JP7153524B2 - Hologram recording device and hologram reproducing device - Google Patents

Description

The present invention relates to a hologram recording apparatus and a hologram reproducing apparatus, and more particularly, a hologram recording apparatus that records a stereoscopic image or a pan-focus image by holography using incoherent light, and a hologram reproducing apparatus that reproduces the recorded information. It is about.

The technique of incoherent holography does not require a high coherence light source such as a laser, but can record a hologram of an object using a low coherence light source such as sunlight or fluorescence. In this way, incoherent holography has the potential to expand the application range of holography because it can relax the coherence condition of the light source required in conventional holography.

An example of a conventionally known incoherent holography optical system is shown in FIG. 12 (see Patent Document 1, Non-Patent Documents 1, 2, 3, 4, and 5).
Among them, in incoherent holography using a Michelson interferometer, which is a typical non-common path interferometer, shown in FIG. 802 is used to split into two light waves. One of these two split light waves is called first split light, and the other is called second split light. Of these two split beams, the first split beam is reflected by the mirror 803a, and the second split beam is reflected by the mirror 803b, which has a different radius of curvature than the mirror 803a, thereby modulating the respective phase distributions.

The two light waves respectively reflected by the mirrors 803a and 803b enter the beam splitter 802 again and are superimposed. When the optical path length difference between the two light waves is shorter than the coherence length of the light source, the first split light and the second split light interfere with each other. If the coherence length of the light source is short and no hologram is formed, a bandpass filter 804 is used to narrow the wavelength range of the light wave from the light source.

On the other hand, incoherent holography using a common optical path interferometer shown in FIG. 12B is characterized by being resistant to vibration and air disturbance because the optical system is configured with a single optical path.

In the optical system shown in FIG. 12(b), a spatially incoherent light wave propagated from an object passes through a polarizer 816a and a polarizer 816b that outputs a polarized component orthogonal to this polarizer 816a. Let That is, a light wave is considered as a superposition of two light waves having polarization components orthogonal to each other, and the respective light waves are referred to as first split light and second split light. Then, a spatial light modulator having birefringence, a diffractive optical element, a liquid crystal lens, or the like (spatial light modulator 817 in FIG. 12B) arranged between the two polarizers 816a and 816b. are used to modulate the phase distributions of the first split light and the second split light.

After that, by passing the first split light and the second split light through the polarizer 816b, the polarization states of the first split light and the second split light whose polarization states are orthogonal to each other are aligned. As a result, the first split light beam and the second split light beam interfere with each other on the imaging surface of the imaging device 815, and a self-interference hologram can be imaged, and the hologram information is recorded.

The procedure for reproducing the holograms acquired by the interferometers in FIGS. 12(a) and 12(b) is common, and a three-dimensional image of the imaged object can be obtained by applying diffraction propagation calculations in the computer. Can be reconfigured. Patent Document 1 below and Non-Patent Documents 1 and 2 below have succeeded in capturing a three-dimensional image of a three-dimensional object that emits fluorescence using the optical system described above. In Non-Patent Documents 3, 4, and 5 listed below, the optical system described above is used to successfully capture a three-dimensional image of a three-dimensional object illuminated by an arc lamp, a light-emitting diode, or sunlight.

All of the optical systems described above capture a three-dimensional image of a three-dimensional object by incoherent holography technology. An optical system for capturing an image focused over a wide range in the optical axis direction, that is, a pan-focus image is also known (see Non-Patent Documents 6 and 7 below).

FIG. 13 shows an example of an optical system for obtaining a deep focus image by incoherent holography. In this optical system, a spatially incoherent light wave propagating from an object is split into two light waves by a beam splitter 922 to obtain a first split light and a second split light, and each light wave is divided into corresponding double beams. The light is made incident on prisms 928a and 928b. These two Dove prisms 928a and 928b are arranged so that their rotational angles are relatively different by 90 degrees with the optical axis as the rotational axis. As a result, the spatial coordinates of the first split light and the second split light that have passed through the Dove prisms 928a and 928b are values rotated by 180 degrees, which is twice the above 90 degrees.

These first split light and second split light are made incident on the beam splitter 929 and superimposed on each other. The common-path interferometer in FIG. 12(b), like the Michelson interferometer in FIG. 12(a), interferes when the optical path length difference between two light waves is shorter than the coherence length of the light source. 925 can be positioned to image and record self-interference holograms. Since the hologram recorded by this optical system corresponds to a Fourier transform hologram, a deep-focus image of a three-dimensional object can be reproduced by applying the Fourier transform calculation in a computer.

Japanese Patent Publication No. 2016-533542

J. Rosen and G. Brooker, "Non-scanning motionless fluorescence three-dimensional holographic microscopy", Nature Photonics, (2008), vol. 2, pp. 190-195 N. Siegel, V. Lupashin, B. Storrie, and G. Brooker, "High-magnification super-resolution FINCH microscopy using birefringent crystal lens interferometers," Nature Photonics, (2016), vol. 10, pp. 802-808 M. K. Kim, "Full color natural light holographic camera", Optics Express, (2013), vol. 21, issue 8, pp. 9636-9642 J. Rosen and G. Brooker, "Fluorescence incoherent color holography," Optics Express, (2007) vol. 15, issue 5, pp. 2244-2250 P. Bouchal and Z. Bouchal, "Selective edge enhancement in three-dimensional vortex imaging with incoherent light", Optics Letters, (2012) vol. 37, issue 14, pp. 2949-2951 P. Potuluri, M. R. Fetterman, and D. J. Brady, "High depth of field microscopic imaging using an interferometric camera", Optics Express, (2001), vol. 8, pp. 624-630 D. Weigel, H. Babovsky, A Kiessling, and R. Kowarschik, "Aberration correction in coherence imaging microscopy using an image inverting interferometer", Optics Express, (2015), vol. 23, issue 16, pp. 20505-20520 M. Takeda, H. Ina, and S. Kobayashi, "Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry," Journal of the Optical Society of America, (1982), vol. 72, issue 1 , pp. 156-160 I. Yamaguchi and T. Zhang, "Phase-shifting digital holography", Optics Letters, (1997), vol. 22, issue 16, pp. 1268-1270

As described above, by using the incoherent holography technique, it is possible to capture either a stereoscopic image or a pan-focus image. If both the stereoscopic image and the pan-focus image can be picked up by switching freely, it is possible to easily realize various kinds of imaging according to the shooting situation, which is preferable.

However, in any of the optical systems disclosed in Patent Document 1 and Non-Patent Documents 1 to 5, it is possible to capture a stereoscopic image of a three-dimensional object, but it is not possible to capture a deep focus image. . On the other hand, according to the techniques of Non-Patent Documents 6 and 7 described above, it is possible to capture a deep-focus image of a three-dimensional object, but it is not possible to capture a stereoscopic image.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a hologram recording apparatus and a hologram reproducing apparatus that use a single optical system and are capable of switching the imaging function of a stereoscopic image and a deep-focus image according to the imaging situation.

The hologram recording device of the present invention is
light wave splitting means for splitting an incoherent light wave into two light waves consisting of a first split light and a second split light;
wavefront rotating means for relatively rotating the spatial coordinates of the wavefronts of these two split light waves;
phase distribution varying means for modulating the radius of curvature of the wavefront of at least one of the first split light and the second split light to impart a relative spherical phase distribution to the wavefronts of the two split light waves;
an optical combining means for combining the first divided light and the second divided light that have passed through the wavefront rotating means and the phase distribution varying means;
a hologram recording means for recording a hologram formed by interference between the first split light and the second split light combined by the light combining means;
It is characterized by having
Here, "the first split light and the second split light that have passed through the wavefront rotating means and the phase distribution varying means" means that "at least one of the first split light and the second split light is the It means that at least one of the first split light and the second split light passes through the phase distribution varying means".

Further, the hologram recording means comprises imaging means,
In the phase distribution varying means, by imparting a plane phase having an infinite radius of curvature to the first split light or the second split light, the imaging means can pick up a deep-focus image, and At least one of the two split lights has a spherical phase with a finite radius of curvature so that the difference between the wavefronts of the first split light and the second split light is a spherical phase with a finite radius of curvature. It is preferable that a three-dimensional image can be picked up by the image pick-up means.

Further, the rotation angle of the spatial coordinates of the wavefront of the light wave can be arbitrarily adjusted so that at least one of lateral magnification, resolution, and field of view can be changed for the pan-focus image or the stereoscopic image captured by the imaging means. is preferably configured to
Further, it is preferable that a lens is arranged on the target object side of the light wave splitting means, and the imaging surface of the imaging means is arranged at a position spaced apart by the rear focal length of the lens.

Moreover, it is preferable that the wavefront rotating means is any one of a Dove prism, a corner cube prism, a retroreflector and a rectangular prism.
Moreover, it is preferable that the phase distribution varying means is any one of a spatial light modulator having birefringence, a diffractive optical element, and a liquid crystal lens.

Further, the hologram reproducing device of the present invention is
Splitting an incoherent light wave into two light waves consisting of a first split light and a second split light, relatively rotating the spatial coordinates of the wavefronts of these two split light waves, and at least one of the wavefronts having a radius of curvature is modulated to impart a relative spherical phase distribution to the wavefronts of the two split light waves, and the two split light waves are caused to interfere with each other to form a reconstructed image on the imaging plane based on a hologram. In the hologram reproducing device to generate,
A reconstructed image is formed at a position separated from the imaging surface by a propagation distance due to diffraction propagation of the light wave, which is set based on the radius of curvature of the spherical wave associated with the spherical phase and the position of the object to be recorded. It is characterized by being

According to the hologram recording device and the hologram reproducing device of the present invention, both a stereoscopic image and a deep-focus image can be easily captured by a single device by switching the imaging function. By using this hologram recording device, the user can easily switch between stereoscopic images and deep-focus images according to the object to be photographed and the photographing conditions. can.

FIG. 1 shows a conceptual diagram for explaining the principle and effects of the hologram recording apparatus of the present invention. Note that FIG. 1 used in the following description includes portions illustrated for convenience of description, but the configuration of the present invention is not limited to this.
In this hologram recording apparatus, a spatially incoherent light wave propagating from an object 101 is split by splitting means 102 to obtain first split light 110 and second split light 111 . The light wave rotator 113 relatively rotates the spatial coordinates of the wavefronts of the first split light and the second split light by an arbitrary angle.

Furthermore, the phase distribution modulation element 112 modulates the phase distribution of the first split light or the second split light. By changing the phase distribution given to the light wave using the phase distribution modulation element 112, it is possible to switch between the imaging function of the pan-focus image and the stereoscopic image. That is, when capturing a pan-focus image, a spherical phase with an infinite radius of curvature, that is, a plane phase is input to the phase distribution modulation element 112 . At this time, the spatial coordinates of the wavefronts of the first split light 110 and the second split light 111 differ only in rotation angle. Therefore, when the first split beam 110 and the second split beam 111 are combined by the combining means 104 and the hologram generated by the mutual interference is recorded by the imaging device 105, the depth information of the object 101 to be imaged is obtained. A deep focus image can be captured without being reflected in the hologram.

On the other hand, when capturing a stereoscopic image, a spherical phase is input to the phase distribution modulation element 112 . That is, the radius of curvature of this spherical phase is not infinite, but finite.
By imparting a spherical phase to the light wave, when a hologram obtained by interfering the first split light 110 and the second split light 111 is imaged by the image sensor 105, the depth information of the object 101 to be imaged is captured by the hologram. , so that a stereoscopic image can be captured.

Further, in the hologram reproducing apparatus of the present invention, the radius of curvature of the spherical wave related to the spherical phase used when creating the hologram and the shape of the object to be recorded are used for the hologram formed and recorded on the imaging surface. By using two parameters, the position and the position, the reproduced image is formed at a position corresponding to the propagation distance of the diffraction propagation of the light wave, so the hologram stereoscopic image can be reproduced at a desired position.

1 is a conceptual diagram for explaining the principle of a hologram recording device according to an embodiment of the invention; FIG. 1 shows an optical system ((a) is an arrangement pattern 1, (b) is an arrangement pattern 2) using a Dove prism as a light wave rotator (Embodiment 1). 1 is a conceptual diagram for explaining a hologram reproducing apparatus according to an embodiment of the present invention ((a) is a diagram showing reproduction of a deep-focus image, and (b) is a diagram showing reproduction of a stereoscopic image); FIG. An optical system using a retroreflector as a light wave rotating element is shown (Embodiment 2). An optical system using a corner cube prism as a light wave rotating element is shown (Embodiment 3). An optical system using a rectangular prism as a light wave rotating element is shown (Embodiment 4). It represents a three-dimensional object to be recorded, in particular, (a) represents the positional relationship in the propagation direction, and (b) represents the object viewed from the propagation direction. 1 shows a hologram recording apparatus (an example using a Dove prism) according to a specific embodiment of the present invention. When a deep-focus image is taken, (a) represents a hologram, and (b) represents its reproduced image. When picking up a stereoscopic image, (a) represents a hologram, (b) represents a reconstructed image focused on the object 1, and (c) represents a reconstructed image focused on the object 2. It represents 10 is a graph showing the relationship between the object placement distance _zs and the reproduction distance _zr from the hologram plane. 1 shows an optical system capable of picking up a stereoscopic image, (a) showing a Michelson interferometer and (b) showing a common path interferometer. 1 shows an optical system capable of imaging a deep-focus image.

A hologram recording device and a hologram reproducing device according to embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1>
FIG. 2(a) schematically shows an optical system portion of a hologram recording apparatus according to Embodiment 1 of the present invention, using two Dove prisms 208a and 208b as light wave rotating elements. That is, in the hologram recording apparatus according to the first embodiment, the spatially incoherent light wave propagating from the object 201 is passed through the lens 216 and then split by the splitting means 202 into first split light and second split light. get the light The first split light passes through the Dove prism 208a via the mirror 203a, undergoes phase modulation when passing through the spatial light modulator 207, and reaches the beam splitter 209. FIG. On the other hand, the second split light reaches the beam splitter 209 via the mirror 203b after passing through the Dove prism 208b.
The first split light that reaches the beam splitter 209 is reflected in the direction of the image sensor 205, and the second split light that reaches the beam splitter 209 is transmitted in the direction of the image sensor 205, so that these two split lights are superimposed and captured. A hologram is formed on the imaging surface of the element 205 . A bandpass filter 204 is arranged between the beam splitter 209 and the image sensor 205 .

In the optical system of Embodiment 1, two Dove prisms 208 a and 208 b are used as the light wave rotator (wavefront rotator) 113 . The two Dove prisms 208a and 208b are arranged in a shape rotated by 90° with respect to the optical axis. The Dove prisms 208a and 208b have the effect of rotating the spatial coordinates of the light wave and also the effect of reversing the light wave in one direction. can only cancel each other out.
By relatively rotating the light waves by the light wave rotator 113 in this way, it is possible to give a shift amount in each of the in-plane x and y directions between the light waves of the two split lights. When two light waves that are given a relative amount of rotation are caused to interfere with each other, interference fringes are obtained in which the depth information of the light waves has disappeared. This interference fringe corresponds to a Fourier transform hologram, and it is possible to secure the pan-focus imaging function by calculating the Fourier transform.
In addition, by relatively rotating the light waves in this way, it is possible to freely change the spatial resolution, field of view, and magnification of the captured image without changing the lens for both deep-focus imaging and stereoscopic imaging. Become. That is, when the amount of rotation between the light waves of the two split lights changes, the x and y positions of the light waves also change, so the period of the interference fringes formed by the interference of those light waves also changes. Since the period of the interference fringes is a variable of the spatial resolution, field of view, and magnification of the pan-focus image or stereoscopic image, by giving relative rotation, the spatial resolution, field of view, and magnification can be changed without changing the configuration of the optical system. will be able to control.

Further, in the optical system of Embodiment 1, the spatial light modulator 207 that phase-modulates the light wave is used as the phase distribution modulation element (phase distribution variable means) 112 .
The spatial light modulator 207 modulates the phase distribution of the first split light or the second split light (in FIGS. 2(a) and 2(b), only the first split light is modulated). are). By changing the phase distribution given to the light wave using the spatial light modulator 207, the imaging function of the pan-focus image and the stereoscopic image can be switched.
A plane phase is input to the spatial light modulator 207 when capturing a pan-focus image. At this time, the spatial coordinates of the wavefronts of the first split light and the second split light differ only in the angle of rotation. When the hologram is recorded by the imaging element 205, a deep focus image can be captured without reflecting the depth information of the object 201, which is the imaging target, on the hologram.
On the other hand, when capturing a stereoscopic image, a spherical phase is input to the spatial light modulator 207 . That is, the radius of curvature of this spherical phase is finite.
By imparting a spherical phase to the light wave, depth information of the object 201 to be imaged is reflected in the hologram when the imaging device 205 captures the hologram obtained by interfering the first split light and the second split light. Therefore, a stereoscopic image can be captured.
In addition, as the phase distribution modulation element 112, any element such as a varifocal lens, a liquid crystal lens, or the like, which can arbitrarily change the radius of curvature of the spherical phase may be used.

Further, in the optical system of Embodiment 1, the spatially incoherent light wave propagated from the object 201 is converged or diverged using the lens 216 . This lens 216 is used to adjust the magnification of the image, and it can be configured without the lens 216 inserted, or when the lens 216 is provided, it can be configured by a combination of a plurality of lenses. is also possible.
Note that the Dove prism 208a and the spatial light modulator 207, which pass one of the split beams, may be exchanged to first modulate the phase distribution and then rotate the spatial coordinates using the Dove prism 208a.

FIG. 2(b) schematically shows a modified example of the hologram recording apparatus according to Embodiment 1 of the present invention. 100 is added to the reference numerals assigned to the respective members, and detailed description thereof is omitted.

However, the hologram recording apparatus shown in FIG. 2B is different from the hologram recording apparatus shown in FIG. I have to. In the optical system of the hologram recording apparatus shown in FIG. 2(a), it is also possible to adopt a modified example in which the Dove prism 208b through which the second split beam passes is provided not in front of the mirror 203b but in the rear. is.

By the way, in the hologram recording apparatus according to the present embodiment, the imaging device 205 is used to capture and record a hologram generated by interference between the first split beam and the second split beam. When it is necessary to acquire a hologram with a single exposure, an off-axis hologram can be obtained by adjusting the angles of the mirrors 303a and 303b of the optical system and making light obliquely enter the imaging surface of the imaging element 205. It is possible to record

Based on the Fourier fringe analysis technique disclosed in Non-Patent Document 8, the complex amplitude distribution on the hologram plane is obtained by removing unnecessary components from the off-axis hologram. In addition, if the amount of phase shift between two light waves can be changed and an increase in the number of recorded holograms is allowed, the phase shift method disclosed in Non-Patent Document 9 can be used to determine the complex amplitude distribution of the hologram plane. can be obtained.
That is, acquisition of the complex amplitude distribution on the hologram plane can be performed using either the Fourier fringe analysis method or the phase shift method.

When the coherence length of the light source is short and the optical path length difference between the two light waves is large, bandpass filters 204 and 304 are used as shown in FIGS. may be made longer to make it easier for the two light waves to interfere with each other.

In the hologram recording apparatus configured as described above, when a plane phase is input from the spatial light modulators 207 and 307, the imaging elements 205 and 305 capture and record Fourier transform holograms. As shown in FIG. 3(a), by applying a Fourier transform operation to this hologram 318a or a complex amplitude distribution obtained by applying Fourier fringe analysis or a phase shift method to this hologram 318a, a pan-focus An image (reproduced image) 317a can be reproduced. The lateral magnification of this deep-focus image 317a changes according to the arrangement of the object 201 and the parameters of the optical system. Assuming that the distance from the lens 216 to the object 201 is z _s , the focal length of the lens 216 is _fo , and the distance between the lens 216 and the image sensor 205 is z _h1 , the lateral magnification M _T is expressed by the following equation (1). be.

Here, if it is desired to keep the lateral magnification constant without depending on the arrangement distance _zs to the object 201, the imaging device 205 is arranged at the position of the focal length behind the lens 216. FIG.
That is, when z _h1 =f _o , the lateral magnification M _T is constant at 1/f _o .
When the spatial light modulator 207 inputs a spherical phase with a radius of curvature _fd when recording the hologram 318a, a hologram reflecting the depth information of the object is recorded.

ここで、ｄはレンズ２１６から空間光変調器２０７までの距離である。
また、ｚ_ｈ２は、立体像撮像時における、空間光変調器２０７と撮像素子２０５の距離であり、上記ｚ_ｈ１とこのｚ_ｈ２は、ともに光学系を構築した際に決定されるパラメータである。
このように、伝搬距離ｚ_ｒは像を再生する際の再生距離を示しており、撮影者が像を再構成する際に任意に設定する値となっている。特に、撮像対象の物体２０１の配置距離ｚ_ｓが既知で、その物体２０１に焦点が合った像を取得したい場合には、上記数式（２）～（４）で定義される値をｚ_ｒとして用いることができる。
また、上記数式（２）～（４）のパラメータのうち、ｚ_ｓは、「記録対象である物体の位置」を示すものであり、ｚ_ｓ以外のパラメータは「球面波の曲率半径」を決定するものである。したがって、光学系を構築すると、ｚ_ｓを除くすべての変数に値を代入することができ、数式（２）～（４）に基づき、物体２０１の配置距離ｚ_ｓ（mm）と再生距離ｚ_ｒ（mm）の関係は、図１１に示すグラフで表される。すなわち、ｚ_ｓが既知の場合には、記録対象である物体２０１の位置に応じ、図１３のグラフで表される関係に基づきｚ_ｒを決定することができ、焦点のあった像を再構成することができる。 On the other hand, as shown in FIG. 3(b), this hologram 318b, or the complex amplitude distribution obtained by applying the Fourier fringe analysis or the phase shift method to this hologram 318b, is diffracted and propagated over a propagation distance _zr within a computer. By calculating , an image of an arbitrary propagation plane can be reconstructed, and a stereoscopic image (reconstructed image) 317b can be reconstructed. In particular, when the arrangement distance z _s of the object 201 is known in advance and it is desired to obtain a focused image of the object with this arrangement distance z _s , the propagation distance z _r can be expressed by the following equations (2) to (4). calculated using

Here, d is the distance from lens 216 to spatial light modulator 207 .
Also, _zh2 is the distance between the spatial light modulator 207 and the imaging device 205 when picking up a stereoscopic image, and both _zh1 and _zh2 are parameters determined when the optical system is constructed.
In this way, the propagation distance _zr indicates a reproduction distance when reproducing an image, and is a value arbitrarily set by the photographer when reconstructing an image. In particular, when the arrangement distance z _s of the object 201 to be imaged is known and it is desired to acquire an image in which the object 201 is in focus, the values defined by the above formulas (2) to (4) are set to z _r can be used.
In addition, among the parameters of the above formulas (2) to (4), _zs indicates "the position of the object to be recorded", and the parameters other than _zs determine the "radius of curvature of the spherical wave". It is something to do. Therefore, when constructing the optical system, values can be substituted for all variables except z _s , and based on the formulas (2) to (4), the arrangement distance z _s (mm) of the object 201 and the reproduction distance z _r (mm) is represented by the graph shown in FIG. That is, when zs is known, _zr can be determined according to the position of the object 201 to be recorded, based on the relationship represented by the graph of FIG _. can do.

<Embodiment 2>
FIG. 4 schematically shows a hologram recording apparatus according to Embodiment 2 of the present invention, which is an equal optical path length type non-common optical path type interferometer similar to that of Embodiment 1, but FIG. While both a) and (b) are Mach-Zehnder interferometers, the second embodiment shown in FIG. 4 is a Michelson interferometer.

The optical system of the hologram recording apparatus according to the second embodiment uses a retroreflector as a wavefront rotating means.
Specifically, a spatially incoherent light wave from an object 401 is split by a beam splitter 402 to obtain first split light and second split light. The phase distribution of the light wave of one of the split lights is modulated by the spatial light modulator 407, and the spatial coordinates of the light wave of the other split light are rotated using the retroreflector 419 with respect to the light wave of the one split light. do. After that, the light waves of these two split beams that have returned to the beam splitter 402 are caused to interfere with each other, and the generated hologram is imaged by the imaging element 405 and recorded.

The optical system of the hologram recording device according to the second embodiment, like the optical system of the hologram recording device according to the second embodiment, picks up a pan-focus image when a plane phase is input to the spatial light modulator 407. , and when a spherical phase is input, a stereoscopic image can be captured. Further, the retroreflector 419 is used to rotate the spatial coordinate axes of the wavefronts of the two split beams, so that not only a stereoscopic image but also a deep focus image can be formed. A hologram reproducing apparatus for reproducing the recorded pan-focus image and stereoscopic image reproduces the holograms by the same technique as that shown in FIG.

<Embodiment 3>
FIG. 5 schematically shows a hologram recording apparatus according to Embodiment 3 of the present invention. Although the Michelson interferometer is similar to that of the second embodiment, the main difference is that a corner cube prism 519 is used as the light wave rotating element 113. Therefore, the members corresponding to the members in FIG. , 100 is added to the reference numerals given to the respective members in FIG. 4, and detailed description of the members is omitted.

In the hologram recording apparatus according to this embodiment, unlike the retroreflector 419 in the second embodiment, the solid corner cube prism 519 is used as the light wave rotating element 113, so that the wavelength width of the light wave from the light source is wide. In this case, the contrast of the hologram is lowered due to the wavelength dispersion caused by the glass material of the corner cube prism 519 . If the influence of chromatic dispersion is large, it is essential to either narrow the wavelength range of the light source with the bandpass filter 504 or to place an optical element such as a glass plate 521 for compensating the chromatic dispersion in the optical path.

The optical system of the hologram recording apparatus according to Embodiment 3, like the optical system of the hologram recording apparatus according to Embodiment 2 described above, picks up a pan-focus image when a plane phase is input to the spatial light modulator 507. , and when a spherical phase is input, a stereoscopic image can be captured. Further, the corner cube prism 519 is used to rotate the spatial coordinate axes of the wavefronts of the two split beams, so that not only a stereoscopic image but also a deep focus image can be formed. A hologram reproducing apparatus that reproduces the recorded pan-focus image and stereoscopic image reproduces the hologram by the same technique as that shown in FIG.

<Embodiment 4>
FIG. 6 schematically shows a hologram recording apparatus according to Embodiment 4 of the present invention. Although the Michelson interferometers are similar to those of Embodiments 2 and 3, the main difference is that rectangular prisms 619a and 619b are used as the light wave rotator 113. Therefore, members corresponding to the members in FIG. 4 are added by 200 to the reference numerals assigned to the respective members in FIG. 4, and detailed description of the members is omitted.

In the optical system of the hologram recording apparatus according to the fourth embodiment, similarly to the optical systems of the hologram recording apparatuses according to the second and third embodiments described above, when a plane phase is input to the spatial light modulator 607, a pan-focus image can be imaged, and when the spherical phase is input, a stereoscopic image can be imaged. Further, the rectangular prisms 619a and 619b are used to rotate the spatial coordinate axes of the wavefronts of the two split beams, so that not only a stereoscopic image but also a deep focus image can be formed. Further, the rectangular prisms 619a and 619b are used to rotate the spatial coordinate axes of the wavefronts of the two split beams, so that not only a stereoscopic image but also a deep focus image can be formed. A hologram reproducing apparatus that reproduces the recorded pan-focus image and stereoscopic image reproduces the hologram by the same technique as that shown in FIG.

<Experimental example>
A hologram recording apparatus using incoherent holography according to the present invention will be further described using experimental examples.
A three-dimensional object was taken as an object to be imaged, and a pan-focus image and a three-dimensional image of the three-dimensional object were imaged by switching with one recording device according to the experiment described below.

In this experiment, as shown in FIG. 7(a), two masks 725 and 726 arranged at a predetermined interval (here, 24 mm) were arranged with numbers "1" and "2". A three-dimensional object to be recorded was used as a whole. The numbers "1" and "2" are the object 1 (623) and the object 2 (624), respectively. The size (horizontal×vertical) of the object 1 (623) was 0.37 mm×1.31 mm, and the size (horizontal×vertical) of the object 2 (624) was 0.96 mm×1.35 mm. Also, the distance between object 1 (623) and object 2 (624) is 24 mm as described above.

A hologram relating to a three-dimensional object constructed as described above was generated by a hologram recording apparatus using a Dove prism shown in FIG. 8 and imaged.
The optical system of the hologram recording apparatus shown in FIG. 8 realizes the same function as the optical system shown in FIG. 2(a). Incidentally, as shown in FIG. 8, the three-dimensional object described above is the object 1 (623) with the number "1" and the number "1" by two light emitting diodes (center wavelength 625 nm, wavelength width 18 nm) 727a, b. Transmissive masks 725 and 726 each having the shape of the number "2", which is the object 2 (624), are illuminated, and the light wave carrying the shape information of "1" and the light wave carrying the shape information of "2" are illuminated. are combined by the beam splitter 728.

The light wave multiplexed by the beam splitter 728 passes through the polarizer 706, and its polarization direction is matched with the polarization direction of the light wave that can be modulated by the spatial light modulator 707 (orientation direction of the liquid crystal). After that, in order to prevent the generation of stray light due to the reflection of the light wave within the housing that holds the optical element, the aperture 729 is used to set the diameter of the transmitted light sufficiently smaller than the size of the beam splitter 702a. . The light wave passing through the aperture 729 passes through the lens 716 with a focal length of 200 mm, enters the beam splitter 702a, and is split into two light waves at the beam splitter 702a.

One light wave (first split light) passes through the Dove prism 708a, is transmitted through the beam splitter 702, is reflected by the mirror 703, returns to the beam splitter 702, is reflected by this beam splitter 702, and is directed to the beam splitter 709. It enters and passes through this beam splitter 709 .
The other light wave (second split light) transmitted through the beam splitter 702a is transmitted through the beam splitter 702b, and its phase distribution is modulated by a spatial light modulator (1408×1058 pixels, pixel pitch 10.4 μm) 707. Received, reflected, and returned to beam splitter 702b for further reflection. After that, the other light wave (second split light) passes through the Dove prism 708b, enters the beam splitter 709, and is reflected by the beam splitter 709. FIG.

One light wave (first split light) and the other light wave (second split light) incident on the beam splitter 709 are superimposed by the beam splitter 709 and interfere with each other, and pass through the bandpass filter 704 to the image sensor 705. A hologram is formed on the imaging surface. The formed hologram is imaged by the imaging device 705 and recorded. The imaging device 705 is composed of CMOS (10000×7096 pixels, 3.1 μm pixel pitch).
Since the two Dove prisms 708a,b described above are rotated 90° relative to each other about the optical axis, the spatial coordinates of the two light waves passing through these two Dove prisms 708a,b are 180° relative to each other. rotating.

FIG. 9A shows a hologram obtained by imaging a pan-focus image by inputting a plane phase to the spatial light modulator 707 using the hologram recording apparatus shown in FIG. FIG. 9B shows a reconstructed image obtained by applying the calculation. Object 1 (623), consisting of the number "1", and Object 2 (624), consisting of the number "2", are different masks (Mask 1 (725) and It is clear that focused images of both objects 623, 624 are obtained, although they are located on Mask 2 (726)).

Next, FIG. 10(a) shows a hologram obtained by picking up a three-dimensional image by inputting a spherical phase with a radius of curvature of 460 mm to the spatial light modulator 707 using the hologram recording apparatus shown in FIG.

In the optical system of the _hologram recording apparatus shown in FIG. The radius of curvature _{fd of the modulated spherical wave is 460 mm, and the distance zh2 between} the spatial light modulator 707 and the imaging device 705 is 270 mm.
Here, the distance z _s from the objects 1 and 2 (623, 624) to the lens 716 and the propagation distance z _r from the hologram surface to the reconstructed image derived from the above formulas (2), (3), and (4) is shown in FIG.

According to this experiment, the distances _zs from lens 716 to object 1 (623) and object 2 (624) are 200 mm and 176 mm, respectively, so that focused images of objects 623 and 624 are obtained. For this purpose, it is necessary to set the propagation distance _zr to 190 mm and 314.2 mm from the relationship shown in FIG.

Reconstructed images obtained by applying diffraction propagation calculation with propagation distances _zr of 190 mm and 314.2 mm are shown in FIGS. 10(b) and 10(c), respectively. In FIG. 10(b), object 1 (623) is focused, and in FIG. 10(c), object 2 (624) is focused, and it is clear that a stereoscopic image is obtained.

When the object 1 (623) is focused, the image of the object 2 (624) is blurred. Similarly, when the object 2 (624) is focused, the image of the object 1 (623) is blurred.
The above experiments demonstrate that the hologram recording apparatus of the present embodiment can capture a deep-focus image and a stereoscopic image by switching functions using one optical system.

The hologram recording apparatus of the present invention is not limited to the above-described embodiment, and can be modified into other various modes. For example, the configuration of the optical system of the device is not limited to that of the above embodiment.
Further, in the above embodiment, the phase distribution modulation element is arranged in one of the two split beams. A desired three-dimensional image can be picked up and recorded by imparting spherical waves having different radii of curvature to the passing split beams.
Further, in the above embodiments, the spatially incoherent light waves are converged or diverged using a lens, but the lens is not limited to having positive refractive power and may have negative refractive power. It may be a single lens or a combination lens consisting of a plurality of lenses.
Further, in the optical system of the experimental example described with reference to FIG. is introduced into the optical system on the object side. No need to insert children.

101, 201, 301, 401, 501, 601, 801, 811, 921 object 102 dividing means 104 combining means 105, 205, 305, 405, 505, 605, 705, 805, 815, 925 imaging element 110 first division Light 111 Second split light 112 Phase distribution modulation element 113 Light wave rotator 114 Spherical phase 115 Planar phase 202, 209, 302, 309, 402, 502, 602, 702, 702a, b, 709, 728, 802, 922, 929 beam splitters 203a, b, 303a, b, 703, 803a, b, 923a, b mirrors 204, 304, 404, 504, 604, 704, 804, 814, 924 bandpass filters 207, 307, 407, 507, 607, 707, 817 spatial light modulators 208a,b, 308a,b, 708a,b, 928a,b Dove prisms 706, 816a,b polarizers 216, 316, 716 lenses 317a,b reconstructed images 318a,b holograms 419 retroreflectors 519 corner cube prism 521 glass plates 619a,b right angle prism 623 object 1
624 Object 2
725 Mask 1
726 mask 2
727a,b light emitting diode 729 aperture

Claims (7)

light wave splitting means for splitting an incoherent light wave into two light waves consisting of a first split light and a second split light;
wavefront rotating means for relatively rotating the spatial coordinates of the wavefronts of these two split light waves;
phase distribution varying means for modulating the radius of curvature of the wavefront of at least one of the first split light and the second split light to impart a relative spherical phase distribution to the wavefronts of the two split light waves;
an optical combining means for combining the first divided light and the second divided light that have passed through the wavefront rotating means and the phase distribution varying means;
a hologram recording means for recording a hologram formed by interference between the first split light and the second split light combined by the light combining means;
A hologram recording device comprising: The hologram recording means comprises imaging means,
In the phase distribution varying means, by imparting a plane phase having an infinite radius of curvature to the first split light or the second split light, the imaging means can pick up a deep-focus image, and At least one of the two split lights has a spherical phase with a finite radius of curvature so that the difference between the wavefronts of the first split light and the second split light is a spherical phase with a finite radius of curvature. 2. The hologram recording apparatus according to claim 1, wherein a three-dimensional image can be picked up by said image pick-up means. The rotation angle of the spatial coordinates of the wavefront of the light wave can be arbitrarily adjusted so that at least one of lateral magnification, resolution, and field of view can be changed for the pan-focus image or the stereoscopic image captured by the imaging means. 3. The hologram recording apparatus according to claim 2, wherein the hologram recording apparatus is 4. The apparatus according to claim 2, wherein a lens is arranged on the target object side of said light wave splitting means, and an imaging surface of said imaging means is arranged at a position spaced apart by a rear focal length of said lens. hologram recorder. 5. The hologram recording apparatus according to any one of claims 1 to 4, wherein said wavefront rotating means is any one of a Dove prism, a corner cube prism, a retroreflector and a rectangular prism. 6. The hologram recording apparatus according to any one of claims 1 to 5, wherein said phase distribution varying means is any one of a spatial light modulator having birefringence, a diffractive optical element, and a liquid crystal lens. Splitting an incoherent light wave into two light waves consisting of a first split light and a second split light, relatively rotating the spatial coordinates of the wavefronts of these two split light waves, and at least one of the wavefronts having a radius of curvature is modulated to impart a relative spherical phase distribution to the wavefronts of the two split light waves, and the two split light waves are caused to interfere with each other to form a reconstructed image on the imaging plane based on a hologram. In the hologram reproducing device to generate,
A reconstructed image is formed at a position separated from the imaging surface by a propagation distance due to diffraction propagation of the light wave, which is set based on the radius of curvature of the spherical wave associated with the spherical phase and the position of the object to be recorded. A hologram reproducing device characterized by:

Images