JP2020159791A - Imaging apparatus and method for determination - Google Patents

Abstract

To detect whether a polarization sunglass is being used or not.SOLUTION: An imaging apparatus 10 includes: a camera 22; an illumination device for selectively emitting a first illumination light 12s linearly polarized in a first direction and a second illumination light 12p linearly polarized in a second direction perpendicular to the first direction to an imaging target of the camera 22; an image acquisition unit for acquiring, from the camera 22, a first image including the imaging target irradiated with the first illumination light 12s and a second image including the imaging target irradiated with the second illumination light 12p; and an image processing unit for determining whether the imaging target includes a linear polarizer on the basis of the first image and the second image.SELECTED DRAWING: Figure 1

Description

The present invention relates to an imaging device and a determination method.

In recent years, a head-up display has been used in which an image display light is projected onto a windshield of a vehicle or the like, and a virtual image based on the image display light is superimposed on a landscape outside the vehicle. A user such as a driver visually recognizes the image display light reflected by the windshield. It is known that the reflectance of a general windshield made of glass or the like has polarization dependence, and the P polarization component is less likely to be reflected than the S polarization component. When the user is using polarized sunglasses, the S polarized light component that is easily reflected by the windshield is shielded by the polarized sunglasses, which makes it difficult to see the image display light. A display device has been proposed in which the image display light is easily visible even when polarized sunglasses are used (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-57897

If the P-polarized light component, which is hard to be reflected by the windshield, is mainly used, the image display light becomes dark for the user who does not use the polarized sunglasses. In order to provide appropriate image display light depending on whether or not polarized sunglasses are used, it is preferable to be able to detect the presence or absence of polarized sunglasses.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for detecting the presence or absence of the use of polarized sunglasses.

The image pickup apparatus of an aspect of the present invention captures a camera, a first illumination light linearly polarized in the first direction, and a second illumination light linearly polarized in a second direction orthogonal to the first direction. A lighting device capable of selectively irradiating an object, a first image including an imaged object irradiated with the first illumination light, and a second image including an imaged object irradiated with the second illumination light are captured from a camera. The image acquisition unit to be acquired and an image processing unit for determining whether or not the imaging target includes a linear polarizer based on the first image and the second image are provided.

Another aspect of the present invention is a determination method. In this method, the first image of the imaged object irradiated with the first illumination light linearly polarized in the first direction and the second illumination light linearly polarized in the second direction orthogonal to the first direction are irradiated. It is determined whether or not the imaging target includes a linear polarizer based on the second image obtained by imaging the imaging target.

It should be noted that any combination of the above components or components and expressions of the present invention that are mutually replaced between methods, devices, systems, and the like are also effective as aspects of the present invention.

According to the present invention, it is possible to provide a technique for detecting the presence or absence of use of polarized sunglasses.

It is a figure which shows typically the installation example of the image pickup apparatus which concerns on embodiment. It is a graph which shows the reflectance of a windshield. It is a figure which shows typically the determination method of polarized sunglasses. It is a figure which shows typically the structure of the image pickup apparatus which concerns on embodiment. It is a figure which shows typically the structure of the lighting apparatus which concerns on embodiment. It is a block diagram which shows typically the functional structure of the control device which concerns on embodiment. It is a timing chart which shows operation of a lighting apparatus and a camera schematically. 8 (a) and 8 (b) are diagrams schematically showing the configuration of the lighting device according to the modified example. 9 (a) and 9 (b) are diagrams schematically showing the configuration of the lighting device according to another modified example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The specific numerical values and the like shown in such an embodiment are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are designated by the same reference numerals to omit duplicate description, and elements not directly related to the present invention are not shown. To do.

FIG. 1 is a diagram schematically showing an installation example of the image pickup apparatus 10 according to the embodiment. In the present embodiment, the image pickup device 10 and the virtual image display device 50 are installed in the vehicle 60, which is an example of the moving body. The image pickup device 10 is a so-called driver monitor, and images the face of the driver 70 of the vehicle 60 to monitor the state of the driver 70. The virtual image display device 50 is a so-called head-up display, and projects an image display light 52 on the windshield 62 to present the virtual image 54 in front of the vehicle 60 in the traveling direction (right direction in FIG. 1). The driver 70 visually recognizes the virtual image 54 superimposed on the real landscape through the windshield 62. In FIG. 1, the traveling direction (front-rear direction) of the vehicle 60 is the z direction, the top-bottom direction (vertical direction) of the vehicle 60 is the y direction, and the left-right direction of the vehicle 60 is the x direction.

The imaging device 10 according to the present embodiment is configured to be able to determine whether or not the sunglasses 72 used by the driver 70 are polarized sunglasses. Here, the polarized sunglasses are sunglasses capable of shielding or reducing the reflected light on the water surface, and include a linear polarizer that shields or reduces the S-polarizing component and transmits the P-polarizing component. On the other hand, ordinary sunglasses do not contain a linear polarizer and include an ND (Neutral Density) filter that attenuates the intensity of incident light. The background that requires the detection of polarized sunglasses is the polarization dependence of the reflectance of the image display light 52 in the windshield 62.

FIG. 2 is a graph showing the reflectance of the windshield 62. It is known that the reflectance of a general windshield 62 made of glass or the like has polarization dependence, and the reflectance Rp of the P polarization component is lower than the reflectance Rs of the S polarization component. Therefore, among the image display lights 52 shown in FIG. 1, the reflectance of the first display light 52s of the S polarization component is relatively high, and the reflectance of the second display light 52p of the P polarization component is relatively low. In particular, at an incident angle (for example, 53 degrees) called Brewster's angle θ _B , the reflectance Rp of the P-polarized light component becomes 0. As shown in FIG. 1, the image display light 52 projected from the virtual image display device 50 is obliquely input-reflected with respect to the windshield 62, and the input / reflection angle φ at the windshield 62 is the Brewster angle θ _B. Can take close values. As a result, the first display light 52s of the S polarization component easily reaches the eyes of the driver 70, and the second display light 52p of the P polarization component does not easily reach the eyes of the driver 70.

At this time, if the driver 70 is using polarized sunglasses, the first display light 52s of the S polarization component is shielded or reduced by the polarized sunglasses. As a result, in order for the driver 70 to visually recognize the image display light 52, the second display light 52p of the P polarization component must be used. On the other hand, when the driver 70 does not use polarized sunglasses, it is possible to provide a brighter and more visible virtual image 54 by using the first display light 52s of the S polarization component. Therefore, in the present embodiment, it is possible to automatically determine whether or not polarized sunglasses are used, and to provide an image display light 52 having a more appropriate polarized component depending on whether or not polarized sunglasses are used.

The S-polarized light component in the configuration of FIG. 1 is a light component linearly polarized in the first direction orthogonal to both the incident direction and the reflected direction of the image display light 52 in the windshield 62, and is the left-right direction of the vehicle 60 ( It corresponds to a light component linearly polarized in the x direction). On the other hand, the P polarization component is a light component linearly polarized in the second direction orthogonal to the first direction, and is along the yz plane defined in the vertical direction (y direction) and the front-rear direction (z direction) of the vehicle 60. It corresponds to a light component linearly polarized in the direction.

In FIG. 1, the image pickup apparatus 10 is configured to irradiate the illumination light 12 toward the face of the driver 70 to be imaged. The image pickup apparatus 10 selects the first illumination light 12s of the S-polarized component linearly polarized in the first direction and the second illumination light 12p of the P-polarized component linearly polarized in the second direction toward the driver 70. It is configured to irradiate the target. The image pickup apparatus 10 acquires a first image of the driver 70 irradiated with the first illumination light 12s and a second image of the driver 70 irradiated with the second illumination light 12p. The image pickup apparatus 10 determines whether or not the driver 70 is using polarized sunglasses by comparing the first image and the second image.

FIG. 3 is a diagram schematically showing a method for determining polarized sunglasses. In FIG. 3, the image is acquired by the image pickup apparatus 10 in three cases: (a) when the naked eye is not using sunglasses, (b) when using normal sunglasses which are not polarized sunglasses, and (c) when using polarized sunglasses. (I) The first image and (ii) the second image are shown. FIG. 3 also shows histograms of the (iii) difference image and the (iv) difference image corresponding to the difference between the first image and the second image. Here, the "difference image" refers to the luminance value (also referred to as the second luminance value) of each pixel constituting the second image from the luminance value (also referred to as the first luminance value) of each pixel constituting the first image. It is an image in which the brightness value of each pixel is composed of the subtracted difference value (= first brightness value − second brightness value). The histogram is a graph of the distribution of the brightness values of each pixel constituting the image, and is represented by a graph in which the horizontal axis is the brightness value and the vertical axis is the number of pixels.

In the case of the naked eye of (a), since the first image of the S-polarized illumination and the second image of the P-polarized illumination are almost the same, the brightness value of the difference image (that is, the difference value between the first brightness value and the second brightness value). ) Becomes almost zero, and almost nothing appears in the difference image. As a result, in the histogram of the difference image, the peak 74 is detected only in the vicinity where the luminance value becomes zero. The same applies when using the normal sunglasses of (b), and since the first image of the S-polarized illumination and the second image of the P-polarized illumination are almost the same, almost nothing is reflected in the difference image, and the difference image Also in the histogram, the peak 74 is detected only in the vicinity where the brightness value becomes zero. When the polarized sunglasses of (c) are used, the appearance of the polarized sunglasses differs between the first image of the S-polarized illumination and the second image of the P-polarized illumination. Since the polarized sunglasses shield the S-polarized component, the polarized sunglasses appear black in the first image of the S-polarized illumination. On the other hand, since polarized sunglasses transmit the P-polarized component, the polarized sunglasses can be seen through in the second image of P-polarized illumination. As a result, in the difference image, the absolute value of the brightness value in the region of the polarized sunglasses (that is, the difference value between the first brightness value and the second brightness value) becomes large, and the polarized sunglasses appear to be emphasized. Since the first luminance value of the polarized sunglasses region in the first image is relatively small (that is, dark) and the second luminance value of the polarized sunglasses region in the second image is relatively large (that is, bright), in the difference image. The brightness value in the polarized sunglasses region is a negative value (for example, −n). As a result, in the histogram of the difference image, the first peak 74a is detected in the vicinity where the luminance value becomes zero, and the second peak 74b is detected in the vicinity where the luminance value becomes −n. In this way, by comparing the first image of the S-polarized illumination and the second image of the P-polarized illumination, the presence or absence of the polarized sunglasses can be detected.

FIG. 4 is a diagram schematically showing the configuration of the image pickup apparatus 10 according to the embodiment. The image pickup device 10 includes a lighting device 20, a camera 22, and a control device 24. The camera 22 targets the driver 70 in front of the image pickup shaft 16. The lighting device 20 irradiates the illumination light 12 toward the driver 70 in front of the illumination shaft 14. The control device 24 controls the operations of the camera 22 and the lighting device 20. In the illustrated example, the illumination axis 14 and the image pickup axis 16 are drawn so as to be parallel, but the illumination axis 14 and the image pickup axis 16 do not necessarily have to be parallel.

FIG. 5 is a diagram schematically showing the configuration of the lighting device 20 according to the embodiment. The lighting device 20 includes a first light source 30s, a second light source 30p, a drive circuit 32, a combiner element 34, a projection lens 36, and a light diffusing plate 38.

The first light source 30s generates S-polarized first illumination light 12s linearly polarized in the first direction, and the second light source 30p generates P-polarized second illumination light 12p linearly polarized in the second direction. To do. The first light source 30s and the second light source 30p are, for example, laser light sources having an oscillation mode of linearly polarized light, and are arranged so that the polarization directions differ from each other by 90 degrees. The first light source 30s and the second light source 30p are configured to output, for example, an infrared laser. The first light source 30s and the second light source 30p may output a visible light laser, or may output a red, green, or blue laser light. Each of the first light source 30s and the second light source 30p is driven by the drive circuit 32, and the lighting timing and the extinguishing timing are controlled.

The combiner element 34 is arranged on the illumination shaft 14, and the first illumination light 12s emitted from the first light source 30s and the second illumination light 12p emitted from the second light source 30p are combined on the illumination shaft 14. Wave. An example of the combiner element 34 is a polarization beam splitter, which transmits the first illumination light 12s and reflects the second illumination light 12p to combine the two.

The projection lens 36 is arranged on the illumination shaft 14 and projects the illumination light 12 combined by the combine element 34 toward the illumination target. The light diffusing plate 38 is arranged on the illumination shaft 14 and is configured to diffuse and homogenize the illumination light 12 transmitted through the projection lens 36. The light diffusing plate 38 is preferably a polarization preserving type in which the polarization direction is preserved before and after the incident of the light diffusing plate 38.

FIG. 6 is a block diagram schematically showing a functional configuration of the control device 24 according to the embodiment. The control device 24 includes a lighting control unit 40, an image pickup control unit 42, an image acquisition unit 44, an image processing unit 46, and an output unit 48. Each functional block shown in the figure can be realized by elements and mechanical devices such as the CPU and memory of a computer in terms of hardware, and by a computer program or the like in terms of software, but here, by linking them. It is drawn as a functional block to be realized. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by combining hardware and software.

The lighting control unit 40 controls the operation of the lighting device 20 to switch the operation mode of the lighting device 20. The illumination device 20 has a first illumination mode in which only the first light source 30s is turned on to generate the first illumination light 12s, and a second illumination mode in which only the second light source 30p is turned on to generate the second illumination light 12p. It has a third illumination mode in which both the first light source 30s and the second light source 30p are turned on to generate unpolarized illumination light 12. The lighting control unit 40 switches between the first lighting mode, the second lighting mode, and the third lighting mode by controlling the operation of the drive circuit 32.

The image pickup control unit 42 controls the operation of the camera 22 in synchronization with the operation of the lighting device 20. The image pickup control unit 42 causes the camera 22 to take a first image at the timing when the first illumination light 12s is applied to the image pickup target. The image pickup control unit 42 causes the camera 22 to take a second image at the timing when the image pickup target is irradiated with the second illumination light 12p. The image pickup control unit 42 causes the camera 22 to take a third image at the timing when the unpolarized illumination light 12 is applied to the image pickup target. Here, the third image is an image when the image pickup device 10 is operated as a driver monitor to image the driver 70, and is, for example, an image constituting a moving image.

FIG. 7 is a timing chart schematically showing the operations of the lighting device 20 and the camera 22. The first period T1 is a first illumination mode in which only the first light source 30s is turned on to generate the first illumination light 12s. The second period T2 is a second illumination mode in which only the second light source 30p is turned on to generate the second illumination light 12p. The third period T3 is a third illumination mode in which both the first light source 30s and the second light source 30p are turned on to generate unpolarized illumination light 12. The camera 22 captures a first image in the first period T1, a second image in the second period T2, and a third image (moving image) in the third period T3.

The lighting control unit 40 periodically switches between the first period T1, the second period T2, and the third period T3 to enable acquisition of the first image and the second image for detecting polarized sunglasses, and at the same time, It enables the acquisition of a third image (moving image) for the driver monitor. For example, the illumination control unit 40 switches the illumination mode in synchronization with the frame rate of the camera 22, sets the first illumination mode in the first frame, sets the second illumination mode in the second frame, and sets the second illumination mode in the third and subsequent frames. 3 Lighting mode. Therefore, it can be said that the lighting control unit 40 sets the basic lighting mode as the third lighting mode and intermittently inserts the first lighting mode and the second lighting mode. The cycle for switching to the first lighting mode and the second lighting mode is not particularly limited, but is, for example, 1 second, 5 seconds, 10 seconds, 30 seconds, 1 minute, 5 minutes, and the like. Further, the lighting control unit 40 switches between the first lighting mode and the second lighting mode between adjacent frames of the camera 22. This minimizes the change in the imaging target between the acquisition timings of the first image and the second image, and prevents the difference between the first image and the second image due to factors other than polarization.

Returning to FIG. 6, the image acquisition unit 44 acquires an image captured by the camera 22. The image acquisition unit 44 acquires a first image captured in the first illumination mode and a second image captured in the second illumination mode. The image acquisition unit 44 may acquire a third image (moving image) to be captured in the third illumination mode.

The image processing unit 46 determines whether or not polarized sunglasses are included in the imaging target based on the first image and the second image acquired by the image acquisition unit 44. As shown in FIG. 3, the image processing unit 46 generates a difference image between the first image and the second image, and the difference image has a “specific area” in which the absolute value of the brightness value of each pixel is equal to or greater than the reference value. Determined to include polarized sunglasses if present. As shown in FIG. 3, the image processing unit 46 may determine the presence or absence of polarized sunglasses based on the histogram of the difference image. For example, in the histogram of FIG. 3, a peak in which the number of pixels on the vertical axis is equal to or greater than a predetermined value at a position where the absolute value of the brightness value on the horizontal axis is equal to or greater than the reference value (for example, the luminance value −n) (for example, the second peak 74b). Is included to determine that there are polarized sunglasses.

The image processing unit 46 may determine whether or not polarized sunglasses are included in consideration of the sign (positive or negative) of the brightness value of the pixel in the specific region in the difference image. For example, the brightness value of the pixel in the specific region of the first image using S-polarized illumination is relatively small (that is, dark), and the brightness value of the pixel in the specific region of the second image using P-polarized illumination is relatively large. It may be determined that polarized sunglasses are included only if they are (ie, bright). The image processing unit 46 identifies the contour of the driver 70's face and the position of the eyes by using an image analysis technique such as pattern matching, and when a specific area exists in a range overlapping the face or a specific area is located at the eye position. You may determine that you are using polarized sunglasses if they are present. The image processing unit 46 may determine whether or not polarized sunglasses are used only when the driver 70 does not tilt his head and the left-right direction of the vehicle 60 matches the left-right direction of both eyes of the driver 70 or the left-right direction of the sunglasses. ..

The image processing unit 46 may evaluate the state of the driver 70 based on the third image (moving image) acquired by the image acquisition unit 44. The image processing unit 46 detects dozing when the driver 70's eyes are closed continuously for a predetermined time, and the line-of-sight direction of the driver 70 is continuously directed to a direction different from the front of the vehicle for a predetermined time. In some cases, inattentive driving may be detected.

The output unit 48 outputs the determination result by the image processing unit 46 to the external device. The output unit 48 outputs, for example, a signal indicating a determination result of whether or not polarized sunglasses are used to the virtual image display device 50. The output unit 48 may output a signal relating to the state or state change of the driver 70 to any device mounted on the vehicle 60, or may output the image data acquired by the image acquisition unit 44.

According to this embodiment, it is possible to automatically determine whether or not the driver 70 is using polarized sunglasses by using the imaging device 10. As a result, the virtual image display device 50 can generate an appropriate image display light 52 depending on whether or not polarized sunglasses are used. For example, when polarized sunglasses are not used, the windshield 62 generates S-polarized first display light 52s which is easily reflected, and when polarized sunglasses are used, it is visible through polarized sunglasses. It is possible to generate a second display light 52p of P-polarized light. As a result, the power consumption of the virtual image display device 50 can be reduced as compared with the case where both the first display light 52s and the second display light 52p are generated regardless of whether or not the polarized sunglasses are used. Further, since it is not necessary to simultaneously turn on a plurality of light sources in order to generate both the first display light 52s and the second display light 52p, it is possible to prevent the operating temperature from rising due to the simultaneous lighting of the plurality of light sources, and the light source Can achieve a longer life.

According to this embodiment, it is possible to automatically determine whether or not the driver 70 is using polarized sunglasses while using the image pickup device 10 as a driver monitor. By intermittently switching the operation mode of the lighting device 20 to the first lighting mode and the second lighting mode, the polarized sunglasses can be obtained without substantially affecting the acquisition of the third image (moving image) as the driver monitor. The first image and the second image used for the determination can be acquired. Further, in the third illumination mode for acquiring the third image (moving image) as the driver monitor, the face of the driver 70 is further radiated by irradiating both the first illumination light 12s and the second illumination light 12p. Can be illuminated brightly. As a result, a clearer image of the driver 70 can be captured, and the determination accuracy as a driver monitor can be improved.

8 (a) and 8 (b) are diagrams schematically showing the configuration of the lighting device 120 according to the modified example. In this modification, the lighting device 20 according to the above-described embodiment is generated in that the first illumination light 112s and the second illumination light 112p are generated by using an unpolarized light source 130 such as an LED (Light Emitting Diode). It's different.

As shown in FIG. 8A, the illuminating device 120 includes a light source 130 and a polarization switching mechanism 132. The light source 130 produces unpolarized or randomly polarized illumination light 112, and produces illumination light 112 containing at least two linearly polarized components orthogonal to each other. The light source 130 and the polarization switching mechanism 132 are arranged on the illumination shaft 114 of the illumination device 120. The polarization switching mechanism 132 includes a polarization filter 134 and a motor 136.

As shown in FIG. 8B, the polarizing filter 134 has a disk shape, and the first region 134a, the second region 134b, and the third region 134c are provided at different positions in the circumferential direction. The first region 134a and the second region 134b are provided with linear polarizers, while the third region 134c is not provided with a polarizer. The first region 134a and the second region 134b are provided with linear polarizing elements having the same orientation of the polarization axis A. The motor 136 rotates the polarizing filter 134 in the R direction to switch the regions 134a to 134c of the polarizing filter 134 arranged on the illumination shaft 114. The motor 136 is a drive unit that displaces the linear polarizer provided in the polarizing filter 134 with respect to the illumination shaft 114.

By rotating the polarizing filter 134, the motor 136 changes the direction of the polarizing axis A of the linear polarizer and aligns it with the orientation of the polarizing axis A that transmits the S polarizing component or the P polarizing component. In the state shown in FIG. 8B, since the direction of the polarizing axis A of the linear polarizing element is the left-right direction, the polarizing filter 134 functions as a first linear polarizer that transmits the S polarization component. Therefore, when the first region 134a is arranged on the illumination shaft 114, only the S polarization component is transmitted through the polarizing filter 134 that functions as the first linear polarizer, and the first illumination light 112s that is S-polarized illumination is generated. To. On the other hand, when the second region 134b is arranged on the illumination axis 114, that is, when the polarizing filter 134 is rotated 90 degrees from the state of FIG. 8B, the direction of the polarizing axis A of the linear polarizer is in the vertical direction. Therefore, the polarizing filter 134 functions as a second linear polarizer that transmits the P polarization component. As a result, when the second region 134b is arranged on the illumination shaft 114, only the P-polarizing component is transmitted through the polarizing filter 134 that functions as the second linear polarizing element, and the second illumination light 112p that is P-polarized illumination is generated. Will be done. When the third region 134c is arranged on the illumination shaft 114, that is, when the linear polarizer is not inserted on the illumination shaft 114, the unpolarized illumination light passes through the polarizing filter 134 as it is, so that the unpolarized illumination light is transmitted. 112 is generated. In this way, the polarization switching mechanism 132 is configured to switch the polarization state of the illumination light 112 projected from the illumination device 120.

The operation of the lighting device 120 is controlled by, for example, the lighting control unit 40 described above. The illumination control unit 40 controls the operation of the motor 136, and has a first illumination mode in which the first region 134a is arranged on the illumination shaft 114 and a second illumination mode in which the second region 134b is arranged on the illumination shaft 114. And the third illumination mode in which the third region 134c is arranged on the illumination shaft 114. The motor 136 may be configured as a stepping motor, or may be configured to instantaneously switch between the illumination modes by instantaneously rotating the polarizing filter 134 by a predetermined angle. The motor 136 may be configured to maintain each illumination mode for a certain period of time by keeping the polarizing filter 134 stationary in each illumination mode without rotating it. Even when the lighting device 120 according to this modification is used, the same effect as that of the above-described embodiment can be obtained.

In a further modification, the polarization axes A of the linearly polarized lighters provided in the first region 134a and the second region 134b do not have to be common, and the first linearly polarizer that transmits the S polarization component through the first region 134a A second linear polarizer may be provided so as to transmit the P polarization component in the second region 134b. Further, the range occupied by each region 134a to 134c of the polarizing filter 134 is not limited to that shown, and at least one of each region 134a to 134c may occupy a wider range than the shown region, and is shown. It may occupy a smaller area than the area.

9 (a) and 9 (b) are diagrams schematically showing the configuration of the lighting device 220 according to another modified example. This modification differs from the above modification in that the polarizing filter is configured to slide instead of rotating.

As shown in FIG. 9A, the illuminating device 220 includes a light source 230 and a polarization switching mechanism 232. The light source 230 produces unpolarized or randomly polarized illumination light 212, and produces illumination light 212 containing at least two linearly polarized components orthogonal to each other. The light source 230 and the polarization switching mechanism 232 are arranged on the illumination shaft 214 of the illumination device 220. The polarization switching mechanism 232 includes a polarization filter 234 and a motor 236.

As shown in FIG. 9B, the polarizing filter 234 has a rectangular shape, and a first region 234a, a second region 234b, and a third region 234c are provided at different positions in the longitudinal direction (S direction). The first region 234a is provided with a first linear polarizer that transmits the S polarization component, and the second region 234b is provided with a second linear polarizer that transmits the P polarization component. No polarizer is provided in the third region 234c. The motor 236 slides the polarizing filter 234 in the S direction to switch the regions 234a to 234c of the polarizing filter 234 arranged on the illumination shaft 214. The motor 236 is a drive unit that displaces the first linear polarizer and the second linear polarizer provided on the polarizing filter 234 with respect to the illumination shaft 214.

When the first region 234a is arranged on the illumination shaft 214, that is, when the first linear polarizer is inserted on the illumination shaft 214, only the S polarization component passes through the polarization filter 234, so that the S polarization illumination can be used. A certain first illumination light 212s is generated. When the second region 234b is arranged on the illumination axis 214, that is, when the second linear polarizer is inserted on the illumination axis 214, only the P polarization component passes through the polarization filter 234, so that the P-polarized illumination can be used. A certain second illumination light 212p is generated. When the third region 234c is arranged on the illumination shaft 214, that is, when the linear polarizer is not inserted on the illumination shaft 214, the unpolarized illumination light passes through the polarizing filter 234 as it is, so that the unpolarized illumination light is transmitted. 212 is generated. In this way, the polarization switching mechanism 232 is configured to switch the polarization state of the illumination light 212 projected from the illumination device 220.

The operation of the lighting device 220 is controlled by, for example, the lighting control unit 40 described above. The illumination control unit 40 controls the operation of the motor 236 and has a first illumination mode in which the first region 234a is arranged on the illumination shaft 214 and a second illumination mode in which the second region 234b is arranged on the illumination shaft 214. And the third illumination mode in which the third region 234c is arranged on the illumination shaft 214. Even when the lighting device 220 according to this modification is used, the same effect as that of the above-described embodiment can be obtained.

In a further modification, a first illuminating device for projecting S-polarized illumination onto an imaging target and a second illuminating device for projecting P-polarized illumination on an imaging target may be provided separately. As the first illumination device, a first laser light source having a linearly polarized oscillation mode may be used, or a first unpolarized or randomly polarized light source and a first linear polarizer may be combined. Similarly, as the second illumination device, a second laser light source having a linearly polarized oscillation mode may be used, or an unpolarized or randomly polarized second light source and a second linear polarizer may be combined.

Although the present invention has been described above with reference to the above-described embodiment, the present invention is not limited to the above-described embodiment, and the present invention is not limited to the above-described embodiment, and the configurations shown in each display example are appropriately combined or replaced. Is also included in the present invention.

In the above-described embodiment and modification, an example applied to the determination of whether or not the polarized sunglasses used by the driver 70 are used has been described. In a further modification, it may be applied to determine whether or not an arbitrary linear polarizer is included in the imaging target. For example, the first image of the imaged object irradiated with the first illumination light linearly polarized in the first direction and the second illumination light linearly polarized in the second direction orthogonal to the first direction were irradiated. It may be determined whether or not the imaged object includes a linear polarizer based on the second image obtained by capturing the imaged object.

10 ... Imaging device, 12 ... Illumination light, 12s ... First illumination light, 12p ... Second illumination light, 14 ... Illumination axis, 20 ... Lighting device, 22 ... Camera, 40 ... Illumination control unit, 42 ... Imaging control unit, 44 ... image acquisition unit, 46 ... image processing unit, 60 ... vehicle, 70 ... driver.

Claims (7)

With the camera
An illumination device that selectively irradiates a first illumination light linearly polarized in the first direction and a second illumination light linearly polarized in a second direction orthogonal to the first direction toward an imaging target of the camera. When,
An image acquisition unit that acquires a first image including the image pickup target irradiated with the first illumination light and a second image including the image pickup target irradiated with the second illumination light from the camera.
An image pickup apparatus comprising: an image processing unit for determining whether or not a linear polarizer is included in the image pickup target based on the first image and the second image. The camera captures the face of the driver of the vehicle.
The first direction is a direction orthogonal to both the illumination direction of the first illumination light and the vertical direction of the vehicle.
The second direction is a direction orthogonal to both the illumination direction of the second illumination light and the first direction.
The imaging unit according to claim 1, wherein the image processing unit determines whether or not a linear polarizing element that shields the linearly polarized light component in the first direction is included in a range that overlaps with the driver's face. apparatus. The lighting device combines the first light source that generates the first illumination light, the second light source that generates the second illumination light, the first illumination light, and the second illumination light on the illumination axis. Including the combiner element
A lighting control unit that switches between a first period in which the first light source is turned on and a second period in which the second light source is turned on.
The first or second claim is further comprising an imaging control unit that causes the camera to image the first image in the first period and causes the camera to image the second image in the second period. The imaging device described. The lighting control unit periodically switches between the first period, the second period, and the third period in which both the first light source and the second light source are turned on.
The imaging device according to claim 3, wherein the imaging control unit causes the camera to capture a third image in the third period. The illumination device includes a light source that generates illumination light containing two linear polarization components orthogonal to each other, and a first linear polarizer that can be inserted on the illumination axis of the illumination light to generate the first illumination light. , A second linear polarizer that can be inserted on the illumination axis to generate the second illumination light, and a drive unit that displaces the first linear polarizer and the second linear polarizer with respect to the illumination axis. And, including
An illumination control unit that switches between a first period in which the first linear polarizer is inserted on the illumination axis and a second period in which the second linear polarizer is inserted on the illumination axis.
The first or second claim is further comprising an imaging control unit that causes the camera to image the first image in the first period and causes the camera to image the second image in the second period. The imaging device described. The illumination control unit periodically switches between the first period, the second period, and the third period in which both the first linear polarizer and the second linear polarizer are retracted from the illumination axis. ,
The imaging device according to claim 5, wherein the imaging control unit causes the camera to capture a third image in the third period. The first image of an imaged object irradiated with the first illumination light linearly polarized in the first direction and the second illumination light linearly polarized in the second direction orthogonal to the first direction are irradiated. A determination method characterized in that it is determined whether or not a linear polarizer is included in the imaging target based on the second image obtained by capturing the imaging target.

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