Patent Publication Number: US-2022236463-A1

Title: Optical element, optical device, and imaging apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a Continuation of PCT International Application No. PCT/JP2020/040064 filed on Oct. 26, 2020 claiming priority under 35 U.S.C § 119(a) to Japanese Patent Application No. 2019-197777 filed on Oct. 30, 2019. Each of the above applications is hereby expressly incorporated by reference, in its entirety, into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical element, an optical device, and an imaging apparatus, for capturing a multispectral image. 
     2. Description of the Related Art 
     JP2016-177060A describes a color wheel having a color filter having a rotationally symmetric disposition, and a projection device using the color wheel. In addition, JP2016-102733A describes a color filter comprising first to third filter regions. The third filter region is disposed symmetrically with respect to the center. In addition, JP6124079B describes a polarizing color filter plate in which a polarizing filter is disposed in a fan-shaped region, and an imaging apparatus comprising the color filter plate. Further, as described in JP2013-57761A, the amount of image deviation increases or decreases depending on the position of the centroid of an aperture. 
     SUMMARY OF THE INVENTION 
     One embodiment according to the technology of the present disclosure provides an optical element, an optical device, and an imaging apparatus, which can acquire a multispectral image having a good image quality. 
     An optical element according to a first aspect of the present invention comprises: a frame having a plurality of aperture regions; and a plurality of optical filters that are mounted in the plurality of aperture regions, the plurality of optical filters including at least two types of filters having different wavelength ranges of transmitted light, in which positions of centroids of the aperture regions are the same for the at least two types of filters. 
     A second aspect provides the optical element according to the first aspect, in which the centroid is a centroid of an image generated by the aperture region. 
     A third aspect provides the optical element according to the first or second aspect, in which the plurality of optical filters are mounted in aperture regions having aperture areas corresponding to the wavelength ranges. 
     A fourth aspect provides the optical element according to the third aspect, in which the plurality of optical filters are mounted such that an optical filter having a longer wavelength at a center of the wavelength range is mounted in an aperture region having a larger aperture area. 
     A fifth aspect provides the optical element according to any one of the first to fourth aspects, in which the frame has a feature point that coincides with the centroid in a case where the frame is viewed from a front, and the aperture region has a smaller aperture area as a distance from the feature point increases. 
     A sixth aspect provides the optical element according to any one of the first to fifth aspects, in which for at least one of the wavelength ranges, a plurality of optical filters having the same wavelength range are mounted in the plurality of aperture regions, respectively. 
     A seventh aspect provides the optical element according to any one of the first to sixth aspects, in which the plurality of aperture regions have different aperture shapes for each of the wavelength ranges of the mounted optical filters, and the plurality of optical filters have different shapes for each wavelength range, the shapes corresponding to the aperture shapes. 
     An eighth aspect provides the optical element according to any one of the first to seventh aspects, in which at least one set of the plurality of optical filters has two or more types of wavelength ranges in the plurality of aperture regions. 
     A ninth aspect provides the optical element according to any one of the first to eighth aspects, the optical element further comprising a plurality of polarizing filters having different polarization directions. 
     A tenth aspect provides the optical element according to the ninth aspect, in which the polarization directions are the same for each wavelength range. 
     An optical device according to an eleventh aspect comprises: the optical element according to any one of the first to eighth aspects; and a lens that forms an optical image of a subject, in which the optical element is disposed at a pupil position of the lens such that the centroid coincides with an optical axis of the lens. 
     A twelfth aspect provides the optical device according to the eleventh aspect, the optical device further comprising a plurality of polarizing filters having different polarization directions, in which polarizing filters having the same polarization direction among the plurality of polarizing filters are disposed in the aperture regions in which optical filters having the same wavelength range are mounted. 
     A thirteenth aspect provides the optical device according to the twelfth aspect, in which at least one of the optical element or the plurality of polarizing filters is inserted into an optical path of light incident on the lens or is retracted from the optical path. 
     An imaging apparatus according to a fourteenth aspect comprises: the optical device according to any one of the eleventh to thirteenth aspects; an imaging element including a plurality of pixel groups that selectively receive light transmitted through any of the plurality of optical filters; and a signal processing unit that generates a plurality of images corresponding to the wavelength ranges of the plurality of optical filters, respectively, based on a signal output from the imaging element. 
     A fifteenth aspect provides the imaging apparatus according to the fourteenth aspect, in which the imaging element comprises, on a pixel, a plurality of types of optical filters having different transmission wavelength ranges and a plurality of types of polarization portions having different transmission polarization directions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing a schematic configuration of an imaging apparatus according to a first embodiment. 
         FIGS. 2A and 2B  are front views showing a configuration of a bandpass filter unit. 
         FIGS. 3A and 3B  are front views showing a configuration of a polarizing filter unit. 
         FIG. 4  is a diagram showing a relationship between an aperture shape and an image quality at the time of defocus. 
         FIG. 5  is another diagram showing a relationship between an aperture shape and an image quality at the time of defocus. 
         FIG. 6  is still another diagram showing a relationship between an aperture shape and an image quality at the time of defocus. 
         FIG. 7  is still another diagram showing a relationship between an aperture shape and an image quality at the time of defocus. 
         FIG. 8  is still another diagram showing a relationship between an aperture shape and an image quality at the time of defocus. 
         FIG. 9  is still another diagram showing a relationship between an aperture shape and the image quality at the time of defocus. 
         FIG. 10  is still another diagram showing a relationship between an aperture shape and an image quality at the time of defocus. 
         FIG. 11  is still another diagram showing a relationship between an aperture shape and an image quality at the time of defocus. 
         FIG. 12  is still another diagram showing a relationship between an aperture shape and an image quality at the time of defocus. 
         FIG. 13  is a diagram showing an arrangement of pixels of an imaging element. 
         FIG. 14  is a diagram showing a configuration of the imaging element. 
         FIG. 15  is a cross-sectional view showing a configuration of the imaging element. 
         FIG. 16  is a diagram showing an arrangement pattern of polarizing filter elements. 
         FIG. 17  is a diagram showing an arrangement pattern of spectral filter elements. 
         FIG. 18  is a diagram showing a transmission wavelength characteristic of the spectral filter element. 
         FIG. 19  is a block diagram showing a schematic configuration of a signal processing unit. 
         FIG. 20  is a conceptual diagram of image generation. 
         FIGS. 21A to 21D  are diagrams showing a configuration of a light screen. 
         FIG. 22  is a conceptual diagram of the image generation by the imaging apparatus. 
         FIGS. 23A and 23B  are diagrams showing another aspect of the bandpass filter unit. 
         FIGS. 24A and 24B  are diagrams showing still another aspect of the bandpass filter unit. 
         FIG. 25  is a diagram showing still another aspect of the bandpass filter unit. 
         FIGS. 26A to 26C  are diagrams showing still another aspect of the bandpass filter unit. 
         FIGS. 27A and 27B  are diagrams showing still another aspect of the bandpass filter unit. 
         FIGS. 28A to 28D  are diagrams showing a state of image shift at the time of defocus in the related art. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An optical element, an optical device, and an imaging apparatus according to one embodiment of the present invention are as follows. In the description, the accompanying drawings will be referred to as needed. 
     First Embodiment 
     &lt;Configuration of Imaging Apparatus&gt; 
       FIG. 1  is a diagram showing a schematic configuration of an imaging apparatus according to a first embodiment. An imaging apparatus  1  according to the first embodiment is an imaging apparatus that captures a multispectral image of four bands, and mainly comprises an imaging optical system  10  (optical device), an imaging element  100 , and a signal processing unit  200 . 
     &lt;Imaging Optical System&gt; 
     The imaging optical system  10  is configured by a plurality of combinations of lenses  12  (lenses) that form an optical image of a subject, and has a bandpass filter unit  16  (optical element) and a polarizing filter unit  18  (polarizing filter) in an optical path thereof. The bandpass filter unit  16  and the polarizing filter unit  18  are disposed in an optical path of light transmitted through the lens  12  (for example, at a pupil position or its vicinity) in a state in which an optical axis L of the lens  12  and optical axes of the bandpass filter unit  16  and of the polarizing filter unit  18  coincide with each other (a state in which a centroid  19 G of a frame  19  and a centroid  20 G of a frame  20  and an optical axis L of the lens  12  coincide with each other). In addition, the imaging optical system  10  includes a focus adjustment mechanism (not shown). The focus adjustment mechanism adjusts the focus by moving a focus lens included in the imaging optical system  10  back and forth along the optical axis L. 
     &lt;Configuration of Bandpass Filter Unit&gt; 
       FIGS. 2A and 2B  are front views of the bandpass filter unit  16 . As shown in  FIG. 2A , the bandpass filter unit  16  comprises a frame  20  (frame) and bandpass filters  50 A to  50 D (optical filters). The bandpass filters  50 A to  50 D are mounted in aperture regions  52 A to  52 D (a plurality of aperture regions; see  FIG. 2B ) formed in the frame  20 , respectively. Aperture regions  52 B to  52 D are each composed of a plurality of (two) apertures, and bandpass filters  50 B to  50 D having the same wavelength range of transmitted light are mounted in the aperture regions  52 B to  52 D, respectively. Further, for the bandpass filters  50 A to  50 D, the centroid of the aperture regions  52 B to  52 D coincides with the centroid  20 G of the frame  20 . 
     In the first embodiment, the wavelength ranges of the transmitted light of the bandpass filters  50 A to  50 D can be near infrared, red, green, and blue, respectively. That is, the bandpass filters  50 A to  50 D include at least two types of filters having different wavelength ranges of transmitted light. The wavelength range of the transmitted light of the bandpass filter is not limited to the above combination, and the wavelength range can be selected according to the spectrum in which the image is to be acquired. 
     The bandpass filters  50 A to  50 D described above each transmit light having one type of wavelength, but at least one set of the bandpass filters may have two or more types of wavelength ranges. Among the plurality of bandpass filters, at least one set of bandpass filters may have two or more types of wavelength ranges. Here, “one set” is a combination that the centroid of the aperture regions  52 B to  52 D coincides with the centroid  20 G, and is, for example, a bandpass filter  50 B. In a case where the centroid  20 G has an aperture region, one set is, for example, a bandpass filter  50 A. Further, “having two or more types of wavelength ranges” means that there are two or more types of wavelength ranges to be transmitted, and, for example, a case where two types of wavelength ranges of red and blue are transmitted in the bandpass filter  50 B is applicable. 
     As shown in  FIG. 2B , the frame  20  has a plurality of aperture regions  52 A to  52 D. The aperture region  52 A is a single aperture region surrounding the centroid  20 G of the frame  20 , and the aperture regions  52 B to  52 D are a plurality of aperture regions arranged symmetrically with respect to the centroid  20 G of the frame  20 . Specifically, the two aperture regions  52 B are arranged symmetrically with respect to the centroid  20 G (feature point), the two aperture regions  52 C are arranged symmetrically with respect to the centroid  20 G, and the two aperture regions  52 D are arranged symmetrically with respect to the centroid  20 G. 
     Further, the positions of the centroids of the aperture regions  52 A to  52 D (for the aperture regions having a plurality of apertures such as the aperture regions  52 B to  52 D, the centroids of all the plurality of apertures) are the same. However, the positions of the centroids may not match for all the aperture regions, and it is sufficient that the positions of the centroids match for at least two types of aperture regions. Further, in a case where the frame  20  is viewed from the front, the centroid of the image generated corresponding to the aperture region coincides with the centroid (feature point) of the aperture region. The centroid of the image generated corresponding to the aperture region refers to the in-focus position located on the optical axis of the imaging optical system. 
     The bandpass filters  50 A to  50 D are mounted in an aperture region having an aperture area corresponding to the wavelength range of transmitted light. That is, a bandpass filter having a longer wavelength at the center of the wavelength range is mounted in an aperture region having a larger aperture area. Further, the bandpass filters  50 A to  50 D are mounted such that a bandpass filter mounted farther from the centroid  20 G of the frame  20  is mounted in the aperture region having a narrower aperture area. The aperture area of these aperture regions becomes smaller as the distance from the centroid (which coincides with the centroid of the subject image in a case where the frame is viewed from the front), which is a feature point of the frame, increases. 
     In the first embodiment, the aperture regions  52 A to  52 D have a larger aperture area in the order of the aperture regions  52 A to  52 D. Further, the aperture region  52 A has the shortest distance from the centroid  20 G (distance between the centroid of the aperture region and the centroid  20 G) (distance is zero), and thereafter, the aperture regions  52 B to  52 D are farther from the centroid  20 G in this order. Therefore, the bandpass filter  50 A (for near-infrared light) having the longest wavelength in the center of the wavelength range of the transmitted light is mounted in the aperture region  52 A having the widest aperture area and the shortest distance from the centroid  20 G. Similarly, the bandpass filters  50 B (for red light),  50 C (for green light), and  50 D (for blue light) are respectively mounted in the aperture regions  52 B to  52 D, which are far from the centroid  20 G and which have a narrow aperture area. 
     &lt;Configuration of Polarizing Filter Unit&gt; 
       FIGS. 3A and 3B  are front views of the polarizing filter unit  18 . At least one of the bandpass filter unit or the polarizing filter unit  18  described above is inserted into the optical path of light incident on the lens  12  (imaging optical system  10 ) or is retracted from the optical path by an operation mechanism (not shown). The polarizing filter unit  18  has a frame  19  having a centroid  19 G as a centroid, and the frame  19  has aperture regions  19 A to  19 D having a position, a size, and a shape corresponding to the above-mentioned aperture regions  52 A to  52 D (see  FIG. 3A ). Similarly to the above-mentioned aperture regions  52 A to  52 D, the aperture region  19 A is a single aperture region surrounding the centroid  19 G of the frame  19 , and the aperture regions  19 B to  19 D are a plurality of aperture regions arranged symmetrically with respect to the centroid  19 G. Further, polarizing filters  21 A to  21 D are mounted in the aperture regions  19 A to  19 D (see  FIG. 3B ). The polarizing filters  21 A to  21 D are a plurality of polarizing filters having different polarization directions. Assuming that the polarization directions (polarization angles) in the aperture regions  19 A to  19 D are θ 1  to θ 4 , respectively, for example, θ 1 =0 deg, θ 2 =45 deg, θ 3 =90 deg, and θ 4 =135 deg can be satisfied. 
     The polarizing filters having the same polarization direction among the plurality of polarizing filters  21 A to  21 D are disposed in the aperture regions in which bandpass filters having the same wavelength range are mounted. Specifically, the two polarizing filters  21 B (both polarization directions are the same at 45 deg) are mounted in the two aperture regions  19 B corresponding to the two aperture regions  52 B (where the bandpass filter  50 B is mounted). Further, the two polarizing filters  21 C (both polarization directions are the same at 90 deg) are mounted in the two aperture regions  19 C corresponding to the two aperture regions  52 C (where the bandpass filter  50 C is mounted). Further, the two polarizing filters  21 D (both polarization directions are the same at 135 deg) are mounted in the two aperture regions  19 D corresponding to the two aperture regions  52 D (where the bandpass filter  50 D is mounted). That is, the polarization direction is the same for each wavelength range. 
     &lt;Pupil Division&gt; 
     In the imaging optical system  10 , a pupil region is divided into four pupil regions Z 1  to Z 4  (see  FIGS. 2A to 3B ) by the bandpass filter unit  16  and the polarizing filter unit  18  having the above-described configuration (pupil division). The pupil region Z 1  corresponds to the bandpass filter  50 A, the aperture region  52 A, the aperture region  19 A, and the polarizing filter  21 A. The pupil region Z 2  corresponds to the bandpass filter  50 B, the aperture region  52 B, the aperture region  19 B, and the polarizing filter  21 B. The pupil region Z 3  corresponds to the bandpass filter  50 C, the aperture region  52 C, the aperture region  19 C, and the polarizing filter  21 C. The pupil region Z 4  corresponds to the bandpass filter  50 D, the aperture region  52 D, the aperture region  19 D, and the polarizing filter  21 D. 
     &lt;Image Shift at Time of Defocus in Related Art&gt; 
     Here, the image shift at the time of defocus in the related art will be described. Consider a case where a subject  90  (shape of the letter “A”) shown in  FIG. 28A  is imaged by a bandpass filter unit  91  shown in  FIG. 28B  and an imaging optical system (not shown). The bandpass filter unit  91  is a filter unit in which four bandpass filters  90 R,  90 G,  90 M, and  90 B having different transmission wavelength ranges are mounted on a frame  92 . 
     As shown in  FIG. 28C , the position where the subject  90  is in focus on the optical axes of the bandpass filter unit  91  and of the imaging optical system is defined as a point Q 0 , the position closer to the subject  90  than the point Q 0  is defined as a point Q 1 , and the position farther from the subject  90  than the point Q 0  is defined as a point Q 2 . In this case, as shown in  FIG. 28D , the image shift does not occur at the point Q 0  as in a subject image  93 . On the other hand, in a subject image  94  at the point Q 1 , four subject images  94 R,  94 G,  94 M, and  94 B with image shifts are generated corresponding to the transmission wavelength ranges of the bandpass filters  90 R,  90 G,  90 M, and  90 B. Similarly, in a subject image  95  at the point Q 2 , four subject images  95 R,  95 G,  95 M, and  95 B with image shifts are generated corresponding to the transmission wavelength ranges of the bandpass filters  90 R,  90 G,  90 M, and  90 B (the direction of the shift is opposite to that of the subject image  94 ). However, the related art has not suppressed such image shift at the time of defocus. 
     &lt;Effect of Area and Disposition of Aperture Region&gt; 
     Here, the relationship between the shape, disposition, and arrangement of the aperture region and the defocus and the image shift will be described. Specifically, the results of a simulation assuming that a subject (an object having the shape of the letter “A” and a point light source) is imaged using various apertures and an imaging optical system (not shown) will be described. 
     &lt;Case 1: In Case of Aperture without Centroid Shift&gt; 
       FIG. 4  is a diagram showing results in a case where an aperture  1001  is used. The aperture  1001  is circular, and a centroid  1001 G of the aperture  1001  exists on the optical axis of the imaging optical system. In the upper part of  FIG. 4 , the part with reference numeral  1011 A indicates a subject image in an in-focus state (images of the above-mentioned object and point light source, the upper right part is the image of the point light source; the same in Case 1 to Case 9), and indicates the subject image at positions progressively farther away from an in-focus position (positions on the optical axis of the imaging optical system) toward the right side in  FIG. 4 . The subject image becomes blurred (defocused) as the distance from the in-focus position increases. Meanwhile, the lower part of  FIG. 4  is a graph showing a brightness distribution of the image of the point light source at the same positions as those in the upper part of  FIG. 4 . For example, the part with reference numeral  1021 A is a graph at the same position (in-focus position) as that of reference numeral  1011 A. As the distance from the in-focus position increases, the brightness distribution becomes wider and gentler. 
     &lt;Case 2: In Case of Aperture with Centroid Shift&gt; 
       FIG. 5  is a diagram showing results in a case where an aperture  1002  is used. The aperture  1002  is fan-shaped, and a centroid  1002 G of the aperture  1002  is offset from the optical axis of the imaging optical system. In such a case, the subject image shifts according to the defocus. For example, the peak of brightness shifts to the left side in  FIG. 5  (graph of reference numeral  1022 B), just by being slightly offset from the in-focus state (indicated by reference numerals  1012 A and  1022 A) as in reference numeral  1012 B. The peak of brightness in the in-focus state is indicated by a dotted line in the graph (same in the following cases). 
     &lt;Case 3: In Case of Plurality of Apertures with Centroid Aligned (Aperture Size: Medium)&gt; 
       FIG. 6  is a diagram showing results in a case where apertures  1003  are used. The apertures  1003  are formed of two fan-shaped regions, and a centroid  1003 G of the apertures  1003  exists on the optical axis of the imaging optical system. In such a case, the subject image does not shift in a state (reference numerals  1013 B and  1023 B) of being slightly offset from the in-focus state (reference numerals  1013 A and  1023 A). However, in a case where the deviation from the in-focus state becomes large (the states on the right sides of reference numerals  1013 C and  1023 C), the subject image shifts corresponding to each of the two regions of the aperture  1003 , and the subject image becomes doubled (which corresponds to a state in which two peaks of brightness occur). 
     &lt;Case 4: In Case of Plurality of Apertures with Centroid Aligned (Aperture Size: Small)&gt; 
       FIG. 7  is a diagram showing results in a case where apertures  1004  are used. The apertures  1004  are formed of two fan-shaped regions like the aperture  1003  shown in  FIG. 6 , and a centroid  1004 G of the apertures  1004  exists on the optical axis of the imaging optical system, but the aperture area is narrower than that of the aperture  1003 . In such a case, the subject image in a state of being offset from the in-focus state (indicated by reference numerals  1014 A and  1024 A) shifts while a clear state is maintained as compared with Case 3. For example, even at a position farthest from the in-focus state (indicated by reference numerals  1014 H and  1024 H), the subject image (upper part of  FIG. 7 ) is clearer than that of Case 3, and the peak is clear even in the brightness graph. 
     &lt;Case 5: In Case of Plurality of Vertical Apertures (Aperture Size: Large)&gt; 
       FIG. 8  is a diagram showing results in a case where apertures  1005  are used. The apertures  1005  are formed of two vertical regions extending in the vertical direction in the figure, and a centroid  1005 G of the apertures  1005  exists on the optical axis of the imaging optical system. Even in the case of such apertures, similarly to the case of the two fan-shaped apertures (Case 3 and Case 4), the subject image shifts (according to the defocus) as the distance from the in-focus state (indicated by reference numerals  1015 A and  1025 A) increases, and a double image is generated in the state on the right side of the states indicated by reference numerals  1015 C and  1025 C. 
     &lt;Case 6: In Case of Plurality of Vertical Apertures (Aperture Size: Medium)&gt; 
       FIG. 9  is a diagram showing results in a case where apertures  1006  are used. 
     Similarly to the aperture  1005  in Case 5, the apertures  1006  are formed of two vertical regions extending in the vertical direction in  FIG. 9 , and a centroid  1006 G of the apertures  1006  exists on the optical axis of the imaging optical system, but the aperture area is narrower than that of the aperture  1005 . Even in the case of such apertures, the subject image shifts as the distance from the in-focus state (indicated by reference numerals  1016 A and  1026 A) increases, but the degree of duality of the subject image is reduced as compared with the case of Case 5. For example, a double image is generated in the state indicated by reference numerals  1015 C and  1025 C of Case 5 (see  FIG. 8 ), but in a state corresponding to this in Case 6 (the deviation from the in-focus state is the same; in  FIG. 9 , the state indicated by reference numerals  1016 C and  1026 C), the double image is not generated (the peak of the brightness graph is one). 
     &lt;Case 7: In Case of Plurality of Vertical Apertures (Aperture Size: Small)&gt; 
       FIG. 10  is a diagram showing results in a case where apertures  1007  are used. Similarly to the above-mentioned apertures  1005  and  1006 , the apertures  1007  are formed of two vertical regions extending in the vertical direction in  FIG. 10 , and a centroid  1007 G of the apertures  1007  exists on the optical axis of the imaging optical system, but the aperture area is narrower than those of the apertures  1005  and  1006 . Even in the case of such apertures, the subject image shifts as the distance from the in-focus state (indicated by reference numerals  1017 A and  1027 A) increases, but the degree of duality of the subject image is further reduced as compared with the case of Case 5 and Case 6. Specifically, the double image is generated in Case 7 on the right side (the state in which the focus is further offset) of the state indicated by reference numerals  1017 E and  1027 E. 
     &lt;Case 8: In Case of Vertical Apertures Moved to Center Portion (Aperture Size: Medium)&gt; 
       FIG. 11  is a diagram showing results in a case where apertures  1008  are used. The apertures  1008  have the same shape and size as the apertures  1006  in Case 6, but the two apertures are disposed closer (closer to a centroid  1008 G) than in Case 6. Even in the case of such apertures, the subject image shifts as the distance from the in-focus state (indicated by reference numerals  1018 A and  1028 A) increases, but the degree of duality of the subject image is reduced as compared with the case of Case 6. Specifically, the double image is generated in Case 8 on the right side (the state in which the focus is further offset) of the state indicated by reference numerals  1018 E and  1028 E. 
     &lt;Case 9: In Case of Single Vertical Aperture Disposed in Center Portion&gt; 
       FIG. 12  is a diagram showing results in a case where an aperture  1009  is used. The aperture  1009  is a single aperture with a centroid  1009 G that coincides with the center of the optical axis of the imaging optical system. In the case of such an aperture, similarly to the case of the aperture  1001  of Case 1, the subject image does not shift even at a position away from the in-focus state, and thus the double image is not generated. 
     &lt;Summary of Case 1 to Case 9&gt; 
     As can be seen from Case 1 to Case 9, by increasing the aperture for the center portion of the lens (the portion close to the optical axis of the imaging optical system) and reducing the aperture at the peripheral portion, it is possible to suppress the shift of the subject image and the generation of the double image in a wide defocus range (at a position where the degree of deviation from the in-focus state is large). In the optical element, the imaging optical system, and the imaging apparatus according to the embodiment of the present invention, the shape, size, and disposition of the aperture are set in consideration of the above point, and thus it is possible to suppress subject image shift (image shift) at the time of defocus, and to acquire a multispectral image with a good image quality. 
     &lt;Configuration of Imaging Element&gt; 
       FIG. 13  is a diagram showing a schematic configuration of an arrangement of pixels of the imaging element. As shown in  FIG. 10 , the imaging element  100  has a plurality of types of pixels (pixel P 1  to pixel P 16 ) on a light-receiving surface thereof. These pixels P 1  to P 16  are regularly arranged at a certain pitch along a horizontal direction (x-axis direction) and a vertical direction (y-axis direction). In the imaging apparatus  1  according to the first embodiment, in the imaging element  100 , one pixel block PB (X,Y) is configured by 16 (4×4) adjacent pixels P 1  to P 16 , and the pixel blocks PB (X,Y) are regularly arranged along the horizontal direction (x-axis direction) and the vertical direction (y-axis direction). (X,Y) indicate positions in the x-axis direction and the y-axis direction, respectively. 
       FIG. 14  is a diagram showing a schematic configuration of the imaging element  100 . In addition,  FIG. 15  is a cross-sectional view showing a schematic configuration of one pixel (broken line portion in  FIG. 14 ). The imaging element  100  includes a pixel array layer  110 , a polarizing filter element array layer  120  (polarization portion), a spectral filter element array layer  130  (optical filter), and a micro lens array layer  140 . That is, the imaging element  100  comprises, on a pixel, a plurality of types of optical filters having different transmission wavelength ranges and a plurality of types of polarization portions having different transmission polarization directions. The layers are disposed in the order of the pixel array layer  110 , the polarizing filter element array layer  120 , the spectral filter element array layer  130 , and the micro lens array layer  140  from an image plane side to an object side. 
     The pixel array layer  110  is configured by two-dimensionally arranging a large number of photodiodes  112 . One photodiode  112  configures one pixel. The photodiodes  112  are regularly disposed along the horizontal direction (x-axis direction) and the vertical direction (y-axis direction). The polarizing filter element array layer  120  is configured by two-dimensionally arranging four types of polarizing filter elements  122 A to  122 D having different polarization directions of the transmitted light. Each of the polarizing filter elements  122 A to  122 D, one of which is provided for each pixel, is disposed at the same intervals as the photodiodes  112 . The polarizing filter elements  122 A to  122 D are regularly arranged in each pixel block PB (X,Y). 
       FIG. 16  is a diagram showing an example of an arrangement pattern of the polarizing filter elements in one pixel block. As shown in  FIG. 16 , in the imaging apparatus  1  according to the first embodiment, the pixel P 1 , the pixel P 3 , the pixel P 9 , and the pixel P 11  comprise the polarizing filter element  122 A. In addition, the pixel P 2 , the pixel P 4 , the pixel P 10 , and the pixel P 12  comprise the polarizing filter element  122 B. In addition, the pixel P 3 , the pixel P 7 , the pixel P 13 , and the pixel P 15  comprise the polarizing filter element  122 C. In addition, the pixel P 4 , the pixel P 8 , the pixel P 14 , and the pixel P 16  comprise the polarizing filter element  122 D. 
     The polarizing filter elements  122 A to  122 D transmit the light in different polarization directions from each other. Specifically, the polarizing filter element  122 A transmits the light in the polarization direction θA (for example, θA=45°). The polarizing filter element  122 B transmits the light in the polarization direction θB (for example, θB=90°). The polarizing filter element  122 C transmits the light in the polarization direction θC (for example, θC=135°). The polarizing filter element  122 D transmits the light in the polarization direction θD (for example, θD=0°). 
     The spectral filter element array layer  130  is configured by two-dimensionally arranging four types of spectral filter elements  132 A to  132 D having different transmission wavelength characteristics. Each spectral filter element  132 A to  132 D, one of which is provided for each pixel, is disposed at the same intervals as the photodiodes  112 . The spectral filter elements  132 A to  132 D are regularly arranged in each pixel block PB (X,Y). 
       FIG. 17  is a diagram showing an example of an arrangement pattern of the spectral filter elements in one pixel block. As shown in  FIG. 17 , in the imaging apparatus  1  according to the first embodiment, the pixel P 1 , the pixel P 2 , the pixel P 5 , and the pixel P 6  comprise the spectral filter element  132 A. In addition, the pixel P 3 , the pixel P 4 , the pixel P 7 , and the pixel P 8  comprise the spectral filter element  132 B. In addition, the pixel P 9 , the pixel P 10 , the pixel P 13 , and the pixel P 14  comprise the spectral filter element  132 C. In addition, the pixel P 11 , the pixel P 12 , the pixel P 15 , and the pixel P 16  comprise the spectral filter element  132 D. 
       FIG. 18  is a graph showing an example of the transmission wavelength characteristic of each spectral filter element. In  FIG. 18 , A shows the transmission wavelength characteristic of the spectral filter element  132 A. B shows the transmission wavelength characteristic of the spectral filter element  132 B. C shows the transmission wavelength characteristic of the spectral filter element  132 C. D shows the transmission wavelength characteristic of the spectral filter element  132 D. The spectral filter elements  132 A to  132 D have different transmission wavelength characteristics from each other. Note that  FIG. 18  shows an example in a case in which the spectral filter element  132 A is configured by the spectral filter element which transmits blue (B) light, the spectral filter element  132 B is configured by the spectral filter element which transmits green (G) light, the spectral filter element  132 C is configured by the spectral filter element which transmits red (R) light, and the spectral filter element  132 D is configured by the spectral filter element which transmits infrared (IR) light. 
     Here, as shown in  FIG. 18 , wavelength ranges λ 1  to λ 4  of the light transmitted through the bandpass filters  50 A to  50 D described above are set within ranges of transmission wavelength ranges of the spectral filter elements  132 A to  132 D. That is, the wavelength ranges λ 1  to λ 4  of the light transmitted through the bandpass filters  50 A to  50 D are set in regions of which the transmission wavelength ranges of the spectral filter elements  132 A to  132 D overlap with each other. In other words, the transmission wavelength ranges of the spectral filter elements  132 A to  132 D are set so as to cover the transmission wavelength ranges of the bandpass filters  50 A to  50 D. Therefore, each of the spectral filter elements  132 A to  132 D uses a filter which transmits light in a wide range. 
     The micro lens array layer  140  is configured by two-dimensionally arranging a large number of micro lenses  142 . Each micro lens  142 , one of which is provided for each pixel, is disposed at the same intervals as the photodiodes  112 . The micro lenses  142  are provided for a purpose of efficiently condensing the light from the imaging optical system  10  on the photodiodes  112 . 
     In the imaging element  100  configured as described above, in each pixel block PB (X,Y), each of the pixels P 1  to P 16  receives the light from the imaging optical system  10  as follows. 
     That is, the pixel P 1  receives the light from the imaging optical system  10  via the spectral filter element  132 A (transmission wavelength characteristic A) and the polarizing filter element  122 A (polarization direction θA). In addition, the pixel P 2  receives the light from the imaging optical system  10  via the spectral filter element  132 A (transmission wavelength characteristic A) and the polarizing filter element  122 B (polarization direction θB). In addition, the pixel P 3  receives the light from the imaging optical system  10  via the spectral filter element  132 B (transmission wavelength characteristic B) and the polarizing filter element  122 A (polarization direction θA). In addition, the pixel P 4  receives the light from the imaging optical system  10  via the spectral filter element  132 B (transmission wavelength characteristic B) and the polarizing filter element  122 B (polarization direction θB). In addition, the pixel P 5  receives the light from the imaging optical system  10  via the spectral filter element  132 A (transmission wavelength characteristic A) and the polarizing filter element  122 C (polarization direction θC). In addition, the pixel P 6  receives the light from the imaging optical system  10  via the spectral filter element  132 A (transmission wavelength characteristic A) and the polarizing filter element  122 D (polarization direction θD). In addition, the pixel P 7  receives the light from the imaging optical system  10  via the spectral filter element  132 B (transmission wavelength characteristic B) and the polarizing filter element  122 C (polarization direction θC). In addition, the pixel P 8  receives the light from the imaging optical system  10  via the spectral filter element  132 B (transmission wavelength characteristic B) and the polarizing filter element  122 D (polarization direction θD). In addition, the pixel P 9  receives the light from the imaging optical system  10  via the spectral filter element  132 C (transmission wavelength characteristic C) and the polarizing filter element  122 A (polarization direction θA). In addition, the pixel P 10  receives the light from the imaging optical system  10  via the spectral filter element  132 C (transmission wavelength characteristic C) and the polarizing filter element  122 B (polarization direction θB). In addition, the pixel P 11  receives the light from the imaging optical system  10  via the spectral filter element  132 D (transmission wavelength characteristic D) and the polarizing filter element  122 A (polarization direction θA). In addition, the pixel P 12  receives the light from the imaging optical system  10  via the spectral filter element  132 D (transmission wavelength characteristic D) and the polarizing filter element  122 B (polarization direction θB). In addition, the pixel P 13  receives the light from the imaging optical system  10  via the spectral filter element  132 C (transmission wavelength characteristic C) and the polarizing filter element  122 C (polarization direction θC). In addition, the pixel P 14  receives the light from the imaging optical system  10  via the spectral filter element  132 C (transmission wavelength characteristic C) and the polarizing filter element  122 D (polarization direction θD). In addition, the pixel P 15  receives the light from the imaging optical system  10  via the spectral filter element  132 D (transmission wavelength characteristic D) and the polarizing filter element  122 C (polarization direction θC). In addition, the pixel P 16  receives the light from the imaging optical system  10  via the spectral filter element  132 D (transmission wavelength characteristic D) and the polarizing filter element  122 D (polarization direction θD). 
     In this way, the pixels P 1  to P 16  receive the light having different characteristics (wavelength ranges and polarization directions), respectively, by having different optical characteristics from each other. That is, the pixels P 1  to P 16  constitute a plurality of pixel groups that selectively receive the light transmitted through any of the bandpass filters  50 A to  50 D (plurality of optical filters) by the spectral filter elements and the polarizing filter elements. 
     &lt;Configuration of Signal Processing Unit&gt; 
     The signal processing unit  200  (signal processing unit) processes the signals output from the imaging element  100  to generate image data of the multispectral image of four bands. That is, pieces of image data of four types of wavelength ranges λ 1  to λ 4  (a plurality of images corresponding to the wavelength ranges of the plurality of optical filters) transmitted through the bandpass filter unit  16  described above are generated. 
       FIG. 19  is a block diagram showing a schematic configuration of a signal processing unit. As shown in  FIG. 19 , the signal processing unit  200  includes an analog signal processing unit  200 A, an image generation unit  200 B, and a coefficient storage unit  200 C. The analog signal processing unit  200 A takes in an analog pixel signal output from each pixel of the imaging element  100 , performs signal processing (for example, sampling two correlation pile processing, amplification processing, and the like), then converts the processed pixel signal into a digital signal, and then outputs the converted digital signal. The image generation unit  200 B performs signal processing on the pixel signal after being converted into the digital signal to generate the image data of each of the wavelength ranges (λ 1  to λ 4 ). 
       FIG. 20  is a conceptual diagram of image generation. Each pixel block PB (X,Y) includes 16 pixels P 1  to P 16 , as described above. Therefore, 16 pieces of image data D 1  to D 16  are generated by separating and extracting the pixel signals of the pixels P 1  to P 16  from each pixel block PB (X,Y). However, interference (crosstalk) has occurred in these 16 pieces of image data D 1  to D 16 . That is, since the light in each wavelength range is incident on each of the pixels P 1  to P 16 , the generated image is an image in which images of the wavelength ranges are mixed. Therefore, the image generation unit  200 B performs interference removal processing to generate the image data of each of the wavelength ranges (λ 1  to λ 4 ). 
     Hereinafter, the interference removal processing performed by the signal processing unit  200  will be described. 
     The pixel signal (signal value) obtained by the pixel P 1  of each pixel block PB (X,Y) is referred to as α 1 , and the pixel signals obtained by the pixels P 2  to P 16  are referred to as α 2  to α 16 , respectively, in the same manner. Then, 16 pixel signals α 1  to α 16  can be obtained from each pixel block PB (X,Y). The image generation unit  200 B calculates four pixel signals β 1  to β 4  corresponding to the light in the wavelength ranges λ 1  to λ 4  from 16 pixel signals α 1  to α 16 , and removes interference. Specifically, the image generation unit  200 B calculates four pixel signals β 1  to β 4  corresponding to the light in the wavelength ranges λ 1  to λ 4  via Equation 1 using the following matrix A, and removes the interference. 
     
       
         
           
             
               
                 
                   A 
                   = 
                   
                     
                       
                         [ 
                         
                           
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 11 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 12 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 13 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 14 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 15 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 16 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 17 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 18 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 19 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 110 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 111 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 112 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 113 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 114 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 115 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 116 
                               
                             
                           
                           
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 21 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 22 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 23 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 24 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 25 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 26 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 27 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 28 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 29 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 210 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 211 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 212 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 213 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 214 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 215 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 216 
                               
                             
                           
                           
                             
                               
                                 a 
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                                 ⁢ 
                                 31 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 32 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 33 
                               
                             
                             
                               
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                                 ⁢ 
                                 34 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 35 
                               
                             
                             
                               
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                                 ⁢ 
                                 36 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 37 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 38 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 39 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 310 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 311 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 312 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 313 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 314 
                               
                             
                             
                               
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                                 ⁢ 
                                 315 
                               
                             
                             
                               
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                                 ⁢ 
                                 316 
                               
                             
                           
                           
                             
                               
                                 a 
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                                 ⁢ 
                                 41 
                               
                             
                             
                               
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                                 ⁢ 
                                 42 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 43 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 44 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 45 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 46 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 47 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 48 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 49 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 410 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 411 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 412 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 413 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 414 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 415 
                               
                             
                             
                               
                                 a 
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                                 416 
                               
                             
                           
                         
                         ] 
                       
                       ⁢ 
                       
                         
 
                       
                       [ 
                       
                         
                           
                             β1 
                           
                         
                         
                           
                             β2 
                           
                         
                         
                           
                             β3 
                           
                         
                         
                           
                             β4 
                           
                         
                       
                       ] 
                     
                     = 
                     
                       
                         [ 
                         
                           
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 11 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 12 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 13 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 14 
                               
                             
                             
                               
                                 a 
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                                 ⁢ 
                                 15 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 16 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 17 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 18 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 19 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 110 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 111 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 112 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 113 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 114 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 115 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 116 
                               
                             
                           
                           
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 21 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 22 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 23 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 24 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 25 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 26 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 27 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 28 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 29 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 210 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 211 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 212 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 213 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 214 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 215 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 216 
                               
                             
                           
                           
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 31 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 32 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 33 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 34 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 35 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 36 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 37 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 38 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 39 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 310 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 311 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 312 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 313 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 314 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 315 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 316 
                               
                             
                           
                           
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 41 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 42 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 43 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 44 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 45 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 46 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 47 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 48 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 49 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 410 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 411 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 412 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 413 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 414 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 415 
                               
                             
                             
                               
                                 a 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 416 
                               
                             
                           
                         
                         ] 
                       
                       * 
                       
                         [ 
                         
                           
                             
                               α1 
                             
                           
                           
                             
                               α2 
                             
                           
                           
                             
                               α3 
                             
                           
                           
                             
                               α4 
                             
                           
                           
                             
                               α5 
                             
                           
                           
                             
                               α6 
                             
                           
                           
                             
                               α7 
                             
                           
                           
                             
                               α8 
                             
                           
                           
                             
                               α9 
                             
                           
                           
                             
                               α10 
                             
                           
                           
                             
                               α11 
                             
                           
                           
                             
                               α12 
                             
                           
                           
                             
                               α13 
                             
                           
                           
                             
                               α14 
                             
                           
                           
                             
                               α15 
                             
                           
                           
                             
                               α16 
                             
                           
                         
                         ] 
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
               
             
           
         
       
     
     Note that the pixel signal β 1  is the pixel signal corresponding to the light in the wavelength range λ 1 , the pixel signal β 2  is the pixel signal corresponding to the light in the wavelength range λ 2 , the pixel signal β 3  is the pixel signal corresponding to the light in the wavelength range λ 3 , and the pixel signal β 4  is the pixel signal corresponding to the light in the wavelength range λ 4 . Therefore, the image data of the wavelength range λ 1  is generated from the pixel signal β 1 , the image data of the wavelength range λ 2  is generated from the pixel signal β 2 , the image data of the wavelength range λ 3  is generated from the pixel signal β 3 , and the image data of the wavelength range λ 4  is generated from the pixel signal β 4 . Hereinafter, the reason why the interference can be removed by the above-mentioned Equation 1 will be described. 
     The interference occurs by the light in each of the wavelength ranges λ 1  to λ 4  being mixed into each of the pixels P 1  to P 16 . A ratio (interference ratio) at which the light in each of the wavelength ranges λ 1  to λ 4  emitted from the imaging optical system  10  is received by each of the pixels P 1  to P 16  is bij (i=1 to 16, j=1 to 4). For example, b 11  is a ratio of the light in the wavelength range λ 1  received by the pixel P 1 , b 12  is a ratio of the light in the wavelength range λ 2  received by the pixel P 1 , b 13  is a ratio of the light in the wavelength range λ 3  received by the pixel P 1 , and b 14  is a ratio of the light in the wavelength range λ 4  received by the pixel P 1 . In the following description, b 21  to b 164  are defined below in the same manner. This ratio bij (b 11  to b 164 ) can be determined in advance by unique determination from setting of the wavelength ranges λ 1  to λ 4  of the light transmitted through the bandpass filters  50 A to  50 D of the bandpass filter unit  16 , setting of the polarization directions θ 1  to θ 4  of the light transmitted by the polarizing filters  21 A to  21 D, setting of the transmission wavelength characteristics A to D (see  FIG. 18 ) of each of the pixels P 1  to P 16  of the imaging element  100 , and setting of the polarization directions θA to θC (see  FIG. 16 ) of the light received by the pixels P 1  to P 16  of the imaging element  100 . 
     The following relationship is satisfied between the pixel signals α 1  to α 16  obtained by the pixels P 1  to P 16  of each pixel block PB (X,Y) and the pixel signals β 1  to β 4  corresponding to the light in the wavelength ranges λ 1  to λ 4 . 
     Regarding the pixel signal α 1  obtained by the pixel P 1 , “b 11 *β 1 +b 12 *β 2 +b 13 *β 3 +b 14 *β 4 =α 1  . . . Equation 2” is satisfied (“*” is a symbol of integration). 
     Regarding the pixel signal α 2  obtained by the pixel P 2 , “b 21 *β 1 +b 22 *β 2 +b 23 *β 3 +b 24 *β 4 =α 2  . . . Equation 3” is satisfied. 
     Regarding the pixel signal α 3  obtained by the pixel P 3 , “b 31 *β 1 +b 32 *β 2 +b 33 *β 3 +b 34 *β 4 =α 3  . . . Equation 4” is satisfied. 
     Regarding the pixel signal α 4  obtained by the pixel P 4 , “b 41 *β 1 +b 42 *β 2 +b 43 *β 3 +b 44 *β 4 =α 4  . . . Equation 5” is satisfied. 
     Regarding the pixel signal α 5  obtained by the pixel P 5 , “b 51 *β 1 +b 52 *β 2 +b 53 *β 3 +b 54 *β 4 =α 5  . . . Equation 6” is satisfied. 
     Regarding the pixel signal α 6  obtained by the pixel P 6 , “b 61 *β 1 +b 62 *β 2 +b 63 *β 3 +b 64 *β 4 =α 6  . . . Equation 7” is satisfied. 
     Regarding the pixel signal α 7  obtained by the pixel P 7 , “b 71 *β 1 +b 72 *β 2 +b 73 *β 3 +b 74 *β 4 =α 7  . . . Equation 8” is satisfied. 
     Regarding the pixel signal α 8  obtained by the pixel P 8 , “b 81 *β 1 +b 82 *β 2 +b 83 *β 3 +b 84 *β 4 =α 8  . . . Equation 9” is satisfied. 
     Regarding the pixel signal α 9  obtained by the pixel P 9 , “b 91 *β 1 +b 92 *β 2 +b 93 *β 3 +b 94 *β 4 =α 9  . . . Equation 10” is satisfied. 
     Regarding the pixel signal α 10  obtained by the pixel P 10 , “b 101 *β 1 +b 102 *β 2 +b 103 *β 3 +b 104 *β 4 =α 10  . . . Equation 11” is satisfied. 
     Regarding the pixel signal α 11  obtained by the pixel P 11 , “b 111 *β 1 +b 112 *β 2 +b 113 *β 3 +b 114 *β 4 =α 11  . . . Equation 12” is satisfied. 
     Regarding the pixel signal α 12  obtained by the pixel P 12 , “b 121 *β 1 +b 122 *β 2 +b 123 *β 3 +b 124 *β 4 =α 12  . . . Equation 13” is satisfied. 
     Regarding the pixel signal α 13  obtained by the pixel P 13 , “b 131 *β 1 +b 132 *β 2 +b 133 *β 3 +b 134 *β 4 =α 13  . . . Equation 14” is satisfied. 
     Regarding the pixel signal α 14  obtained by the pixel P 14 , “b 141 *β 1 +b 142 *β 2 +b 143 *β 3 +b 144 *β 4 =α 14  . . . Equation 15” is satisfied. 
     Regarding the pixel signal α 15  obtained by the pixel P 15 , “b 151 *β 1 +b 152 *β 2 +b 153 *β 3 +b 154 *β 4 =α 15  . . . Equation 16” is satisfied. 
     Regarding the pixel signal α 16  obtained by the pixel P 16 , “b 161 *β 1 +b 162 *β 2 +b 163 *β 3 +b 164 *β 4 =α 16  . . . Equation 17” is satisfied. 
     Here, the simultaneous equations of Equations 2 to 17 can be expressed by Equation 18 using a matrix B. 
     
       
         
           
             
               
                 
                   B 
                   = 
                   
                     
                       
                         
                           [ 
                           
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   11 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   12 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   13 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   14 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   21 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   22 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   23 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   24 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   31 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   32 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   33 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   34 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   41 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   42 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   43 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   44 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   51 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   52 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   53 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   54 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   61 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   62 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   63 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   64 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   71 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   72 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   73 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   74 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   81 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   82 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   83 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   84 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   91 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   92 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   93 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   94 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   101 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   102 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   103 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   104 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   111 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   112 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   113 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   114 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   121 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   122 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   123 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   124 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   131 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   132 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   133 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   134 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   141 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   142 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   143 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   144 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   151 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   152 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   153 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   154 
                                 
                               
                             
                             
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   161 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   162 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   163 
                                 
                               
                               
                                 
                                   b 
                                   ⁢ 
                                   
                                       
                                   
                                   ⁢ 
                                   164 
                                 
                               
                             
                           
                           ] 
                         
                         ⁢ 
                         
                           
 
                         
                         [ 
                         
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 11 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 12 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 13 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 14 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 21 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 22 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 23 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 24 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 31 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 32 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 33 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 34 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 41 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 42 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 43 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 44 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 51 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 52 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 53 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 54 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 61 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 62 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 63 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 64 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 71 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 72 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 73 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 74 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 81 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 82 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 83 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 84 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 91 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 92 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 93 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 94 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 101 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 102 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 103 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 104 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 111 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 112 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 113 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 114 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 121 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 122 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 123 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 124 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 131 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 132 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 133 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 134 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 141 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 142 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 143 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 144 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 151 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 152 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 153 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 154 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 161 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 162 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 163 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 164 
                               
                             
                           
                         
                         ] 
                       
                       * 
                       
                         [ 
                         
                           
                             
                               β1 
                             
                           
                           
                             
                               β2 
                             
                           
                           
                             
                               β3 
                             
                           
                           
                             
                               β4 
                             
                           
                         
                         ] 
                       
                     
                     = 
                     
                       [ 
                       
                         
                           
                             α1 
                           
                         
                         
                           
                             α2 
                           
                         
                         
                           
                             α3 
                           
                         
                         
                           
                             α4 
                           
                         
                         
                           
                             α5 
                           
                         
                         
                           
                             α6 
                           
                         
                         
                           
                             α7 
                           
                         
                         
                           
                             α8 
                           
                         
                         
                           
                             α9 
                           
                         
                         
                           
                             α10 
                           
                         
                         
                           
                             α11 
                           
                         
                         
                           
                             α12 
                           
                         
                         
                           
                             α13 
                           
                         
                         
                           
                             α14 
                           
                         
                         
                           
                             α15 
                           
                         
                         
                           
                             α16 
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   18 
                 
               
             
           
         
       
     
     β 1  to β 4 , which are the solutions of the simultaneous equations of Equations 2 to 17, are calculated by multiplying both sides of Equation 18 by an inverse matrix B −1  of the matrix B. 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           β1 
                         
                       
                       
                         
                           β2 
                         
                       
                       
                         
                           β3 
                         
                       
                       
                         
                           β4 
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       
                         [ 
                         
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 11 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 12 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 13 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 14 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 21 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 22 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 23 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 24 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 31 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 32 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 33 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 34 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 41 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 42 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 43 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 44 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 51 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 52 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 53 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 54 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 61 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 62 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 63 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 64 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 71 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 72 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 73 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 74 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 81 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 82 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 83 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 84 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 91 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 92 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 93 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 94 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 101 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 102 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 103 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 104 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 111 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 112 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 113 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 114 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 121 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 122 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 123 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 124 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 131 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 132 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 133 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 134 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 141 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 142 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 143 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 144 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 151 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 152 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 153 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 154 
                               
                             
                           
                           
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 161 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 162 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 163 
                               
                             
                             
                               
                                 b 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 164 
                               
                             
                           
                         
                         ] 
                       
                       
                         - 
                         1 
                       
                     
                     * 
                     
                       [ 
                       
                         
                           
                             α1 
                           
                         
                         
                           
                             α2 
                           
                         
                         
                           
                             α3 
                           
                         
                         
                           
                             α4 
                           
                         
                         
                           
                             α5 
                           
                         
                         
                           
                             α6 
                           
                         
                         
                           
                             α7 
                           
                         
                         
                           
                             α8 
                           
                         
                         
                           
                             α9 
                           
                         
                         
                           
                             α10 
                           
                         
                         
                           
                             α11 
                           
                         
                         
                           
                             α12 
                           
                         
                         
                           
                             α13 
                           
                         
                         
                           
                             α14 
                           
                         
                         
                           
                             α15 
                           
                         
                         
                           
                             α16 
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   19 
                 
               
             
           
         
       
     
     In this way, the pixel signals β 1  to β 4  corresponding to the wavelength ranges λ 1  to λ 4  can be calculated from the signal values (pixel signals α 1  to α 16 ) of the pixels P 1  to P 16  based on the ratio in which the light in the wavelength ranges λ 1  to λ 4  emitted from the imaging optical system  10  is received by the pixels P 1  to P 16  of the pixel block PB (X,Y). 
     In Equation 1, the inverse matrix B −1  of Equation 19 is set to A (B −1 =A). Therefore, elements aij of the matrix A in Equation 1 can be acquired by obtaining the inverse matrix B −1  of the matrix B. 
     The coefficient storage unit  200 C stores the elements aij of the matrix A for performing the interference removal processing, as a coefficient group. 
     &lt;Light Screen&gt; 
     Each element of the matrix A can be calculated from the result of imaging by inserting any of the light screens shown in  FIGS. 21A to 21D  into the optical path of the imaging optical system  10 . A light screen  40  shown in  FIG. 21A  has an aperture  40 A at a portion corresponding to the bandpass filter  50 A (see  FIG. 2A ) mounted on the bandpass filter unit  16 , and the other portions corresponding to the other bandpass filters  50 B to  50 D are shielded. Similarly, a light screen  42  shown in  FIG. 21B  has an aperture  42 B at a portion corresponding to the bandpass filter  50 B, and the other portions corresponding to the bandpass filters  50 A,  50 C, and  50 D are shielded. Further, a light screen  44  shown in  FIG. 21C  has an aperture  44 C at a portion corresponding to the bandpass filter  50 C, and the other portions corresponding to the bandpass filters  50 A,  50 B, and  50 D are shielded. A light screen  46  shown in  FIG. 21D  has an aperture  46 D at a portion corresponding to the bandpass filter  50 D, and the other portions corresponding to the bandpass filters  50 A to  50 C are shielded. 
     The image generation unit  200 B acquires the coefficient group from the coefficient storage unit  200 C, calculates the pixel signals β 1  to β 4  corresponding to the wavelength ranges λ 1  to λ 4  via Equation 1 from the pixel signals α 1  to α 16  obtained from the pixels P 1  to P 16  of each pixel block PB (X,Y), and generates the image data of the wavelength ranges λ 1  to λ 4 . 
     The image data of the wavelength ranges λ 1  to λ 4  generated by the image generation unit  200 B are output to the outside and stored in a storage device (not shown), as needed. In addition, the image data is displayed on a display (not shown), as needed. 
     &lt;Image Generation&gt; 
       FIG. 22  is a conceptual diagram of the image generation by the imaging apparatus  1 . 
     The light beams incident on the imaging optical system  10  become four types of the light having different characteristics, which are incident on the imaging element  100 . Specifically, the light beams become light (first light) of the polarization direction θ 1  and the wavelength range  1 , light (second light) of the polarization direction θ 2  and the wavelength range λ 2 , light (third light) of the polarization direction θ 3  and the wavelength range λ 3 , and light (fourth light) of the polarization direction θ 4  and the wavelength range λ 4 , which are incident on the imaging element  100 . 
     In each pixel block PB (X,Y) of the imaging element  100 , the light in each of the wavelength ranges emitted from the imaging optical system  10  is received in each of the pixels P 1  to P 16  at the ratio bij described above. That is, the light in each of the wavelength ranges λ 1  to λ 4  is received at the ratio bij by the actions of the polarizing filter elements  122 A to  122 D and the spectral filter elements  132 A to  132 D provided in each of the pixels P 1  to P 16 . 
     The signal processing unit  200  calculates the pixel signals β 1  to β 4  corresponding to the light in the wavelength ranges λ 1  to λ 4  from the pixel signals α 1  to α 16  obtained from the pixels P 1  to P 16  of each pixel block PB (X,Y) of the imaging element  100 , and generates the image data of the wavelength ranges λ 1  to λ 4 . That is, the signal processing unit  200  performs arithmetic processing (interference removal processing) via Equation 1 using the matrix A, calculates the pixel signals β 1  to β 4  corresponding to the light in the wavelength ranges λ 1  to λ 4  from the pixel signals α 1  to α 16  of the pixels P 1  to P 16  obtained from the imaging element  100 , and generates the image data of the wavelength ranges λ 1  to λ 4 . 
     In this way, with the imaging apparatus  1  according to the first embodiment, the image of four types of different wavelength ranges (multispectral image of four bands) can be captured by using one imaging optical system  10  and one (single plate) imaging element  100 . 
     Modification Example 
     A modification example of the imaging apparatus  1  according to the first embodiment described above will be described. 
     Another Example (No. 1) of Bandpass Filter Unit 
       FIGS. 23A and 23B  are diagrams showing another example (No. 1) of the bandpass filter unit. In an aspect shown in  FIGS. 23A and 23B , in a bandpass filter unit  22 , two of each of bandpass filters  22 R,  22 G,  22 C, and  22 M (a plurality of bandpass filters) having different wavelength ranges of transmitted light are mounted on a frame  23  (see  FIG. 23A ). The frame  23  is provided with two of each of circular aperture regions  23 R,  23 G,  23 C, and  23 M (see  FIG. 23B ). The aperture regions are arranged symmetrically with respect to a centroid  23 P of the frame  23 . Further, for each wavelength range, a plurality of bandpass filters having the same wavelength range are mounted in the plurality of aperture regions, respectively. In  FIGS. 23A and 23B , the aperture region and the bandpass filter have the same shape and area regardless of the transmission wavelength range, but the area may correspond to the transmission wavelength range as in the first embodiment. 
     The bandpass filter unit of the aspect shown in  FIGS. 23A and 23B  has features such as “the centroid of the aperture region for each color (frequency range of transmitted light) does not shift”, “the luminous flux can be narrowed without shifting the centroid for each color”, “easy to manufacture”, “easy to perform aberration correction for each color”, “easy to acquire an interference removal matrix”, and “rotationally symmetric”. 
     Another Example (No. 2) of Bandpass Filter Unit 
       FIGS. 24A and 24B  are diagrams showing another example (No. 2) of the bandpass filter unit. In an aspect shown in  FIGS. 24A and 24B , in a bandpass filter unit  24 , a basic pattern  26  of the bandpass filter is mounted on a frame  25  repeatedly in the horizontal direction and the vertical direction, in  FIGS. 24A and 24B  (16 in total; see  FIG. 24A ). As shown in  FIG. 24B , the basic pattern  26  is composed of four bandpass filters  26 R,  26 G,  26 C, and  26 M having different wavelength ranges of transmitted light. Although the illustration of the aperture region is omitted in the aspect shown in  FIGS. 24A and 24B , the aperture region has a disposition, shape, and size corresponding to the arrangement of the bandpass filters. As in the first embodiment, a bandpass filter having a longer wavelength at the center of the wavelength range of transmitted light may be mounted in an aperture region having a larger aperture area. 
     The bandpass filter unit of the aspect shown in  FIGS. 24A and 24B  has features such as “the centroid of the aperture region for each color (frequency range of transmitted light) does not shift”, “the luminous flux can be reduced without shifting the centroid for each color”, “the edge part light quantity for each color is symmetrical”, and “rotationally symmetric”. 
     Another Example (No. 3) of Bandpass Filter Unit 
       FIG. 25  is a diagram showing another example (No. 3) of the bandpass filter unit. In an aspect shown in  FIG. 25 , in a bandpass filter unit  27 , two of each of fan-shaped bandpass filters  27 R,  27 G,  27 C, and  27 M having different wavelength ranges of transmitted light are mounted on a frame  28 . The bandpass filters are mounted in aperture regions (not shown) arranged symmetrically with respect to a centroid  28 G of the frame  28 . The area of the bandpass filter  27 R is the largest among the bandpass filters (and corresponding aperture regions). The aperture region and the bandpass filter can have an area corresponding to the transmission wavelength range, as in the first embodiment and “another example (No. 2)”. 
     Another Example (No. 4) of Bandpass Filter Unit 
     In the first embodiment described above and the aspects of  FIGS. 23A to 25 , the bandpass filter unit has four types of bandpass filters having different wavelength ranges of transmitted light. However, in the optical element according to the embodiment of the present invention, the wavelength range of the bandpass filter unit is not limited to four types. In another example (No. 4) of the bandpass filter unit shown in  FIGS. 26A to 26C , the bandpass filter unit has three types of bandpass filters. 
     In the bandpass filter unit  30  shown in  FIG. 26A , bandpass filters  30 R,  30 G, and  30 C having different wavelength ranges of transmitted light are mounted on a frame  31  (one bandpass filter  30 R and two of each of bandpass filters  30 G and  30 C). The area of the bandpass filter  30 R is the largest, and the areas of the bandpass filters  30 G and  30 C are narrower than that of the bandpass filter  30 R (the areas of the bandpass filters  30 G and  30 C are the same). The bandpass filter  30 R is mounted in a single aperture region (not shown) surrounding a centroid  31 G of the frame  31 , and the bandpass filters  30 G and  30 C are mounted in a plurality of aperture regions (not shown) arranged symmetrically with respect to the centroid  31 G. In addition, also in the aspect shown in  FIG. 26A , the bandpass filter may be mounted in an aperture region having an aperture area corresponding to the wavelength range. Further, the bandpass filters may be mounted such that a bandpass filter having a longer wavelength at the center of the wavelength range is mounted in an aperture region having a larger aperture area. Further, the bandpass filters may be mounted such that a bandpass filter mounted farther from the centroid  31 G (feature point) of the frame  31  is mounted in the aperture region having a narrower aperture area. 
     The bandpass filter unit of the aspect shown in  FIG. 26A  has features such as “the centroid of the aperture region for each color (frequency range of transmitted light) does not shift”, “the luminous flux can be narrowed without shifting the centroid for each color”, “easy to manufacture”, “easy to perform aberration correction for each color”, and “easy to acquire an interference removal matrix”. 
     In a bandpass filter unit  32  shown in  FIG. 26B , bandpass filters  32 R,  32 G, and  32 C having different wavelength ranges of transmitted light are mounted on a frame  33 . Also in the aspect shown in  FIG. 26B , the bandpass filter may be mounted in an aperture region having an aperture area corresponding to the wavelength range. Further, as in the above-described aspect, the bandpass filters may be mounted such that a bandpass filter having a longer wavelength at the center of the wavelength range is mounted in an aperture region having a larger aperture area. Further, the bandpass filters may be mounted such that a bandpass filter mounted farther from a centroid  33 G (feature point) of the frame  33  is mounted in the aperture region having a narrower aperture area. 
     The bandpass filter unit of the aspect shown in  FIG. 26B  has features such as “the centroid of the aperture region for each color (frequency range of transmitted light) does not shift”, “the edge part light quantity for each color is symmetrical”, and “rotationally symmetric”. 
     In a bandpass filter unit  34  shown in  FIG. 26C , bandpass filters  34 R,  34 G, and  34 C having different wavelength ranges of transmitted light are mounted on a frame  35  (one bandpass filter  34 R, three bandpass filters  34 G, and three bandpass filters  34 C). The bandpass filter  34 R is mounted in a single aperture region (not shown) surrounding a centroid  35 G of the frame  35 , and the bandpass filters  34 G and  34 C are mounted in a plurality of aperture regions (not shown) arranged symmetrically with respect to the centroid  35 G. Similarly to the above-described aspect, also in an aspect shown in  FIG. 26B , the bandpass filter may be mounted in an aperture region having an aperture area corresponding to the wavelength range. Further, the bandpass filters may be mounted such that a bandpass filter having a longer wavelength at the center of the wavelength range is mounted in an aperture region having a larger aperture area. 
     The bandpass filter unit of the aspect shown in  FIG. 26C  has features such as “the centroid of the aperture region for each color (frequency range of transmitted light) does not shift”, “easy to perform aberration correction for each color”, “the edge part light quantity for each color is symmetrical”, and “rotationally symmetric”. 
     Another Example (No. 5) of Bandpass Filter Unit 
       FIGS. 27A and 27B  are diagrams showing another example (No. 5) of the disposition of the aperture region and the filter. In an aspect shown in  FIGS. 27A and 27B , two of each of bandpass filters  36 R,  36 G,  36 C, and  36 M (a plurality of bandpass filters) having different wavelength ranges of transmitted light are mounted in a bandpass filter unit  36 . The bandpass filter unit  36  has a frame  37 , and the frame  37  is provided with two of each of aperture regions  37 R,  37 G,  37 C, and  37 M having different aperture shapes. The aperture regions are arranged symmetrically with respect to a centroid  37 P of the frame  37 . The bandpass filters  36 R,  36 G,  36 C, and  36 M have different shapes for each wavelength range, the shapes corresponding to the aperture shapes of the aperture regions  37 R,  37 G,  37 C, and  37 M. By making the shapes of the aperture regions and the bandpass filters different for each wavelength range of transmitted light in this way, the probability that the bandpass filter is mounted in an inappropriate aperture region can be reduced, and assembly can be facilitated. 
     As in the first embodiment, even in the case of the bandpass filter units of the aspects shown in  FIGS. 23A to 27B , it is possible to suppress the image shift at the time of defocus and to acquire a multispectral image with a good image quality. The polarizing filter unit (not shown) can be used for the other examples (No. 1 to No. 5) as in the case of the first embodiment. It is desirable that the polarizing filter (not shown) mounted on the polarizing filter unit also has a disposition, shape, and size corresponding to the shapes of the aperture regions and of the bandpass filters. 
     Application of Present Invention 
     The optical element, the optical device, and the imaging apparatus according to the embodiment of the present invention can be applied to a general single-lens type or compact type digital camera, a digital camera used in a measuring device or an inspection device, and a digital camera included in a smartphone, a mobile phone, a tablet terminal, or the like. 
     Although the embodiment of the present invention and other examples have been described above, it is needless to say that the present invention is not limited to the aspect described above, and various modifications can be made without departing from the gist of the present invention. 
     EXPLANATION OF REFERENCES 
     
         
         
           
               1 : imaging apparatus 
               10 : imaging optical system 
               12 : lens 
               16 : bandpass filter unit 
               18 : polarizing filter unit 
               19 : frame 
               19 A: aperture region 
               19 B: aperture region 
               19 C: aperture region 
               19 D: aperture region 
               19 G: centroid 
               20 : frame 
               20 G: centroid 
               21 A: polarizing filter 
               21 B: polarizing filter 
               21 C: polarizing filter 
               21 D: polarizing filter 
               22 : bandpass filter unit 
               22 C: bandpass filter 
               22 G: bandpass filter 
               22 M: bandpass filter 
               22 R: bandpass filter 
               23 : frame 
               23 C: aperture region 
               23 G: aperture region 
               23 M: aperture region 
               23 P: centroid 
               23 R: aperture region 
               24 : bandpass filter unit 
               25 : frame 
               26 : basic pattern 
               26 C: bandpass filter 
               26 G: bandpass filter 
               26 M: bandpass filter 
               26 R: bandpass filter 
               27 : bandpass filter unit 
               27 C: bandpass filter 
               27 G: bandpass filter 
               27 M: bandpass filter 
               27 R: bandpass filter 
               28 : frame 
               28 G: centroid 
               30 : bandpass filter unit 
               30 C: bandpass filter 
               30 G: bandpass filter 
               30 R: bandpass filter 
               31 : frame 
               31 G: centroid 
               32 : bandpass filter unit 
               32 C: bandpass filter 
               32 G: bandpass filter 
               32 R: bandpass filter 
               33 : frame 
               33 G: centroid 
               34 : bandpass filter unit 
               34 C: bandpass filter 
               34 G: bandpass filter 
               34 R: bandpass filter 
               35 : frame 
               35 G: centroid 
               36 : bandpass filter unit 
               36 C: bandpass filter 
               36 G: bandpass filter 
               36 M: bandpass filter 
               36 R: bandpass filter 
               37 : frame 
               37 C: aperture region 
               37 G: aperture region 
               37 M: aperture region 
               37 P: centroid 
               37 R: aperture region 
               40 : light screen 
               40 A: aperture 
               42 : light screen 
               42 B: aperture 
               44 : light screen 
               44 C: aperture 
               46 : light screen 
               46 D: aperture 
               50 A: bandpass filter 
               50 B: bandpass filter 
               50 C: bandpass filter 
               50 D: bandpass filter 
               52 A: aperture region 
               52 B: aperture region 
               52 C: aperture region 
               52 D: aperture region 
               90 : subject 
               90 B: bandpass filter 
               90 G: bandpass filter 
               90 M: bandpass filter 
               90 R: bandpass filter 
               91 : bandpass filter unit 
               92 : frame 
               93 : subject image 
               94 : subject image 
               94 B: subject image 
               94 G: subject image 
               94 M: subject image 
               94 R: subject image 
               95 : subject image 
               95 B: subject image 
               95 G: subject image 
               95 M: subject image 
               95 R: subject image 
               100 : imaging element 
               110 : pixel array layer 
               112 : photodiode 
               120 : polarizing filter element array layer 
               122 A: polarizing filter element 
               122 B: polarizing filter element 
               122 C: polarizing filter element 
               122 D: polarizing filter element 
               130 : spectral filter element array layer 
               132 A: spectral filter element 
               132 B: spectral filter element 
               132 C: spectral filter element 
               132 D: spectral filter element 
               140 : micro lens array layer 
               142 : micro lens 
               200 : signal processing unit 
               200 A: analog signal processing unit 
               200 B: image generation unit 
               200 C: coefficient storage unit 
               1001 : aperture 
               1001 G: centroid 
               1002 : aperture 
               1002 G: centroid 
               1003 : aperture 
               1003 G: centroid 
               1004 : aperture 
               1004 G: centroid 
               1005 : aperture 
               1005 G: centroid 
               1006 : aperture 
               1006 G: centroid 
               1007 : aperture 
               1007 G: centroid 
               1008 : aperture 
               1008 G: centroid 
               1009 : aperture 
               1009 G: centroid 
             A: transmission wavelength characteristic 
             B: transmission wavelength characteristic 
             C: transmission wavelength characteristic 
             D: transmission wavelength characteristic 
             D 1 : image data 
             D 2 : image data 
             D 3 : image data 
             D 4 : image data 
             D 5 : image data 
             D 6 : image data 
             D 7 : image data 
             D 8 : image data 
             D 9 : image data 
             D 10 : image data 
             D 11 : image data 
             D 12 : image data 
             D 13 : image data 
             D 14 : image data 
             D 15 : image data 
             D 16 : image data 
             L: optical axis 
             P 1 : pixel 
             P 2 : pixel 
             P 3 : pixel 
             P 4 : pixel 
             P 5 : pixel 
             P 6 : pixel 
             P 7 : pixel 
             P 8 : pixel 
             P 9 : pixel 
             P 10 : pixel 
             P 11 : pixel 
             P 12 : pixel 
             P 13 : pixel 
             P 14 : pixel 
             P 15 : pixel 
             P 16 : pixel 
             PB: pixel block 
             Z 1 : pupil region 
             Z 2 : pupil region 
             Z 3 : pupil region 
             Z 4 : pupil region 
             α 1 : pixel signal 
             α 2 : pixel signal 
             α 3 : pixel signal 
             α 4 : pixel signal 
             α 5 : pixel signal 
             α 6 : pixel signal 
             α 7 : pixel signal 
             α 8 : pixel signal 
             α 9 : pixel signal 
             α 10 : pixel signal 
             α 11 : pixel signal 
             α 12 : pixel signal 
             α 13 : pixel signal 
             α 14 : pixel signal 
             α 15 : pixel signal 
             α 16 : pixel signal 
             β 1 : pixel signal 
             β 2 : pixel signal 
             β 3 : pixel signal 
             θ 1 : polarization direction 
             θ 2 : polarization direction 
             θ 3 : polarization direction 
             θ 4 : polarization direction 
             θA: polarization direction 
             θB: polarization direction 
             θC: polarization direction 
             θD: polarization direction 
             λ 1 : wavelength range 
             λ 2 : wavelength range 
             λ 3 : wavelength range 
             λ 4 : wavelength range