Lens device, optical filter unit, and image pickup device

Abstract

Provided is a lens device, an optical filter unit, and an imaging device that can suppress the generation of ghost images. The lens device includes an optical filter unit in an optical path. The optical filter unit includes a plurality of openings including a first opening and a second opening, at least the first opening and the second opening include a band-pass filter, and at least one of an object side and an image side of the band-pass filter includes an optical element. The optical element includes a polarizing filter and a wave plate that converts linearly polarized light into circularly polarized light or elliptically polarized light, and the first opening and the second opening pass light of mutually different wavelength regions and polarization directions.

Description

Technical Field

[0001] This invention relates to a lens device, a filter unit, and an imaging device, and more particularly to a lens device, a filter unit, and an imaging device for capturing images of light split into multiple wavelengths. Background Technology

[0002] Patent Document 1 describes an imaging device for capturing images that split light into multiple wavelengths. Patent Document 1 further describes an embodiment where, as embodiment 1, a light-absorbing filter is disposed between the lens optical system and the image sensor to absorb light reflected from the imaging surface of the image sensor. Also in Patent Document 1, as embodiment 2, a polarizer and a quarter-wave plate are used instead of the light-absorbing filter.

[0003] Previous technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-36127 Summary of the Invention

[0006] One embodiment of the present invention provides a lens device, a filter unit, and a camera device capable of suppressing ghosting.

[0007] means for solving technical problems

[0008] (1) A lens device having a filter unit in an optical path, wherein the filter unit has a plurality of openings including a first opening and a second opening, at least the first opening and the second opening have a bandpass filter, and at least one of the object side and the image side of the bandpass filter has an optical element, the optical element being composed of a polarizing filter and a waveplate that converts linearly polarized light into circularly polarized light or elliptically polarized light, the first opening and the second opening allowing light of different wavelength regions and polarization directions to pass through.

[0009] (2) According to the lens device in (1), the wave plate is a quarter-wave plate.

[0010] (3) The lens device according to (1) or (2), wherein the filter unit is disposed at or near the pupil position.

[0011] (4) The lens device according to any one of (1) to (3), wherein, when the optical element is disposed on the image side of the bandpass filter, or on the object side and the image side, at least one of the first opening and the second opening further comprises a half-wave plate on the image side of the optical element disposed on the image side of the bandpass filter.

[0012] (5) According to the lens device of (4), in the first opening and the second opening, the transmission axis angles of the polarizing filters of the optical elements disposed on the image side of the bandpass filter are equal.

[0013] (6) The lens device according to any one of (1) to (5), wherein, when the optical element is arranged on the object side and the image side of the bandpass filter, the angle of the fast axis of the waveplate is different on the object side and the image side of the bandpass filter.

[0014] (7) According to the lens arrangement of (6), the fast axis of the waveplate is orthogonal on the object side and the image side of the bandpass filter.

[0015] (8) The lens device according to any one of (1) to (3), wherein, when the optical element is disposed on the object side of the bandpass filter, the first opening and the second opening further provide polarizing filters on the image side of the bandpass filter.

[0016] (9) A lens device according to any one of (1) to (8), wherein the polarizing filter is an absorption polarizing filter.

[0017] (10) A filter unit disposed in the optical path of a lens device, wherein the filter unit has a plurality of openings including a first opening and a second opening, at least the first opening and the second opening are provided with bandpass filters, and at least one of the object side and the image side of the bandpass filters is provided with an optical element, the optical element being composed of a polarizing filter and a waveplate that converts linearly polarized light into circularly polarized light or elliptically polarized light, and the first opening and the second opening allow light with different wavelength regions and polarization directions to pass through.

[0018] (11) According to the filter unit of (10), the waveplate is a quarter-wave plate.

[0019] (12) A camera device comprising: a lens device of any one of (1) to (9); and a polarization image sensor for receiving light passing through the lens device. Attached Figure Description

[0020] Figure 1 This is a diagram showing the general structure of a multispectral camera system.

[0021] Figure 2 This is a diagram showing the general structure of a filter unit.

[0022] Figure 3 This is a diagram showing an example of the polarizing filters present in each window.

[0023] Figure 4 This is a diagram showing an example of the polarizing filters present in each window.

[0024] Figure 5 This is a diagram showing an example of a quarter-wave plate in each window.

[0025] Figure 6 This is a diagram illustrating an example of the structure of the filter array present in each window.

[0026] Figure 7 This diagram illustrates the function of preventing re-reflection based on optical isolators.

[0027] Figure 8 This is a diagram illustrating an example of the configuration of pixels and polarizers in a polarization image sensor.

[0028] Figure 9 This is a diagram illustrating an example of the hardware structure of a signal processing device.

[0029] Figure 10 It is a block diagram of the functions of a signal processing device.

[0030] Figure 11 This is a diagram showing a variation of the filter group provided in each window.

[0031] Figure 12 This is a diagram showing the general structure of a filter unit.

[0032] Figure 13 This is a diagram illustrating an example of the structure of the filter array present in each window.

[0033] Figure 14 This diagram illustrates the function of preventing re-reflection based on the front and rear optical isolators.

[0034] Figure 15 This is a diagram showing a variation of the filter group provided in each window.

[0035] Figure 16 This is a diagram showing the general structure of a filter unit.

[0036] Figure 17 This is a diagram illustrating an example of the structure of the filter array present in each window.

[0037] Figure 18 This is a diagram showing a variation of the filter group provided in each window.

[0038] Figure 19 This diagram illustrates an example of the structure of a filter group in each window when optical isolators are placed before and after a bandpass filter.

[0039] Figure 20 This is a diagram showing the general structure of a filter unit.

[0040] Figure 21 This is a diagram illustrating an example of the structure of the filter array present in each window.

[0041] Figure 22 This is a diagram showing a variation of the filter group provided in each window.

[0042] Figure 23 This is a diagram illustrating an example of the structure of a filter unit used for imaging when the light is split into four wavelengths.

[0043] Figure 24 This is a diagram illustrating an example of the structure of the filter array present in each window.

[0044] Figure 25 This is another example of the shape of the window portion within a filter frame. Detailed Implementation

[0045] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0046] [First Implementation]

[0047] Here, we will describe an example of applying the present invention to a multispectral camera system. A multispectral camera system is a system that simultaneously captures images split into multiple wavelengths. Here, we will describe an example of simultaneously capturing images split into three wavelengths.

[0048] [Structure of a multispectral camera system]

[0049] Figure 1 This is a diagram showing the general structure of a multispectral camera system.

[0050] The multispectral camera system shown in the figure is a so-called polarization-based multispectral camera system. Polarization-based refers to a multispectral camera system that utilizes polarized light. As shown in the figure, the multispectral camera system 1 mainly consists of a multispectral camera 10 and a signal processing device 300. The multispectral camera 10 consists of a lens assembly 100 and a camera body 200. The multispectral camera 10 is an example of an imaging device.

[0051] [Lens Device]

[0052] like Figure 1 As shown, the lens device 100 includes multiple lens groups 110A, 110B and a filter unit 120.

[0053] Lens groups 110A and 110B each consist of at least one lens. Figure 1For simplicity, only two lens groups 110A and 110B are shown in the diagram. Hereinafter, as needed, the lens group 110A, located on the front side of the filter unit 120, will be designated as the first lens group, and the lens group 110B, located on the rear side of the filter unit 120, will be designated as the second lens group to distinguish between the two lens groups 110A and 110B. Furthermore, "front side" refers to the "object side," and "rear side" refers to the "image side."

[0054] The filter unit 120 is disposed in the optical path. More specifically, the filter unit 120 is disposed at or near the pupil position in the lens device 100. Furthermore, "near the pupil position" refers to a region that satisfies the following formula.

[0055] |d|<φ / (2tanθ)

[0056] θ: The maximum principal ray angle at the pupil position (the principal ray angle is the angle with respect to the optical axis).

[0057] φ: Pupil diameter

[0058] |d|: Distance from the pupil

[0059] Figure 2 This is a diagram showing the general structure of a filter unit.

[0060] The filter unit 120 consists of a filter frame 122 and three filter groups 124A, 124B and 124C installed in the filter frame 122.

[0061] The filter frame 122 has a plate-like shape corresponding to the inner circumferential shape of the lens barrel, and has multiple windows. For example... Figure 2 As shown, the filter frame 122 of this embodiment has a disk shape and has three windows 122A, 122B and 122C.

[0062] Three windows 122A, 122B, and 122C are formed by circular openings and are arranged at equal intervals along the circumference. Windows 122A, 122B, and 122C are examples of openings. Hereinafter, as needed, window 122A will be designated as the first window, window 122B as the second window, and window 122C as the third window to distinguish the windows 122A, 122B, and 122C. Window 122A is an example of the first opening. Window 122B is an example of the second opening.

[0063] In each of the three windows 122A, 122B, and 122C, a filter assembly 124A, 124B, and 124C is installed separately.

[0064] The three filter groups 124A, 124B, and 124C each consist of three filters. These three filters are: band-pass filters (BPF) 124A1, 124B1, 124C1; quarter-wave plates (QWP) 124A2, 124B2, 124C2; and polarized light filters (PLF) 124A3, 124B3, 124C3. The three filters are arranged along the optical axis Z from the object side in the following order: band-pass filters 124A1, 124B1, 124C1; quarter-wave plates 124A2, 124B2, 124C2; and polarized light filters 124A3, 124B3, 124C3.

[0065] The three windows 122A, 122B, and 122C each have bandpass filters 124A1, 124B1, and 124C1 for different transmission wavelength regions. The bandpass filter 124A1 in the first window 122A allows light in the first wavelength region λ1 to pass through. The bandpass filter 124B1 in the second window 122B allows light in the second wavelength region λ2 (λ2≠λ1) to pass through. The bandpass filter 124C1 in the third window 122C allows light in the third wavelength region λ3 (λ3≠λ1, λ3≠λ2) to pass through.

[0066] From the perspective of the degree of freedom of spectral transmission characteristics, reflective bandpass filters are preferred among bandpass filters 124A1, 124B1, and 124C1.

[0067] The three windows 122A, 122B, and 122C each contain polarizing filters 124A3, 124B3, and 124C3 with different transmission axis angles. In the first window 122A, the transmission axis of the polarizing filter 124A3 is set to the first angle θA. In the second window 122B, the transmission axis of the polarizing filter 124B3 is set to the second angle θB (θB≠θA). In the third window 122C, the transmission axis of the polarizing filter 124C3 is set to the third angle θC (θC≠θA).

[0068] Figure 3 This diagram shows an example of the polarizing filters included in each window. The diagram shows the transmission axis settings of each polarizing filter 124A3, 124B3, and 124C3 when the filter unit 120 is viewed from the object side (front side).

[0069] As shown in the figure, in the filter unit 120 of this embodiment, the transmission axis of the polarizing filter 124A3 provided in the first window 122A is set to θA = 0°, the transmission axis of the polarizing filter 124B3 provided in the second window 122B is set to θB = 60°, and the transmission axis of the polarizing filter 124C3 provided in the third window 122C is set to θC = 120°.

[0070] Furthermore, regarding angles, the state parallel to the X-axis is set to 0°, and the counterclockwise direction is set to positive (+) when viewed from the object's side (front side). Therefore, a transmission axis of 60° refers to a state tilted 60° counterclockwise relative to the X-axis. And a transmission axis of 120° refers to a state tilted 120° counterclockwise relative to the X-axis.

[0071] The X-axis is an axis set in a plane orthogonal to the optical axis Z. In the plane orthogonal to the optical axis Z, an axis orthogonal to the X-axis is designated as the Y-axis. As described later, the image sensor in the camera body 200 has its upper and lower edges of the light-receiving surface arranged parallel to the X-axis. Furthermore, its left and right edges are arranged parallel to the Y-axis.

[0072] Furthermore, as will be described later, from the viewpoint of suppressing ghosting, absorption-type polarizing filters are preferably used among polarizing filters 124A3, 124B3, and 124C3.

[0073] The quarter-wave plates 124A2, 124B2, and 124C2 in each window are arranged at a 45° angle relative to the polarizing filters 124A3, 124B3, and 124C3 in each window. More specifically, the fast axis (high-speed axis) is arranged at a 45° angle relative to the transmission axis of the polarizing filters 124A3, 124B3, and 124C3 in each window. In this embodiment, the fast axis is arranged at a 45° counterclockwise angle.

[0074] Figure 4 This diagram shows an example of the polarizing filters included in each window. Furthermore, Figure 5 This is a diagram showing an example of a quarter-wave plate present in each window. Furthermore, Figure 6 This is a diagram illustrating an example of the structure of the filter array present in each window.

[0075] exist Figure 4 In the diagram, the long arrows LPA, LPB, and LPC within each window 122A, 122B, and 122C indicate the direction of the transmission axis of the polarizing filters 124A3, 124B3, and 124C3 contained in each window 122A, 122B, and 122C.

[0076] Furthermore, in Figure 5In the diagram, the arrows FAA, FAB, and FAC within each window 122A, 122B, and 122C indicate the direction of the fast axis of the quarter-wave plates 124A2, 124B2, and 124C2 present in each window 122A, 122B, and 122C.

[0077] like Figures 4-6 As shown, the quarter-wave plates 124A2, 124B2, and 124C2 in each window 122A, 122B, and 122C are arranged at a 45° counterclockwise angle relative to the transmission axis of the polarizing filters 124A3, 124B3, and 124C3 in each window. Specifically, in the first window, a quarter-wave plate with a fast axis angle of 45° is arranged as a quarter-wave plate. Furthermore, in the second window, a quarter-wave plate with a fast axis angle of 105° is arranged as a quarter-wave plate. And in the third window, a quarter-wave plate with a fast axis angle of 165° is arranged as a quarter-wave plate.

[0078] In addition, Figure 5 In the diagram, the short arrows LAA, LAB, and LAC within each window 122A, 122B, and 122C indicate the direction of the slow axis (low-speed axis) of the quarter-wave plates 124A2, 124B2, and 124C2 contained in each window 122A, 122B, and 122C. The slow axis is orthogonal to the fast axis.

[0079] As described above, each window 122A, 122B, and 122C comprises a filter group 124A, 124B, and 124C, consisting of bandpass filters 124A1, 124B1, and 124C1, quarter-wave plates 124A2, 124B2, and 124C2, and polarizing filters 124A3, 124B3, and 124C3. The quarter-wave plates 124A2, 124B2, and 124C2, and the polarizing filters 124A3, 124B3, and 124C3 are combined to form optical isolators 124A4, 124B4, and 124C4. Optical isolators 124A4, 124B4, and 124C4 are constructed using quarter-wave plates 124A2, 124B2, and 124C2, and polarizing filters 124A3, 124B3, and 124C3. Located behind bandpass filters 124A1, 124B1, and 124C1, they prevent re-reflection on the surfaces behind the bandpass filters 124A1, 124B1, and 124C1 caused by backlighting. Optical isolators 124A4, 124B4, and 124C4 are an example of optical elements. Furthermore, quarter-wave plates 124A2, 124B2, and 124C2 are examples of waveplates that convert linearly polarized light into circularly polarized or elliptically polarized light.

[0080] Figure 7This diagram illustrates the function of preventing re-reflection based on optical isolators.

[0081] This diagram illustrates an example of light (reflected light) reflected by the second lens group 110B entering the first window 122A. The reflected light also includes light reflected from sources such as the light-receiving surface of the image sensor. Furthermore, this diagram corresponds to... Figure 3 Section 7-7.

[0082] The reflected light L1, after being reflected by the second lens group 110B and entering the first window 122A, enters the bandpass filter 124A1 via the optical isolator 124A4. At this time, the light passes through the optical isolator 124A4 in the order of polarizing filter 124A3 and quarter-wave plate 124A2, and then enters the bandpass filter 124A1. During this process, it is converted to circularly polarized light. If the circularly polarized light is reflected by the bandpass filter 124A1 and re-enters the quarter-wave plate 124A2, it returns to linearly polarized light rotated by 90°. The light L2, whose direction has changed, is blocked from passing by the polarizing filter 124A3. This prevents re-reflection caused by the reflected light. Furthermore, by preventing the re-reflection of this reflected light, ghosting can be effectively suppressed.

[0083] Furthermore, since polarizing filters 124A3, 124B3, and 124C3 have the function of blocking the passage caused by re-reflection on bandpass filters 124A1, 124B1, and 124C1, absorption-type polarizing filters are preferred.

[0084] [Camera Body]

[0085] like Figure 1 As shown, the camera body 200 has an image sensor 210. The image sensor 210 is disposed on the optical axis of the lens assembly 100 and receives light passing through the lens assembly 100. This image sensor 210 is composed of a polarization image sensor. A polarization image sensor is an image sensor equipped with a polarizer, and each pixel has a polarizer. For example, a polarizer is provided between a microlens and a photodiode. In addition, such polarization image sensors are known (e.g., International Publication No. 2020 / 071253, etc.), so a detailed description of its contents is omitted.

[0086] The orientation (angle of the transmission axis) of the polarizer mounted on the polarization image sensor is selected according to the number of wavelengths being captured. In this embodiment, an image split into three wavelengths is captured. Therefore, a polarization image sensor with polarizers in at least three directions is used. In this embodiment, a polarization image sensor with polarizers in four directions is used.

[0087] Figure 8 This is a diagram illustrating an example of the configuration of pixels and polarizers in a polarization image sensor.

[0088] As shown in the figure, for pixels arranged in a matrix, four polarizers with different transmission axis angles are regularly arranged. The polarizer with a transmission axis angle of α1 is designated as the first polarizer, the polarizer with a transmission axis angle of α2 as the second polarizer, the polarizer with a transmission axis angle of α3 as the third polarizer, and the polarizer with a transmission axis angle of α4 as the fourth polarizer. As an example, in this embodiment, the transmission axis angle α1 of the first polarizer is set to 0°, the transmission axis angle α2 of the second polarizer is set to 45°, the transmission axis angle α3 of the third polarizer is set to 90°, and the transmission axis angle α4 of the fourth polarizer is set to 135°.

[0089] Pixel P1, which has a first polarizer, is designated as the first pixel; pixel P2, which has a second polarizer, is designated as the second pixel; pixel P3, which has a third polarizer, is designated as the third pixel; and pixel P4, which has a fourth polarizer, is designated as the fourth pixel. A 2×2 pixel group consisting of the first pixel P1, the second pixel P2, the third pixel P3, and the fourth pixel P4 is designated as a unit (pixel unit) PU, and this pixel unit PU is repeatedly arranged along the X-axis and Y-axis.

[0090] Thus, in a polarization image sensor equipped with polarizers in four directions, it is possible to capture polarization images in four directions with a single illumination.

[0091] The image sensor 210 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) type comprising a driving unit, an ADC (Analog-to-Digital Converter), and a signal processing unit. In this case, the image sensor 210 is driven by the built-in driving unit. Furthermore, the signal of each pixel is converted into a digital signal by the built-in ADC and output. Moreover, the signal of each pixel undergoes correlation double sampling, gain processing, correction processing, etc., by the built-in signal processing unit and is output. The signal processing can be performed after conversion to a digital signal or before conversion to a digital signal.

[0092] The camera body 200, in addition to the image sensor 210, includes an output unit (not shown) that outputs data of the images captured by the image sensor 210, and a camera control unit (not shown) that controls the overall movement of the camera body 200. The camera control unit may be, for example, a processor. The processor functions as the camera control unit by executing a predetermined control program.

[0093] Furthermore, the image data output from the camera body 200 is so-called RAW image data, that is, unprocessed image data. This RAW image data is processed by the signal processing unit 300 to generate an image split into multiple wavelengths.

[0094] [Signal Processing Device]

[0095] As described above, the signal processing device 300 processes the image data (RAW image data) output from the camera body 200 to generate an image split into multiple wavelengths. More specifically, it generates an image with wavelengths corresponding to the transmission wavelength regions of the bandpass filters provided in each window of the lens device 100. In this embodiment, an image with three wavelengths is generated, consisting of an image of a first wavelength region λ1 (first image), an image of a second wavelength region λ2 (second image), and an image of a third wavelength region λ3 (third image).

[0096] Figure 9 This is a diagram illustrating an example of the hardware structure of a signal processing device.

[0097] As shown in the figure, the signal processing device 300 includes a CPU (Central Processing Unit) 311, a ROM (Read Only Memory) 312, a RAM (Random Access Memory) 313, an auxiliary storage device 314, an input device 315, an output device 316, and an input / output interface 317. This signal processing device 300 is, for example, composed of a general-purpose computer such as a personal computer.

[0098] Regarding the signal processing device 300, it functions as a signal processing device by executing a predetermined program (signal processing program) by the CPU 311, which acts as a processor. The program executed by the CPU 311 is stored in the ROM 312 or the auxiliary storage device 314.

[0099] The auxiliary storage device 314 constitutes the storage unit of the signal processing device 300. The auxiliary storage device 314 may be, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0100] The input device 315 constitutes the operation unit of the signal processing device 300. The input device 315 may be, for example, a keyboard, a mouse, a touch panel, etc.

[0101] The output device 316 constitutes the display unit of the signal processing device 300. The output device 316 may be, for example, a liquid crystal display (LCD) or an organic light emitting diode (OLED) display.

[0102] The input / output interface 317 forms the connection part of the signal processing device 300. The signal processing device 300 is connected to the camera body 200 via the input / output interface 317.

[0103] Figure 10 It is a block diagram of the functions of a signal processing device.

[0104] As shown in the figure, the signal processing device 300 has the functions of an image data acquisition unit 320, an image generation unit 330, an output control unit 340, and a recording control unit 350. These functions are implemented by the CPU 311 executing a predetermined program.

[0105] The image data acquisition unit 320 acquires image data obtained through photography from the camera body 200. As described above, the image data acquired from the camera body 200 is RAW image data.

[0106] The image generation unit 330 performs prescribed signal processing on the image data acquired by the image data acquisition unit 320 to generate images of multiple wavelengths. In this embodiment, an image of the first wavelength region λ1 (first image), an image of the second wavelength region λ2 (second image), and an image of the third wavelength region λ3 (third image) are generated. The image generation unit 330 performs interference removal processing on the image data acquired by the image data acquisition unit 320 at the pixel unit level to generate images of each wavelength region λ1, λ2, and λ3. This processing will be summarized below.

[0107] As described above, the polarization image sensor equipped with polarizers in four directions can capture polarization images in four directions with a single illumination. Each of these four polarization images contains image components of wavelength regions λ1, λ2, and λ3 at a predetermined ratio (interference rate). The interference rate is determined and is known by the angle of the transmission axis of the polarization filter in each window of the filter unit 120 and the angle of the transmission axis of the polarizer in each pixel. Furthermore, by utilizing this interference rate information, images of each wavelength region can be generated.

[0108] The pixel value of the first pixel P1 in the image captured by the image sensor 210 is set to x1, the pixel value of the second pixel P2 is set to x2, the pixel value of the third pixel P3 is set to x3, and the pixel value of the fourth pixel P4 is set to x4.

[0109] Furthermore, the pixel value of the corresponding pixel in the generated first image is set to X1, the pixel value of the corresponding pixel in the second image is set to X2, and the pixel value of the corresponding pixel in the third image is set to X3.

[0110] If we set the ratio of light from the first wavelength region λ1 to light received by the first pixel P1 as b11, the ratio of light from the second wavelength region λ2 to light received by the first pixel P1 as b12, and the ratio of light from the third wavelength region λ3 to light received by the first pixel P1 as b13, then the following relationship holds between X1, X2, X3 and x1.

[0111] b11*X1+b12*X2+b13*X3=x1…(Equation 1)

[0112] Furthermore, if the ratio of light from the first wavelength region λ1 to light received by the second pixel P2 is set as b21, the ratio of light from the second wavelength region λ2 to light received by the second pixel P2 is set as b22, and the ratio of light from the third wavelength region λ3 to light received by the second pixel P2 is set as b23, then the following relationship holds between X1, X2, X3 and x2.

[0113] b21*X1+b22*X2+b23*X3=x2…(Formula 2)

[0114] Furthermore, if the ratio of light from the first wavelength region λ1 to light received by the third pixel P3 is set to b31, the ratio of light from the second wavelength region λ2 to light received by the third pixel P3 is set to b32, and the ratio of light from the third wavelength region λ3 to light received by the third pixel P3 is set to b33, then the following relationship holds between X1, X2, X3 and x3.

[0115] b31*X1+b32*X2+b33*X3=x3…(Formula 3)

[0116] Furthermore, if the ratio of light from the first wavelength region λ1 to light received by the fourth pixel P4 is set as b41, the ratio of light from the second wavelength region λ2 to light received by the fourth pixel P4 is set as b42, and the ratio of light from the third wavelength region λ3 to light received by the fourth pixel P4 is set as b43, then the following relationship holds between X1, X2, X3 and x4.

[0117] b41*X1+b42*X2+b43*X3=x4…(Equation 4)

[0118] Regarding X1, X2, and X3, by solving the simultaneous equations 1 to 4 above, the pixel values ​​X1, X2, and X3 of the corresponding pixels in the first, second, and third images can be obtained.

[0119] Thus, by utilizing information about the interference rate, it is possible to generate images of various wavelength regions from images captured by an image sensor.

[0120] Here, the aforementioned simultaneous equations can be expressed using matrices. Furthermore, X1, X2, and X3 can be calculated by multiplying both sides of the inverse matrix. The signal processing device 300 retains the elements of the inverse matrix as a coefficient group. Information about the coefficient group is stored, for example, in the auxiliary storage device 314. The image generation unit 330 retrieves the information about the coefficient group from the auxiliary storage device 314, thereby generating images for each wavelength region.

[0121] The output control unit 340 controls the output of images (first image, second image, and third image) of each wavelength region generated by the image generation unit 330. In this embodiment, it controls the output (display) to the display, which is the output device 316.

[0122] The recording control unit 350 controls the recording of images of each wavelength region generated by the image generation unit 330 according to instructions from the user. The generated images of each wavelength region are recorded in the auxiliary storage device 314.

[0123] [The role of a multispectral camera system]

[0124] The multispectral camera system 1 of this embodiment, configured as described above, can simultaneously capture images split into three wavelengths. These three wavelengths correspond to the transmission wavelength regions of the three bandpass filters 124A1, 124B1, and 124C1 included in the lens device 100. Therefore, by changing the bandpass filters, images in different wavelength regions can be captured.

[0125] However, considering the degree of freedom in spectral transmission characteristics, reflective bandpass filters are preferred. But if a reflective bandpass filter is used, there is a concern about ghosting caused by reflections from the bandpass filter.

[0126] However, the lens device 100 according to this embodiment includes optical isolators 124A4, 124B4, and 124C4 in each window portion 122A, 122B, and 122C, thereby suppressing reflections from the bandpass filters 124A1, 124B1, and 124C1. This effectively suppresses ghosting and enables the capture of high-quality images.

[0127] [Variation Example]

[0128] [Examples of variations in the structure of the filter assemblies in each window]

[0129] As described above, the quarter-wave plates arranged in each window of the filter unit are configured to combine with the polarizing filter to form an optical isolator. Specifically, their fast axis is tilted at 45° relative to the transmission axis of the polarizing filter.

[0130] Figure 11 This is a diagram showing a variation of the filter group provided in each window.

[0131] In this example, the setting of the quarter-wave plate in each window is different from that of the filter unit in the above embodiment.

[0132] As shown in the figure, in the first window, a quarter-wave plate with a fast axis angle of 135° is arranged as a quarter-wave plate. Furthermore, in the second window, a quarter-wave plate with a fast axis angle of 15° is arranged as a quarter-wave plate. And in the third window, a quarter-wave plate with a fast axis angle of 75° is arranged as a quarter-wave plate. That is, in this example, the quarter-wave plate is arranged at a 45° clockwise angle relative to the polarizing filter. In this case, similar to the lens device of the above embodiment, an optical isolator can be constructed from the quarter-wave plate and the polarizing filter.

[0133] [Example of a modified optical isolator]

[0134] An optical isolator can also be constructed by using an eighth-wave plate instead of a quarter-wave plate. That is, by using an eighth-wave plate instead of a quarter-wave plate, an optical isolator can also be constructed by combining the eighth-wave plate with a polarizing filter.

[0135] [Second Implementation]

[0136] In the lens device of the first embodiment described above, the structure is such that an optical isolator is disposed in each window portion on the rear side (image side) of the bandpass filter. In the lens device of this embodiment, the structure is such that optical isolators are disposed on the front and rear sides of the bandpass filter, i.e., on the object side and the image side. Furthermore, the structure other than the filter unit is the same as that of the lens device of the first embodiment described above. Therefore, only the structure of the filter unit will be described below.

[0137] Figure 12 This is a diagram showing the general structure of a filter unit.

[0138] As shown in the figure, the three windows 122A, 122B, and 122C in the filter frame 122 each contain filter groups 130A, 130B, and 130C. Each filter group 130A, 130B, and 130C consists of five filters.

[0139] The five filters consist of the first polarizing filters 130A1, 130B1, and 130C1, the first quarter-wave plates 130A2, 130B2, and 130C2, the bandpass filters 130A3, 130B3, and 130C3, the second quarter-wave plates 130A4, 130B4, and 130C4, and the second polarizing filters 130A5, 130B5, and 130C5. Five filters are arranged along the optical axis Z from the object side in the following order: first polarizing filter 130A1, 130B1, 130C1; first quarter-wave plate 130A2, 130B2, 130C2; bandpass filter 130A3, 130B3, 130C3; second quarter-wave plate 130A4, 130B4, 130C4; and second polarizing filter 130A5, 130B5, 130C5.

[0140] In each window 122A, 122B, and 122C, the first polarizing filters 130A1, 130B1, and 130C1 and the first quarter-wave plates 130A2, 130B2, and 130C2 form the first optical isolators 130A6, 130B6, and 130C6 on the front side (object side) of the bandpass filters 130A3, 130B3, and 130C3. Furthermore, the second quarter-wave plates 130A4, 130B4, and 130C4 and the second polarizing filters 130A5, 130B5, and 130C5 form the second optical isolators 130A7, 130B7, and 130C7 on the rear side (image side) of the bandpass filters 130A3, 130B3, and 130C3.

[0141] To form an optical isolator, the first quarter-wave plates 130A2, 130B2, and 130C2 are arranged at a 45° angle relative to the first polarizing filters 130A1, 130B1, and 130C1. Furthermore, the second quarter-wave plates 130A4, 130B4, and 130C4 are arranged at a 45° angle relative to the second polarizing filters 130A5, 130B5, and 130C5.

[0142] Figure 13 This is a diagram illustrating an example of the structure of the filter array present in each window.

[0143] (1) 1st window

[0144] The first window is the window through which light of the first wavelength region λ1 is transmitted.

[0145] like Figure 13As shown, in the first window, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter. Furthermore, in the first window, a quarter-wave plate with a fast axis angle of 135° is arranged as a first quarter-wave plate. The first polarizing filter and the first quarter-wave plate constitute a first optical isolator. In this example, the optical isolator is formed by arranging the first quarter-wave plate at a 45° clockwise angle relative to the first polarizing filter.

[0146] Furthermore, in the first window, a bandpass filter with a first wavelength region λ1 is configured as a bandpass filter.

[0147] Furthermore, in the first window, a second quarter-wave plate with a fast axis angle of 45° is arranged as the second quarter-wave plate. Also in the first window, a polarizing filter with a transmission axis angle of 0° is arranged as the second polarizing filter. The second polarizing filter and the second quarter-wave plate constitute the second optical isolator. In this example, the optical isolator is constructed by tilting the second quarter-wave plate counterclockwise by 45° relative to the second polarizing filter.

[0148] With the above settings, the first window allows linearly polarized light with an azimuth angle of 0° to pass through, specifically: First, it passes through the first polarizing filter, thus becoming linearly polarized light with an azimuth angle of 0°. Next, it passes through the first quarter-wave plate, thus converting it into circularly polarized light. Then, it passes through the bandpass filter, thus becoming light with the first wavelength region λ1. Next, it passes through the second quarter-wave plate, thus returning to linearly polarized light. Finally, it passes through the second polarizing filter, thus becoming linearly polarized light with an azimuth angle of 0°.

[0149] (2) Second window

[0150] The second window is the window that allows light from the second wavelength region λ2 to pass through.

[0151] like Figure 13 As shown, in the second window, a polarizing filter with a transmission axis angle of 60° is arranged as a first polarizing filter. Furthermore, in the second window, a quarter-wave plate with a fast axis angle of 15° is arranged as a first quarter-wave plate. The first polarizing filter and the first quarter-wave plate constitute a first optical isolator. In this example, the optical isolator is formed by arranging the first quarter-wave plate at a 45° clockwise angle relative to the first polarizing filter.

[0152] Furthermore, in the second window, a bandpass filter with a second wavelength region λ2 is configured as a bandpass filter.

[0153] Furthermore, in the second window, a quarter-wave plate with a fast axis angle of 105° is arranged as the second quarter-wave plate. Also in the second window, a polarizing filter with a transmission axis angle of 60° is arranged as the second polarizing filter. The second polarizing filter and the second quarter-wave plate constitute the second optical isolator. In this example, the optical isolator is constructed by tilting the second quarter-wave plate counterclockwise by 45° relative to the second polarizing filter.

[0154] With the above settings, the second window allows linearly polarized light of the second wavelength region λ2, with an azimuth angle of 60°, to pass through. Specifically, first, it passes through the first polarizing filter, thus becoming linearly polarized light with an azimuth angle of 60°. Next, it passes through the first quarter-wave plate, thus converting it into circularly polarized light. Then, it passes through the bandpass filter, thus becoming light of the first wavelength region λ1. Next, it passes through the second quarter-wave plate, thus returning to linearly polarized light. Finally, it passes through the second polarizing filter, thus becoming linearly polarized light with an azimuth angle of 60°.

[0155] (3) 3rd window part

[0156] The third window is the window that allows light from the third wavelength region λ3 to pass through.

[0157] like Figure 13 As shown, in the third window, a polarizing filter with a transmission axis angle of 120° is arranged as a first polarizing filter. Furthermore, in the third window, a quarter-wave plate with a fast axis angle of 75° is arranged as a first quarter-wave plate. The first polarizing filter and the first quarter-wave plate constitute a first optical isolator. In this example, the optical isolator is formed by arranging the first quarter-wave plate at a 45° clockwise angle relative to the first polarizing filter.

[0158] Furthermore, in the third window, a bandpass filter with a third wavelength region λ3 is configured as a bandpass filter.

[0159] Furthermore, in the third window, a quarter-wave plate with a fast axis angle of 165° is arranged as the second quarter-wave plate. Also in the third window, a polarizing filter with a transmission axis angle of 120° is arranged as the second polarizing filter. The second polarizing filter and the second quarter-wave plate constitute the second optical isolator. In this example, the optical isolator is formed by tilting the second quarter-wave plate counterclockwise by 45° relative to the second polarizing filter.

[0160] With the above settings, the third window allows linearly polarized light of the third wavelength region λ3 with an azimuth angle of 120° to pass through. Specifically, first, it passes through the first polarizing filter, thus becoming linearly polarized light with an azimuth angle of 120°. Next, it passes through the first quarter-wave plate, thus converting it into circularly polarized light. Next, it passes through the bandpass filter, thus becoming light of the first wavelength region λ1. Next, it passes through the second quarter-wave plate, thus returning to linearly polarized light. Finally, it passes through the second polarizing filter, thus becoming linearly polarized light with an azimuth angle of 120°.

[0161] As described above, each window in the filter unit 120 allows light of different wavelength regions and polarization directions to pass through.

[0162] Figure 14 This diagram illustrates the function of preventing re-reflection based on the front and rear optical isolators.

[0163] The figure shows an example of light (reflected light) reflected by the first lens group 110A and light (reflected light) reflected by the second lens group 110B entering the first window 122A.

[0164] The reflected light L11, after being reflected by the first lens group 110A and entering the first window 122A, enters the bandpass filter 130A3 via the first optical isolator 130A6. At this time, the light passes through the first optical isolator 130A6 in the order of the first polarizing filter 130A1 and the first quarter-wave plate 130A2, and then enters the bandpass filter 130A3. During this process, it is converted to circularly polarized light. If the circularly polarized light is reflected by the bandpass filter 130A3 and re-enters the first quarter-wave plate 130A2, it returns to linearly polarized light, rotated by 90°. The light L12, whose direction has changed, is blocked by the first polarizing filter 130A1. This prevents re-reflection caused by the reflected light from the front side (object side).

[0165] On the other hand, the reflected light L21, which enters the first window 122A after being reflected by the second lens group 110B, enters the bandpass filter 130A3 via the second optical isolator 130A7. At this time, the light passes through the second optical isolator 130A7 in the order of the second polarizing filter 130A5 and the second quarter-wave plate 130A4 before entering the bandpass filter 130A3. During this process, it is converted to circularly polarized light. If the circularly polarized light is reflected by the bandpass filter 130A3 and re-enters the second quarter-wave plate 130A4, it returns to linearly polarized light that has been rotated 90°. The light L22, whose direction has changed, is blocked from passing by the second polarizing filter 130A5. This prevents re-reflection caused by the reflected light.

[0166] Thus, the lens device according to this embodiment can prevent the re-reflection of backlight before and after the bandpass filter. As a result, ghosting can be further suppressed more effectively.

[0167] [Variation Example]

[0168] [Examples of variations in the structure of the filter assemblies in each window]

[0169] As described above, the quarter-wave plate and polarizing filter arranged before and after the bandpass filter are configured to form an optical isolator. Specifically, the quarter-wave plate is arranged at a 45° angle relative to the polarizing filter.

[0170] [First Variation]

[0171] Figure 15 This is a diagram showing a variation of the filter group provided in each window.

[0172] Figure 15 (A) represents the first variation of the filter group configured in each window.

[0173] In this example, the settings of the first quarter-wave plate and the second quarter-wave plate in each window are different from those in the filter unit of the above embodiment.

[0174] As shown in the figure, in the first window, a quarter-wave plate with a fast axis angle of 45° is arranged as the first quarter-wave plate. Furthermore, in the second window, a quarter-wave plate with a fast axis angle of 105° is arranged as the first quarter-wave plate. And in the third window, a quarter-wave plate with a fast axis angle of 165° is arranged as the first quarter-wave plate. That is, in this example, the first quarter-wave plate is arranged at a 45° clockwise angle relative to the first polarizing filter. Similarly to the filter unit in the above embodiment, the first quarter-wave plate and the first polarizing filter can constitute the first optical isolator.

[0175] Furthermore, as shown in the figure, in the first window, a quarter-wave plate with a fast axis angle of 135° is arranged as the second quarter-wave plate. In the second window, a quarter-wave plate with a fast axis angle of 15° is arranged as the second quarter-wave plate. In the third window, a quarter-wave plate with a fast axis angle of 75° is arranged as the second quarter-wave plate. That is, in this example, the second quarter-wave plate is arranged at a 45° counterclockwise angle relative to the second polarizing filter. Similarly to the filter unit in the above embodiment, the second quarter-wave plate and the second polarizing filter can constitute the second optical isolator.

[0176] [Second Variation]

[0177] Figure 15 (B) represents the second variation of the filter group in each window.

[0178] In this example, the structure of the first optical isolator in each window is different from that of the filter unit in the above embodiment.

[0179] As shown in the figure, the first optical isolator in each window is composed of a first polarizing filter with a transmission axis angle of 0° and a first quarter-wave plate with a fast axis angle of 135°. That is, in the filter unit of this example, each window has a first optical isolator with the same structure.

[0180] The polarization direction of the light passing through each window is ultimately determined by the second polarizing filter. Therefore, for the first optical isolator, a first optical isolator with the same structure in each window can be used.

[0181] [3rd Variation]

[0182] Figure 15 (C) represents the third variation of the filter group in each window.

[0183] In this example, the structure of the first optical isolator also differs from the filter unit in the above embodiment. Furthermore, in this example, the first optical isolator with the same structure can be provided in each window. The difference from the second variation described above lies in the setting of the first quarter-wave plate constituting the first optical isolator. As shown in the figure, the first quarter-wave plate can be a quarter-wave plate with a fast axis angle of 45°. That is, the first quarter-wave plate is arranged at a 45° clockwise angle relative to the first polarizing filter.

[0184] In addition, in this example and the second modified example described above, each window has a first optical isolator with the same structure, but it is also possible to configure a first optical isolator with a different structure in each window.

[0185] However, considering the amount of light transmitted, the optical isolators (first optical isolator and second optical isolator) disposed before and after the bandpass filter are preferably configured as follows: that is, they are configured such that the fast axes of the quarter-wave plates before and after the bandpass filter are at different angles. More preferably, they are configured such that the fast axes of the quarter-wave plates before and after the bandpass filter are orthogonal.

[0186] It is difficult to achieve a complete quarter-wave plate at all wavelengths. Therefore, the light becomes elliptically polarized as it passes through the first and second quarter-wave plates. If it passes through a polarizing filter in this state, the light intensity decreases. This phenomenon is maximized if the fast axes of the first and second quarter-wave plates are aligned; that is, the decrease in light intensity becomes greater.

[0187] Therefore, a structure is designed where the fast axes of the front and rear quarter-wave plates of the bandpass filter are at different angles. More preferably, a structure is designed where the fast axes of the front and rear quarter-wave plates of the bandpass filter are orthogonal.

[0188] The structure of the above-described embodiment and the structure of the first modification are such that the fast axes of the quarter-wave plates before and after the bandpass filter are orthogonal in all the windows.

[0189] [Third Implementation]

[0190] In the lens device of the first and second embodiments described above, the polarization direction of the light passing through each window is adjusted by a polarizing filter disposed on the rear side of the bandpass filter.

[0191] In this embodiment, a half-wave plate is further disposed behind the optical isolator located behind the bandpass filter, and the polarization direction of the light passing through each window is adjusted.

[0192] Furthermore, the structure other than the filter unit is the same as that of the lens device in the first embodiment described above. Therefore, only the structure of the filter unit will be described below.

[0193] Figure 16 This is a diagram showing the general structure of a filter unit.

[0194] As shown in the figure, filter groups 140A, 140B, and 140C are respectively provided in windows 122A, 122B, and 122C.

[0195] The filter group 140A in the first window 122A consists of three filters. On the other hand, the filter group 140B in the second window 122B consists of four filters. Furthermore, the filter group 140C in the third window 122C also consists of four filters.

[0196] The filter group 140A that may be included in the first window 122A consists of a bandpass filter 140A1, a quarter-wave plate 140A2, and a polarizing filter 140A3. The filters are arranged along the optical axis Z from the object side in the order of bandpass filter 140A1, quarter-wave plate 140A2, and polarizing filter 140A3. Furthermore, the quarter-wave plate 140A2 and polarizing filter 140A3 constitute an optical isolator 140A4.

[0197] The filter group 140B that may be included in the second window 122B consists of a bandpass filter 140B1, a quarter-wave plate 140B2, a polarizing filter 140B3, and a half-wave plate (HWP) 140B5. The filters are arranged along the optical axis Z from the object side in the following order: bandpass filter 140B1, quarter-wave plate 140B2, polarizing filter 140B3, and half-wave plate 140B5. Furthermore, the quarter-wave plate 140B2 and the polarizing filter 140B3 constitute an optical isolator 140B4.

[0198] The filter group 140C that may be included in the third window 122C consists of a bandpass filter 140C1, a quarter-wave plate 140C2, a polarizing filter 140C3, and a half-wave plate 140C5. The filters are arranged along the optical axis Z from the object side in the order of bandpass filter 140C1, quarter-wave plate 140C2, polarizing filter 140C3, and half-wave plate 140C5. Furthermore, the quarter-wave plate 140C2 and the polarizing filter 140C3 constitute an optical isolator 140C4.

[0199] Figure 17 This is a diagram illustrating an example of the structure of the filter array present in each window.

[0200] (1) 1st window

[0201] like Figure 17 As shown, in the first window, a bandpass filter with a first wavelength region λ1 is arranged as a bandpass filter (BPF). Furthermore, in the first window, a quarter-wave plate (QWP) with a fast axis angle of 45° is arranged. And in the first window, a polarizing filter (PLF) with a transmission axis angle of 0° is arranged.

[0202] In the first window, an optical isolator is formed by a quarter-wave plate and a polarizing filter. In this example, the optical isolator is formed by tilting the quarter-wave plate 45° counterclockwise relative to the polarizing filter.

[0203] With the above settings, the first window allows linearly polarized light with an azimuth angle of 0° to pass through the light in the first wavelength region λ1.

[0204] (2) Second window

[0205] like Figure 17As shown, in the second window, a bandpass filter with a second wavelength region λ2 is arranged as a bandpass filter (BPF). Furthermore, in the second window, a quarter-wave plate (QWP) with a fast axis angle of 45° is arranged. Also in the second window, a polarizing filter (PLF) with a transmission axis angle of 0° is arranged. Finally, in the second window, a half-wave plate (HWP) with a fast axis angle of 30° is arranged.

[0206] Similar to the first window, the second window comprises an optical isolator consisting of a quarter-wave plate and a polarizing filter. In this example, the optical isolator is configured by tilting the quarter-wave plate counterclockwise by 45° relative to the polarizing filter. Furthermore, the structure of this optical isolator is the same as that of the first window. Therefore, light with the same polarization direction as in the first window passes before the quarter-wave plate. In the second window, it is further passed through the quarter-wave plate, thereby switching the polarization direction. If the quarter-wave plate is tilted only by an angle Φ relative to the polarizing filter, the existing polarized light is rotated by an amount of 2Φ. In this example, the fast axis of the quarter-wave plate is tilted by 30° relative to the transmission axis (0°) of the polarizing filter. Therefore, in the second window, light passing through the quarter-wave plate becomes linearly polarized light with an azimuth angle of 60° and exits from the window.

[0207] (3) 3rd window part

[0208] like Figure 17 As shown, in the third window, a bandpass filter with a third wavelength region λ3 is arranged as a bandpass filter (BPF). Furthermore, in the third window, a quarter-wave plate (QWP) with a fast axis angle of 45° is arranged. Also in the third window, a polarizing filter (PLF) with a transmission axis angle of 0° is arranged. Finally, in the third window, a half-wave plate (HWP) with a fast axis angle of 150° is arranged.

[0209] Similar to the first and second windows, the third window comprises an optical isolator consisting of a quarter-wave plate and a polarizing filter. In this example, the optical isolator is formed by tilting the quarter-wave plate counterclockwise by 45° relative to the polarizing filter. Furthermore, the structure of this optical isolator is the same as that of the first and second windows. Therefore, light with the same polarization direction as in the first and second windows passes before the quarter-wave plate. The third window, also similar to the second window, allows light to pass through the quarter-wave plate, thereby switching the polarization direction. In the third window, the fast axis of the quarter-wave plate is tilted by 150° relative to the transmission axis (0°) of the polarizing filter. Therefore, in the third window, light passing through the quarter-wave plate becomes linearly polarized light with an azimuth angle of 120° and exits from the window.

[0210] As described above, the filter unit according to this embodiment can allow light with different wavelength regions and polarization directions to pass through from each window.

[0211] Furthermore, according to the filter unit of this embodiment, optical isolators with the same structure can be used in each window.

[0212] Furthermore, while the same optical isolator structure is used in each window in this embodiment, it is also possible to use optical isolators with different structures in each window. That is, it is also possible to use optical isolators with different angles for the quarter-wave plate and polarizing filter in each window.

[0213] Furthermore, in this embodiment, a half-wave plate is configured to be arranged outside the first window portion, but it can also be configured to have a half-wave plate in all windows.

[0214] [Variation Example]

[0215] [Examples of variations in the structure of the filter assemblies in each window]

[0216] Figure 18 This is a diagram showing a variation of the filter group provided in each window.

[0217] In this example, the setting of the quarter-wave plate in each window is different from that of the filter unit in the above embodiment.

[0218] like Figure 18 As shown, each window portion includes a quarter-wave plate with a fast axis angle of 135°. That is, in this example, the quarter-wave plate is arranged at a 45° clockwise angle relative to the polarizing filter. In this case, similar to the filter unit in the above embodiment, an optical isolator can be constructed from the quarter-wave plate and the polarizing filter.

[0219] In this example, linearly polarized light with an azimuth angle of 0° is emitted from the first window, representing the first wavelength region λ1. Furthermore, linearly polarized light with an azimuth angle of 60° is emitted from the second window, representing the second wavelength region λ2. Finally, linearly polarized light with an azimuth angle of 120° is emitted from the third window, representing the third wavelength region λ3.

[0220] [Example of a filter array structure with optical isolators placed before and after the bandpass filter]

[0221] When optical isolators are placed before and after the bandpass filter, the polarization direction of light passing through each window can be adjusted in the same way.

[0222] Figure 19 This diagram illustrates an example of the structure of a filter group in each window when optical isolators are placed before and after a bandpass filter.

[0223] When optical isolators are arranged before and after the bandpass filter, a half-wave plate is arranged behind the rear optical isolator (the second optical isolator). More specifically, a half-wave plate is arranged behind the polarizing filter (the second polarizing filter) constituting the rear optical isolator. Furthermore, in Figure 19 The example shown represents an example where half-wave plates are configured only in the second and third windows.

[0224] [Example of Structure 1]

[0225] Figure 19 (A) is a diagram showing a first structural example of the filter group provided in each window.

[0226] As shown in the figure, each window is equipped with a first optical isolator of the same structure. Furthermore, each window is equipped with a second optical isolator of the same structure.

[0227] In each window, the first optical isolator, located in front of the bandpass filter (BPF) (object side), is composed of a first polarizing filter (first PLF) with a transmission axis angle of 0° and a first quarter-wave plate (first QWP) with a fast axis angle of 135°.

[0228] Furthermore, in each window, the second optical isolator disposed behind the bandpass filter (BPF) (image side) is composed of a second quarter-wave plate (2nd QWP) with a fast axis angle of 45° and a second polarizing filter (2nd PLF) with a transmission axis angle of 0°.

[0229] The second and third windows further include a half-wave plate (HWP). The half-wave plate is positioned behind the second optical isolator. The second window has a half-wave plate with a fast axis angle of 30°. The third window has a half-wave plate with a fast axis angle of 150°.

[0230] In this example, linearly polarized light with an azimuth angle of 0° is emitted from the first window, representing the first wavelength region λ1. Furthermore, linearly polarized light with an azimuth angle of 60° is emitted from the second window, representing the second wavelength region λ2. Finally, linearly polarized light with an azimuth angle of 120° is emitted from the third window, representing the third wavelength region λ3.

[0231] [Example of Structure 2]

[0232] Figure 19 (B) is a diagram showing a second structural example of the filter group provided in each window.

[0233] As shown in the figure, in this example, a first optical isolator and a second optical isolator with the same structure are also arranged in each window. The difference from the first structural example is the angle setting of the quarter-wave plate constituting the optical isolator.

[0234] The first optical isolator consists of a first polarizing filter (first PLF) with a transmission axis angle of 0° and a first quarter-wave plate (first QWP) with a fast axis angle of 135°.

[0235] On the other hand, the second optical isolator is composed of a second quarter-wave plate (2QWP) with a fast axis angle of 45° and a second polarizing filter (2PLF) with a transmission axis angle of 0°.

[0236] In this example, linearly polarized light with an azimuth angle of 0° is emitted from the first window, representing the first wavelength region λ1. Furthermore, linearly polarized light with an azimuth angle of 60° is emitted from the second window, representing the second wavelength region λ2. Finally, linearly polarized light with an azimuth angle of 120° is emitted from the third window, representing the third wavelength region λ3.

[0237] In both the first and second structural examples, the fast axes of the quarter-wave plates are orthogonal before and after the bandpass filter. This prevents a decrease in the amount of light passing through each window.

[0238] Furthermore, in this example, optical isolators with different structures can be used in each window. Also, it is possible to configure a structure with half-wave plates in all windows.

[0239] [Fourth Implementation]

[0240] By placing an optical isolator on the front side (object side) of the bandpass filter, it is possible to prevent the re-reflection of backlight from the front.

[0241] However, if an optical isolator is placed only on the front side of the bandpass filter, the light emitted from each window is converted into circularly polarized light.

[0242] Therefore, by configuring an optical isolator in front of the bandpass filter and then further configuring a polarizing filter behind the bandpass filter, the polarization direction of the light passing through each window can be adjusted.

[0243] Furthermore, the structure other than the filter unit is the same as that of the lens device in the first embodiment described above. Therefore, only the structure of the filter unit will be described below.

[0244] Figure 20 This is a diagram showing the general structure of a filter unit.

[0245] As shown in the figure, windows 122A, 122B, and 122C each contain filter groups 150A, 150B, and 150C, respectively. Each window 122A, 122B, and 122C may contain filter groups 150A, 150B, and 150C, which consist of four filters. Specifically, they are composed of first polarizing filters 150A1, 150B1, and 150C1; quarter-wave plates 150A2, 150B2, and 150C2; bandpass filters 150A3, 150B3, and 150C3; and second polarizing filters 150A4, 150B4, and 150C4. The filters are arranged along the optical axis Z from the object side in the following order: first polarizing filters 150A1, 150B1, 150C1; quarter-wave plates 150A2, 150B2, 150C2; bandpass filters 150A3, 150B3, 150C3; and second polarizing filters 150A4, 150B4, 150C4. Furthermore, the first polarizing filters 150A1, 150B1, 150C1 and the quarter-wave plates 150A2, 150B2, 150C2 constitute optical isolators 150A5, 150B5, and 150C5.

[0246] Figure 21 This is a diagram illustrating an example of the structure of the filter array present in each window.

[0247] (1) 1st window

[0248] like Figure 21As shown, in the first window, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter (first PLF). Furthermore, in the first window, a quarter-wave plate (QWP) with a fast axis angle of 45° is arranged. Also in the first window, a bandpass filter (BPF) with a first wavelength region λ1 is arranged. Finally, a polarizing filter with a transmission axis angle of 0° is arranged as a second polarizing filter (second PLF).

[0249] In the first window, an optical isolator is formed by a first polarizing filter and a quarter-wave plate. In this example, the optical isolator is formed by tilting the quarter-wave plate 45° counterclockwise relative to the polarizing filter.

[0250] (2) Second window

[0251] like Figure 21 As shown, in the second window, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter (first PLF). Furthermore, in the second window, a quarter-wave plate (QWP) with a fast axis angle of 45° is arranged. Also in the second window, a bandpass filter (BPF) with a first wavelength region λ1 is arranged. Finally, a polarizing filter with a transmission axis angle of 60° is arranged as a second polarizing filter (second PLF).

[0252] In the second window, an optical isolator is formed by the first polarizing filter and a quarter-wave plate. In this example, the optical isolator is formed by tilting the quarter-wave plate 45° counterclockwise relative to the polarizing filter.

[0253] (3) 3rd window part

[0254] like Figure 21 As shown, in the third window, a polarizing filter with a transmission axis angle of 0° is arranged as the first polarizing filter (first PLF). Furthermore, in the third window, a quarter-wave plate (QWP) with a fast axis angle of 45° is arranged. Also in the third window, a bandpass filter (BPF) with a first wavelength region λ1 is arranged. Finally, a polarizing filter with a transmission axis angle of 120° is arranged as the second polarizing filter (second PLF).

[0255] In the third window, an optical isolator is formed by the first polarizing filter and a quarter-wave plate. In this example, the optical isolator is formed by tilting the quarter-wave plate 45° counterclockwise relative to the polarizing filter.

[0256] As described above, in the filter unit of this embodiment, each window has an optical isolator with the same structure, and the polarization direction is adjusted substantially by the second polarizing filter.

[0257] According to the filter unit of this embodiment, linearly polarized light with an azimuth angle of 0° is emitted from the first window, light with a first wavelength region λ1 is emitted from the second window, and linearly polarized light with an azimuth angle of 60° is emitted from the second window. Linearly polarized light with a third wavelength region λ3 and an azimuth angle of 120° is emitted from the third window.

[0258] [Variation Example]

[0259] [Examples of variations in the structure of the filter assemblies in each window]

[0260] As described above, when an optical isolator is arranged in front of the bandpass filter, a polarizing filter is further arranged behind the bandpass filter to adjust the polarization direction of the light passing through each window.

[0261] Figure 22 This is a diagram showing a variation of the filter group provided in each window.

[0262] [First Variation]

[0263] Figure 22 (A) represents the first variation of the filter group configured in each window.

[0264] The filter unit in this example also has an optical isolator with the same structure in each window. The difference from the filter unit in the above embodiment lies in the angle setting of the quarter-wave plate.

[0265] like Figure 22 As shown in (A), in each window portion, a quarter-wave plate with a fast axis angle of 135° is arranged as a quarter-wave plate. That is, in this example, the quarter-wave plate is arranged at a 45° clockwise angle relative to the first polarizing filter. At this time, similar to the filter unit of the above embodiment, an optical isolator can be formed by the quarter-wave plate and the first polarizing filter.

[0266] [Second Variation]

[0267] Figure 22 (B) represents the second variation of the filter group configured in each window.

[0268] In this example, the filter unit has optical isolators with different structures in each window. Furthermore, the structure of the second polarizing filter is the same as that of the filter unit in the above embodiment.

[0269] like Figure 22As shown in (B), in the first window, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter (first PLF). Furthermore, in the first window, a quarter-wave plate (QWP) with a fast axis angle of 45° is arranged as a quarter-wave plate. By arranging the quarter-wave plate in the first window at a 45° counterclockwise angle relative to the first polarizing filter, an optical isolator is formed.

[0270] In the second window, a polarizing filter with a transmission axis angle of 60° is arranged as a first polarizing filter (first PLF). Furthermore, a quarter-wave plate (QWP) with a fast axis angle of 15° is arranged in the second window. The second window is also configured as an optical isolator by tilting the quarter-wave plate 45° counterclockwise relative to the first polarizing filter.

[0271] In the third window, a polarizing filter with a transmission axis angle of 120° is arranged as a first polarizing filter (first PLF). Furthermore, in the third window, a quarter-wave plate (QWP) with a fast axis angle of 75° is arranged. In the third window, an optical isolator is also constructed by arranging the quarter-wave plate at a 45° counterclockwise angle relative to the first polarizing filter.

[0272] [3rd Variation]

[0273] Figure 22 (C) represents the third variation of the filter group configured in each window.

[0274] The filter unit in this example also has optical isolators with different structures in each window. The difference from the second variation lies in the angle setting of the quarter-wave plate.

[0275] like Figure 22 As shown in (C), in the first window, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter (first PLF). Furthermore, in the first window, a quarter-wave plate (QWP) with a fast axis angle of 135° is arranged as a quarter-wave plate. By arranging the quarter-wave plate in the first window at a 45° clockwise angle relative to the first polarizing filter, an optical isolator is formed.

[0276] In the second window, a polarizing filter with a transmission axis angle of 60° is arranged as a first polarizing filter (first PLF). Furthermore, in the second window, a quarter-wave plate (QWP) with a fast axis angle of 105° is arranged. In the second window, an optical isolator is also constructed by arranging the quarter-wave plate at a 45° clockwise angle relative to the first polarizing filter.

[0277] In the third window, a polarizing filter with a transmission axis angle of 120° is arranged as a first polarizing filter (first PLF). Furthermore, in the third window, a quarter-wave plate (QWP) with a fast axis angle of 165° is arranged. In the third window, an optical isolator is also constructed by arranging the quarter-wave plate at a 45° clockwise angle relative to the first polarizing filter.

[0278] [Other implementation methods and variations]

[0279] [Number of windows]

[0280] In the filter unit, the number of windows is set according to the number of wavelengths of the beam splitting. For example, when shooting with two wavelengths of beam splitting, at least two windows are provided. And when shooting with four wavelengths of beam splitting, at least four windows are provided.

[0281] Figure 23 This diagram illustrates an example of the structure of a filter unit used for imaging with light splitting into four wavelengths. Additionally, the diagram shows an example of optical isolators positioned before and after the bandpass filter.

[0282] As shown in the figure, the filter frame 122 has four windows 122A, 122B, 122C, and 122D. The windows 122A to 122D are arranged at regular intervals on the same circumference with the center of the filter frame 122 as the axis. That is, they are arranged at 90° intervals. Hereinafter, as needed, window 122A is designated as the first window, window 122B as the second window, window 122C as the third window, and window 122D as the fourth window to distinguish the windows 122A to 122D.

[0283] Each window 122A to 122D has a filter group 160A to 160D. Each filter group 160A to 160D consists of 5 filters.

[0284] The five filters consist of a first polarizing filter 160A1–160D1, a first quarter-wave plate 160A2–160D2, a bandpass filter 160A3–160D3, a second quarter-wave plate 160A4–160D4, and a second polarizing filter 160A5–160D5. The five filters are arranged along the optical axis Z from the object side in the following order: first polarizing filter 160A1–160D1, first quarter-wave plate 160A2–160D2, bandpass filter 160A3–160D3, second quarter-wave plate 160A4–160D4, and second polarizing filter 160A5–160D5.

[0285] In each window 122A to 122D, the first polarizing filters 160A1 to 160D1 and the first quarter-wave plates 160A2 to 160D2 form the first optical isolators 160A6 to 160D6 on the front side (object side) of the bandpass filters 160A3 to 160D3. Furthermore, the second quarter-wave plates 160A4 to 160D4 and the second polarizing filters 160A5 to 160D5 form the second optical isolators 160A7 to 160D7 on the rear side (image side) of the bandpass filters 160A3 to 160D3.

[0286] To form an optical isolator, the first quarter-wave plates 160A2 to 160D2 are arranged at a 45° angle relative to the first polarizing filters 160A1 to 160D1. Furthermore, the second quarter-wave plates 160A4 to 160D4 are arranged at a 45° angle relative to the second polarizing filters 160A5 to 160D5.

[0287] Figure 24 This is a diagram illustrating an example of the structure of the filter array present in each window.

[0288] (1) 1st window

[0289] The first window is the window through which light of the first wavelength region λ1 is transmitted.

[0290] like Figure 24 As shown, in the first window, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter. Furthermore, in the first window, a quarter-wave plate with a fast axis angle of 45° is arranged as a first quarter-wave plate. The first polarizing filter and the first quarter-wave plate constitute a first optical isolator. In this example, the optical isolator is formed by tilting the first quarter-wave plate counterclockwise by 45° relative to the first polarizing filter.

[0291] Furthermore, in the first window, a bandpass filter with a first wavelength region λ1 is configured as a bandpass filter.

[0292] Furthermore, in the first window, a quarter-wave plate with a fast axis angle of 135° is arranged as the second quarter-wave plate. Also in the first window, a polarizing filter with a transmission axis angle of 0° is arranged as the second polarizing filter. The second polarizing filter and the second quarter-wave plate constitute the second optical isolator. In this example, the optical isolator is formed by arranging the second quarter-wave plate at a 45° clockwise angle relative to the second polarizing filter.

[0293] With the above settings, the first window allows linearly polarized light with an azimuth angle of 0° to pass through the light in the first wavelength region λ1.

[0294] (2) Second window

[0295] The second window is the window that allows light from the second wavelength region λ2 to pass through.

[0296] like Figure 24 As shown, in the second window, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter. Furthermore, in the second window, a quarter-wave plate with a fast axis angle of 45° is arranged as a first quarter-wave plate. That is, in the second window, a polarizing filter and a quarter-wave plate with the same structure as those in the first window are provided in front of the bandpass filter.

[0297] In the second window, a bandpass filter with a second wavelength region λ2 is further configured as a bandpass filter.

[0298] Furthermore, in the second window, a quarter-wave plate with a fast axis angle of 15° is arranged as the second quarter-wave plate. Also in the second window, a polarizing filter with a transmission axis angle of 60° is arranged as the second polarizing filter. The second polarizing filter and the second quarter-wave plate constitute the second optical isolator. In this example, the optical isolator is constructed by arranging the second quarter-wave plate at a 45° clockwise angle relative to the second polarizing filter.

[0299] With the above settings, the second window allows linearly polarized light with an azimuth angle of 60° to pass through the light in the second wavelength region λ2.

[0300] (3) 3rd window part

[0301] The third window is the window that allows light from the third wavelength region λ3 to pass through.

[0302] like Figure 24 As shown, in the third window, a polarizing filter with a transmission axis angle of 0° is arranged as the first polarizing filter. Furthermore, in the third window, a quarter-wave plate with a fast axis angle of 45° is arranged as the first quarter-wave plate. That is, in the second window, a polarizing filter and a quarter-wave plate with the same structure as those in the first window are provided in front of the bandpass filter.

[0303] In the third window, a bandpass filter with a third wavelength region λ3 is further configured as a bandpass filter.

[0304] Furthermore, in the third window, a quarter-wave plate with a fast axis angle of 75° is arranged as the second quarter-wave plate. Also in the third window, a polarizing filter with a transmission axis angle of 120° is arranged as the second polarizing filter. The second polarizing filter and the second quarter-wave plate constitute the second optical isolator. In this example, the optical isolator is formed by arranging the second quarter-wave plate at a 45° clockwise angle relative to the second polarizing filter.

[0305] With the above settings, the third window allows linearly polarized light with an azimuth angle of 120° to pass through the light in the second wavelength region λ2.

[0306] (4) 4th window

[0307] The fourth window is the window that allows light in the fourth wavelength region λ4 to pass through.

[0308] like Figure 24 As shown, in the fourth window, a polarizing filter with a transmission axis angle of 0° is arranged as the first polarizing filter. Furthermore, in the fourth window, a quarter-wave plate with a fast axis angle of 45° is arranged as the first quarter-wave plate. That is, in the second window, a polarizing filter and a quarter-wave plate with the same structure as those in the first window are provided in front of the bandpass filter.

[0309] In the fourth window, a bandpass filter with a fourth wavelength region λ4 is further configured as a bandpass filter.

[0310] Furthermore, in the fourth window, a quarter-wave plate with a fast axis angle of 45° is arranged as the second quarter-wave plate. Also in the fourth window, a polarizing filter with a transmission axis angle of 90° is arranged as the second polarizing filter. The second polarizing filter and the second quarter-wave plate constitute the second optical isolator. In this example, the optical isolator is constructed by tilting the second quarter-wave plate counterclockwise by 45° relative to the second polarizing filter.

[0311] With the above settings, the fourth window allows linearly polarized light of the fourth wavelength region λ4 and an azimuth angle of 120° to pass through.

[0312] As described above, the four windows 122A to 122D in the filter unit 120 allow light with different wavelength regions and polarization directions to pass through.

[0313] [The shape of the window]

[0314] In the above embodiments, the shape of the window (opening shape) is set to a circular shape, but the shape of the window is not limited to this.

[0315] Figure 25This is another example of the shape of the window portion within a filter frame.

[0316] This figure illustrates an example with four windows 122A to 122D. In this example, the disc-shaped filter frame 122 is divided into four equal parts along its circumference to provide windows 122A to 122D with fan-shaped openings. Each window 122A to 122D has a fan-shaped filter group 170A to 170D.

[0317] [Examples of lens devices, filter units, and filter assemblies]

[0318] Regarding the lens assembly, it is preferable to have a structure in which the filter unit can be attached and detached relative to the lens housing. This allows for the replacement of the filter unit. Furthermore, it is also preferable to have a structure in which the filter assemblies installed in each window can be replaced. This allows for free switching of the number and combination of wavelengths used for beam splitting.

[0319] Furthermore, in a filter unit with a structure that allows for the replacement of filter groups, it is not necessary to use all the windows. For example, if a filter frame has four windows, when capturing an image with three wavelengths of light, one window can be used to block light. This allows for capturing an image with three wavelengths of light.

[0320] Furthermore, the filter assemblies installed in each window can be constructed by integrating (joining) filters with different functions, or by separating filters with different functions. In the integrated configuration, a structure can be formed where there is no air gap between the filters. The filters can be integrated, for example, by optical contact joining. Furthermore, in the case of a separate structure, filters can be used in any combination.

[0321] Furthermore, when the structure is configured to separate filters with each function, it is preferable that the filter unit be configured so that each filter can be individually installed in each window. This allows for arbitrary combination of filters installed in each window.

[0322] Image sensor

[0323] Color polarized image sensors can also be used in image sensors. For example, a color polarized image sensor is used when capturing an image with four wavelengths of light. A color polarized image sensor is a polarized image sensor where each pixel has a color filter. The color filters are arranged at specific positions in each pixel unit. For example, such as... Figure 8As shown, in a pixel unit PU composed of four pixels P1 to P4, a first color filter (e.g., a color filter that allows light in the green wavelength region to pass through) is disposed in the first pixel P1, a second color filter (e.g., a color filter that allows light in the red wavelength region to pass through) is disposed in the second pixel P2, a third color filter (e.g., a color filter that allows light in the blue wavelength region to pass through) is disposed in the third pixel P3, and a fourth color filter (e.g., a color filter that allows light in the infrared region to pass through) is disposed in the fourth pixel P4. In each pixel, the color filter is disposed, for example, between a microlens and a polarizer.

[0324] When using a color polarized image sensor, the interference rate is calculated by further considering the spectral transmittance information of the color filters in each pixel.

[0325] [Signal Processing Device]

[0326] In the multispectral camera system described above, the camera body and the signal processing device are separate components, but the signal processing device function can also be integrated into the camera body. Furthermore, it is also possible to configure the camera body to have only signal processing functionality.

[0327] Furthermore, the various functions of a signal processing device are implemented by various processors. These processors include general-purpose processors (CPUs and / or GPUs, Graphics Processing Units) that execute programs and function as various processing units; programmable logic devices (PLDs) such as FPGAs (Field Programmable Gate Arrays) whose circuit structures can be modified after manufacturing; and dedicated circuits such as ASICs (Application Specific Integrated Circuits) that have circuit structures specifically designed to perform specific processes. The definition of a program is the same as that of software.

[0328] A processing unit can be composed of one of these various processors, or it can be composed of two or more processors of the same or different types. For example, a processing unit can be composed of multiple FPGAs or a combination of a CPU and an FPGA. Furthermore, multiple processing units can also be composed of a single processor. As examples of multiple processing units composed of a single processor, firstly, there is the following: Represented by computers used for clients and servers, a single processor is composed of a combination of one or more CPUs and software, and this processor functions as multiple processing units. Secondly, there is the following: Represented by Systems on Chips (SoCs), a processor that implements the overall system functionality including multiple processing units using a single IC (Integrated Circuit) chip. Thus, regarding various processing units, as a hardware structure, one or more of the aforementioned processors are used.

[0329] Symbol Explanation

[0330] 1 - Multispectral camera system; 10 - Multispectral camera; 100 - Lens assembly; 110A - Lens group (first lens group); 110B - Lens group (second lens group); 120 - Filter unit; 122 - Filter frame; 122A - Window (first window); 122B - Window (second window); 122C - Window (third window); 122D - Window (fourth window); 124A - Filter group included in the first window; 124A1 - Bandpass filter; 124A2 - Quarter-wave plate; 124A3 - Polarizing filter; 124A4 - Optical isolator; 124B - Filter group included in the second window; 124B1 - Bandpass filter; 124B2 - Quarter-wave plate; 1 24B3 - Polarizing filter, 124B4 - Optical isolator, 124C - Filter group included in the third window, 124C1 - Bandpass filter, 124C2 - Quarter-wave plate, 124C3 - Polarizing filter, 124C4 - Optical isolator, 130A - Filter group included in the first window, 130A1 - First polarizing filter, 130A2 - First quarter-wave plate, 130A3 - Bandpass filter, 130A4 - Second quarter-wave plate, 130A5 - Second polarizing filter, 130A6 - First optical isolator, 130A7 - Second optical isolator, 130B - Filter group included in the second window, 130B1 - First polarizing filter, 130B2 - First quarter-wave plate One-wave plate, 130B3 - bandpass filter, 130B4 - second quarter-wave plate, 130B5 - second polarizing filter, 130B6 - first optical isolator, 130B7 - second optical isolator, 130C - filter group included in the third window, 130C1 - first polarizing filter, 130C2 - first quarter-wave plate, 130C3 - bandpass filter, 130C4 - second quarter-wave plate, 130C5 - second polarizing filter, 130C6 - first optical isolator, 130C7 - second optical isolator, 140A - filter group included in the first window, 140A1 - bandpass filter, 140A2 - quarter-wave plate, 140A3 - polarizing filter, 140A4 - Optical isolator; 140B - filter group included in the second window, 140B1 - bandpass filter, 140B2 - quarter-wave plate, 140B3 - polarizing filter, 140B4 - optical isolator, 140B5 - half-wave plate; 140C - filter group included in the third window, 140C1 - bandpass filter, 140C2 - quarter-wave plate, 140C3 - polarizing filter, 140C4 - optical isolator, 140C5 - half-wave plate; 150A - filter group included in the first window, 150A1 - first polarizing filter, 150A2 - quarter-wave plate, 150A3 - bandpass filter, 150A4 - second polarizing filter, 150A5 - optical isolator.150B - Filter group included in the second window, 150B1 - First polarizing filter, 150B2 - Quarter-wave plate, 150B3 - Bandpass filter, 150B4 - Second polarizing filter, 150B5 - Optical isolator; 150C - Filter group included in the third window, 150C1 - First polarizing filter, 150C2 - Quarter-wave plate, 150C3 - Bandpass filter, 150C4 - Second polarizing filter, 150C5 - Optical isolator; 160A - Filter group included in the first window, 160A1 - First polarizing filter, 160A2 - First quarter-wave plate, 160A3 - Bandpass filter, 160A4 - Second quarter-wave plate, 160A5 - Second... Polarizing filters, 160A6 - first optical isolator, 160A7 - second optical isolator, 160B - filter group included in the second window, 160B1 - first polarizing filter, 160B2 - first quarter-wave plate, 160B3 - bandpass filter, 160B4 - second quarter-wave plate, 160B5 - second polarizing filter, 160B6 - first optical isolator, 160B7 - second optical isolator, 160C - filter group included in the third window, 160C1 - first polarizing filter, 160C2 - first quarter-wave plate, 160C3 - bandpass filter, 160C4 - second quarter-wave plate, 160C5 - second polarizing filter, 160C6 - first optical isolator, 1 60C7 - Second optical isolator; 160D - Filter group in the fourth window; 160D1 - First polarizing filter; 160D2 - First quarter-wave plate; 160D3 - Bandpass filter; 160D4 - Second quarter-wave plate; 160D5 - Second polarizing filter; 160D6 - First optical isolator; 160D7 - Second optical isolator; 170A - Filter group in the first window; 170B - Filter group in the second window; 170C - Filter group in the third window; 170D - Filter group in the fourth window; 200 - Camera body; 210 - Image sensor (polarizing image sensor); 300 - Signal processing unit; 311 - CPU. 312-ROM, 313-RAM, 314-Auxiliary storage device, 315-Input device, 316-Output device, 317-Input / output interface, 320-Image data acquisition unit, 330-Image generation unit, 340-Output control unit, 350-Recording control unit, FAA-Arrow indicating the direction of the fast axis of the quarter-wave plate, FAB-Arrow indicating the direction of the fast axis of the quarter-wave plate, FAC-Arrow indicating the direction of the fast axis of the quarter-wave plate, L1-Reflected light, L2-Light reflected by the bandpass filter, L11-Reflected light, L12-Light reflected by the bandpass filter, L21-Reflected light, L22-Light reflected by the bandpass filter, LAA-Arrow indicating the direction of the slow axis of the quarter-wave plate.LAB - Arrow indicating the direction of the slow axis of the quarter-wave plate; LAC - Arrow indicating the direction of the slow axis of the quarter-wave plate; LPA - Arrow indicating the direction of the transmission axis of the polarizing filter; LPB - Arrow indicating the direction of the transmission axis of the polarizing filter; LPC - Arrow indicating the direction of the transmission axis of the polarizing filter; P1 - Pixel (1st pixel); P2 - Pixel (2nd pixel); P3 - Pixel (3rd pixel); P4 - Pixel (4th pixel); PU - Pixel unit; Z - Optical axis; α1 - Angle of the transmission axis of the 1st polarizer; α2 - Angle of the transmission axis of the 2nd polarizer; α3 - Angle of the transmission axis of the 3rd polarizer; α4 - Angle of the transmission axis of the 4th polarizer; θA - Angle of the transmission axis of the polarizing filter in the 1st window (1st angle); θB - Angle of the transmission axis of the polarizing filter in the 2nd window (2nd angle); θC - Angle of the transmission axis of the polarizing filter in the 3rd window (3rd angle).

Claims

1. A lens device comprising a filter unit in an optical path, wherein, The filter unit has multiple openings, including a first opening and a second opening. At least the first opening and the second opening are provided with bandpass filters, and optical elements are provided on the object side and the image side of the bandpass filters. The optical element consists of a polarizing filter and a quarter-wave plate tilted at 45° relative to the transmission axis of the polarizing filter. The quarter-wave plate is closer to the bandpass filter than the polarizing filter. The first opening and the second opening allow light of different wavelength regions and polarization directions to pass through. The angles of the fast axis of the quarter-wave plate are different on the object side and the image side of the bandpass filter.

2. The lens device according to claim 1, wherein, The filter unit is positioned at or near the pupil position.

3. The lens device according to claim 2, wherein, On the object side and image side of the bandpass filter, the fast axis of the quarter-wave plate is orthogonal.

4. The lens device according to claim 1 or 2, wherein, The polarizing filter is an absorption-type polarizing filter.

5. A camera device comprising: The lens device according to any one of claims 1 to 4; and A polarization image sensor that receives light passing through the lens device.

6. A lens device comprising a filter unit in an optical path, wherein, The filter unit has multiple openings, including a first opening and a second opening. At least the first opening and the second opening are provided with bandpass filters, and optical elements are provided on the object side and the image side of the bandpass filters. The optical element comprises a polarizing filter and a waveplate that converts linearly polarized light into circularly polarized or elliptically polarized light, and is disposed on the object side and image side of the bandpass filter. The waveplate is closer to the bandpass filter than the polarizing filter. The first opening and the second opening allow light of different wavelength regions and polarization directions to pass through. At least one of the first opening and the second opening further comprises a half-wave plate on the image side of the optical element disposed on the image side of the bandpass filter. On the object side and image side of the bandpass filter, the fast axis angles of the waveplate that converts linearly polarized light into circularly polarized light or elliptically polarized light are different.

7. The lens device according to claim 6, wherein, The waveplate that converts linearly polarized light into circularly polarized light or elliptically polarized light is a quarter-wave plate.

8. The lens device according to claim 6 or 7, wherein, The filter unit is positioned at or near the pupil position.

9. The lens device according to claim 6 or 7, wherein, In the first opening and the second opening, the transmission axis angles of the polarizing filter of the optical element disposed on the image side of the bandpass filter are equal.

10. The lens device according to claim 6 or 7, wherein, The polarizing filter is an absorption-type polarizing filter.

11. A camera device comprising: The lens device according to any one of claims 6 to 10; and A polarization image sensor that receives light passing through the lens device.

12. A filter unit disposed in the optical path of a lens assembly, wherein, The filter unit has multiple openings, including a first opening and a second opening. At least the first opening and the second opening are provided with bandpass filters, and optical elements are provided on the object side and the image side of the bandpass filters. The optical element consists of a polarizing filter and a quarter-wave plate tilted at 45° relative to the transmission axis of the polarizing filter. The quarter-wave plate is closer to the bandpass filter than the polarizing filter. The first opening and the second opening allow light of different wavelength regions and polarization directions to pass through. The angles of the fast axis of the quarter-wave plate are different on the object side and the image side of the bandpass filter.

Images