JP7744766B2 - Incoherent digital holographic imaging device - Google Patents

Description

The present invention relates to an incoherent digital holography imaging device that acquires digital holography using incoherent light with a short coherence length.

Digital holography is an imaging technique that can acquire the complex amplitude (amplitude and phase distribution) of a subject, and has many advantages, including excellent spatial and depth resolution, as well as the ability to adjust the focus position through calculations. In particular, incoherent digital holography technology has advanced in recent years, allowing digital holograms to be captured using incoherent light such as sunlight, LEDs, and fluorescent light, without the need for special light sources such as lasers, and this has expanded the range of applications for holography.

In incoherent digital holography, the object light is split into two beams, and a hologram (interference fringes) is formed on the imaging surface by causing them to self-interfere with each other.
In order to cause interference of incoherent light, the wavelength width of the light source is limited to 100 nm or less using a wavelength filter (bandpass filter) (Non-Patent Document 1).

J. Rosen and G. Brooker: “Digital spatially incoherent Fresnel holography”, Optics Letters Vol. 32, No. 8, pp. 912-914 (2007)

However, for example, as described above, if the wavelength width of natural light is limited to the extent that coherence of the two lights is obtained, the light utilization efficiency will be significantly reduced, which will result in a problem of a significant decrease in S/N due to optical shot noise in the imaging element, etc.
Furthermore, for example, an image of an object is reconstructed by performing a predetermined calculation on a hologram image captured by an image sensor. However, the image of the object obtained in this manner has a problem in that noise in the image sensor has a significantly greater effect on the quality of the reconstructed image than in a normal imaging method in which light from the object is directly incident on the image sensor to capture the image of the object.
Conversely to the above-mentioned problem, there are also cases where it is desired to make a predetermined image have a lower image quality (for example, a blurred image).
Therefore, it is desirable to easily and accurately form a new image of an object with a desired image quality from a reconstructed image of the object based on the above-mentioned hologram image.

The present invention has been made in consideration of the above circumstances, and aims to provide an incoherent digital holography imaging device that can easily and accurately generate a new image of a subject with the desired image quality from a reconstructed image of the subject obtained using holography technology.

The incoherent digital holographic imaging device of the present invention comprises:
a first imaging function unit that captures a hologram image formed by causing incoherent light from a subject, which is incident through an imaging lens and split into two systems, to interfere with each other, and obtains a first image that is a reconstructed image of the subject; and a second imaging function unit that focuses a single light beam incident through the imaging lens from the subject, and obtains a second image that is an image of the subject simultaneously with or sequentially to the first image,
an image combining unit that combines information contained in the first image and information contained in the second image to form a new image of the subject ;
The image combination unit is configured to identify, for each part of the subject, a predetermined area in the first image having position information indicating the distance to that part based on the level of contrast, set an area in the second image corresponding to the predetermined area in the identified predetermined area of the first image, and form a new first image .
Preferably, the second imaging function unit includes a shutter that blocks one of the two split beams of light when obtaining the second image .
Here , it is preferable that the first imaging function unit is configured to determine positional information relating to the first image , which indicates the distance from the imaging surface to each part of the subject, based on the contrast of the first image when the complex amplitude distribution of the obtained hologram image is back- propagated.

Furthermore, it is preferable that the imaging optical system in the first imaging function unit includes a beam splitter that splits the beam from the subject into two systems, a plane mirror that receives one of the split beams and reflects it as a plane wave, a concave mirror that receives the other of the split beams and reflects it so as to converge as a spherical wave, an imaging element that obtains a hologram image by causing the plane wave from the plane mirror and the spherical wave from the concave mirror to interfere with each other, and a wavelength filter that narrows the wavelength range of the light waves that are incident on the imaging element on a common optical path of the plane wave and the spherical wave.
It is also preferable to provide a phase shifting means for shifting either the plane mirror or the concave mirror by a predetermined phase in the optical axis direction.

Furthermore, it is preferable that the imaging optical system in the second imaging function unit is configured so that at least a portion thereof is shared with the imaging optical system in the first imaging function unit, and that it comprises the light beam splitting means, the concave mirror that receives the other light beam split by the light beam splitting means and reflects it to converge as a spherical wave, and the imaging element that forms an image of the subject by focusing the spherical wave from the concave mirror.

In addition, the imaging optical system in the first imaging function unit and the imaging optical system in the second imaging function unit share an optical path in which a first polarizer is disposed up to a beam splitter that splits a beam from a subject, but each of them is provided with an imaging element separately,
The light beam splitting means is a spatial light modulator,
It is preferable that a wavelength filter and a second polarizer are arranged on a common optical path of the plane wave and the spherical wave from the beam splitting means to the image sensor of the first imaging function unit so that a hologram image can be obtained at the image sensor of the first imaging function unit, and that the spherical wave from the beam splitting means to the image sensor of the second imaging function unit is imaged on the image sensor of the second imaging function unit to obtain an image of the subject.

In incoherent digital holography imaging technology, the reconstructed image obtained (hereinafter referred to as the first image) contains position information and can be used to construct a three-dimensional image, but it also has the characteristic of containing a lot of noise.
The inventors of the present application therefore came up with the idea of simultaneously acquiring an image (hereinafter referred to as the second image) using a common optical system and the first image, which is obtained using a normal imaging method that is less affected by noise, even though it is not possible to obtain positional information for each part, and then combining these two images to form a new image of the subject with the desired image quality, taking advantage of the fact that corresponding parts of the subject in both images can be easily distinguished.

In other words, as an example, positional information for each part of the subject is obtained based on a first image, which is a reconstructed image of the subject obtained using a hologram in the first imaging function unit, and a new first image is formed by arranging each part of the second image obtained by the second imaging function unit based on the obtained positional information.

As a result, the incoherent digital holography imaging device of the present invention can obtain a new image of desired image quality based on the information of the obtained first and second images. Moreover, because both images can be captured substantially simultaneously using a common optical system, a new image of desired image quality can be obtained easily and with high accuracy.
Specifically, using the above example, in incoherent digital holography imaging technology, it is possible to prevent the decrease in S/N ratio that accompanies the wavelength width restriction of light that is imposed in order to obtain light coherence, improve the problem of the imaging element being susceptible to noise, and obtain a three-dimensional reconstructed image of the subject that is less susceptible to noise.
Furthermore, by utilizing this invention, it is possible to construct cameras, measuring devices, microscopes, and the like that can accurately capture information about a subject.

1 is a conceptual diagram for explaining a holographic imaging and reproducing device according to a first embodiment of the present invention. FIG. 10 is a conceptual diagram for explaining a holographic imaging and reproducing device according to a second embodiment of the present invention. In the holographic imaging and reproduction device according to the second embodiment of the present invention, the patterns displayed on the SLM are (a) a spherical wave pattern focused on the first imaging element 106a, (b) a spherical wave pattern focused on the second imaging element 106b, and (c) a combination of (a) and (b)). FIG. 10 is a conceptual diagram showing the premise of a method for improving the image quality of a reconstructed image by a system that combines holographic imaging and single-light imaging in a holographic imaging and reconstructing device according to a second embodiment of the present invention. 5A and 5B are diagrams showing the image states resulting from adding noise to the two imaging techniques shown in FIG. 4 (the upper half is imaging using holography, and the lower half is imaging using a single light source). FIG. 10 is a conceptual diagram for explaining a technique for capturing an image with an angle of view that includes three objects A, B, and C at different distances using a holographic imaging and reproducing device according to a second embodiment of the present invention. FIG. 7 is a conceptual diagram for explaining a method for forming a useful image from two types of images obtained by the two photographing methods shown in FIG. 6 . FIG. 10 is a conceptual diagram for explaining a holographic imaging and reproducing device according to a first modified embodiment of the present invention. FIG. 10 is a conceptual diagram for explaining a holographic imaging and reproducing device according to a second modified embodiment of the present invention.

Hereinafter, an incoherent digital holographic imaging device and imaging method of the present invention will be described using an embodiment, in which the configuration of a holographic imaging and reproducing device is taken as an example.
The following description will first focus on the configuration of the optical system using Embodiments 1 and 2, and then explain an example of a technique for combining a reconstructed image of a subject using holography with a general subject image using a single light, based on the configuration of Embodiment 2. After that, supplementary explanations will be given of the optical system of the above-mentioned holographic imaging and reproduction device, citing two modified embodiments.

[Configuration of holographic imaging and reproduction device (mainly optical system)]
(Embodiment 1)
FIG. 1 shows the overall configuration, mainly including the optical system, of a holographic imaging and reproducing apparatus 50 according to a first embodiment of the present invention.
This holographic imaging and reproducing device 50 constitutes an incoherent digital holographic imaging device using a Michelson interferometer optical system. This imaging and reproducing device 50 has a holographic imaging function and a single-light imaging function (imaging using a normal imaging system), and can use both functions to obtain low-noise incoherent digital holographic images.

First, we will explain holographic photography. Object light from a subject 1 is collimated by a lens 2 and enters a beam splitter (B/S) 3. One of the split beams is incident on a plane mirror 5 and reflected as a collimated beam, while the other split beam is incident on a concave mirror 4 and reflected as a convergent beam.
The two reflected beams of light are incident on the beam splitter (B/S) 3 again, and the former reflected light and the latter transmitted light travel toward the image sensor 6, forming a hologram on the imaging surface of the image sensor 6 by self-interference.

Here, the phase shift method is used to obtain the object light while avoiding the superposition of direct light and conjugate light in in-line holography, and among these, the four-step phase shift method is used to simplify the calculation.
The plane mirror 5 is moved in the optical axis direction by a phase shifting means (piezo element) 7 from a reference position by distances of 1/8, 2/8, and 3/8 times the wavelength (the optical path length of the light traveling toward the plane mirror 5 changes by 1/4, 2/4, and 3/4 times the wavelength), and the phase changes in four stages: 0, π/2, π, and 3π/2.

A light-blocking shutter 8 is shown on the beam splitter (B/S) 3 side of the plane mirror 5, but this is only functional when taking photographs using a single light beam, as described below, and is not functional when taking photographs using holography. On the other hand, a wavelength filter 9 is located on the beam splitter (B/S) 3 side of the imaging element 6 to narrow the wavelength range of light so that interference can occur even with incoherent light (light with a short coherence length).

Hologram image data is output from the imaging element 6 to the subject image reconstruction means 11, and a first image calculation unit 12 within the subject image reconstruction means 11 uses a phase shift method to calculate the amplitude and phase distributions on the imaging plane from the four pieces of hologram information formed on the imaging plane. Specifically, the amplitude and phase distributions at the subject position can be reconstructed by performing a calculation that backpropagates from the imaging plane to the subject plane.
Instead of the four-step phase shifting method, a three-step, two-step, or five-step or more phase shifting method may be used. Alternatively, a complex amplitude may be obtained in one imaging (exposure) by using a reference beam tilt, parallel phase shift, or random phase reference beam (see Ito and Shimobaba, "Introduction to Holography: 3D Imaging and Measurement Using a Computer," Kodansha, pp. 119-125).

Alternatively, instead of moving the plane mirror 5, the concave mirror 4 may be moved by the phase shift means 7, thereby performing a four-step phase shift method in which the phase of the light passing through the concave mirror 4 is changed in four steps. In this case, when photographing with a single light beam, as described below, photographing can be performed with the movement by the phase shift means 7 stopped, or photographing can be performed while moving the concave mirror 4 by the phase shift means 7, as in photographing using holography. In the latter case, an effect can be expected in which an image that is in focus over a wide depth range of the subject 1 can be obtained when photographing with a single light beam.

Next, we will explain shooting using a single light source. By operating the shutter 8 located on the beam splitter (B/S) 3 side of the plane mirror 5 and turning on the light blocking function, light passing through the plane mirror 5 is blocked, and only light passing through the concave mirror 4 reaches the image sensor 6. This shutter 8 can be a mechanical shutter, a liquid crystal shutter, or the like. As a result, an image (intensity distribution) of the subject 1 can be obtained directly from the image sensor 6. Alternatively, the shutter 8 can be located on the concave mirror 4 side, allowing only light from the plane mirror 5 to reach the imaging surface. In this case, it is possible to shoot the subject 1, which is in an imaging relationship between the lens 2 and the image sensor 6.

In addition, image data obtained by a single light is output from the imaging element 6 to the subject image reconstruction means 11, and multiple image data obtained by the single light are stored in the second image storage section 13 within the subject image reconstruction means 11.
Thereafter, the amplitude and phase distribution data obtained by the calculation in the first image calculation unit 12 and the image data stored in the second image storage unit 13 are combined in the image combination unit 14 within the subject image reconstructing means 11, and this combined reconstructed image (a new first image) is output as a subject image signal to an external monitor 15, etc. The image combination process performed in the image combination unit 14 will be described later.
The subject image reconstruction means 11, the monitor 15, and the like constitute a holographic reproduction device section 40 corresponding to the holographic imaging device section 20.

The device of this embodiment alternates between the above-mentioned holographic imaging function and the single-light imaging function. That is, during the first period, the shutter 8 is turned off and a hologram image of the subject 1 corresponding to phases of 0, π/2, π, and 3π/2 is captured using the four-step phase shift method; during the second period, the shutter 8 is turned on and an image of the subject 1 is acquired using only the light converged by the concave mirror 4.

Note that while wavelength filter 9 may be constantly operating, there is no need to limit the wavelength width when capturing images using a single light source during the second period. Therefore, in order to improve light utilization efficiency, it is desirable to operate wavelength filter 9 by switching it on and off in the same way as shutter 8 so that it does not operate during the second period. Methods for turning wavelength filter 9 on and off include physically inserting it into and removing it from the optical path, or using liquid crystal to change the transmission wavelength band.

In holographic imaging, the position of the image sensor 6 does not need to be near the focal length of the concave mirror 4, but in single-light imaging, it is desirable that the position of the image sensor 6 be near the focal length of the concave mirror in order to maintain resolution.
Furthermore, in the configuration of FIG. 1, it is necessary to selectively perform two types of photography by switching the time, and therefore it is desirable that the position of the image sensor 6 be near the focal length of the concave mirror 4 (or the plane mirror 5 when light from the plane mirror 5 is used for photography using a single light) in accordance with photography using a single light.

(Embodiment 2)
FIG. 2 shows the overall configuration, primarily of the optical system, of a holographic imaging and reproducing device 150 according to a second embodiment of the present invention. Since many of the components in this embodiment have substantially the same functions as those in the first embodiment, the reference numerals of those components are given the same reference numerals as those in the first embodiment, but with an additional 100, and detailed descriptions thereof will be omitted to avoid redundancy. The holographic reproducing device section 40 shown in the first embodiment has the same configuration, and is therefore omitted from the drawings (the same applies to FIGS. 6, 8, and 9 described below). Furthermore, in this embodiment, complex amplitudes are obtained by using a single imaging (exposure) technique, such as reference beam tilt, parallel phase shift, and the use of a random phase reference beam, rather than a phase shift technique (the same applies to Modifications 1 and 2 described below).
A feature of the holographic imaging and reproduction device 150 according to this embodiment is that, as shown in FIG. 2, it is possible to perform both types of imaging simultaneously by providing dedicated imaging elements 106a and 106b for both holographic imaging and single-light imaging.

As shown in Figure 2, light from the subject 101 passes through a first polarizer 110a, which is located after the lens 102 and transmits linearly polarized light at a 45-degree angle, before being split by the SLM 116. Plane waves and spherical waves reach the first image sensor 106a, while only spherical waves reach the second image sensor 106b. This allows holographic imaging at the former and single-light imaging at the latter. In other words, the plane wave reaching the first image sensor 106a is the vertically (or horizontally) linearly polarized component of the 45-degree linearly polarized incident light, and the spherical wave reaching the first image sensor 106a is the horizontally (or vertically) linearly polarized component of the 45-degree linearly polarized incident light. The second polarizer 110b, located on the SLM 116 side of the first image sensor 106a, aligns the polarization components of each light, causing the two lights to interfere with each other, resulting in a hologram.

As shown in FIG. 3, the pattern to be displayed on the SLM 116 may be a spherical wave (a) formed on the first image sensor 106a, a spherical wave (b) formed on the second image sensor 106b, or a pattern (c) obtained by combining (a) and (b).
This pattern has the effect of separating the incident horizontally (or vertically) linearly polarized light component into two spherical waves, but it is also possible to use a pattern in which the area of the SLM 116 is divided so that, for example, light reaching odd-numbered pixels is imaged on the first image sensor 106a and light reaching even-numbered pixels is imaged on the second image sensor 106b. This division does not have to be done in pixel units, and may be done in block units, each consisting of multiple pixels. Note that a reflective SLM 116 may also be used.

In the configuration of this embodiment, the shutter 8 in embodiment 1 is not necessary, and the wavelength filter 109 only needs to be placed on the SLM 116 side of the first image sensor 106a. This makes it possible to build a system that does not require switching of shutters, has a simple configuration, and enables faster image capture.

The distance from the SLM 116 to the image sensors 106a and 106b may be the same for both image sensors 106a and 106b, but they may also be positioned at different distances, such as placing the first image sensor 106a at the distance that is considered to provide the highest resolution in holographic imaging (the distance at which the images of the plane wave and spherical wave are the same size) and the second image sensor 106b at the focal length.

[Method of combining images to obtain a new reconstructed image]
A detailed description will now be given of a configuration of the holographic imaging and reproducing device 150 according to the second embodiment that combines holographic imaging and single-light imaging.
The configuration described below corresponds to the configuration of the image combination unit 14 in the subject image reconstructing means 11 described above.
In the following description, the term "object" may be used instead of the term "subject."
Figure 4 shows the general flow of holographic imaging and single-light imaging. The upper part shows a schematic diagram of the flow of hologram formation and object image reconstruction in holographic imaging (I). The numerical parameters used are those shown in Figure 2. For example, the distance between the SLM 116, which generates plane waves and spherical waves, and the image sensor 106a was set to 500 mm to obtain a hologram image formed on the imaging surface.

If the intensity distributions (I ₁ to I ₄ ) of four hologram images are obtained by changing the phase in four steps, 0, π/2, π, and 3π/2, using the four-step phase shift method, the complex amplitude distribution (amplitude/phase distribution) u on the imaging plane of the object is expressed by the following equation (1):
u = 1/4 × {(I ₁ - _{I 3} ) + i (I ₂ - _{I 4} )} (i is the imaginary unit) ... (1)
By performing a backpropagation operation on this complex amplitude distribution from the imaging plane to the object plane, a complex amplitude distribution (amplitude/phase distribution) at the object position is obtained, and a reconstructed image of the subject 101 is obtained.

The lower half of Figure 4 shows an object image captured using a single light source (II). For example, the distance between the SLM 116 that generates the spherical wave and the second image sensor 106b was set to 250 mm, and an object image (intensity distribution) formed on the imaging surface was acquired.

FIG. 5 shows the results of adding noise to the two imaging techniques shown in FIG.
It is assumed that random noise having a Gaussian distribution is added to the images acquired by the image sensors 106a and 106b, and the standard deviation of the Gaussian distribution is set to 1% or 3% of the maximum pixel value.
The upper half of Figure 5 shows how a reconstructed image is formed by adding noise to each of the four holograms _I1 to _I4 obtained by the first image sensor 106a using holography, while the lower half of Figure 5 shows how an image of an object is obtained by adding the above-mentioned noise to the object image obtained by the image sensor 106b using a single light source.

Figure 5 shows the reconstructed images along with their PSNR (Peak Signal to Noise Ratio) values. The PSNR values are shown for both the original image and the noise-free reconstructed image. It is clear that the images captured with a single light source are more resistant to noise, both in terms of appearance and PSNR value.
For example, if the acceptable threshold for image degradation is a PSNR of 30 relative to the output, then Fig. 5 clearly shows that even 1% noise is unacceptable in holographic imaging, whereas 3% noise is acceptable in single-light imaging.

In the example shown in Figure 5, the noise added by the two imaging techniques was set to the same level, but in reality, imaging using holography is more likely to be affected by noise due to the reduction in light intensity caused by wavelength bandwidth limitations.
That is, one of the main types of noise detected by the image sensor 106a is optical shot noise. If the number of incident photons is S, the optical shot noise is expressed as N = √S, and the S/N ratio is S/√S = √S, which is proportional to the square root of the number of photons.

For example, if a single-light image is taken with light of wavelengths between 380 and 780 nm without limiting the wavelength range with a wavelength filter, and if a wavelength filter is used to limit the wavelength range to 10 nm when taking holographic images, the amount of light in the latter image will be reduced to approximately one-tenth of the amount in the former image, and the S/N ratio will also deteriorate, depending on the influence of the spectral distribution.
Therefore, when this difference in the amount of incident light is taken into consideration, the comparison results of the image quality between the two photographing techniques show a larger difference than the values shown in FIG.

An example of a configuration according to an embodiment that can obtain a useful image from two types of images obtained by the device shown in FIG. 2 will now be described.
As shown in Fig. 6, an image is captured with an angle of view that includes three objects A, B, and C at different distances, and the images obtained by the two capturing techniques at that time are shown in Fig. 7. Note that holographic imaging and reproducing device 450 shown in Fig. 6 uses holographic imaging and reproducing device 150 of embodiment 2, but for convenience, the reference numerals of the corresponding components shown in Fig. 2 are increased by 300.
The reconstructed image using holography (hereinafter referred to as the "first image") contains a lot of noise (represented by dots within objects A, B, and C in Figure 7). However, by backpropagating the noise corresponding to the distances a, b, and c of each object, the contrast of the objects at those distances increases, and information about the objects at those distances can be obtained. On the other hand, the image captured using a single light (hereinafter referred to as the "second image") contains less noise, but the relationship between the distance and the object is unclear. Note that the range of distances in which objects exist is assumed to be within the depth of field when captured using a single light.

In order to obtain a low-noise image for each part of the object in the first image, only high-contrast pixel areas corresponding to the parts in the first image are extracted from the second image. That is, the high-contrast parts in the second image are identified, and the positions of the parts in the second image are set based on the position information of the corresponding parts in the first image, to form a new first image.
By doing so, it is possible to obtain a first image (reconstructed image) with less noise for the object located at each distance a, b, and c.
In Figure 7, the in-focus part (high contrast part) is extracted and used, but it is also possible to use information about out-of-focus parts in holographic photography to synthesize the out-of-focus part and also to create a blurred image.

In addition, as another application method, it is known that photography using holography contains information about the high spatial frequencies of an object compared to photography using a single light source. For example, by performing FFT processing on the images obtained using these two photography methods and combining the high-frequency information obtained by the former photography with the low-frequency information obtained by the latter photography to reconstruct the image, it is possible to obtain an image that combines both image quality and spatial frequency bandwidth.

Another possible use is when obtaining moving images. In other words, when using the four-step phase shift method in holographic imaging, it takes time to acquire four images and then calculate the reconstructed image, which may limit improvements in frame rate.

On the other hand, when shooting with a single light source, it is possible to shoot at a high frame rate up to the limits of the image sensor's performance. Therefore, video shooting at the highest frame rate uses image information from shooting with a single light source, and then uses a synthesis method similar to that shown in Figure 7. In other words, by extracting only the high-contrast pixel areas from the second image corresponding to the distance of each object in the reconstructed image obtained using holography, video images of the object at each object distance can be obtained.

Although distance information cannot be obtained with the time precision of the highest frame rate, this embodiment is a particularly effective method for capturing subjects where, for example, the movement of an object changes drastically within the same distance, but there is little change in the depth direction of the object.

As described above, the imaging device and imaging method of this embodiment can achieve the function of incoherent digital holography, which can acquire the complex amplitude (amplitude-phase distribution) of a subject, while retaining the functions of imaging using a normal imaging system, such as high S/N and video capture, and can be applied to various devices that accurately capture information about objects, such as cameras, measuring devices, and microscopes.

Furthermore, the incoherent digital holography imaging device and imaging method according to the present invention are not limited to the above-described embodiments, and various other modifications are possible.
For example, the optical system may be modified as shown in FIGS.
In addition, since many of the following modified embodiments have similar component functions to those of embodiment 2, for such components, the reference numerals of the components of embodiment 2 are given with 400 added for modified embodiment 1, and 500 added for modified embodiment 2, and detailed explanations thereof are omitted to avoid tediousness.

(Modification 1)
8, this modified embodiment has a configuration in which a rotary polarizer 517 that can rotate about the optical axis is arranged on the SLM 516 side of the image sensor 506, and which allows for temporal switching between holographic imaging and single-light imaging. In holographic imaging, the rotary polarizer 517 arranged on the SLM 516 side of the image sensor 506 operates to align the polarization directions of two light waves, as in the case of embodiment 2 shown in Fig. 2, but in single-light imaging, the rotary polarizer 517 is rotated to transmit only a spherical wave, which is a horizontally (or vertically) linearly polarized component.
In this case, it is essential to generate a spherical wave that forms an image on the imaging surface in accordance with the imaging conditions using a single light using the SLM 516. This configuration requires only one imaging element 506 and does not require a shutter, making it possible to achieve a simpler configuration.

(Modification 2)
As shown in Fig. 9, this modified example has a configuration in which a polarizing beam splitter (PBS) 603 is used to separate the object light into S-polarized light and P-polarized light. The separated S-polarized light is imaged on a second image sensor 606b via a lens 602a, and photography is performed using a single light beam. On the other hand, the separated P-polarized light is transmitted through a half-wave plate 618 as linearly polarized light at an angle of 45°. Thereafter, holographic photography is performed by the first image sensor 606a, as in the modified example 1 shown in Fig. 8. Compared to the modified example 1, this has the advantage of eliminating light loss in the rotating polarizer and enabling efficient use of incident light.

(Other changes)
As for other modifications to the optical system, for example, although the first embodiment uses a Michelson-type equal-path length optical system, it is also possible to use, for example, a Mach-Zehnder type optical system or a roundabout equal-path length Fizeau type optical system.

1, 101, 401, 501, 601 Object 2, 102, 402, 502, 602, 602a Lens 3 Beam splitter (B/S)
4 Concave mirror 5 Plane mirror 6, 106a, 106b, 406a, 406b, 506, 606a, 606b
Image pickup element 7 Phase shift means (piezo element)
8 shutter 9, 109, 409, 509, 609 wavelength filter 11 subject image reconstruction means 12 first image calculation unit 13 second image storage unit 14 image combination unit 15 monitor 20, 120, 420, 520, 620 holographic imaging device unit 40 holographic reproduction device unit 50, 150, 450, 550, 650 holographic imaging and reproduction device 110a, 110b, 410a, 410b, 510, 610 polarizer 116, 416, 516, 616 SLM
517 Rotating polarizer 603 Polarizing beam splitter (PBS)
618 Half wave plate

Claims (7)

a first imaging function unit that captures a hologram image formed by causing incoherent light from a subject, which is incident through an imaging lens and split into two systems, to interfere with each other, and obtains a first image that is a reconstructed image of the subject; and a second imaging function unit that focuses a single light beam incident through the imaging lens from the subject, and obtains a second image that is an image of the subject simultaneously with or sequentially to the first image,
an image combining unit that combines information contained in the first image and information contained in the second image to form a new image of the subject ;
The image combination unit is configured to identify, for each part of the subject, a predetermined area in the first image having positional information indicating the distance to the part based on the contrast level, set an area in the second image corresponding to the predetermined area in the identified predetermined area of the first image, and form a new first image . The incoherent digital holography imaging device described in claim 1, characterized in that the second imaging function unit is equipped with a shutter that blocks one of the two split light beams when obtaining the second image. The incoherent digital holography imaging device described in claim 1 or 2, characterized in that the first imaging function unit is configured to determine position information related to the first image, which represents the distance from the imaging surface to each part of the subject , based on the contrast level of the first image when the complex amplitude distribution of the obtained hologram image is back -propagated. The incoherent digital holography imaging device according to any one of claims 1 to 3, characterized in that the imaging optical system in the first imaging function unit comprises: a beam splitter that splits a beam from the subject into two beams; a plane mirror that receives one of the split beams and reflects it as a plane wave; a concave mirror that receives the other of the split beams and reflects it so as to converge as a spherical wave; an imaging element that obtains a hologram image by causing the plane wave from the plane mirror and the spherical wave from the concave mirror to interfere with each other; and a wavelength filter that narrows the wavelength range of the light wave that is incident on the imaging element, on a common optical path of the plane wave and the spherical wave. 5. The incoherent digital holography imaging device according to claim 4 , further comprising a phase shifting means for shifting either the plane mirror or the concave mirror by a predetermined phase in the optical axis direction. The incoherent digital holography imaging device described in claim 4 or 5, characterized in that the imaging optical system in the second imaging function unit is configured to be at least partially shared with the imaging optical system in the first imaging function unit, and is equipped with the light beam splitting means, the concave mirror that receives the other light beam split by the light beam splitting means and reflects it to converge as a spherical wave, and an imaging element that focuses the spherical wave from the concave mirror to obtain an image of the subject. the imaging optical system in the first imaging function unit and the imaging optical system in the second imaging function unit share an optical path in which a first polarizer is disposed up to a beam splitter that splits a beam from a subject, but each of the imaging optical systems is provided with an imaging element separate from the other;
The light beam splitting means is a spatial light modulator,
The incoherent digital holography imaging device according to any one of claims 1 to 3, characterized in that a wavelength filter and a second polarizer are arranged on a common optical path of the plane wave and the spherical wave from the beam splitting means to the imaging element of the first imaging function unit, so that a hologram image can be obtained at the imaging element of the first imaging function unit, and the spherical wave from the beam splitting means to the imaging element of the second imaging function unit is imaged on the imaging element of the second imaging function unit to obtain an image of the subject.