Incoherent Digital Holography Imaging System

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

Technical Field

[0004]

[0001] The present invention relates to an incoherent digital holography imaging apparatus that acquires digital holography using incoherent light with a short coherence distance. Place Related thereto.

Background Art

[0002] Digital holography is a photography method capable of acquiring the complex amplitude (amplitude and phase distribution) of a subject, and has many advantages such as excellent spatial resolution and depth resolution, and the ability to adjust the focus position by calculation. Among them, in recent years, the technology of incoherent digital holography, which can capture a digital hologram using incoherent light such as sunlight, LED, and fluorescence without using a special light source such as a laser, has advanced, and thereby the application range of holography has been expanded.

[0003] In incoherent digital holography, object light is divided into two systems, and they are self-interfered with each other to form a hologram (interference fringes) on the imaging surface. And in order to interfere incoherent light, the wavelength width of the light source is restricted to several tens of nanometers or less by a wavelength filter (band-pass filter) (Non-Patent Document 1). Thus, the resolution can be improved by restricting the wavelength width of the light source.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

[0005] However, today, there is a strong demand for colorization of images in the field of incoherent digital holography, and it is urgent to achieve colorization, which has been considered difficult in this field. In other words, in the field of incoherent digital holography, narrowing the wavelength range is essential. Therefore, the three-band imaging method used with conventional image sensors, employing R, G, and B color filters, cannot be used to perform incoherent holographic color imaging. On the other hand, to perform incoherent holographic color imaging that acquires information across the entire visible light spectrum with a wavelength range of, for example, 10 nm, approximately 40 bands would be required, making implementation impractical. Furthermore, in the field of incoherent digital holography, narrowing the wavelength is essential, which means that the signal value decreases relative to the noise, resulting in a significant decrease in image quality (S / N ratio). This problem needs to be solved.

[0006] The present invention has been made in view of the above circumstances, and is an incoherent digital holography imaging device that can easily form a new color reconstructed image of a subject with high accuracy and a high signal-to-noise ratio using a reconstructed image of the subject obtained using holography technology. Place The purpose is to provide it. [Means for solving the problem]

[0007] The incoherent digital holography imaging apparatus of the present invention is Incident from the imaging lens, A first imaging function unit captures a hologram image formed by interfering incoherent light from a subject divided into two systems, and forms a first image which is a reconstructed image of the subject. The light is incident from the imaging lens,It has a second imaging function unit that forms an image of a single beam of light from a subject and obtains a second image, which is a color image of the subject, simultaneously with or sequentially with the first image. The system includes an image combination unit that combines the image information of the first image and the color image information of the second image to form a new color reconstructed image of the subject. 、 The image information contained in the aforementioned first image is color image information, Of the two imaging function units, at least the first imaging function unit is equipped with an optical wavelength band selection means that selects and uses light from a portion of the wavelength bands of each of the three primary color lights that form the first image. The image combination unit is configured to identify a predetermined area based on the contrast level within the first image, which has positional information representing the distance to each part of the subject, and to set an area in the second image corresponding to the identified predetermined area within the first image, thereby forming a new first image. The first imaging function unit is configured to determine positional information representing 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 backpropagated to a predetermined distance. It is characterized by ru.

[0008] Ma Furthermore, it is preferable that the optical wavelength band selection means is a bandpass filter. Furthermore, it is preferable that the width of the aforementioned wavelength band is 50 nm or less. Furthermore, it is preferable that the second imaging function unit includes a shutter that blocks one of the two divided incoherent light systems when obtaining the second image.

[0010] Furthermore, the imaging optical system in the first imaging function unit receives the light beam from the subject. The aforementioned Preferably, the system includes: a light beam splitting means that divides the light beam into two systems; a plane mirror that receives one of the split light beams and reflects a plane wave; a concave mirror that receives the other split light beam and reflects it in a way that converges a spherical wave; an image sensor that acquires a color hologram image by interfering the plane wave from the plane mirror with the spherical wave from the concave mirror; and a bandpass filter on the common optical path between the plane wave and the spherical wave that narrows the wavelength band of each of the three primary color lights that are incident on the image sensor. Furthermore, it is preferable to include a phase shifting means for moving either the plane mirror or the concave mirror by a predetermined phase in the optical axis direction.

[0011] Furthermore, it is preferable that the imaging optical system in the second imaging function unit is configured to be shared with the imaging optical system in the first imaging function unit in at least a portion of it, and 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 focus a spherical wave, and the image sensor that forms an image of the spherical wave from the concave mirror to acquire a color image of the subject.

[0012] Furthermore, the imaging optical system in the first imaging function unit and the imaging optical system in the second imaging function unit share a common optical path through which the first polarizer is arranged, leading to the light beam splitting means that splits the light beam from the subject, while the image sensors are provided separately from each other. The aforementioned light beam splitting means is a spatial light modulator, Preferably, the bandpass filter and the second polarizer are arranged on the common optical path of the plane wave and spherical wave from the light beam splitting means to the image sensor of the first imaging function unit so that a color hologram image can be obtained at the image sensor of the first imaging function unit, and the spherical wave from the light beam splitting means to the image sensor of the second imaging function unit is imaged at the image sensor of the second imaging function unit so that a color image of the subject can be obtained. [Effects of the Invention]

[0014] The present invention's incoherent digital holography imaging device Place This technology achieves colorization in the field of incoherent digital holography, where there is a strong demand for image colorization, while also achieving the following effects. That is, in incoherent digital holographic imaging technology, the obtained reconstructed image (hereinafter referred to as the first image) has position information, and a three-dimensional image can be constructed. On the other hand, as described above, since it is necessary to narrow the wavelength width for holographic imaging, color imaging by incoherent holography cannot be performed by the conventional three-band imaging method using R, G, and B color filters in an image sensor. For example, to perform color imaging by incoherent holography that acquires information over the entire visible light range with a wavelength width of 10 nm, about 40 bands are required, and it is not realistic to implement. Furthermore, it also has the characteristic of containing a lot of noise. Therefore, the inventor of the present application can obtain a color image (hereinafter referred to as the second image) obtained by a normal imaging method that cannot obtain the position information of each part but can obtain information over the entire visible light range and is also less affected by noise, and uses a common optical system to obtain the first image simultaneously. Utilizing the fact that corresponding parts of the subject in both images can be easily discriminated, the inventor came up with the idea of combining these two images to form a new color reconstructed image of the subject with a desired image quality.

[0015] That is, to describe an example, based on the first image, which is a reconstructed color image of the subject obtained using a hologram in the first imaging functional unit, the position information of each part of the subject is obtained, and based on the obtained position information, each part of the second image obtained by the second imaging functional unit is arranged to form a new first image.

[0016] Thereby, in the incoherent digital holographic imaging device of the present invention Place a new color reconstructed image with a desired image quality (high S / N ratio) can be obtained based on the color information of the obtained first image and second image. Moreover, since both images can be taken substantially simultaneously using a common optical system, a new color image with a desired image quality can be obtained simply and with high precision.

[0017] Regarding the configuration for colorizing an image, for a more specific example, in incoherent digital holography imaging technology, at least the first imaging function unit includes a light wavelength band selection means for selecting and outputting light in a narrow wavelength band of a predetermined width from each of the wavelength bands of the three primary color lights that form the first image. By doing so, it is possible to cause optical interference while improving the resolution in each of the three primary color lights, and in the field of incoherent digital holography, the colorization of the image can be satisfactorily realized. Moreover, by utilizing this invention, it is possible to construct a camera, a measuring device, and further a microscope or the like that accurately captures subject information (including color information).

Brief Description of the Drawings

[0018] [Figure 1] It is a conceptual diagram for explaining a holographic imaging and playback device according to Embodiment 1 of the present invention. [Figure 2] It is a conceptual diagram for showing the wavelength band of light incident on each pixel of an image pickup device accompanying the ON / OFF operation of the BPF of the holographic imaging and playback device according to Embodiment 1 of the present invention ((A) shows a pixel array of a Bayer array, and (B) shows the wavelength band of each light incident on each pixel of the image pickup device of the first imaging function unit (I. Holography), and the wavelength band of each light incident on each pixel of the image pickup device of the second imaging function unit (II. Imaging by a single light)). [Figure 3] It is a conceptual diagram for explaining a holographic imaging and playback device according to Embodiment 2 of the present invention. [Figure 4] In the holographic imaging and playback device according to Embodiment 2 of the present invention, it is a pattern to be displayed on the SLM (pattern (a) of a spherical wave that forms an image on the first image pickup device 106a, pattern (b) of a spherical wave that forms an image on the second image pickup device 106b, and pattern (c) obtained by synthesizing (a) and (b)). [Figure 5] It 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 imaging by a single light in the holographic imaging and playback device according to Embodiment 2 of the present invention. [Figure 6] This is a conceptual diagram illustrating a method for capturing images with a field of view that includes three objects A, B, and C at different distances from each other, using a holographic imaging and playback device according to Embodiment 2 of the present invention. [Figure 7] This is a conceptual diagram illustrating a method for forming a useful image from two types of images obtained using the two imaging techniques shown in Figure 6. [Figure 8] This is a conceptual diagram illustrating a holographic imaging and playback device according to Modified Embodiment 1 of this model. [Figure 9] This is a conceptual diagram illustrating a holographic imaging and playback device according to a modified version 2 of this embodiment. [Modes for carrying out the invention]

[0019] The following describes the incoherent digital holography imaging device of the present invention. Place This will be explained using an embodiment. In this embodiment, the configuration of a holographic imaging and reproduction device that captures and reproduces color images will be used as an example. Furthermore, the following explanation will first describe the configuration of the optical system using Embodiments 1 and 2, and then, based on the configuration of Embodiment 2, describe an example of a method for combining a reconstructed color image of a subject using holography with a general color image of a subject using a single light source. Subsequently, supplementary explanations will be given regarding the optical system of the holographic imaging and reproduction device described above, citing two types of modifications.

[0020] [Configuration of a holographic imaging and playback system (primarily focusing on the optical system)] (Embodiment 1) Figure 1 shows the overall configuration, mainly the optical system, of the holographic imaging and playback apparatus 50 according to Embodiment 1 of the present invention. This holographic imaging and playback device 50 is an incoherent digital holographic imaging device that uses the optical system of a Michelson interferometer. This imaging and playback device 50 has a function for imaging using holography and a function for imaging with a single light source (imaging with a normal imaging system), and by using both functions, it is possible to obtain incoherent digital holographic images with low noise.

[0021] First, let's explain holographic photography. Object light from subject 1 is converted into parallel light by lens 2 and enters beam splitter (B / S) 3. One of the split beams enters plane mirror 5 and is reflected as parallel light, while the other split beam enters concave mirror 4 and is reflected as focused light. The two reflected beams of light enter the beam splitter (B / S) 3 again, and the reflected light from the former and the transmitted light from the latter travel towards the single-chip color image sensor 6, forming a hologram on the imaging surface of the single-chip color image sensor 6 through self-interference.

[0022] Here, to acquire object light while avoiding the superposition of direct and conjugate light in in-line holography, the phase shift method is used, and among these, the 4-step phase shift method is employed to simplify calculations. The plane mirror 5 is configured to change its phase in four stages: 0, π / 2, π, and 3π / 2, by moving in the optical axis direction from the reference position by a distance of 1 / 8, 2 / 8, and 3 / 8 times the wavelength using a phase shifting means (piezo element) 7 (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).

[0023] A light-shielding shutter 8 is shown on the beam splitter (B / S) 3 side of the plane mirror 5. This shutter is activated (turned ON) when performing single-light imaging (main imaging), as described later, but is not activated (turned OFF) when performing holographic imaging. This allows switching between illuminating the single-chip color image sensor 6 with only light from the concave mirror 4 when performing single-light imaging, and illuminating the single-chip color image sensor 6 with both light from the concave mirror 4 and light from the plane mirror 5 when performing holographic imaging. For this shutter 8, for example, a mechanical shutter or an LCD shutter can be used.

[0024] The single-chip color image sensor 6 has pixels equipped with red (R), green (G), and blue (B) on-chip color filters (OCF) arranged in a Bayer array or similar configuration, and each pixel is configured to acquire color information from either R, G, or B. The OCF bandwidth is approximately 150-200 nm, and the three types of filters (R, G, and B) are configured to cover the entire visible light spectrum.

[0025] On the other hand, a bandpass filter (BPF) 9 is positioned on the beam splitter (B / S) 3 side of the single-chip color image sensor 6 to narrow the wavelength bands of each color light, R, G, and B, so that interference can be caused even by incoherent light (light with a short coherence distance). Like the shutter 8 mentioned above, the BPF9 can also be switched ON / OFF. The ON / OFF switching operation of the BPF9 can employ various methods, such as a mechanical extension / retraction mechanism or a method using liquid crystal to change the transmission wavelength band. When performing photography with a single light source, the BPF9 is activated (turned ON). The BPF9 is a multi-bandpass filter, for example, having peaks at the center wavelengths of each of the R, G, and B bands (having three peaks), with each of the three bands set to be less than a few tens of nanometers.

[0026] Holographic image data is output from the single-chip color image sensor 6 to the subject image reconstruction means 11. In the first image processing unit 12 within the subject image reconstruction means 11, the amplitude and phase distribution of the imaging surface is calculated from the four holographic information images formed on the imaging surface using a four-step phase shift method. Specifically, the amplitude and phase distribution at the subject position can be reconstructed by performing calculations that propagate back from the imaging surface to the subject surface. In this process, by calculating the amplitude and phase distribution for each R, G, and B pixel, the amplitude and phase distribution at the object position can be reconstructed for each of the R, G, and B colored lights. Therefore, a color image can be obtained using these three amplitude and phase distributions. Instead of the four-step phase shift method described above, a three-step, two-step, or five-step or more phase shift method may be used, or a method that acquires the complex amplitude in a single imaging (exposure) may be used, such as using reference light tilt, parallel phase shift, or random phase reference light (see Ito and Shimobaba: "Introduction to Holography: Computer-Assisted 3D Imagery and Measurement", Kodansha, pp. 119-125).

[0027] 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 multiple stages, as described above. In this case, when shooting with a single light source as described later, the movement by the phase shift means 7 may be stopped before shooting, or the concave mirror 4 may be moved by the phase shift means 7 while shooting, similar to when shooting with holography. In the latter case, the effect of obtaining a focused image over a wide depth range of the subject 1 when shooting with a single light source can also be expected.

[0028] Next, we will explain imaging using a single light source. By activating the shutter 8 located on the beam splitter (B / S) 3 side of the plane mirror 5, the light-shielding function is turned on, blocking the light passing through the plane mirror 5, and only the light passing through the concave mirror 4 reaches the single-chip color image sensor 6. Furthermore, the BPF9 is set to be disabled (turned off), allowing the single-chip color image sensor 6 to function as a normal single-chip color camera and obtain a color image (intensity distribution) of subject 1. Alternatively, the shutter 8 may be placed between the concave mirror 4 and the beam splitter (B / S) 3 so that only 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 that is in an imaging relationship with the image sensor 6.

[0029] Furthermore, the single-chip color image sensor 6 outputs image data obtained from a single light source to the subject image reconstruction means 11, and the second image storage unit 13 within the subject image reconstruction means 11 stores multiple image data obtained from a single light source. Subsequently, the amplitude and phase distribution data obtained by the calculations in the first image processing 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 reconstruction means 11, and this combined reconstructed image (new first image) is output as a subject image signal to an external monitor 15 or the like. The image combination processing performed in the image combination unit 14 will be described later. Furthermore, the subject image reconstruction means 11 and the monitor 15, etc., are used to construct a holography playback device 40 corresponding to the holography imaging device 20.

[0030] In the apparatus of this embodiment, the above-mentioned holographic shooting function and the single-light shooting function are alternately switched. Specifically, in the first period, the shutter 8 is turned off and the BPF 9 is turned on, and a color hologram image of subject 1 corresponding to phases 0, π / 2, π, and 3π / 2 is captured using a 4-step phase shift method. In the second period, the shutter 8 is turned on and the BPF 9 is turned off, and a color image of subject 1 is acquired using only the light focused by the concave mirror 4.

[0031] In holographic imaging, the position of the single-chip color image sensor 6 does not need to be near the focal length of the concave mirror 4. However, in imaging using a single light source, it is desirable for the position of the single-chip color image sensor 6 to be near the focal length of the concave mirror 4 in order to maintain resolution. Furthermore, in the configuration shown in Figure 1, since it is necessary to selectively perform two types of imaging by switching between time zones, it is desirable that the position of the single-chip color image sensor 6 be near the focal length of the concave mirror 4 (or the plane mirror 5 if light from the plane mirror 5 is used for imaging with a single light source) to match the imaging with a single light source.

[0032] Figure 2 illustrates the wavelength range of light incident on each pixel of the single-chip color image sensor 6 due to the ON / OFF switching operation of the BPF9. In single-light imaging, pixels for R, G, and B are incident on the usual broadband (e.g., 150-200 nm wide) R, G, and B corresponding color light determined by the OCF characteristics. In contrast, in holographic imaging, each pixel is incident on light that has passed through both the BPF9 and the OCF. As a result, the R, G, and B pixels are incident on light whose bandwidth corresponding to R, G, and B color light has been narrowed to the bandwidth defined by the BPF9 (e.g., 10 nm wide). To cover the entire visible light spectrum solely through holographic imaging, for example, approximately 40 bands would be needed for a 10nm width, making implementation impractical.

[0033] In this embodiment, color information across the entire visible light spectrum is acquired by imaging with a single light source, and then information obtained from the complex amplitude (amplitude-phase distribution) of subject 1, particularly depth information, is acquired by imaging using holography. By using both imaging with a single light source and imaging using holography, it is possible to acquire highly accurate subject information. Regarding the latter, an OCF and BPF9 with three bands are used to obtain at least one complex amplitude (amplitude-phase distribution) from each of the R, G, and B bands. However, it is also possible to increase the number of bands to obtain a configuration that obtains complex amplitudes (amplitude-phase distributions) over a wider bandwidth.

[0034] By using a monochrome image sensor instead of the single-chip color image sensor 6 in the configuration of Figure 1, and setting the BPF9 to switch in a time-division manner to transmit the wavelength bands of the narrowband R, G, B (hereinafter referred to as nR, nG, nB) obtained by the BPF9 and OCF, or the wideband R, G, B (hereinafter referred to as wR, wG, wB) obtained by the OCF, the same effect as above can be obtained by sequentially performing holographic imaging using nR, nG, nB and imaging with a single light source using wR, wG, wB.

[0035] Furthermore, in the holographic imaging and playback device 50 shown in Figure 1, a prism (B / S) 3 may be provided between the subject 1 and the lens 2 to split the light from the subject 1 into three colored lights, R, G, and B, and the configuration of the device 50 shown in Figure 1 may be provided for each colored light. In this case, the image sensor may be a monochrome-compatible image sensor, and the BPF 9 may be configured to narrow the bandwidth of each of the R, G, and B colored lights.

[0036] (Embodiment 2) Figure 3 shows the overall configuration, mainly the optical system, of the holographic imaging and reproduction apparatus 150 according to Embodiment 2 of the present invention. Note that in this embodiment, many of the components have substantially the same function as those in Embodiment 1; therefore, such components are denoted by adding 100 to the reference numeral of the component in Embodiment 1, and their detailed explanation is omitted to avoid complexity. Regarding the holographic reproduction apparatus unit 40 shown in Embodiment 1, the configuration is the same in this embodiment as well, and is therefore omitted from the drawings (the same applies to Figures 6, 8, and 9 described below). Furthermore, in this embodiment, when obtaining a hologram image, instead of using the phase shift method to obtain the complex amplitude, methods that can be calculated in a single imaging (exposure) are used, such as reference light tilt, parallel phase shift, and the use of random phase reference light (the same applies to modified embodiments 1 and 2 described later). Of course, the complex amplitude may also be obtained using the phase shift method, as in Embodiment 1. A key feature of the holographic imaging and playback device 150 according to this embodiment is that, as shown in Figure 3, it is possible to perform both holographic imaging and single-light imaging simultaneously by providing dedicated image sensors 106a and 106b, respectively.

[0037] As shown in Figure 3, light from the subject 101 passes through a first polarizer 110a positioned behind the lens 102, which transmits linearly polarized light at a 45-degree angle, and is then split by the SLM 116. Plane waves and spherical waves reach the first single-chip color image sensor 106a, and only spherical waves reach the second single-chip color image sensor 106b. This configuration allows for holographic imaging with the former and imaging with a single light source with the latter. Specifically, the plane waves reaching the first single-chip color image sensor 106a are the vertical (or horizontal) linearly polarized component of the incident light, which is linearly polarized at 45 degrees, and the spherical waves reaching the first single-chip color image sensor 106a are the horizontal (or vertical) linearly polarized component of the incident light, which is linearly polarized at 45 degrees. The second polarizer 110b, positioned on the SLM 116 side of the first single-chip color image sensor 106a, aligns the polarization components of each light source, causing the two lights to interfere with each other, thereby producing a hologram.

[0038] As shown in Figure 4, the patterns that can be displayed on the SLM116 include a spherical wave (a) imaged on the first image sensor 106a, a spherical wave (b) imaged on the second image sensor 106b, and a pattern (c) obtained by combining these spherical waves (a) and (b). This pattern has the effect of splitting the incident horizontal (or vertical) linearly polarized component into two spherical waves. However, it is also possible to divide the region of the SLM116 and use a pattern in which, 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 on a pixel-by-pixel basis, but can be on a block-by-block basis, where multiple pixels are grouped together. Furthermore, the SLM116 can be a transmissive or reflective type. Also, it is possible to use elements other than liquid crystal displays (LCDs), such as DMDs.

[0039] In the configuration of this embodiment, the shutter 8 used in Embodiment 1 described above is unnecessary, and the BPF 109 only needs to be placed in the optical path between the SLM 116 and the first single-chip color image sensor 106a, eliminating the need for ON / OFF switching. Thus, since the shutter 8 is unnecessary and the switching operation and structure of the BPF 109 are unnecessary, the structure of the device is simpler, and a system that can achieve faster imaging is possible.

[0040] The distances from the SLM116 to the image sensors 106a and 106b may be the same for both image sensors 106a and 106b. However, the first image sensor 106a may be placed at a distance that is considered to yield the highest resolution when using holography (a distance at which the images of plane waves and spherical waves are the same size), while the second image sensor 106b may be placed at the focal length.

[0041] Furthermore, the holographic imaging and playback device 150 of this embodiment can obtain substantially the same effects and advantages as the holographic imaging and playback device 50 of Embodiment 1 described above. That is, a monochrome image sensor may be used instead of the first single-chip color image sensor 106a shown in Figure 3. In this case, a BPF is also placed on the SLM 116 side of the second single-chip color image sensor 106b, and the respective BPFs are synchronized with each other so that the imaging operations of each image sensor 106a and b can be performed in a time-division manner. The same effect can be obtained by switching to narrowband nR, nG, and nB as shown in Figure 2(B)I using the BPF 109 placed on the SLM 116 side of the first single-chip color image sensor 106a, and by switching to wideband wR, wG, and wB as shown in Figure 2(B)II using the BPF placed on the SLM 116 side of the second single-chip color image sensor 106b for imaging.

[0042] Furthermore, similar to the holographic imaging and reproduction device 50 of Embodiment 1 described above, in the holographic imaging and reproduction device 150 shown in Figure 3, a prism (B / S) 103 may be provided between the subject 101 and the lens 102 to split the light from the subject 101 into three colored lights, R, G, and B, and the configuration of the device 150 shown in Figure 3 may be provided for each colored light. In this case, each image sensor may be a monochrome image sensor, and the BPF 109 may be placed only on the SLM 116 side of the first image sensor (corresponding to the first single-chip color image sensor 106a) related to each colored light, and the BPF 109 may function to narrow the bandwidth of each of these colored lights.

[0043] [Techniques for combining images when obtaining a new reconstructed image] The following describes in detail a configuration in which holographic imaging and playback devices 150 according to Embodiment 2 use both holographic imaging and imaging with a single light source. The configuration described below corresponds to the configuration of the image combination unit 14 within the subject image reconstruction means 11 mentioned above. For the sake of simplicity, this simulation uses monochrome images for explanation. However, when dealing with actual color images, you should apply the same process described using monochrome images to each of the R, G, and B color channels. In the following explanations, the term "object" may be used instead of "subject." Figure 5 shows the general flow of imaging using holography and imaging using a single light source. The upper part schematically shows the output image processing flow for hologram formation and object image reconstruction in imaging using holography (I). The numerical parameters used are the values ​​shown in Figure 3. For example, the distance between the SLM116, which generates plane waves and spherical waves, and the image sensor 106a was set to 500 mm to acquire a hologram image formed on the imaging surface.

[0044] If we obtain the intensity distributions (I1~I4) of four hologram images by changing the phase in four steps, 0, π / 2, π, and 3π / 2, using the 4-step phase shift method, then the complex amplitude distribution (amplitude-phase distribution) u on the imaging plane of the object can be expressed as shown in equation (1) below. u = 1 / 4 × {(I1 - I3) + i(I2 - I4)} (where i is the imaginary unit) ... (1) By performing a calculation that propagates this complex amplitude distribution back from the imaging plane to the object plane, the complex amplitude distribution (amplitude-phase distribution) at the object position is obtained, and a reconstructed image of subject 101 is obtained.

[0045] The lower half of Figure 5 shows the object image in imaging with a single light source (II). For example, by setting the distance between the SLM116 that generates spherical waves and the second single-chip color image sensor 106b to 250 mm, a color image (intensity distribution) of an object consisting of R, G, and B is obtained on the imaging surface.

[0046] Using the above methods, R, G, and B information across the entire visible light spectrum can be acquired in imaging with a single light source, and in imaging using holography, complex amplitude distributions (amplitude-phase distributions) at various object positions can be acquired using at least one narrow band from each of the R, G, and B wavelength bands.

[0047] The calculations shown in Figure 5 do not include the effects of noise, so there is no difference in image quality between the two imaging methods, holography-based imaging I and single-light imaging II (between images (D) and (E)). However, in reality, due to the reduction in light intensity caused by the limitation of wavelength, holography-based imaging I is more susceptible to the effects of noise. In other words, 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 signal-to-noise ratio is S / √S = √S, which is proportional to the square root of the number of photons.

[0048] For example, if imaging with a single light source is performed using light with a wavelength of 150-200 nm without wavelength width limitation by a BPF, and imaging using holography is performed by limiting the wavelength width to 10 nm with a BPF, the amount of light in the latter case will decrease to about one-tenth or less of the former case, depending on the effect of the spectral distribution, and the signal-to-noise ratio will also deteriorate. Therefore, taking into account this difference in the amount of incident light, the signal-to-noise ratio (S / N ratio) of the two imaging methods described above is worse when using holography.

[0049] The following describes an example of a configuration according to an embodiment in which a useful image can be obtained from two types of images obtained with the device shown in Figure 3. As shown in Figure 6, the image is taken with a field of view that includes three objects A, B, and C at different distances from each other, and Figure 7 shows the image images obtained using the two shooting methods at that time. Note that the holographic imaging and playback device 450 in Figure 6 is the same as the holographic imaging and playback device 150 of Embodiment 2, but for convenience, the reference numerals of the components shown in Figure 3 plus 300 are used for the corresponding components. The reconstructed image using holography (hereinafter referred to as the first image) has a lot of noise (represented by dots within objects A, B, and C in Figure 7), but by backpropagating the image in accordance with the distances a, b, and c of each object, the contrast of objects at those distances increases, thus providing information about the objects at those distances. On the other hand, the image captured with a single light source (hereinafter referred to as the second image) has less noise, but the relationship between distance and objects is unclear. Here, the range of distances in which objects exist is assumed to be within the depth of field range in single-light photography.

[0050] In the first image, to create a low-noise image for each part of the object, only the high-contrast pixel areas in the second image that correspond to the parts in the first image are extracted. In other words, the high-contrast parts in the second image are identified, and based on the positional information of the corresponding parts in the first image, each part in the second image is positioned to form a new first image. By doing this, we can obtain a first image (reconstructed image) with less noise for objects located at distances a, b, and c. In Figure 7, only the in-focus areas (high-contrast areas) are extracted and used. However, it is also possible to intentionally create a blurred image by combining the blurred images of the out-of-focus areas, taking advantage of the information that the image is out of focus in holographic photography.

[0051] By performing the above steps for each of the R, G, and B channels, a low-noise color image of each object at a given distance can be obtained. Here, it is assumed that there is a correlation between the narrowband signals (nR, nG, nB) for each R, G, and B color light obtained using holography and the original wideband signals (wR, wG, wB) for each R, G, and B color light, making it possible to determine focus for each color light. However, depending on the subject and shooting conditions, errors may occur when acquiring color information. As the number of bands in the narrowband signal acquired increases, this error can be reduced, so it is desirable to determine the number of bands according to the application.

[0052] Furthermore, as another application, holographic imaging is known to contain higher spatial frequency information of an object compared to imaging with a single light source. For example, by performing FFT processing on images obtained with these two imaging methods, and synthesizing the high-frequency information obtained from the former imaging with the low-frequency information obtained from the latter imaging to reconstruct the image, it is possible to obtain an image that balances both image quality and spatial frequency bandwidth.

[0053] Another potential application is in obtaining moving images. Specifically, when using the 4-step phase-shift method in holographic imaging, acquiring four images and then calculating the reconstructed image takes time, which may limit the improvement of the frame rate.

[0054] On the other hand, with single-light imaging, it is possible to capture images at high frame rates up to the limits of the image sensor's performance. Therefore, for video recording at the highest frame rate, the image information from single-light imaging is used, and then the same synthesis method as in Figure 7 is applied. That is, by extracting only the high-contrast pixel areas of the second image corresponding to the distance of each object in the reconstructed image obtained using holography, a color video of each object at its respective 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 subjects that are photographed, for example, where the movement of an object changes drastically within the same distance, but the change in the depth direction of the object is small.

[0055] As described above, the imaging device of this embodiment Place This technology enables incoherent digital holography, which allows for the acquisition of the complex amplitude (amplitude phase distribution) of a subject while maintaining the functionality of conventional imaging systems. It can be applied to various devices such as cameras, measuring instruments, and microscopes that accurately capture information about objects.

[0056] Furthermore, the incoherent digital holography imaging device according to the present invention Place and Therefore, the invention is not limited to the embodiment described above, and various other modifications are possible. For example, the optical system can be modified as shown in Figures 8 and 9. Furthermore, since many of the following modifications have similar functions to those of Embodiment 2, for such components, the reference numeral 400 is added to the reference numeral of the component in Embodiment 2 for Modification 1, and 500 is added for Modification 2. A detailed explanation is omitted to avoid unnecessary explanation.

[0057] (Change type 1) As shown in Figure 8, this modified configuration includes a rotating polarizer 517, which is rotatable about the optical axis, placed on the SLM 516 side of the single-chip color image sensor 506, to enable temporal switching between holographic imaging and imaging with a single light source. In holographic imaging, the rotating polarizer 517 placed on the SLM 516 side of the single-chip color image sensor 506 aligns the polarization directions of the two light waves, similar to the case of Embodiment 2 shown in Figure 3. However, in imaging with a single light source, the rotating polarizer 517 is rotated to transmit only the spherical wave, which is the horizontal (or vertical) linearly polarized component. In this case, it is essential to generate a spherical wave in the SLM516 that forms an image on the imaging plane, in accordance with the shooting conditions using a single light source. The BPF509 performs an ON / OFF switching operation, as in the first embodiment described above. In this modified embodiment 1 configuration, only one single-chip color image sensor 506 is required, and the shutter used in the first embodiment is unnecessary, resulting in a simpler configuration.

[0058] (Change type 2) As shown in Figure 9, this modified configuration includes a polarizing beam splitter (PBS) 603 that separates object light into S-polarized and P-polarized light. The separated S-polarized light is imaged onto the second image sensor 606b via lens 602a to perform imaging with a single light source. Meanwhile, the separated P-polarized light is transmitted as linearly polarized light at an oblique angle of 45° by a half-wave plate 618. From there, holographic imaging is performed with the first image sensor 606a, similar to modified configuration 1 shown in Figure 8. Furthermore, the BPF609 should always be set to the ON state. Compared to the above modification embodiment 1, this modified embodiment has the advantage of eliminating the light loss in the rotating polarizer 517 used in the above modification embodiment 1, and enabling efficient utilization of incident light.

[0059] (Other forms of modification) Other modifications to the optical system include, for example, the Michelson-type equipath-length optical system shown in Embodiment 1 above, but it is also possible to use, for example, a Mach-Zehnder type or a bypass-path type equipath-length Fizeau optical system. In the above embodiment, the first image, which is the reconstructed image of the subject, is a color image, but it is also possible to use a monochrome image. That is, the incoherent digital holography imaging device of the present invention Place In this case, it is acceptable whether the first image is a color image or a monochrome image, as long as a color image is obtained when combined with the second image. However, the second image must be a color image. [Explanation of symbols]

[0060] 1, 101, 401, 501, 601 Subject 2, 102, 402, 502, 602, 602a lenses 3 Beam Splitter (B / S) 4 concave mirror 5 plane mirror 6, 106a, 106b, 406a, 406b, 506, 606a, 606b Single-chip color image sensor 7. Phase shifting means (piezo element) 8 shutters 9, 109, 409, 509, 609 Bandpass Filters (BPF) 11 Subject image reconstruction means 12 First Image Processing Unit 13. Second image storage unit 14 Image Combination Section 15 monitors 20, 120, 420, 520, 620 Holographic imaging unit 40 Holographic Playback Unit 50, 150, 450, 550, 650 Holographic Imaging and Regeneration System 110a, 110b, 410a, 410b, 510, 610 polarizers (first polarizer, second polarizer) 116, 416, 516, 616 SLM 517 Rotating polarizer 603 Polarizing Beam Splitter (PBS) 618 Half-wave plate

Claims

1. The system includes a first imaging function unit that captures a hologram image formed by interfering incoherent light from a subject, which is incident from an imaging lens and divided into two systems, and forms a first image which is a reconstructed image of the subject; and a second imaging function unit that captures a single beam of light from the subject, which is incident from the imaging lens, and forms an image to obtain a second image which is a color image of the subject, simultaneously with or sequentially with the first image. The system includes an image combination unit that combines the image information of the first image and the color image information of the second image to form a new color reconstructed image of the subject, The image information contained in the aforementioned first image is color image information. Of the two imaging function units, at least the first imaging function unit is equipped with an optical wavelength band selection means that selects and uses light from a portion of the wavelength bands of each of the three primary color lights that form the first image. The image combination unit is configured to identify a predetermined area based on the contrast level within the first image, which has positional information representing the distance to each part of the subject, and to set an area in the second image corresponding to the identified predetermined area within the first image, thereby forming a new first image. The incoherent digital holography imaging apparatus is characterized in that the first imaging function unit is configured to determine positional information representing 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 backpropagated to a predetermined distance.

2. The incoherent digital holography imaging apparatus according to claim 1, characterized in that the optical wavelength band selection means is a bandpass filter.

3. The incoherent digital holography imaging apparatus according to claim 1 or 2, characterized in that the width of the aforementioned wavelength band is 50 nm or less.

4. The incoherent digital holography imaging apparatus according to any one of claims 1 to 3, characterized in that the second imaging function unit is equipped with a shutter that blocks one of the two divided incoherent light systems when obtaining the second image.

5. The imaging optical system in the first imaging function unit comprises: a beam splitting means for splitting a beam of light from the subject into two systems; a plane mirror that receives one of the split beams of light and reflects a plane wave; a concave mirror that receives the other split beam of light and reflects it in a way that converges a spherical wave; an image sensor that acquires a color hologram image by interfering the plane wave from the plane mirror with the spherical wave from the concave mirror; and a bandpass filter on the common optical path between the plane wave and the spherical wave that narrows the wavelength band of each of the three primary color lights that are incident on the image sensor, characterized in that the incoherent digital holography imaging apparatus is as described in any one of claims 1 to 4.

6. The incoherent digital holography imaging apparatus according to claim 5, further comprising a phase shift means for moving either the plane mirror or the concave mirror by a predetermined phase in the optical axis direction.

7. The incoherent digital holography imaging apparatus according to claim 5 or 6, characterized in that the imaging optical system in the second imaging function unit is configured to be shared with the imaging optical system in the first imaging function unit in at least a portion thereof, and comprises: a light beam splitting means; a concave mirror that receives the other light beam split by the light beam splitting means and reflects it to converge a spherical wave; and an image sensor that forms an image of the spherical wave from the concave mirror to acquire a color image of the subject.

8. The imaging optical system in the first imaging function unit and the imaging optical system in the second imaging function unit share a common optical path through which a first polarizer is arranged, leading to a light beam splitting means that splits the light beam from the subject, while the image sensors are provided separately from each other. The aforementioned light beam splitting means is a spatial light modulator, The incoherent digital holography imaging apparatus according to claim 2, any one of claims 3-4 referencing claim 2, or any one of claims 5-7. The incoherent digital holography imaging apparatus is characterized in that the bandpass filter and the second polarizer are arranged on a common optical path of a plane wave and a spherical wave from the light beam splitting means to the image sensor of the first imaging function unit so that a color hologram image can be obtained at the image sensor of the first imaging function unit, and the spherical wave from the light beam splitting means to the image sensor of the second imaging function unit is imaged at the image sensor of the second imaging function unit so that a color image of the subject can be obtained.

Images