JP4790250B2 - Digital single-lens reflex camera - Google Patents

Description

  The present invention relates to a digital single lens reflex camera.

  The finder optical system of a general single-lens reflex camera is an image of an inverted subject that is inverted left and right by being reflected upward by a main mirror, such as a quick return mirror, provided in the middle of the optical path of the photographic optical system. The basic configuration is to provide a next imaging plane and invert the image into an erect image through a prism or mirror for conversion. At the time of shooting, the quick return mirror is retracted out of the shooting optical path, and the light flux of the subject image is guided to the imaging surface for shooting.

For example, Patent Documents 1 to 4 have been proposed as techniques based on such a conventional finder optical system of a single-lens reflex camera.
Japanese Patent Laid-Open No. 01-185622 Japanese Patent Laid-Open No. 10-197914 JP 2003-307764 A Japanese Patent Laid-Open No. 2001-8066

  In Patent Document 1, an image formed in a Porro prism that is transmitted through a quick return mirror provided in the middle of an optical path of a photographing optical system and is arranged behind the quick return mirror is reflected by the quick return mirror. Techniques have been proposed for forming an image that is optically equivalent to an inverted subject image that is imaged on the imaging surface.

  Further, Patent Document 2 discloses that an erect image formed by reversing an image by a Porro prism after the light is reflected upward by a quick return mirror provided in the middle of the optical path of the photographing optical system, There has been proposed a technique for forming an image formed through transmission through a mirror and an equivalent image.

  Further, in Patent Document 3, light is reflected upward by a quick return mirror in the middle of the optical path of the photographing optical system, reflected by a pellicle mirror, and then reflected by a roof prism or roof mirror, whereby an observed image is There has been proposed a technique for forming an image of an image forming plane on which light passes through a quick return mirror and forms an image, and an equivalent image.

  Patent Document 4 discloses a subject obtained by reflecting light upward by a first beam splitter provided in the middle of an optical path of a photographing optical system and reflected by another beam splitter provided further through an eyepiece. As the image, a technique for forming an image equivalent to an image in which light is transmitted through a beam splitter and an equivalent image has been proposed.

  On the other hand, when a finder optical system such as a single-lens reflex camera described in Patent Documents 1 to 3 or a digital single-lens reflex camera described in Patent Document 4 is a basic configuration, an image inverted by a prism or the like is an erect image. Therefore, the image is reflected once toward the subject side to make an erect image. For this reason, when a mirror or the like is disposed on the front surface of the prism or the like, there is a problem that a protrusion is formed in front of the camera body, and the shape easily comes into contact with other photographing equipment.

  In addition, when an optical system such as an AE (Automatic Exposure) or other image forming optical system is arranged, it is necessary to secure a space for the arrangement, but the finder optical system of a conventional single-lens reflex camera has a basic configuration. As long as this is done, there is a problem that it is difficult to secure a space for arranging other optical systems while maintaining the size of the camera body.

  In addition, digital single-lens reflex cameras using large CCDs such as 4/3 inch, APS size, and 35 mm full size, which are the mainstream in digital single-lens reflex cameras, are a common function in compact digital cameras. The through-image function (the function of observing the subject with an electronic viewfinder such as an LCD) is not installed. Therefore, only the optical viewfinder determines the composition at the time of photographing, and there is a problem that photographing cannot be performed while displaying the subject to be photographed by the display element on the back.

  Therefore, the present invention has been made in view of the above-described problems of conventional methods. Its purpose is a digital single-lens reflex camera that is advantageous for any measurement, observation, display, etc. without parallax, and it can be taken with a digital single-lens reflex camera that can easily reduce the thinning or protrusion of the camera, or through images. Another object of the present invention is to provide either or both of digital single-lens reflex cameras capable of determining the composition of photographing while observing a subject to be photographed.

  In order to achieve the above object, a digital single-lens reflex camera according to a first aspect of the present invention includes an image sensor that converts an image of a subject formed on an imaging surface into an electrical signal, and a position substantially equivalent to the imaging surface. A digital single-lens reflex camera having an observation optical system for observing an intermediate image of the object to be formed, and when a light beam perpendicularly incident toward the center of the image sensor is used as an incident optical axis, The observation optical system is disposed on the incident optical axis of the image pickup device, and includes a first reflecting surface that folds the incident optical axis in the horizontal direction of the camera, and an optical axis that is folded by the first reflecting surface. A second reflecting surface disposed in a direction in which the optical axis incident surface intersects with respect to an optical axis incident surface which is a surface including the optical axis that is reflected on the first reflecting surface and the folded optical axis; Placed on the optical axis folded back by the surface Then, the third optical axis is folded back in the direction opposite to the traveling direction of the light incident on the second reflective surface and parallel to the optical axis folded back on the first reflective surface. The reflective surface and the optical axis that is folded back at the third reflective surface, and the optical axis that is folded back at the third reflective surface is in the same direction as the traveling direction of the light incident on the first reflective surface, An eyepiece lens system including an image inverting optical system including a fourth reflecting surface that is folded back in parallel with the optical axis incident on the first reflecting surface and disposed on the optical axis that is folded back at the fourth reflecting surface. And an optical path dividing surface on the optical path from the first reflecting surface to the fourth reflecting surface in the image inverting optical system, and disposed on one of the optical paths divided by the optical path dividing surface. It has an imaging optical system and a light receiving element or a light emitting element.

  The second digital single-lens reflex camera of the present invention is the first digital single-lens reflex camera according to the first digital single-lens reflex camera, wherein the optical path dividing surface is the second reflecting surface, the third reflecting surface, or the fourth reflecting surface. The image forming optical system and the light receiving element or the light emitting element are provided on any one of the surfaces and on the optical axis on the transmission side of the optical path dividing surface.

  According to a third digital single-lens reflex camera of the present invention, in the first digital single-lens reflex camera, the imaging surface has a rectangular shape that is long in the horizontal direction, and the optical axis is folded back by the first reflective surface. Is parallel to the long side direction of the imaging surface.

According to a fourth digital single-lens reflex camera of the present invention, in the first digital single-lens reflex camera, the intermediate image plane is formed between the first reflective surface and the second reflective surface. And the following conditional expression is satisfied.
18.0 mm <Y <26.0 mm (1)
1.0 <H / V <1.4 (2)
Where Y is the diagonal length of the intermediate image plane, H is the length of the intermediate image plane in the long side direction, and V is the length of the intermediate image plane in the short side direction.

  According to a fifth digital single-lens reflex camera of the present invention, in the first digital single-lens reflex camera, a screen surface is provided between the first reflective surface and the second reflective surface. .

  According to a sixth digital single-lens reflex camera of the present invention, in the first digital single-lens reflex camera, the first reflecting surface is retracted in the long side direction of the imaging surface with the short side direction as an axis. It is a quick return mirror that rotates in a straight line.

  According to a seventh digital single-lens reflex camera of the present invention, in the first digital single-lens reflex camera, the observation optical system has the optical path dividing surface as the second reflective surface, The intermediate image is formed between the reflective surface and the second reflective surface, and has a positive refractive power between the first reflective surface and the second reflective surface, and the second reflective surface. It is comprised so that it may have a negative refractive power between a surface and the said 3rd reflective surface.

An eighth digital single-lens reflex camera according to the present invention is characterized in that, in the seventh digital single-lens reflex camera, the following conditional expression is satisfied.
0.5 <f1 / fe <1.4 (3)
−3.3 <f2 / Y <−2.3 (4)
However, f1 is a focal length of an optical system constituted by an optical member arranged between the first reflecting surface and the second reflecting surface, and fe is constituted by an optical member arranged after the intermediate image of the observation optical system. The focal length of the optical system, f2 is the focal length of the optical system composed of an optical member disposed between the second reflecting surface and the third reflecting surface, and Y is the diagonal length of the intermediate image plane. Each element value of the conditional expression is a value when the diopter of the observation optical system becomes −1 diopter when the diopter of the observation optical system continuously changes in conjunction with the movement of the optical member constituting the digital single lens reflex camera.

  According to a ninth digital single-lens reflex camera of the present invention, the seventh or eighth digital single-lens reflex camera has a positive refractive power between the first reflecting surface and the second reflecting surface. And a negative lens for arranging a negative refractive power between the second reflecting surface and the third reflecting surface. To do.

  According to a tenth digital single-lens reflex camera of the present invention, in the ninth digital single-lens reflex camera, the field lens has a Fresnel lens surface having a positive refractive power and a screen surface. And

  The eleventh digital single-lens reflex camera of the present invention is the first digital single-lens reflex camera according to the first digital single-lens reflex camera, wherein the observation optical system is configured such that the optical path dividing surface is the second reflecting surface. The second reflecting surface is configured to form the intermediate image between the reflecting surface and the second reflecting surface, and has a positive refractive power between the first reflecting surface and the second reflecting surface. And the third reflecting surface have a negative refractive power and the second reflecting surface and the imaging optical system have a positive refractive power. .

  According to a twelfth digital single-lens reflex camera of the present invention, in the first digital single-lens reflex camera, the observation optical system has the optical path dividing surface as the second reflecting surface, and the first optical single-lens reflex camera in the first digital single-lens reflex camera. The second reflecting surface is configured to form the intermediate image between the reflecting surface and the second reflecting surface, and has a positive refractive power between the first reflecting surface and the second reflecting surface. And the third reflecting surface have a refractive power of zero, and have a positive refractive power between the second reflecting surface and the imaging optical system. .

  The thirteenth digital single-lens reflex camera according to the present invention has a positive refractive power between the second reflecting surface and the imaging optical system in the eleventh or twelfth digital single-lens reflex camera. It is characterized by arranging a positive lens for the purpose.

  Further, the fourteenth digital single-lens reflex camera of the present invention is the first digital single-lens reflex camera according to the first digital single-lens reflex camera, wherein the imaging optical system and the light receiving element are provided on the optical axis on the transmission side of the optical path dividing plane. The light receiving element is configured by a second imaging element that converts the image of the subject into an electrical signal, and the electrical signal of the image of the subject formed by the second imaging element is converted to convert the image of the subject. A display element for displaying an image is arranged on the back surface of the camera.

  According to a fifteenth digital single-lens reflex camera of the present invention, in the first digital single-lens reflex camera, the imaging optical system includes a reflecting prism.

  According to a sixteenth digital single-lens reflex camera of the present invention, in the first digital single-lens reflex camera, the imaging optical system includes a plurality of reflecting prisms.

  According to a seventeenth digital single-lens reflex camera of the present invention, in the first digital single-lens reflex camera, the imaging optical system includes a plurality of reflecting prisms having a lens function.

  According to an eighteenth digital single lens reflex camera of the present invention, in the first digital single lens reflex camera, the observation optical system has the optical path splitting surface as the second reflecting surface, and the first optical single lens reflex camera. The second reflecting surface is configured to form the intermediate image between the reflecting surface and the second reflecting surface, and has a positive refractive power between the first reflecting surface and the second reflecting surface. An optical element having a refractive power of zero between the first reflective surface and the third reflective surface and having a refractive power disposed on the transmission side of the second reflective surface is a single lens as the imaging optical system. It is characterized by comprising.

  According to a nineteenth digital single-lens reflex camera of the present invention, an image sensor that converts an image of a subject formed on an imaging surface into an electrical signal, and the subject formed at a position substantially equivalent to the imaging surface. A digital single-lens reflex camera having an observation optical system for observing an intermediate image, and when the light beam perpendicularly incident toward the center of the image sensor is an incident optical axis, the observation optical system is A first reflecting surface that is disposed on the incident optical axis of the imaging device and that folds the incident optical axis in the horizontal direction of the camera, and an optical axis that is folded back by the first reflecting surface. A second reflecting surface arranged in a direction where the optical axis incident surface intersects with respect to an optical axis incident surface which is a surface including the incident optical axis and the folded optical axis, and an optical axis folded by the second reflecting surface The second reflecting surface is disposed on the second reflecting surface A third reflecting surface that folds the folded optical axis in a direction opposite to the traveling direction of the light beam incident on the second reflecting surface and parallel to the optical axis folded by the first reflecting surface; An optical axis that is disposed on an optical axis that is folded back by the surface and that is folded by the third reflecting surface is oriented in the same direction as the traveling direction of the light incident on the first reflecting surface and toward the first reflecting surface. And an image reversal optical system comprising a fourth reflecting surface that is folded back in parallel with the incident optical axis, and the imaging surface is a rectangle that is long in the horizontal direction, and the optical axis that is folded back by the first reflecting surface is: It is parallel to the long side direction of the imaging surface.

According to a twentieth digital single-lens reflex camera of the present invention, in the nineteenth digital single-lens reflex camera, the intermediate image plane is formed between the first reflective surface and the second reflective surface. And the following conditional expression is satisfied.
18.0 mm <Y <26.0 mm (5)
1.0 <H / V <1.4 (6)
Where Y is the diagonal length of the intermediate image plane, H is the length of the intermediate image plane in the long side direction, and V is the length of the intermediate image plane in the short side direction.

  In the twenty-first digital single-lens reflex camera according to the present invention, in the nineteenth digital single-lens reflex camera, the first reflecting surface is retracted in the long side direction of the imaging surface with the short side direction as an axis. It is a quick return mirror that rotates in a straight line.

According to a twenty-second digital single-lens reflex camera of the present invention, an imaging element that converts an image of a subject formed on an imaging surface into an electrical signal, and the subject formed at a position substantially equivalent to the imaging surface. A digital single-lens reflex camera having an observation optical system for observing an intermediate image, and when the light beam perpendicularly incident toward the center of the image sensor is an incident optical axis, the observation optical system is A first reflecting surface that is disposed on the incident optical axis of the imaging device and that folds the incident optical axis in the horizontal direction of the camera, and an optical axis that is folded back by the first reflecting surface. A second reflecting surface arranged in a direction where the optical axis incident surface intersects with respect to an optical axis incident surface which is a surface including the incident optical axis and the folded optical axis, and an optical axis folded by the second reflecting surface The second reflecting surface is disposed on the second reflecting surface A third reflecting surface that folds the folded optical axis in a direction opposite to the traveling direction of the light beam incident on the second reflecting surface and parallel to the optical axis folded by the first reflecting surface; An optical axis that is disposed on an optical axis that is folded back by the surface and that is folded by the third reflecting surface is oriented in the same direction as the traveling direction of the light incident on the first reflecting surface and toward the first reflecting surface. And an image inverting optical system including a fourth reflecting surface that is folded back in parallel with the incident optical axis, the optical path dividing surface is the second reflecting surface, and the first reflecting surface and the second reflecting surface The intermediate image is formed between the first reflecting surface and the second reflecting surface, and has a positive refractive power between the second reflecting surface and the third reflecting surface. It is characterized by having negative refractive power between them.

The twenty-third digital single-lens reflex camera of the present invention is characterized in that, in the twenty-second digital single-lens reflex camera, the following conditional expression is satisfied.
0.5 <f1 / fe <1.4 (7)
−3.3 <f2 / Y <−2.3 (8)
However, f1 is a focal length of an optical system constituted by an optical member arranged between the first reflecting surface and the second reflecting surface, and fe is constituted by an optical member arranged after the intermediate image of the observation optical system. The focal length of the optical system, f2 is the focal length of the optical system composed of an optical member disposed between the second reflecting surface and the third reflecting surface, and Y is the diagonal length of the intermediate image plane. Each element value of the conditional expression is a value when the diopter of the observation optical system becomes −1 diopter when the diopter of the observation optical system continuously changes in conjunction with the movement of the optical member constituting the digital single lens reflex camera.

  According to a twenty-fourth digital single-lens reflex camera of the present invention, in the twenty-second or twenty-third digital single-lens reflex camera, a positive refractive power is provided between the first reflecting surface and the second reflecting surface. A field lens having a positive refracting power is arranged, and a negative lens is arranged to have a negative refracting power between the second reflecting surface and the third reflecting surface. Features.

  According to a 25th digital single-lens reflex camera of the present invention, in the 24th digital single-lens reflex camera, the field lens has a Fresnel lens surface having a positive refractive power and a screen surface. And

  The digital single-lens reflex camera of the present invention may be configured to satisfy any one of the configurations of the digital single-lens reflex camera at the same time.

  The digital single-lens reflex camera according to the present invention is a digital single-lens reflex camera that is advantageous for any measurement, observation, display, etc. without parallax, and is easy to suppress thinning or protrusion of the camera, Alternatively, it is possible to provide either or both of a digital single-lens reflex camera that can determine the composition of photographing while observing a subject to be photographed with a through image.

Prior to the description of the embodiment of the present invention, the function and effect of the present invention will be described.
The digital single-lens reflex camera to which the present invention is applied is such that an image pickup element is picked up by light passing through the photographing lens by attaching a photographing lens integral with or removable from the digital single-lens reflex camera to the digital single-lens reflex camera. An image formed on the surface is converted into an electric signal and processed (for example, image processing, storage, etc.).

  Here, like the first digital single-lens reflex camera of the present invention, the light incident from the photographing lens is reflected by the first reflecting surface, the second reflecting surface, the third reflecting surface, and the fourth reflecting surface by the observation optical system. By doing so, an intermediate image of the subject can be observed as an erect image as in the case where the subject image passes through the optical path of a so-called poro prism or polo mirror.

  Here, as in the first digital single-lens reflex camera of the present invention, the observation optical path formed by the first reflecting surface, the second reflecting surface, the third reflecting surface, and the fourth reflecting surface is defined with respect to the incident optical axis. If it is laid out so that it bends in a substantially vertical plane, an optical layout with little influence on the thickness direction of the camera can be obtained.

  Further, like the first digital single-lens reflex camera of the present invention, the position of the fourth reflecting surface on the reflection optical axis of the third reflecting surface is moved, and the eyepiece lens system 1 is folded back by the fourth reflecting surface. By moving the position of the reflected optical axis leading to the position, the position of the exit window of the finder can be changed, and an optical layout arranged at an easy-to-use position can be achieved. In the case of such an optical layout, it is easy to secure a space for providing an optical path dividing surface, an imaging optical system, a light receiving element, or a light emitting element.

  For example, in the first digital single lens reflex camera of the present invention, if the light receiving element is configured by an image sensor such as a CCD or C-MOS, image information from the image sensor is displayed on a display element such as a liquid crystal display element (LCD). An electronic viewfinder that can communicate and display electrically can be provided.

  In the first digital single-lens reflex camera of the present invention, the imaging optical system and the light receiving element may be configured to detect the brightness of the subject, detect the in-focus state of the subject, and the like. Moreover, it is good also as a structure which receives the light from an observer's eyeball and detects an observer's eyes | visual_axis.

  In the first digital single-lens reflex camera according to the present invention, when the light-emitting element is used instead of the light-receiving element, the object position at which the subject is in focus is projected by projecting to the in-focus position. Can do.

  As in the second digital single-lens reflex camera of the present invention, if any one of the second reflecting surface, the third reflecting surface, and the fourth reflecting surface is an optical path dividing surface, it is formed on the back surface of the optical path dividing surface. An optical system such as an imaging optical system can be disposed in the optical path, and the space behind the optical path dividing surface can be effectively used. In addition, the observation optical path formed by the first reflection surface, the second reflection surface, the third reflection surface, and the fourth reflection surface is laid out so as to be bent at a plane substantially perpendicular to the incident optical axis, and the optical path is divided. Since the optical path formed on the back surface of the surface is also a surface that is substantially perpendicular to the incident optical axis, the influence on the thickness direction of the camera can be reduced even if an optical system such as an imaging optical system is arranged. .

  As in the third digital single-lens reflex camera of the present invention, the imaging surface has a rectangular shape that is long in the horizontal direction, and the optical axis turned back by the first reflecting surface is parallel to the long side direction of the imaging surface. If so, an increase in the height direction of the camera can be suppressed.

  In addition, since the camera body generally has a structure that is long in the lateral direction, the optical axis folded back on the first reflecting surface is the long side direction of the imaging surface, as in the third digital single-lens reflex camera of the present invention. If it is made parallel, when the second reflecting surface is an optical path dividing surface, the place where the optical system such as the imaging optical system is arranged is in the horizontal direction of the camera body, so it is advantageous to secure a space. Become.

  In the first digital single-lens reflex camera of the present invention, since the distance between the first reflecting surface and the intermediate image surface is substantially equal to the distance between the first reflecting surface and the image sensor, the position of the intermediate image surface and the first image surface If the distance from the reflecting surface is shortened, the distance between the first reflecting surface and the image sensor can be relatively shortened.

  Therefore, if the intermediate image plane is formed between the first reflecting surface and the second reflecting surface as in the fourth digital single lens reflex camera of the present invention, the position of the intermediate image plane is the first. Compared to the case where there are two or more reflecting surfaces, the distance between the first reflecting surface and the image sensor can be reduced, which is advantageous for reducing the thickness direction of the camera.

  Further, as in the fourth digital single lens reflex camera of the present invention, the long side direction of the intermediate image plane formed between the first reflecting surface and the second reflecting surface corresponds to the long side direction of the imaging surface. Since this also corresponds to the thickness direction of the camera, the thickness direction of the camera can be reduced by reducing the length of the intermediate image plane in the long side direction.

Further, as in the fourth digital single-lens reflex camera of the present invention, if the size of the intermediate image plane is too small, it becomes difficult to increase the observation field of view, so that the following conditional expressions (9) and (10) are satisfied. preferable.
18.0 mm <Y <26.0 mm (9)
1.0 <H / V <1.4 (10)
Where Y is the diagonal length of the intermediate image plane, H is the length of the intermediate image plane in the long side direction, and V is the length of the intermediate image plane in the short side direction.

Conditional expression (9) defines the diagonal length Y of the intermediate image plane, and defines a range smaller than the intermediate image size used in the conventional digital single-lens reflex camera.
When the diagonal length Y of the intermediate image plane is below the lower limit of the conditional expression (9), the observation field of view becomes small.
On the other hand, if the diagonal length Y of the intermediate image plane exceeds the upper limit of the conditional expression (9), it is disadvantageous for miniaturization of the camera.
In the digital single-lens reflex camera of the present invention, it is preferable to set the lower limit of conditional expression (9) to 19.0. Furthermore, the lower limit is more preferably 20.0.
In the digital single-lens reflex camera of the present invention, it is preferable to set the upper limit of conditional expression (9) to 24.0. Furthermore, the upper limit is more preferably 22.0.

Conditional expression (10) defines the ratio between the length H of the intermediate image plane in the long side direction and the length V of the intermediate image plane in the short side direction.
If the length H in the long side direction of the intermediate image plane / the length V in the short side direction of the intermediate image plane is less than the lower limit of the conditional expression (10), the photograph at the normal position becomes square or vertically long. .
On the other hand, if the length H in the long side direction of the intermediate image plane / the length V in the short side direction of the intermediate image plane exceeds the upper limit of the conditional expression (10), the difference between the short side and the long side increases. Since the field of view in the short side direction is smaller than the field of view in the long side direction, observation becomes difficult.
In the digital single-lens reflex camera of the present invention, it is preferable to set the lower limit of conditional expression (10) to 1.25. Furthermore, the lower limit is more preferably 1.30.
In the digital single-lens reflex camera of the present invention, it is preferable to set the upper limit of conditional expression (10) to 1.35.

If the length H in the long side direction of the intermediate image surface / the length V in the short side direction of the intermediate image surface is within the range of the conditional expression (10), the first reflecting surface is the length of the first reflecting surface. Even if the side of the side or the short side is used as an axis to retract from the incident optical axis, the influence on the thickness direction of the camera is not so great.
In addition, even if the first reflecting surface is configured so that the incident optical axis is folded back in parallel with the long side direction of the imaging surface, the space for retreating from the incident optical axis about the short side of the first reflecting surface is in the thickness direction of the camera. Can be secured.

  As in the fifth digital single-lens reflex camera of the present invention, a screen surface (for example, ground glass, minute prism array, etc.) is arranged at the position of the intermediate image formed between the first reflecting surface and the second reflecting surface. Then, since the image position formed by the photographing lens is equal to the intermediate image position formed between the first reflecting surface and the second reflecting surface, the subject image on the screen surface is confirmed by checking the subject image. Easy focus adjustment.

  As in the sixth digital single-lens reflex camera of the present invention, when the incident optical axis is folded back in parallel with the long side direction of the imaging surface by the quick return mirror, the short side direction is used as an axis in the long side direction of the imaging surface. It is composed of a quick return mirror that rotates to retract.

  Like the seventh digital single-lens reflex camera of the present invention, it is configured to form an intermediate image between the first reflecting surface and the second reflecting surface, and the first reflecting surface and the second reflecting surface; If the optical power is positive, the off-axis light beam on the image plane is inclined toward the optical axis, and the subsequent optical system can be easily miniaturized.

  Further, as in the seventh digital single-lens reflex camera of the present invention, if the positive refractive power is increased between the first reflecting surface and the second reflecting surface, the distance from the intermediate image surface to the imaging optical system. The imaging optical system 7 can be arranged even when the space behind the second reflecting surface is small.

  Further, as in the seventh digital single-lens reflex camera of the present invention, if the positive refracting power is increased between the first reflecting surface and the second reflecting surface, the light beam of the entire subject image is reliably transmitted to the light receiving element. Can lead to the screen periphery. As a result, when the digital single-lens reflex camera is provided with a through image function, it is possible to ensure the field of view of the entire subject image in the imaging optical system and the light receiving element.

  Further, as in the seventh digital single-lens reflex camera of the present invention, if the negative refractive power is provided between the second reflecting surface and the third reflecting surface, the convergence of the off-axis light beam can be reduced. Can be diverged or diverged, and even if the positive refractive power between the first reflecting surface and the second reflecting surface is too strong, a space and an eye point for arranging the reflecting surface for image reversal are secured. can do.

It is preferable that the following conditional expressions (11) and (12) are satisfied as in the eighth digital single-lens reflex camera of the present invention.
0.5 <f1 / fe <1.4 (11)
−3.3 <f2 / Y <−2.3 (12)
However, f1 is a focal length of an optical system constituted by an optical member arranged between the first reflecting surface and the second reflecting surface, and fe is constituted by an optical member arranged after the intermediate image of the observation optical system. The focal length of the optical system, f2 is the focal length of the optical system composed of an optical member disposed between the second reflecting surface and the third reflecting surface, and Y is the diagonal length of the intermediate image plane. Each element value of the conditional expression is -1.0 diopter when the diopter (m ^-1 ) of the observation optical system continuously changes in conjunction with the movement of the optical member constituting the digital single lens reflex camera. Value.

  Conditional expression (11) is obtained from the focal length f1 of the optical system constituted by the optical member arranged between the first reflecting surface and the second reflecting surface, and the optical member arranged after the intermediate image of the observation optical system. The ratio with the focal length fe of the optical system to be configured is defined.

Focal length of an optical system constituted by an optical member arranged between the first reflecting surface and the second reflecting surface f1 / focal length of an optical system constituted by an optical member arranged after the intermediate image of the observation optical system If fe falls below the lower limit of conditional expression (11), the positive refractive power as a field lens is too strong, and it becomes difficult to secure the eye point of the observation optical system.
On the other hand, the focal length f1 of the optical system constituted by the optical member arranged between the first reflecting surface and the second reflecting surface f1 / of the optical system constituted by the optical member arranged after the intermediate image of the observation optical system If the focal length fe exceeds the upper limit of the conditional expression (11), the positive refractive power as a field lens is too weak, the image forming optical system tends to be large, and layout becomes difficult.
In the digital single-lens reflex camera of the present invention, it is preferable to set the lower limit of conditional expression (11) to 0.6. Furthermore, the lower limit is more preferably 0.7.
In the digital single-lens reflex camera of the present invention, it is preferable to set the upper limit of conditional expression (11) to 1.0. Further, the upper limit value is more preferably 0.8.

  Conditional expression (12) defines the ratio between the focal length f2 of the optical system composed of the optical member disposed between the second reflecting surface and the third reflecting surface and the diagonal length Y of the intermediate image surface. Is.

When the focal length f2 / diagonal length Y of the intermediate image plane 3 of the optical system configured by the optical member disposed between the second reflecting surface and the third reflecting surface is below the lower limit of the conditional expression (12), Since the negative refractive power between the second reflecting surface and the third reflecting surface becomes weak, it becomes difficult to ensure the optical path length of the observation optical system, and the arrangement of the reflecting surfaces is restricted.
On the other hand, the focal length f2 / diagonal length Y of the intermediate image plane 3 of the optical system constituted by the optical member disposed between the second reflecting surface M2 and the third reflecting surface M3 is the upper limit of the conditional expression (12). Since the negative power increases, the focal length of the eyepiece lens system becomes short, and it becomes difficult to ensure the magnification of the finder.
In the digital single-lens reflex camera of the present invention, it is preferable to set the lower limit of conditional expression (12) to −3.1. Furthermore, the lower limit value is more preferably −2.9.
In the digital single-lens reflex camera of the present invention, it is preferable that the upper limit value of conditional expression (12) is −2.5. Furthermore, the upper limit is more preferably −2.7.

  As in the ninth digital single-lens reflex camera of the present invention, a field lens having a positive refractive power is disposed between the first reflecting surface and the second reflecting surface so as to have a positive refractive power. If a negative lens is provided between the second reflecting surface and the third reflecting surface so as to have a negative refracting power, the necessary refracting power between the reflecting surfaces can be ensured.

  If the field lens has a Fresnel lens surface having a positive refractive power and a screen surface as in the tenth digital single-lens reflex camera of the present invention, the number of elements can be reduced.

  As in the eleventh digital single-lens reflex camera of the present invention, if it is configured to have a positive refractive power between the second reflecting surface and the imaging optical system, the first reflecting surface, the second reflecting surface, Between the second reflecting surface and the third reflecting surface can be made relatively weak, and the negative refracting power arranged to weaken the positive refracting power relatively between the second reflecting surface and the third reflecting surface can also be made weak. .

  In addition, as in the eleventh digital single-lens reflex camera of the present invention, if it is configured to have a positive refractive power between the second reflecting surface and the imaging optical system, the lens constituting the observation optical system The degree of freedom in design increases, the aberration generated between the second reflecting surface and the third reflecting surface can be reduced, and the observation of the observation optical system can be improved.

  Further, like the eleventh digital single-lens reflex camera of the present invention, each has a positive refractive power between the first reflecting surface and the second reflecting surface and between the second reflecting surface and the imaging optical system. If comprised in this way, a part of role as a field lens of positive refractive power can be shared between a 2nd reflective surface and an imaging optical system, and refractive power can be shared.

  Further, if the positive refractive power is disposed near the back surface of the second reflecting surface at a position close to the intermediate image surface, the field lens function can be maximized and the optical performance can be improved.

  In addition, when a digital single-lens reflex camera is provided with a through image function or the like, if it is configured to have a strong positive refractive power between the second reflecting surface and the imaging optical system, Even when the positive refracting power between the second reflecting surface and the second reflecting surface is weak, it is possible to easily obtain a configuration in which the light beam of the entire subject image is reliably guided to the periphery of the screen of the light receiving element through the imaging optical system.

  As in the twelfth digital single-lens reflex camera of the present invention, if it is configured to have a positive refractive power between the second reflecting surface and the imaging optical system, the first reflecting surface, the second reflecting surface, The positive refracting power can be weakened, and the optical path between the second reflecting surface and the light receiving element can be shortened.

  Further, by reducing the positive refractive power between the first reflecting surface and the second reflecting surface, the observation optical path can be obtained even when the refractive power is zero between the second reflecting surface and the third reflecting surface of the observation optical system. Can be secured, and the configuration of the observation optical system can be simplified.

  As in the thirteenth digital single-lens reflex camera of the present invention, if a positive lens for providing a positive refractive power is disposed between the second reflecting surface and the imaging optical system, the first reflecting surface The function of the field lens arranged between the second reflecting surface and the second reflecting surface can be shared.

  As in the fourteenth digital single-lens reflex camera of the present invention, it has an imaging optical system and a light receiving element on the optical axis on the transmission side of the optical path dividing surface, and the light receiving element converts the subject image into an electrical signal. If a display element configured to display the subject image by converting an electric signal of the subject image formed by the second image sensor and displaying the subject image is formed in the photographed image. On the other hand, an electronic image having no parallax can be observed.

  Further, as in the fourteenth digital single-lens reflex camera of the present invention, an electronic image having no parallax with respect to a photographed image can be observed by a display element provided on the back of the camera. Unlike a camera, it is not necessary to determine the composition at the time of shooting while checking the subject image with the optical viewfinder, so that restrictions on the shooting angle and shooting posture can be reduced. In other words, the fourteenth digital single-lens reflex camera of the present invention is displayed on the image sensor for observation regardless of the presence or absence of the image sensor (for example, a through image function) having both functions for photographing and observation. With this electronic image, the composition can be determined and photographed while observing the subject image.

  As in the fifteenth digital single-lens reflex camera of the present invention, the camera can be reduced in size if the optical axis transmitted through the half mirror is bent by the imaging optical system.

  As in the sixteenth digital single-lens reflex camera of the present invention, the camera can be miniaturized by adopting a configuration in which the optical axis transmitted through the half mirror is bent a plurality of times by the imaging optical system.

  As in the seventeenth digital single-lens reflex camera of the present invention, the camera can be miniaturized by adopting a configuration in which the optical axis transmitted through the half mirror is bent a plurality of times by the imaging optical system.

  Further, if the prism itself constituting the imaging optical system has a refractive power, the number of optical members constituting the imaging optical system can be reduced.

  As in the 18th digital single lens reflex camera of the present invention, an optical element is omitted between the second reflecting surface and the third reflecting surface, and an optical device having a refractive power arranged on the transmission side of the second reflecting surface. If the element is composed of only a single lens as the imaging optical system, the number of optical members constituting the imaging optical system can be reduced, and the configuration of the imaging optical system can be simplified.

  According to a nineteenth digital single-lens reflex camera of the present invention, an image pickup surface of an image pickup device is formed by a light beam that passes through the photographic lens by attaching a photographic lens integral with or removable from the digital single-lens reflex camera to the digital single-lens reflex camera. The image formed above is converted into an electrical signal and processed (for example, image processing, storage, etc.).

  Here, as in the nineteenth digital single-lens reflex camera of the present invention, the light incident from the photographing lens is reflected by the first reflecting surface, the second reflecting surface, the third reflecting surface, and the fourth reflecting surface by the observation optical system. By doing so, an intermediate image of the subject can be observed as an erect image as in the case where the subject image passes through the optical path of a so-called poro prism or polo mirror.

  Here, as in the nineteenth digital single-lens reflex camera of the present invention, the observation optical path formed by the first reflecting surface, the second reflecting surface, the third reflecting surface, and the fourth reflecting surface is defined with respect to the incident optical axis. If it is laid out so that it bends in a substantially vertical plane, an optical layout with little influence on the thickness direction of the camera can be obtained.

  Further, as in the nineteenth digital single-lens reflex camera of the present invention, the position of the fourth reflection surface on the reflection optical axis of the third reflection surface is moved and folded back on the fourth reflection surface to form an eyepiece system. If the position of the reflected optical axis to be guided is moved, the position of the exit window of the finder can be changed, and an optical layout arranged at an easy-to-use position can be achieved.

  As in the nineteenth digital single-lens reflex camera of the present invention, the imaging surface has a rectangular shape that is long in the horizontal direction, and the optical axis that is turned back at the first reflecting surface is parallel to the long-side direction of the imaging surface. If so, the increase in the height direction of the camera can be suppressed.

  In the nineteenth digital single-lens reflex camera of the present invention, the distance between the first reflecting surface and the intermediate image surface is substantially equal to the distance between the first reflecting surface and the image sensor, so If the distance from the reflecting surface is shortened, the distance between the first reflecting surface and the image sensor can be relatively shortened.

  Therefore, if the intermediate image plane is formed between the first reflecting surface and the second reflecting surface as in the twentieth digital single-lens reflex camera of the present invention, the position of the intermediate image plane is the first. Compared to the case where there are two or more reflecting surfaces, the distance between the first reflecting surface and the image sensor can be reduced, which is advantageous for reducing the thickness direction of the camera.

  Further, as in the twentieth digital single lens reflex camera of the present invention, the long side direction of the intermediate image plane formed between the first reflecting surface and the second reflecting surface corresponds to the long side direction of the imaging surface. Since this also corresponds to the thickness direction of the camera, the thickness direction of the camera can be reduced by reducing the length of the intermediate image plane in the long side direction.

Further, as in the twentieth digital single-lens reflex camera of the present invention, if the size of the intermediate image plane is too small, it becomes difficult to increase the observation field of view, so it is preferable to satisfy the following conditional expressions (13) and (14). .
18.0 mm <Y <26.0 mm (13)
1.0 <H / V <1.4 (14)
Where Y is the diagonal length of the intermediate image plane, H is the length of the intermediate image plane in the long side direction, and V is the length of the intermediate image plane in the short side direction.

Conditional expression (13) defines the diagonal length Y of the intermediate image plane, and defines a range smaller than the intermediate image size used in the conventional digital single-lens reflex camera.
When the diagonal length Y of the intermediate image plane is less than the lower limit of conditional expression (13), the observation field of view becomes small.
On the other hand, if the diagonal length Y of the intermediate image plane exceeds the upper limit of the conditional expression (13), it is disadvantageous for downsizing of the camera.
In the digital single-lens reflex camera of the present invention, it is preferable to set the lower limit of conditional expression (13) to 19.0. Furthermore, the lower limit is more preferably 20.0.
In the digital single-lens reflex camera of the present invention, it is preferable to set the upper limit of conditional expression (13) to 24.0. Furthermore, the upper limit is more preferably 22.0.

Conditional expression (14) defines the ratio between the length H of the intermediate image plane in the long side direction and the length V of the intermediate image plane in the short side direction.
If the length H in the long side direction of the intermediate image plane / the length V in the short side direction of the intermediate image plane is less than the lower limit of the conditional expression (14), the photograph at the normal position becomes square or vertically long. .
On the other hand, when the length H in the long side direction of the intermediate image plane / the length V in the short side direction of the intermediate image plane exceeds the upper limit of the conditional expression (14), the difference between the short side and the long side increases. Since the field of view in the short side direction is smaller than the field of view in the long side direction, observation becomes difficult.
In the digital single-lens reflex camera of the present invention, it is preferable to set the lower limit of conditional expression (14) to 1.25. Furthermore, the lower limit is more preferably 1.30.
In the digital single-lens reflex camera of the present invention, it is preferable to set the upper limit of conditional expression (14) to 1.35.

If the length H in the long side direction of the intermediate image surface / the length V in the short side direction of the intermediate image surface is within the range of the conditional expression (14), the first reflecting surface is the length of the first reflecting surface. Even if the side of the side or the short side is used as an axis to retract from the incident optical axis, the influence on the thickness direction of the camera is not so great.
In addition, even if the first reflecting surface is configured so that the incident optical axis is folded back in parallel with the long side direction of the imaging surface, the space for retreating from the incident optical axis about the short side of the first reflecting surface is in the thickness direction of the camera. Can be secured.

  As in the twenty-first digital single-lens reflex camera of the present invention, when the incident optical axis is folded back in parallel with the long-side direction of the imaging surface with a quick return mirror, the short-side direction is used as an axis in the long-side direction of the imaging surface. It is composed of a quick return mirror that rotates to retract.

  According to a twenty-second digital single-lens reflex camera of the present invention, an image pickup surface of an image pickup device is formed by a light beam that passes through the photographic lens by attaching a photographic lens integral with or removable from the digital single-lens reflex camera to the digital single-lens reflex camera. The image formed above is converted into an electrical signal and processed (for example, image processing, storage, etc.).

  Here, like the twenty-second digital single-lens reflex camera of the present invention, the light incident from the photographing lens is reflected by the first reflecting surface, the second reflecting surface, the third reflecting surface, and the fourth reflecting surface by the observation optical system. By doing so, an intermediate image of the subject can be observed as an erect image as in the case where the subject image passes through the optical path of a so-called poro prism or polo mirror.

  Here, as in the twenty-second digital single-lens reflex camera of the present invention, the observation optical path formed by the first reflecting surface, the second reflecting surface, the third reflecting surface, and the fourth reflecting surface is defined with respect to the incident optical axis. If it is laid out so that it bends in a substantially vertical plane, an optical layout with little influence on the thickness direction of the camera can be obtained.

  Further, as in the twenty-second digital single-lens reflex camera of the present invention, the position of the fourth reflecting surface on the reflection optical axis of the third reflecting surface is moved and folded back by the fourth reflecting surface to form an eyepiece lens system. If the position of the reflected optical axis to be guided is moved, the position of the exit window of the finder can be changed, and an optical layout arranged at an easy-to-use position can be achieved.

  Like the 22nd digital single-lens reflex camera of this invention, it is comprised so that an intermediate image may be formed between a 1st reflective surface and a 2nd reflective surface, and a 1st reflective surface and a 2nd reflective surface, If the optical power is positive, the off-axis light beam on the image plane is inclined toward the optical axis, and the subsequent optical system can be easily miniaturized.

  Further, as in the twenty-second digital single-lens reflex camera of the present invention, if the negative refracting power is provided between the second reflecting surface and the third reflecting surface, the convergence of the off-axis light beam can be reduced. Can be diverged or diverged, and even if the positive refractive power between the first reflecting surface and the second reflecting surface is too strong, a space and an eye point for arranging the reflecting surface for image reversal are secured. can do.

As in the twenty-third digital single-lens reflex camera of the present invention, it is preferable that the following conditional expressions (15) and (16) are satisfied.
0.5 <f1 / fe <1.4 (15)
−3.3 <f2 / Y <−2.3 (16)
However, f1 is a focal length of an optical system constituted by an optical member arranged between the first reflecting surface and the second reflecting surface, and fe is constituted by an optical member arranged after the intermediate image of the observation optical system. The focal length of the optical system, f2 is the focal length of the optical system composed of an optical member disposed between the second reflecting surface and the third reflecting surface, and Y is the diagonal length of the intermediate image plane. Each element value of the conditional expression is -1.0 diopter when the diopter (m ^-1 ) of the observation optical system continuously changes in conjunction with the movement of the optical member constituting the digital single lens reflex camera. Value.

  Conditional expression (15) is obtained from the focal length f1 of the optical system constituted by the optical member arranged between the first reflecting surface and the second reflecting surface, and the optical member arranged after the intermediate image of the observation optical system. The ratio with the focal length fe of the optical system to be configured is defined.

Focal length of an optical system constituted by an optical member arranged between the first reflecting surface and the second reflecting surface f1 / focal length of an optical system constituted by an optical member arranged after the intermediate image of the observation optical system When fe falls below the lower limit of conditional expression (15), the positive refractive power as a field lens is too strong, and it becomes difficult to secure the eye point of the observation optical system.
On the other hand, the focal length f1 of the optical system constituted by the optical member arranged between the first reflecting surface and the second reflecting surface f1 / of the optical system constituted by the optical member arranged after the intermediate image of the observation optical system If the focal length fe exceeds the upper limit of the conditional expression (15), the positive refractive power as a field lens is too weak, the imaging optical system 7 tends to be large, and layout becomes difficult.
In the digital single-lens reflex camera of the present invention, it is preferable to set the lower limit of conditional expression (15) to 0.6. Furthermore, the lower limit is more preferably 0.7.
In the digital single-lens reflex camera of the present invention, it is preferable to set the upper limit of conditional expression (15) to 1.0. Further, the upper limit value is more preferably 0.8.

  Conditional expression (16) defines the ratio between the focal length f2 of the optical system composed of the optical member disposed between the second reflecting surface and the third reflecting surface and the diagonal length Y of the intermediate image surface. Is.

When the focal length f2 / diagonal length Y of the intermediate image plane of the optical system configured by the optical member disposed between the second reflecting surface and the third reflecting surface is less than the lower limit of the conditional expression (16), Since the negative refractive power between the second reflecting surface and the third reflecting surface becomes weak, it becomes difficult to secure the optical path length of the observation optical system, and the arrangement of the reflecting surfaces is restricted.
On the other hand, if the focal length f2 / diagonal length Y of the intermediate image plane of the optical system configured by the optical member disposed between the second reflecting surface and the third reflecting surface exceeds the upper limit of the conditional expression (16). Since the negative power becomes stronger, the focal length of the eyepiece lens system becomes shorter, and it becomes difficult to ensure the magnification of the finder.
In the digital single-lens reflex camera of the present invention, it is preferable to set the lower limit of conditional expression (16) to −3.1. Furthermore, the lower limit value is more preferably −2.9.
In the digital single-lens reflex camera of the present invention, it is preferable that the upper limit value of conditional expression (16) is −2.5. Furthermore, the upper limit is more preferably −2.7.

  As in the 24th digital single lens reflex camera of the present invention, a field lens having a positive refractive power is disposed between the first reflecting surface and the second reflecting surface so as to have a positive refractive power. If a negative lens is provided between the second reflecting surface and the third reflecting surface so as to have a negative refracting power, the necessary refracting power between the reflecting surfaces can be ensured.

  If the field lens has a Fresnel lens surface having positive refractive power and a screen surface as in the 25th digital single lens reflex camera of the present invention, the number of elements can be reduced and the camera can be made thin. Can be

  Moreover, the digital single-lens reflex camera of this invention is good also as a structure which satisfies at least one of the structures which said digital single-lens reflex camera has simultaneously.

Embodiments of the present invention will be described below with reference to the drawings.
7A and 7B are explanatory views of the basic configuration of a digital single-lens reflex camera having an observation optical system according to the present invention as viewed from the object side, where FIG. 7A is a perspective view and FIG. 7B is a front view.

  As shown in FIG. 7, the digital single-lens reflex camera of the present invention includes an image sensor 13 and an observation optical system.

  The observation optical system includes an image inverting optical system, an optical path dividing surface, an imaging optical system 7, and an eyepiece lens system 1, and observes an intermediate image of a subject formed at a position substantially equivalent to the imaging surface.

  The image inverting optical system includes a first reflecting surface M1, a second reflecting surface M2, a third reflecting surface M3, and a fourth reflecting surface M4 in order from the object side.

  The first reflecting surface M1 is disposed on the incident optical axis 14 of the image sensor 13 at the time of photographing, and is disposed so that the incident optical axis 14 is folded back in parallel with the long side direction of the imaging surface. A quick return mirror M1 that rotates so as to retract in the long side direction of the imaging surface is used.

  The second reflecting surface M2 is composed of a half mirror M2 and functions as an optical path dividing surface. Further, the second reflecting surface M2 is on the optical axis 15a folded back by the first reflecting surface M1 with respect to the optical axis incident surface (surface including the incident optical axis and the folded optical axis) on the first reflecting surface M1. Are arranged in a direction intersecting with the optical axis incident surface.

  The third reflecting surface M3 is opposite to the traveling direction of the light beam incident on the second reflecting surface M2 with the optical axis 15b folded back on the second reflecting surface M2 on the optical axis 15b folded back on the second reflecting surface M2. Thus, they are arranged so as to be folded back in parallel with the optical axis 15a folded back at the first reflecting surface M1.

  The fourth reflecting surface M4 has an optical axis 15c folded back on the third reflecting surface M3 on the optical axis 15c folded back on the third reflecting surface M3 in the same direction as the traveling direction of the light beam incident on the first reflecting surface M1. Therefore, it is arranged so as to be folded back in parallel with the optical axis 14 incident on the first reflecting surface M1.

  The optical path splitting surface is configured by any one of the second reflecting surface M2, the third reflecting surface M3, and the fourth reflecting surface M4, and the first reflecting surface M1 to the fourth reflecting surface M4 in the image inverting optical system. It is arranged on the optical path. In the case of FIG. 7, for convenience, the second reflecting surface M2 is an optical path dividing surface.

  The imaging optical system 7 is disposed on the optical axis 15e on the transmission side of the optical path dividing surface among the optical paths divided by the optical path dividing surface.

  The eyepiece lens system 1 is disposed on the optical axis 15d that is folded back by the fourth reflecting surface M4.

  According to the digital single-lens reflex camera having the basic configuration in which the optical members constituting the observation optical system of the present invention are arranged, the light beam of the subject image that has passed through the photographing lens is the first reflecting surface that is in the middle of the optical path in the observation optical system. Reflected in parallel with the long side direction of the imaging surface via M1. The light beam reflected through the first reflecting surface M1 forms an image at the position of the intermediate image surface 3 and enters the half mirror M2. Then, the light beam reflected through the half mirror M2 enters the third reflecting surface M3. The light beam reflected through the third reflecting surface M3 is opposite to the traveling direction of the light beam incident on the half mirror M2, and is parallel to the optical axis 15a turned back at the first reflecting surface M1, The light enters the fourth reflecting surface M4. The light beam reflected through the fourth reflection surface M4 is in the same direction as the traveling direction of the light beam incident on the first reflection surface M1, and is parallel to the incident optical axis 14 on the first reflection surface M1. , Enters the eyepiece lens system 1. Then, it is guided to the viewfinder through the eyepiece lens system 1 and observed as an erect image.

  On the other hand, the light beam transmitted through the optical path dividing surface is guided to the light receiving element 11 through the imaging optical system 7 disposed on the optical axis 15e on the transmission side of the optical path dividing surface.

  Then, the electrical signal of the subject image formed on the light receiving element 11 is transferred to a display element provided on the back surface of the camera, and an electronic image of the subject image is displayed on the display screen. As a result, the photographer can photograph the subject image while viewing the photographed image displayed on the liquid crystal disposed on the back of the camera, separately from the viewfinder.

  At the time of shooting, the quick return mirror M1 rotates so as to retract in the long side direction of the imaging surface with the short side as an axis. Then, the light beam of the subject image that has passed through the photographic lens is guided to the image sensor 13 and is imaged.

First Embodiment FIG. 1 is an explanatory view of a layout of a digital single lens reflex camera according to a first embodiment of the present invention as viewed from the object side.

  FIG. 2 does not show the first reflecting surface M1, the second reflecting surface M2, the third reflecting surface M3, and the fourth reflecting surface M4 in the observation optical system of the digital single lens reflex camera according to the first embodiment of the present invention. It is sectional drawing in alignment with the optical axis which shows the optical structure from the screen surface 4b developed to the exit pupil.

  As shown in FIG. 1, the digital single-lens reflex camera of the first embodiment of the present invention has the basic configuration of the observation optical system of the digital single-lens reflex camera of the present invention shown in FIG. A field lens having a positive refracting power for having a power is disposed between the first reflecting surface M1 and the half mirror M2, and a concave surface is provided on the object side for having a negative refracting power. This is a configuration in which a negative meniscus lens 6 having negative refractive power is disposed between the half mirror M2 and the third reflecting surface M3.

  In the case of the digital single-lens reflex camera according to the first embodiment of the present invention, the imaging optical system 7 is composed of two prisms 9a and 9b having free-form surfaces. Therefore, the imaging optical system 7 can realize good imaging performance without using a large number of lenses even when the space behind the half mirror M2 is limited. Further, since the two prisms 9a and 9b are composed of a prism having a reflecting surface, the imaging optical system 7 can be made compact by bending the optical axis.

  In the case of the digital single-lens reflex camera according to the first embodiment of the present invention, a field lens having a positive refractive power for providing a positive refractive power is provided between the first reflecting surface M1 and the half mirror M2. Is arranged. The field lens is composed of a Fresnel lens 4 having a positive refractive power composed of a Fresnel lens surface 4a having positive refractive power on the pupil side and a screen surface 4b on the object side. As the Fresnel lens surface 4a, a Fresnel lens surface having positive refractive power on the pupil side may be used as an optical action surface such as a refractive surface having positive refractive power with a convex surface facing the pupil side. The screen surface 4 b is composed of a screen mat 5 and is located on the intermediate image surface 3. The screen surface 4b may be configured to project using, for example, ground glass, a minute prism array, a hologram screen, or the like.

  In the case of the digital single-lens reflex camera according to the first embodiment of the present invention, the negative lens 6 having a negative meniscus negative refractive power with the concave surface facing the object side to have negative refractive power is provided. , Between the half mirror M2 and the third reflecting surface M3. The negative lens 6 is preferably disposed immediately behind the half mirror M2 in order to reduce the action of the field lens.

Next, numerical data of optical members constituting the digital single-lens reflex camera of the first embodiment of the present invention are shown below.
In the numerical data, r ₁ , r ₂ ... Are curvature radii (mm) of the surfaces of the optical members, d ₁ , d _2. ), N _d1 , n _d2 ... Is the refractive index of each optical member at the wavelength of d-line (587.6 nm), and ν _d1 , ν _d2 ... Are Abbe's at the wavelength of d-line of each optical member (587.6 nm). Represents a number.
Further, the aspherical shape to be rotated with respect to the optical axis is such that the optical axis direction is z, the direction orthogonal to the optical axis is y, the direction orthogonal to z and y is x, the cone coefficient is k, the optical axis When the aspherical coefficients to be rotated are A ₄ , A ₆ , and A ₈ , they are defined by the following equations.
z = (y ² / r) / [1+ [1− (1 + k) (y / r) ² ] ^1/2 ] + A ₄ y ⁴ +
A ₆ y ⁶ + A ₈ y ⁸
Further, f1 is a focal length of the Fresnel lens 4 disposed between the first reflecting surface M1 and the second reflecting surface M2, and f2 is a negative lens 6 disposed between the second reflecting surface M2 and the third reflecting surface M3. Is the focal point of the optical system composed of the Fresnel lens 4, the second reflecting surface M2, the negative lens 6, the third reflecting surface M3, and the fourth reflecting surface M4 disposed after the intermediate image of the observation optical system. The distance, Y is the diagonal length of the intermediate image plane 3, V is the length of the intermediate image plane 3 in the short side direction, and H is the length of the intermediate image plane 3 in the long side direction.
These symbols are also common in numerical data 2 of Example 4 described later.

  The positions of the first reflecting surface M1 to the fourth reflecting surface M4 are not described as numerical values, but are respectively planar reflecting surfaces. In addition, the first reflecting surface M1 is disposed closer to the subject than the first surface of the numerical data 1. Further, the second reflecting surface M2 is disposed between the second surface of the numerical data 1 and the third surface of the numerical data 1 which is 4.8700 mm. In addition, the third reflecting surface M3 and the fourth reflecting surface M4 are disposed between the fourth surface of the numerical data 1 and the fifth surface of the numerical data 1 at a distance of 9.7900 mm. Further, the position of the reflecting surface is arranged by appropriately adjusting the observation optical path.

The first surface and the second surface of the numerical data 1 are both “INF” (∞). The first surface of the numerical data 1 is the screen surface 4b and is disposed at the position of the intermediate image surface 3 that is equivalent to the imaging surface.
The second surface of the numerical data 1 is constituted by a Fresnel lens surface 4a having a positive refractive power.

Diopter adjustment is performed by moving the lens of the eyepiece system 1. When the diopter (m ^-1 ) of numerical data 1 is adjusted to +1.0 diopter, D1 is 2.860602 mm and D2 is 2.73554 mm. When the diopter (m ^-1 ) is adjusted to -1.0 diopter, D1 is 3.26619 mm and D2 is 2.39347 mm. When the diopter (m ^-1 ) is adjusted to -3.0 diopters, D1 is 3.71391 mm and D2 is 1.94744 mm.

Further, both the ninth surface and the eleventh surface are aspheric surfaces. The conical coefficient K on the ninth surface is zero. The fourth-order aspheric coefficient A ₄ is 1.9502 × 10 ⁻⁶ , the sixth-order aspheric coefficient A ₆ is −2.0711 × 10 ⁻⁸ , and the eighth-order aspheric coefficient A ₈ is 1.0096 × 10 ⁻¹⁰ .
Further, the conical coefficient K on the eleventh surface is zero. The fourth-order aspheric coefficient A ₄ is 1.1485 × 10 ⁻⁴ , the sixth-order aspheric coefficient A ₆ is −5.8005 × 10 ⁻⁷ , and the eighth-order aspheric coefficient A ₈ is 1.5471 × 10 ⁻⁹ .

The focal length f1 of the Fresnel lens 4 is configured to be 35 mm. The focal length f2 of the negative lens 6 is configured to be −58.0 mm. Further, the focal length fe of the optical system composed of the Fresnel lens 4, the second reflecting surface M2, the negative lens 6, the third reflecting surface M3, and the fourth reflecting surface M4 arranged after the intermediate image is 48.0 mm. It is configured as follows. Further, when the length H in the short side direction of the intermediate image plane 3 is 12.3 mm and the length V in the long side direction of the intermediate image plane 3 is 16.4 mm, the diagonal length Y of the intermediate image plane 3 is It is configured to be 20.5 mm.
In addition, the optical system includes the Fresnel lens 4, the second reflecting surface, the negative lens 6, the third reflecting surface M3, and the fourth reflecting surface M4, which are disposed after the primary imaging surface of the focal length f1 of the Fresnel lens 4. The ratio of the system to the focal length fe is configured to be 0.73.
Further, the ratio of the focal length f2 of the negative lens 6 to the diagonal length Y of the intermediate image plane 3 is set to −2.83. Further, the ratio of the length V in the long side direction of the intermediate image surface 3 to the length H in the short side direction of the intermediate image surface 3 is 1.33.

Numerical data 1
r ₁ = INF (screen surface) d ₁ = 1.5000 n _d1 = 1.51633 ν _d1 = 64.14
r ₂ = INF (Fresnel lens surface) d ₂ = 24.8700
r ₃ = −19.9875 d ₃ = 1.5163 n _d3 = 1.51633 ν _d3 = 64.14
r ₄ = −61.6237 d ₄ = 46.7900
r ₅ = 54.9375 d ₅ = 7.8000 n _d5 = 1.51633 ν _d5 = 64.14
r ₆ = −56.2405 d ₆ = 0.2118
r ₇ = 28.1467 d ₇ = 5.4932 n _d7 = 1.51633 ν _d7 = 64.14
r ₈ = 296.1988 d ₈ = D1 (variable)
r ₉ = 14.121 (aspherical surface) d ₉ = 6.2572 n _d9 = 1.52542 ν _d9 = 55.78
r ₁₀ = 36.1049 d ₁₀ = D2 (variable)
r ₁₁ = −31.4023 (aspherical surface) d ₁₁ = 1.8000 n _d11 = 1.58423 ν _d11 = 30.49
r ₁₂ = 8.8451 d ₁₂ = 21.9300
r ₁₃ = INF (exit pupil)

Diopter (m ^-1 ) = +1.0 -1.0 -3.0
D1 2.88602 3.26619 3.71391
D2 2.77354 2.39347 1.94744

Aspheric coefficient surface number k A ₄ A ₆ A ₈
9 0 1.9502 × 10 ^-6 −2.0711 × 10 ^-8 1.0096 × 10 ^-10
11 0 1.1485 × 10 ^-4 −5.8005 × 10 ^-7 1.5471 × 10 ^-9

f1 = 35.0mm
f2 = -58.0mm
fe = 48.0mm
Y = 20.5mm (V = 12.3mm, H = 16.4mm)
f1 / fe = 0.73
f2 / Y = -2.83
H / V = 1.33

Second Embodiment FIG. 3 is an explanatory view of the layout of a digital single lens reflex camera according to a second embodiment of the present invention as viewed from the object side.

  As shown in FIG. 3, the digital single lens reflex camera in the second embodiment has the basic configuration of the observation optical system of the digital single lens reflex camera of the present invention shown in FIG. A field lens having a positive refracting power is arranged between the first reflecting surface M1 and the half mirror M2, and a positive lens 12 whose both surfaces are convex is arranged with the half mirror M2 and the imaging optical system 7. It is the structure arrange | positioned between.

  In the case of the digital single-lens reflex camera according to the second embodiment of the present invention, the negative lens 6 is not disposed between the half mirror M2 and the third reflecting surface M3. It will be tailored to. When it is difficult to form an image on the light receiving element 11 with only the two prisms 9a and 9b by disposing the positive lens 12 having both convex surfaces between the half mirror M2 and the imaging optical system 7. However, the power of the field lens is supplemented and an image is formed on the light receiving element 11. Further, the positive lens 12 has a good position close to the intermediate image plane 3 so as to maximize the effect as a field lens, and is disposed immediately behind the half mirror M2.

Third Embodiment FIG. 4 is an explanatory diagram showing the layout of a digital single lens reflex camera according to a third embodiment of the present invention as viewed from the object side.

  As shown in FIG. 4, the digital single-lens reflex camera in the third embodiment has the basic configuration of the observation optical system of the digital single-lens reflex camera of the present invention shown in FIG. In this configuration, a field lens having positive refracting power is arranged between the first reflecting surface M1 and the half mirror M2.

  In the case of the digital single-lens reflex camera of the third embodiment of the present invention, the imaging optical system 7 includes a photometric optical system composed of a positive single lens 16 having a convex surface on the light receiving side.

  In the case of the digital single-lens reflex camera according to the third embodiment of the present invention, the image on the intermediate image plane 3 formed on the screen surface 4b is formed to the outermost periphery of the image on the intermediate image plane 3 in the photometric optical system. There is no need to Therefore, the refractive power between the half mirror M2 and the photometric optical system is sufficient by the power of the field lens matched to the observation optical system.

Fourth Embodiment FIG. 5 is an explanatory view of the layout of a digital single-lens reflex camera according to a fourth embodiment of the present invention as viewed from the object side.

  FIG. 6 does not show the first reflecting surface M1, the second reflecting surface M2, the third reflecting surface M3, and the fourth reflecting surface M4 in the observation optical system of the digital single lens reflex camera according to the fourth embodiment of the present invention. It is sectional drawing which follows the optical axis which shows the optical structure from the screen surface 4b developed to the exit pupil.

  As shown in FIG. 5, the digital single lens reflex camera in the fourth embodiment has the basic configuration of the observation optical system of the digital single lens reflex camera of the present invention shown in FIG. A field lens having positive refracting power for having a negative refracting power is disposed between the first reflecting surface M1 and the half mirror M2, and a concave surface is directed to the object side for having negative refracting power. The meniscus negative lens 6 having negative refractive power is arranged between the half mirror M2 and the third reflecting surface M3.

  Next, numerical data of optical members constituting the digital single-lens reflex camera of the fourth embodiment of the present invention are shown below.

  The first surface of the numerical data 2 is the Fresnel lens surface 4a, and the second surface of the numerical data 2 is the screen surface 4b. Further, the first reflecting surface M1 is disposed closer to the subject than the first surface of the numerical data 2. The second reflection surface M2, the third reflection surface M3, and the fourth reflection surface M4 are disposed between the screen surface 4b and the third surface of the numerical data 2.

Diopter adjustment is performed by moving the lens of the eyepiece system 1. When the diopter (m ^-1 ) of numerical data 2 is adjusted to +1.0 diopter, D1 is 0.68989 mm and D2 is 4.91664 mm. When the diopter (m ^-1 ) is adjusted to -1.0 diopter, D1 is 1.47951 mm and D2 is 4.12931 mm. In addition, when adjusting diopter (m ^-1 ) to -3.0 diopters, D1 is 2.41983mm and D2 is 3.18669mm

  Further, the focal length f1 of the Fresnel lens 4 is configured to be 70 mm. The focal length fe of the optical system composed of the Fresnel lens 4, the second reflecting surface M2, the negative lens 6, the third reflecting surface M3, and the fourth reflecting surface M4 disposed after the intermediate image surface 3 is 50.0 mm. It is comprised so that. Further, when the length H in the short side direction of the intermediate image surface 3 is 12.3 mm and the length V in the long side direction of the intermediate image surface 3 is 16.4 mm, the diagonal length Y of the intermediate image surface 3 is 20.5 mm. It is configured as follows. The ratio of the focal length f1 of the Fresnel lens 4 to the focal length f2 of the negative lens 6 is 1.40. Further, the ratio of the focal length f2 of the negative lens 6 to the diagonal length Y of the intermediate image plane 3 is set to −2.83. Further, the ratio of the length V in the long side direction of the intermediate image surface 3 to the length H in the short side direction of the intermediate image surface 3 is 1.33.

  Further, the screen surface 4b and the Fresnel lens surface 4a may be reversely arranged with the first surface as the Fresnel lens surface 4a and the second surface as the screen surface 4b.

Numerical data 2
r ₁ = INF (Fresnel lens surface) d ₁ = 1.5000 n _d1 = 1.51633 ν _d1 = 64.14
r ₂ = INF (screen surface) d ₂ = 73.2400
r ₃ = 36.1201 d ₃ = 7.4725 n _d3 = 1.51633 ν _d3 = 64.14
r ₄ = -55.8429 d ₄ = D1 (variable)
r ₅ = 16.1794 d ₅ = 4.2709 n _d5 = 1.77250 ν _d5 = 49.60
r ₆ = 29.1531 d ₆ = D2 (variable)
r ₇ -468.5107 d ₇ = 1.8000 n _d7 = 1.59270 ν _d7 = 35.31
r ₈ = 11.5579 d ₈ = 3.1100
r ₉ = INF (exit pupil)

Diopter (m ^-1 ) = +1.0 -1.0 -3.0
D1 0.68989 1.47951 2.41983
D2 4.91664 4.12931 3.18669

f1 = 70.0mm
f2 =-
fe = 50.0mm
Y = 20.5mm (V = 12.3mm, H = 16.4mm)
f1 / fe = 1.40

  The retraction direction of the quick return mirror M1 may be either the horizontal direction or the vertical direction of the incident optical axis 14.

  In each of the embodiments, if the light receiving element 11 is replaced with a light emitting element, display within the field of view can be performed on the screen surface 4b. For example, if red light is projected onto the in-focus area on the screen surface 4b, the in-focus area can be easily confirmed.

  If the optical path is divided at the back of the imaging optical system 7, both the light receiving element 11 and the light emitting element can be arranged, and the functions of both can be obtained separately or simultaneously.

  As described above, the digital single-lens reflex camera according to the present invention has the following features in addition to the invention described in the claims.

(1) An optical path dividing member is arranged in the middle of the optical path of a single-lens reflex finder using a polo-type mirror or prism as an optical member constituting the image inverting optical system, and an imaging optical system 7 is arranged on the divided optical path side. A digital single-lens reflex camera characterized by

(2) The digital single-lens reflex camera according to (1) above, wherein a negative lens 6 for reducing the effect of a field lens is arranged in the middle of the optical path of the finder closer to the pupil than the eyepiece lens system 1

(3) The digital single-lens reflex camera according to (1) above, wherein the imaging optical system 7 disposed on the divided optical path side includes two prisms 9a and 9b.

(4) The observation optical system mounted on the digital single-lens reflex camera described in (1) above is characterized in that the intermediate image plane 3 is disposed in the lateral position of the camera and satisfies the following conditional expression: Digital single-lens reflex camera.
18.0 <Y <26.0
1.0 <H / V <1.4
Where Y is the diagonal length of the intermediate image plane 3, H is the length of the intermediate image plane 3 in the long side direction, and V is the length of the intermediate image plane 3 in the short side direction.

It is explanatory drawing which looked at the layout of the digital single-lens reflex camera concerning 1st Example of this invention from the object side. A screen developed by omitting the description of the first reflecting surface M1, the second reflecting surface M2, the third reflecting surface M3, and the fourth reflecting surface M4 in the observation optical system of the digital single lens reflex camera of the first embodiment of the invention. It is sectional drawing which follows the optical axis which shows the optical structure from the surface 4b to an exit pupil. It is explanatory drawing which looked at the layout of the digital single-lens reflex camera concerning 2nd Example of this invention from the object side. It is explanatory drawing which looked at the layout of the digital single-lens reflex camera concerning 3rd Example of this invention from the object side. It is explanatory drawing which looked at the layout of the digital single-lens reflex camera concerning 4th Example of this invention from the object side. The first reflective surface M1, the second reflective surface M2, the third reflective surface M3, and the fourth reflective surface M4 in the observation optical system of the digital single-lens reflex camera according to the fourth embodiment of the present invention are omitted and developed. FIG. 3 is a cross-sectional view along the optical axis showing the optical configuration from the Fresnel lens surface 4a to the exit pupil. It is explanatory drawing which looked at the basic composition of the digital single-lens reflex camera which has an observation optical system of the present invention from the object side, (a) is a perspective view and (b) is a front view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Eyepiece lens system 2 Mount 3 Intermediate image surface 4 Fresnel lens 4a Fresnel lens surface 4b Screen surface 5 Screen mat 6 Negative lens 7 Imaging optical system 8 Cover glass 9a, 9b Prism 10 Aperture 11 Light receiving element 12 Positive lens 13 Imaging element 14 Incident optical axes 15, 15a, 15b, 15c, 15d, 15e Observation optical system optical axis 16 Single lens M1 First reflecting surface (quick return mirror)
M2 Second reflective surface (half mirror)
M3 Third reflective surface M4 Fourth reflective surface

Claims (21)

A digital single-lens camera comprising: an imaging element that converts an image of a subject formed on an imaging surface into an electrical signal; and an observation optical system for observing the intermediate image of the subject that is formed at a position substantially equivalent to the imaging surface A reflex camera,
When the light incident perpendicularly toward the center of the image sensor is the incident optical axis,
The observation optical system is
A first reflecting surface that is disposed on the incident optical axis of the imaging device and folds the incident optical axis in the horizontal direction of the camera;
The optical axis incident surface intersects with the optical axis incident surface which is a surface including the incident optical axis and the folded optical axis on the first reflective surface on the optical axis folded on the first reflective surface. A second reflecting surface,
The optical axis that is disposed on the optical axis that is folded back at the second reflective surface, the optical axis that is folded back at the second reflective surface is opposite to the traveling direction of the light incident on the second reflective surface, and the A third reflecting surface that is folded back in parallel with the optical axis that is folded at the first reflecting surface;
The optical axis is disposed on the optical axis that is folded at the third reflecting surface, and the optical axis that is folded at the third reflecting surface is in the same direction as the traveling direction of the light incident on the first reflecting surface, and the first A fourth reflecting surface that folds in parallel with the optical axis incident on the reflecting surface;
An image reversal optical system consisting of
An eyepiece lens system disposed on the optical axis that is folded back on the fourth reflecting surface;
An optical path dividing surface on the optical path from the first reflecting surface to the fourth reflecting surface in the image reversal optical system;
An imaging optical system and a light receiving element or a light emitting element arranged on one of the optical paths divided by the optical path dividing surface,
I have a,
A quick return mirror that rotates so that the first reflecting surface is retracted in the long side direction of the imaging surface with the short side direction as an axis;
An optical system between the first reflecting surface and the second reflecting surface, and an optical system having a negative refractive power between the second reflecting surface and the third reflecting surface;
Configured to form the intermediate image between the first reflective surface and the second reflective surface;
A digital single-lens reflex camera that satisfies the following conditional expression .
0.5 <f1 / fe <1.4
−3.3 <f2 / Y <−2.3
However, f1 is a focal length of an optical system constituted by an optical member arranged between the first reflecting surface and the second reflecting surface, and fe is constituted by an optical member arranged after the intermediate image of the observation optical system. The focal length of the optical system, f2 is the focal length of the optical system composed of an optical member disposed between the second reflecting surface and the third reflecting surface, and Y is the diagonal length of the intermediate image plane.
Each element value of the conditional expression is −1.0 diopter when the diopter (m ⁻¹ ) of the observation optical system continuously changes in conjunction with the movement of the optical member constituting the digital single-lens reflex camera. The value at the time. The optical path dividing surface is constituted by any one of the second reflecting surface, the third reflecting surface, and the fourth reflecting surface,
2. The digital single-lens reflex camera according to claim 1, wherein the imaging optical system and the light receiving element or the light emitting element are provided on an optical axis on a transmission side of the optical path dividing surface.   The digital single-lens camera according to claim 1, wherein the imaging surface has a rectangular shape that is long in a horizontal direction, and an optical axis that is turned back at the first reflecting surface is parallel to a long-side direction of the imaging surface. Reflex camera. Digital single-lens reflex camera according to claim 1, characterized in that it satisfies the following Symbol condition.
18.0mm <Y <26.0mm
1.0 <H / V <1.4
Where Y is the diagonal length of the intermediate image plane, H is the length of the intermediate image plane in the long side direction, and V is the length of the intermediate image plane in the short side direction.   The digital single-lens reflex camera according to claim 1, further comprising a screen surface between the first reflecting surface and the second reflecting surface. The observation optical system is configured such that the optical path dividing surface is the second reflecting surface, and has a positive refractive power between the first reflecting surface and the second reflecting surface. The digital single-lens reflex camera according to claim 1, wherein Arranging a field lens having a positive refractive power so as to have a positive refractive power between the first reflecting surface and the second reflecting surface;
The digital single-lens reflex camera according to claim 6 , wherein a negative lens is disposed between the second reflecting surface and the third reflecting surface so as to have a negative refractive power . The digital single-lens reflex camera according to claim 7, wherein the field lens has a Fresnel lens surface having a positive refractive power and a screen surface . In the observation optical system, the optical path dividing surface is the second reflecting surface,
Moreover, while having a positive refractive power between the first reflecting surface and the second reflecting surface,
The digital single-lens reflex camera according to claim 1 , wherein the digital single-lens reflex camera is configured to have a positive refractive power between the second reflecting surface and the imaging optical system . In the observation optical system, the optical path dividing surface is the second reflecting surface,
Further, it has a positive refractive power between the first reflecting surface and the second reflecting surface,
The refractive power is zero between the second reflecting surface and the third reflecting surface,
The digital single-lens reflex camera according to claim 1 , wherein the digital single-lens reflex camera is configured to have a positive refractive power between the second reflecting surface and the imaging optical system . 11. The digital single-lens reflex camera according to claim 9 , wherein a positive lens is disposed between the second reflecting surface and the imaging optical system so as to have a positive refractive power . The imaging optical system and the light receiving element are provided on an optical axis on the transmission side of the optical path dividing surface, and the light receiving element includes a second imaging element that converts the image of the subject into an electrical signal,
The display element for converting the electrical signal of the image of the subject formed by the second image sensor to display the image of the subject is disposed on the back of the camera. The digital single-lens reflex camera of 1. The digital single-lens reflex camera according to claim 1 , wherein the imaging optical system includes a reflecting prism . The digital single-lens reflex camera according to claim 1, wherein the imaging optical system includes a plurality of reflecting prisms . The digital single-lens reflex camera according to claim 1, wherein the imaging optical system includes a plurality of reflecting prisms having a lens function . In the observation optical system, the optical path dividing surface is the second reflecting surface,
Further, it has a positive refractive power between the first reflecting surface and the second reflecting surface,
The refractive power is zero between the second reflecting surface and the third reflecting surface,
2. The digital single-lens reflex camera according to claim 1 , wherein an optical element having a refractive power disposed on the transmission side of the second reflecting surface is configured by only a single lens as the imaging optical system. . A digital single-lens camera comprising: an imaging element that converts an image of a subject formed on an imaging surface into an electrical signal; and an observation optical system for observing the intermediate image of the subject that is formed at a position substantially equivalent to the imaging surface A reflex camera,
When the light incident perpendicularly toward the center of the image sensor is the incident optical axis,
The observation optical system is
A first reflecting surface that is disposed on the incident optical axis of the imaging device and folds the incident optical axis in the horizontal direction of the camera;
The optical axis incident surface intersects with the optical axis incident surface which is a surface including the incident optical axis and the folded optical axis on the first reflective surface on the optical axis folded on the first reflective surface. A second reflecting surface,
The optical axis that is disposed on the optical axis that is folded back at the second reflective surface, the optical axis that is folded back at the second reflective surface is opposite to the traveling direction of the light incident on the second reflective surface, and the A third reflecting surface that is folded back in parallel with the optical axis that is folded at the first reflecting surface;
The optical axis is disposed on the optical axis that is folded at the third reflecting surface, and the optical axis that is folded at the third reflecting surface is in the same direction as the traveling direction of the light incident on the first reflecting surface, and the first A fourth reflecting surface that folds in parallel with the optical axis incident on the reflecting surface;
An image reversal optical system consisting of
The imaging surface has a rectangular shape that is long in the horizontal direction, and an optical axis that is turned back at the first reflecting surface is parallel to a long side direction of the imaging surface,
A quick return mirror that rotates so that the first reflecting surface is retracted in the long side direction of the imaging surface with the short side direction as an axis;
An optical system between the first reflecting surface and the second reflecting surface, and an optical system having a negative refractive power between the second reflecting surface and the third reflecting surface;
Configured to form the intermediate image between the first reflective surface and the second reflective surface;
A digital single-lens reflex camera that satisfies the following conditional expression .
0.5 <f1 / fe <1.4
−3.3 <f2 / Y <−2.3
However, f1 is a focal length of an optical system constituted by an optical member arranged between the first reflecting surface and the second reflecting surface, and fe is constituted by an optical member arranged after the intermediate image of the observation optical system. The focal length of the optical system, f2 is the focal length of the optical system composed of an optical member disposed between the second reflecting surface and the third reflecting surface, and Y is the diagonal length of the intermediate image plane.
Each element value of the conditional expression is −1.0 diopter when the diopter (m ⁻¹ ) of the observation optical system continuously changes in conjunction with the movement of the optical member constituting the digital single-lens reflex camera. The value at the time. The digital single-lens reflex camera according to claim 17 , wherein the following conditional expression is satisfied .
18.0mm <Y <26.0mm
1.0 <H / V <1.4
Where Y is the diagonal length of the intermediate image plane, H is the length of the intermediate image plane in the long side direction, and V is the length of the intermediate image plane in the short side direction. A digital single-lens camera comprising: an imaging element that converts an image of a subject formed on an imaging surface into an electrical signal; and an observation optical system for observing the intermediate image of the subject that is formed at a position substantially equivalent to the imaging surface A reflex camera,
When the light incident perpendicularly toward the center of the image sensor is the incident optical axis,
The observation optical system is
A first reflecting surface that is disposed on the incident optical axis of the imaging device and folds the incident optical axis in the horizontal direction of the camera;
The optical axis incident surface intersects with the optical axis incident surface which is a surface including the incident optical axis and the folded optical axis on the first reflective surface on the optical axis folded on the first reflective surface. A second reflecting surface,
The optical axis that is disposed on the optical axis that is folded back at the second reflective surface, the optical axis that is folded back at the second reflective surface is opposite to the traveling direction of the light incident on the second reflective surface, and the A third reflecting surface that is folded back in parallel with the optical axis that is folded at the first reflecting surface;
The optical axis is disposed on the optical axis that is folded at the third reflecting surface, and the optical axis that is folded at the third reflecting surface is in the same direction as the traveling direction of the light incident on the first reflecting surface, and the first A fourth reflecting surface that folds in parallel with the optical axis incident on the reflecting surface;
An image reversal optical system consisting of
The optical path splitting surface is the second reflecting surface;
Further, the intermediate image is formed between the first reflecting surface and the second reflecting surface,
Having a positive refractive power between the first reflecting surface and the second reflecting surface;
It is comprised so that it may have a negative refractive power between the said 2nd reflective surface and the said 3rd reflective surface,
A quick return mirror that rotates so that the first reflecting surface is retracted in the long side direction of the imaging surface with the short side direction as an axis;
A digital single-lens reflex camera that satisfies the following conditional expression .
0.5 <f1 / fe <1.4
−3.3 <f2 / Y <−2.3
However, f1 is a focal length of an optical system constituted by an optical member arranged between the first reflecting surface and the second reflecting surface, and fe is constituted by an optical member arranged after the intermediate image of the observation optical system. The focal length of the optical system, f2 is the focal length of the optical system composed of an optical member disposed between the second reflecting surface and the third reflecting surface, and Y is the diagonal length of the intermediate image plane.
Each element value of the conditional expression is −1.0 diopter when the diopter (m ⁻¹ ) of the observation optical system continuously changes in conjunction with the movement of the optical member constituting the digital single-lens reflex camera. The value at the time. Arranging a field lens having a positive refractive power so as to have a positive refractive power between the first reflecting surface and the second reflecting surface;
Wherein between the second reflecting surface and the third reflecting surface, the digital single-lens reflex camera according to claim 19, characterized in that a negative lens so that a negative refractive power. 21. The digital single-lens reflex camera according to claim 20 , wherein the field lens has a Fresnel lens surface having a positive refractive power and a screen surface .