Multi-view optical system, optical apparatus, imaging apparatus, and moving body

A multi-view optical system includes an optical element. The optical element is configured to direct, in a predetermined direction, a first polarization component of a light beam coming from a first visual field, and a second polarization component, which is different from the first polarization component, of a light beam coming from a second visual field different from the first visual field.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2019-042723, filed Mar. 8, 2019, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a multi-view optical system, an optical apparatus, an imaging apparatus, and a moving body.

BACKGROUND

Conventionally, it is common practice to use what is called a fisheye lens to obtain a wide-field image.

DETAILED DESCRIPTION

According to one embodiment, a multi-view optical system includes an optical element. The optical element is configured to direct, in a predetermined direction, a first polarization component of a light beam coming from a first visual field, and a second polarization component, which is different from the first polarization component, of a light beam coming from a second visual field different from the first visual field.

An objective according to one embodiment is to provide the multi-view optical system, an optical apparatus, an imaging apparatus, and a moving body configured to obtain a wide-field image.

The drawings are schematic or conceptual, and a relationship between the thickness and width of each part, a ratio of sizes between parts, and the like are not necessarily the same as the actual ones. Further, even in a case of representing the same portion, dimensions and ratios may be different from one another depending on the drawings. In the description of the present application and the drawings, the same elements as those described previously with reference to drawings described previously are denoted by the same reference numerals, and the detailed description of such elements will be appropriately omitted.

First Embodiment

A configuration of a wide-field imaging system10according to a first embodiment will be described with reference toFIGS. 1 to 3B.

FIG. 1is a block diagram showing an example of the configuration of the wide-field imaging system10according to the present embodiment. As shown inFIG. 1, the wide-field imaging system10includes a wide-field imaging apparatus12and a display14. The wide-field imaging apparatus12includes an optical apparatus22, a processing circuit (image signal processing circuit)24, and a memory26. The processing circuit24includes an acquisition function32configured to acquire acquired data (image data) acquired by a polarization area sensor54described later, and a calculation function34configured to calculate a value obtained by performing predetermined operation on acquired data acquired using the acquisition function32. In the present embodiment, as an example, the processing circuit24controls the polarization area sensor54and also controls the display14.

The display14can display output data from the processing circuit24. Output of the processing circuit24includes, for example, an image based on acquired data (image data) acquired by the polarization area sensor54, an operation screen, and the like. The display14is, for example, a liquid crystal display or an organic EL display. The display14does not need to be provided. In this case, output of the processing circuit24is preferably recorded in a memory26, displayed on a display provided outside the wide-field imaging apparatus12, or recorded in a memory provided outside the wide-field imaging apparatus12.

An image output from the processing circuit24may be displayed on a display located at a position distant from the wide-field imaging apparatus12by communication by a communication function.

As shown inFIG. 2, the optical apparatus22according to the present embodiment includes a multi-view optical system (hereinafter, mainly referred to as a polarization separation optical system)42and a polarization camera44. The polarization camera44includes an imaging lens52configured to image a light beam coming from the polarization separation optical system42, and the polarization area sensor54configured to capture an image formed by the imaging lens52. The polarization area sensor54includes, for example, a photoelectric conversion circuit. In the present embodiment, as an example, the polarization separation optical system42, the imaging lens52, and the polarization area sensor54are coaxial.

The polarization separation optical system42is used to guide different polarization components from light from each visual field in a predetermined direction when light beams coming from a plurality of visual fields are incident. The imaging lens52is disposed in a predetermined direction with respect to the polarization separation optical system42, and is disposed at a position where a first polarization component and a second polarization component are directed from the polarization separation optical system42. The imaging lens52images the first polarization component and the second polarization component on the polarization area sensor54. The polarization area sensor54is configured to acquire the first polarization component and the second polarization component imaged through the imaging lens52at each pixel.

In the present embodiment, an example where the polarization separation optical system42is used to separate different polarization components from light beams coming from three visual fields V1, V2, V3, and guide them in a predetermined direction in which the imaging lens52and the polarization area sensor54are disposed.

In the present embodiment, the first visual field V1includes optical axes of the imaging lens52and the polarization area sensor54. The first visual field V1is in a front direction as viewed from the polarization camera44in the present embodiment. The second visual field V2is in a right side direction as viewed from the polarization camera44in the present embodiment. The third visual field V3is in a left side direction as viewed from the polarization camera44in the present embodiment.

The second visual field V2may be in the left side direction as viewed from the polarization camera44, and the third visual field V3may be in the right side direction as viewed from the polarization camera44. For this reason, the left and right of the polarization separation optical system42of the present embodiment may be switched.

The first visual field V1and the second visual field V2preferably partially overlap each other. The first visual field V1and the third visual field V3are preferably adjacent and continuous. The first visual field V1and the third visual field V3preferably partially overlap each other. The second visual field V2and the third visual field. V3preferably do not overlap. When the second visual field V2, the first visual field V1, and the third visual field V3are combined, a continuous viewing angle of a range over 180° is obtained.

The polarization separation optical system42extracts a linear polarization component (a first polarization component) of, for example, 0° from a first light beam coming from the first visual field V1including polarization components in all directions. When the first light beam coming from the first visual field V1is incident on the polarization separation optical system42, the polarization separation optical system42allows linearly polarized light of, for example, 0° from the first light beam coming from the first visual field V1to pass through, and cuts off transmission of the polarization components at other angles.

The polarization separation optical system42extracts a linear polarization component (a second polarization component different from the first polarization component) of, for example, 45° from a second light beam (including polarization components in all directions) coming from the second visual field V2adjacent to the first visual field V1. When the second light beam coming from the second visual field V2is incident on the polarization separation optical system42, the polarization separation optical system42allows linearly polarized light of, for example, 45° from the second light beam coming from the second visual field V2to pass through, and cuts off transmission of the polarization components at other angles.

The polarization separation optical system42includes an optical element configured to direct, in a predetermined direction, the first polarization component of the light beam coming from the first visual field V1and the second polarization component, which is different from the first polarization component, of the light beam coming from the second visual field V2different from the first visual field V1.

The polarization separation optical system42extracts a linear polarization component (a third polarization component different from the first polarization component and the second polarization component) of, for example, 90° from a third light beam (including polarization components in all directions) coming from the third visual field V3distant from the second visual field V2and adjacent to the first visual field V1. When the third light beam coming from the third visual field V3is incident on the polarization separation optical system42, the polarization separation optical system42allows linearly polarized light of, for example, 90° from the third light beam coming from the third visual field V3to pass through, and cuts off transmission of the polarization components at other angles.

The optical element of the polarization separation optical system42is configured to direct, in a predetermined direction, the third polarization component, which is different from the first polarization component and also different from the second polarization component, of the light beam coming from the third visual field V3different from the first visual field V1and the second visual field V2.

The polarization separation optical system42guides, in a predetermined direction, a 0° linear polarization component separated from the first light beam coming from the first visual field V1, a 45° linear polarization component separated from the second light beam coming from the second visual field V2, and a 90° linear polarization component separated from the third light beam coming from the third visual field V3. As described above, the polarization separation optical system42separates different polarization components from light beams coming from three of the visual fields V1, V2, V3, and guides them in a predetermined direction. The polarization separation optical system42guides each polarization component passing through the polarization separation optical system42to the common imaging lens52and polarization area sensor54. Different polarization components guided by the polarization separation optical system42are imaged on the polarization area sensor54through the imaging lens52.

The linearly polarized light of 45° separated from the second visual field V2is not actually along the linearly polarized light of 0° separated from the first visual field V1on the same plane. InFIG. 2, the linearly polarized light of 0° and linearly polarized light of 45° are drawn on the same plane for convenience.

In the present embodiment, as an example of the polarization area sensor54, one in which a total of four pixels, at which polarization component data of polarization angles 0°, 45°, 90°, and 135° can be acquired, are used as one set is used. In the present embodiment, the polarization area sensor54is configured to capture the polarization components of 0°, 45°, and 90° from three of the visual fields V1, V2, and V3passing through the polarization separation optical system42at the above-described set of pixels. Therefore, the polarization area sensor54can acquire captured image data for each polarization component in each set. The polarization area sensor54preferably includes an effective number of pixels, such as several million pixels. As the polarization area sensor54, IMX250MZR manufactured by SONY is used as an example.

As described above, the optical apparatus22can separate the first polarization component (0°) by the polarization separation optical system42from the first light beam coming from the first visual field V1, can image the component passing through the imaging lens52on the polarization area sensor54, and can acquire the first polarization component of a polarization angle at 0° by the polarization area sensor54. The optical apparatus22can separate the second polarization component (45°) by the polarization separation optical system42from the second light beam coming from the second visual field V2, can image the component passing through the imaging lens52on the polarization area sensor54, and can acquire the second polarization component of a polarization angle at 45° by the polarization area sensor54. The optical apparatus22can separate the third polarization component (90°) by the polarization separation optical system42from the third light beam coming from the third visual field V3, can image the component passing through the imaging lens52on the polarization area sensor54, and can acquire the third polarization component of a polarization angle at 90° by the polarization area sensor54. For this reason, The optical apparatus22can obtains data of images of the first polarization component, the second polarization component, and the third polarization component by the polarization area sensor54. As described above, according to the present embodiment, the multi-view optical system42and the optical apparatus22including the multi-view optical system42configured to obtain a wide-field image by a method completely different from one that uses a fisheye lens are provided.

One or a plurality of the processing circuits24of the wide-field imaging apparatus12are configured to obtain images of two or more visual fields by performing a predetermined operation on data of the first polarization component and the second polarization component acquired by the polarization area sensor54. The predetermined operation is, as an example, inverse matrix operation configured to calculate image data of an image in consideration of intensities of light from two or more visual fields based on intensity data of the first polarization component and the second polarization component acquired by the polarization area sensor54.

The processing circuit (controller)24of the wide-field imaging apparatus12is, for example, an integrated circuit, such as a central processing unit (CPU) or an application specific integrated circuit (ASIC). A general purpose computer may be used as the processing circuit24. The processing circuit24is not limited to one provided as a dedicated circuit, and may be provided as a program executed by a computer. In this case, the program is stored in a storage area in the integrated circuit, the memory26, or the like. The processing circuit24is connected to the polarization area sensor54and the memory26. The processing circuit24acquires acquired data in the polarization area sensor54by the acquisition function32and performs operation of multiplying with an appropriate coefficient or the like using the calculation function34based on the acquired data, so as to calculate the image data.

Here, the intensity of each polarization component acquired at four pixels as one set by the polarization area sensor54is I0, I45, I90, and I135for each polarization component. The acquisition function32of the processing circuit24acquires from the polarization area sensor54the intensities I0, I45, I90, and I135of each polarization component acquired by the polarization area sensor54in accordance with an acquisition signal for a still image and moving images described later. Here, the subscript represents an angle of polarization.

The processing circuit24is configured to acquire acquired data at the polarization area sensor54. The processing circuit24is configured to generate image data based on the acquired data for each polarization component acquired by the polarization area sensor54. The processing circuit24can output the image data for each polarization component acquired by the polarization area sensor54to the display14, and can display the image data on the display14(seeFIG. 6).

Let S1, S2, and S3be the intensities of the respective light beams for the respective visual fields V1, V2, and V3. These satisfy the following relationship:

is established. By performing inverse matrix operation,

is established. That is, the processing circuit24can respectively calculate image data S1, S2, and S3in consideration of the light intensities from the original visual fields V1, V2, and V3, based on signals (data I0, I45, and I90indicating the intensities of polarization components) acquired by the polarization area sensor54. Thereby, the wide-field imaging apparatus12can acquire the image data S1, S2, and S3of the respective visual fields V1, V2, and V3according to the light intensities of the respective visual fields V1, V2, and V3.

The memory26stores the above-described equation (2). The memory26stores, for example, an output (image data or the like) of the processing circuit24. The memory26may store the output (acquired data) of the polarization area sensor54. The memory26is, for example, a non-volatile memory, such as a flash memory. However, the memory26may be a storage apparatus, such as a hard disk drive (HDD), a solid state drive (SSD), an integrated circuit storage apparatus, or the like, and may further include a volatile memory.

Here, flowcharts in a case of capturing a still image and moving images using the wide-field imaging apparatus12will be briefly described with reference toFIGS. 3A and 3B. The processing circuit (one or a plurality of processors)24is connected to the polarization area sensor54in a wired or wireless manner. The polarization area sensor54is controlled by the processing circuit24.

The processing circuit24can perform processing below by using the calculation function34before displaying image data of each polarization component acquired from the polarization area sensor54on the display14. The processing circuit24may display an image based on data acquired by the polarization area sensor54on the display14directly. The processing circuit24may display an image based on image data calculated using the calculation function34on the display14.

In a case where the processing circuit24performs the processing below by using the calculation function34, the processing circuit24acquires the acquired data acquired by the polarization area sensor54by the acquisition function32, and executes operation of Equation (2) by the calculation function34. In the calculation function34, the processing circuit24performs predetermined operation based on the image data for each polarization component.

An example of capturing a still image will be described using the flowchart shown inFIG. 3A. For example, when a switch provided on the camera44or a wireless switch is operated by the user and a still image acquisition start signal configured to capture a still image is input to the processing circuit24of the wide-field imaging apparatus12, the processing circuit24acquires acquired data (image data) from the polarization area sensor54by using the acquisition function32of the processing circuit24(ST1). Here, the processing circuit24acquires, from the polarization area sensor54, the intensities I0, I45, I90, and Ins of not only polarization components of 0°, 45°, and 90°, but also of a polarization component of 135°. In the present embodiment, since the polarization component of 135° is not extracted through the polarization separation optical system42, the polarization area sensor54acquires reference example data.

The processing circuit24calculates the image data S1, S2, and S3according to the intensities of light beams coming from the visual field V1, V2, and V3from Equation (2) stored in the memory26by using the calculation function34based on the data of the intensities I0, I45, and I90of the polarization components acquired from the polarization area sensor54using the acquisition function32. The processing circuit24generates an image based on the image data S1, S2, and S3according to the calculated intensities of the respective light beams coming from the respective visual fields V1, V2, and V3(ST2). Details will be described, for example, in the second embodiment. The inverse matrix operation of Equation (2) described above merely multiplies the data of the intensities I0, I45, and I90of the polarization components by a coefficient, and does not perform complicated processing. For this reason, processing time of the processing circuit24using the calculation function34may also be short.

Then, the processing circuit24sends image data generated based on the image data S1, S2, and S3corresponding to the intensities of light beams coming from the respective visual fields V1, V2, and V3calculated using the calculation function34to the display14, and causes the generated image to be displayed on the display14(ST3). In a case where the generated image data is sent to the display14, data that is compressed by an appropriate compression technique is preferably transmitted to the display14. Preferably, the image data displayed on the display14is stored in the memory26.

In a case where, in addition to capturing of a single still image, for example, what is called continuous shooting, in which a plurality of times of shooting is performed per second, is performed, a series of pieces of processing of ST1, ST2, and ST3described above are repeated at an appropriate speed.

In the present embodiment, the polarization area sensor54acquires image data of the visual fields V1, V2, and V3simultaneously. For this reason, special synchronization adjustment is not necessary even if the camera44is used to capture an image of three of the visual fields V1, V2, and V3at high speed, for example, more than 100 frames per second.

In the present embodiment, the polarization separation optical system42separates the polarization components from the light beams coming from the visual fields V1, V2, and V3, and the polarization area sensor54separates the image based on each of the polarization components, so as to obtain images of the visual fields V1, V2, and V3. By using, for example, a color RGB area sensor as the polarization area sensor54, color information of all the visual fields V1, V2, and V3can be obtained without loss.

Next, an example of capturing moving images will be described using the flowchart shown inFIG. 3B. For example, when the switch provided on the camera44or the wireless switch is operated by the user, and a moving image acquisition start signal configured to capture moving images is input to the processing circuit24of the wide-field imaging apparatus12, the processing circuit24performs the processing of ST1, ST2, and ST3described above. In a case where an image is generated, data may be compressed using an appropriate compression technique and transmitted to the display14, so as to be displayed on the display14. Moving images are obtained as such work is performed repeatedly at appropriate time intervals. The processing circuit24repeats the above-described flow until a signal for ending capturing of moving images is input to the processing circuit24(ST4). The moving image data displayed on the display14is preferably stored in the memory26.

In addition to being stored in the memory26, a still image and moving images are also preferably stored in a storage apparatus, such as an appropriate storage, via a network.

According to the present embodiment, the wide-field imaging apparatus12can obtain a wide-field image by a method completely different from one that uses a fisheye lens is provided.

By separating polarization components into an appropriate number (the number of visual fields) using the polarization separation optical system42according to the present embodiment, the camera44capable of capturing polarization components can capture images from light beams coming from a plurality of directions in a wide angle. Then, in this case, by using the wide-field imaging apparatus12, a desired image can be obtained in a short time by calculation of a simple equation (Equation (2)).

The processing circuit24may be provided outside the wide-field imaging apparatus12. The processing of the processing circuit24may be executed by a predetermined server. Acquired data of the polarization area sensor54is preferably output to the outside of the wide-field imaging apparatus12or recorded in the memory26. That is, output and calculation of the acquired data of the polarization area sensor54may be performed inside the wide-field imaging apparatus12or may be performed outside.

In the optical apparatus, the polarization separation optical system42does not require electric energy. Therefore, operation time of the polarization camera44can be made as long as possible.

Here, the polarization separation optical system42separates a linear polarization component of 0° from the first visual field V1, a linear polarization component of 45° from the second visual field V2, and a polarization component of 90° from the third visual field V3, and guides them to the imaging lens52. A combination of the polarization components and the visual fields V1, V2, and V3is not limited to the above. For example, the polarization separation optical system42may separate the polarization component of 90° from the second visual field V2and separate the polarization component of 45° from the third visual field V3.

The polarization area sensor54according to the present embodiment can acquire linearly polarized light at 135°, in addition to that at 0°, 45°, and 90°. For this reason, images of four visual fields V1, V2, V3, and V4can be obtained by separating the images from the four visual fields V1, V2, V3, and V4into four different linear polarization components (0°, 45°, 90°, and 135°) using the polarization separation optical system42. If the polarization area sensor54is further formed so as to be able to acquire polarization components of different angles, it is possible to obtain images of more visual fields.

The optical apparatus22according to the present embodiment can be attached to appropriate moving bodies82,84, and86(seeFIGS. 4A to 4C) and used. According to the present embodiment, the moving bodies82,84, and86including the wide-field imaging apparatus12configured to obtain a wide-field image by a method completely different from one that uses a fisheye lens are provided. Hereinafter, an example, in which an automobile is used as a moving body as a first application (seeFIG. 4A), a ship is used as a moving body as a second application (seeFIG. 4B), and a flying object, such as an airplane, is used as a moving body as a third application (seeFIG. 4C), will be described. The moving bodies82,84, and86of the first to third applications are configured to be stoppable and movable.

As shown inFIG. 4A, the moving body82includes a body82aand the wide-field imaging apparatus12or the optical apparatus22. The wide-field imaging apparatus12or the optical apparatus22is used by being attached to the body82aof the moving body82, such as an automobile. In this case, the optical apparatus22shown inFIG. 2is fixed to a top surface (upper surface)82bof the roof of the body82aas an example.

A front direction, a rear direction, a right side direction, and a left side direction may be defined for the body82aof the moving body82. In this case, an image can be obtained by the camera44from predetermined polarization components in the front direction of the moving body82in the first visual field V1, in the right side direction of the moving body82in the second visual field V2, and in the left side direction of the moving body82in the third visual field V3.

The optical apparatus22may be disposed on a front bumper83aor a rear bumper83bof the body82aof the moving body82. The optical apparatus22may also be disposed in the vehicle (in the body82a) such that the first light beam from the outside through a windshield and the first light beam from the outside through a rear glass are obtained as the first visual field V1.

In a case where the optical apparatus22is attached to, for example, the front bumper83aof the body82aof the moving body82, the optical apparatus22is used to detect a person, an automobile, and the like heading for the moving body82from the right and left directions. In this case, as described in the first embodiment, an image from the first visual field V1facing the camera44may be observed, which may be unnecessary. In this case, the visual fields V2and V3do not have to be continuous. That is, the polarization separation optical system42of the optical apparatus22does not necessarily have to separate three polarization components, and may be configured to separate two polarization components different from each other. In a case where the polarization separation optical system42separates two polarization components different from each other, a linear polarization component of 0° and a linear polarization component of 90° are preferably used as the polarization components.

Therefore, the multi-view optical system (polarization separation optical system) according to the first embodiment preferably includes the optical element configured to direct, in a predetermined direction, the first polarization component of the light beam coming from the first visual field V1and the second polarization component, which is different from the first polarization component, of the light beam coming from the second visual field V2different from the first visual field V1. The above similarly applies to second to fifth embodiments described later.

As shown inFIG. 4B, the moving body84includes a body84aand the wide-field imaging apparatus12or the optical apparatus22. The wide-field imaging apparatus12or the optical apparatus22is used by being attached to the body84aof the moving body84moving on the sea, such as a ship. The optical apparatus22can be attached to the bow, stern, or any other suitable positions of the body84aof the moving body84and used. The wide-field imaging apparatus12or the optical apparatus22may be used for a submarine (moving body) capable of moving in the sea or the like, in addition to a ship moving on the sea.

As shown inFIG. 4C, the moving body86includes the body86aand the wide-field imaging apparatus12or the optical apparatus22. As shown inFIG. 4C, the wide-field imaging apparatus12or the optical apparatus22is used by being attached to the body86aof a moving body86such as an aircraft (including a drone such as a drone). The optical apparatus22can be attached to, for example, the nose, cockpit, or any other suitable positions of an aircraft. The moving body86here also includes a spacecraft.

Second Embodiment

Next, the second embodiment will be described by usingFIGS. 5 and 6. The present embodiment is a modification of the first embodiment, and the same members, or members having the same functions, as the members described in the first embodiment are denoted by the same reference numerals as much as possible, and the detailed description of such members is omitted. The above similarly applies to the third to fifth embodiments described later.

The wide-field imaging apparatus12or the optical apparatus22according to the present embodiment can be appropriately used in the above-described first to third applications. The above similarly applies to the third to fifth embodiments described later.

Here, the polarization separation optical system42of the optical apparatus22, which is a portion different from the optical apparatus22described in the first embodiment, will be mainly described. The optical apparatus22of the present embodiment is used for the wide-field imaging apparatus12and the wide-field imaging system10ofFIG. 1like the one described in the first embodiment.

As shown inFIG. 5, the optical apparatus22according to the present embodiment includes the polarization separation optical system42including an optical element, the imaging lens52, and the polarization area sensor54.

Here, as explained in the first embodiment, the front side of the imaging lens52of the optical apparatus22is taken as the first visual field V1, the right side of the imaging lens52is taken as the second visual field V2, and the left side of the imaging lens52is taken as the third visual field V3. The first visual field V1and the second visual field V2are preferably adjacent and continuous. The first visual field V1and the second visual field V2preferably partially overlap each other. The first visual field V1and the third visual field V3are preferably adjacent and continuous. The first visual field V1and the third visual field V3preferably partially overlap each other. The second visual field V2and the third visual field V3preferably do not overlap. When the second visual field V2, the first visual field V1, and the third visual field V3are combined, a continuous viewing angle of a range over 180° is obtained.

The polarization separation optical system42includes a polarization beam splitter (PBS) cube122, a non-polarization beam splitter (NPBS) cube124, and a linear polarization plate (polarizer)126as optical elements. The PBS cube122is a polarization optical element. The PBS cube122and the NPBS cube124are in front of the imaging lens52. The PBS cube122is more distal to the imaging lens52than the NPBS cube124. The linear polarization plate126may be in front of the imaging lens52or may be at a position offset from the front.

If the imaging lens52and the polarization area sensor54each have a plane, a transmitting/reflecting surface122aof the PBS cube122is inclined at an angle of +(plus) 45° with respect to the plane. The PBS cube122transmits linearly polarized light of 0° (P-polarized light) of the first light beams coming from the first visual field V1at an appropriate transmittance b. The PBS cube122reflects linearly polarized light of 90° (S-polarized light) of the third light beams coming from the third visual field V3at an appropriate reflectance c.

If the imaging lens52and the polarization area sensor54each have a plane, a transmitting/reflecting surface124aof the NPBS cube124is inclined at an angle of −(minus) 45° with respect to the plane. The NPBS cube124transmits linearly polarized light of 0° passing through the PBS cube122at an appropriate transmittance a1among the first light beams coming from the first visual field V1, and linearly polarized light of 90° passing through the PBS cube122at the appropriate transmittance a1among the third light beams coming from the third visual field V3.

The transmitting/reflecting surface122aof the PBS cube122and the transmitting/reflecting surface124aof the NPBS cube124are in a relationship of about 90° with each other.

The linear polarization plate126transmits linearly polarized light of 45° among the second light beams coming from the second visual field V2at an appropriate transmittance d. The transmitting/reflecting surface124aof the NPBS cube124reflects linearly polarized light of 45° that has passed through the linear polarization plate126among the second light beams coming from the second visual field V2at an appropriate reflectance a2. The linear polarization plate126is one or a plurality of linear polarization elements that extract a linear polarization component in a specific direction from light passing through the linear polarization plate (polarization optical element)126.

The linear polarization plate126is disposed to be inclined with respect to the NPBS cube124so that linearly polarized light of 45° passes.

The PBS cube122transmits part of linearly polarized light of 0° from the first beam coming from the first visual field V1. The PBS cube122reflects part of linearly polarized light of 90° from the third beam coming from the third visual field V3. The NPBS cube124is disposed at the point where the linearly polarized light of 0° is transmitted and the point where the linearly polarized light of 90° is reflected.

The NPBS cube124transmits linearly polarized light of 0° and linearly polarized light of 90° and directs them toward the imaging lens52.

Here, the linear polarization plate126transmits linearly polarized light of 45° from the second light beam coming from the second visual field V2. The NPBS cube124is disposed at the point where the linearly polarized light is transmitted by the linear polarization plate126. The NPBS cube124reflects part of the linearly polarized light of 45° and directs it toward the imaging lens52.

As described above, the optical apparatus22can separate the first polarization component (0°) by the polarization separation optical system42from the first light beam coming from the first visual field V1, can image the component passing through the imaging lens52on the polarization area sensor54, and can acquire a polarization component of a polarization angle at 0° by the polarization area sensor54. The optical apparatus22can separate the second polarization component (45°) by the polarization separation optical system42from the second light beam coming from the second visual field V2, can image the component passing through the imaging lens52on the polarization area sensor54, and can acquire a polarization component of a polarization angle at 45° by the polarization area sensor54. The optical apparatus22can separate the third polarization component (90°) by the polarization separation optical system42from the third light beam coming from the third visual field V3, can image the component passing through the imaging lens52on the polarization area sensor54, and can acquire a polarization component of a polarization angle at 90° by the polarization area sensor54.

The intensities I0, I45, I90, and Ins of polarization components acquired at a set of four pixels of the polarization area sensor54, and the image data S1, S2, and S3considering the intensity of each light beam for the visual fields V1, V2, and V3satisfy the following relationship: That is,

is established. In the equation, a1: transmittance of the NPBS cube124, a2: reflectance of the NPBS cube124, b: transmittance of P-polarized light of the PBS cube122, c: reflectance of S-polarized light of the PBS cube122, and d: transmittance of the linear polarization plate126. By performing inverse matrix operation,

is established. That is, the processing circuit24can calculate the image data S1, S2, and S3considering the light intensities corresponding to the original visual fields V1, V2, and V3from the signals (intensity data of polarization components) I0, I45, and I90that can be acquired by the polarization area sensor54. Thereby, the wide-field imaging apparatus12can acquire images of the visual fields V1, V2, and V3according to the light intensities of the respective visual fields V1, V2, and V3.

In the present embodiment, Equation (4) can be further modified to

As can be seen from Equation (5), the right side does not depend on the performance of the polarizing elements (the PBS cube122, the NPBS cube124, and the linear polarizing plate126). That is, the right side does not depend on the above-described a1, a2, b, c, and d. Meanwhile, the overall brightness of the visual fields V1, V2, and V3depends on the intensities I0, I45, and I90of polarization components acquired by the polarization area sensor54. From the above, the image data obtained from the light of the visual field V1, V2, and V3captured by the polarization area sensor54is separated by the polarization separation optical system42regardless of the performance of the optical elements (the PBS cube122, the NPBS cube124, and the linear polarization plate126). For this reason, the performance of the polarization separation optical system42does not depend on aging degradation of the optical elements (the NPBS cube124, the PBS cube122, and the linear polarization plate126).

In the present embodiment, the memory26stores Equation (4) in place of Equation (2) described above. The flow in a case of capturing a still image and moving images is similar to that described with reference toFIGS. 3A and 3B.

In a case where the processing circuit24performs processing below by using the calculation function34, the processing circuit24acquires an output from the polarization area sensor54by the acquisition function32, and executes operation described later by the calculation function34. In the calculation function34, the processing circuit24performs predetermined operation (as an example, the inverse matrix operation described above) based on the image data for each polarization component.

By using the polarization separation optical system42according to the present embodiment, it is possible to obtain an image from light beams coming from a plurality of directions in a wide angle by the camera44configured to capture a polarization component. In this case, by using the wide-field imaging apparatus12, an image of the image data S1, S2, and S3of a desired intensity in the visual fields V1, V2, and V3can be obtained in a short time by calculation of a simple equation (Equation (4)).

The wide-field imaging apparatus12can calculate the image data S1, S2, and S3in consideration of the light intensities corresponding to the original visual fields V1, V2, and V3from the intensity data I0, I45, and I90of polarization components configured to be acquired by the polarization area sensor54. Thereby, the wide-field imaging apparatus12can acquire images of the visual fields V1, V2, and V3according to the light intensities of the respective visual fields V1, V2, and V3.

An image captured by the polarization area sensor54according to the present embodiment is shown on the left side (left diagram) inFIG. 6, and an image reconstructed by using the image captured by the polarization area sensor54is shown on the right side (right diagram) inFIG. 6.

The left diagram inFIG. 6show captured images of the polarization area sensor54for polarization angles of 0°, 45°, and 90° arranged in this order from the top. An example of the polarization angle of 0° is an image in the direction of the first visual field V1on which the acquired data acquired by the polarization area sensor54is displayed. An example of the polarization angle of 45° is an image in the direction of the second visual field V2in which the acquired data acquired by the polarization area sensor54is displayed. An example of the polarization angle of 90° is an image in the direction of the third visual field V3on which the acquired data acquired by the polarization area sensor54is displayed. It shows that, the image, particularly for the polarization angle of 45′, in the left diagram inFIG. 6is displayed in a manner that the polarization component of the polarization angle of 0° and the polarization component of the polarization angle of 90° overlap each other.

The right diagram inFIG. 6is an image (referred to as a reconstructed image) showing the intensity data S1, S2, and S3of light beams for the respective visual fields V1, V2, and V3obtained by converting the acquired data acquired by the polarization area sensor54by using Equation (4). The right diagram inFIG. 6show reconstructed images for polarization angles of 0°, 45°, and 90° arranged in this order from the top. It shows that, in the reconstructed image, particularly for the polarization angle of 45°, in the right diagram inFIG. 6, the polarization component of the polarization angle of 0° and the polarization component of the polarization angle of 90° are removed.

In the present embodiment, a positional relationship between the optical elements (the NPBS cube124, the PBS cube122, and the linear polarization plate126) of the polarization separation optical system42can be reliably maintained with high accuracy. That is, the polarization separation optical system42according to the present embodiment can be formed into a more robust configuration.

Third Embodiment

Next, the third embodiment will be described with reference toFIG. 7. Here, the optical apparatus22, which is a portion different from that described in the first and second embodiments, will be mainly described. The optical apparatus22of the present embodiment is used for the system10ofFIG. 1in a similar manner as that described in the first and second embodiments.

As shown inFIG. 7, the optical apparatus22according to the present embodiment includes the polarization separation optical system42and the polarization camera44.

In the second embodiment, the example in which the polarization separation optical system42includes the PBS cube122and the NPBS cube124is described. In the present embodiment, as shown inFIG. 7, the polarization separation optical system42may use a plate-shaped polarization beam splitter (PBS)132instead of using the cube-shaped PBS cube122. Instead of using the cube-shaped NPBS cube124, the polarization separation optical system42may use a plate-shaped non-polarization beam splitter (NPBS)134. The PBS132and the NPBS134can preferably maintain an angle with respect to the imaging lens52and the polarization area sensor54.

Fourth Embodiment

Next, the fourth embodiment will be described with reference toFIG. 8. Here, the optical apparatus22, which is a portion different from that described in the first to third embodiments, will be mainly described. The optical apparatus22of the present embodiment is used for the system10ofFIG. 1in a similar manner as that described in the first to third embodiments.

As shown inFIG. 8, the optical apparatus22according to the present embodiment includes the polarization separation optical system42and the polarization camera44.

The polarization separation optical system42acquires one polarization component from each of different viewing angles and guides it to the imaging lens52. The polarization separation optical system42acquires, for example, a linear polarization component of 0° from the first visual field V1, a linear polarization component of 45° from the second visual field V2, and a polarization component of 90° from the third visual field V3, and guides them to the imaging lens52. However, the combination of the polarization components and the visual fields is not limited to the above. The polarization components corresponding to the visual fields are different from each other. InFIG. 8, linearly polarized light of 45° is not actually along the same plane as linearly polarized light of 0°. However, they are drawn on the same plane for convenience.

The description has been made on the example, in which the polarization separation optical system42according to the second embodiment includes the PBS cube122and the NPBS cube124as optical elements, and the polarization separation optical system42according to the third embodiment includes the PBS132and the NPBS134as optical elements, which are arranged along the optical axis of the first visual field V1. In the polarization separation optical system42according to the present embodiment, two half mirrors (or NPBS cubes)142and144as optical elements are juxtaposed perpendicularly to the optical axis of the first visual field V1.

The polarization separation optical system42includes, as optical elements, two of the half mirrors (or NPBS cubes)142and144and three linear polarization plates (linear polarizers)152,154, and156. The three linear polarization plates (linear polarizers)152,154, and156of the polarization separation optical system42extract linear polarization components in a specific direction from light passing through the polarization optical element.

The first linear polarization plate152extracts a linear polarization component (first polarization component) of, for example, 0° from the first light beam coming from the first visual field V1. The first polarization component that has passed through the first linear polarization plate152is incident on two of the half mirrors142and144.

The second linear polarization plate154extracts a linear polarization component (second polarization component) of, for example, 45° from a second light beam coming from the second visual field V2. The second polarization component that has passed through the second linear polarization plate154is incident on the half mirror142.

The third linear polarization plate156extracts a linear polarization component (third polarization component) of, for example, 90° from a third light beam coming from the third visual field V3. The third polarization component that has passed through the third linear polarization plate156is incident on the half mirror144.

The first half mirror142and the second half mirror144reflect part of the first polarization component of 0° and transmit the rest. Therefore, the first linearly polarized light of 0° that has passed through the first half mirror142and the second half mirror144is imaged by the imaging lens52and captured by the polarization area sensor54.

The first half mirror142reflects part of the second polarization component of 45° that has passed through the second linear polarization plate154toward the imaging lens52and transmits the rest. The second half mirror144reflects part of the third polarization component of 90° that has passed through the third linear polarization plate156toward the imaging lens52and transmits the rest. The second linearly polarized light 45° reflected by the first half mirror142is imaged by the imaging lens52and captured by the polarization area sensor54. The third linearly polarized light of 90° reflected by the second half mirror144is imaged by the imaging lens52and captured by the polarization area sensor54.

For this reason, the polarization separation optical system42according to the present embodiment can separate polarization components into an appropriate number (the number of visual fields).

As described in the first to third embodiments, the optical apparatus22can simultaneously acquire images of three of the visual fields V1, V2, and V3.

Fifth Embodiment

Next, the fifth embodiment will be described with reference toFIG. 9. Here, the optical apparatus22, which is a portion different from that described in the first to fourth embodiments, will be mainly described. The optical apparatus22of the present embodiment is used for the system10ofFIG. 1in a similar manner as that described in the first and fourth embodiments.

As shown inFIG. 9, the optical apparatus22according to the present embodiment includes the polarization separation optical system42and the polarization camera44.

The polarization separation optical system42separates one polarization component from polarization components in all directions of different viewing angles and guides the polarization component to the imaging lens52. For example, the linear polarization component of 0° is separated for the first visual field and the linear polarization component of 90° is separated for the second visual field, and guided to the imaging lens52. However, the combination of the polarization components and the visual fields is not limited to the above. The polarization components corresponding to the visual fields are different from each other.

The polarization separation optical system42includes a polarization beam splitter (PBS) block162. Here, the PBS block162of the polarization separation optical system42is formed in a conical or truncated cone shape. The PBS block162includes a bottom surface164on which light beams coming from the first visual field V1are incident and a side surface166on which light beams coming from the second visual field V2are incident. The side surface166of the polarization beam splitter (PBS) block162is curved. That is, the polarization separation optical system42includes a curved polarization beam splitter as an optical element.

Here, the content of the second visual field V2is different from that in the first embodiment to the fourth embodiment. The second visual field V2in the first to fourth embodiments is for capturing, by the polarization separation optical system42, a light beam incident on a plane orthogonal to the first visual field V1. For the second visual field V2in the present embodiment, a light beam coming from an annular region is captured annularly by the polarization separation optical system42.

The second visual field V2reflects part of the polarization component of 90° of the light beams coming from 360° of the side of the PBS block162toward the imaging lens52.

For this reason, the polarization separation optical system42can separate the first polarization component of 0° and the second polarization component of 90° and direct them to the imaging lens52.

With the above configuration, the polarization separation optical system42according to the present embodiment can guide the polarization component of 90° separated from the light beam coming from all directions or the visual field V2which is close to all directions to the polarization area sensor54.

The polarization separation optical system42of the present embodiment can capture a wide viewing angle with a small number of optical elements.

According to the first to fifth embodiments, the multi-view optical system42, the optical apparatus22, the imaging apparatus12, and the moving body82configured to obtain a wide-field image is provided.