Incoherent digital holographic imaging device

Abstract

To provide an incoherent digital holography imaging apparatus and imaging method capable of forming an image of a new subject of predetermined image quality from a reconstituted image of the subject obtained by using holography technology easily with high accuracy.SOLUTION: The incoherent digital holography imaging apparatus comprises: a first imaging function section that photographs a hologram image by incoherent light from subject 1 and forms a first image which is a reconstituted image of subject 1; a second imaging function section that images a single luminous flux from subject 1 and photographs a second image which is an image of subject 1; and an image combination section 14 that obtains position information on each portion of subject 1 on the basis of the first image which is the reconstituted image of subject 1 obtained by the first imaging function section, segments each portion of the second image corresponding to each of the first image obtained by the second imaging function section on the basis of the obtained position information, sets a position, and form a new first image.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an incoherent digital holography imaging device for acquiring digital holography using incoherent light with a short coherence length. Place Regarding. [Background technology]

[0002] Digital holography is an imaging technique that can acquire the complex amplitude (amplitude-phase distribution) of a subject, and has many advantages, such as excellent spatial and depth resolution, as well as the ability to adjust the focus position through calculations.In particular, incoherent digital holography technology has advanced in recent years, which can capture digital holograms using incoherent light such as sunlight, LED, and fluorescent light, without using special light sources such as lasers, and this has expanded the range of applications of holography.

[0003] In incoherent digital holography, the object light is split into two beams, and a hologram (interference fringes) is formed on the imaging surface by causing them to self-interfere with each other. In order to cause interference between incoherent lights, the wavelength width of the light source is limited to 100 nm or less using a wavelength filter (bandpass filter) (Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] J. Rosen and G. Brooker: “Digital spatially incoherent Fresnel holography”, Optics Letters Vol. 32, No. 8, pp. 912-914 (2007) Summary of the Invention [Problem to be solved by the invention]

[0005] However, for example, as described above, if the wavelength width of natural light is limited to the extent that coherence between the two beams is obtained, the light utilization efficiency will be significantly reduced, resulting in a problem of a significant decrease in S / N due to optical shot noise in the imaging element, etc. Furthermore, for example, an image of an object is reconstructed by performing a predetermined calculation on a hologram image captured by an image sensor. However, the image of the object obtained in this manner has a problem in that noise in the image sensor has a significantly greater effect on the quality of the reconstructed image than in a normal imaging method in which light from the object is directly incident on the image sensor to capture the image of the object. Conversely to the above-mentioned problem, there are also cases where it is desired to make a predetermined image have a lower image quality (for example, a blurred image). Therefore, it is desirable to easily and accurately form a new image of an object with a desired image quality from a reconstructed image of the object based on the above-mentioned hologram image.

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

[0007] The incoherent digital holographic imaging device of the present invention comprises: It is incident from the imaging lens, A hologram image is formed by causing incoherent light from a subject split into two systems to interfere with each other, and a first image is a reconstructed image of the subject. profit a first imaging function unit; The light is incident from the imaging lens, a second imaging function unit that forms an image of a single light beam from a subject and obtains a second image, which is an image of the subject, simultaneously with or sequentially after the first image; an image combining unit that combines information contained in the first image and information contained in the second image to form a new image of the subject; 、 The image combination unit is configured to identify, for each part of the subject, a predetermined area based on a contrast level in the first image having position information indicating a distance to the part, set an area in the second image corresponding to the predetermined area in the identified predetermined area of ​​the first image, and form a new first image. It is characterized by the following. Furthermore, it is preferable that the second imaging function section includes a shutter that blocks one of the two split beams of light when obtaining the second image. 。 child Here, the first imaging function unit is From the imaging surface relating to the first image Each part of the subject to of Representing distance Location information was obtained The aforementioned Complex amplitude distribution of holographic images Reverse When propagated before It is preferable that the determination be based on the contrast of the first image.

[0008] Furthermore, it is preferable that the imaging optical system in the first imaging function unit includes a beam splitter that splits the beam from the subject into two beams, a plane mirror that receives one of the split beams and reflects it as a plane wave, a concave mirror that receives the other of the split beams and reflects it so as to converge as a spherical wave, an imaging element that obtains a hologram image by causing the plane wave from the plane mirror and the spherical wave from the concave mirror to interfere with each other, and a wavelength filter that narrows the wavelength range of the light waves that are incident on the imaging element on a common optical path of the plane wave and the spherical wave. It is also preferable to provide a phase shifting means for shifting either the plane mirror or the concave mirror by a predetermined phase in the optical axis direction.

[0009] Furthermore, it is preferable that the imaging optical system in the second imaging function unit is configured so that at least a part of it is shared with the imaging optical system in the first imaging function unit, and is provided with the light beam splitting means, the concave mirror that receives the other light beam split by the light beam splitting means and reflects it to converge into a spherical wave, and the imaging element that focuses the spherical wave from the concave mirror to obtain an image of the subject.

[0010] In addition, the imaging optical system in the first imaging function unit and the imaging optical system in the second imaging function unit share an optical path in which a first polarizer is disposed up to a light beam splitting means for splitting a light beam from a subject, but each of them is provided with an imaging element separately, The light beam splitting means is a spatial light modulator, It is preferable that a wavelength filter and a second polarizer are arranged on a common optical path of the plane wave and the spherical wave from the beam splitting means to the image sensor of the first imaging function unit so that a hologram image can be obtained at the image sensor of the first imaging function unit, and that the spherical wave from the beam splitting means to the image sensor of the second imaging function unit is imaged on the image sensor of the second imaging function unit to obtain an image of the subject. [Effects of the Invention]

[0012] In incoherent digital holography imaging technology, the reconstructed image obtained (hereinafter referred to as the first image) contains position information and can be used to construct a three-dimensional image, but it also has the characteristic of containing a lot of noise. The inventors of the present application therefore came up with the idea of ​​combining two images to form a new image of the subject with the desired image quality, taking advantage of the fact that although it is not possible to obtain positional information for each part, an image (hereinafter referred to as the second image) obtained using a normal imaging method that is less affected by noise can be obtained simultaneously with the first image using a common optical system, and corresponding parts of the subject in both images can be easily distinguished.

[0013] That is, as an example, based on a first image, which is a reconstructed image of the subject obtained using a hologram in the first imaging function unit, positional information of each part of the subject is obtained, and based on the obtained positional information, each part of the second image obtained by the second imaging function unit is arranged to form a new first image.

[0014] This allows the incoherent digital holography imaging device of the present invention to PlaceIn this system, a new image of desired image quality can be obtained based on the information of the obtained first and second images. Moreover, since both images can be captured almost simultaneously using a common optical system, a new image of desired image quality can be obtained easily and with high accuracy. Specifically, using the above example, in incoherent digital holography imaging technology, it is possible to prevent the decrease in S / N ratio that accompanies the wavelength width restriction of light that is imposed to achieve light coherence, improve the problem of the image sensor being susceptible to noise, and obtain a 3D reconstructed image of the subject that is less susceptible to noise. Furthermore, by utilizing this invention, it is possible to construct cameras, measuring devices, microscopes, and the like that can accurately capture information about a subject. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a conceptual diagram for explaining a holographic imaging and reproducing device according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a conceptual diagram for explaining a holographic imaging and reproducing device according to a second embodiment of the present invention. [Figure 3] In the holographic imaging and reproduction device according to the second embodiment of the present invention, the patterns displayed on the SLM are (a) a spherical wave pattern focused on the first imaging element 106a, (b) a spherical wave pattern focused on the second imaging element 106b, and (c) a combination of (a) and (b)). [Figure 4] FIG. 10 is a conceptual diagram showing the premise of a method for improving the quality of a reconstructed image by a system that combines holographic imaging and single-light imaging in a holographic imaging and reconstructing device according to a second embodiment of the present invention. [Figure 5] FIG. 5 shows the image state resulting from adding noise to the two imaging methods shown in FIG. 4 (the upper half is imaging using holography, and the lower half is imaging using a single light source). [Figure 6]FIG. 10 is a conceptual diagram for explaining a method for capturing an image with an angle of view that includes three objects A, B, and C at different distances using the holographic imaging and reproducing device according to the second embodiment of the present invention. [Figure 7] FIG. 7 is a conceptual diagram for explaining a method for forming a useful image from two types of images obtained by the two imaging methods shown in FIG. 6. [Figure 8] FIG. 10 is a conceptual diagram for explaining a holographic imaging and reproducing device according to a first modified embodiment of the present embodiment. [Figure 9] FIG. 10 is a conceptual diagram for explaining a holographic imaging and reproducing device according to a second modified embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an incoherent digital holographic imaging device and imaging method of the present invention will be described using an embodiment, in which the configuration of a holographic imaging and reproducing device is taken as an example. The following explanation will first focus on the configuration of the optical system using Embodiments 1 and 2, and then explain an example of a technique for combining a reconstructed image of a subject using holography with a general subject image using a single light, based on the configuration of Embodiment 2. After that, supplementary explanations will be given on the optical system of the above-mentioned holographic imaging and reproduction device, citing two modified embodiments.

[0017] [Configuration of holographic imaging and reconstructing device (mainly optical system)] (Embodiment 1) FIG. 1 shows the overall configuration, mainly consisting of an optical system, of a holographic imaging and reproducing device 50 according to a first embodiment of the present invention. This holographic imaging and reproducing device 50 constitutes an incoherent digital holographic imaging device using a Michelson interferometer optical system. This imaging and reproducing device 50 has a holographic imaging function and a single-light imaging function (imaging using a normal imaging system), and by using both functions, it is possible to obtain low-noise incoherent digital holographic images.

[0018] First, we will explain holographic imaging. Object light from subject 1 is collimated by lens 2 and enters beam splitter (B / S) 3. One of the split beams enters plane mirror 5 and is reflected as collimated light, and the other split beam enters concave mirror 4 and is reflected as convergent light. The two reflected beams are incident on the beam splitter (B / S) 3 again, and the former reflected beam and the latter transmitted beam travel toward the imaging element 6 and form a hologram on the imaging surface of the imaging element 6 by self-interference.

[0019] Here, the phase shift method is used to obtain the object beam while avoiding the superposition of direct and conjugate beams in in-line holography, and among these, the four-step phase shift method is used to simplify the calculation. The plane mirror 5 is moved in the optical axis direction by a phase shifting means (piezo element) 7 from a reference position by distances of 1 / 8, 2 / 8, and 3 / 8 times the wavelength (the optical path length of the light traveling toward the plane mirror 5 changes by 1 / 4, 2 / 4, and 3 / 4 times the wavelength), and the phase changes in four stages: 0, π / 2, π, and 3π / 2.

[0020] A light-blocking shutter 8 is shown on the beam splitter (B / S) 3 side of the plane mirror 5, but this is used when taking pictures using a single light, as will be described later, and is not used when taking pictures using holography. On the other hand, a wavelength filter 9 is arranged on the beam splitter (B / S) 3 side of the imaging element 6 to narrow the wavelength range of light so that interference can occur even with incoherent light (light with a short coherence length).

[0021] Hologram image data is output from the imaging element 6 to subject image reconstruction means 11, and a first image calculation unit 12 within subject image reconstruction means 11 uses a phase shift method to calculate the amplitude and phase distribution on the imaging plane from the four hologram pieces of information formed on the imaging plane. Specifically, the amplitude and phase distribution at the subject position can be reconstructed by performing a calculation that backpropagates from the imaging plane to the subject plane. Instead of the above four-step phase shifting method, a three-step, two-step, or five-step or more phase shifting method may be used, or a complex amplitude may be acquired in one imaging (exposure) by using a reference beam tilt, parallel phase shift, or random phase reference beam (see Ito and Shimobaba, "Introduction to Holography: 3D Imaging and Measurement Using a Computer," Kodansha, pp. 119-125).

[0022] Alternatively, instead of moving the plane mirror 5, a four-step phase shift method may be used in which the concave mirror 4 is moved by the phase shift means 7 to change the phase of the light passing through the concave mirror 4 in four steps. In this case, when photographing with a single light beam, which will be described later, photographing may be performed with the movement by the phase shift means 7 stopped, or photographing may be performed while moving the concave mirror 4 by the phase shift means 7, as in photographing using holography. In the latter case, an effect can be expected in which an image that is in focus over a wide depth range of the subject 1 can be obtained when photographing with a single light beam.

[0023] Next, we will explain imaging using a single light source. By operating the shutter 8 provided on the beam splitter (B / S) 3 side of the plane mirror 5 and turning on the light blocking function, the light passing through the plane mirror 5 is blocked, and only the light passing through the concave mirror 4 reaches the image sensor 6. This shutter 8 can be a mechanical shutter, a liquid crystal shutter, or the like. As a result, an image (intensity distribution) of the subject 1 can be obtained directly from the image sensor 6. Note that the shutter 8 may also be located on the concave mirror 4 side, allowing only the light from the plane mirror 5 to reach the imaging surface. In this case, it is possible to capture an image of the subject 1 in an imaging relationship between the lens 2 and the image sensor 6.

[0024] In addition, image data obtained by a single light is output from the imaging element 6 to the subject image reconstruction means 11, and multiple image data obtained by the single light are stored in the second image storage unit 13 within the subject image reconstruction means 11. Thereafter, the amplitude / phase distribution data obtained by the calculation in the first image calculation unit 12 and the image data stored in the second image storage unit 13 are combined in the image combination unit 14 in the subject image reconstructing means 11, and this combined reconstructed image (a new first image) is output as a subject image signal to an external monitor 15 or the like. The image combination process performed in the image combination unit 14 will be described later. The subject image reconstruction means 11, the monitor 15, etc. constitute a holographic reproduction device section 40 corresponding to the holographic imaging device section 20.

[0025] The device of this embodiment alternates between the above-mentioned holographic imaging function and the single-light imaging function. That is, during a first period, shutter 8 is turned off and hologram images of subject 1 corresponding to phases of 0, π / 2, π, and 3π / 2 are captured using the four-step phase shift method. During a second period, shutter 8 is turned on and an image of subject 1 is captured using only the light converged by concave mirror 4.

[0026] Note that the wavelength filter 9 may be constantly operating, but since there is no need to limit the wavelength width when photographing with a single light in the second period, in order to improve the light utilization efficiency, it is desirable to operate the wavelength filter 9 by switching it on and off in the same way as the shutter 8 so that it does not operate in the second period. Methods that can be used to turn the wavelength filter 9 on and off include physically inserting it into or removing it from the optical path, or using liquid crystal to change the transmission wavelength band.

[0027] When photographing using holography, the position of the image sensor 6 does not need to be near the focal length of the concave mirror 4, but when photographing using a single light, it is desirable that the position of the image sensor 6 be near the focal length of the concave mirror in order to maintain resolution. Furthermore, in the configuration of Figure 1, since it is necessary to selectively perform two types of photography by switching the time, it is desirable that the position of the image sensor 6 be near the focal length of the concave mirror 4 (or the plane mirror 5 when light from the plane mirror 5 is used for photography using a single light) in accordance with photography using a single light.

[0028] (Embodiment 2) FIG. 2 shows the overall configuration, focusing on the optical system, of a holographic imaging and reproducing device 150 according to a second embodiment of the present invention. Since many of the components in this embodiment have substantially the same functions as those in the first embodiment, the reference numerals of those components in the first embodiment are given with an additional 100, and detailed descriptions thereof will be omitted to avoid redundancy. Holographic reproducing device section 40 shown in the first embodiment has the same configuration, and is therefore omitted from the drawings (the same applies to FIGS. 6, 8, and 9, which will be described below). Furthermore, in this embodiment, complex amplitudes are obtained by using a single imaging (exposure) technique, such as reference beam tilt, parallel phase shift, and the use of a random phase reference beam, rather than a phase shift technique (the same applies to Modifications 1 and 2, which will be described later). The holographic imaging and reproduction device 150 according to this embodiment is characterized in that, as shown in FIG. 2, it is possible to perform both holographic imaging and single-light imaging simultaneously by providing dedicated imaging elements 106a and 106b, respectively.

[0029] As shown in Figure 2, light from subject 101 passes through first polarizer 110a, which is located after lens 102 and transmits linearly polarized light at a 45-degree angle, and is then split by SLM 116. Plane and spherical waves reach first image sensor 106a, while only the spherical wave reaches second image sensor 106b. This allows holographic imaging at the former and single-light imaging at the latter. Specifically, the plane wave reaching first image sensor 106a is the vertically (or horizontally) linearly polarized component of the 45-degree linearly polarized incident light, and the spherical wave reaching first image sensor 106a is the horizontally (or vertically) linearly polarized component of the 45-degree linearly polarized incident light. Second polarizer 110b, located on the SLM 116 side of first image sensor 106a, aligns the polarization components of the two beams, causing interference between the two beams, resulting in a hologram.

[0030] As shown in FIG. 3, the patterns that can be displayed on the SLM 116 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) that combines (a) and (b). This pattern has the effect of separating the incident horizontally (or vertically) linearly polarized light component into two spherical waves, but it is also possible to use a pattern in which the area of ​​the SLM 116 is divided so that, for example, light reaching odd-numbered pixels is imaged on the first image sensor 106a and light reaching even-numbered pixels is imaged on the second image sensor 106b. This division does not have to be done in pixel units, but can also be done in block units, each consisting of multiple pixels. Note that a reflective SLM 116 may also be used.

[0031] In the configuration of this embodiment, the shutter 8 in the first embodiment is not necessary, and the wavelength filter 109 only needs to be placed on the SLM 116 side of the first image sensor 106a. Therefore, it is possible to construct a system that does not require switching of shutters or the like, has a simple configuration, and can achieve high-speed imaging.

[0032] The distance from the SLM 116 to the image sensors 106a and 106b may be the same for both image sensors 106a and 106b, but they may also be placed at different distances, such as placing the first image sensor 106a at a distance that is considered to provide the highest resolution in holographic imaging (the distance at which the images of the plane wave and spherical wave are the same size) and placing the second image sensor 106b at the focal length.

[0033] [Method of combining images to obtain a new reconstructed image] A detailed description will now be given of a configuration for holographic imaging and reproduction device 150 according to the second embodiment, in which imaging using holography and imaging using a single light are used in combination. The configuration described below corresponds to the configuration of the image combination unit 14 in the subject image reconstructing means 11 described above. In the following description, the term "object" may be used instead of the term "subject." Figure 4 shows the general flow of holographic imaging and single-light imaging. The upper part shows a schematic diagram of the flow of hologram formation and object image reconstruction in holographic imaging (I). The numerical parameters used are those shown in Figure 2. For example, the distance between the SLM 116, which generates plane waves and spherical waves, and the image sensor 106a was set to 500 mm to obtain a hologram image formed on the imaging surface.

[0034] If the intensity distributions of four hologram images (I1 to I4) are obtained by changing the phase in four steps (0, π / 2, π, and 3π / 2) using the four-step phase shift method, the complex amplitude distribution (amplitude-phase distribution) u on the imaging plane of the object can be expressed as follows: u=1 / 4×{(I1-I3)+i(I2-I4)} (i is the imaginary unit) …(1) By performing a backpropagation operation on this complex amplitude distribution from the imaging plane to the object plane, a complex amplitude distribution (amplitude-phase distribution) at the object position is obtained, and a reconstructed image of the subject 101 is obtained.

[0035] The object image in single-light imaging (II) is shown in the lower half of Fig. 4. For example, the distance between the SLM 116 that generates the spherical wave and the second image sensor 106b is set to 250 mm, and the object image (intensity distribution) formed on the imaging surface is acquired.

[0036] Figure 5 shows the results of adding noise to the two imaging methods shown in Figure 4. It is assumed that random noise having a Gaussian distribution is added to the images acquired by the image sensors 106a and 106b, and the standard deviation of the Gaussian distribution is set to 1% or 3% of the maximum pixel value. The upper half of Figure 5 shows how a reconstructed image is formed by adding noise to each of the four holograms I1 to I4 obtained by the first image sensor 106a using holography, while the lower half of Figure 5 shows how an image of an object is obtained by adding the above-mentioned noise to the object image obtained by the image sensor 106b using a single light source.

[0037] Figure 5 shows the reconstructed images along with their PSNR (Peak Signal to Noise Ratio) values. The PSNR values ​​are shown for both the original image and the noise-free reconstructed image. It is clear that the images captured with a single light source are more resistant to noise, both in terms of appearance and PSNR value of the reconstructed images. For example, if the acceptable threshold for image degradation is a PSNR of 30 relative to the output, then Figure 5 clearly shows that even 1% noise is unacceptable in holographic imaging, whereas 3% noise is acceptable in single-light imaging.

[0038] In the example shown in Figure 5, the noise added by the two imaging techniques was set to the same level. However, in reality, imaging using holography is more susceptible to the effects of noise due to the reduction in light intensity caused by wavelength bandwidth limitations. That is, one of the main types of noise detected by the image sensor 106a is optical shot noise. If the number of incident photons is S, the optical shot noise is expressed as N = √S, and the S / N ratio is S / √S = √S, which is proportional to the square root of the number of photons.

[0039] For example, if a single-light image is taken with light of wavelengths between 380 and 780 nm without limiting the wavelength range with a wavelength filter, and if a wavelength filter is used to limit the wavelength range to 10 nm when taking a holographic image, the amount of light in the latter image will be reduced to approximately one-tenth or less of the former image, and the S / N ratio will also deteriorate, although this will depend on the influence of the spectral distribution. Therefore, when this difference in the amount of incident light is taken into consideration, the difference in image quality between the two shooting methods will be greater than the values ​​shown in Figure 5.

[0040] An example of a configuration according to an embodiment that can obtain a useful image from two types of images obtained by the device shown in FIG. 2 will now be described. As shown in Fig. 6, imaging is performed with an angle of view that includes three objects A, B, and C at different distances, and images obtained by the two imaging techniques at that time are shown in Fig. 7. Note that holographic imaging and reproducing device 450 in Fig. 6 uses holographic imaging and reproducing device 150 of embodiment 2, but for convenience, the reference numerals of the corresponding components shown in Fig. 2 are assigned with reference numerals that are 300 larger than the reference numerals of the corresponding components. The reconstructed image using holography (hereinafter referred to as the first image) contains a lot of noise (represented by dots within objects A, B, and C in Figure 7), but by backpropagating the noise corresponding to the distances a, b, and c of each object, the contrast of the objects at those distances increases, allowing information about the objects at those distances to be obtained. On the other hand, the image captured using a single light (hereinafter referred to as the second image) contains less noise, but the relationship between distance and object is unclear. Note that the range of distances in which objects exist is assumed to be within the depth of field when captured using a single light.

[0041] In order to obtain a low-noise image for each part of the object in the first image, only high-contrast pixel areas corresponding to the parts in the first image are extracted from the second image. That is, the high-contrast parts in the second image are identified, and the positions of the parts in the second image are set based on the position information of the corresponding parts in the first image, to form a new first image. By doing so, it is possible to obtain a first image (reconstructed image) with less noise for the object located at each distance a, b, and c. In Figure 7, the in-focus part (high contrast part) is extracted and used, but it is also possible to use information on out-of-focus parts in holographic photography to synthesize the blurred image of the out-of-focus part and create a deliberately blurred image.

[0042] Another application method is that photography using holography is known to contain information about the high spatial frequencies of an object compared to photography using a single light source. For example, by performing FFT processing on the images obtained using these two photography methods and combining the high-frequency information obtained by the former photography with the low-frequency information obtained by the latter photography to reconstruct the image, it is possible to obtain an image that combines image quality and spatial frequency bandwidth.

[0043] Another possible application is to obtain moving images. In other words, when using the four-step phase shift method in holographic imaging, it takes time to obtain four images and then to calculate the reconstructed image, which may limit the improvement of the frame rate.

[0044] On the other hand, when shooting with a single light, it is possible to shoot at a high frame rate up to the limit of the performance of the image sensor itself, so video shooting at the highest frame rate uses image information shot with a single light, and then uses a synthesis method similar to that shown in Figure 7. In other words, by cutting out only the high-contrast pixel areas of the second image corresponding to the distance of each object in the reconstructed image obtained using holography, video images of the object at each distance can be obtained.

[0045] Although distance information cannot be obtained with the time accuracy of the highest frame rate, this embodiment is a particularly effective method for photographing objects in which, for example, the movement of the object changes drastically within the same distance but there is little change in the depth direction of the object.

[0046] As described above, the imaging device and imaging method of this embodiment can realize the function of incoherent digital holography, which can acquire the complex amplitude (amplitude-phase distribution) of a subject, while retaining the functions of imaging using a normal imaging system, such as high S / N and video capture, and can be applied to various devices that accurately capture information about objects, such as cameras, measuring devices, and microscopes.

[0047] Furthermore, the incoherent digital holography imaging device and imaging method according to the present invention are not limited to the above-described embodiments, and various other modifications are possible. For example, the optical system may be modified as shown in FIGS. In addition, since many of the following modified embodiments have similar component functions to those of embodiment 2, for such components, the reference numbers of the components of embodiment 2 are increased by 400 for modified embodiment 1, and by 500 for modified embodiment 2, and detailed explanations thereof are omitted to avoid tediousness.

[0048] (Modification 1) 8, this modified embodiment has a configuration in which a rotary polarizer 517 that can rotate around the optical axis is arranged on the SLM 516 side of the image sensor 506, and the configuration switches over time between holographic imaging and single-light imaging. In holographic imaging, the rotary polarizer 517 arranged on the SLM 516 side of the image sensor 506 operates to align the polarization directions of two light waves, as in the second embodiment shown in FIG. 2, but in single-light imaging, the rotary polarizer 517 is rotated to transmit only a spherical wave that is a horizontally (or vertically) linearly polarized component. In this case, it is essential to generate a spherical wave that forms an image on the imaging surface in accordance with the imaging conditions using a single light using the SLM 516. This configuration requires only one imaging element 506 and does not require a shutter, making it a simpler configuration.

[0049] (Modification 2) As shown in Fig. 9, this modified example has a configuration in which a polarizing beam splitter (PBS) 603 is used to split the object light into S-polarized light and P-polarized light. The split S-polarized light is imaged on a second image sensor 606b via a lens 602a, and photography is performed using a single light beam. On the other hand, the split P-polarized light is transmitted through a half-wave plate 618 as linearly polarized light at an angle of 45°. Thereafter, holographic photography is performed by a first image sensor 606a, as in the first modified example shown in Fig. 8. Compared to the first modified example, this has the advantage of eliminating light loss in the rotating polarizer and enabling efficient use of incident light.

[0050] (Other changes) As for other modifications to the optical system, for example, although the first embodiment uses a Michelson-type equal-path length optical system, it is also possible to use, for example, a Mach-Zehnder type optical system or a roundabout equal-path length Fizeau type optical system. [Explanation of symbols]

[0051] 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 Image sensor 7 Phase shift means (piezo element) 8 Shutter 9, 109, 409, 509, 609 wavelength filters 11 Subject image reconstruction means 12 First image calculation unit 13 Second image storage unit 14 Image Combination Unit 15 monitors 20, 120, 420, 520, 620 Holographic imaging device 40 Holographic Reconstruction Device 50, 150, 450, 550, 650 Holographic imaging and reconstruction device 110a, 110b, 410a, 410b, 510, 610 polarizer 116, 416, 516, 616 SLM 517 Rotating Polarizer 603 Polarizing Beam Splitter (PBS) 618 Half-wave plate

Claims

1. A device having a first imaging function unit that captures a hologram image formed by causing incoherent light from a subject that is incident through an imaging lens and split into two systems to interfere with each other, and obtains a first image that is a reconstructed image of the subject, and a second imaging function unit that focuses a single light beam that is incident through the imaging lens from the subject, and obtains a second image that is an image of the subject simultaneously with or sequentially to the first image, an image combining unit that combines information contained in the first image and information contained in the second image to form a new image of the subject; The image combination unit is configured to identify, for each part of the subject, a predetermined area in the first image having positional information indicating the distance to the part based on the contrast level, set an area in the second image corresponding to the predetermined area in the identified predetermined area of ​​the first image, and form a new first image.

2. The incoherent digital holography imaging device described in claim 1, characterized in that the second imaging function unit is equipped with a shutter that blocks one of the two split light beams when obtaining the second image.

3. The incoherent digital holography imaging device described in claim 1 or 2, characterized in that the first imaging function unit is configured to determine position information related to the first image, which represents the distance from the imaging surface to each part of the subject, based on the contrast level of the first image when the complex amplitude distribution of the obtained hologram image is back-propagated.

4. The incoherent digital holography imaging device of any one of claims 1 to 3, characterized in that the imaging optical system in the first imaging function unit comprises a beam splitter that splits the light beam from the subject into two systems; a plane mirror that receives one of the split beams and reflects it as a plane wave; a concave mirror that receives the other of the split beams and reflects it so as to converge as a spherical wave; an imaging element that obtains a hologram image by causing the plane wave from the plane mirror and the spherical wave from the concave mirror to interfere with each other; and a wavelength filter that narrows the wavelength range of the light wave that is incident on the imaging element on a common optical path of the plane wave and the spherical wave.

5. 5. The incoherent digital holography imaging device according to claim 4, further comprising a phase shifting means for shifting either the plane mirror or the concave mirror by a predetermined phase in the optical axis direction.

6. The incoherent digital holography imaging device described in claim 4 or 5, characterized in that the imaging optical system in the second imaging function unit is configured to be at least partially shared with the imaging optical system in the first imaging function unit, and is equipped with the light beam splitting means, the concave mirror that receives the other light beam split by the light beam splitting means and reflects it to converge as a spherical wave, and an imaging element that focuses the spherical wave from the concave mirror to obtain an image of the subject.

7. the imaging optical system in the first imaging function unit and the imaging optical system in the second imaging function unit share an optical path in which a first polarizer is disposed up to a beam splitter that splits a beam from a subject, but each of the imaging optical systems is provided with an imaging element separate from the other; The light beam splitting means is a spatial light modulator, The incoherent digital holography imaging device of any one of claims 1 to 3, characterized in that a wavelength filter and a second polarizer are arranged on a common optical path of the plane wave and the spherical wave from the beam splitting means to the imaging element of the first imaging function unit so that a hologram image can be obtained at the imaging element of the first imaging function unit, and the spherical wave from the beam splitting means to the imaging element of the second imaging function unit is imaged on the imaging element of the second imaging function unit to obtain an image of the subject.

Images