JP7737293B2 - Imaging device and imaging method - Google Patents

Description

The present invention relates to an imaging device and an imaging method, and in particular to an imaging device and an imaging method for incoherent digital holography.

Incoherent digital holography is being investigated as a method for acquiring three-dimensional information without using special lighting such as lasers. Incoherent object light from a subject is split into two optical paths, and a concave mirror or lens is placed in one of the optical paths to create a slight optical path difference. These lights are then combined and interfered with, capturing the subject as interference fringes. By acquiring and calculating multiple interference fringe images (holograms) with different phases, complex amplitude information of the subject on the image sensor surface can be obtained. By performing backpropagation calculations of light from this complex amplitude information, a two-dimensional image of any depth distance, i.e., three-dimensional image information, can be obtained.

Capturing moving images containing three-dimensional information requires acquiring complex amplitude information about the subject for each frame, which in turn requires simultaneously acquiring interference fringes of different phases. One proposed method for this is to use polarized light to simultaneously generate and acquire interference fringe images of different phases (Patent Document 1, Non-Patent Document 1).

Figures 7 and 8 show examples of conventional incoherent digital holography imaging devices. The imaging device in Figure 7 is composed of an optical system using a birefringent lens. Object light from subject 1 passes through lens 2 and wavelength filter 3, and polarizer 4 filters out only linearly polarized components in a given direction. Birefringent lens 5 is provided with different focal lengths for polarization directions ±45° from this polarization direction. The object light passing through birefringent lens 5 is converted into right-handed and left-handed circularly polarized light by quarter-wave plate 6. This light is captured by polarization camera 20, in which polarizers are provided at 45° intervals for each pixel, and images for each polarization direction (images constructed by aggregating pixel data for each polarization direction) are generated, allowing interference fringe images with different phases to be simultaneously obtained. Complex amplitude information is obtained from these interference fringe images, and a reconstructed image at any depth can be obtained by performing a light backpropagation calculation. It has been reported that this optical system has been able to capture video at a frame rate of 25 fps (Non-Patent Document 1).

On the other hand, as shown in Figure 8, an optical system has also been proposed that uses a reflective liquid crystal panel instead of a birefringent lens. Object light from a subject 1 passes through a lens 2, a wavelength filter 3, and a polarizing plate 4, becoming a linearly polarized light wave. This linearly polarized light is incident on a reflective liquid crystal panel 8 via a beam splitter (BS) 7. The reflective liquid crystal panel 8 imparts a different spherical phase distribution to polarization directions that are ±45° from this polarization direction.

The object light reflected by the reflective liquid crystal panel 8 and beam splitter (BS) 7 passes through the quarter-wave plate 9, becoming clockwise and counterclockwise circularly polarized light, which is then split into four directions by the diffraction grating 21 (since Figure 8 is a plan view, light is depicted in two directions, but in reality it is diffracted in four directions). This diffraction grating 21 may, for example, be a checkered diffraction grating in which two types of phase objects (objects that change only the phase of light) are arranged in a checkered pattern. Due to its periodic structure, a checkered diffraction grating (phase grating) can diffract light in four directions (up, down, left, and right), thereby propagating light of the same quality as the incident light in four directions.

Next, the light waves diffracted in four directions are incident on the polarizing plate array 22. Figure 9 shows an example of the transmission axis of the polarizing plate array 22. The polarizing plate array 22 is composed of four types (four regions) of linear polarizers with transmission axes at 0°, 45°, 90°, and 135°, for example. When the polarizers are installed so that their transmission axes form an angle of η with respect to the x-axis, right-handed circularly polarized light and left-handed circularly polarized light undergo phase shifts of +η and -η, respectively, and are output from the linear polarizer as two linearly polarized lights with the same polarization state but a relative phase difference of 2η. In other words, depending on the angle of the transmission axis of the linear polarizer, different phase shifts of 0, π/2, π, and 3π/2 [rad] are imparted to each pair of linearly polarized light for each region.

By capturing pairs of linearly polarized light transmitted through the polarizer array 22 with cameras 23 and 24 (actually, four cameras), interference fringe images of different phases can be simultaneously obtained. By obtaining complex amplitude information from these interference fringe images and performing backpropagation calculations of light, a reconstructed image at any depth distance can be obtained (Patent Document 1).

The imaging device in Figure 8 uses the polarizing plate array 22 and cameras 23 and 24 to capture the object light after it passes through the quarter-wave plate 9, making it possible to acquire interference fringes all at once, just like in Figure 7. Furthermore, this method can acquire interference fringes in each polarization direction with high resolution, so the resolution of the interference fringe image is twice as high both vertically and horizontally as in Figure 7.

Japanese Patent Application Laid-Open No. 2021-131457

KiHong Choi, Kyung-Il Joo, Tae-Hyun Lee, Hak-Rin Kim, Junkyu Yim, Hyeongkyu Do, and Sung-Wook Min, “Compact self-interference incoherent digital holographic camera system with real-time operation,” Optics Express, Vol. 27, No 4, pp. 4818-4833, (2019)

The optical system of the imaging device shown in Figure 7 uses a birefringent lens 5. However, when constructing a lens from a birefringent material, it is difficult to obtain a material large enough to form a lens with a birefringence large enough to be used in incoherent digital holography. Furthermore, a diffractive birefringent lens 5 generates unnecessary diffracted light, which causes degradation of the reconstructed image.

The optical system of the imaging device shown in Figure 8 uses a beam splitter (BS) 7. In this optical system, the object light passes through the beam splitter twice, reducing the light utilization efficiency to 1/4. Furthermore, if the object light is incident on a reflective LCD panel at an angle without using a beam splitter, the light utilization efficiency does not decrease, but due to the angle dependency of the LCD panel, it is not possible to accurately impart a spherical phase distribution.

Therefore, in consideration of the above-mentioned problems, the object of the present invention is to provide an imaging device and imaging method that improves light utilization efficiency and enables high-quality hologram images/reconstructed images to be obtained compared to conventional incoherent digital holography imaging devices.

To solve the above problem, the imaging device of the present invention comprises a first polarizing plate that converts incoherent light waves into linearly polarized light; a polarizing beam splitter that splits the light waves transmitted through the first polarizing plate into first and second split lights according to the polarization direction; first and second mirrors with different curvatures that reflect the first and second split lights, respectively; a first quarter-wave plate disposed between the polarizing beam splitter and the first mirror; a second quarter-wave plate disposed between the polarizing beam splitter and the second mirror; and a third quarter-wave plate that converts the first split light reflected by the first mirror and transmitted through the first quarter-wave plate and the second split light reflected by the second mirror and transmitted through the second quarter-wave plate into circularly polarized light. The imaging device is characterized by capturing the first and second split lights transmitted through the third quarter-wave plate through a polarizing plate, thereby simultaneously acquiring multiple interference fringes.

Furthermore, it is desirable that the imaging device captures the first and second split lights that have passed through the third quarter-wave plate using a polarization camera, and simultaneously acquires interference fringes of different phases.

Furthermore, it is desirable that the imaging device diffracts the first and second split lights that have passed through the third quarter-wave plate in multiple directions using a diffraction grating, and photographs the diffracted lights in each direction using a camera through polarizing plates with different polarization directions, thereby simultaneously obtaining interference fringes of different phases.

Furthermore, it is desirable that the imaging device splits the first and second split lights that have passed through the third quarter-wave plate into two optical paths using a beam splitter after passing through a polarizing plate, and captures images using cameras positioned on each optical path at different distances from the beam splitter, thereby simultaneously acquiring interference fringes at different optical path distances.

Furthermore, it is desirable that the imaging device further obtains complex amplitude information from multiple interference fringes of different phases using a phase shift method, and performs backpropagation calculations of light to obtain a reconstructed image at any depth distance.

Furthermore, it is desirable that the imaging device further obtains phase information by phase retrieval from amplitude information of interference fringes acquired at different distances, and performs backpropagation calculations of light using the acquired amplitude information and the obtained phase information, thereby obtaining a reconstructed image at any depth distance.

To solve the above problems, the incoherent digital holography imaging method of the present invention splits a light wave transmitted through a polarizing plate into first and second split lights using a polarizing beam splitter, then passes the first and second split lights through quarter-wave plates, reflects them off mirrors with different curvatures, and then passes them again through the quarter-wave plate to be combined by the polarizing beam splitter. The combined first and second split lights are then photographed by a camera through a polarizing plate with a polarization direction different from that of the quarter-wave plate, thereby simultaneously obtaining interference fringes of different phases.

To solve the above problems, the incoherent digital holography imaging method of the present invention splits a light wave transmitted through a polarizing plate into first and second split lights using a polarizing beam splitter, passes the first and second split lights through quarter-wave plates, reflects them off mirrors with different curvatures, and then passes them again through the quarter-wave plate and combines them using the polarizing beam splitter. The combined first and second split lights then pass through the quarter-wave plate and polarizing plate and are split into two optical paths using a beam splitter. Images are taken with cameras positioned on each optical path at different distances from the beam splitter, thereby simultaneously obtaining interference fringes with different optical path lengths.

The imaging device and imaging method of the present invention improve the light utilization efficiency and enable the production of high-quality hologram images/reconstructed images compared to conventional incoherent digital holography imaging devices.

1 is a diagram illustrating the principle of an interferometer used in an imaging device of the present invention. 1 is a schematic diagram of an imaging device according to a first embodiment of the present invention. FIG. 10 is a schematic diagram of an imaging device according to a second embodiment of the present invention. FIG. 10 is a schematic diagram of an imaging device according to a third embodiment of the present invention. 10 is an example of four interference fringes with different phases when a point object is photographed by the imaging device of the present invention. 10 is an example of a reconstructed image of one frame when a moving grayscale object is captured as a moving image by the imaging device of the present invention. 1 is an example of a conventional incoherent digital holography imaging device. 1 is an example of a conventional incoherent digital holography imaging device. 1A and 1B are diagrams illustrating examples of transmission axes of a polarizing plate array.

Figure 1 shows the principle of the interferometer used in the imaging device of the present invention. The interferometer is composed of a polarizing plate 11, a polarizing beam splitter (PBS) 12, quarter-wave plates 13, 15, and 17, a concave mirror 14, and a plane mirror 16. Furthermore, the imaging device is equipped with a polarizing plate 18 and a camera 19 to capture interference fringes. Each component is explained below.

Polarizing plate 11 (first polarizing plate) converts the object light from the subject into linearly polarized light. For example, polarizing plate 11 is installed so that only linearly polarized light at 45° to the horizontal plane is transmitted.

The polarizing beam splitter (PBS) 12 splits the object light transmitted through the polarizing plate 11 into a first split light and a second split light based on its polarization components. The PBS 12 reflects the s-polarized component (referred to as the first split light) of the object light transmitted through the polarizing plate 11, changing its direction of travel (upward in the drawing), and transmits the p-polarized component (referred to as the second split light) of the object light transmitted through the polarizing plate 11. As described below, after reflection from the mirror, the first split light enters the PBS 12 as p-polarized light, and the second split light enters the PBS 12 as s-polarized light. Therefore, the PBS 12 transmits the first split light after reflection from the mirror and reflects the second split light, changing its direction of travel (downward in the drawing), thereby combining the first and second split lights.

The quarter-wave plate 13 (first quarter-wave plate) transmits the s-polarized component of the object light (first split light) reflected by the PBS 12, converting it to circularly polarized light. It also transmits the circularly polarized light reflected by the concave mirror 14, converting it to p-polarized light, and directs it to the PBS 12.

The quarter-wave plate 15 (second quarter-wave plate) transmits the p-polarized component of the object light (second split light) that has passed through the PBS 12, converting it to circularly polarized light. It also transmits the circularly polarized light that is reflected by the mirror 16 and incident on it, converting it to s-polarized light, and directs it to the PBS 12.

The concave mirror 14 (first mirror) imparts a phase distribution with a predetermined focal length (curvature) to the circularly polarized light that has passed through the quarter-wave plate 13, and reflects it toward the quarter-wave plate 13.

The plane mirror 16 (second mirror) imparts a plane (infinite focal length) phase distribution to the circularly polarized light that has passed through the quarter-wave plate 15, and reflects it toward the quarter-wave plate 15. Note that in this principle diagram, mirror 16 is described as a plane mirror, but it may be any mirror with a focal length (curvature) different from that of the concave mirror 14.

The quarter-wave plate 17 (third quarter-wave plate) transmits the first and second split lights that are reflected by the mirror and transmitted/reflected by the PBS 12, converting them into right-handed and left-handed circularly polarized light, respectively.

In this interferometer, the first and second split lights interfere due to a slight difference in optical path caused by reflections from the concave mirror 14 and the plane mirror 16. Interference fringes can be obtained by capturing images of the first and second split lights after they pass through the quarter-wave plate 17 using a camera 19 via a polarizing plate 18. For example, multiple interference fringes with different phases can be simultaneously captured using a polarization camera. Complex amplitude information at the imaging plane can then be calculated from these interference fringe images, and a reconstructed image at any depth distance can be obtained by performing a backpropagation calculation of the light.

In this description, the s-polarized component of the object light is referred to as the first split light, and the p-polarized component of the object light is referred to as the second split light, but the first and second split lights may be reversed.

In the interferometer (optical system) of the imaging device of the present invention, the s-polarized component of the object light incident on PBS 12 is reflected by concave mirror 14, passes through quarter-wave plate 13 again, becomes p-polarized, and passes through PBS 12. That is, all of the s-polarized components of the object light incident on PBS 12 become p-polarized and pass through PBS 12, eliminating the attenuation of light that occurs when an interferometer is configured using a beam splitter (BS) 7, as in conventional technology. Similarly, the p-polarized component of the object light that passes through PBS 12 is reflected by plane mirror 16, passes through quarter-wave plate 15 again, becomes s-polarized, and is reflected by PBS 12. All of the p-polarized components of the object light incident on PBS 12 become s-polarized and are reflected by PBS 12, eliminating the attenuation of light that occurs when an interferometer is configured using a beam splitter (BS) 7. This improves light utilization efficiency.

In addition, the PBS 12, concave mirror 14, and plane mirror 16 that make up this interferometer are common optical components, and the size of the interference fringes can be easily adjusted according to the required resolution of the reconstructed image by changing the focal length of the concave mirror 14 or replacing the plane mirror 16 with a concave mirror. Furthermore, because a diffractive birefringent lens is not used, noise caused by harmonic components due to diffraction can be suppressed. Furthermore, unlike birefringent materials or diffractive lenses, concave and plane mirrors are not affected by chromatic aberration.

Below, we describe an embodiment of an incoherent digital holography imaging device that improves light utilization efficiency by configuring an interferometer using a polarizing beam splitter (PBS) without using a birefringent lens or a reflective liquid crystal panel.

(First embodiment)
2 is a schematic diagram of an imaging device according to a first embodiment of the present invention. The imaging device includes an interferometer made up of a polarizing plate 11, a polarizing beam splitter (PBS) 12, quarter-wave plates 13, 15, and 17, a concave mirror 14, and a plane mirror 16, as well as a lens 2, a wavelength filter 3, and a polarization camera 20. The configuration of the interferometer is the same as that shown in FIG. 1, so a description of the optical elements that make up the interferometer will be omitted.

Object light from subject 1 is an incoherent light wave that enters lens 2. Note that object light may be reflected light, transmitted light, or light emitted from subject 1.

Lens 2 focuses the object light and makes it incident on wavelength filter 3. Like a normal camera lens, lens 2 has adjustment functions such as image magnification and wide angle. Note that subject 1 can be positioned anywhere, regardless of the focal position of lens 2.

Wavelength filter 3 is a bandpass filter that transmits light waves with a specified wavelength range (e.g., 3 nm to 20 nm) and improves the temporal coherence of the light waves. Narrowing the wavelength range improves image quality but reduces the amount of light in the image, so an appropriate wavelength filter 3 is selected depending on the desired image. Light waves that pass through wavelength filter 3 are incident on polarizing plate 11 of the interferometer.

Note that the lens 2 and wavelength filter 3 are not essential components of the imaging device, and the object light may be input directly to the polarizing plate 11.

The behavior of the object light after entering polarizing plate 11 and the function of each optical element are as explained in the principle diagram in Figure 1. The object light passing through polarizing plate 11 becomes linearly polarized at 45° to the horizontal plane, and PBS 12 reflects the s-polarized component and transmits the p-polarized component. The s-polarized component of the object light passes through quarter-wave plate 13 and becomes circularly polarized light. It is reflected by concave mirror 14, passes through quarter-wave plate 13 again and becomes p-polarized light, and passes through PBS 12. The p-polarized component of the object light passes through quarter-wave plate 15 and becomes circularly polarized light, is reflected by plane mirror 16, passes through quarter-wave plate 15 again and becomes s-polarized light, and is reflected by PBS 12. These two beams (the first and second split beams) are converted to clockwise and counterclockwise circularly polarized light by quarter-wave plate 17. A slight optical path difference occurs between the two beams due to reflections from concave mirror 14 and plane mirror 16, causing interference between them.

This interference light is captured by a polarization camera 20 equipped with polarizing plates spaced 45° apart for each pixel. For example, a polarization camera 20 can be used in which each pixel has a 3.75 μm pitch and four types of polarizing plates are installed at 45° intervals for every four adjacent 2x2 pixels. By constructing an image from pixels with different polarization directions, interference fringes can be captured with a resolution of 6.5 μm pitch in both the vertical and horizontal directions, resulting in four interference fringes with different phases.

The imaging device may further include an information processing device (not shown). The information processing device obtains complex amplitude information of the subject 1 on the imaging plane of the polarization camera 20 from the four acquired interference fringes using a phase shift method or the like. Furthermore, an image at any depth distance can be reconstructed from this complex amplitude information using wavefront backpropagation calculations (see Patent Document 1). According to this embodiment, light utilization efficiency is higher than conventional methods and exposure time can be shortened, making it easy to acquire moving images.

Second Embodiment
3 is a schematic diagram of an imaging device according to a second embodiment of the present invention. The imaging device includes an interferometer made up of a polarizing plate 11, a polarizing beam splitter (PBS) 12, quarter-wave plates 13, 15, and 17, a concave mirror 14, and a plane mirror 16, as well as a lens 2, a wavelength filter 3, a diffraction grating 21, a polarizing plate array 22, and cameras 23 and 24.

Object light from subject 1 is an incoherent light wave that enters lens 2. The functions of lens 2 and wavelength filter 3 are the same as in the first embodiment. Furthermore, since the configuration of the interferometer is the same as in Figure 1, a description of each optical element that makes up the interferometer will be omitted. The object light is split into first and second split lights within the interferometer, which are reflected by concave mirror 14 and plane mirror 16, respectively, and converted into clockwise and counterclockwise circularly polarized light by quarter-wave plate 17.

The object light (first and second split lights) that passes through the interferometer is split into four directions by the diffraction grating 21 (although Figure 3 shows light in two directions, in reality it is diffracted in four directions). This diffraction grating 21 uses, for example, a checkered diffraction grating in which two types of phase objects (objects that only change the phase of light) are arranged in a checkered pattern.

Next, the diffracted light split into four directions is incident on each region of the polarizing plate array 22. Polarizing plate array 22 is composed of four types (four regions) of linear polarizers with transmission axes of 0°, 45°, 90°, and 135°, as shown in Figure 9. Depending on the angle of the transmission axis of the linear polarizer, different phase shift amounts of 0, π/2, π, and 3π/2 [rad] are imparted to each set of linearly polarized light for each region.

By capturing the pairs of linearly polarized light that have passed through the polarizer array 22 with cameras 23 and 24 (actually, four cameras), four interference fringe images with different phases can be obtained simultaneously. Note that while four cameras are used here, it is also possible to simultaneously capture four interference fringe images with a single camera (image sensor) with a large light-receiving area.

The imaging device may further include an information processing device (not shown). The information processing device obtains the complex amplitude distribution of the subject 1 on the imaging plane from the four acquired interference fringes using a phase shift method or the like, and then reconstructs an image at any depth distance from this complex amplitude distribution using wavefront backpropagation calculations, just as in the first embodiment.

While the above embodiment uses a checkerboard diffraction grating to split light into four directions, a linear diffraction grating may be used to split light into three directions. For example, if a diffraction grating (light modulation element) that periodically changes the incident light in one axial direction (x direction) and imparts a constant two-level phase distribution in the orthogonal direction (y direction) is used as the diffraction grating 21, the first and second split light beams, which are left-handed and right-handed circularly polarized light beams that pass through the quarter-wave plate 17, are each split into three beams (center and left and right). The polarizer array 22 is a three-area split polarizer (a polarizer consisting of three linear polarizers with different transmission axis directions at the center and left and right), and the three split diffracted beams are incident on each of the three areas of the three-area split polarizer. By capturing the light that passes through each area with three cameras, three interference fringe images with different phases can be simultaneously obtained.

Furthermore, the information processing device can use a phase shift method or other method to obtain a complex amplitude distribution on the imaging plane from the three acquired interference fringes, and then use wavefront backpropagation calculations to reconstruct an image at any depth distance from this complex amplitude distribution.

In this way, while the first embodiment (Figure 2) uses the polarization camera 20 to separate each polarization component, the second embodiment (Figure 3) uses a diffraction grating 21, a polarizing plate array 22, and cameras 23 and 24 to separate the polarization components and simultaneously acquire interference fringes of different phases. In this embodiment, interference fringes can be acquired at high density by each camera, thereby improving the resolution of the interference fringes compared to the first embodiment.

(Third embodiment)
4 shows a schematic diagram of an imaging device according to a third embodiment of the present invention. The imaging device according to the third embodiment is an incoherent digital holography imaging device that acquires complex amplitude information of interference fringes by phase retrieval. The imaging device includes an interferometer consisting of a polarizing plate 11, a polarizing beam splitter (PBS) 12, quarter-wave plates 13, 15, and 17, a concave mirror 14, and a plane mirror 16, as well as a lens 2, a wavelength filter 3, a polarizing plate 25, a beam splitter (BS) 26, and cameras 27 and 28.

Object light from subject 1 is an incoherent light wave that enters lens 2. The functions of lens 2 and wavelength filter 3 are the same as in the first embodiment. Furthermore, since the configuration of the interferometer is the same as in Figure 1, a description of each optical element that makes up the interferometer will be omitted. The object light is split into first and second split lights within the interferometer, which are reflected by concave mirror 14 and plane mirror 16, respectively, and converted into clockwise and counterclockwise circularly polarized light by quarter-wave plate 17.

The object light (first and second split lights) that passes through the quarter-wave plate 17 passes through the polarizing plate 25 and becomes linearly polarized light. It is then split into two optical paths by the beam splitter (BS) 26.

The cameras 27 and 28 for each optical path are installed at different distances from the beam splitter (BS) 26. By capturing the split object light (including the first split light and the second split light) with cameras 27 and 28, respectively, interference fringes with different optical path distances (and therefore magnification ratios) can be simultaneously obtained.

The imaging device may further include an information processing device (not shown). The information processing device can obtain phase information from the intensity distributions (amplitude information) of two interference fringes acquired at different distances using phase retrieval methods such as the TIE (Transport of Intensity Equation) method or the GS (Gerchberg-Saxton) algorithm. Images at any depth distance can be reconstructed by performing backpropagation calculations of light using the acquired amplitude information and the obtained phase information.

This embodiment obtains complex amplitude information using phase retrieval, a technique different from the phase shift method. However, as with the first and second embodiments, the efficiency of light utilization can be improved by configuring the interferometer using a polarizing beam splitter (PBS).

(Test results and verification of effects)
FIG. 5 shows an example of four interference fringes with different phases when a point object is photographed by the imaging device according to the first embodiment of the present invention.

Figure 5(a) shows interference fringes when the polarization direction of the polarizer installed in the pixel is 0° relative to the horizontal direction. Figure 5(b) shows interference fringes when the polarization direction is 135°, Figure 5(c) shows interference fringes when the polarization direction is 45°, and Figure 5(d) shows interference fringes when the polarization direction is 90°. Each image in Figure 5 is an image of 1024 x 1024 pixels. Using wavefront backpropagation calculations, it is possible to reconstruct an image at any depth distance from the four acquired interference fringes. It has been confirmed that this invention achieves higher light utilization efficiency than conventional methods and can capture clearer interference fringes.

Figure 6 shows an example of a reconstructed image of one frame when a moving grayscale image is captured as a video using the imaging device of the first embodiment of the present invention. The image shows a grayscale chart with different brightness levels in the horizontal direction (the upper side is bright on the right and dark on the left, the center is a black line, and the lower side is dark on the right and bright on the left). It is an image of the chart being moved horizontally.

Figure 6(a) shows a reconstructed image of one frame taken in grayscale at a frame rate of 10 fps. At 10 fps, the boundaries between each brightness level are unclear. On the other hand, Figure 6(b) shows a reconstructed image of one frame taken at a frame rate of 60 fps. The image is not blurred, and the boundaries between each brightness level are clear.

The imaging device of the present invention has high light utilization efficiency and can shorten exposure times, making it easy to capture moving images. Therefore, it has been confirmed that it is possible to capture moving images (reconstructed images) at a frame rate of 60 fps.

In the embodiments of the present invention, the configuration and operation of an imaging device have been described, but the present invention is not limited to this and may also be configured as an imaging method for incoherent digital holography. That is, the imaging method may be configured in such a way that, following the flow of object light (light waves) in each figure, a light wave transmitted through a polarizing plate is split into first and second divided lights by a polarizing beam splitter, the first and second divided lights are each reflected by mirrors with different curvatures through a quarter-wave plate, and then combined by the polarizing beam splitter after passing through the quarter-wave plate again. The combined first and second divided lights are then photographed by a camera through the quarter-wave plate and polarizing plate, thereby simultaneously acquiring multiple interference fringes.

The above-described embodiments have been described as representative examples, but it will be apparent to those skilled in the art that numerous modifications and substitutions are possible within the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the above-described embodiments, and various modifications and alterations are possible without departing from the scope of the claims. For example, the functions contained in each block, step, etc. described in the embodiments can be rearranged so as not to result in logical inconsistencies, and multiple constituent blocks, steps, etc. can be combined into one or divided.

1 Object 2 Lens 3 Wavelength filter 4 Polarizer 5 Birefringent lens 6 1/4 wave plate 7 Beam splitter 8 Reflective liquid crystal panel 9 1/4 wave plate 11 Polarizer 12 Polarizing beam splitter 13 1/4 wave plate 14 Concave mirror 15 1/4 wave plate 16 Plane mirror 17 1/4 wave plate 18 Polarizer 19 Camera 20 Polarized camera 21 Diffraction grating 22 Polarizer array 23 Camera 24 Camera 25 Polarizer 26 Beam splitter 27 Camera 28 Camera

Claims (8)

a first polarizer for converting incoherent light waves into linearly polarized light;
a polarizing beam splitter that splits the light wave transmitted through the first polarizing plate into a first split light and a second split light according to the polarization direction;
first and second mirrors having different curvatures that reflect the first divided light and the second divided light, respectively;
a first quarter-wave plate disposed between the polarizing beam splitter and the first mirror;
a second quarter-wave plate disposed between the polarizing beam splitter and the second mirror;
a third quarter-wave plate that converts the first split light reflected by the first mirror and transmitted through the first quarter-wave plate and the second split light reflected by the second mirror and transmitted through the second quarter-wave plate into circularly polarized light;
Equipped with
an imaging device, characterized in that the first split light and the second split light that have passed through the third quarter-wave plate are photographed through a polarizing plate, and a plurality of interference fringes are simultaneously obtained. 2. The imaging device according to claim 1,
an imaging device, characterized in that the first split light and the second split light that have passed through the third quarter-wave plate are photographed by a polarization camera, and interference fringes of different phases are simultaneously obtained. 2. The imaging device according to claim 1,
an imaging device characterized in that the first divided light and the second divided light that have passed through the third quarter-wave plate are diffracted in a plurality of directions by a diffraction grating, and the diffracted light in each direction is photographed by a camera through a polarizing plate of a different polarization direction, thereby simultaneously obtaining interference fringes of different phases. 2. The imaging device according to claim 1,
an imaging device, characterized in that the first split light and the second split light that have passed through the third quarter-wave plate are split into two optical paths by a beam splitter through a polarizing plate, and the first split light and the second split light are photographed by cameras arranged on each optical path at different distances from the beam splitter, thereby simultaneously obtaining interference fringes at different optical path distances. 4. The imaging device according to claim 2,
Furthermore, the imaging device is characterized in that it obtains complex amplitude information from a plurality of interference fringes of different phases by a phase shift method, and performs a back propagation calculation of light to obtain a reconstructed image at any depth distance. 5. The imaging device according to claim 4,
Furthermore, the imaging device is characterized in that it obtains phase information by phase retrieval from amplitude information of interference fringes acquired at different distances, and performs back propagation calculations of light using the acquired amplitude information and the obtained phase information, thereby obtaining a reconstructed image at any depth distance. An incoherent digital holography imaging method characterized by splitting a light wave transmitted through a polarizing plate into first and second split lights using a polarizing beam splitter, having the first and second split lights each pass through a quarter-wave plate, reflected by mirrors with different curvatures, and then combined by the polarizing beam splitter after passing through the quarter-wave plate again, and then photographing the combined first and second split lights with a camera through a polarizing plate with a polarization direction different from that of the quarter-wave plate, thereby simultaneously obtaining interference fringes of different phases. An incoherent digital holography imaging method in which a light wave transmitted through a polarizing plate is split into first and second split lights by a polarizing beam splitter, the first and second split lights are each passed through a quarter-wave plate and reflected by mirrors with different curvatures, and then passed through the quarter-wave plate again and combined by the polarizing beam splitter. The combined first and second split lights are then passed through the quarter-wave plate and polarizing plate and split into two optical paths by a beam splitter, and images are taken with cameras positioned on each optical path at different distances from the beam splitter, thereby simultaneously obtaining interference fringes at different optical path lengths.