Lens device, filter unit, and imaging device

Abstract

The present invention provides a lens device, a filter unit, and an imaging apparatus with which it is possible to suppress occurrence of ghosts. This lens device is provided with a filter unit in an optical path. The filter unit has a plurality of openings including a first opening and a second opening, and at least the first opening and the second opening are each provided with a bandpass filter, and provided with an optical element on the object side and / or the image side of the bandpass filter. The optical element comprises a polarizing filter and a wavelength plate that converts linearly polarized light into circularly polarized light or elliptically polarized light, and light beams in wavelength regions and polarization directions different from each other pass through the first opening and the second opening.

Description

[Technical Field]

[0001] The present 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 that capture an image dispersed into a plurality of wavelengths. [Background technology]

[0002] Patent Document 1 describes an imaging device that captures an image separated into a plurality of wavelengths. Patent Document 1 describes, as a first embodiment, that a light-absorbing filter that absorbs light reflected from the imaging surface of the image sensor is disposed between the lens optical system and the image sensor. Patent Document 1 also describes, as a second embodiment, that a polarizer and a quarter-wave plate are disposed instead of the light-absorbing filter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-36127 Summary of the Invention

[0004] One embodiment of the technique of the present disclosure provides a lens device, a filter unit, and an imaging device that can suppress the occurrence of ghosts. [Means for solving the problem]

[0005] (1) A lens device having a filter unit in an optical path, the filter unit having a plurality of openings including a first opening and a second opening, at least the first opening and the second opening having a bandpass filter, and an optical element on at least one of the object side and the image side of the bandpass filter, the optical element being composed of 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 passing light of different wavelength ranges and polarization directions.

[0006] (2) The lens device of (1), wherein the wave plate is a quarter wave plate.

[0007] (3) The lens device of (1) or (2), wherein the filter unit is disposed at or near the pupil position.

[0008] (4) A lens device according to any one of (1) to (3), in which, when the optical element is arranged 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 arranged on the image side of the bandpass filter.

[0009] (5) The lens device according to (4), wherein the angles of the transmission axes of the polarizing filters of the optical elements arranged on the image side of the bandpass filter are equal in the first opening and the second opening.

[0010] (6) A lens device according to any one of (1) to (5), in which, 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 wave plate is different on the object side and the image side of the bandpass filter.

[0011] (7) The lens device of (6), in which the fast axes of the wave plates on the object side and the image side of the bandpass filter are orthogonal to each other.

[0012] (8) A lens device according to any one of (1) to (3), wherein when the optical element is arranged on the object side of the bandpass filter, the first opening and the second opening further comprise a polarizing filter on the image side of the bandpass filter.

[0013] (9) A lens device according to any one of (1) to (8), wherein the polarizing filter is an absorptive type.

[0014] (10) A filter unit arranged in the optical path of a lens device, the filter unit having a plurality of openings including a first opening and a second opening, at least the first opening and the second opening having a bandpass filter, and an optical element on at least one of the object side and the image side of the bandpass filter, the optical element being composed of 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 passing light of different wavelength ranges and polarization directions.

[0015] (11) The filter unit of (10), wherein the wave plate is a quarter wave plate.

[0016] (12) An imaging device comprising a lens device according to any one of (1) to (9) and a polarization image sensor that receives light that has passed through the lens device. [Brief explanation of the drawings]

[0017] [Figure 1] A diagram showing the schematic configuration of a multispectral camera system. [Figure 2] 1 is a diagram showing a schematic configuration of a filter unit; [Figure 3] FIG. 10 is a diagram showing an example of a polarizing filter provided in each window portion. [Figure 4] FIG. 10 is a diagram showing an example of a polarizing filter provided in each window portion. [Figure 5] FIG. 10 is a diagram showing an example of a quarter-wave plate provided in each window portion. [Figure 6] FIG. 10 is a diagram showing an example of the configuration of a filter group provided in each window portion; [Figure 7] Diagram explaining the function of optical isolators to prevent re-reflection [Figure 8] FIG. 1 is a diagram showing an example of the arrangement of pixels and polarizers in a polarization image sensor. [Figure 9] FIG. 1 is a diagram illustrating an example of a hardware configuration of a signal processing device. [Figure 10] Block diagram of functions possessed by a signal processing device [Figure 11] 10A and 10B are diagrams showing modified examples of the filter group provided in each window portion; [Figure 12] 1 is a diagram showing a schematic configuration of a filter unit; [Figure 13] FIG. 10 is a diagram showing an example of the configuration of a filter group provided in each window portion; [Figure 14] Diagram explaining the function of preventing re-reflection using front and rear optical isolators [Figure 15] 10A and 10B are diagrams showing modified examples of the filter group provided in each window portion; [Figure 16] 1 is a diagram showing a schematic configuration of a filter unit; [Figure 17] FIG. 10 is a diagram showing an example of the configuration of a filter group provided in each window portion; [Figure 18] 10A and 10B are diagrams showing modified examples of the filter group provided in each window portion; [Figure 19] FIG. 1 shows an example of the configuration of a filter group provided in each window when optical isolators are placed before and after a bandpass filter. [Figure 20] 1 is a diagram showing a schematic configuration of a filter unit; [Figure 21] FIG. 10 is a diagram showing an example of the configuration of a filter group provided in each window portion; [Figure 22] 10A and 10B are diagrams showing modified examples of the filter group provided in each window portion; [Figure 23] FIG. 10 is a diagram showing an example of the configuration of a filter unit when capturing images by dispersing light into four wavelengths. [Figure 24] FIG. 10 is a diagram showing an example of the configuration of a filter group provided in each window portion; [Figure 25] FIG. 10 is a diagram showing another example of the shape of a window portion provided in a filter frame; DETAILED DESCRIPTION OF THE INVENTION

[0018] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] [First embodiment] Here, an example will be described in which the present invention is applied to a multispectral camera system. A multispectral camera system is a system that simultaneously captures images separated into multiple wavelengths. Here, an example will be described in which images separated into three wavelengths are simultaneously captured.

[0020] [Configuration of multispectral camera system] FIG. 1 is a diagram showing a schematic configuration of a multispectral camera system.

[0021] The multispectral camera system shown in the figure is a so-called polarization-type multispectral camera system. A polarization-type multispectral camera system is a multispectral camera system that uses polarized light. As shown in the figure, the multispectral camera system 1 is mainly composed of a multispectral camera 10 and a signal processing device 300. The multispectral camera 10 is composed of a lens device 100 and a camera body 200. The multispectral camera 10 is an example of an imaging device.

[0022] [Lens device] As shown in FIG. 1, the lens device 100 includes a plurality of lens groups 110A and 110B and a filter unit 120.

[0023] Each of the lens groups 110A and 110B is composed of at least one lens. For convenience, only two lens groups 110A and 110B are shown in FIG. 1. Hereinafter, as necessary, the two lens groups 110A and 110B will be distinguished by referring to the lens group 110A arranged in front of the filter unit 120 as the first lens group and the lens group 110B arranged in back of the filter unit 120 as the second lens group. Note that "front side" means "object side" and "rear side" means "image side."

[0024] 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 apparatus 100. Note that the vicinity of the pupil position refers to an area that satisfies the following formula: |d| < φ / (2tanθ) θ: Maximum chief ray angle at pupil position (the chief ray angle is the angle with the optical axis) φ: Pupil diameter |d|: distance from pupil position

[0025] FIG. 2 is a diagram showing a schematic configuration of the filter unit.

[0026] The filter unit 120 is composed of a filter frame 122 and three filter groups 124A, 124B, and 124C attached to the filter frame 122.

[0027] Filter frame 122 has a plate-like shape corresponding to the inner circumferential shape of the lens barrel and has multiple windows. As shown in Figure 2, filter frame 122 of this embodiment has a circular plate shape and has three windows 122A, 122B, and 122C.

[0028] The three window portions 122A, 122B, and 122C are formed by circular openings and are arranged at equal intervals along the circumferential direction. The window portions 122A, 122B, and 122C are an example of an opening portion. Hereinafter, as necessary, the window portion 122A will be referred to as the first window portion, the window portion 122B as the second window portion, and the window portion 122C as the third window portion to distinguish between the window portions 122A, 122B, and 122C. The first window portion 122A is an example of a first opening portion. The second window portion 122B is an example of a second opening portion.

[0029] Filter groups 124A, 124B, and 124C are attached to the three window portions 122A, 122B, and 122C, respectively.

[0030] Each of the three filter groups 124A, 124B, and 124C is composed of three filters. The three filters are band-pass filters (BPFs) 124A1, 124B1, and 124C1, quarter-wave plates (QWPs) 124A2, 124B2, and 124C2, and polarized light filters (PLFs) 124A3, 124B3, and 124C3. The three filters are arranged along the optical axis Z in the following order from the object side: band-pass filters 124A1, 124B1, and 124C1, quarter-wave plates 124A2, 124B2, and 124C2, and polarized light filters 124A3, 124B3, and 124C3.

[0031] The three windows 122A, 122B, and 122C are provided with bandpass filters 124A1, 124B1, and 124C1, respectively, that transmit different wavelength ranges. The bandpass filter 124A1 provided in the first window 122A transmits light in a first wavelength range λ1. The bandpass filter 124B1 provided in the second window 122B transmits light in a second wavelength range λ2 (λ2≠λ1). The bandpass filter 124C1 provided in the third window 122C transmits light in a third wavelength range λ3 (λ3≠λ1, λ3≠λ2).

[0032] It is preferable to use reflective bandpass filters 124A1, 124B1, and 124C1 in view of the high degree of freedom in spectral transmission characteristics.

[0033] The three windows 122A, 122B, and 122C are provided with polarizing filters 124A3, 124B3, and 124C3, respectively, with different angles of transmission axes. The polarizing filter 124A3 provided in the first window 122A has its transmission axis set at a first angle θA. The polarizing filter 124B3 provided in the second window 122B has its transmission axis set at a second angle θB (θB ≠ θA). The polarizing filter 124C3 provided in the third window 122C has its transmission axis set at a third angle θC (θC ≠ θA, θC ≠ θA).

[0034] 3 is a diagram showing an example of the polarizing filters provided in each window portion, which shows the settings of the transmission axes of the polarizing filters 124A3, 124B3, and 124C3 when the filter unit 120 is viewed from the object side (front side).

[0035] 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 portion 122A is set to θA = 0°, the transmission axis of the polarizing filter 124B3 provided in the second window portion 122B is set to θB = 60°, and the transmission axis of the polarizing filter 124C3 provided in the third window portion 122C is set to θC = 120°.

[0036] The angle parallel to the X-axis is defined as 0°, and the counterclockwise direction as viewed from the object side (front side) is defined as the positive (+) direction. Therefore, a transmission axis of 60° means that the axis is tilted 60° counterclockwise with respect to the X-axis. Furthermore, a transmission axis of 120° means that the axis is tilted 120° counterclockwise with respect to the X-axis.

[0037] The X-axis is an axis set in a plane perpendicular to the optical axis Z. In the plane perpendicular to the optical axis Z, the axis perpendicular to the X-axis is defined as the Y-axis. As will be described later, the image sensor provided in the camera body 200 has its upper and lower sides of the light receiving surface arranged parallel to the X-axis. Furthermore, its left and right sides are arranged parallel to the Y-axis.

[0038] As will be described later, it is preferable to use absorption type polarizing filters 124A3, 124B3, and 124C3 in order to suppress ghosting.

[0039] The quarter-wave plates 124A2, 124B2, and 124C2 provided in each window are arranged so as to be tilted by 45° with respect to the polarizing filters 124A3, 124B3, and 124C3 provided in each window. More specifically, the fast axes (high-speed axes) are arranged so as to be tilted by 45° with respect to the transmission axes of the polarizing filters 124A3, 124B3, and 124C3 provided in each window. In this embodiment, the fast axes are arranged so as to be tilted by 45° counterclockwise.

[0040] Fig. 4 is a diagram showing an example of a polarizing filter provided in each window portion, Fig. 5 is a diagram showing an example of a quarter-wave plate provided in each window portion, and Fig. 6 is a diagram showing an example of the configuration of a filter group provided in each window portion.

[0041] In FIG. 4, long arrows LPA, LPB, LPC in each window 122A, 122B, 122C indicate the directions of the transmission axes of polarizing filters 124A3, 124B3, 124C3 provided in each window 122A, 122B, 122C.

[0042] In addition, in FIG. 5, arrows FAA, FAB, and FAC in the windows 122A, 122B, and 122C indicate the directions of the fast axes of the quarter-wave plates 124A2, 124B2, and 124C2 provided in the windows 122A, 122B, and 122C, respectively.

[0043] As shown in FIGS. 4 to 6, the quarter-wave plates 124A2, 124B2, and 124C2 provided in the respective window portions 122A, 122B, and 122C are disposed at an angle of 45° counterclockwise with respect to the transmission axes of the polarization filters 124A3, 124B3, and 124C3 provided in the respective window portions (i.e., are disposed rotated 45° counterclockwise). Specifically, a quarter-wave plate having a fast axis angle of 45° is disposed in the first window portion. A quarter-wave plate having a fast axis angle of 105° is disposed in the second window portion. A quarter-wave plate having a fast axis angle of 165° is disposed in the third window portion.

[0044] 5, the short arrows LAA, LAB, and LAC in the windows 122A, 122B, and 122C indicate the direction of the slow axis (slow axis) of the quarter-wave plates 124A2, 124B2, and 124C2 provided in the windows 122A, 122B, and 122C, respectively. The slow axis is perpendicular to the fast axis.

[0045] As described above, each window 122A, 122B, 122C is provided with a filter group 124A, 124B, 124C, which includes bandpass filters 124A1, 124B1, 124C1, quarter-wave plates 124A2, 124B2, 124C2, and polarizing filters 124A3, 124B3, 124C3. Of these, the quarter-wave plates 124A2, 124B2, 124C2 and the polarizing filters 124A3, 124B3, 124C3 are combined to form optical isolators 124A4, 124B4, 124C4. The quarter-wave plates 124A2, 124B2, and 124C2 and the polarizing filters 124A3, 124B3, and 124C3 constitute optical isolators 124A4, 124B4, and 124C4, which prevent re-reflection of returning light on the rear surfaces of the band-pass filters 124A1, 124B1, and 124C1 behind the band-pass filters 124A1, 124B1, and 124C1. The optical isolators 124A4, 124B4, and 124C4 are examples of optical elements. The quarter-wave plates 124A2, 124B2, and 124C2 are examples of wave plates that convert linearly polarized light into circularly polarized light or elliptically polarized light.

[0046] FIG. 7 is a diagram illustrating the function of preventing re-reflection by an optical isolator.

[0047] This figure shows an example in which light (returned light) reflected by the second lens group 110B enters the first window portion 122A. The returned light also includes light reflected by the light receiving surface of the image sensor, for example. This figure corresponds to the cross section taken along line 7-7 in FIG. 3.

[0048] The return light L1, which is reflected by the second lens group 110B and enters the first window portion 122A, enters the bandpass filter 124A1 via the optical isolator 124A4. At this time, the return light L1 passes through the polarizing filter 124A3 and the quarter-wave plate 124A2 in that order, and then enters the optical isolator 124A4 and enters the bandpass filter 124A1. During this process, the return light L1 is converted into circularly polarized light. When the circularly polarized light is reflected by the bandpass filter 124A1 and enters the quarter-wave plate 124A2 again, it returns to linearly polarized light rotated by 90 degrees. The light L2, whose direction has changed, is prevented from passing by the polarizing filter 124A3. This prevents re-reflection of the return light. By preventing re-reflection of this return light, ghosts can be effectively suppressed.

[0049] In this way, since the polarizing filters 124A3, 124B3, and 124C3 have the function of preventing light from passing through due to re-reflection at the band-pass filters 124A1, 124B1, and 124C1, it is preferable to use an absorption type.

[0050] [Camera body] As shown in FIG. 1, the camera body 200 has an image sensor 210. The image sensor 210 is disposed on the optical axis of the lens device 100 and receives light that has passed through the lens device 100. This image sensor 210 is configured as a polarization image sensor. A polarization image sensor is an image sensor equipped with a polarizer, and a polarizer is provided for each pixel. The polarizer is provided, for example, between a microlens and a photodiode. Note that this type of polarization image sensor is publicly known (for example, International Publication No. 2020 / 071253, etc.), and therefore detailed description thereof will be omitted.

[0051] The direction (angle of the transmission axis) of the polarizer mounted on the polarization image sensor is selected according to the number of wavelengths to be captured. In this embodiment, an image separated into three wavelengths is captured. In this case, a polarization image sensor equipped with polarizers in at least three directions is used. In this embodiment, a polarization image sensor equipped with polarizers in four directions is used.

[0052] FIG. 8 is a diagram showing an example of the arrangement of pixels and polarizers in a polarization image sensor.

[0053] As shown in the figure, four polarizers with different transmission axis angles are regularly arranged with respect to the pixels arranged in a matrix. The polarizer with a transmission axis angle of α1 is referred to as the first polarizer, the polarizer with a transmission axis angle of α2 is referred to as the second polarizer, the polarizer with a transmission axis angle of α3 is referred to as the third polarizer, and the polarizer with a transmission axis angle of α4 is referred to 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°.

[0054] The pixel P1 equipped with the first polarizer is referred to as the first pixel, the pixel P2 equipped with the second polarizer is referred to as the second pixel, the pixel P3 equipped with the third polarizer is referred to as the third pixel, and the pixel P4 equipped with the fourth polarizer is referred to as the fourth pixel. A 2x2 pixel group consisting of the first pixel P1, the second pixel P2, the third pixel P3, and the fourth pixel P4 is referred to as one unit (pixel unit) PU, and this pixel unit PU is repeatedly arranged along the X-axis and the Y-axis.

[0055] A polarization image sensor equipped with polarizers in four directions like this can capture a polarized image in four directions in one shot.

[0056] The image sensor 210 is configured, for example, as a CMOS (Complementary Metal Oxide Semiconductor) type including a driver, an ADC (Analog to Digital Converter), a signal processor, and the like. In this case, the image sensor 210 is driven by the built-in driver to operate. The signal of each pixel is converted into a digital signal by the built-in ADC and output. Furthermore, the signal of each pixel is subjected to correlated double sampling processing, gain processing, correction processing, and the like by the built-in signal processor before being output. The signal processing may be performed after or before conversion into a digital signal.

[0057] In addition to image sensor 210, camera body 200 is equipped with an output unit (not shown) that outputs data of an image captured by image sensor 210, a camera control unit (not shown) that controls the overall operation of camera body 200, and the like. The camera control unit is composed of, for example, a processor. The processor functions as the camera control unit by executing a predetermined control program.

[0058] The image data output from the camera body 200 is so-called RAW image data. That is, it is unprocessed image data. This RAW image data is processed by the signal processing device 300, and an image is generated that is spectrally separated into multiple wavelengths.

[0059] [Signal processing device] As described above, signal processing device 300 processes image data (RAW image data) output from camera body 200 to generate images separated into a plurality of wavelengths. More specifically, it generates images of wavelengths corresponding to the transmission wavelength ranges of the bandpass filters provided in each window of lens device 100. In this embodiment, it generates images of three wavelengths, including an image in a first wavelength range λ1 (first image), an image in a second wavelength range λ2 (second image), and an image in a third wavelength range λ3 (third image).

[0060] FIG. 9 is a diagram illustrating an example of a hardware configuration of a signal processing device.

[0061] 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. Such a signal processing device 300 is configured, for example, by a general-purpose computer such as a personal computer.

[0062] The signal processing device 300 functions as a signal processing device when a CPU 311, which is a processor, executes a predetermined program (signal processing program). The program executed by the CPU 311 is stored in the ROM 312 or the auxiliary storage device 314.

[0063] The auxiliary storage device 314 constitutes a storage unit of the signal processing device 300. The auxiliary storage device 314 is constituted by, for example, a hard disk drive (HDD) or a solid state drive (SSD).

[0064] The input device 315 constitutes an operation unit of the signal processing device 300. The input device 315 is constituted by, for example, a keyboard, a mouse, a touch panel, and the like.

[0065] The output device 316 constitutes a display unit of the signal processing device 300. The output device 316 is constituted by a display such as a liquid crystal display (Liquid Crystal Display) or an organic light emitting diode display (Organic EL Display).

[0066] The input / output interface 317 constitutes a connection section of the signal processing device 300. The signal processing device 300 is connected to the camera body 200 via the input / output interface 317.

[0067] FIG. 10 is a block diagram of the functions of the signal processing device.

[0068] 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 realized by a CPU 311 executing a predetermined program.

[0069] Image data acquisition section 320 acquires image data obtained by capturing an image from camera body 200. As described above, the image data acquired from camera body 200 is RAW image data.

[0070] The image generation unit 330 performs predetermined 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 in a first wavelength band λ1 (first image), an image in a second wavelength band λ2 (second image), and an image in a third wavelength band λ3 (third image) are generated. The image generation unit 330 performs processing on the image data acquired by the image data acquisition unit 320 to remove interference in pixel units, and generates images for each of the wavelength bands λ1, λ2, and λ3. This processing will be outlined below.

[0071] As described above, a polarization image sensor equipped with a four-directional polarizer can capture a four-directional polarization image in one shot. These four-directional polarization images contain image components in the wavelength ranges λ1, λ2, and λ3 at a predetermined ratio (crosstalk ratio). The crosstalk ratio is determined by the angle of the transmission axis of the polarization filter provided in each window of the filter unit 120 and the angle of the transmission axis of the polarizer provided in each pixel, and is known. Images in each wavelength range can then be generated using this crosstalk ratio information.

[0072] In the image captured by the image sensor 210, the pixel value of the first pixel P1 is x1, the pixel value of the second pixel P2 is x2, the pixel value of the third pixel P3 is x3, and the pixel value of the fourth pixel P4 is x4.

[0073] 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 to X2, and the pixel value of the corresponding pixel in the third image to X3.

[0074] If the proportion of light in the first wavelength band λ1 received by the first pixel P1 is b11, the proportion of light in the second wavelength band λ2 received by the first pixel P1 is b12, and the proportion of light in the third wavelength band λ3 received by the first pixel P1 is b13, then the following relationship holds between X1, X2, X3, and x1. b11*X1+b12*X2+b13*X3=x1…(Formula 1)

[0075] Furthermore, if the proportion of light in the first wavelength band λ1 received by the second pixel P2 is b21, the proportion of light in the second wavelength band λ2 received by the second pixel P2 is b22, and the proportion of light in the third wavelength band λ3 received by the second pixel P2 is b23, then the following relationship holds between X1, X2, X3, and x2. b21*X1+b22*X2+b23*X3=x2…(Formula 2)

[0076] Furthermore, if the proportion of light in the first wavelength band λ1 received by the third pixel P3 is b31, the proportion of light in the second wavelength band λ2 received by the third pixel P3 is b32, and the proportion of light in the third wavelength band λ3 received by the third pixel P3 is b33, then the following relationship holds between X1, X2, X3, and x3. b31*X1+b32*X2+b33*X3=x3…(Formula 3)

[0077] Furthermore, if the proportion of light in the first wavelength band λ1 received by the fourth pixel P4 is b41, the proportion of light in the second wavelength band λ2 received by the fourth pixel P4 is b42, and the proportion of light in the third wavelength band λ3 received by the fourth pixel P4 is b43, then the following relationship holds between X1, X2, X3, and x4. b41*X1+b42*X2+b43*X3=x4…(Formula 4)

[0078] By solving the simultaneous equations of the above expressions 1 to 4 for X1, X2, and X3, the pixel values ​​X1, X2, and X3 of the corresponding pixels in the first, second, and third images can be obtained.

[0079] In this way, by using the information on the interference rate, it is possible to generate images in each wavelength range from the images captured by the image sensor.

[0080] Here, the above simultaneous equations can be expressed as an expression using a matrix. Furthermore, X1, X2, and X3 can be calculated by multiplying both sides of the matrix by the inverse matrix. The signal processing device 300 holds each element of this inverse matrix as a coefficient group. Information about the coefficient group is stored in, for example, the auxiliary storage device 314. The image generation unit 330 acquires the information about the coefficient group from the auxiliary storage device 314 and generates images for each wavelength band.

[0081] The output control unit 340 controls the output of the images (first image, second image, and third image) in each wavelength range generated by the image generation unit 330. In this embodiment, the output control unit 340 controls the output (display) to the display, which is the output device 316.

[0082] In response to an instruction from a user, the recording control unit 350 controls the recording of the images in each wavelength range generated by the image generation unit 330. The generated images in each wavelength range are recorded in the auxiliary storage device 314.

[0083] [Multispectral camera system operation] The multispectral camera system 1 of this embodiment configured as described above can simultaneously capture images separated into three wavelengths. The three wavelengths correspond to the transmission wavelength ranges of the three bandpass filters 124A1, 124B1, and 124C1 provided in the lens device 100. Therefore, by changing the bandpass filter, images in different wavelength ranges can be captured.

[0084] Incidentally, it is preferable to use a reflective bandpass filter because of the high degree of freedom in spectral transmission characteristics. However, when a reflective bandpass filter is used, there is a concern that ghosts may occur due to reflection from the bandpass filter.

[0085] However, according to the lens device 100 of the present embodiment, the optical isolators 124A4, 124B4, and 124C4 are provided in the respective window portions 122A, 122B, and 122C, so that reflection from the bandpass filters 124A1, 124B1, and 124C1 can be suppressed. This effectively suppresses the occurrence of ghosts. This also allows high-quality images to be captured.

[0086] [Variations] [Modification of the configuration of the filter group provided in each window] As described above, the quarter-wave plates placed in each window of the filter unit are arranged in combination with the polarizing filters to form an optical isolator, with their fast axes tilted 45° to the transmission axis of the polarizing filters.

[0087] FIG. 11 is a diagram showing a modified example of the filter group provided in each window portion.

[0088] In this example, the setting of the quarter wave plate provided in each window portion is different from that of the filter unit in the above embodiment.

[0089] As shown in the figure, a quarter-wave plate with a fast axis angle of 135° is placed in the first window. A quarter-wave plate with a fast axis angle of 15° is placed in the second window. A quarter-wave plate with a fast axis angle of 75° is placed in the third window. In other words, in this example, the quarter-wave plate is tilted 45° clockwise with respect to the polarizing filter. In this case, as with the lens device of the above embodiment, an optical isolator can be configured using the quarter-wave plate and the polarizing filter.

[0090] [Modification of optical isolator] An optical isolator can also be configured by using a 1 / 8 wavelength plate instead of a 1 / 4 wavelength plate. That is, an optical isolator can be configured by using a 1 / 8 wavelength plate instead of a 1 / 4 wavelength plate and combining that 1 / 8 wavelength plate with a polarizing filter.

[0091] [Second embodiment] In the lens device of the first embodiment, an optical isolator is arranged behind (on the image side of) the bandpass filter in each window. In the lens device of this embodiment, optical isolators are arranged before and after the bandpass filter, i.e., on the object side and image side. Note that the configuration other than the filter unit is the same as that of the lens device of the first embodiment. Therefore, only the configuration of the filter unit will be described below.

[0092] FIG. 12 is a diagram showing a schematic configuration of the filter unit.

[0093] As shown in the figure, filter groups 130A, 130B, and 130C are provided in three window portions 122A, 122B, and 122C, respectively, provided in the filter frame 122. Each of the filter groups 130A, 130B, and 130C is made up of five filters.

[0094] The five filters are composed of first polarizing filters 130A1, 130B1, and 130C1, first quarter-wave plates 130A2, 130B2, and 130C2, bandpass filters 130A3, 130B3, and 130C3, second quarter-wave plates 130A4, 130B4, and 130C4, and second polarizing filters 130A5, 130B5, and 130C5. The five filters are arranged along the optical axis Z in the following order from the object side: first polarizing filters 130A1, 130B1, 130C1, first quarter-wave plates 130A2, 130B2, 130C2, bandpass filters 130A3, 130B3, 130C3, second quarter-wave plates 130A4, 130B4, 130C4, and second polarizing filters 130A5, 130B5, 130C5.

[0095] In each of the windows 122A, 122B, and 122C, the first polarization filters 130A1, 130B1, and 130C1 and the first quarter-wave plates 130A2, 130B2, and 130C2 constitute first optical isolators 130A6, 130B6, and 130C6 in front of (on the object side of) the bandpass filters 130A3, 130B3, and 130C3. The second quarter-wave plates 130A4, 130B4, and 130C4 and the second polarization filters 130A5, 130B5, and 130C5 constitute second optical isolators 130A7, 130B7, and 130C7 in back of (on the image side of) the bandpass filters 130A3, 130B3, and 130C3.

[0096] To form an optical isolator, the first quarter-wave plates 130A2, 130B2, and 130C2 are tilted at 45° with respect to the first polarizing filters 130A1, 130B1, and 130C1, and the second quarter-wave plates 130A4, 130B4, and 130C4 are tilted at 45° with respect to the second polarizing filters 130A5, 130B5, and 130C5.

[0097] FIG. 13 is a diagram showing an example of the configuration of a filter group provided in each window portion.

[0098] (1) First window The first window transmits light in the first wavelength band λ1.

[0099] As shown in Fig. 13, a polarizing filter with a transmission axis angle of 0° is placed in the first window as a first polarizing filter. Also, a quarter-wave plate with a fast axis angle of 135° is placed in the first window as a first quarter-wave plate. This first polarizing filter and first quarter-wave plate form a first optical isolator. In this example, the optical isolator is formed by placing the first quarter-wave plate at an angle of 45° clockwise with respect to the first polarizing filter.

[0100] Furthermore, a bandpass filter of a first wavelength band λ1 is disposed in the first window portion.

[0101] Furthermore, a quarter-wave plate with a fast axis angle of 45° is disposed in the first window as a second quarter-wave plate. Furthermore, a polarizing filter with a transmission axis angle of 0° is disposed in the first window as a second polarizing filter. This second polarizing filter and the second quarter-wave plate form a second optical isolator. In this example, the optical isolator is formed by disposing the second quarter-wave plate at an angle of 45° counterclockwise with respect to the second polarizing filter.

[0102] With the above settings, the first window portion passes light in the first wavelength band λ1 that is linearly polarized light with an azimuth angle of 0°. Specifically, first, the light passes through the first polarizing filter to become linearly polarized light with an azimuth angle of 0°. Next, the light passes through the first quarter-wave plate to be converted into circularly polarized light. Next, the light passes through the bandpass filter to become light in the first wavelength band λ1. Next, the light passes through the second quarter-wave plate to be converted back into linearly polarized light. Finally, the light passes through the second polarizing filter to become linearly polarized light with an azimuth angle of 0°.

[0103] (2) Second window The second window is a window that transmits light in the second wavelength band λ2.

[0104] As shown in Fig. 13, a polarizing filter with a transmission axis angle of 60° is placed in the second window as a first polarizing filter. Also, a quarter-wave plate with a fast axis angle of 15° is placed in the second window as a first quarter-wave plate. This first polarizing filter and first quarter-wave plate form a first optical isolator. In this example, the optical isolator is formed by placing the first quarter-wave plate at a 45° clockwise angle with respect to the first polarizing filter.

[0105] Furthermore, a bandpass filter of a second wavelength band λ2 is disposed in the second window portion.

[0106] Furthermore, a quarter-wave plate with a fast axis angle of 105° is disposed in the second window as a second quarter-wave plate. Furthermore, a polarizing filter with a transmission axis angle of 60° is disposed in the second window as a second polarizing filter. This second polarizing filter and the second quarter-wave plate form a second optical isolator. In this example, the optical isolator is formed by disposing the second quarter-wave plate at an angle of 45° counterclockwise with respect to the second polarizing filter.

[0107] With the above settings, the second window portion transmits light in the second wavelength band λ2 that is linearly polarized with an azimuth angle of 60°. Specifically, the light first passes through the first polarizing filter, becoming linearly polarized light with an azimuth angle of 60°. Next, the light passes through the first quarter-wave plate, where it is converted into circularly polarized light. Next, the light passes through the bandpass filter, becoming light in the first wavelength band λ1. Next, the light passes through the second quarter-wave plate, where it is converted back into linearly polarized light. Finally, the light passes through the second polarizing filter, becoming linearly polarized light with an azimuth angle of 60°.

[0108] (3) Third window The third window is a window that transmits light in the third wavelength band λ3.

[0109] As shown in Fig. 13, a polarizing filter with a transmission axis angle of 120° is placed in the third window as a first polarizing filter. Also, a quarter-wave plate with a fast axis angle of 75° is placed in the third window as a first quarter-wave plate. This first polarizing filter and first quarter-wave plate form a first optical isolator. In this example, the optical isolator is formed by placing the first quarter-wave plate at a 45° clockwise angle with respect to the first polarizing filter.

[0110] Furthermore, a bandpass filter of a third wavelength band λ3 is disposed in the third window portion.

[0111] Furthermore, a quarter-wave plate with a fast axis angle of 165° is disposed in the third window as a second quarter-wave plate. Furthermore, a polarizing filter with a transmission axis angle of 120° is disposed in the third window as a second polarizing filter. This second polarizing filter and the second quarter-wave plate form a second optical isolator. In this example, the optical isolator is formed by disposing the second quarter-wave plate at an angle of 45° counterclockwise with respect to the second polarizing filter.

[0112] With the above settings, the third window portion transmits light in the third wavelength band λ3 that is linearly polarized with an azimuth angle of 120°. Specifically, the light first passes through the first polarizing filter, becoming linearly polarized light with an azimuth angle of 120°. Next, the light passes through the first quarter-wave plate, where it is converted into circularly polarized light. Next, the light passes through the bandpass filter, becoming light in the first wavelength band λ1. Next, the light passes through the second quarter-wave plate, where it is converted back into linearly polarized light. Finally, the light passes through the second polarizing filter, becoming linearly polarized light with an azimuth angle of 120°.

[0113] As described above, the windows provided in the filter unit 120 transmit light of different wavelength ranges and polarization directions.

[0114] FIG. 14 is a diagram illustrating the function of preventing re-reflection by the front and rear optical isolators.

[0115] The figure shows the light reflected by the first lens group 110A (return light), and Beauty, An example is shown in which light reflected by the second lens group 110B (returned light) enters the first window portion 122A.

[0116] The return light L11, which is reflected by the first lens group 110A and enters the first window portion 122A, enters the bandpass filter 130A3 via the first optical isolator 130A6. At this time, the return light L11 passes through the first polarizing filter 130A1 and the first quarter-wave plate 130A2 in that order, and then passes through the first optical isolator 130A6 before entering the bandpass filter 130A3. During this process, the return light L11 is converted into circularly polarized light. When the circularly polarized light is reflected by the bandpass filter 130A3 and enters the first quarter-wave plate 130A2 again, it returns to linearly polarized light rotated 90 degrees. The light L12, whose direction has changed, is prevented from passing by the first polarizing filter 130A1. This prevents the return light from being reflected again on the front side (object side).

[0117] Meanwhile, the return light L21, which is reflected by the second lens group 110B and enters the first window portion 122A, enters the bandpass filter 130A3 via the second optical isolator 130A7. At this time, the return light L21 passes through the second polarizing filter 130A5 and the second quarter-wave plate 130A4 in that order, and then enters the second optical isolator 130A7 and enters the bandpass filter 130A3. During this process, the return light L21 is converted into circularly polarized light. When the circularly polarized light is reflected by the bandpass filter 130A3 and enters the second quarter-wave plate 130A4 again, it returns to linearly polarized light rotated 90 degrees. The light L22, whose direction has changed, is blocked from passing by the second polarizing filter 130A5. This prevents the return light from being reflected again.

[0118] In this way, the lens device of this embodiment can prevent re-reflection of returning light before and after the bandpass filter, thereby more effectively suppressing ghosts.

[0119] [Variations] [Modification of the configuration of the filter group provided in each window] As described above, the quarter-wave plate and the polarizing filter, which are placed before and after the bandpass filter, are combined to form an optical isolator. Specifically, the quarter-wave plate is tilted 45° relative to the polarizing filter.

[0120] [First Modification] FIG. 15 is a diagram showing a modified example of the filter group provided in each window portion.

[0121] FIG. 15(A) shows a first modified example of a filter group arranged in each window portion.

[0122] In this example, the settings of the first and second quarter wave plates in each window are different from those in the filter unit of the above embodiment.

[0123] As shown in the figure, a quarter-wave plate with a fast axis angle of 45° is disposed in the first window as the first quarter-wave plate. Furthermore, a quarter-wave plate with a fast axis angle of 105° is disposed in the second window as the first quarter-wave plate. Furthermore, a quarter-wave plate with a fast axis angle of 165° is disposed in the third window as the first quarter-wave plate. That is, in this example, the first quarter-wave plate is disposed at an angle of 45° clockwise with respect to the first polarizing filter. In this case, as with the filter unit of the above embodiment, a first optical isolator can be configured using the first quarter-wave plate and the first polarizing filter.

[0124] As shown in the figure, a quarter-wave plate with a fast axis angle of 135° is disposed in the first window as the second quarter-wave plate. A quarter-wave plate with a fast axis angle of 15° is disposed in the second window as the second quarter-wave plate. A quarter-wave plate with a fast axis angle of 75° is disposed in the third window as the second quarter-wave plate. That is, in this example, the second quarter-wave plate is tilted 45° counterclockwise with respect to the second polarizing filter. In this case, as with the filter unit of the above embodiment, a second optical isolator can be configured using the second quarter-wave plate and the second polarizing filter.

[0125] [Second Modification] FIG. 15(B) shows a second modified example of the filter group provided in each window portion.

[0126] In this example, the configuration of the first optical isolator in each window portion differs from that of the filter unit in the above embodiment.

[0127] As shown in the figure, the first optical isolator in each window receives the first polarized light with a transmission axis angle of 0°. filter and a first quarter-wave plate with a fast axis angle of 135°. That is, in the filter unit of this example, each window portion is provided with a first optical isolator of the same configuration.

[0128] The polarization direction of the light passing through each window is ultimately determined by the second polarizing filter, so the first optical isolator can have the same configuration for each window.

[0129] [Third Modification] FIG. 15(C) shows a third modified example of the filter group provided in each window portion.

[0130] In this example, the configuration of the first optical isolator is different from that of the filter unit in the above embodiment. Ta The difference from the second modified example is the setting of the first quarter-wave plate that constitutes the first optical isolator. As shown in the figure, the first quarter-wave plate is a quarter-wave plate with a fast axis angle of 45°. In other words, the first quarter-wave plate is tilted 45° clockwise with respect to the first polarizing filter.

[0131] In this example and the second modified example, each window section is provided with a first optical isolator having the same configuration, but it is also possible to arrange first optical isolators having different configurations in each window section.

[0132] However, considering the amount of light passing through, it is preferable that the optical isolators (first and second optical isolators) placed before and after the bandpass filter be configured as follows: That is, the fast axes of the quarter-wave plates before and after the bandpass filter are configured to have different angles. More preferably, the fast axes of the quarter-wave plates before and after the bandpass filter are configured to be orthogonal to each other.

[0133] It is difficult to create a perfect quarter-wave plate for all wavelengths. As a result, light becomes elliptically polarized as it passes through the first quarter-wave plate and then the second quarter-wave plate. When this state passes through a polarizing filter, the amount of light decreases. This phenomenon is maximized when the fast axes of the first and second quarter-wave plates are aligned. In other words, the amount of light decreases significantly.

[0134] For this reason, the fast axes of the quarter-wave plates before and after the bandpass filter are configured to have different angles, and more preferably, the fast axes of the quarter-wave plates before and after the bandpass filter are configured to be orthogonal to each other.

[0135] In the configuration of the above-described embodiment and the configuration of the first modified example, the fast axes of the quarter-wave plates before and after the bandpass filter are orthogonal to each other in all the window portions.

[0136] [Third embodiment] In the lens devices of the first and second embodiments, the polarization direction of light passing through each window is adjusted by a polarizing filter disposed behind the bandpass filter.

[0137] In this embodiment, a half-wave plate is further disposed behind the optical isolator disposed behind the band-pass filter to adjust the polarization direction of light passing through each window.

[0138] The configuration other than the filter unit is the same as that of the lens device of the first embodiment, so the following will only describe the configuration of the filter unit.

[0139] FIG. 16 is a diagram showing a schematic configuration of a filter unit.

[0140] As shown in the figure, the windows 122A, 122B, and 122C are provided with filter groups 140A, 140B, and 140C, respectively.

[0141] The filter group 140A provided in the first window 122A is made up of three filters, while the filter group 140B provided in the second window 122B is made up of four filters, and the filter group 140C provided in the third window 122C is also made up of four filters.

[0142] The filter group 140A provided in the first window portion 122A is composed of a band-pass filter 140A1, a quarter-wave plate 140A2, and a polarizing filter 140A3. The filters are arranged along the optical axis Z in the following order from the object side: band-pass filter 140A1, quarter-wave plate 140A2, polarizing filter 140A3. The quarter-wave plate 140A2 and polarizing filter 140A3 form an optical isolator 140A4.

[0143] The filter group 140B provided in the second window portion 122B is composed 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 in the following order from the object side: bandpass filter 140B1, quarter-wave plate 140B2, polarizing filter 140B3, and half-wave plate 140B5. The quarter-wave plate 140B2 and polarizing filter 140B3 form an optical isolator 140B4.

[0144] The filter group 140C provided in the third window portion 122C is composed 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 in the following order from the object side: bandpass filter 140C1, quarter-wave plate 140C2, polarizing filter 140C3, and half-wave plate 140C5. The quarter-wave plate 140C2 and polarizing filter 140C3 form an optical isolator 140C4.

[0145] FIG. 17 is a diagram showing an example of the configuration of a filter group provided in each window portion.

[0146] (1) First window 17, a bandpass filter having a first wavelength band λ1 is disposed in the first window as a bandpass filter (BPF). Also, a quarter-wave plate with a fast axis angle of 45° is disposed in the first window as a quarter-wave plate (QWP). Also, a polarizing filter with a transmission axis angle of 0° is disposed in the first window as a polarizing filter (PLF).

[0147] In the first window, the quarter-wave plate and the polarizing filter form an optical isolator. In this example, the quarter-wave plate is tilted 45° counterclockwise relative to the polarizing filter to form the optical isolator.

[0148] With the above settings, the first window portion transmits light in the first wavelength band λ1 that is linearly polarized light with an azimuth angle of 0°.

[0149] (2) Second window As shown in Fig. 17, a bandpass filter having a second wavelength band λ2 is disposed in the second window as a bandpass filter (BPF). Also, a quarter-wave plate with a fast axis angle of 45° is disposed in the second window as a quarter-wave plate (QWP). Also, a polarizing filter with a transmission axis angle of 0° is disposed in the second window as a polarizing filter (PLF). Also, a half-wave plate with a fast axis angle of 30° is disposed in the second window as a half-wave plate (HWP).

[0150] 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 constructed by placing the quarter-wave plate at a 45° counterclockwise angle relative to the polarizing filter. The configuration of this optical isolator is the same as that of the first window. Therefore, light with the same polarization direction as the first window passes through up to the half-wave plate. In the second window, the polarization direction is switched by passing the light through a half-wave plate. When the half-wave plate is tilted by an angle Φ relative to the polarizing filter, the existing polarization rotates by 2Φ. In this example, the fast axis of the half-wave plate is tilted by 30° relative to the transmission axis of the polarizing filter (0°). Therefore, in the second window, after passing through the half-wave plate, the light becomes linearly polarized light with an azimuth angle of 60° and is emitted from the window.

[0151] (3) Third window 17, a bandpass filter having a third wavelength band λ3 is disposed in the third window as a bandpass filter (BPF). Also, a quarter-wave plate with a fast axis angle of 45° is disposed in the third window as a quarter-wave plate (QWP). Also, a polarizing filter with a transmission axis angle of 0° is disposed in the third window as a polarizing filter (PLF). Also, a half-wave plate with a fast axis angle of 150° is disposed in the third window as a half-wave plate (HWP).

[0152] As with the first and second window sections, the third window section comprises an optical isolator consisting of a quarter-wave plate and a polarizing filter. In this example, the optical isolator is constructed by arranging the quarter-wave plate at an angle of 45° counterclockwise relative to the polarizing filter. The configuration of this optical isolator is the same as that of the first and second window sections. Therefore, light with the same polarization direction as the first and second window sections passes through up to the half-wave plate. As with the second window section, the third window section also switches the polarization direction by passing light through the half-wave plate. In the third window section, the fast axis of the half-wave plate is inclined by 150° with respect to the angle (0°) of the transmission axis of the polarizing filter. Therefore, 3 In the window, the light passes through the half-wave plate, becoming linearly polarized light with an azimuth angle of 120°, and is emitted from the window.

[0153] As described above, the filter unit of this embodiment allows light beams having different wavelength bands and polarization directions to pass through the respective window portions.

[0154] Furthermore, according to the filter unit of this embodiment, optical isolators having the same configuration can be used for each window portion.

[0155] In this embodiment, optical isolators with the same configuration are used for each window, but optical isolators with different configurations can also be used for each window, i.e., optical isolators with different angle settings for the quarter-wave plate and polarizing filter can also be used for each window.

[0156] Furthermore, in this embodiment, half-wave plates are arranged in all but the first window portion, but half-wave plates may be provided in all window portions.

[0157] [Variations] [Modification of the configuration of the filter group provided in each window] FIG. 18 is a diagram showing a modified example of the filter group provided in each window portion.

[0158] In this example, the setting of the quarter wave plate provided in each window portion is different from that of the filter unit in the above embodiment.

[0159] As shown in Fig. 18, each window is provided with a quarter-wave plate with a fast axis angle of 135°. That is, in this example, the quarter-wave plate is tilted 45° clockwise with respect to the polarizing filter. In this case, too, an optical isolator can be configured using the quarter-wave plate and polarizing filter, just like the filter unit in the above embodiment.

[0160] In this example, the first window also emits linearly polarized light in the first wavelength band λ1 with an azimuth angle of 0°. The second window also emits linearly polarized light in the second wavelength band λ2 with an azimuth angle of 60°. The third window also emits linearly polarized light in the third wavelength band λ3 with an azimuth angle of 120°.

[0161] [Example of filter group configuration when optical isolators are placed before and after bandpass filters] When optical isolators are placed before and after the bandpass filter, the polarization direction of the light passing through each window can be adjusted using a similar method.

[0162] FIG. 19 is a diagram showing an example of the configuration of a filter group provided in each window when optical isolators are placed before and after a bandpass filter.

[0163] When placing optical isolators before and after a bandpass filter, the rear optical isolator (second light A half-wave plate is placed behind the polarizing filter (second polarizing filter) that constitutes the rear optical isolator. More specifically, a half-wave plate is placed behind the polarizing filter (second polarizing filter) that constitutes the rear optical isolator. Note that the example shown in FIG. 19 shows a case where half-wave plates are placed only in the second window portion and the third window portion.

[0164] [First configuration example] FIG. 19(A) is a diagram showing a first configuration example of the filter group provided in each window portion.

[0165] As shown in the figure, a first optical isolator with the same configuration is disposed in each window, and a second optical isolator with the same configuration is disposed in each window.

[0166] In each window, the first optical isolator, which is placed in front of (on the object side of) the bandpass filter (BPF), 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°.

[0167] In addition, in each window section, the second optical isolator, which is placed behind (on the image side of) the bandpass filter (BPF), is composed of a second quarter-wave plate (second QWP) with a fast axis angle of 45° and a second polarizing filter (second PLF) with a transmission axis angle of 0°.

[0168] The second and third windows are further provided with half-wave plates (HWPs). The half-wave plates are disposed behind the second optical isolator. A half-wave plate with a fast axis angle of 30° is disposed in the second window. A half-wave plate with a fast axis angle of 150° is disposed in the third window.

[0169] In this example, the first window also emits linearly polarized light in the first wavelength band λ1 with an azimuth angle of 0°. The second window also emits linearly polarized light in the second wavelength band λ2 with an azimuth angle of 60°. The third window also emits linearly polarized light in the third wavelength band λ3 with an azimuth angle of 120°.

[0170] [Second configuration example] FIG. 19(B) is a diagram showing a second configuration example of the filter group provided in each window portion.

[0171] As shown in the figure, in this example, a first optical isolator and a second optical isolator with the same configuration are placed in each window. The difference from the first example configuration is the angle setting of the quarter-wave plate that makes up the optical isolator.

[0172] The first optical isolator 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°.

[0173] On the other hand, the second optical isolator is composed of a second quarter-wave plate (second QWP) with a fast axis angle of 45° and a second polarizing filter (second PLF) with a transmission axis angle of 0°.

[0174] In this example, the first window also emits linearly polarized light in the first wavelength band λ1 with an azimuth angle of 0°. The second window also emits linearly polarized light in the second wavelength band λ2 with an azimuth angle of 60°. The third window also emits linearly polarized light in the third wavelength band λ3 with an azimuth angle of 120°.

[0175] In both the first and second configuration examples, the fast axes of the quarter-wave plates before and after the bandpass filter are made orthogonal to each other, which prevents a decrease in the amount of light passing through each window.

[0176] In this example, optical isolators with different configurations can be used for each window, and half-wave plates can be provided for all windows.

[0177] [Fourth embodiment] By placing an optical isolator in front of the bandpass filter (on the object side), it is possible to prevent re-reflection of returning light from the front.

[0178] However, if an optical isolator is placed only in front of the bandpass filter, light converted into circularly polarized light is emitted from each window.

[0179] Therefore, when an optical isolator is placed in front of a bandpass filter, a polarizing filter is also placed behind the bandpass filter to adjust the polarization direction of light passing through each window.

[0180] The configuration other than the filter unit is the same as that of the lens device of the first embodiment, so the following will only describe the configuration of the filter unit.

[0181] FIG. 20 is a diagram showing a schematic configuration of a filter unit.

[0182] As shown in the figure, the window portions 122A, 122B, and 122C are provided with filter groups 150A, 150B, and 150C, respectively. Each of the filter groups 150A, 150B, and 150C provided in each of the window portions 122A, 122B, and 122C is composed of four filters. Specifically, the filter groups are composed of first polarizing filters 150A1, 150B1, and 150C1, quarter-wave plates 150A2, 150B2, and 150C2, band-pass filters 150A3, 150B3, and 150C3, and second polarizing filters 150A4, 150B4, and 150C4. The filters are arranged in the following order from the object side along the optical axis Z: first polarizing filters 150A1, 150B1, 150C1, quarter-wave plates 150A2, 150B2, 150C2, band-pass filters 150A3, 150B3, 150C3, and second polarizing filters 150A4, 150B4, 150C4. Optical isolators 150A5, 150B5, 150C5 are configured by the first polarizing filters 150A1, 150B1, 150C1 and the quarter-wave plates 150A2, 150B2, 150C2.

[0183] FIG. 21 is a diagram showing an example of the configuration of a filter group provided in each window portion.

[0184] (1) First window As shown in Fig. 21, a polarizing filter with a transmission axis angle of 0° is arranged in the first window as a first polarizing filter (first PLF). Also, a quarter-wave plate with a fast axis angle of 45° is arranged in the first window as a quarter-wave plate (QWP). Also, a band-pass filter of a first wavelength band λ1 is arranged in the first window as a band-pass filter (BPF). Also, a polarizing filter with a transmission axis angle of 0° is arranged in the first window as a second polarizing filter (second PLF).

[0185] In the first window, the first polarizing filter and the quarter-wave plate form an optical isolator. In this example, the optical isolator is formed by placing the quarter-wave plate at an angle of 45° counterclockwise relative to the polarizing filter.

[0186] (2) Second window As shown in Fig. 21, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter (first PLF) in the second window portion. Also, a quarter-wave plate with a fast axis angle of 45° is arranged as a quarter-wave plate (QWP) in the second window portion. Also, a band-pass filter of a first wavelength band λ1 is arranged as a band-pass filter (BPF) in the second window portion. Also, a polarizing filter with a transmission axis angle of 60° is arranged as a second polarizing filter (second PLF).

[0187] In the second window, the first polarizing filter and the quarter-wave plate form an optical isolator. In this example, the quarter-wave plate is tilted 45° counterclockwise relative to the polarizing filter to form the optical isolator.

[0188] (3) Third window As shown in Fig. 21, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter (first PLF) in the third window. Also, a quarter-wave plate with a fast axis angle of 45° is arranged as a quarter-wave plate (QWP) in the third window. Also, a band-pass filter of a first wavelength band λ1 is arranged as a band-pass filter (BPF) in the third window. Also, a polarizing filter with a transmission axis angle of 120° is arranged as a second polarizing filter (second PLF).

[0189] In the third window, the first polarizing filter and the quarter-wave plate form an optical isolator. In this example, the quarter-wave plate is tilted 45° counterclockwise relative to the polarizing filter to form the optical isolator.

[0190] As described above, in the filter unit of this embodiment, each window portion is provided with an optical isolator having the same configuration, and the polarization direction is essentially adjusted by the second polarizing filter.

[0191] According to the filter unit of this embodiment, the first window emits light in the first wavelength band λ1 that is linearly polarized at an azimuth angle of 0°. The second window emits light in the second wavelength band λ2 that is linearly polarized at an azimuth angle of 60°. The third window emits light in the third wavelength band λ3 that is linearly polarized at an azimuth angle of 120°.

[0192] [Variations] [Modification of the configuration of the filter group provided in each window] When an optical isolator is placed in front of the bandpass filter as described above, a polarizing filter is also placed behind the bandpass filter to adjust the polarization direction of the light passing through each window.

[0193] FIG. 22 is a diagram showing a modified example of the filter group provided in each window portion.

[0194] [First Modification] FIG. 22(A) shows a first modified example of a filter group arranged in each window portion.

[0195] The filter unit of this example also has an optical isolator with the same configuration in each window portion. The difference from the filter unit of the above embodiment is the angle setting of the quarter wave plate.

[0196] As shown in Figure 22(A), a quarter-wave plate with a fast axis angle of 135° is placed in each window. That is, in this example, the quarter-wave plate is tilted 45° clockwise with respect to the first polarizing filter. In this case, as with the filter unit of the above embodiment, an optical isolator can be configured using the quarter-wave plate and the first polarizing filter.

[0197] [Second Modification] FIG. 22(B) shows a second modified example of the filter group arranged in each window portion.

[0198] In the filter unit of this example, optical isolators with different configurations are provided in the respective window portions. Note that the configuration of the second polarizing filter is the same as that of the filter unit of the above embodiment.

[0199] As shown in Figure 22(B), a polarizing filter with a transmission axis angle of 0° is placed in the first window as a first polarizing filter (first PLF). Also, a quarter-wave plate with a fast axis angle of 45° is placed in the first window as a quarter-wave plate (QWP). In the first window, the quarter-wave plate is tilted 45° counterclockwise with respect to the first polarizing filter, thereby forming an optical isolator.

[0200] A polarizing filter with a transmission axis angle of 60° is placed in the second window as a first polarizing filter (first PLF). Also, a quarter-wave plate (QWP) with a fast axis angle of 15° is placed in the second window. In the second window, the quarter-wave plate is also placed at an angle of 45° counterclockwise with respect to the first polarizing filter, thereby forming an optical isolator.

[0201] A polarizing filter with a transmission axis angle of 120° is placed in the third window as a first polarizing filter (first PLF). Also, a quarter-wave plate with a fast axis angle of 75° is placed in the third window as a quarter-wave plate (QWP). In the third window, the quarter-wave plate is also placed at an angle of 45° counterclockwise with respect to the first polarizing filter, thereby forming an optical isolator.

[0202] [Third Modification] FIG. 22(C) shows a third modified example of the filter group arranged in each window portion.

[0203] The filter unit of this example also has optical isolators with different configurations provided in each window portion. The difference from the second modification is the angle setting of the quarter-wave plate.

[0204] As shown in Figure 22(C), a polarizing filter with a transmission axis angle of 0° is placed in the first window as a first polarizing filter (first PLF). Also, a quarter-wave plate with a fast axis angle of 135° is placed in the first window as a quarter-wave plate (QWP). In the first window, the quarter-wave plate is tilted 45° clockwise with respect to the first polarizing filter, thereby forming an optical isolator.

[0205] A polarizing filter with a transmission axis angle of 60° is placed in the second window as a first polarizing filter (first PLF). Also, a quarter-wave plate (QWP) with a fast axis angle of 105° is placed in the second window. In the second window, the quarter-wave plate is also placed at an angle of 45° clockwise with respect to the first polarizing filter, thereby forming an optical isolator.

[0206] A polarizing filter with a transmission axis angle of 120° is placed in the third window as a first polarizing filter (first PLF). Also, a quarter-wave plate with a fast axis angle of 165° is placed in the third window as a quarter-wave plate (QWP). In the third window, the quarter-wave plate is also placed at an angle of 45° clockwise with respect to the first polarizing filter, thereby forming an optical isolator.

[0207] [Other embodiments and modifications] [Number of windows] The filter unit has a number of windows set according to the number of wavelengths to be split. For example, if imaging is performed by splitting light into two wavelengths, at least two windows are provided. Also, if imaging is performed by splitting light into four wavelengths, at least four windows are provided.

[0208] 23 is a diagram showing an example of the configuration of a filter unit for capturing images by dispersing light into four wavelengths. Note that this figure shows an example in which optical isolators are placed before and after the bandpass filter.

[0209] As shown in the figure, filter frame 122 is provided with four windows 122A, 122B, 122C, and 122D. Window sections 122A to 122D are arranged at regular intervals on the same circumference with the center of filter frame 122 as the axis. That is, they are arranged at 90° intervals. Hereinafter, as necessary, window section 122A will be referred to as the first window section, window section 122B as the second window section, window section 122C as the third window section, and window section 122D as the fourth window section to distinguish between window sections 122A to 122D.

[0210] The windows 122A to 122D are provided with filter groups 160A to 160D, respectively. Each of the filter groups 160A to 160D is made up of five filters.

[0211] The five filters are composed of first polarizing filters 160A1 to 160D1, first quarter-wave plates 160A2 to 160D2, band-pass filters 160A3 to 160D3, second quarter-wave plates 160A4 to 160D4, and second polarizing filters 160A5 to 160D5. The five filters are arranged along the optical axis Z from the object side, with the first polarizing filters 160A1 to 160D1 and the band-pass filters 160A3 to 160D3 being the first polarizing filters. 1 , first quarter-wave plates 160A2 to 160D2, band-pass filters 160A3 to 160D3, second quarter-wave plates 160A4 to 160D4, and second polarizing filters 160A5 to 160D5 are arranged in this order.

[0212] In each of the windows 122A to 122D, first polarizing filters 160A1 to 160D1 and first quarter-wave plates 160A2 to 160D1 are provided. D2 The second quarter-wave plates 160A4 to 160D4 and the second polarizing filters 160A5 to 160D5 constitute first optical isolators 160A6 to 160D6 on the front side (object side) of the bandpass filters 160A3 to 160D3. The second quarter-wave plates 160A4 to 160D4 and the second polarizing filters 160A5 to 160D5 constitute second optical isolators 160A7 to 160D7 on the rear side (image side) of the bandpass filters 160A3 to 160D3.

[0213] To form an optical isolator, the first quarter-wave plates 160A2 to 160D2 are arranged at an angle of 45° relative to the first polarizing filters 160A1 to 160D1, and the second quarter-wave plates 160A4 to 160D4 are arranged at an angle of 45° relative to the second polarizing filters 160A5 to 160D5.

[0214] FIG. 24 is a diagram showing an example of the configuration of a filter group provided in each window portion.

[0215] (1) First window The first window transmits light in the first wavelength band λ1.

[0216] As shown in Fig. 24, a polarizing filter with a transmission axis angle of 0° is placed in the first window as a first polarizing filter. Also, a quarter-wave plate with a fast axis angle of 45° is placed in the first window as a first quarter-wave plate. This first polarizing filter and first quarter-wave plate form a first optical isolator. In this example, the optical isolator is formed by placing the first quarter-wave plate tilted 45° counterclockwise with respect to the first polarizing filter.

[0217] Furthermore, a bandpass filter of a first wavelength band λ1 is disposed in the first window portion.

[0218] Furthermore, a quarter-wave plate with a fast axis angle of 135° is disposed in the first window as a second quarter-wave plate. Furthermore, a polarizing filter with a transmission axis angle of 0° is disposed in the first window as a second polarizing filter. This second polarizing filter and the second quarter-wave plate form a second optical isolator. In this example, the optical isolator is formed by disposing the second quarter-wave plate at an angle of 45° clockwise with respect to the second polarizing filter.

[0219] With the above settings, the first window portion transmits light in the first wavelength band λ1 that is linearly polarized light with an azimuth angle of 0°.

[0220] (2) Second window The second window is a window that transmits light in the second wavelength band λ2.

[0221] 24, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter in the second window portion. Also, a quarter-wave plate with a fast axis angle of 45° is arranged as a first quarter-wave plate in the second window portion. That is, the second window portion is provided with a polarizing filter and a quarter-wave plate with the same configuration as the first window portion, in front of the bandpass filter.

[0222] In the second window portion, a bandpass filter of a second wavelength band λ2 is further disposed as a bandpass filter.

[0223] Furthermore, a quarter-wave plate with a fast axis angle of 15° is disposed in the second window as a second quarter-wave plate. Furthermore, a polarizing filter with a transmission axis angle of 60° is disposed in the second window as a second polarizing filter. This second polarizing filter and the second quarter-wave plate form a second optical isolator. In this example, the optical isolator is formed by disposing the second quarter-wave plate at a 45° clockwise angle with respect to the second polarizing filter.

[0224] With the above settings, the second window portion transmits light in the second wavelength band λ2 that is linearly polarized light with an azimuth angle of 60°.

[0225] (3) Third window The third window is a window that transmits light in the third wavelength band λ3.

[0226] 24, a polarizing filter with a transmission axis angle of 0° is disposed as a first polarizing filter in the third window. Also, a quarter-wave plate with a fast axis angle of 45° is disposed as a first quarter-wave plate in the third window. That is, a polarizing filter and a quarter-wave plate with the same configuration as those in the first window are provided in front of the bandpass filter in the second window.

[0227] In the third window portion, a bandpass filter of a third wavelength band λ3 is further disposed as a bandpass filter.

[0228] Furthermore, a quarter-wave plate with a fast axis angle of 75° is disposed in the third window as a second quarter-wave plate. Furthermore, a polarizing filter with a transmission axis angle of 120° is disposed in the third window as a second polarizing filter. This second polarizing filter and the second quarter-wave plate form a second optical isolator. In this example, the optical isolator is formed by disposing the second quarter-wave plate at a 45° clockwise angle with respect to the second polarizing filter.

[0229] With the above settings, the third window portion transmits light in the second wavelength band λ2 that is linearly polarized light with an azimuth angle of 120°.

[0230] (4) Fourth window The fourth window is a window that transmits light in the fourth wavelength band λ4.

[0231] 24, a polarizing filter with a transmission axis angle of 0° is arranged as a first polarizing filter in the fourth window. Also, a quarter-wave plate with a fast axis angle of 45° is arranged as a first quarter-wave plate in the fourth window. That is, a polarizing filter and a quarter-wave plate with the same configuration as those in the first window are provided in front of the bandpass filter in the second window.

[0232] In the fourth window portion, a bandpass filter of a fourth wavelength band λ4 is further disposed as a bandpass filter.

[0233] Furthermore, a quarter-wave plate with a fast axis angle of 45° is disposed in the fourth window portion as a second quarter-wave plate. Furthermore, a polarizing filter with a transmission axis angle of 90° is disposed in the fourth window portion as a second polarizing filter. This second polarizing filter and the second quarter-wave plate form a second optical isolator. In this example, the optical isolator is formed by disposing the second quarter-wave plate at an angle of 45° counterclockwise with respect to the second polarizing filter.

[0234] With the above settings, the fourth window portion transmits light in the fourth wavelength band λ4 that is linearly polarized light with an azimuth angle of 120°.

[0235] As described above, the four windows 122A to 122D provided in the filter unit 120 transmit light beams in different wavelength ranges and polarization directions.

[0236] [Window shape] In the above embodiment, the shape of the window portion (opening shape) is circular, but the shape of the window portion is not limited to this.

[0237] FIG. 25 is a diagram showing another example of the shape of the window portion provided in the filter frame.

[0238] The figure shows an example in which four windows 122A to 122D are provided. In this example, the disk-shaped filter frame 122 is divided into four equal parts in the circumferential direction to provide the windows 122A to 122D, each with a sector-shaped opening. The windows 122A to 122D are provided with sector-shaped filter groups 170A to 170D, respectively.

[0239] [Modifications of the lens device, filter unit, and filter group] It is preferable that the lens device be configured so that the filter unit can be attached to and detached from the lens barrel. This makes it possible to replace the filter unit. It is also preferable that the filter unit be configured so that the filter groups attached to each window can be replaced. This makes it possible to freely change the number and combination of wavelengths to be separated.

[0240] In a filter unit with a replaceable filter group, it is not necessary to use all of the windows. For example, if the filter frame has four windows, one window can be used in a light-shielded state to capture an image split into three wavelengths. This allows the image to be split into three wavelengths.

[0241] Furthermore, the filter group attached to each window portion may be configured by integrating (bonding) filters having each function, or may be configured by separating filters having each function. If the filters are integrated, it is possible to have a configuration in which there is no air gap between the filters. For example, the filters can be integrated by bonding them together using optical contact. If the filters are separated, it is possible to combine the filters in any desired manner.

[0242] When the filters having each function are configured separately, it is preferable that the filter unit be configured so that each filter can be attached individually to each window, thereby allowing any combination of filters to be attached to each window.

[0243] [Image sensor] A color polarization image sensor can also be used as the image sensor. For example, a color polarization image sensor is used when capturing an image separated into four wavelengths. A color polarization image sensor is a polarization image sensor in which a color filter is provided for each pixel. The color filters are arranged at predetermined positions in each pixel unit. For example, as shown in FIG. 8, if one pixel unit PU is composed of four pixels P1 to P4, a first color filter (e.g., a color filter that transmits light in the green wavelength range) is arranged in the first pixel P1, a second color filter (e.g., a color filter that transmits light in the red wavelength range) is arranged in the second pixel P2, a third color filter (e.g., a color filter that transmits light in the blue wavelength range) is arranged in the third pixel P3, and a fourth color filter (e.g., a color filter that transmits light in the infrared range) is arranged in the fourth pixel P4. In each pixel, the color filter is arranged, for example, between the microlens and the polarizer.

[0244] When a color polarization image sensor is used, the interference rate is calculated by further taking into account information on the spectral transmittance of the color filters provided in each pixel.

[0245] [Signal processing device] In the multispectral camera system of the above embodiment, the camera body and the signal processing device are configured as separate entities, but the functions of the signal processing device may be provided in the camera body. In this case, the camera body may be configured to have only the signal processing function.

[0246] The various functions of the signal processing device are realized by various processors. The various processors include a CPU and / or a GPU (Graphic Processing Unit), which are general-purpose processors that execute programs and function as various processing units, a programmable logic device (PLD), such as an FPGA (Field Programmable Gate Array), whose circuit configuration can be changed after manufacture, and a dedicated electrical circuit, such as an ASIC (Application Specific Integrated Circuit), which is a processor having a circuit configuration designed specifically to execute specific processing. The term "program" is synonymous with "software."

[0247] A single processing unit may be configured with one of these various processors, or may be configured with two or more processors of the same or different types. For example, a single processing unit may be configured with multiple FPGAs, or a combination of a CPU and an FPGA. Alternatively, multiple processing units may be configured with a single processor. Examples of multiple processing units configured with a single processor include, first, a configuration in which a single processor is configured with a combination of one or more CPUs and software, as typified by computers used as clients or servers, and this processor functions as multiple processing units. Second, a configuration in which a processor is used to realize the functions of an entire system including multiple processing units on a single IC (Integrated Circuit) chip, as typified by a system on chip (SoC). In this way, the various processing units are configured with one or more of the above-mentioned various processors as a hardware structure. [Explanation of symbols]

[0248] 1. Multispectral camera system 10 Multispectral Camera 100 Lens device 110A Lens Group (1st Lens Group) 110B lens group (second lens group) 120 Filter Unit 122 Filter Frame 122A Window (first window) 122B Window section (second window section) 122C Window section (third window section) 122D Window section (4th window section) 124A Filter group provided in the first window 124A1 Bandpass Filter 124A2 1 / 4 wave plate 124A3 Polarizing Filter 124A4 Optical Isolator 124B Filter group provided in second window portion 124B1 bandpass filter 124B2 1 / 4 wave plate 124B3 Polarizing Filter 124B4 Optical Isolator 124C Filter group provided in the third window 124C1 Bandpass Filter 124C2 1 / 4 wave plate 124C3 Polarizing Filter 124C4 Optical Isolator 130A Filter group provided 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 provided in second window portion 130B1 First polarizing filter 130B2 First quarter-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 provided in the third window section 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 provided in the first window 140A1 Bandpass Filter 140A2 1 / 4 wave plate 140A3 Polarizing Filter 140A4 Optical Isolator 140B Filter group provided in second window portion 140B1 Bandpass Filter 140B2 1 / 4 wave plate 140B3 Polarizing Filter 140B4 Optical isolator 140B5 1 / 2 wave plate 140C Filter group provided in the third window section 140C1 Bandpass Filter 140C2 1 / 4 wave plate 140C3 Polarizing Filter 140C4 Optical Isolator 140C5 1 / 2 wave plate 150A Filter group provided in the first window 150A1 First polarizing filter 150A2 1 / 4 wave plate 150A3 Bandpass Filter 150A4 Second polarizing filter 150A5 Optical Isolator 150B Filter group provided in second window portion 150B1 First polarizing filter 150B2 1 / 4 wave plate 150B3 bandpass filter 150B4 Second polarizing filter 150B5 Optical Isolator 150C Filter group provided in the third window 150C1 First polarizing filter 150C2 1 / 4 wave plate 150C3 bandpass filter 150C4 Second polarizing filter 150C5 Optical Isolator 160A Filter group provided in the first window 160A1 First polarizing filter 160A2 First quarter wave plate 160A3 Bandpass Filter 160A4 Second quarter wave plate 160A5 Second polarizing filter 160A6 First Optical Isolator 160A7 Second Optical Isolator 160B Filter group provided in second window portion 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 provided in the third window section 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 160C7 Second Optical Isolator 160D Filter group provided in the fourth window section 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 provided in the first window 170B Filter group provided in second window portion 170C Filter group provided in the third window section 170D Filter group provided in the fourth window section 200 camera body 210 Image sensor (polarized image sensor) 300 Signal Processing Device 311 CPU 312 ROM 313 RAM 314 Auxiliary storage 315 Input Device 316 Output Device 317 Input / Output Interface 320 Image data acquisition unit 330 Image Generation Unit 340 Output control section 350 Recording control section Arrow indicating the direction of the fast axis of the FAA quarter-wave plate Arrow indicating the direction of the fast axis of the FAB quarter-wave plate Arrow indicating the direction of the fast axis of the FAC quarter-wave plate L1 Return light Light reflected by the L2 bandpass filter L11 Return light Light reflected by the L12 bandpass filter L21 Return light Light reflected by the L22 bandpass filter Arrow indicating the direction of the slow axis of the LAA quarter-wave plate Arrow indicating the direction of the slow axis of the LAB quarter-wave plate Arrow indicating the direction of the slow axis of the LAC quarter-wave plate Arrow indicating the direction of the transmission axis of the LPA polarizing filter Arrow indicating the direction of the transmission axis of the LPB polarizing filter Arrow indicating the direction of the transmission axis of the LPC polarizing filter P1 pixel (first pixel) P2 pixel (second pixel) P3 pixel (third pixel) P4 pixel (4th pixel) PU Pixel Unit Z optical axis α1 Angle of the transmission axis of the first polarizer α2 Angle of the transmission axis of the second polarizer α3 Angle of the transmission axis of the third polarizer α4 Chapter 4 The angle of the transmission axis of the polarizer θA: Angle of the transmission axis of the polarizing filter provided in the first window portion (first angle) θB: Angle of the transmission axis of the polarizing filter provided in the second window portion (second angle) θC: Angle of the transmission axis of the polarizing filter provided in the third window (third angle)

Claims

1. A lens device having a filter unit in an optical path, 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 include a band-pass filter, and optical elements are provided on the object side and the image side of the band-pass filter, the optical element is composed of a polarizing filter and a quarter-wave plate disposed at an angle of 45° with respect to the transmission axis of the polarizing filter, and the angle of the fast axis differs between the object side and the image side of the band-pass filter; the first opening and the second opening transmit light having different wavelength ranges and polarization directions from each other; Lens device.

2. the fast axes of the wave plates on the object side and the image side of the bandpass filter are orthogonal to each other; The lens device according to claim 1 .

3. A lens device having a filter unit in an optical path, 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 include a band-pass filter, and an optical element is provided on at least one of an object side and an image side of the band-pass filter; the optical element is composed of a polarizing filter and a wave plate that converts linearly polarized light into circularly polarized light or elliptically polarized light, and is disposed on the image side of the bandpass filter, or on both the object side and the image side; at least one of the first opening and the second opening further includes a half-wave plate on the image side of the optical element that is arranged on the image side of the band-pass filter; the first opening and the second opening transmit light having different wavelength ranges and polarization directions from each other; Lens device.

4. the angles of the transmission axes of the polarization filters of the optical elements arranged on the image side of the band-pass filter are equal in the first opening and the second opening; The lens device according to claim 3 .

5. The filter unit is disposed at or near the pupil position. The lens device according to claim 1 .

6. The polarizing filter is an absorptive type. The lens device according to claim 1 .

7. A filter unit disposed in an optical path of the lens device, 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 optical elements are provided on the object side and the image side of the band-pass filter, the optical element is composed of a polarizing filter and a quarter-wave plate disposed at an angle of 45° with respect to the transmission axis of the polarizing filter, and the angle of the fast axis differs between the object side and the image side of the band-pass filter; the first opening and the second opening transmit light having different wavelength ranges and polarization directions from each other; Filter unit.

8. A filter unit disposed in an optical path of the lens device, 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 an optical element is provided on at least one of an object side and an image side of the band-pass filter; the optical element is composed of a polarizing filter and a wave plate that converts linearly polarized light into circularly polarized light or elliptically polarized light, and is disposed on the image side of the bandpass filter, or on both the object side and the image side; at least one of the first opening and the second opening further includes a half-wave plate on the image side of the optical element that is arranged on the image side of the band-pass filter; the first opening and the second opening transmit light having different wavelength ranges and polarization directions from each other; Filter unit.

9. A lens device according to any one of claims 1 to 6; a polarization image sensor that receives light that has passed through the lens device; An imaging device comprising:

Images