JP2023097562A - Incoherent digital holography imaging apparatus and imaging method - Google Patents

Abstract

To provide an incoherent digital holography imaging apparatus and an imaging method which can easily and highly accurately form a new color reconstruction image of a subject with the desired image quality by using a reconstruction image of the subject obtained by using the holography technology.SOLUTION: An incoherent digital holography imaging device comprises: a first imaging function unit which captures a hologram image with incoherent light from a subject 1 and forms a first image being a reconstruction color image of the subject 1; a second imaging function unit which captures a second image being a color image of the subject 1 by imaging a single light flux from the subject 1; and an image combination unit 14 which obtains position information of each portion of the subject 1 based on the first image, cuts out each portion of the second image corresponding to each portion of the first image based on the obtained position information, sets the position and forms a new first image.SELECTED DRAWING: Figure 1

Description

The present invention relates to an incoherent digital holography imaging apparatus and imaging method for acquiring digital holography using incoherent light with a short coherence length.

Digital holography is an imaging method that can acquire the complex amplitude (amplitude and phase distribution) of the subject, and has many advantages such as excellent spatial resolution and depth resolution, as well as being able to adjust the focus position by calculation. there is Among them, in recent years, the technology of incoherent digital holography, which can capture digital holograms using incoherent light such as sunlight, LEDs, and fluorescent light without using special light sources such as lasers, has progressed. application range is expanding.

In incoherent digital holography, an object beam is split into two beams and caused to self-interfere with each other to form a hologram (interference fringes) on an imaging surface.
In order to allow incoherent light to interfere, a wavelength filter (band-pass filter) is used to limit the wavelength width of the light source to several tens of nanometers or less (Non-Patent Document 1).
Thus, the resolution can be improved by limiting the wavelength width of the light source.

X. Quan, et al.”Three-dimensional stimulation and imaging-based functional optical microscopy of biological cells”, Optics Letters Vol. 43, No. 21, pp. 5447-5450 (2018)

However, today, even in the field of incoherent digital holography, there is a strong demand for colorization of images, and there is an urgent need to realize colorization, which has been considered difficult in this field.
In other words, in the field of incoherent digital holography, it is essential to narrow the wavelength width. Color imaging by coherent holography cannot be performed. On the other hand, incoherent holographic color photography that acquires information in the entire visible light range with a wavelength width of 10 nm, for example, requires about 40 bands, which is not realistic to implement.
Furthermore, in the field of incoherent digital holography, it is essential to narrow the wavelength width, so the signal value decreases relative to noise, resulting in a significant drop in image quality (S/N ratio). , and need to solve the problem.

The present invention has been made in view of the above circumstances, and uses a reconstructed image of a subject obtained using holography technology to create a new color reconstructed image of the subject with high accuracy and a high S/N ratio. It is an object of the present invention to provide an incoherent digital holography imaging device and an imaging method that can be easily formed by

The incoherent digital holography imaging device of the present invention comprises:
a first imaging function unit that captures a hologram image formed by mutually interfering incoherent light from an object divided into two systems and forms a first image that is a reconstructed image of the object; a second imaging function unit that forms a single light beam to obtain a second image, which is a color image of the subject, simultaneously or sequentially with the first image;
It is characterized by comprising an image combiner for combining the image information of the first image and the color image information of the second image to form a new reconstructed color image of the object.
Further, it is preferable that the image information of the first image is color image information.

Further, of the two imaging function units, at least the first imaging function unit selects and uses light in a part of the wavelength bands of the three primary color lights forming the first image. It is preferable to have optical wavelength band selection means.
Further, it is preferable that the optical wavelength band selection means is a bandpass filter.
Further, it is preferable that the width of the partial wavelength band is 50 nm or less.
In addition, it is preferable that the second imaging function unit includes a shutter for blocking one of the two systems of the divided incoherent light when obtaining the second image.

The image combination unit obtains position information of each part of the subject based on the first image, and obtains each part of the first image obtained by the second imaging function unit based on the obtained position information. It is preferable to have a function of forming a new first image by setting each part of the second image corresponding to .
Here, when the position information of each part of the subject is back-propagated up to a predetermined distance through the complex amplitude distribution of the obtained hologram image, the first imaging function unit obtains the contrast of the first image at the predetermined distance. preferably based on the height of the

Further, the imaging optical system in the first imaging function unit is divided into a beam splitting means for splitting the beam from the subject into two systems, and a plane mirror for receiving one of the split beams and reflecting a plane wave. a concave mirror that receives the other light beam and reflects it so as to converge the spherical wave; an imaging device that causes interference between the plane wave from the plane mirror and the spherical wave from the concave mirror to acquire a color hologram image; It is preferable to include a bandpass filter for narrowing the wavelength band of each of the three primary color lights to be incident on the imaging element, on the common optical path with the spherical wave.
Moreover, it is preferable to include phase shift means for moving either the plane mirror or the concave mirror by a predetermined phase in the optical axis direction.

Further, at least part of the imaging optical system in the second imaging function unit is shared with the imaging optical system in the first imaging function unit. the concave mirror that receives the other luminous flux and reflects it so as to converge the spherical wave; preferably.

Further, the imaging optical system in the first imaging function section and the imaging optical system in the second imaging function section are provided with a first polarizer up to the beam splitting means for splitting the beam from the subject. While the optical path is shared, the imaging elements are provided separately from each other,
the beam splitting means is a spatial light modulator,
The band-pass filter and the second polarizer are arranged on the common optical path of the plane wave and the spherical wave from the light beam splitting means to the imaging device of the first imaging function unit, and the color imaging device of the first imaging function unit a holographic image of the subject, and a color image of the subject is obtained by forming a spherical wave from the light beam splitting means to the imaging device of the second imaging function unit into an image on the imaging device of the second imaging function unit. It is preferably configured to obtain.

Further, the incoherent digital holography imaging method of the present invention includes:
a first imaging step of capturing a hologram image formed by mutually interfering incoherent light from an object divided into two systems to form a first image that is a reconstructed image of the object; simultaneously or sequentially performing a second imaging step of imaging one light flux to capture a second image, which is a color image of the subject;
The method is characterized by performing a step of forming a new color reconstructed image of the subject by combining image information of the first image and color image information of the second image.

The incoherent digital holography imaging apparatus and imaging method of the present invention achieve colorization while achieving the following effects in the field of incoherent digital holography where colorization of images is strongly desired.
That is, in the incoherent digital holography imaging technique, the obtained reconstructed image (hereinafter referred to as the first image) has position information and can construct a three-dimensional image. On the other hand, as described above, it is necessary to narrow the wavelength width for holographic imaging. Depending on the method, incoherent holographic color imaging cannot be performed. For example, about 40 bands are required to perform color imaging by incoherent holography, which acquires information in the entire visible light range with a wavelength width of 10 nm, and implementation is not realistic. Furthermore, it also has the characteristic of containing a lot of noise.
Therefore, the inventors of the present application have found that although it is not possible to obtain position information of each part, it is possible to obtain information in the entire visible light range, and a color image obtained by a normal imaging method with little influence of noise (hereinafter referred to as the second image) is acquired at the same time as the first image using a common optical system, and using the fact that the corresponding parts of the subject in both images can be easily determined, these two images are combined to obtain the desired image quality. It has occurred to me to create a color reconstructed image of a new object.

That is, to describe an example, based on a first image which is a reconstructed color image of the subject obtained using a hologram in the first imaging function unit, position information of each part of the subject is obtained, and the obtained position Based on the information, a new first image is formed by arranging the parts of the second image obtained by the second imaging function unit.

As a result, in the incoherent digital holography imaging apparatus and imaging method of the present invention, new color reproduction with a desired image quality (high S/N ratio) is achieved based on the color information of the obtained first and second images. A constituent image can be obtained. Moreover, since both images can be captured substantially simultaneously using a common optical system, a new color image with desired image quality can be obtained simply and with high precision.

To give a more specific example of the configuration for colorizing an image, in the incoherent digital holography imaging technology, at least the first imaging function unit selects , By providing an optical wavelength band selection means for selecting and outputting light in a narrow wavelength band with a predetermined width, it is possible to generate optical interference while improving resolution in each of the three primary color lights, and incoherent digital holography In the field, the colorization of the image can be realized well.
Further, by using the present invention, it is possible to construct a camera, a measuring device, a microscope, etc. that can accurately capture subject information (including color information).

1 is a conceptual diagram for explaining a holographic imaging/reproducing device according to Embodiment 1 of the present invention; FIG. A conceptual diagram for showing the wavelength band of light incident on each pixel of the imaging element accompanying the ON/OFF operation of the BPF of the holographic imaging and reproducing apparatus according to Embodiment 1 of the present invention ((A) is a Bayer array pixel (B) shows the wavelength band (I. holography) of each light incident on each pixel of the imaging device of the first imaging function unit, and each pixel of the imaging device of the second imaging function unit The wavelength band of each incident light (II. Imaging with a single light) is shown). FIG. 2 is a conceptual diagram for explaining a holographic imaging/reproducing device according to Embodiment 2 of the present invention; In the holography imaging and reproducing apparatus according to the second embodiment of the present invention, the pattern displayed on the SLM (the pattern (a) of the spherical wave imaged on the first image sensor 106a, the spherical wave imaged on the second image sensor 106b) and a pattern (c) obtained by synthesizing (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 uses both holographic imaging and imaging with a single light in the holographic imaging and reproducing apparatus according to Embodiment 2 of the present invention. . FIG. 10 is a conceptual diagram for explaining a method of photographing with an angle of view including three objects A, B, and C having different distances with the holography imaging and reproducing apparatus according to Embodiment 2 of the present invention. FIG. 7 is a conceptual diagram for explaining a method of forming a useful image from two types of images obtained by the two imaging methods shown in FIG. 6; FIG. 3 is a conceptual diagram for explaining a holographic imaging/reproducing device according to modification 1 of the present embodiment; FIG. 10 is a conceptual diagram for explaining a holographic imaging/reproducing device according to modification 2 of the present embodiment;

The incoherent digital holography imaging device and imaging method of the present invention will be described below using embodiments. In the present embodiment, the configuration of a holographic imaging/reproducing apparatus for imaging/reproducing a color image will be described as an example.
Further, the following description will first focus on the configuration of the optical system using Embodiments 1 and 2, and then, on the premise of the configuration of Embodiment 2, the reconstructed color of the subject using holography. An example of a technique for combining an image with a general subject color image using a single light will be described. After that, the optical system of the holographic imaging/reproducing apparatus will be supplemented with two modifications.

[Configuration of holographic imaging and reproducing device (mainly optical system)]
(Embodiment 1)
FIG. 1 shows the overall configuration of a holographic imaging/reproducing apparatus 50 according to Embodiment 1 of the present invention, mainly including an optical system.
The holographic imaging/reproducing device 50 constitutes an incoherent digital holographic imaging device using an optical system of a Michelson interferometer. The imaging and reproducing apparatus 50 has a holographic imaging function and a single light imaging function (imaging by a normal imaging system). image can be obtained.

First, photographing using holography will be described. Object light from subject 1 is converted into parallel light by lens 2 and enters beam splitter (B/S) 3. One of the split lights enters plane mirror 5 and is reflected as parallel light. of light enters the concave mirror 4 and is reflected as convergent light.
The two reflected lights enter the beam splitter (B/S) 3 again, and the former reflected light and the latter transmitted light travel in the direction of the single-plate color image sensor 6 and reach the imaging surface of the single-plate color image sensor 6. A hologram is formed on the top by self-interference.

Here, a phase shift method is used to obtain object light while avoiding superposition of direct light and conjugate light in in-line holography, and among them, a four-step phase shift method is used to facilitate calculation.
The plane mirror 5 is moved in the optical axis direction by a distance of 1/8, 2/8, and 3/8 times the wavelength from the reference position by the phase shift means (piezo element) 7 (the amount of light traveling toward the plane mirror 5 is increased). The optical path length is changed by 1/4, 2/4, and 3/4 times the wavelength), so that the phase is changed in four steps of 0, π/2, π, and 3π/2. there is

A shutter 8 capable of blocking light is shown on the plane mirror 5 on the side of the beam splitter (B/S) 3, and this functions (blocks light) when photographing with a single light (actual photographing), which will be described later. It is turned ON)), and in the case of photographing using holography, it is not made to function (it is not light-shielded (turned OFF)). As a result, only the light from the concave mirror 4 is used when photographing with a single light, while both the light from the concave mirror 4 and the light from the plane mirror 5 are used in the case of photographing using holography. It is possible to switch so that the plate color imaging device 6 is illuminated.
As the shutter 8, for example, a mechanical shutter, a liquid crystal shutter, or the like can be used.

In the single-chip color imaging device 6, pixels attached with on-chip color filters (OCF) of red (R), green (G), and blue (B) are arranged in a Bayer array or the like. , B is obtained. The OCF has a band of about 150 to 200 nm, and three filters of R, G, and B are set so as to cover the entire band of visible light.

On the other hand, on the beam splitter (B/S) 3 side of the single-chip color image pickup device 6, R, G, and B light beams are arranged so that even incoherent light (light with a short coherence length) can cause interference. A bandpass filter (BPF) 9 is arranged to narrow the wavelength band.
This BPF 9 can also be turned on/off (switched) in the same way as the shutter 8 described above. As the ON/OFF switching operation of the BPF 9, it is possible to employ a mechanism that mechanically inserts and withdraws the BPF 9, or a technique that uses a liquid crystal to change the transmission wavelength band. Note that this ON/OFF switching operation of the BPF 9 operates (turns ON) the BPF 9 when photographing with the single light. The BPF 9 is, for example, a multi-bandpass filter having peaks (three peaks) at the center wavelengths of the R, G, and B bands, and each of the three bands is set to several tens of nm or less.

Hologram image data is output from the single-plate color imaging device 6 to the subject image reconstruction means 11, and in the first image calculation section 12 in the subject image reconstruction means 11, the image plane is converted to the image plane using the four-step phase shift method. The amplitude and phase distributions of the imaging plane are calculated from the information of the four holograms formed in . Specifically, the amplitude/phase distribution at the object position can be reconstructed by performing back-propagating calculations from the imaging surface to the object surface.
At this time, by calculating the above amplitude/phase distribution for each pixel of R, G, and B, the amplitude/phase distribution at the object position can be reconstructed for each color light of R, G, and B. , a color image can be obtained from these three amplitude and phase distributions.
Instead of the 4-step phase-shift method, a 3-step, 2-step, or 5-step or more phase-shift method may be used, and a single imaging such as reference beam tilt, parallel phase shift, and random phase reference beam use may be used. (Exposure) may be used to acquire the complex amplitude (Refer to Ito and Shimobaba: “Introduction to Holography: 3D Images and 3D Measurements Using Computers”, 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 to change the phase of the light passing through the concave mirror 4 in a plurality of stages. In this case, when photographing with a single light, which will be described later, the movement of the phase shift means 7 may be stopped, or the concave mirror 4 may be moved by the phase shift means 7 as in the case of photographing using holography. You can shoot while In the latter case, it is possible to expect an effect that a focused image of the object 1 can be obtained over a wide depth range in photographing with a single light.

Next, imaging with a single light will be described. By operating the shutter 8 provided on the beam splitter (B/S) 3 side of the plane mirror 5 to turn on the light shielding function, the light passing through the plane mirror 5 is blocked, and only the light passing through the concave mirror 4 is isolated. It reaches the plate color imaging device 6 .
Also, the BPF 9 is set so as not to operate (turned off), whereby the single-chip color image sensor 6 functions as a normal single-chip color camera, and a color image (intensity distribution) of the subject 1 can be obtained. .
Alternatively, the shutter 8 may be arranged between the concave mirror 4 and the beam splitter (B/S) 3 so that only the light from the plane mirror 5 reaches the imaging surface. In this case, the lens 2 located behind the subject 1 can image the subject 1 in an imaging relationship with the imaging device 6 .

Further, from the single-plate color imaging device 6, image data by a single light is output to the object image reconstruction means 11, and in the second image storage section 13 in the object image reconstruction means 11, the single light image data is stored. A plurality of image data obtained by is stored.
After that, the amplitude/phase distribution data obtained by the calculation in the first image calculation section 12 and the image data stored in the second image storage section 13 are combined with the image combination section 14 in the subject image reconstruction means 11 . , and outputs the combined reconstructed image (new first image) to an external monitor 15 or the like as a subject image signal. The image combination processing performed in the image combination section 14 will be described later.
A holography reproduction device section 40 corresponding to the holography imaging device section 20 is constructed by the subject image reconstruction means 11, the monitor 15, and the like.

The apparatus of this embodiment alternately switches between the holography-based imaging function and the single-light imaging function. That is, in the first period, the shutter 8 is turned off, the BPF 9 is turned on, and a color hologram image of the object 1 corresponding to the phases of 0, π/2, π, and 3π/2 is photographed by the 4-step phase shift method, In the second period, the shutter 8 is turned on, the BPF 9 is turned off, and a color image of the subject 1 is acquired only by the light converged by the concave mirror 4 .

In photography using holography, the position of the single plate color image sensor 6 does not need to be near the position of the focal length of the concave mirror 4. It is desirable that the position of is near the position of the focal length of the concave mirror 4 .
In the configuration shown in FIG. 1, it is necessary to alternately perform two types of photography by switching the time. 4 (flat mirror 5 if light from plane mirror 5 is used for imaging with a single light).

FIG. 2 explains the wavelength band of light incident on each pixel of the single-chip color image pickup device 6 by the ON/OFF switching operation of the BPF 9 .
In shooting with a single light, normal broadband (for example, 150 to 200 nm width) R, G, and B color lights determined by the characteristics of the OCF are incident on the pixels for R, G, and B. On the other hand, in photographing using holography, since light that has passed through both the BPF 9 and the OCF is incident on each pixel, the pixels for R, G, and B have a bandwidth of each color light corresponding to R, G, and B. , and BPF 9, the light narrowed down to the band (for example, 10 nm width) is incident.
In order to cover the entire visible light range only by photographing using holography, for example, about 40 bands with a width of 10 nm are required, which is not realistic to implement.

In this embodiment, the color information of the entire visible light range is obtained by photographing with a single light, and then the complex amplitude (amplitude and phase distribution) of the subject 1 such as depth information is obtained by photographing using holography. ), and by using both single-light imaging and holographic imaging, it is possible to obtain highly accurate subject information.
For the latter, an OCF and a BPF 9 having three bands are used to acquire at least one complex amplitude (amplitude/phase distribution) from each of the R, G, and B bands. It is also possible to increase the number of bands to obtain a wider band complex amplitude (amplitude/phase distribution).

A monochrome image sensor is used instead of the single-plate color image sensor 6 having the configuration shown in FIG. B), or the broadband R, G, and B (hereinafter referred to as wR, wG, and wB) wavelength bands obtained by the OCF described above. Set to switch and sequentially perform holographic imaging using nR, nG, and nB, and single light imaging using wR, wG, and wB. The same effect as described above can also be obtained by

Further, in the holographic imaging and reproducing apparatus 50 shown in FIG. 1, a prism (B/S) 3 is provided between the subject 1 and the lens 2 to split the light from the subject 1 into three colored lights of R, G and B, A configuration of the device 50 shown in FIG. 1 may be provided for each color light. In this case, the image pickup device may be a monochrome image pickup device, and the BPF 9 may function to narrow the band of each color light of R, G, and B. FIG.

(Embodiment 2)
FIG. 3 shows the overall configuration of a holographic imaging/reproducing apparatus 150 according to Embodiment 2 of the present invention, mainly including an optical system. In this embodiment, there are many members whose functions are substantially the same as those in the first embodiment, so such members are given the reference numerals of the members in the first embodiment by adding 100. , the detailed description of which is omitted to avoid complication. Note that the holography reproducing device section 40 shown in Embodiment 1 has the same configuration as in this embodiment, so it is omitted from the drawings (the same is true in FIGS. 6, 8, and 9 described below) ). Further, in the present embodiment, when obtaining a hologram image, a single imaging operation using a reference beam tilt, a parallel phase shift, a random phase reference beam, etc., without using a phase shift method is used to obtain a complex amplitude. (exposure) is used (the same applies to modifications 1 and 2 described later). Of course, as in the first embodiment, the phase shift method may be used to obtain the complex amplitude.
As shown in FIG. 3, the feature of the holographic imaging/reproducing apparatus 150 according to the present embodiment is that dedicated imaging elements 106a and 106b are provided for imaging using holography and imaging with a single light, respectively. Therefore, it is possible to perform both photographing at the same time.

As shown in FIG. 3, the light from the subject 101 passes through the first polarizer 110a arranged behind the lens 102, which transmits linearly polarized light at an angle of 45 degrees, and is then split by the SLM 116 to obtain a first By allowing plane waves and spherical waves to reach the second single-plate color image pickup device 106a and only spherical waves to the second single-plate color image pickup device 106b, the former is used for photography using holography, and the latter is for photography using a single light. It is configured to take pictures. That is, the plane wave reaching the first single-plate color imaging device 106a is the vertical (or horizontal) linearly polarized component of the 45-degree linearly polarized incident light, and the spherical plane wave reaching the first single-plate color imaging device 106a. A wave is the horizontally (or vertically) linearly polarized component of the 45 degree linearly polarized incident light. The second polarizer 110b arranged on the SLM 116 side of the first single-plate color imaging device 106a aligns the polarization components of the respective lights, thereby causing the above two lights to interfere with each other, thereby obtaining a hologram. be done.

As a pattern displayed on the SLM 116, as shown in FIG. A pattern (c) or the like obtained by synthesizing the spherical waves of (a) and (b) can be applied.
This pattern has the effect of splitting the incident horizontal (or vertical) linearly polarized component into two spherical waves. It is also possible to use a pattern in which light that has reached even-numbered pixels in 106a forms an image on the second image sensor 106b. This division may be performed in units of blocks, each grouping a plurality of pixels, instead of in units of pixels.
As the SLM 116, not only a transmissive type but also a reflective type may be used. Moreover, it is possible to use not only a liquid crystal display device (LCD) but also a device such as a DMD.

In the configuration of this embodiment, the shutter 8 used in the above-described first embodiment becomes unnecessary, and the BPF 109 only needs to be arranged on the optical path between the SLM 116 and the first single-chip color image sensor 106a. , no ON/OFF switching operation is required. Since the shutter 8 and the switching operation and structure of the BPF 109 are not required in this way, the structure of the device is simple and the system can be made capable of speeding up the photographing.

The distance from the SLM 116 to the imaging elements 106a and 106b may be the same for the two imaging elements 106a and 106b, but the first imaging element 106a is the distance ( The second imaging element 106b may be arranged at different distances, such as the distance at which the images of the plane wave and the spherical wave have the same size, and the second image sensor 106b may be arranged at the position of the focal length.

Further, the holographic imaging/reproducing device 150 of the present embodiment can obtain the following effects substantially similar to those of the holographic imaging/reproducing device 50 of the first embodiment described above. That is, a monochrome image sensor may be used in place of the first single-plate color image sensor 106a shown in FIG. In this case, a BPF is also arranged on the SLM 116 side of the second single-plate color image pickup device 106b to synchronize the respective BPFs so that the image pickup operations of the image pickup devices 106a and 106b can be performed in a time-sharing manner, The BPF 109 arranged on the SLM 116 side of the first single-plate color image sensor 106a performs switching to narrow bands nR, nG, and nB as shown in FIG. The BPF arranged on the SLM 116 side of the second single-plate color image sensor 106b is used to perform switching to broadband wR, wG, and wB as shown in FIG. However, the same effect can be obtained.

Further, in substantially the same manner as the holographic imaging/reproducing device 50 of Embodiment 1 described above, in the holographic imaging/reproducing device 150 shown in FIG. may be divided into three colored lights of R, G, and B, and the configuration of the device 150 shown in FIG. 3 may be provided for each of the colored lights. In this case, each image pickup device is a monochrome image pickup device, and the BPF 109 is arranged only on the SLM 116 side of the first image pickup device (corresponding to the first single-plate color image pickup device 106a) for each color light. The BPF 109 may function to narrow the band of each color light.

[Method of combining images when obtaining a new reconstructed image]
Hereinafter, in the holographic imaging/reproducing device 150 according to the second embodiment, a configuration that uses both holographic imaging and single light imaging will be described in detail.
The configuration described below corresponds to the configuration of the image combining section 14 in the object image reconstructing means 11 described above.
Note that this simulation is explained using a monochrome image for the sake of simplicity of explanation. It suffices to perform it for light (channel).
In the following description, the term “object” may be used instead of the term “subject”.
FIG. 5 shows a general flow of imaging using holography and imaging with a single light. The upper portion schematically shows the processing flow of the output image for hologram formation and object image reconstruction in photographing using holography (I). The numerical parameters used are the numerical values shown in FIG. obtained.

Assuming that the four hologram image intensity distributions (I ₁ to I ₄ ) are obtained by changing the phase in four steps of 0, π/2, π, and 3π/2 by the 4-step phase shift method, the object A complex amplitude distribution (amplitude/phase distribution) u on the imaging plane of is represented by the following equation (1).
u=1/4×{(I ₁ −I ₃ )+i(I ₂ −I ₄ )} (i is an imaginary unit) (1)
A complex amplitude distribution (amplitude/phase distribution) at the object position is obtained by performing back propagation calculation on this complex amplitude distribution from the imaging plane to the object plane, and a reconstructed image of the subject 101 is obtained.

The lower half of FIG. 5 shows the image of the object in the single light shot (II). For example, an object color image (intensity distribution).

With the above method, in photographing with a single light, it is possible to obtain R, G, and B information over the entire visible light range. Complex amplitude distributions (amplitude and phase distributions) at various object positions can be acquired from each narrow band.

Since the calculations shown in FIG. 5 do not include the effects of noise, the difference between ((D) and (E)) between the two imaging techniques, holographic imaging I and single-light imaging II. There is no difference in image quality between each image), but in reality, photography using holography I is more likely to be affected by noise due to the decrease in the amount of light due to the limitation of the wavelength width.
That is, one of the main noises detected by the image sensor 106a is optical shot noise. S=√S, which is proportional to the square root of the number of photons.

For example, when photographing with a single light, the wavelength width is not limited by the BPF, but with a wavelength of 150 to 200 nm. Although it depends on the influence of , the amount of light in the latter is reduced to about one-tenth or less of that in the former, so the S/N ratio is also degraded.
Therefore, taking this difference in the amount of incident light into consideration, the S/N ratio of the above two photographing methods is worse in photographing using holography.

An example of a configuration according to an embodiment capable of obtaining useful images from two types of images obtained by the apparatus shown in FIG. 3 will be described below.
As shown in FIG. 6, photographing is performed at an angle of view including three objects A, B, and C at different distances, and images obtained by the two photographing methods at that time are shown in FIG. 6 uses the holographic imaging/reproducing device 150 of Embodiment 2, but for the sake of convenience, the corresponding members are denoted by 300 added to the reference numerals of the members shown in FIG. are doing.
A reconstructed image using holography (hereinafter referred to as the first image) has a lot of noise (represented by dots in objects A, B, and C in FIG. 7), but the distances a, b, and c of each object Corresponding backpropagation will increase the contrast of objects at that distance, thus providing information about the object at that distance. On the other hand, an image captured with a single light (hereinafter referred to as a second image) has little noise, but the relationship between distance and object is unknown. It is assumed here that the range of distances in which the object exists is within the range of the depth of field in photographing with a single light.

In the first image, in order to obtain an image with less noise for each part of the object, only high-contrast pixel areas corresponding to the parts of the first image in the second image are cut out. That is, a new first image is formed by specifying a high-contrast portion in the second image, setting each portion of the second image based on the position information of each corresponding portion of the corresponding first image. I'm trying
By doing so, it is possible to obtain a first image (reconstructed image) with little noise for the object positioned at each of the distances a, b, and c.
In FIG. 7, the in-focus portion (high-contrast portion) is extracted and used. It is also possible to create a blurred image on purpose by compositing the image including the blurred image.

By performing the above operations for each of the R, G, and B channels, a color image of an object at the distance of each object and with little noise can be obtained. Here, narrow-band signals (nR, nG, nB) for each of the R, G, and B colored lights obtained by holographic photography, and the original, for each of the R, G, and B colored lights Since it is thought that the broadband signals (wR, wG, and wB) of . In some cases, errors may occur when color information is acquired. This error can be reduced as the number of bands of signals acquired in a narrow band increases, so it is desirable to determine the number of bands according to the application.

In addition, as another method of utilization, it is known that holographic imaging contains information of higher spatial frequencies of an object than imaging with a single light. By performing FFT processing on the image obtained by the method, and reconstructing the image by synthesizing the high-frequency information obtained by the former imaging and the low-frequency information obtained by the latter imaging, the image quality and spatial An image with both frequency bands can be obtained.

Also, as another utilization method, use in obtaining moving images can be considered. That is, when the 4-step phase shift method is used in imaging using holography, it takes time to obtain four images and then to obtain a reconstructed image by calculation, which limits the improvement of the frame rate. case is conceivable.

On the other hand, when shooting with a single light, it is possible to shoot at a high frame rate up to the performance limit of the image sensor itself. Then, a synthesis method similar to that of FIG. 7 is used. That is, by cutting out only high-contrast pixel areas of the second image corresponding to the distance of each object in the reconstructed image obtained using holography, a color moving image of the object at the distance of each object is obtained. Obtainable.
Although distance information cannot be obtained with the highest frame rate time accuracy, it is useful for shooting subjects where, for example, the movement of an object changes drastically within the same distance, but the change in the depth direction of the object is small. , this embodiment is a particularly effective method.

As described above, in the imaging apparatus and imaging method of the present embodiment, the function of incoherent digital holography capable of acquiring the complex amplitude (amplitude phase distribution) of the subject while maintaining the function of imaging by a normal imaging system. can be realized, and can be applied to various devices such as cameras, measuring devices, microscopes, etc. that accurately capture information on an object.

Moreover, the incoherent digital holography imaging apparatus and imaging method according to the present invention are not limited to the above-described embodiments, and other various modifications are possible.
For example, the optical system may be modified as shown in FIGS. 8 and 9. FIG.
In addition, since many of the following modifications are similar in function to those of the members of the second embodiment, such members are denoted by the reference numerals of the members of the second embodiment, and 400 for the first modification. , and on the other hand, 500 is added to Modification 2, and a detailed description thereof is omitted to avoid complication.

(Modification 1)
As shown in FIG. 8, this modification is achieved by arranging a rotating polarizer 517 rotatable about the optical axis on the SLM 516 side of the single-chip color image pickup device 506 to perform holographic photography and single-lens imaging. It is equipped with a configuration for temporally switching between photographing with the light of . In photographing using holography, the rotating polarizer 517 arranged on the SLM 516 side of the single-chip color image sensor 506 performs the operation of aligning the polarization directions of the two light waves, as in the case of the second embodiment shown in FIG. In single-light photography, the rotating polarizer 517 is rotated to transmit only the spherical wave, which is the horizontally (or vertically) linearly polarized component.
In this case, it is important for the SLM 516 to generate a spherical wave that forms an image on the imaging plane in accordance with the imaging conditions using a single light. The BPF 509 performs an ON/OFF switching operation as in the case of the first embodiment. In the configuration of Modification 1, only one single-plate color image sensor 506 can be used, and the shutter used in Embodiment 1 is not required, so that the configuration can be made simpler.

(Modification 2)
As shown in FIG. 9, this modification has a configuration in which a polarizing beam splitter (PBS) 603 is used to split object light into S-polarized light and P-polarized light. The separated S-polarized light is imaged on the second image sensor 606b via the lens 602a for imaging with a single light, while the separated P-polarized light is captured by a half-wave plate 618 in a straight line at an angle of 45°. A configuration is adopted in which polarized light is transmitted, and holographic imaging is performed with the first image sensor 606a in the same manner as in Modification Mode 1 shown in FIG.
Note that the BPF 609 may always be set to the ON state. Compared with Modification 1, this Modification has the advantage of eliminating the loss of light quantity in the rotating polarizer 517 used in Modification 1 and efficiently utilizing the incident light. .

(Other Modifications)
As other modified aspects of the optical system, for example, in the first embodiment, an aspect using a Michelson type equal optical path length type optical system is shown, but for example, a Mach-Zehnder type or a detour optical path type is shown. It is also possible to use a Fizeau type optical system with equal optical path length.
In the above embodiment, the first image, which is the reconstructed image of the subject, is a color image, but it can also be a monochrome image. That is, in the incoherent digital holography imaging device and imaging method of the present invention, whether the first image is a color image or a monochrome image, and whether the result of combining with the second image is a color image. Just do it. However, the second image must be a color image.

1, 101, 401, 501, 601 subject 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
Single-plate color image sensor 7 Phase shift means (piezo element)
8 shutter 9, 109, 409, 509, 609 band pass filter (BPF)
11 subject image reconstructing means 12 first image calculation section 13 second image storage section 14 image combination section 15 monitor 20, 120, 420, 520, 620 holography imaging device section 40 holography reproduction device section 50, 150, 450, 550, 650 holographic imaging and reproducing device 110a, 110b, 410a, 410b, 510, 610 polarizer (first polarizer, second polarizer)
116, 416, 516, 616 SLMs
517 rotating polarizer 603 polarizing beam splitter (PBS)
618 half-wave plate

Claims (13)

a first imaging function unit that captures a hologram image formed by mutually interfering incoherent light from an object divided into two systems and forms a first image that is a reconstructed image of the object; a second imaging function unit that forms a single light beam to obtain a second image, which is a color image of the subject, simultaneously or sequentially with the first image;
Incoherent digital holography, comprising: an image combiner for combining image information of the first image and color image information of the second image to newly form a reconstructed color image of the subject. Imaging device. 2. The incoherent digital holography imaging apparatus according to claim 1, wherein the image information contained in said first image is color image information. At least the first imaging function unit of the two imaging function units selects and uses light in a partial wavelength band from wavelength bands of each of the three primary color lights forming the first image. 3. The incoherent digital holographic imaging device of claim 2, further comprising band selection means. 4. An incoherent digital holography imaging apparatus according to claim 3, wherein said optical wavelength band selection means is a bandpass filter. 5. The incoherent digital holography imaging apparatus according to claim 3, wherein the width of said partial wavelength band is 50 nm or less. 6. The method according to any one of claims 1 to 5, wherein the second imaging function unit includes a shutter for shielding one of the divided incoherent light beams of the two systems when obtaining the second image. The incoherent digital holography imaging device according to any one of the above. The image combination unit obtains position information of each part of the subject based on the first image, and obtains each part of the first image obtained by the second imaging function unit based on the obtained position information. 7. The incoherent digital according to any one of claims 1 to 6, characterized in that it has the function of positioning each part of the second image corresponding to the to form a new first image. Holographic imaging device. The first imaging function unit is configured to, when back-propagating the position information of each part of the subject through the complex amplitude distribution of the obtained hologram image up to a predetermined distance, obtain a high-contrast image of the first image at the predetermined distance. An incoherent digital holographic imaging device according to any one of claims 1 to 7, wherein the incoherent digital holographic imaging device is arranged to determine based on the distance. The imaging optical system in the first imaging function section includes a beam splitting means for splitting the beam from the subject into two systems, a plane mirror for receiving one of the split beams and reflecting a plane wave, and the other split beam. A concave mirror that reflects a light flux so as to converge the spherical wave, an imaging device that obtains a color hologram image by causing interference between the plane wave from the plane mirror and the spherical wave from the concave mirror, and the plane wave and the spherical wave. and a band-pass filter that narrows the wavelength band of each of the three primary color lights incident on the imaging device, on the common optical path with incoherent digital holography imager. 10. The incoherent digital holography imaging apparatus according to claim 9, further comprising phase shift means for moving either the plane mirror or the concave mirror by a predetermined phase in the optical axis direction. The imaging optical system in the second imaging function unit is configured such that at least a part of the imaging optical system in the first imaging function unit is shared with the imaging optical system in the first imaging function unit. the concave mirror that receives the other light beam and reflects the spherical wave so as to converge; 11. The incoherent digital holography imaging device according to claim 9 or 10, characterized in that: The imaging optical system in the first imaging function unit and the imaging optical system in the second imaging function unit are an optical path in which a first polarizer is arranged up to a beam splitting means for splitting a beam from a subject. are shared, while the imaging elements are provided separately from each other,
the beam splitting means is a spatial light modulator,
The band-pass filter and the second polarizer are arranged on the common optical path of the plane wave and the spherical wave from the light beam splitting means to the imaging device of the first imaging function unit, and the color imaging device of the first imaging function unit a holographic image of the subject, and a color image of the subject is obtained by forming a spherical wave from the light beam splitting means to the imaging device of the second imaging function unit into an image on the imaging device of the second imaging function unit. An incoherent digital holography imaging device according to any one of claims 4 to 11, characterized in that it is arranged to obtain. a first imaging step of capturing a hologram image formed by mutually interfering incoherent light from an object divided into two systems to form a first image that is a reconstructed image of the object; simultaneously or sequentially performing a second imaging step of imaging one light flux to capture a second image, which is a color image of the subject;
An incoherent digital holography imaging method, comprising: combining image information of the first image and color image information of the second image to form a new color reconstructed image of the subject.

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