JP4773906B2 - Imaging device - Google Patents

Description

  The present invention generally relates to an imaging apparatus, and more particularly to an imaging apparatus capable of pan / tilt imaging. The present invention is suitable for a video camera that captures continuous images, for example.

  With the recent spread of imaging devices such as digital video cameras and digital cameras, such imaging devices are applied to various scenes, and higher quality imaging and smaller imaging devices are increasingly required. For example, a digital video camera is used as a surveillance video camera provided on the ceiling of a store or the like, and has a drive mechanism that enables a pan / tilt operation according to a subject to be monitored (field of view). A technique related to such a drive mechanism is disclosed in Patent Document 1.

  Patent Document 1 sets imaging conditions (pan angle value, tilt angle value, zoom magnification value) at a predetermined imaging position (monitoring focus) for a surveillance video camera. Then, the center coordinate of the electronic zoom cutout position on the image sensor with respect to the imaging position is calculated from the pan angle value and the tilt angle value, and the electronic zoom magnification value for the current optical zoom magnification value is calculated from the zoom magnification value. Next, the camera unit is switched to the target imaging position and electronic zoom processing is performed from the electronic zoom cut-out position, and then pan / tilt and optical zoom are driven in a direction to cancel the electronic zoom processing, and the optical zoom processed image is displayed. Output.

In addition, in the imaging apparatus having an optical system that guides the light from the subject to the imaging element by deflecting the light from the subject in the direction of approximately 90 degrees by the reflection element, the rotation angle of the reflection element (prism) and the rotation angle of the objective lens A tilt mechanism configured to double the relationship is proposed.
JP 2004-7261 A

  However, the technique disclosed in Patent Document 1 is a technique for a surveillance video camera. For example, in Patent Document 1, when opening / closing of a door is detected, the door portion is enlarged and displayed by electronic zoom based on preset information, and then pan / tilt from an initial position toward a preset pan position and tilt position. Operate the optical zoom while operating. Thereby, the magnification of the electronic zoom is gradually lowered to cancel the electronic zoom with the optical zoom, and finally a high-quality image can be obtained by the optical zoom. However, Patent Document 1 gives priority to the specifications required for a surveillance video camera (that is, capture a target subject in a short time), and does not consider image degradation due to electronic zoom at the initial stage of imaging. Furthermore, since the structure and control of the camera are different, it cannot be applied to a video camera used by a general user.

  On the other hand, the tilt mechanism proposed by the present applicant can prevent image deterioration, but requires components and a drive source of the tilt mechanism, resulting in an increase in size and cost of the apparatus.

  Accordingly, an object of the present invention is to provide an imaging apparatus capable of realizing pan / tilt imaging without causing image deterioration, apparatus enlargement, and cost increase.

In order to achieve the above object, an imaging apparatus according to one aspect of the present invention is an imaging apparatus that images a subject, and includes an objective lens and an imaging surface that converts light from the objective lens into an electrical signal. An element, a reflection element that deflects light from the objective lens and guides the light to the imaging element, a lens barrel unit that includes the reflection element, and the lens barrel unit that rotates around the optical axis of the imaging element A drive mechanism that is coupled to the lens base unit, an iris base plate provided in the lens barrel unit, a stepping motor fixed by the iris base plate, an output gear that rotates by receiving the driving force of the stepping motor, and the output gear. has a support member for rotatably supporting the entire lens barrel unit, and when the first image pickup, in a time of the second imaging changing the imaging direction from the time the first imaging, the Wherein the region for reading the electrical signals of the image plane is different.

  Further objects and other features of the present invention will become apparent from the preferred embodiments described below with reference to the accompanying drawings.

  According to the present invention, it is possible to provide an imaging apparatus capable of realizing pan / tilt imaging without degrading an image, increasing the size of the apparatus, and increasing the cost.

  Hereinafter, an imaging apparatus according to an aspect of the present invention will be described with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

  The imaging apparatus 1 of the present invention is an imaging apparatus that captures an image of a subject, and is embodied as a digital video camera in the present embodiment. The imaging apparatus 1 has a reflective optical system 10 as shown in FIG. 1 as a main component. Here, FIG. 1 is a schematic cross-sectional view showing a configuration of an optical system 10 included in the imaging apparatus 1.

  Referring to FIG. 1, reference numeral 101 denotes an objective lens that is an optical element positioned on the first optical axis A. Reference numeral 102 denotes a reflecting element that bends (deflects) light from the objective lens 101 by approximately 90 degrees and guides the light to an imaging element 106 described later. In other words, the reflecting element 102 bends (deflects) the first optical axis A by approximately 90 degrees and guides it to the second optical axis B. Here, the first optical axis A is the optical axis of the objective lens 101, and the second optical axis B is the optical axes of the imaging lens 105 and the imaging element 106 described later.

  In this embodiment, the reflecting element 102 is a prism, and the first cemented lens 103 and the second cemented lens 104 are bonded (fixed) to the incident plane portion 102a and the exit plane portion 102b of the prism. That is, the first cemented lens 103 is located between the objective lens 101 and the reflective element 102, and the second cemented lens 104 is located between the reflective element 102 and the imaging lens 105.

  The imaging lens 105 is a lens group including a plurality of lenses, and is disposed on the second optical axis B. Reference numeral 106 denotes an image pickup element having an image pickup surface that converts light that has passed through the objective lens 101, the first cemented lens 103, the reflecting element 102, the second cemented lens 104, and the image pickup lens 105 into an electric signal. It is arranged on the optical axis B. In the present embodiment, the image sensor 106 is constituted by a CCD.

  The light transmitted through the objective lens 101 is incident on the reflective element 102 via the first cemented lens 103 and deflected (reflected) by the reflective surface 102 c of the reflective element 102. The light reflected by the reflecting surface 102 c of the image sensor 102 passes through the second cemented lens 104, passes through the photographing lens 105, and forms an image on the image sensor 106.

  FIG. 2 is a perspective view of a main part of the barrel unit 20 in which the reflection type optical system 10 shown in FIG. 1 is incorporated. The lens barrel unit 20 also includes a panning drive mechanism PM for driving panning, as will be described later.

  Referring to FIG. 2, reference numeral 201 denotes a CCD holder that constitutes a part of a lens frame. In the CCD holder 201, a CCD that is the image sensor 106 is disposed on the image plane of the optical system 10, and components of the lens barrel unit 20 described later are disposed inside. A prism holder 202 including the objective lens 101 and the reflective element (prism) 102 is disposed on the CCD holder 201 via the flange portion 201a. In the present embodiment, the prism holder 202 is fixed to the opposite side of the imaging surface of the optical system 10 on which the image sensor 106 is disposed by screws or the like (not shown).

  Reference numeral 203 denotes a second group holder that contains a second group lens that forms part of the imaging lens 105. The second group lens is a so-called variator lens having a zooming function of the photographing optical system. The second group holder 203 is slidably supported by a first guide bar 204a fixed to the CCD holder 201 along the second optical axis B, and is also slidable by the second guide bar 204b. The rotation around 204a is restricted.

  A rack 205 is attached to the second group holder 203. Reference numeral 206 denotes a stepping motor for driving the second group holder 203 along the second optical axis B. A lead screw 207 is fixed to the output shaft of the stepping motor 206. Further, the lead screw 207 is connected to the rack 205 via a screw. Accordingly, the second group holder 203 can be moved (advanced / retracted) along the second optical axis B as the lead screw 207 rotates.

  Reference numeral 208 denotes a fourth group holder that includes a fourth group lens that forms part of the imaging lens 105. The fourth group lens is a so-called compensator lens having a correction function of the photographing optical system. Similar to the second group holder 203, the fourth group holder 208 is slidably supported along the second optical axis B by the first guide bar 204a and the second guide bar 204b. A rack (not shown) is attached to the fourth group holder 208. As a result, like the second group holder 203, the output of the stepping motor 209 is transmitted to a lead screw (not shown), and the fourth group holder 208 is moved (advanced / retracted) along the second optical axis B by driving the rack. be able to.

  Reference numeral 30 denotes an iris unit that regulates a transmission amount (light quantity) of light from the objective lens 101 (imaging lens 105). A panning drive mechanism PM, which will be described later, is integrally attached to the iris unit 30. The panning drive mechanism PM rotates the lens barrel unit 20 around the second optical axis B to enable panning imaging of the imaging device 1.

  FIG. 3 is a perspective view showing a main part of the configuration of the panning drive mechanism PM. The panning drive mechanism PM constitutes a part of the iris unit 30. The panning drive mechanism PM rotates the lens barrel unit 20 around the second optical axis B as will be described later.

  Referring to FIG. 3, reference numeral 301 denotes an iris base plate, which has an opening 301a on the optical axis (second optical axis B). An iris blade (not shown) shields the opening 301a so that appropriate exposure can be obtained. In other words, the iris blade controls the amount of light from the objective lens 101 (imaging lens 105). In addition, a third group lens constituting a part of the imaging lens 105 is fixed to the lens receiving portion 301c located in the back of the opening 301a.

  Reference numeral 302 denotes a stepping motor, which is fixed to the iris base plate 301 by screws (not shown). A pinion gear 303 is press-fitted into the output shaft 302 a of the stepping motor 302.

  Reference numeral 304 denotes a first reduction gear that is rotatably supported on the shaft 301 b of the iris base plate 301. The large gear portion 304a of the first reduction gear 304 is coupled (gear coupled) with the pinion gear 303.

  Reference numeral 305 denotes an intermediate ground plane. The intermediate base plate 305 is fixed to the iris base plate 301 with screws (not shown) after the first reduction gear 304 is incorporated into the iris base plate 301.

  Reference numeral 306 denotes a second reduction gear, which is rotatably supported by a support shaft 305a of the intermediate base plate 305. The large gear portion 306a of the second reduction gear 306 is coupled (gear-coupled) with the small gear portion 304b of the first reduction gear 304.

  Reference numeral 307 denotes a third reduction gear that is rotatably supported on a support shaft 305b of the intermediate base plate 305. The large gear portion 307 a of the third reduction gear 307 is coupled (gear-coupled) with the small gear portion 306 b of the second reduction gear 306.

  Reference numeral 308 denotes an output gear that is rotatably supported on a support shaft 305c of the intermediate base plate 305. The gear portion 308 a of the output gear 308 is coupled (gear coupled) to the small gear portion 307 b of the third reduction gear 307.

  Reference numeral 309 denotes a gear presser, which is fixed to the iris base plate 301 with screws (not shown) after the above-described reduction gears (first to third reduction gears) are incorporated. The gear press 309 holds each of the reduction gears (first to third reduction gears) described above in a rotatable manner, and constitutes a reduction gear unit.

  In the reduction gear unit, the rotation of the stepping motor 302 is transmitted to each of the reduction gears (first to third reduction gears) described above, and is finally transmitted to the output gear 308. At this time, the rotational force of the stepping motor 302 is transmitted to the output gear 308 in an enlarged manner. The output gear 308 is arranged so that a part thereof protrudes from the outer peripheral surface of the CCD holder 201 as will be described later.

  FIG. 4 is a main part perspective view showing the panning drive mechanism PM in which the first reduction gear 304, the second reduction gear 306, the third reduction gear 307, and the iris blades 310a and 310b are incorporated.

  Referring to FIG. 4, the iris blades 310a and 310b shield the opening 301a of the iris base plate 301 as described above. Reference numeral 311 denotes an iris driving actuator. The iris blades 310a and 310b are rotatably supported on the support shaft 301b of the iris base plate 301, and the drive shaft 311a of the actuator 311 is slidably engaged with the engagement hole. Therefore, the iris blades 310a and 310b can control the opening amount (opening ratio) of the opening 301a of the iris base plate 301 by rotating the actuator 311 (that is, obtain appropriate exposure).

  Reference numeral 312 denotes an ND filter composed of a semi-transmissive film that regulates the amount of transmitted light (transmitted light amount). The ND filter 312 is rotatably supported on the support shaft 301 d of the iris base plate 301. Further, the engagement hole 312 a of the ND filter 312 is slidably engaged with the drive shaft 311 a of the actuator 311. Thus, the ND filter 312 moves (advances and retreats) to the opening formed by the opening 301a and the iris blades 310a and 310b as the actuator 311 is driven, and can control the amount of transmitted light.

  FIG. 5 is a main part perspective view showing the components (the iris unit 30, the second group holder 203, the fourth group holder 208, etc.) of the panning drive mechanism PM incorporated in the CCD holder 201.

  Referring to FIG. 5, the iris unit 30 is fixed to the CCD holder 201 with a screw or the like (not shown). The second group holder 203 and the fourth group holder 208 are supported by the first guide bar 204a and the second guide bar 205b so as to be slidable in the optical axis direction.

  When the stepping motor 302 rotates to pan the entire lens barrel unit 20, the driving force is transmitted to each reduction gear (first to third reduction gears) and to the output gear 308. As described above, the output gear 308 is disposed so that a part thereof protrudes from the outer peripheral surface of the CCD holder 201. Accordingly, the panning drive mechanism PM is housed inside the CCD holder 201 without affecting the operation of the second group holder 203 or the fourth group holder 208. Thereby, size reduction of the panning drive mechanism PM can be realized.

  FIG. 6 is a perspective view showing a main part of the lens barrel unit 20 that is rotatably supported. Referring to FIG. 6, reference numeral 313 denotes a CCD cover, which forms the other side of the lens frame. The CCD cover 313 is fixed to the CCD holder 201 with screws or the like (not shown) after the components of the panning drive mechanism PM are incorporated into the CCD holder 201.

  The holding member 314 and the support member 315 support the entire barrel unit 20 in a rotatable manner. The support member 315 is formed with an internal gear 315 a that is coupled (gear-coupled) with the output gear 308. As a result, the entire lens barrel unit 20 rotates around the optical axis as the output gear 308 rotates. As a result, panning photography can be performed so that the composition intended by the user is obtained.

  Next, the tilt shooting in the image pickup apparatus 1 of the present invention will be described. FIG. 7 is a schematic plan view showing the imaging surface IS of the imaging device (CCD) 106 used in the imaging device 1. In FIG. 7, IA1 is an area (reading area) that is used during normal imaging (at the time of first imaging) (that is, an electrical signal is read out), and has an aspect ratio of, for example, 3: 4.

  For example, when the screen size of the image pickup surface of the image pickup element 106 is 1 / 2.5 inch size, the image circle is approximately φ7.1 mm. Therefore, if the screen size has an aspect ratio of 3: 4, the long side of the imaging surface IS of the imaging device 106 used during normal shooting is 5.68 mm, and the imaging surface IS of the imaging device 106 used during normal shooting is used. The short side is 4.26 mm.

  However, the imaging element 106 in the present embodiment has a square imaging surface IS having a side length of 5.68 mm (that is, a long side of the imaging surface IS of the imaging element 106 used during normal imaging). Have At the time of normal imaging, as described above, the imaging is performed with the screen size of the aspect ratio of 3: 4 using the area IA1 on the imaging surface having a side length of 5.68 mm. Therefore, above and below the square imaging surface IS, there are areas NIAa and NIAb that are not used at the time of the first imaging (that is, non-reading areas where no electrical signal is read). The long sides of the regions NIAa and NIAb are 5.68 mm, and the short sides of the regions NIAa and NIAb are 0.71 ((5.68−4.26) / 2) mm. That is, the imaging element 106 has an imaging surface IS larger than the area IA1 from which an electrical signal is read out during normal imaging (first imaging). Specifically, the imaging surface IS includes an area IA1 from which an electrical signal is read during imaging, and areas NIAa and NIAb from which an electrical signal is not read during normal imaging.

  In the present embodiment, the areas NIAa and NIAb are used during tilt shooting (second shooting). Specifically, the screen size of the aspect ratio of 3: 4 including the area NIAa is obtained during tilt imaging (second imaging) in which the imaging direction is changed upward from the normal imaging (first imaging). The electrical signal is read from the area IA2a. On the other hand, in tilt imaging (second imaging) in which the imaging direction is changed downward from normal imaging (first imaging), an area IA2b having a screen size of 3: 4 including the area NIAb Read electrical signal from. That is, the area for reading the electrical signal on the imaging surface IS differs between normal imaging and tilt imaging.

  In addition, the image circle of the image sensor 106 of the present embodiment having a square imaging surface IS is a circle whose diameter is a square diagonal line with a side of 5.68 mm, and the diameter is φ8.03 mm. Therefore, when an electrical signal is read from the area IA2a or IA2b during tilt shooting, the electrical signal cannot be read from the upper or lower corner area (that is, the area outside the image circle). However, since such a region is extremely small, it can be ignored. More preferably, an electronic tilt mechanism that does not impair optical performance by designing the above-described photographing optical system with an image circle φ8.03 from the beginning. Can be realized.

  Here, the specifications of the optical system 10 of the image pickup apparatus 1 are set, and tilt shooting by the image pickup apparatus 1 will be specifically described. First, it is assumed that the focal length f of the photographing optical system including the prism which is the reflecting element 102 is a specification expressed by the following formula 1.

Here, the number in parentheses is a numerical value converted into the focal length f when a 35 mm silver salt film is used.

  Accordingly, when the angle at which the electronic tilt can be calculated, it is expressed by the following formula 2 when wide, and by the following formula 3 when tele.

For example, assuming that a subject 3 m ahead is being imaged, how much the subject is tilted up and down by each electronic tilt is calculated. The size of the subject 3 m away is expressed by the following Equation 4 where the short side L _TW and the long side are L _CW .

Accordingly, the shift amount δ _{W at the} center of the screen when the electronic tilt of 6.33 degrees is performed in the wide mode is expressed by the following Equation 5.

  Referring to Equation 5, the short side direction of the subject is tilted vertically by 333 / 1997≈ ± 16.7% due to electronic tilt.

Similarly, consider the case of electronic tilt with respect to a subject 3 meters away during tele. The size of the subject 3 m ahead is expressed by the following Equation 6 when the short side L _TT and the long side L _CT are set.

Therefore, when the telephoto, the deviation amount [delta] _T of the center of the screen when the 1.34 degree of the electronic tilt is expressed by Equation 7 below.

  Referring to Expression 7, the short side direction of the subject is tilted up and down by 70.2 / 421≈ ± 16.7% by electronic tilt. This represents that the vertical direction ± 16.7% of the subject can be photographed by the electronic tilt regardless of the focal length f. Such a value is a constant value regardless of the subject distance and the focal length.

Here, the focal length of the imaging lens 105 f, and an object distance is d, the length L _T of the short-side direction of the object is expressed by the following Equation 8.

  Further, the angle θ at which the electronic tilt is possible when the focal length is f is expressed by the following Equation 9.

  The deviation δ of the subject center at the subject distance is expressed by Equation 10 below.

Accordingly, the region E _T capable electronic tilt is expressed by the following equation 11.

  This means that the electronic tiltable area on the image sensor 106 and the electronic tiltable area on the subject are constant regardless of the subject distance and the focal length of the photographing lens.

  As described above, the imaging apparatus 1 can realize pan / tilt imaging without causing image degradation, apparatus enlargement, and cost increase.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist. For example, in this embodiment, at the time of electronic tilt shooting, a long-side direction is made equal to one side of an image sensor having a square imaging surface, thereby shooting a subject image with the highest image quality according to the aspect ratio. Made possible. However, the imaging surface of the image sensor is configured in the same way as the normal aspect ratio, and at the time of electronic tilt shooting, an electric signal using a part of the image sensor is read in advance by electronic zoom, and the vertical direction is left as necessary. An area of the image pickup surface may be used. In this case, the electronic zoom enables shooting at a longer focal point than the focal length of the original shooting optical system, and the area of the image sensor used for shooting is reduced, so that the image quality of the captured image is deteriorated. . However, for example, when shooting a moving image by pan / tilt using a CCD with 5 million pixels, there is no problem in terms of image quality if shooting is performed with VGA image quality.

It is a schematic sectional drawing which shows the structure of the optical system which the imaging device as one side of this invention has. It is a principal part perspective view of the lens-barrel unit in which the reflection type optical system shown in FIG. 1 is integrated. It is a principal part perspective view which shows the structure of the panning drive mechanism which the imaging device of this invention has. It is a principal part perspective view which shows the panning drive mechanism in which the 1st reduction gear, the 2nd reduction gear, the 3rd reduction gear, and iris blade which were shown in FIG. 3 were integrated. It is a principal part perspective view which shows the component of the panning drive mechanism integrated in the CCD holder shown in FIG. It is a principal part perspective view which shows the lens-barrel unit supported rotatably. It is a schematic plan view which shows the imaging surface of the image pick-up element (CCD) used for the imaging device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 10 Optical system 101 Objective lens 102 Reflective element 102a Incident plane part 102b Ejection plane part 102c Reflective surface 105 Imaging lens 106 Imaging element 20 Lens barrel unit 203 Second group holder 206 Stepping motor 207 Lead screw 208 Fourth group holder 209 Stepping motor 30 Iris unit 301 Iris base plate 301a Opening 302 Stepping motor 303 Pinion gear 304 First reduction gear 305 Intermediate base plate 306 Second reduction gear 307 Third reduction gear 308 Output gear 309 Holding gears 310a and 310b Iris blade 311 Actuator 312 ND filter A 1st optical axis B 2nd optical axis PM Panning drive mechanism IS Imaging surface

Claims (4)

An imaging device for imaging a subject,
An objective lens;
An imaging device having an imaging surface for converting light from the objective lens into an electrical signal;
A reflective element that deflects light from the objective lens and guides it to the imaging element;
A lens barrel unit containing the reflective element;
A drive mechanism for rotating the lens barrel unit around the optical axis of the image sensor ;
An iris base plate provided in the lens barrel unit;
A stepping motor fixed by the iris base plate;
An output gear that rotates in response to the driving force of the stepping motor;
A support member coupled to the output gear and rotatably supporting the lens barrel unit ;
An imaging apparatus, wherein a region for reading out the electrical signal on the imaging surface is different between the first imaging and the second imaging in which the imaging direction is changed from the first imaging.   The imaging apparatus according to claim 1, wherein the imaging element has a square imaging surface.   The image pickup apparatus according to claim 1, wherein the image pickup device has an image pickup surface larger than an area from which the electric signal is read out during the first image pickup. The imaging surface includes a read area that reads the electrical signal during the first imaging, and a non-read area that does not read the electrical signal during the first imaging,
The imaging apparatus according to claim 1, wherein an area from which the electrical signal is read out during the second imaging includes the non-readout area.