JP4939003B2 - Peripheral shooting device - Google Patents

Description

The present invention relates to a peripheral photographing apparatus .

  2. Description of the Related Art Conventionally, as a device for photographing a blind spot of a vehicle, a peripheral photographing device for photographing a blind spot on the left and right and front and lower sides of the vehicle has been developed.

The apparatus described in Patent Document 1 is an apparatus that captures a left and right visual field through a prism and directly captures a front lower visual field (hereinafter referred to as “lower visual field”).
This device captures the road surface in front of the vehicle as a lower field of view. However, since the angle of view depends on the performance of the imaging lens of the camera, only a narrow range can be captured.
In order to increase the shooting field angle of the lower field of view, it may be possible to adopt a camera imaging lens with a large field angle. In this case, however, there is a risk of field loss due to total reflection in the right and left field prisms. The horizontal angle of view of the imaging lens is limited to about 60 to 80 degrees.

Therefore, in order to solve such problems, a peripheral photographing device for photographing the lower visual field through a concave lens has been developed.
The devices described in Patent Literature 2 and Patent Literature 3 are devices that photograph the left and right visual fields via a prism and photograph the lower visual field via a concave lens.
JP 2000-89301 A (paragraphs 0016 to 0019, FIGS. 1 to 3) JP 2004-104476 A (paragraphs 0020 to 0056, FIGS. 1 to 5) JP 2004-325498 A (paragraphs 0047 to 0062, FIGS. 16 and 17)

  However, the devices described in Patent Document 2 and Patent Document 3 can enlarge the angle of view of the lower field of view by inserting the concave lens into the lower field of view. There is a problem that an image cannot be obtained.

The present invention was devised to solve the above-described problems, and when photographing a plurality of fields of view with a single camera, the field angle of a desired field of view is enlarged while suppressing the influence on the focus of each field of view. It is an object of the present invention to provide a peripheral photographing device capable of photographing .

To solve the above problems, the invention according to claim 1, camera and each of the plurality of areas on the imaging lens of the camera, the peripheral photographing; and a peripheral photographing optical system for guiding light from different perspectives The peripheral photographing optical system includes a left visual field optical system that guides light from the left visual field to the upper left region on the imaging lens, and a right that guides light from the right visual field to the upper right region on the imaging lens. A field-of-view optical system, and a field-of-view optical system that guides light from the field of view to a lower region on the imaging lens, and the field-of-view optical system has a refractive power of −2 to 0 diopter. , Functioning to enlarge the angle of view in the lower region on the imaging lens, and the upper edge of the lower visual field optical system determines the boundary between the upper left region and the upper right region and the lower region , The left visual field optical system and the right Characterized in that it is arranged between the field optical system and the camera.

The “ lower-view optical system ” in the peripheral photographing optical system is suitable for a field of view for imaging a nearby imaging target, and suppresses the influence on the focus of the imaging lens of the camera, while suppressing each area of the imaging lens of the camera. It functions to expand the angle of view to a desired angle of view.

The invention according to claim 2 is the peripheral photographing apparatus according to claim 1, wherein the left visual field optical system, the right visual field optical system, and the lower visual field optical system are arranged from a corresponding visual field. The light is reflected an even number of times and led to a corresponding region on the imaging lens as an erect image.

Such a peripheral photographing device reflects light from the corresponding visual field, and therefore, the light from the visual field in a desired direction can be guided to the imaging lens by setting the reflecting surface. In addition, since light from the corresponding field of view is reflected an even number of times and guided to the imaging lens as an erect image, processing such as image inversion is unnecessary.

Further, the invention according to claim 3 is the peripheral photographing apparatus according to claim 1 or 2, wherein the lower visual field optical system includes a first surface on which light from the lower visual field is incident. A second surface on which the light incident on the first surface is reflected, a third surface on which the light reflected on the second surface is reflected, and the light reflected on the third surface. The first surface has a planar shape, the second surface functions as a convex mirror for the light, and the third surface is: It functions as a concave mirror for the light, the fourth surface has a planar shape, and is a combined optical system of the first surface, the second surface, the third surface, and the fourth surface It has a refractive power of −2 to 0 diopter.

The invention according to claim 4 is the peripheral photographing apparatus according to claim 1 or 2, wherein the lower visual field optical system includes a first surface on which light from the lower visual field is incident. A second surface on which the light incident on the first surface is reflected, a third surface on which the light reflected on the second surface is reflected, and the light reflected on the third surface. A first surface that functions as a convex lens with respect to the light, and the second surface functions as a convex mirror with respect to the light, The third surface functions as a concave mirror for the light, the fourth surface functions as a concave lens for the light, the first surface, the second surface, the third surface, and The synthetic optical system of the fourth surface has a refractive power of −2 to 0 diopter.

The peripheral visual field optical system for such a peripheral photographing device has a simple configuration and functions to enlarge the angle of view of the imaging lens while suppressing the influence on the focus of the imaging lens of the camera.

According to the present invention, there is provided a peripheral photographing device capable of enlarging and photographing a desired field of view while suppressing an influence on the focus of each visual field when photographing a plurality of visual fields with one camera. Can be provided.

  Hereinafter, with regard to the embodiments of the present invention, the peripheral photographing optical system of the present invention is installed in the front of the vehicle, the left visual field, the right visual field and the lower visual field are photographed with one camera, and each visual field is displayed on the display means installed in the vehicle interior. A case where the present invention is applied to a periphery monitoring system that displays an image will be described as an example with reference to the drawings as appropriate. Similar parts are denoted by the same reference numerals, and redundant description is omitted. The expression of position, direction, etc. is based on the driver who has boarded the vehicle in which such a periphery monitoring system is installed.

(First embodiment)
First, the periphery monitoring system according to the first embodiment of the present invention will be described. FIG. 1 is a schematic perspective view showing a periphery monitoring system using a periphery photographing optical system according to the first embodiment of the present invention. As shown in FIG. 1, the periphery monitoring system 1 is connected to the peripheral photographing device 2 including the peripheral photographing optical system 11 and the camera 21 and the camera 21 and is installed at a position where the driver in the vehicle cabin can visually recognize. Display means 3. The camera 21 photographs a plurality of fields of view through the peripheral photographing optical system 11. And the display means 3 which consists of a display etc. displays the image which the camera 21 image | photographed.

(Peripheral shooting optical system 11)
The peripheral photographing optical system 11 includes a left visual field optical system 12, a right visual field optical system 13, and a lower visual field optical system 14. Here, the left visual field is the left visual field of the vehicle, and the right visual field is the right visual field of the vehicle. Further, the lower visual field is a front and lower visual field of the vehicle, and is a region that becomes a driver's blind spot by the front grill of the vehicle. The imaging lens 22 of the camera 21 is divided into an upper left region 22a, an upper right region 22b, and a lower region 22c (see FIG. 9), and the left visual field optical system 12 uses light from the left visual field for the left visual field. It is arranged so as to pass through the optical system 12 and enter the upper left region 22a of the imaging lens 22 of the camera 21. Since FIG. 9 is a front view of the imaging lens 22, the left and right sides on the paper and the left and right with reference to the driver of the vehicle are reversed. The right visual field optical system 13 is arranged so that light from the right visual field passes through the right visual field optical system 13 and enters the upper right region 22 b of the imaging lens 22. The lower visual field optical system 14 is arranged so that light from the lower visual field passes through the lower visual field optical system 14 and enters the lower region 22 c of the imaging lens 22.

  The “upper left region 22a”, “upper right region 22b”, and “lower region 22c” referred to here are such that the upper side of the imaging lens 22 of the camera 21 is enlarged by the first boundary L21 (divided) as shown in FIG. The upper part of the upper left part, the upper right part and the lower part are finally divided into three parts by equally dividing the upper part into left and right parts by the second boundary L22. That is. These upper left area 22a, upper right area 22b, and lower area 22c cover the entire imaging lens 22.

  Next, details of the peripheral photographing optical system 11 according to the first embodiment will be described in the order of the left visual field optical system 12, the right visual field optical system 13, and the lower visual field optical system 14.

(Left visual field optical system 12 and right visual field optical system 13)
First, the configuration of the left visual field optical system 12 and the right visual field optical system 13 will be described. The left visual field optical system 12 and the right visual field optical system 13 guide light to the region (upper left region 22a and upper right region 22b) of the imaging lens 22 of the camera 21 that exceeds the vertical field angle ratio of 50% within the photographing field angle. Is. Since the left visual field optical system 12 and the right visual field optical system 13 are symmetrical with respect to a vertical plane including the optical axis of the imaging lens 22 of the camera 21, the left visual field optical system 12 will be described below. The explanation will be focused on.

  FIG. 2 is a front view of the peripheral photographing apparatus of FIG. FIG. 3 is a top view of the peripheral photographing apparatus of FIG. As shown in FIG. 3, the left (right) visual field optical system 12 (13) is provided on the first surface 12 a (13 a) that is an incident surface provided on the left (right) side and on the rear side. A second surface 12b (13b) which is a total reflection surface and an emission surface, and a third surface 12c (13c) which is a reflection surface provided on the front side are provided. The first surface 12a (13a), the second surface 12b (13b), and the third surface 12c (13c) each have a planar shape. The main body of the left (right) visual field optical system 12 (13) is a prism, and the third surface 12c (13c) includes a reflecting member R. The surface 12d is a surface located on the vertical plane including the second boundary L22 (see FIG. 9) and the optical axis of the imaging lens 22, and is joined to the surface 13d of the right visual field optical system 13. The left (right) visual field optical system 12 (13) has a shape extending below the central horizontal plane Sa (see FIGS. 2 and 6) including the central horizontal line L23 of the imaging lens 22 of the camera 21 and the optical axis. As shown in FIG. 2, the lower surface 12e (13e) is inclined downward as it goes toward the visual field in front view, and as shown in FIG. Inclined.

  Next, how the light incident from the left visual field is guided to the imaging lens 22 by the left visual field optical system 12 will be described. 4 is a partially enlarged view of FIG. 3, (a) is an enlarged view of part a, (b) is an enlarged view of part b, (c) is an enlarged view of part c, and (d) is an enlarged view of part d. . The left visual field optical system 12 portion is hatched to distinguish it from the surrounding air portion.

Light from the left field of view, the first surface 12a of the optical system 12 for the left visual field, an incident angle theta _1. Then, it enters the left visual field optical system 12 at a refraction angle θ ₂ (θ ₂ ≦ θ ₁ ) (see FIG. 4A). Although not shown because it is natural, part of the light incident on the first surface 12a is reflected at the reflection angle θ ₁ . The entered light is totally reflected at the reflection angle θ ₃ on the second surface 12b (see FIG. 4B). That is, the left visual field optical system 12 is designed such that the reflection angle θ ₃ is larger than the critical angle θ _C (not shown).

Here, total reflection will be briefly described. Light incident on the second surface 12b at the incident angle α ₁ from the left visual field optical system 12 (refractive index n: n> 1) side is emitted to the air side (refractive index is approximately 1) at the refractive angle α _2. Then, the relationship of Formula (1) is established approximately.
n · sin α ₁ = sin α ₂ (1)
Here, when the refraction angle α ₂ is 90 degrees, Expression (2) is established.
sin α ₁ = 1 / n (2)
That is, when the incident angle α ₁ is larger than the angle obtained by the expression (2), the light is not emitted to the air side. This is called total reflection, and α ₁ satisfying equation (2) is called a critical angle and is generally expressed as θ _C.

Light totally reflected at the third face 12c, is reflected at the reflection angle theta ₄ (see FIG. 4 (c)). Here, since the third surface 12c includes the reflecting member R, all the light is reflected regardless of the magnitude of the reflection angle θ ₄ . The reflected light is incident on the second surface 12b at an incident angle θ ₅ and is emitted out of the left visual field prism portion 12 at a refraction angle θ ₆ (θ ₆ ≧ θ ₅ ) (see FIG. 4D). That is, the left visual field optical system 12 is designed such that the reflection angle θ ₅ is smaller than the critical angle θ _C. The emitted light is incident on the imaging lens 22. In addition, since it is natural and not shown in figure, a part of light which injected into the 2nd surface 12b reflects with reflection angle (theta) ₅ . Also in the following drawings, description of refracted light and reflected light not involved in photographing is omitted.

  Similarly, light from the right visual field passes through the right visual field optical system 13 and enters the imaging lens 22. Here, since the light from the left and right visual fields incident on the imaging lens 22 is reflected twice, it is an erect image. In addition, the positional relationship between the second surface 12b from which light from the left visual field is emitted and the second surface 13b from which light from the right visual field is emitted maintains the positional relationship between the visual fields. That is, the light from the left visual field is incident on the upper left region 22a of the imaging lens 22, and the light from the right visual field is incident on the upper right region 22b of the imaging lens 22 (see FIG. 9). Therefore, it is not necessary to perform special reversal processing or the like with the camera 21, the display means 3, or the like. Then, the light from each visual field incident on the imaging lens 22 is displayed as an image of each visual field on the display means 3 via the image sensor 23 (see FIG. 11).

  As described above, the second surfaces 12b and 13b perform two actions such as total reflection and transmission, so that the left visual field optical system 12 and the right visual field optical system 13 can be reduced in size, particularly in the front-rear direction. It is. In addition, the weight can be reduced and the cost can be reduced.

  The left visual field optical system 12 and the right visual field optical system 13 have a refractive power of 0 diopter, and maintain the angle of view of the corresponding upper left region 22a and upper right region 22b of the imaging lens 22 (enlarge or reduce). No) optical system. Therefore, the left visual field optical system 12 and the right visual field optical system 13 are optical systems suitable for the left visual field and the right visual field that need to capture an imaging target from the vicinity of the vehicle 4 (see FIG. 8) to a distant place. .

  The left visual field optical system 12 and the right visual field optical system 13 may be integrally formed prisms, or prisms for the separate optical systems 12 and 13 fixed to each other by bonding or the like. May be. Further, as a material of the prism, glass, resin, transparent crystal or the like can be used.

(Optical system for lower visual field 14)
Next, the lower visual field optical system 14 will be described. 5A and 5B are perspective views of the lower visual field optical system, where FIG. 5A is a perspective view seen from the front, and FIG. 5B is a perspective view seen from the rear. 6 is a side view of the peripheral photographing apparatus of FIG. As shown in FIG. 5 and FIG. 6, the lower visual field optical system 14 includes a first surface 14a that is an incident surface provided on the front side, and a second surface 14b that is a reflective surface provided on the lower side. , A third surface 14c which is a reflection surface provided on the upper side, and a fourth surface 14d which is an emission surface provided on the rear side. The main body of the lower visual field optical system 14 is a prism, and the second surface 14b and the third surface 14c, which are reflection surfaces, include a reflection member R.
Each of the first surface 14a and the fourth surface 14d has a planar shape. The second surface 14b has a convex shape (concave shape when viewed from the outside) as viewed from the object side (prism side). The third surface 14c has a concave shape as viewed from the object side (prism side) (a convex shape as viewed from the outside).
It should be noted that the second surface 14b and the third surface 14c may be set at an angle that provides total reflection with respect to all incident light rays. In this case, the reflecting member R can be omitted. Further, the ridge line 14d _{1 serving as} the upper edge (on the side of the left visual field optical system 12 and the right visual field optical system 13) of the fourth surface 14d that is the exit surface determines the first boundary L21 (see FIG. 9). And is positioned between the imaging lens 22 and the second surfaces 12b and 13b which are the exit surfaces of the left visual field optical system 12 and the right visual field optical system 13.

  As shown in FIG. 6, the visual field region W1 captured in the upper left region 22a and the upper right region 22b of the imaging lens 22 via the left visual field optical system 12 and the right visual field optical system 13 is a vertical image within the photographing field angle. The corner ratio exceeds 50%. In other words, the upper visual field area W1 extends below the central horizontal line Sa and occupies an area exceeding 50% of the vertical field angle area W. Here, the visual field region W3 is a lower region imaged through the second optical system 11B, and is larger than the region W2 obtained by removing the visual field region W1 from the vertical field angle region W.

  Next, how the light incident from the lower visual field is guided to the imaging lens 22 by the lower visual field optical system 14 will be described. FIG. 7 is a partially enlarged view of FIG. 6, (a) is an enlarged view of a portion, (b) is an enlarged view of the b portion, (c) is an enlarged view of the c portion, and (d) is an enlarged view of the d portion. . In addition, the lower visual field optical system 14 portion is hatched to distinguish it from the surrounding air portion.

Light from the lower field of view, the first surface 14a of the optical lower vision system 14, at an incident angle theta _11. Then, it enters the lower visual field optical system 14 at a refraction angle θ ₁₂ (θ ₁₂ ≦ θ ₁₁ ) (see FIG. 7A). The entering light is reflected at the reflection angle θ ₁₃ by the second surface 14b (see FIG. 7B). The reflected light is reflected at the reflection angle θ ₁₄ by the third surface 14c (see FIG. 7C). The reflected light is incident on the fourth surface 14d at an incident angle θ ₁₅ and exits from the lower visual field optical system 14 at a refraction angle θ ₁₆ (θ ₁₆ ≧ θ ₁₅ ) (see FIG. 7D). . The emitted light is incident on the lower region 22c of the imaging lens 22 of the camera 21 to obtain a lower visual field image 3c (see FIGS. 9 and 10).

The second surface 14b, the third surface 14c, and the third surface 14c are totally reflected (θ ₁₃ ≧ θ _C , θ ₁₄ ≧ θ _C ). The angle of the surface 14c may be set. In this case, even when the reflecting member R is not installed, the loss of the reflected light amount can be reduced.

Here, the second surface 14b has a convex shape, and its refractive power φ _14b has a negative value. Therefore, the second surface 14b functions as a convex mirror, and the reflection on the second surface 14b spreads the light. The third surface 14c has a concave shape, and its refractive power φ _14c has a positive value. Therefore, the third surface 14c functions as a concave mirror, and the reflection on the third surface 14c collects light.
That is, the first surface 14a and the second surface 14b constitute a “first optical system” , and the third surface 14c and the fourth surface 14d constitute a “second optical system” . is doing.
The refractive power φ ₁ (= φ _14b ) of the entire first optical system and the refractive power φ ₂ (= φ _14c ) of the entire second optical system satisfy the following relationship.
φ ₁ <0
φ ₂ > 0
| Φ ₁ | >> | φ ₂ |
The lower visual field optical system 14 has a refractive power of −2 to 0 diopter as a whole system, that is, a combined optical system of the first optical system and the second optical system, and the lower visual field region 22 c of the imaging lens 22. It functions to enlarge the angle of view (horizontal, vertical). The lower visual field optical system 14 can be obtained by suitably setting the radii of curvature of the second surface 14b and the third surface 14c or by suitably setting the curved surface shape.

  Since the lower visual field optical system 14 includes two independent reflection surfaces (14b and 14c), the optical axis of the imaging lens 122 is set downward as in the conventional camera device 101 (see FIG. 15). Even if not, it is possible to photograph the lower visual field set at a suitable angle. Therefore, it is possible to prevent the imaging angle of the left and right visual field from being upward due to the angle of the imaging lens 22 being downward. Further, by adjusting the angles of the reflecting surfaces 14b and 14c, the elevation angle β of the lower visual field (direction of the visual field region W3) can be set to a desired angle (direction).

Further, the left visual field optical system 12 and the right visual field optical system 13 and the camera 21 are set so that the ridge line 14d ₁ of the fourth surface 14d of the lower visual field optical system 14 determines the first boundary L21. Is arranged. Accordingly, the first boundary L21 can be determined regardless of the shape of the lower surfaces 12e and 13e facing the first boundary L21 side of the left visual field optical system 12 and the right visual field optical system 13, and therefore, for the left visual field. The degree of freedom of the shapes of the optical system 12 and the right visual field optical system 13 is increased, and the degree of freedom of the division ratio is increased. In addition, by making the ridgeline 14d ₁ linear, the first boundaries L21 and L31 can be made linear and a more suitable image can be obtained. Further, as shown in FIG. 10, in the obtained image, the amount of vignetting K1 generated near the first boundary L31 can be suppressed, and each image 3a, 3b, 3c can be displayed in a large size. The positional relationship among the third surface 12c of the left visual field optical system 12, the third surface 13c of the right visual field optical system 13, and the fourth surface 14d of the lower visual field optical system 14 is based on the mutual relationship between the visual fields. Are arranged so as to maintain the positional relationship (that is, the lower left and right) (see FIGS. 10, 11, and 12).

  As shown in FIG. 6, the visual field region W1 captured in the upper left region 22a and the upper right region 22b of the imaging lens 22 via the left visual field optical system 12 and the right visual field optical system 13 is a vertical image within the photographing field angle. The corner ratio exceeds 50%. In other words, the upper visual field area W1 extends below the central horizontal line Sa and occupies an area exceeding 50% of the vertical field angle area W.

  Further, as shown in FIG. 6, since the left visual field optical system 12 and the right visual field optical system 13 have a shape extending below the central horizontal plane Sa, the first boundary L21 in FIG. Light from the left and right visual fields (arrows in FIG. 3) can also be imaged between the center horizontal line L23, which is a horizontal line passing through the center O21 of the imaging lens 22.

(Usage status and screen example)
Next, a usage example of the periphery monitoring system 1 will be described. FIG. 8 is a diagram illustrating a state in which the periphery monitoring system is installed in the vehicle. FIG. 9 is a diagram for explaining a region in the imaging lens. FIG. 10 is a diagram illustrating an example of a screen by the periphery monitoring system of FIG. 11A and 11B are diagrams for explaining the optical path of each field of view. FIG. 11A is a diagram for explaining the optical path according to the first embodiment, and FIG. 11B is a diagram for explaining the optical path of the conventional example.
As shown in FIG. 8, by installing the peripheral photographing device 2 on the front surface (here, the front grille) of the vehicle 4, the display unit 3 captures the left image taken through the visual field optical systems 12, 13, and 14. The visual field image 3a, the right visual field image 3b, and the lower visual field image 3c can be displayed (see FIG. 10). In FIG. 10, a first boundary L31, a second boundary L32, and a central horizontal line L33 correspond to the first boundary L21, the second boundary L22, and the central horizontal line L23 shown in FIG. , 3b, and 3c correspond to the upper left region 22a, upper right region 22b, and lower region 22c of the imaging lens 22 shown in FIG. Each of these images 3a, 3b, 3c is an erect image, and is displayed while maintaining the mutual position of each field of view. Since the amount of generation of vignetting K1 is suppressed, the images 3a, 3b, and 3c are displayed large, and are images suitable for viewing each visual field.

  When the vehicle 4 enters the intersection, the driver temporarily stops with the tip of the vehicle 4 slightly protruding into the intersection. Then, the camera 21 photographs the left and right roads via the left visual field optical system 12 and the right visual field optical system 13 of the peripheral photographing optical system 11. The display means 3 displays the captured image. The driver of the vehicle 4 looks at the left visual field image 3a and the right visual field image 3b on the display means 3 and confirms the situation of the left and right roads. Then, it is possible to check the safety from the situation of the left and right roads and enter the intersection.

  Further, the lower visual field image 3 c is obtained by photographing the blind spot in the lower front part of the vehicle 4 through the lower visual field optical system 14. The driver of the vehicle 4 can confirm the blind spot at the front lower side in addition to the situation of the left and right roads by looking at the display means 3. Further, when starting from a parking lot or a garage, the blind spot in the lower front direction can be confirmed by looking at the lower visual field image 3c of the display means 3.

  Since the peripheral photographing apparatus 2 according to the present embodiment uses the peripheral photographing optical system 11, the left visual field image 3a and the right visual field image 3b can be taken below the central horizontal line L33. Therefore, the size of each of the images 3a, 3b, and 3c can be adjusted to be substantially equal while suppressing the generation amount of the vignetting K1, and an image suitable for the driver to view can be obtained.

  In addition, the peripheral photographing device 2 reflects the light from the right and left and the lower visual field twice, and photographs each visual field as an erect image, and photographs while maintaining the relative position of each visual field. There is no need for special image processing.

Further, as shown in FIG. 11 (a), the light from the lower visual field reflects on the second surface 14b and the third surface 14c of the lower visual field optical system 14 having -2 to 0 diopters in the entire system. Therefore, the lower visual field is hard to be out of focus, and the angle of view of the lower visual field can be photographed larger than the angle of view of the imaging lens 22. That is, the lower visual field image 3c is displayed in a state of being smaller than the left and right visual field images 3a and 3b.
That is, as shown in FIG. 8, the imaging range A1 of the road surface that the peripheral photographing apparatus 2 can image via the lower visual field optical system 14 is directly in the peripheral photographing apparatus 2 without the lower visual field optical system 14. It is larger than the imaging range A2 of the road surface that can be imaged. Further, since the lower visual field optical system 14 does not significantly affect the focus of the imaging lens 22, as shown in FIG. 10, a lower visual field image 3c that captures a wide range and hardly causes a focus shift is obtained.
In the conventional example, as shown in FIG. 11B, light from the lower visual field is incident on the imaging lens 122 through the concave lens 114, so that the lower visual field is out of focus.
Usually, since the imaging object of the lower visual field is located closer to the imaging object of the left and right visual fields, the lower visual field optical system 14 having a refractive power of −2 to 0 diopter greatly affects the focus of the imaging lens 22. Therefore, there is almost no focus shift due to the installation of the lower visual field optical system 14. That is, since the refractive power of the lower visual field optical system 14 is -2 to 0 diopter, most of the imaging objects exist within the range of the rear depth of field (in the case of a value other than 0 diopter). Will be out of focus. Incidentally, the lower visual field optical system 14 forming the lower visual field optical path as shown in FIG. 11A has a refractive power of 0 diopter. Since the periphery monitoring system 1 according to the present embodiment suppresses the focus shift while increasing the angle of view of the lower visual field, it is possible to provide an image suitable for visual recognition of each visual field by the driver.

(Second embodiment)
Next, the lower-field optical system 44 according to the second embodiment of the present invention will be described focusing on differences from the lower-field optical system 14 according to the first embodiment.
FIG. 12 is a perspective view of a lower visual field optical system according to the second embodiment of the present invention. 13A is a front view of the lower visual field optical system, FIG. 13B is a plan view thereof, FIG. 13C is a bottom view thereof, and FIG. 13D is a side view thereof. 13 (e) is a rear view of the same. In FIGS. 12 and 13 and FIG. 14 described later, the reflecting members provided on the second surface and the third surface are omitted. The lower visual field optical system 44 according to the second embodiment is an optical system applicable to the periphery monitoring system 1 instead of the lower visual field optical system according to the first embodiment.
As shown in FIG. 12 and FIG. 13, the lower visual field optical system 44 includes a first surface 44 a that is an incident surface provided on the front side, and a second surface 44 b that is a reflective surface provided on the lower side. , A third surface 44c that is a reflection surface provided on the upper side, and a fourth surface 44d that is an emission surface provided on the rear side.
The first surface 44a has a concave shape when viewed from the object side (prism side) (a convex shape when viewed from the outside), and its refractive power φ _44a has a positive value. That is, the first surface 44a functions as a convex lens, and refraction at the first surface 44a collects light.
Similarly to the second surface 14b, the second surface 44b has a convex shape when viewed from the object side (prism side) (a concave shape when viewed from the outside), and its refractive power φ _44b is negative. Has the value of That is, the second surface 44b functions as a convex mirror, and the reflection on the second surface 44b spreads the light.
Similarly to the third surface 14c, the third surface 44c has a concave shape (convex shape when viewed from the outside) when viewed from the object side (prism side), and its refractive power φ _44c is positive. Has the value of That is, the third surface 44c functions as a concave mirror, and the reflection on the third surface 44c collects light.
The fourth surface 44d has a convex shape (concave shape when viewed from the outside) as viewed from the object side (prism side), and its refractive power φ _44d has a negative value. That is, the fourth surface 44d functions as a concave lens, and refraction at the fourth surface 44d spreads light.

In the second embodiment, the first surface 44 a and the second surface 44 b constitute a “first optical system” , and the third surface 44 c and the fourth surface 44 d are “second optical systems ”. Optical system ” .
Here, (power phi depends on _44a and the refractive power phi _44b of the second surface 44b of the first surface 44a) and the second refractive power of the entire optical system of the first refractive power of the entire optical system phi ₁₁ phi ₁₂ (depending on the refractive power phi _44d of the third power of the surface 44c phi _44c and fourth surface 44d) satisfies the following relationship.
φ ₁₁ <0
φ ₁₂ > 0
｜ φ ₁₁ ｜ ＞ ｜ φ ₁₂ ｜
The lower visual field optical system 44 has a refractive power of −2 to 0 diopter as the entire system, that is, the combined optical system of the first optical system and the second optical system, and is in the lower visual field region of the imaging lens 22. Functions to enlarge the angle of view (horizontal, vertical). The lower visual field optical system 44 can be obtained by suitably setting the respective radii of curvature of the first surface 44a, the second surface 44b, the third surface 44c, and the fourth surface 44d.

  Since the lower visual field optical system 44 imparts curvature to each surface, the optical aberration generated on each surface can be reduced by suitably setting these curvatures or suitably setting the curved surface shape. It becomes possible to correct.

Subsequently, examples of the optical system for the lower visual field will be described.
FIG. 14 is a cross-sectional view of the lower visual field optical system as viewed from the side, and corresponds to a cross-sectional view taken along the line AA of FIG. In FIG. 14, the radius of curvature of the first surface S1 is R1, the radius of curvature of the second surface S2 is R2, the radius of curvature of the third surface S3 is R3, and the radius of curvature of the fourth surface S4 is R4.
A horizontal line passing through the apex of the first surface S1 is L1, a horizontal line passing through the bottom of the lower field optical system is L2, and a horizontal line passing through the apex of the lower field optical system is L3. A vertical line passing through the vertex of the first surface S1 is L4, a vertical line passing through the vertex of the second surface S3 is L5, and a vertical line passing through the vertex of the fourth surface S4 is L6. A straight line parallel to the optical axis of the second surface S2 is L7, and a straight line parallel to the optical axis of the third surface S3 is L8. A surface continuous with the upper side of the first surface S1 (portion above the horizontal line L1) is a portion that does not function as the first surface S1 due to the optical path.
Further, the interval between the vertex of the first surface S1 and the vertex of the second surface S2 is D1, the interval between the vertex of the second surface S2 and the vertex of the third surface S3 is D2, and the distance between the vertex of the third surface S3. Let D3 be the distance between the vertex and the vertex of the fourth surface S4. The tilt angle of the second surface S2 is ω2, and the tilt angle of the third surface S3 is ω3. Note that the left and right widths and heights of the lower visual field optical system can be arbitrarily set.
Here, each numerical value of the optical system for the lower visual field according to Example 1 is shown in Table 1.

Here, the refractive index of the first surface S1 and the fourth surface S4 is the refractive index of the medium on the rear side (camera 21 side) of each surface. That is, the refractive index of the first surface S1 is the refractive index of the prism constituting the lower visual field optical system according to the example, and the refractive index of the fourth surface S4 is the refractive index of air (≈1). is there.
Further, D1 = 4.9 [mm], D2 = 3.6 [mm], and D3 = 0.2 [mm].
The refractive power of the optical system for the lower field according to Example 1 is −0.73681 diopter, and the field angle magnification is 129%.

  Subsequently, Table 2 shows numerical values of the optical system for the lower visual field according to Example 2.

The numerical values of D1, D2, and D3 are the same as those in the first embodiment.
The refractive power of the optical system for the lower visual field according to Example 2 is −1.684 diopter, and the field angle magnification ratio is 133%.

  The above-described lower-field optical systems according to Examples 1 and 2 correspond to the lower-field optical system 14 according to the first embodiment, and the formation direction of the curved surface on each surface also corresponds to the lower-field optical system 14. Is the same. The refractive powers of the optical systems for the lower visual field according to Examples 1 and 2 are in the range of not less than −2 diopter and not more than 0 diopter. In addition, the lower visual field optical systems according to the first and second embodiments have a function of expanding the field angle of the lower region 22c of the imaging lens 22.

  Subsequently, Table 3 shows numerical values of the optical system for the lower visual field according to Example 3.

The numerical values of D1, D2, and D3 are the same as those in the first embodiment.
The refractive power of the optical system for the lower visual field according to Example 3 is −0.07658 diopter, and the field angle magnification is 122%.

  Subsequently, Table 4 shows numerical values of the optical system for the lower visual field according to Example 4.

The numerical values of D1, D2, and D3 are the same as those in the first embodiment.
The refractive power of the optical system for the lower field according to Example 4 is −0.08201 diopter, and the field angle magnification is 128%.

  The above-described lower visual field optical system according to Examples 3 and 4 corresponds to the lower visual field optical system 44 according to the second embodiment, and the formation direction of the curved surface on each surface also corresponds to the lower visual field optical system 44. Is the same. The refractive power of the optical system for the lower field according to Examples 3 and 4 is in the range of not less than −2 diopter and not more than 0 diopter. Further, the lower visual field optical system according to Examples 3 and 4 has a function of expanding the angle of view of the lower region 22c of the imaging lens 22.

  As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to this but can change a design suitably in the range which does not deviate from the summary of this invention.

The shapes of the left visual field optical system, the right visual field optical system, and the lower visual field optical system are not limited to those illustrated. For example, the surface of each optical system can be realized by a mirror, a half mirror, a lens, or the like.
In each optical system, the arrangement of the surfaces functioning as convex (or concave) mirrors and convex (or concave) lenses can be appropriately changed in design. For example, in the lower visual field optical system 14 according to the first embodiment, the first surface 14a and the second surface 14b are flat surfaces (focal length ∞), and the third surface 14c is viewed from the object side. The first surface, the second surface, and the third surface are designed to be convex (functioning as a convex mirror), and the fourth surface 14d is convex (functioning as a concave lens) when viewed from the object side. The first surface may constitute a “first optical system” , and the fourth surface may constitute a “second optical system” .

Further, as a reference form, a configuration may be adopted in which either the left visual field optical system 12 or the right visual field optical system 13 in the first embodiment is omitted and the front visual field is directly photographed.

  In each embodiment, the convex or concave surface is a spherical shape, but may be an aspherical shape such as an elliptical shape. However, in the case of a spherical shape, the processing is easy.

Moreover, the structure which interposes an electrochromic layer and a photochromic layer in the optical path of each visual field may be sufficient.
According to such a configuration, it is possible to automatically adjust the amount of incident light.
In addition, when it is set as the structure which interposes the electrochromic layer and the photochromic layer between the main body of each optical system and the reflection member, a layer formation site | part can be limited and manufacture becomes easy. Also, the installation / non-installation of the reflecting member is optional.

  In addition, although only one lens on the peripheral photographing optical system side is illustrated as the imaging lens 22 of the camera 21, the camera 21 may be configured to include an optical system including a plurality of lenses as the imaging lens 22. Is natural.

Moreover, it is not limited to what is installed in the front surface of a vehicle, The structure installed in the rear surface of a vehicle and image | photographing a left visual field, a right visual field, and a back lower visual field may be sufficient.
Moreover, it is not limited to what is installed in a vehicle, It is applicable also to the surveillance camera in a building.

It is a schematic perspective view which shows the periphery monitoring system using the periphery imaging | photography optical system which concerns on 1st embodiment of this invention. It is the figure which looked at the periphery imaging device of FIG. 1 from the front. It is the figure which looked at the periphery imaging device of FIG. 1 from the top. FIG. 4 is a partially enlarged view of FIG. 3. It is a perspective view of the optical system for lower visual fields. It is the figure which looked at the peripheral imaging device of FIG. 1 from the side. It is the elements on larger scale of FIG. It is a figure which shows the state which installed the periphery monitoring system in the vehicle. It is a figure explaining the area | region in an imaging lens. It is a figure which shows the example of a screen by the periphery monitoring system of FIG. It is a figure explaining the optical path of each visual field, (a) is a figure explaining the optical path which concerns on 1st embodiment, (b) is a figure explaining the optical path of a prior art example. It is a perspective view which shows the optical system for lower fields which concerns on 2nd embodiment of this invention. It is an orthographic projection figure which shows the optical system for lower visual fields which concerns on 2nd embodiment of this invention. It is sectional drawing which looked at the optical system for lower fields from the side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Perimeter monitoring system 2 Peripheral imaging device 3 Display means 11 Peripheral imaging optical system 12 Left visual field optical system 13 Right visual field optical system 14,44 Lower visual field optical system 14a, 44a, S1 1st surface (1st optical system)
14b, 44b, S2 Second surface (first optical system)
14c, 44c, S3 Third surface (second optical system)
14d, 44d, S4 Fourth surface (second optical system)
21 Camera 22 Imaging lens 22a Upper left area 22b Upper right area 22c Lower area

Claims (4)

A peripheral photographing device comprising a camera and a peripheral photographing optical system that guides light from different fields of view to each of a plurality of regions on the imaging lens of the camera ,
The peripheral photographing optical system is
An optical system for the left field that guides light from the left field to the upper left region on the imaging lens;
An optical system for the right visual field that guides light from the right visual field to the upper right region on the imaging lens;
A lower visual field optical system for guiding light from the lower visual field to a lower region on the imaging lens;
With
The optical system for the lower visual field has a refractive power of −2 to 0 diopter and functions to enlarge the angle of view in the lower region on the imaging lens ,
Between the left visual field optical system, the right visual field optical system, and the camera so that an upper edge of the lower visual field optical system determines a boundary between the upper left region and the upper right region and the lower region. Peripheral photographing device characterized by being arranged in . The left visual field optical system, the right visual field optical system, and the lower visual field optical system reflect light from the corresponding visual field an even number of times and guide it to the corresponding region on the imaging lens as an erect image. The peripheral photographing apparatus according to claim 1, wherein the peripheral photographing apparatus is characterized .   The lower visual field optical system is reflected by the first surface on which light from the lower visual field is incident, the second surface on which the light incident on the first surface is reflected, and the second surface. A third surface on which the light is reflected, and a fourth surface on which the light reflected on the third surface is emitted, and a prism comprising:
  The first surface has a planar shape,
  The second surface functions as a convex mirror for the light,
  The third surface functions as a concave mirror for the light,
  The fourth surface has a planar shape,
  The combined optical system of the first surface, the second surface, the third surface, and the fourth surface has a refractive power of −2 to 0 diopter.
  The peripheral photographing apparatus according to claim 1 or 2, wherein   The lower visual field optical system is reflected by the first surface on which light from the lower visual field is incident, the second surface on which the light incident on the first surface is reflected, and the second surface. A third surface on which the light is reflected and a fourth surface on which the light reflected on the third surface is emitted;
  The first surface functions as a convex lens for the light,
  The second surface functions as a convex mirror for the light,
  The third surface functions as a concave mirror for the light,
  The fourth surface functions as a concave lens for the light,
  The combined optical system of the first surface, the second surface, the third surface, and the fourth surface has a refractive power of −2 to 0 diopter.
  The peripheral photographing apparatus according to claim 1 or 2, wherein

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