Signal processing apparatus and imaging apparatus

Abstract

To provide a signal processing apparatus and an imaging apparatus that can eliminate artifact and obtain a high quality reconstructed image even when a premise of a linear shift invariant system does not hold.SOLUTION: A signal processing apparatus according to the present invention is a signal processing apparatus in an incoherent digital holography imaging apparatus, and is characterized to obtain a reconstructed image with artifact eliminated, by dividing a complex amplitude distribution extracted from a hologram of a subject imaged with the imaging apparatus by a calibration complex amplitude distribution and applying propagation calculation to the resulting complex amplitude distribution.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a signal processing device and an imaging device, and more particularly to a signal processing device and an imaging device in incoherent digital holography. [Background technology]

[0002] Incoherent Digital Holography (IDH) technology is characterized by its ability to capture holograms of objects using spatially incoherent lighting such as sunlight, general indoor lighting, and fluorescent light, and to obtain 3D information under natural light. Furthermore, IDH has superior spatial frequency characteristics to conventional cameras, making it a powerful technology capable of capturing high-definition images.

[0003] In incoherent digital holography, an object illuminated by an incoherent light source is regarded as a collection of tiny point light sources, and a hologram of the object is formed by adding together all the holograms of the self-interference of light emitted from each point light source. The theoretical formula for the hologram formation process in incoherent digital holography is derived on the premise of a linear shift-invariant system (a system in which the relationship between the input and output of the system does not change with spatial shift). Based on this theoretical formula, an imaging device for incoherent digital holography can reconstruct an image of the object by performing propagation calculations from the hologram (Patent Document 1, Non-Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6416270 [Patent Document 2] Patent No. 7348858 [Non-patent literature]

[0005] [Non-Patent Document 1] Joseph Rosen, et al., “Roadmap on Recent Progress in FINCH Technology”, Journal of Imaging, (2021), vol. 21, 197, [retrieved on 2024-02-16] Internet <URL: https: / / doi.org / 10.3390 / jimaging<7100197> [Non-Patent Document 2] Myung K. Kim, “Full color natural light holographic camera”, Optics Express, (2013), vol. 21, pp. 9636-9642. [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] However, as the aberration of the lens constituting the imaging device of incoherent digital holography increases, and as the arrangement error of each optical element increases, the premise of the linear shift-invariant system no longer holds, and a deviation occurs between the theoretical formula and the actual imaging device. Specifically, the farther the position of the point light source constituting the subject is from the optical axis of the imaging device in the in-plane direction, the more the shape of the hologram of that point light source is deformed. If the image is reconstructed by applying the conventional propagation calculation based on the linear shift-invariant system while the shape of this hologram is deformed, artifacts such as luminance unevenness will occur in the image of the subject, and the image quality will be significantly degraded.

[0007] Generally, when the aperture number of the lens constituting the imaging device is small, there is less aberration, and the premise of the linear shift-invariant system is valid, so the presence of artifacts cannot often be recognized in the reconstructed image. However, when the aperture number of the lens is increased to improve both the resolution and the field of view of the imaging device, the aberration of the lens tends to increase, and there is a problem that the image quality of the reconstructed image deteriorates so much that the presence of artifacts cannot be ignored.

[0008] Therefore, in view of the above-mentioned problems, an object of the present invention is to provide a signal processing device and an imaging device that can remove artifacts such as brightness unevenness and obtain a high-quality reconstructed image even when the assumption of a linear shift-invariant system does not hold in actual incoherent digital holography (for example, when there is aberration in the lens or when there is a placement error in the optical elements). [Means for solving the problem]

[0009] In order to solve the above problems, a signal processing device according to the present invention comprises: (1) A signal processing device for an incoherent digital holography imaging device, characterized in that a complex amplitude distribution extracted from a hologram of a subject captured by the imaging device is divided by a calibration complex amplitude distribution, and a propagation calculation is applied to the obtained complex amplitude distribution to obtain a reconstructed image from which artifacts have been removed.

[0010] (2) In the signal processing device of (1), it is further preferable that the calibration complex amplitude distribution is a complex amplitude distribution extracted from a hologram of a calibration subject having a uniform in-plane luminance distribution, captured by the imaging device.

[0011] (3) In the signal processing device of (1) or (2) above, it is further preferable that the calibration complex amplitude distribution is a complex amplitude distribution obtained by capturing an image of a hologram of a calibration object having a uniform in-plane luminance distribution using the imaging device, and combining an amplitude distribution extracted from the hologram of the calibration object with a phase distribution having a constant phase.

[0012] (4) In any of the signal processing devices (1) to (3) above, it is preferable that the imaging device further captures holograms of the subject at a plurality of wavelengths, and divides the complex amplitude distribution extracted from the hologram of each wavelength component by a calibration complex amplitude distribution corresponding to the wavelength component, thereby obtaining a reconstructed image from which artifacts have been removed for each wavelength component.

[0013] In order to solve the above problems, an imaging device according to the present invention comprises: (5) An imaging device comprising: an optical system that splits incoherent light into a first divided light and a second divided light, imparts different phase distributions to the complex amplitude distributions of the first divided light and the second divided light, and then causes the first divided light and the second divided light to interfere with each other to form a hologram and capture an image; and a signal processing device according to any one of (1) to (4) above.

[0014] (6) It is preferable that the imaging device of (5) above further comprises an optical system including a polarizer that converts incoherent light waves into linearly polarized light, a birefringent lens that gives phases of different focal lengths to the horizontally polarized component and the vertically polarized component of the light waves to convert them into the first split light and the second split light, a quarter-wave plate that converts the first split light and the second split light into circularly polarized light, and a polarizer array imaging element in which linear polarizers of 0°, 45°, 90°, and 135° are periodically mounted in each pixel for every four adjacent 2x2 pixels.

[0015] (7) It is preferable that the optical system of the imaging device of (5) above further comprises a polarizer that converts incoherent light waves into linearly polarized light, a birefringent lens that gives phases of different focal lengths to the horizontally polarized component and the vertically polarized component of the light waves to convert them into the first split light and the second split light, a quarter-wave plate that converts the first split light and the second split light into circularly polarized light, a checkered phase plate that splits the first split light and the second split light in multiple directions, respectively, and an area-divided polarizer that gives different phase differences to the first split light and the second split light for each area. [Effects of the Invention]

[0016] According to the signal processing device and imaging device of the present invention, even if there is aberration in the lens or placement error in the optical elements in an incoherent digital holography imaging device, artifacts such as brightness unevenness can be removed and a high-quality reconstructed image can be obtained. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a conceptual diagram of a signal processing device and an imaging device according to an embodiment of the present invention; [Figure 2] 1 is a flowchart illustrating an example of signal processing in the signal processing device of the present invention. [Figure 3] 1 is a diagram illustrating an example of the configuration of an imaging device for incoherent digital holography. [Figure 4] 10 is another example of the configuration of an imaging device for incoherent digital holography. [Figure 5A] 1 is an example of a hologram of a subject. [Figure 5B] 1 is an example of a complex amplitude distribution extracted from a hologram of a subject. [Figure 6A] An example of a white screen hologram. [Figure 6B] 1 is an example of a calibration complex amplitude distribution extracted from a white screen hologram. [Figure 7] 10 is an example of a complex amplitude distribution with artifacts removed. [Figure 8A] 10 is an example of a reconstructed image using a conventional signal processing device. [Figure 8B] 10 is an example of a reconstructed image by the signal processing device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0019] (Embodiment) 1 is a conceptual diagram of a signal processing device and an imaging device according to one embodiment of the present invention. The imaging device of the present invention includes an incoherent digital holography optical system and a signal processing device 50 that reconstructs an object from a hologram acquired by the optical system.

[0020] The optical system of the imaging device will be described. Incoherent light propagating from a subject is split into two optical paths, referred to as the first split light and the second split light. Different phases are imparted to each light wave. For example, two lenses 11 and 12 with different focal lengths are used to impart different spherical phases to the first split light and the second split light. These light waves are then combined and made to interfere on the imaging element 20, capturing a hologram of the subject. The captured hologram is output to the signal processing device 50.

[0021] The signal processing device 50 includes a complex amplitude distribution extraction unit 51, a calibration complex amplitude distribution 52, an artifact removal unit 53, and a reconstruction unit 54. Since the signal processing device 50 is generally realized by a computer and a program, the units 51 to 54 do not need to be separate and independent, and it is sufficient if the signal processing device 50 has the functions of the units 51 to 54.

[0022] 2 is a flowchart showing an example of signal processing applied to an imaged hologram in the signal processing device 50. Each step will be described.

[0023] Step 1 (S1): The signal processing device 50 acquires a hologram captured by an incoherent digital holography optical system. The acquired hologram is input to the complex amplitude distribution extraction unit 51 in the signal processing device 50.

[0024] Step 2 (S2): The complex amplitude distribution extraction unit 51 extracts the complex amplitude distribution from the acquired hologram. Specifically, the phase shift method or Fourier fringe analysis is performed on the captured hologram to extract the complex amplitude distribution.

[0025] When the phase shift method is applied, the phase of one of the first or second divided beams is shifted in the imaging device to capture multiple holograms with different phase shift amounts. For example, four holograms are captured, and a four-step phase shift method algorithm is applied to obtain the complex amplitude distribution. The intensity distributions of four holograms with phase shift amounts of 0, π / 2, π, and 3π / 2 are expressed as I0(x,y), I π / 2 (x,y), I π (x,y), I 3π / 2 If (x, y), information on the complex amplitude distribution can be obtained by the following equation (1).

[0026]

number

[0027] The complex amplitude distribution extracted from the hologram is output to the artifact removal unit 53 .

[0028] Step 3 (S3): The artifact removal unit 53 uses the complex amplitude distribution 52 for calibration to remove artifacts from the extracted complex amplitude distribution.

[0029] Here, it is desirable that the calibration complex amplitude distribution 52 be acquired in advance of signal processing and stored in a memory or the like within the signal processing device 50. Before capturing a hologram of a target object, the calibration complex amplitude distribution 52 can be extracted from a hologram captured by the same imaging device of a calibration object (e.g., a white screen or a display displaying a white image) that has a uniform in-plane luminance distribution and is positioned within the field of view of the imaging device at an arbitrary depth distance. Even if the object or the depth position of the object changes, the calibration complex amplitude distribution 52 does not need to be changed as long as the configuration of the imaging device remains the same. A characteristic of artifact removal in incoherent digital holography is that the calibration complex amplitude distribution is obtained using a calibration object that can be positioned at an arbitrary distance and has a uniform in-plane luminance distribution. Instead of directly obtaining the calibration complex amplitude distribution 52 using the imaging device, the calibration complex amplitude distribution may be estimated by simulating incoherent digital holography that reflects the configuration of the imaging device.

[0030] In addition, since the amplitude distribution has a large effect on the calibration process, the amplitude distribution a c Only (x,y) is stored, and this amplitude distribution a c (x, y) and the phase distribution φ with a constant phase distribution (the phase is an arbitrary constant value) c (x, y) may be combined to obtain the calibration complex amplitude distribution 52. By making the phase distribution constant, it is possible to speed up the calculation process, and also to reduce the amount of information to be stored when the calibration complex amplitude distribution 52 is stored inside the signal processing device 50.

[0031] The artifacts can be removed by dividing the extracted complex amplitude distribution by the calibration complex amplitude distribution 52 stored in the signal processing device 50, as shown in the following equation (2). This results in a complex amplitude distribution o(x, y) from which the artifacts have been removed. The complex amplitude distribution o(x, y) from which the artifacts have been removed is output to the reconstruction unit 54.

[0032]

number

[0033] Step 4 (S4): The reconstruction unit 54 performs reconstruction processing on the complex amplitude distribution o(x, y) from which the artifacts have been removed. In the reconstruction processing, propagation calculation is applied to the complex amplitude distribution o(x, y) based on the angular spectrum method or Fresnel diffraction to obtain a reconstructed image.

[0034] When using the angular spectrum method, the complex amplitude distribution U of the light propagating over the propagation distance z is z is obtained by the following equation (3).

[0035]

number

[0036] Here, FT[…] and FT -1 […] are the Fourier transform operator and the inverse Fourier transform operator, respectively. u and v are variables in the spatial frequency coordinate system. λ is the central wavelength of the light source. The complex amplitude distribution U z The reconstructed image is obtained as the amplitude distribution of

[0037] By the above signal processing, even if the imaging device has lens aberration or optical element placement error, a high-quality reconstructed image can be obtained from which artifacts such as brightness unevenness have been removed.

[0038] The above procedure is an explanation for the case of a single wavelength, but when capturing a hologram of a subject using multiple wavelengths (for example, capturing a color hologram using RGB wavelengths), it is desirable to acquire the complex amplitude distribution for calibration for each wavelength component. This is because aberrations and other factors differ for each wavelength, and artifacts such as brightness unevenness also change depending on the wavelength of the light source.

[0039] If the object hologram has multiple wavelength components, the imaging device captures the hologram of the calibration object using each wavelength in advance to obtain the calibration complex amplitude distribution for each wavelength component. The complex amplitude distribution extracted from the object hologram for a certain wavelength component is divided by the calibration complex amplitude distribution for the corresponding wavelength component. By applying propagation calculation to the obtained complex amplitude distribution, a reconstructed image from which artifacts have been removed can be obtained for each wavelength component. By combining the reconstructed images for each wavelength component, a high-quality color reconstructed image can be obtained, for example.

[0040] (Configuration of imaging device) A typical configuration of the optical system of an imaging device for incoherent digital holography will be described below, although the optical system for incoherent digital holography is not limited to this.

[0041] An example of the configuration of an imaging device for incoherent digital holography is shown in Figure 3. This imaging device is configured with an optical system based on a common-path interferometer that uses polarized light.

[0042] The imaging device includes a lens 13, a wavelength filter 14, a polarizer 15, a birefringent lens 16, a quarter-wave plate 17, a lens 18, and a polarization camera 21. Each component of the imaging device will be described below.

[0043] The object light from the subject is an incoherent light wave and enters the lens 13. Note that the object light may be reflected light, transmitted light, or light emitted from the subject.

[0044] The lens 13 collects the object light and makes it incident on the wavelength filter 14. The lens 13 has the same functions as a normal camera lens, such as adjusting the magnification and wide angle of the image. The subject can be placed at any position regardless of the focal position of the lens 13.

[0045] Wavelength filter 14 is a bandpass filter that transmits light waves of a predetermined wavelength width (for example, 3 nm to 20 nm) and improves the temporal coherence of the light waves. Note that narrowing the wavelength width improves image quality but reduces the amount of light in the image, so an appropriate wavelength filter 14 is selected depending on the desired image. The light waves that pass through wavelength filter 14 are incident on polarizer 15 of the interferometer.

[0046] The lens 13 and the wavelength filter 14 are not essential components of the imaging device, and the object light may be directly input to the polarizer 15 .

[0047] Polarizer (polarizing plate) 15 transmits only linearly polarized light in a specific direction. In this embodiment, the object light that passes through polarizer 15 becomes linearly polarized at 45° to the horizontal plane and enters birefringent lens 16. The horizontally polarized component and vertically polarized component of the light wave that has passed through polarizer 15 are used as the first split light and the second split light, respectively.

[0048] The birefringent lens 16 has birefringence and has different focal lengths for horizontally polarized light and vertically polarized light. Therefore, the birefringent lens 16 gives phases with different focal lengths to the horizontally polarized component and vertically polarized component of the light wave (the first split light and the second split light). The light that passes through the birefringent lens 16 is incident on the quarter-wave plate 17.

[0049] The quarter-wave plate 17 converts each of the two beams (the first split beam and the second split beam) that have passed through the birefringent lens 16 into left-handed and right-handed circularly polarized beams. The two circularly polarized beams have different focal length phases, which causes a slight optical path difference, resulting in interference.

[0050] The lens 18 focuses the two beams (the first and second split beams) onto the imaging surface of the polarizer array imaging element 21.

[0051] The polarizer array imaging element 21 has linear polarizers of 0°, 45°, 90°, and 135° periodically mounted on each of four adjacent 2 × 2 pixels. This polarizer array imaging element 21 is used to capture the interference light of the first divided light and the second divided light. By constructing an image from pixels with different polarization directions, four holograms with different phase shift amounts can be acquired all at once.

[0052] The signal processing device 50 may be the same as the signal processing device described in Fig. 1. The signal processing device 50 removes artifacts from the complex amplitude distribution extracted from the hologram by using a calibration complex amplitude distribution 52, and applies propagation calculation to the obtained complex amplitude distribution to obtain an artifact-free reconstructed image (reconstructed image).

[0053] Another example of the configuration of an imaging device for incoherent digital holography is shown in Figure 4. Like Figure 3, this imaging device is configured with an optical system based on a common optical path interferometer that uses polarized light, but it splits the light waves in multiple directions along the way and simultaneously generates multiple holograms with different phase shifts.

[0054] This imaging device is the same as the imaging device in Figure 3 in that it includes a lens 13, a wavelength filter 14, a polarizer 15, a birefringent lens 16, and a quarter-wave plate 17, but uses a checkered phase plate 30 and an area-divided polarizer 40 instead of the polarizer array imaging element 21. The imaging element 22 is a normal imaging element. Each component of the imaging device will be described below, but the description of the components common to Figure 3 will be simplified.

[0055] The object light from the subject is an incoherent light wave that enters lens 13. Lens 13 focuses the object light, and wavelength filter 14 transmits light waves with a predetermined wavelength range. Polarizer 15 converts the object light into linearly polarized light at an angle of 45° to the horizontal plane. The horizontally polarized component and vertically polarized component of the light wave become the first and second split lights, respectively.

[0056] The birefringent lens 16 gives phases with different focal lengths to the horizontally polarized component and vertically polarized component of the light wave (the first split light and the second split light). The quarter-wave plate 17 converts the first split light and the second split light that have passed through the birefringent lens 16 into left-handed and right-handed circularly polarized light, respectively.

[0057] The checkered phase plate 30 is an optical element in which, for example, two types of phase objects (objects that change only the phase of light) are arranged in a checkered pattern (see Patent Document 2). The checkered phase plate 30 splits the first and second split light, which are left-handed and right-handed circularly polarized light, into multiple directions (four directions in this embodiment), and each of the split light beams is incident on the area-division polarizer 40.

[0058] The area-divided polarizer 40 is composed of four types (four regions) of linear polarizers with transmission axes at 0°, 45°, 90°, and 135°. When the first and second divided lights, which are branched in four directions, are incident on each region of the area-divided polarizer 40, the area-divided polarizer 40 imparts a different phase difference to the first and second divided lights for each region. As a result, different phase shift amounts of 0, π / 2, π, and 3π / 2 [rad] are imparted to each pair of linearly polarized light for each region, depending on the angle of the transmission axis of the linear polarizer.

[0059] By capturing an image of a set of linearly polarized light beams transmitted through the area-divided polarizer 40 with the image sensor 22, four holograms with different amounts of phase shift can be acquired all at once.

[0060] Comparing the optical systems of FIG. 3 and FIG. 4, the optical system of FIG. 3 makes it easier to expand the field of view, and the optical system of FIG. 4 makes it easier to improve the resolution.

[0061] 1 and 3, the signal processing device 50 extracts the complex amplitude distribution of the object on the imaging plane from the four acquired holograms using a phase shift method or the like. Furthermore, the signal processing device 50 removes artifacts from the extracted complex amplitude distribution using a calibration complex amplitude distribution 52, and applies propagation calculation to the obtained complex amplitude distribution to obtain an artifact-free reconstructed image (reconstructed image).

[0062] The imaging devices to which the signal processing device 50 of the present invention can be applied are not limited to those described above, but can be applied to all incoherent digital holography that forms holograms through self-interference, and can also be used in cases such as Michael interferometers and Mach-Zehnder interferometers. However, the calibration complex amplitude distribution of the present invention, which uses an object with a uniform in-plane luminance distribution, does not function in digital holography imaging devices that use a laser light source as illumination light.

[0063] (Example and verification of effects) The effects of the present invention were verified based on the example using the incoherent digital holography imaging device shown in Figure 3. The focal lengths of lenses 13 and 18 were 750 mm and 40 mm, respectively. The focal length of birefringent lens 16 was 5500 mm for one of the split beams (and infinite for the other split beam). The polarizer array imaging element 21 had a pixel pitch of 3.45 μm and 2448 × 2048 pixels, and the 2048 × 2048 area at the center of the sensor was used for imaging the hologram. To enhance temporal coherence and form a high-contrast hologram, the wavelength filter 14 was a bandpass filter with a center wavelength of 633 nm and a wavelength width of 10 nm.

[0064] Figure 5A shows the result of capturing a hologram of a mannequin using this imaging device. Figure 5B shows the complex amplitude distribution extracted from the hologram. As can be seen from the complex amplitude distribution in Figure 5B, concentric brightness variations occur in the amplitude distribution. Concentric phase variations also occur in the phase distribution. These artifacts arise from the fact that the imaging device does not constitute a linear shift-invariant system.

[0065] To correct this, a calibration complex amplitude distribution was obtained in advance. Figure 6A shows a calibration hologram acquired using the same imaging device and a white screen as the object. Figure 6B shows a calibration complex amplitude distribution 52 extracted from the calibration hologram. Because the object has a uniform luminance distribution, ideally, both the amplitude distribution and phase distribution in Figure 6B should be uniform. However, because a linear shift-invariant system does not exist, luminance and phase unevenness occur. Note that this unevenness does not depend on the placement distance of the white screen in the depth direction and always remains the same distribution. Therefore, the placement distance of the white screen is arbitrary.

[0066] Based on the above-mentioned equation (2), the complex amplitude distribution in Fig. 5B was divided by the calibration complex amplitude distribution in Fig. 6B. Fig. 7 shows the complex amplitude distribution obtained as a result of equation (2). Compared to the complex amplitude distribution in Fig. 5B, in which artifacts occur, it can be seen that there are no concentric circular artifacts in Fig. 7.

[0067] Figure 8A shows a reconstructed image obtained by applying propagation calculation to the complex amplitude distribution in Figure 5B and focusing on the mannequin's face. In other words, Figure 8A shows a reconstructed image obtained by a conventional signal processing device, i.e., by applying a conventional incoherent digital holography reconstruction method. It can be seen that artifacts remain even after applying propagation calculation with the conventional reconstruction method.

[0068] Fig. 8B shows a reconstructed image obtained by removing artifacts using the signal processing device of the present invention through the signal processing of Fig. 2. It can be seen that the artifacts have been removed and a high-quality image of the subject has been obtained.

[0069] In addition, the signal processing device 50 and the imaging device of the present invention not only remove artifacts, but also correct non-uniformity in light-receiving sensitivity among the pixels of the imaging elements constituting the imaging device, even if such non-uniformity exists, thereby obtaining a high-quality reconstructed image.

[0070] In the above embodiments, the configurations and operations of the signal processing device and the imaging device have been described, but the present invention is not limited to this and may be configured as a signal processing method characterized by obtaining a reconstructed image free of artifacts. That is, the present invention may be configured as a signal processing method including the steps of acquiring a hologram, extracting a complex amplitude distribution from the hologram, removing artifacts from the extracted complex amplitude distribution using a complex amplitude distribution for calibration, and performing reconstruction processing on the complex amplitude distribution from which the artifacts have been removed, according to the flowchart of Fig. 2.

[0071] Although the above-described embodiments have been described as typical examples, it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications or alterations are possible without departing from the scope of the claims. For example, the functions included in each block, step, etc. described in the embodiments can be rearranged so as not to be logically inconsistent, and multiple constituent blocks, steps, etc. can be combined or divided into one. [Explanation of symbols]

[0072] 11~13 Lens 14 wavelength filters 15 Polarizer 16 Birefringent Lens 17 1 / 4 wave plate 18 Lenses 20 Image sensor 21 Polarization Camera 22 Image sensor 30 Checkered phase plate 40 region segmentation polarizer 50 Signal Processing Device 51 Complex amplitude distribution extraction unit 52 Complex amplitude distribution for calibration 53 Artifact Removal Unit 54 Reconstruction part

Claims

1. A signal processing device in an incoherent digital holography imaging device, comprising: A signal processing device characterized in that a complex amplitude distribution extracted from a hologram of a subject captured by the imaging device is divided by a calibration complex amplitude distribution, and a propagation calculation is applied to the obtained complex amplitude distribution, thereby obtaining a reconstructed image from which artifacts have been removed.

2. 2. The signal processing device according to claim 1, a signal processing device, characterized in that the calibration complex amplitude distribution is a complex amplitude distribution extracted from a hologram of a calibration object having a uniform in-plane luminance distribution, the hologram being captured by the imaging device.

3. 2. The signal processing device according to claim 1, a signal processing device characterized in that the calibration complex amplitude distribution is a complex amplitude distribution obtained by capturing an image of a hologram of a calibration object having a uniform in-plane luminance distribution with the imaging device, and combining an amplitude distribution extracted from the hologram of the calibration object with a phase distribution having a constant phase.

4. 2. The signal processing device according to claim 1, the imaging device captures a hologram of a subject at a plurality of wavelengths; A signal processing device comprising: a signal processing unit for dividing a complex amplitude distribution extracted from a hologram of each wavelength component by a calibration complex amplitude distribution corresponding to the wavelength component, and obtaining a reconstructed image from which artifacts have been removed for each wavelength component.

5. an optical system that splits incoherent light into first and second split lights, imparts different phase distributions to the complex amplitude distributions of the first and second split lights, and then causes the first and second split lights to interfere with each other to form a hologram and capture an image; A signal processing device according to any one of claims 1 to 4; An imaging device comprising:

6. 6. The imaging device according to claim 5, The optical system comprises: A polarizer that linearly polarizes incoherent light waves; a birefringent lens that gives phases of different focal lengths to the horizontally polarized component and the vertically polarized component of the light wave to form the first split light and the second split light; a quarter-wave plate that converts the first split light and the second split light into circularly polarized light; a polarizer array imaging element in which linear polarizers of 0°, 45°, 90°, and 135° are periodically mounted on each pixel for every four adjacent 2×2 pixels; An imaging device comprising:

7. 6. The imaging device according to claim 5, The optical system comprises: A polarizer that linearly polarizes incoherent light waves; a birefringent lens that gives phases of different focal lengths to the horizontally polarized component and the vertically polarized component of the light wave to form the first split light and the second split light; a quarter-wave plate that converts the first split light and the second split light into circularly polarized light; a checkered phase plate that splits the first divided light beam and the second divided light beam in a plurality of directions; an area-divided polarizer that gives different phase differences to the first divided light and the second divided light for each area; An imaging device comprising:

Images