JP2021176207A - Imaging apparatus - Google Patents

Abstract

To provide a small-sized imaging apparatus that performs illumination and imaging of a subject through a common optical system, while satisfactorily correcting a drop in the quantity of peripheral light.SOLUTION: An imaging apparatus 1 has: an imaging element 8 that picks up an image of imaging light incident on an imaging optical system from an imaging area; an illumination unit 14 that emits illumination light radiated to the imaging area through the imaging optical system; and a light path separation element 6 that reflects one of the illumination light and the imaging light and transmits the other to direct the illumination light to the imaging optical system and direct the imaging light from the imaging optical system to the imaging element. The illumination unit has a first light source unit 16 that emits first illumination light toward the light path separation element, a second light source unit 17 that emits second illumination light in a direction opposite to the first light source unit, and a reflecting member 18 that reflects the second illumination light to be directed to the light path separation element through the periphery of the first light source unit.SELECTED DRAWING: Figure 1

Description

The present invention relates to an imaging device that illuminates a subject and captures images through a common optical system.

By performing the illumination and imaging of the subject through a common optical system (imaging optical system), it is possible to reduce the deviation from the illumination region with respect to the imaging region (imaging region) on the subject side. However, since the light from the light source is applied to the subject through the imaging optical system, is reflected by the subject, and passes through the imaging optical system twice before reaching the imaging surface through the imaging optical system, the imaging is performed. Peripheral light falloff due to the optical system is likely to occur.

Such a drop in peripheral illumination is different in the amount of light emitted between the light source for illuminating the central portion of the imaging region and the light source for illuminating the peripheral portion as in the imaging apparatus disclosed in Patent Document 1 and Patent Document 2. It is possible to reduce (correct) by having.

Japanese Unexamined Patent Publication No. 07-190726 Japanese Unexamined Patent Publication No. 2008-205227

However, it is difficult to miniaturize the image pickup device in the configuration in which a large number of light sources are arranged on the same substrate surface as in the image pickup device disclosed in Patent Documents 1 and 2.

The present invention provides a compact imaging device that illuminates and images a subject through a common optical system while satisfactorily correcting peripheral illumination falloff.

The imaging device as one aspect of the present invention includes an imaging element that captures imaging light incident on the imaging optical system from the imaging region, an illumination unit that emits illumination light that is emitted to the imaging region through the imaging optical system, and illumination light. It has an optical path separation element that directs the illumination light to the imaging optical system and directs the imaging light from the imaging optical system to the imaging element by reflecting one of the imaging lights and transmitting the other. The illumination unit includes a first light source unit that emits a first illumination light toward the optical path separation element, a second light source unit that emits a second illumination light in the direction opposite to the first light source unit, and a second light source unit. It is characterized by having a reflecting member that reflects the illumination light of the above through the periphery of the first light source unit and toward the light path separating element.

According to the present invention, it is possible to realize a compact image pickup apparatus capable of illuminating and imaging a subject through a common optical system while satisfactorily correcting the drop in peripheral illumination.

The cross-sectional view which shows the structure of the illumination part in the image pickup apparatus which is Example 1 of this invention. The perspective view of the surveillance camera system using the image pickup apparatus of Example 1. FIG. The perspective view of the image pickup apparatus of Example 1. FIG. Sectional drawing of the image pickup apparatus of Example 1. FIG. An exploded perspective view of the image pickup apparatus of the first embodiment. The figure which shows the lighting substrate in Example 1. FIG. The block diagram which shows the electrical structure of the image pickup apparatus of Example 1. FIG. The flowchart which shows the peripheral illumination correction processing in Example 1. FIG. The figure which shows the peripheral light amount correction pattern in Example 1. FIG. The figure which shows another peripheral illumination correction pattern in Example 1. FIG. The figure which shows the reflection member in Example 2 of this invention. The figure which shows the illumination condensing lens in Example 3 of this invention.

Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 2 shows a surveillance camera system 100 as an imaging system using the imaging device 1 according to the first embodiment of the present invention. In the surveillance camera system 100, the image pickup apparatus 1 is pan-rotated and tilt-rotated around the pan-axis P and the tilt axis T orthogonal to the pan-axis P by the drive mechanism 101. As a result, the imaging direction of the imaging device 1 is changed. By reducing the size and weight of the image pickup device 1, the load on the drive mechanism 101 can be reduced and the size can be reduced, which is effective for the size reduction of the surveillance camera system 100.

FIG. 3 shows the appearance of the image pickup device 1, and FIG. 4 shows a cross section of the image pickup device 1 cut along the image pickup optical axis X. Further, FIG. 5 shows the image pickup apparatus 1 in an exploded manner. Further, FIG. 7 shows the electrical configuration of the image pickup apparatus 1.

The image pickup apparatus 1 includes a lens group L1 held by the fixing member 2, zoom lens groups L2 and L3 held by the moving frames 3 and 4, respectively, an aperture unit 13, and a focus lens group held by the moving frame 5. It includes an imaging optical system configured by L4. The imaging optical system may be interchangeable (detachable) with respect to the imaging device 1.

The moving frames 3 to 5 are in the direction in which the imaging optical axis X, which is the optical axis of the imaging optical system, is extended by the two guide bars whose ends are held by the fixing members 10 and 11, respectively (hereinafter referred to as the imaging optical axis direction). It is supported so that it can be moved. Rack members that engage with the lead screws of the stepping motors 23, 24, and 25 are attached to each of the moving frames 3, 4, and 5. By driving the stepping motors 23 to 25 and rotating the lead screw, the moving frames 3 to 5 move in the image pickup optical axis direction via the rack member. Zooming is performed by moving the zoom lens groups L2 and L3 together with the moving frames 3 and 4 in the image pickup optical axis direction, and focusing is performed by moving the focus lens group L4 together with the moving frame 5 in the image pickup optical axis direction.

In the diaphragm unit 13, the diaphragm blades (not shown) are driven in the opening / closing direction by the stepping motor 26 to change the size of the aperture diameter, so that the diaphragm unit 13 is incident from the subject side, passes through the image pickup optical system, and enters the image sensor 8. Adjust the amount of light that reaches.

Further, the image pickup device 1 has an image pickup element 8. The image pickup element 8 is a photoelectric conversion element such as a CCD sensor or a CMOS sensor, and images a subject image formed by the imaging optical system (photoelectric conversion). The image sensor 8 is mounted on the image sensor substrate 9, and the image sensor substrate 9 is held by the fixing member 12.

Further, the image pickup apparatus 1 includes a polarization beam splitter (PBS) 6 as an optical path separation element arranged between the image pickup optical system and the image pickup element 8 and held by the PBS holding frame 7. PBS6 has a property of reflecting S-polarized light (first polarized light) and transmitting P-polarized light (second polarized light) having a polarization direction different from that of S-polarized light. In this embodiment, the case where PBS is used as the optical path separation element has been described, but a half mirror may be used instead of PBS. The PBS holding frame 7 is held by the fixing member 11 so that the PBS 6 forms an angle of 45 degrees with respect to the imaging optical axis X as shown in FIG.

Further, the image pickup apparatus 1 includes an illumination unit 14. The illumination unit 14 is a unit that emits illumination light to irradiate the subject, so that the illumination optical axis XL, which is the optical axis thereof, forms an angle of 45 degrees with respect to the half mirror 6 and is orthogonal to the imaging optical axis X. It is located in. The illumination unit 14 includes an illumination substrate 15, a first light source unit 16, a second light source unit 17, a reflection member 18, a cover 19, an illumination condensing lens (optical member) 20, a spacer 21, and the like. It is composed of a fixing sheet metal 22 and is assembled to the fixing member 11 from the same direction (upward direction) as shown in FIG. The first and second light source units 16 emit illumination light (white light, infrared light, etc.) as S-polarized light which is linearly polarized light. Details of the other lighting units 14 will be described later.

In the image pickup apparatus 1 configured in this way, as shown in FIG. 7, the illumination light as S-polarized light emitted from the illumination unit 14 is reflected by the PBS 6 and passes through the imaging optical system to the imaging region including the subject. Be irradiated. The illumination light diffusely reflected by the subject is incident on the imaging optical system as unpolarized imaging light, and the P-polarized light of the imaging light passes through PBS 6 to form a subject image on the imaging element 8. This makes it possible to simultaneously illuminate the subject and perform imaging through an imaging optical system, which is a common optical system. By performing illumination and imaging through a common optical system, it is possible to reduce the deviation (paralux) of the illumination region, which is the irradiation region of the illumination light with respect to the imaging region. That is, the position and size of the illumination area can be adjusted to the position and size of the imaging area. The image pickup signal as an electric signal output from the image pickup device 8 that has captured the subject image is input to the camera control unit 102 shown in FIG. 7.

The camera control unit 102 is a microcomputer including a CPU, an MPU, and the like, and communicates with an external terminal 200 such as a personal computer via a network (LAN, the Internet, etc.) (not shown). The camera control unit 102 converts an image pickup signal as an analog signal input from the image pickup element 8 into a digital signal, and performs various image processing on the digital signal to generate image data. The image data is transmitted to the external terminal 200 and displayed or recorded on the monitor.

Further, the camera control unit 102 controls the driving of the stepping motors 23 to 26 according to the instruction from the external terminal 200 and the information such as the contrast value and the brightness value acquired from the image data. Further, the camera control unit 102 controls the lighting / extinguishing of the first and second light source units 16 and 17 of the lighting unit 14 and the amount of light emitted. The camera control unit 102 controls the amount of light emitted from the first and second light source units 16 and 17 by using the correction table stored in the correction table storage unit 103 as the internal memory.

FIG. 1A shows a detailed configuration of the periphery of the illumination unit 14 in the image pickup apparatus 1. FIG. 1 (b) shows the illumination unit 14 to PBS 6 cut along the line AA in FIG. 1 (a).

FIG. 6A shows the illumination substrate 15, and FIG. 6B shows a cross section of the illumination unit 14 orthogonal to the illumination optical axis XL and viewed from the reflection member 18 side. The illumination unit 14 in this embodiment makes it possible to change the amount of light in the peripheral portion of the illumination light with respect to the central portion by using two light source units (16, 17) which are not a large number, thereby making the imaging optical system 2 It satisfactorily corrects (reduces) the drop in peripheral light intensity due to passing through the circuit.

As shown in FIGS. 6A and 6B, the lighting substrate 15 has a circular light source connection in which the first light source unit 16 and the second light source unit 17 are electrically connected to surfaces opposite to each other. It has a portion 15a and fixed portions 15b and 15c having a shape extending in a direction parallel to the imaging optical axis X from the light source connecting portion 15a. The lighting board 15 is fixed to the fixing member 11 by the fixing portions 15b and 15c, and electric power for lighting the first and second light source portions 16 and 17 is input from the connector 15d connected to the fixing portion 15b. In this embodiment, the shape of the light source connection portion 15a is circular, but it may be a rectangle having an aspect ratio corresponding to the shape of the image pickup surface of the image pickup device 8.

The rectangular region B shown by the alternate long and short dash line in the cross section of FIG. 6B indicates a region corresponding to the rectangular imaging surface of the image pickup device 8 in this cross section, in other words, a region corresponding to the rectangular imaging region including the subject. ing. As will be described in detail later, the illumination light emitted from the second light source unit 17, reflected by the reflecting member 18, and passed through the region B reaches the imaging region.

As shown in FIGS. 1 (a), 1 (b) and 6 (a), the first light source unit 16 is the first light source connection unit 15a of the lighting substrate 15 on the PBS6 side (optical path separation element side). The second light source unit 17 is arranged on the surface, and the second light source unit 17 is arranged on the second surface of the light source connection unit 15a opposite to the first surface. The first and second light source units 16 and 17 are arranged so that their centers are both located on the illumination optical axis XL. The first and second light source units 16 and 17 are each composed of a single light emitting element such as an LED that emits surface light of a uniform amount of light and a polarization conversion element that converts unpolarized light from the light emitting element into S-polarized light. It is configured. The polarization conversion element emits S-polarized light of unpolarized light as it is, and rotates the polarization direction of P-polarized light, which has a different polarization direction from S-polarized light, by a phase plate to emit it as S-polarized light. When a half mirror is used as the optical path separation element, a polarization conversion element is unnecessary. A plurality of light emitting elements may be provided in each light source unit.

As shown in FIGS. 1 (a) and 1 (b), the reflective member 18 has a shape that is rotationally symmetric around the center thereof, and has an inner surface that has been mirrored by processing such as polishing or thin film deposition. The reflection member 18 is located by the fixing member 11 via the fixing sheet metal 22 so that the center thereof is located on the illumination optical axis XL as shown in FIG. 1A and the inner surface faces the second light source portion 17. It is held. The reflection member 18 has a convex reflection surface (first reflection surface) 18a protruding toward the second light source portion 17 on the inner surface of the central portion near the illumination optical axis XL, and is further separated from the illumination optical axis XL. The inner surface of the peripheral portion has a concave reflecting surface (second reflecting surface) 18b recessed on the side away from the second light source portion 17.

The cover 19 is attached to the fixing member 11 so as to cover the outer surface of the reflective member 18, and prevents unnecessary outside light and dust from entering the inside of the lighting unit 14. As shown in FIGS. 1A and 1B, the illumination condensing lens 20 is sandwiched and held between the illumination substrate 15 and the fixing member 11 together with the spacer 21.

In this embodiment, an opening 20a is provided in the central portion of the illumination condensing lens 20 including the illumination optical axis XL, and the first light source portion 16 is arranged in the opening 20a. With such an arrangement, the space efficiency in the lighting unit 14 can be improved and the lighting unit 14 can be miniaturized.

In the illumination unit 14 configured as described above, as shown in FIG. 1B, the illumination light (first illumination light) Lm from the first light source unit 16 directly goes to the entire PBS 6. On the other hand, the second light source unit 17 emits illumination light (second illumination light) Ls in the direction opposite to that of the first light source unit 16. The illumination light Ls is directed toward the convex reflecting surface 18a at the center of the reflecting member 18. The illumination light Ls reflected toward the peripheral portion by the convex reflection surface 18a is reflected by the concave reflection surface 18b and is reflected on the periphery (outside) of the illumination substrate 15, that is, the first and second light source portions 16, 17 Head to PBS6 through the perimeter of.

As described above, since the reflective member 18 has a rotationally symmetric shape centered on the illumination optical axis XL, the illumination light Ls from the second light source unit 17 is formed on the convex reflection surface 18a in the entire circumferential direction around the illumination optical axis XL. It is reflected so as to spread to, and then is reflected by the concave reflecting surface 18b. By using such a reflection member 18, the plurality of second light source units 17 are not provided, and only one second light source unit 17 is directed toward PBS 6 in the entire circumference of the peripheral portion away from the illumination optical axis XL. The illumination light Ls can be emitted.

The illumination light Ls reflected by the reflecting member 18 toward PBS 6 is provided in the peripheral portion of the illumination condensing lens 20 through the gaps outside the light source connecting portion 15a and the fixing portions 15b and 15c of the illumination substrate 15. It is incident on the lens part. As shown in FIG. 6B, the illumination substrate 15 is arranged so as to cover the central portion of the illumination condensing lens 20 in the vicinity of the illumination optical axis XL by the circular light source connection portion 15a. Therefore, even if the illumination light Ls reflected by the reflecting member 18 includes the light directed toward the central portion of the illumination condensing lens 20, the light is circularly blocked by the light source connecting portion 15a. In this way, the light source connecting portion 15a blocks the illumination light Ls reflected by the concave reflecting surface 18b of the reflecting member 18 toward the central portion near the illumination optical axis XL in PBS6, and the illumination light is more than the central portion in PBS6. It functions as a light-shielding member that allows light to pass from the axis XL toward the peripheral portion away from the peripheral side. In other words, the light source connecting portion 15a as a light-shielding member blocks light toward the central portion (first region) of the imaging region, which is near the center through which the imaging optical axis X passes, and is on the peripheral side of the central portion of the imaging region. Only the light directed toward the peripheral part (second region) of the light is passed.

Further, as shown in FIG. 6B, the fixed portions 15b and 15c of the illumination substrate 15 cover not only the central portion but also the peripheral portion of the illumination condensing lens 20. Therefore, of the illumination light Ls reflected toward the PBS 6 by the reflecting member 18, not only the light toward the central portion of the illumination condensing lens 20 but also the light toward the peripheral portion is blocked by the fixing portions 15b and 15c. The effect of shading the illumination light Ls by the fixed portions 15b and 15c will be described later.

The illumination light Ls that has passed through the lateral gap of the light source connection portion 15a and is incident on the illumination condensing lens 20 is angle-adjusted by the illumination condensing lens 20 and is incident on the peripheral portion on the PBS 6. As a result, as shown in FIG. 1 (b), only the illumination light Lm from the first light source unit 16 is incident on the central portion of the PBS 6, and the illumination light Lm and the second light source portion 17 are incident on the peripheral portion. The illumination light Ls of the above is superimposed and incident. Therefore, when the illumination light Lm of the first light source unit 16 has a uniform light amount distribution in the plane orthogonal to the illumination light axis XL, only the illumination light Lm from the first light source unit 16 is displayed on the PBS 6. The amount of illumination light is larger in the peripheral portion where the illumination lights Lm and Ls from the first and second light source portions 16 and 17 are superimposed than in the central portion where the light is incident.

As described above, according to the illumination unit 14 of the present embodiment, even if a large number of light source units are not used, the two light source units of the first and second light source units 16 and 17 are used in the peripheral portion from the central portion. The amount of illumination light can be increased. As a result, even if the illumination light reflected by PBS 6 and heading to the imaging region through the imaging optical system has a peripheral illumination drop due to the imaging optical system, the illumination light amount in the peripheral portion of the imaging region corrects the illumination light amount drop in the central portion. can do.

Here, the influence of shading of the illumination light Ls by the above-mentioned fixed portions 15b and 15c will be described. In order to fix the illumination substrate 15 to the fixing member 11, it is necessary to provide the fixing portions 15b and 15c in any direction (phase) from the light source connecting portion 15a around the illumination optical axis XL. In this case, since a part of the illumination light Ls reflected by the reflecting member 18 is blocked by the fixed portions 15b and 15c, the amount of illumination light in the peripheral portion in the region having the same phase as the fixed portions 15b and 15c in the peripheral portion of the PBS 6 is increased. I can't make it bigger.

However, as shown in FIG. 6B, the fixed portions 15b and 15c correspond to the imaging region around the illumination optical axis XL in the cross section provided with the illumination substrate 15 (the illumination light Ls reaching the imaging region). By providing the phase in the direction parallel to the short side of the rectangular region B (passing through), it is possible to minimize the influence of the light shielding of the illumination light Ls by the fixed portions 15b and 15c on the correction of the peripheral light falloff. In this embodiment, the cross section of FIG. 6B is a plane parallel to the imaging optical axis X, and the fixed portions 15b and 15c are provided in a phase in a direction parallel to the imaging optical axis X.

Peripheral light falloff due to the imaging optical system occurs more as the distance from the imaging optical axis X increases. Therefore, the peripheral light falloff in the imaging region is minimized by the shortest distance from the center of the imaging region (position on the imaging optical axis X) to the edge, which is parallel to the short side of the imaging region. The phase of the direction. Therefore, in this phase, it is least necessary to increase the amount of illumination light in the peripheral portion in order to correct the drop in the amount of peripheral light, as compared with other phases. Therefore, the fixed portions 15b and 15c are short of the rectangular region B when viewed from the center of the rectangular region B (illumination optical axis XL) corresponding to the imaging region in the cross section of FIG. 6B in which the illumination substrate 15 is arranged. By providing the fixtures so as to extend in the direction parallel to the sides, the influence of shading of the illumination light Ls by the fixing portions 15b and 15c can be minimized.

When the intersection C between the outer edge of the light source connecting portion 15a and the outer edges of the fixed portions 15b and 15c is on the short side (on the outer edge) of the rectangular region B or outside the rectangular region B as in this embodiment, imaging is performed. Since the inside of the rectangular region B corresponding to the region is not shielded by the fixed portions 15b and 15c themselves, the influence of the shielding by the fixed portions 15b and 15c does not substantially occur. Therefore, when the intersection C is in the rectangular region B and the influence of shading by the fixing portions 15b and 15c cannot be ignored, it is desirable to provide the fixing portions 15b and 15 in the above-mentioned phases. In this case, in the peripheral illumination correction processing described later, the correction amount of the gain of the image pickup signal with respect to the light receiving amount of the image pickup element 8 is shaded more than the other phases with respect to the phase provided with the fixed portions 15b and 15c. It is only necessary to increase the effect of.

Further, in this embodiment, the case where the illumination light emitted from the illumination unit 14 is reflected by the PBS 6 and heads toward the imaging optical system, and the imaging light passes through the PBS 6 and reaches the imaging element 8 is described. However, the positions of the illumination unit 14 and the image sensor 8 with respect to the PBS 6 are exchanged so that the illumination light passes through the PBS 6 and heads toward the image pickup optical system, and the image pickup light is reflected by the PBS 6 and reaches the image sensor 8. May be good. That is, the optical path separation element reflects one of the illumination light and the imaging light and transmits the other to direct the illumination light to the imaging optical system and direct the imaging light from the imaging optical system to the imaging element. It should be.

Further, in this embodiment, the case where the circular light source connecting portion 15a in the lighting substrate 15 is used as the light shielding member has been described, but the first and second light source portions 16 and 17 are arranged on the transparent lighting substrate and the first The second light source units 16 and 17 themselves may function as light-shielding members.

Next, the details of the correction of the peripheral light falloff by the illumination unit 14 will be described. The camera control unit 102 shown in FIG. 7 counts the number of drive pulses of the stepping motors 23 to 26 in zooming, focusing, and adjusting the amount of light in the direction of the image pickup optical axis of the zoom lens groups L2 and L3 and the focus lens group L4. The position of the lens and the aperture value of the aperture unit 13 are detected. In the following description, the positions of the zoom lens groups L2 and L3 and the focus lens group L4 and the aperture value of the aperture unit 13 are collectively referred to as a camera parameter which means a parameter of the imaging optical system.

The camera control unit 102 causes the first and second light source units 16 and 17 to emit light according to the instruction from the external terminal 200 described above, the brightness value information acquired from the image data, and the current value of the camera parameter, and is a subject. Let the lighting be done. Further, the camera control unit 102 as a correction means changes (corrects) the gain of the image pickup signal (hereinafter referred to as the image pickup gain) with respect to the light receiving amount of the image pickup element 8 with respect to the image data obtained by imaging the illuminated subject. The brightness of the image data is appropriately corrected by performing the peripheral illumination correction processing.

Here, the method of generating the peripheral light falloff by the imaging optical system changes according to the camera parameters. For example, in a state where the aperture diameter of the aperture unit 13 is narrowed down, as for the image pickup light incident on the image pickup optical system, only the light rays passing through a position closer to the image pickup optical axis X than when the aperture diameter is not narrowed down are concatenated on the image sensor 8. Because of the image, the difference in the amount of light received between the central portion and the peripheral portion on the image sensor 8, that is, the drop in the amount of peripheral light becomes small. Further, when the positions of the lens groups L2 to L4 in the optical axis direction change in the image pickup optical system, the angular range of the light rays passing through the peripheral portion in the image pickup optical system of the image pickup optical system changes with respect to the image pickup optical axis X, and the image pickup is performed. The difference in the amount of light received between the central portion and the peripheral portion of the element 8 changes.

Further, when illuminating the subject, the image pickup light first illuminates the subject through the image pickup optical system as illumination light, and then passes through the image pickup optical system twice to reach the image pickup element 8 through the image pickup optical system. Therefore, when the subject is not illuminated, it only passes through the imaging optical system once. Therefore, even if the camera parameters are the same, the magnitude of the peripheral illumination drop on the image sensor 8 differs depending on whether the subject is illuminated or not. In this way, the way in which the peripheral light amount is reduced by the imaging optical system changes depending on the camera parameters and the usage state (lighting / extinguishing) of the lighting unit 14.

However, the peripheral light falloff due to the imaging optical system can be calculated in the optical design, and it is possible to grasp in advance what kind of generation will occur. Therefore, due to the camera parameters and the usage state of the first light source unit 16, the second light source unit 17 should be turned on only when a large drop in peripheral illumination occurs and illumination of the peripheral portion of the imaging region is required. Just do it. As a result, the power consumption of the image pickup apparatus 1 can be suppressed.

Further, if the correction table is stored as a correction table for how to correct the image pickup gains of the central portion and the peripheral portion of the image sensor 8 according to the current camera parameters and the usage state of the illumination unit 14, the image pickup gain at the time of image pickup It is not necessary to calculate the correction amount of.

From the above, in the image pickup apparatus 1 of the present embodiment, the correction table storage unit 103 in the camera control unit 102 stores the correction amount of the image pickup gain according to the camera parameters and the usage state of the first light source unit 16. The corrected correction table is stored. The camera control unit 102 uses this correction table to perform peripheral illumination correction processing for correcting the imaging gain. At this time, if the camera parameter calculated in advance is set so that the peripheral light falloff cannot be sufficiently corrected only by correcting the imaging gain while the first light source unit 16 is lit, the camera control unit The 102 corrects the imaging gain after also turning on the second light source unit 17.

The flowchart of FIG. 8 shows the peripheral illumination correction process executed by the camera control unit 102 according to the computer program. In this embodiment, it is assumed that the pattern (correction pattern) of the correction table stored in the correction table storage unit 103 is divided into three different patterns according to the usage state of the first light source unit 16 and the camera parameters. In FIG. 8, S means a step.

First, in S1, the camera control unit 102 acquires the current value of the camera parameter.

Next, in S2, the camera control unit 102 confirms whether or not the first light source unit 16 is lit (ON), proceeds to S3 if it is turned off (OFF), and proceeds to S4 if it is ON. move on. In this embodiment, since the second light source unit 17 is used to increase the peripheral light amount of the illumination light, it is assumed that the second light source unit 17 is also OFF when the first light source unit 16 is OFF.

In S3, the camera control unit 102 corrects the imaging gain by using a correction pattern corresponding to the case where the illumination unit 14 does not illuminate the subject. When no illumination is performed, the peripheral light falloff due to the image pickup optical system occurs only for the amount of the image pickup light from the subject passing through the image pickup optical system once. Therefore, in S3, the center of the image pickup element 8 is corrected so as to correct this amount. Make the imaging gain of the peripheral part larger than that of the part.

On the other hand, in S4, the camera control unit 102 determines whether or not the camera parameter acquired in S1 is a camera parameter in which the peripheral light falloff due to the imaging optical system can be corrected only by correcting the imaging gain. Specifically, the result of calculating in advance whether or not the peripheral light falloff can be corrected for various camera parameters only by correcting the imaging gain is stored in the correction table storage unit 103 for each camera parameter, and in S1. Judgment is made by reading the result corresponding to the acquired camera parameter. In S4, the camera control unit 102 proceeds to S5 when the current camera parameter can correct the peripheral light falloff only by correcting the imaging gain, and proceeds to S6 when the correction is not possible.

In S5, the camera control unit 102 corrects the imaging gain with a correction pattern corresponding to the case where the subject is illuminated only by the first light source unit 16. In this case, the amount of peripheral light is reduced twice when the illumination light from the first light source unit 16 passes through the imaging optical system and when the imaging light from the subject passes through the imaging optical system. Therefore, a correction pattern is used that greatly increases the imaging gain of the peripheral portion of the image pickup device 8 as compared with the correction pattern used when no illumination is performed in S3.

Further, in S6, the camera control unit 102 lights the second light source unit 17. As a result, the amount of the image pickup light that reaches the peripheral portion of the image pickup element 8 before the image pickup gain is corrected increases.

Then, in S7, the camera control unit 102 raises the image gain of the peripheral portion of the image sensor 8 by using a correction pattern corresponding to the case where the first and second light source units 16 and 17 are used to illuminate the subject.

A specific example of the correction of the peripheral illumination amount drop (correction of the imaging gain) in this embodiment will be described with reference to FIGS. 9 (a) to 9 (d) and FIGS. 10 (a) to 10 (d). The horizontal axis of each figure indicates the image height position. The 0% image height position indicates the center position on the illumination optical axis XL or the imaging optical axis X, and the closer to 100%, the farther away from each optical axis. The vertical axis of each figure shows the ratio of the amount of light at each image height position or the ratio of the amount of correction of the imaging gain when the value at the center position is 1. Further, in each figure, the solid line indicates the ratio of the amount of light or the amount of correction when no illumination is performed (when the illumination is OFF), and the one-point chain line indicates the case where only the first light source unit 16 is lit for illumination (first light source). The light amount ratio or the correction amount ratio when the unit is ON), and the light amount when the two-point chain line lights the first and second light source units 16 and 17 to illuminate (when the first + second light source unit is ON). The ratio or the ratio of the correction amount is shown respectively.

FIG. 9A shows the light intensity ratio of the illumination light Lm for each image height position on the PBS 6 when the illumination is OFF and when the first light source unit is ON. The light intensity ratio (solid line) is 0 when the illumination is off, and the light intensity ratio (dotted chain line) when the first light source unit is ON is uniform over the entire image height position.

FIG. 9B shows the light intensity ratio of the image pickup light for each image height position from the image pickup optical axis X on the image pickup element 8 when the illumination is OFF and when the first light source unit is ON. Before the imaging gain is corrected, image data (image data before correction) having a brightness ratio corresponding to the light amount ratio of the imaging light shown in FIG. 9B can be obtained. FIG. 9C shows the ratio of the correction amount of the imaging gain for each image height position on the image sensor 8 when the illumination is turned off and when the first light source unit is turned on. The correction amount corresponding to the ratio when the illumination is OFF is stored in the correction table used in S3, and the correction amount corresponding to the ratio when the first light source unit is ON is stored in the correction table used in S5. The threshold value in the figure indicates the ratio of the maximum correction amount that does not affect the image quality of the image data after the correction of the imaging gain.

As shown in FIG. 9B, due to the difference in the number of times (1 time and 2 times) the image pickup light passes through the image pickup optical system, the first light source unit is turned on as compared with the light amount ratio of the image pickup light when the illumination is off. The light intensity ratio of the imaged light at time becomes low in the peripheral portion. Therefore, as shown in FIG. 9C, the ratio of the correction amount of the imaging gain when the first light source unit is ON is higher in the peripheral portion than the ratio of the correction amount of the imaging gain when the illumination is OFF.

FIG. 9D shows the light amount (luminance) ratio for each image height position on the image data after the image gain is corrected (peripheral light amount correction) when the illumination is turned off and when the first light source unit is turned on. By correcting the image gain at the ratio of the correction amount shown in FIG. 9 (c) when the illumination is OFF and when the first light source unit is ON, the brightness of the peripheral portion is corrected to be at the same level. Image data can be obtained.

FIG. 10A shows the light intensity ratio of the illumination light Lm + Ls for each image height position on the PBS 6 when the first + second light source units are ON. When the first + second light source unit is ON, the illumination light Lm when the first light source unit is ON shown in FIG. 9A is the illumination light when only the second light source unit 17 shown by the broken line is turned on. Since Ls is added, the light amount ratio in the peripheral portion becomes higher than when the first light source portion is ON.

FIG. 10B shows the light intensity ratio of the image pickup light for each image height position on the image pickup device 8 when the first light source unit is ON and when the first + second light source unit is ON. FIG. 10C shows the ratio of the correction amount of the imaging gain for each image height position when the first light source unit is ON and when the first + second light source unit is ON. FIG. 10B shows a case where the light amount ratio of the imaging light in the peripheral portion is too low only by lighting the first light source unit 16 and the peripheral light amount drop cannot be sufficiently corrected only by correcting the imaging gain. That is, the case where the ratio of the correction amount shown in FIG. 10C exceeds the above-mentioned threshold value is shown.

As shown in FIG. 10B, when the first + 2 light source unit is ON, the light intensity ratio of the imaged light in the peripheral portion is higher than when the first light source unit is ON. Therefore, as shown in FIG. 10C, the ratio of the correction amount of the imaging gain when the first light source unit is ON is compared with the ratio of the correction amount of the imaging gain when the first light source unit is ON. It can be lowered in the peripheral area (however, it is higher than when the lighting is off). Therefore, the ratio of the correction amount that does not exceed the threshold value can be set. The correction amount corresponding to the ratio when the first + second light source unit is ON is stored in the correction table used in S7.

FIG. 10D shows the light amount ratio for each image height position on the image data after correction of the imaging gain when the first light source unit is ON and when the first + second light source unit is ON. In the corrected image data when the first light source unit is ON, the peripheral portion is too dark due to insufficient correction. On the other hand, when the first + second light source units are ON, image data in which the brightness of the peripheral portion is sufficiently corrected can be obtained.

As described above, in the image pickup apparatus 1 of the present embodiment, the correction pattern for the image pickup gain is determined according to the camera parameters and the usage state of the illumination unit 14 (illumination OFF, first light source unit ON and first + second light source unit ON). By changing, the brightness of the image data can be appropriately corrected.

Example 2 of the present invention will be described with reference to FIGS. 11A and 11B. In the first embodiment, the case where the reflection member 18 having a rotationally symmetric shape centered on the illumination optical axis XL has been described. However, if it is not necessary to correct the peripheral light falloff with the same size in all the peripheral portions of the imaging region. The reflecting member does not necessarily have to have a rotationally symmetric shape centered on the illumination optical axis XL. For example, in a rectangular imaging region, when it is desired to increase the amount of illumination light in the diagonal peripheral portion where the distance from the center is the maximum and the peripheral light falloff is large, the illumination light should be concentrated in the peripheral portion. It is possible to use a reflective member that does not have a rotationally symmetric shape.

Similar to the reflection member 18, the reflection member 27 shown in FIGS. 11A and 11B has a convex reflection surface (second light source portion side) projecting to the inner surface side (second light source portion side) in the central portion near the illumination optical axis XL. 1 has a reflective surface) 27a. However, the reflective member 27 has a reflective surface 27b at a peripheral portion away from the illumination optical axis XL, and the convex reflective surface (second reflective surface) 27c protruding inward at a plurality of locations of the reflective surface 27b. , 27d are formed. As described above, the reflecting member 27 does not have a rotationally symmetric shape centered on the illumination optical axis XL.

By using the reflecting member 27, the illumination light reflected from the convex reflecting surface 27a in the direction of the peripheral reflecting surface 27b is reflected by the convex reflecting surfaces 27c and 27d in the diagonal direction of the imaging region (FIG. 11B). The light can be focused on the peripheral part (the direction corresponding to the alternate long and short dash line crossed by). By using the non-rotationally symmetrical reflective member in this way, it is possible to illuminate a specific peripheral portion of the imaging region brighter than the other peripheral portions.

Although the reflecting members 18 and 27 of the first embodiment and the reflecting members 18 and 27 of the present embodiment are both integrally reflecting members having a cup-shaped shape, the illumination light from the second light source unit 17 is guided to the peripheral portion of the imaging region. If possible, it may have another shape such as a plate shape, or a plurality of reflective members may be used.

Example 3 of the present invention will be described with reference to FIG. The illumination condensing lens 20 in the first embodiment has a lens unit only in a portion where the illumination light from the second light source unit 17 is incident, but a lens that condenses the illumination light from the first light source unit 16 It may be necessary. In such a case, an illumination condensing lens for illumination light from the first light source unit 16 may be provided separately from the illumination condensing lens 20, but as shown in FIG. 12, one is the first. An illumination condensing lens 28 that condenses the illumination light from the light source unit 16 and the illumination light from the second light source unit 17 may be provided.

The illumination condensing lens 28 is provided in the central portion near the illumination optical axis XL and is located in the first lens portion 28a where the illumination light from the first light source portion 16 is incident and in the peripheral portion away from the illumination optical axis XL. It has a second lens portion 28b to which the illumination light from the second light source portion 17 provided and reflected by the reflecting member 18 is incident. The first lens portion 28a and the second lens portion 28b have different shapes (curvatures) from each other. Further, the first lens portion 28a has a hemispherical shape that covers the first light source portion 16.

With such one illumination condensing lens 28, the illumination light from the first and second light source units 16 and 17 can be individually condensed.
(Other Examples)
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

Each of the above-described examples is only a representative example, and various modifications and changes can be made to each of the examples in carrying out the present invention.

1 Imaging device L2, L3 Zoom lens group L4 Focus lens group 6 Polarized beam splitter 8 Imaging element 13 Aperture unit 15 Lighting substrate 16 First light source unit 17 Second light source unit 18 Reflecting member

Claims (9)

An image sensor that captures the imaging light incident on the imaging optical system from the imaging region, and
An illumination unit that emits illumination light that irradiates the imaging region through the imaging optical system, and
By reflecting one of the illumination light and the imaging light and transmitting the other, the illumination light is directed to the imaging optical system, and the imaging light from the imaging optical system is directed to the imaging element. Has a separating element
The lighting unit
A first light source unit that emits a first illumination light toward the optical path separation element, and
A second light source unit that emits a second illumination light in a direction opposite to that of the first light source unit,
An image pickup apparatus comprising: a reflecting member that reflects the second illumination light toward the optical path separating element through the periphery of the first and second light source portions. A light-shielding member that blocks light from the second illumination light reflected by the reflecting member toward the first region in the imaging region and passes light toward a second region on the peripheral side of the first region. The imaging apparatus according to claim 1, wherein the image pickup apparatus has. The light-shielding member is a substrate on which the first light source portion is arranged on the first surface on the optical path separation element side and the second light source portion is arranged on the surface opposite to the first surface. The imaging device according to claim 2, wherein the image pickup device is provided. The substrate is
A light source connection portion having the first surface and the second surface,
It has a fixing portion fixed to the fixing member of the image pickup apparatus, and has a fixing portion.
Of the second illumination light, the light directed to the first region is blocked by the light source connection portion.
The imaging device according to claim 3, wherein the fixing portion is provided on or outside the outer edge of the region corresponding to the imaging region in the plane on which the substrate is provided. The substrate is
A light source connection portion having the first surface and the second surface,
It has a fixing portion fixed to the fixing member of the image pickup apparatus, and has a fixing portion.
Of the second illumination light, the light directed to the first region is blocked by the light source connection portion.
A part of the second illumination light toward the second region is blocked by the fixing portion.
The fixing portion is provided so as to extend in a direction parallel to the short side of the rectangular region when viewed from the center of the rectangular region corresponding to the imaging region in the plane on which the substrate is provided. The imaging device according to claim 3. The reflective member has a first reflective surface and a second reflective surface provided on the peripheral side of the first reflective surface.
The second illumination light from the second light source is reflected by the first reflecting surface toward the second reflecting surface and reflected by the second reflecting surface toward the optical path separating element. The imaging apparatus according to any one of claims 1 to 5, wherein the image pickup apparatus is characterized by the above. The imaging apparatus according to any one of claims 1 to 6, further comprising an optical member having a lens portion through which the second illumination light reflected by the reflecting member is transmitted. The seventh aspect of claim 7, wherein the optical member has a shape different from that of the lens portion through which the second illumination light is transmitted, and further has a lens portion through which the first illumination light is transmitted. Imaging device. It has a correction means for performing correction processing for correcting the brightness of the peripheral portion of the image data generated by using the output from the image sensor.
Any of claims 1 to 8, wherein the correction means performs the correction process using the parameters of the imaging optical system and the correction amount according to the usage state of the first and second light source units. The imaging apparatus according to paragraph 1.

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