WO2018190164A1

WO2018190164A1 - Hologram recording device and hologram manufacturing method

Info

Publication number: WO2018190164A1
Application number: PCT/JP2018/014044
Authority: WO
Inventors: 隆太朗大井; 健詞山本; 保之市橋; 奥井　誠人; 光喜涌波; ジェシージャキンボワズ
Original assignee: 国立研究開発法人情報通信研究機構
Priority date: 2017-04-11
Filing date: 2018-04-02
Publication date: 2018-10-18
Also published as: JP2018180201A; JP7037797B2

Abstract

A hologram recording device (1B) is provided with: a coherent light source (10) for emitting coherent light; a light source separation means (11) for separating the coherent light into two light paths; a first spatial light modulation means (14) for modulating cell-by-cell object light by one separated light; a second spatial light modulation means (17B) for modulating reference light corresponding to a cell-by-cell light source position by the other separated light; a recording medium moving means (18) for moving a cell to which writing is to be performed to the irradiation position of the object light and the reference light; and a hologram recording controller (20B) for performing control for irradiation with the object light and the reference light in synchronization with the movement of the cell to which writing is to be performed.

Description

Hologram recording apparatus and hologram manufacturing method

The present invention relates to a hologram recording apparatus and a hologram manufacturing method.

Conventionally, there is a holography technique as a recording / reproducing method of three-dimensional subject information. In this holography technique, light reflected from an object (object light) interferes with light (reference light) different from the object light, and fringes (interference fringes) formed by the interference are recorded on a photosensitive medium. . The photosensitive medium on which the interference fringes are recorded is called a hologram. In other words, the hologram is obtained by recording three-dimensional subject information on a two-dimensional plane.

Conventionally known analog holograms that record interference fringes on a hologram recording medium expose the entire hologram recording medium, so that an exposure power laser and an exposure time are required, and the interference fringes are extremely stationary. Vibration control technology is required. Therefore, the analog hologram becomes more difficult to manufacture as the hologram recording medium becomes larger.

In recent years, a hologram printer that records interference fringes for each minute cell called an element hologram on a hologram recording medium is known.
Such a hologram printer records interference fringes in cell units while moving an element hologram (cell) vertically and horizontally, and finally generates one large hologram.
The hologram printer only needs to have a laser power capable of exposing a minute cell. In addition, this hologram printer only sends object light as digital data from a computer to a Spatial Light Modulator (SLM), and since the distance between the SLM and the cell is usually constant, it is affected by vibration. It is difficult and does not require advanced vibration control.

As described above, there are a fringe printer and a wavefront printer as hologram printers that record interference fringes for each cell.
The fringe printer obtains the interference fringes by calculation in advance in the computer, displays the interference fringes on the SLM, and projects the reduced fringes on the hologram recording medium.
On the other hand, the wavefront printer reproduces the three-dimensional digital data (hologram data) generated in the computer by the SLM, and the obtained complex amplitude distribution (object light) and the object light guided to the hologram surface by another path Interference fringes with coherent light (reference light) are recorded on a hologram recording medium (Patent Document 1, etc.).
Since this wavefront printer records interference fringes in the thickness direction of the hologram recording medium, it is excellent in that it can also implement functions that cannot be realized by a fringe printer, such as providing a wavelength selection system during reproduction.

Japanese Unexamined Patent Publication No. 2016-212231

Since the conventional wavefront printer records the interference fringes in cell units while moving the element hologram (cell) up and down, left and right, it is necessary to irradiate the reference light with parallel light.
However, analog holograms are generally used by using a halogen lamp (point light source) as illumination light for illuminating the hologram in an indoor viewing application or the like.
Therefore, the hologram recorded by the conventional wavefront printer has a problem that the reproducibility of the object light deteriorates with the light of a commonly used light source (for example, a point light source) other than the parallel light.

Therefore, it is an object of the present invention to provide a hologram recording apparatus and a hologram manufacturing method for manufacturing a hologram capable of accurately reproducing object light according to the position of the light source of illumination light.

In order to solve the above problems, a hologram recording apparatus according to the present invention is a hologram recording apparatus that records interference fringes on a hologram recording medium in units of cells, and includes a coherent light source that emits coherent light, and two coherent lights. A light source separating means for separating the light path; a first spatial light modulating means for modulating the object light by one separated light; a second spatial light modulating means for modulating the reference light by the other separated light; and writing A recording medium moving means for moving a target cell to the irradiation position of the object light and the reference light; and a control means. The control means includes a cell position control means, a cell data display means, and a second space. And a light modulation control means.

In such a configuration, the hologram recording apparatus controls the recording medium moving unit so that the cell to be written is moved to the irradiation position by the cell position control unit. As a result, the hologram recording apparatus can record interference fringes in units of cells of a predetermined size on the hologram recording medium.
Then, the hologram recording apparatus displays the hologram data generated in advance corresponding to the cell on the first spatial light modulation unit in synchronization with the movement of the cell by the cell data display unit. As a result, the hologram recording apparatus can modulate the object light in units of cells with the one light separated from the coherent light.

In addition, the hologram recording apparatus uses the second spatial light modulation control means to synchronize with the movement of the cell, using the position of the light source during hologram reproduction as the relative position of the reference light, and the phase of the other light separated from the coherent light. The second spatial light modulation means is controlled so as to generate reference light by modulating. Thereby, the hologram recording apparatus can modulate the reference light in units of cells by the other light separated from the coherent light.
Accordingly, the hologram recording apparatus can generate a hologram using different reference light for each cell corresponding to the position of the light source at the time of hologram reproduction without using the reference light that becomes the same parallel light in the entire hologram. .

The second spatial light modulation control means may be realized by using a complex amplitude distribution obtained by modulating the reference light from the relative position of the light source using the SLM.
Further, the hologram recording apparatus may irradiate object light having different viewing angles on the same cell, and record the interference fringes by superimposing them.
Further, the second spatial light modulation control means generates the reference light by reflecting the other light separated from the coherent light in the direction of the cell to be written from the mirror moved in the relative position direction of the light source. It is good.

In order to solve the above-described problem, a hologram manufacturing method according to the present invention includes a coherent light source that emits coherent light, a light source separation unit that separates the coherent light into two optical paths, and an object using one of the separated lights. First spatial light modulation means for modulating light, second spatial light modulation means for modulating reference light with the other separated light, and a cell to be written moved to the irradiation position of the object light and the reference light A hologram recording apparatus comprising a recording medium moving means and a control means, and a hologram manufacturing method for recording interference fringes on a hologram recording medium in cell units, a cell position control step, a cell data display step, And a second spatial light modulation control step.

In this procedure, in the hologram manufacturing method, as a cell position control step, the recording medium moving means is controlled by the control means so that the cell to be written moves to the irradiation position.
In the hologram manufacturing method, as the cell data display step, the control unit displays the hologram data corresponding to the cell on the first spatial light modulation unit in synchronization with the movement of the cell. As a result, the object light is modulated in units of cells by the one light separated from the coherent light.
Then, in the hologram manufacturing method, as the second spatial light modulation control step, the control means synchronizes with the movement of the cell and uses the position of the light source at the time of reproducing the hologram as the relative position of the reference light to separate the other from the coherent light. The second spatial light modulator is controlled so as to generate the reference light by modulating the phase of the light.
As a result, the hologram manufacturing method can manufacture a hologram using reference light having relatively different irradiation directions in cell units.

The present invention has the following excellent effects.
According to the present invention, it is possible to generate a hologram by irradiating the hologram recording medium with different reference light in cell units according to the light source during hologram reproduction.
Accordingly, the present invention can generate a hologram with improved reproducibility of object light during hologram reproduction.

1 is an overall configuration diagram showing a configuration of a hologram recording apparatus according to a first embodiment of the present invention. It is a functional block diagram which shows the structure of the hologram recording control apparatus of FIG. It is a schematic diagram which shows the relationship between a hologram recording medium and a mirror. It is a flowchart which shows operation | movement of the hologram recording apparatus which concerns on 1st Embodiment of this invention. It is a whole block diagram which shows the structure of the hologram recording apparatus which concerns on 2nd Embodiment of this invention. It is a functional block diagram which shows the structure of the hologram recording control apparatus of FIG. It is explanatory drawing for demonstrating the method of calculating the complex amplitude distribution of a hologram surface. It is a flowchart which shows operation | movement of the hologram recording apparatus which concerns on 2nd Embodiment of this invention. It is a whole block diagram which shows the structure of the hologram recording apparatus which concerns on 3rd Embodiment of this invention. It is a functional block diagram which shows the structure of the hologram recording control apparatus of FIG. It is a block diagram which shows the structural example of a reduction optical system.

Hereinafter, embodiments for carrying out a hologram recording apparatus and a hologram manufacturing method according to the present invention will be described in detail with reference to the drawings.

<< First Embodiment >>
[Configuration of hologram recording apparatus]
With reference to FIG. 1, the structure of the hologram recording apparatus 1 which concerns on 1st Embodiment of this invention is demonstrated.

The hologram recording apparatus 1 records a hologram on a hologram recording medium H in units of cells EH that are rectangular areas having a predetermined size. Here, the hologram recording apparatus 1 includes a coherent light source 10, a light source separation unit 11, a mirror 12 (12 ₁ , 12 ₂ ), a half mirror 13, a first spatial light modulation unit 14, and an unnecessary light removal unit 15. And imaging means 16, second spatial light modulation means 17, recording medium moving means 18, and hologram recording control device 20. A beam expander is provided between the coherent light source 10 and the light source separation means 11 to enlarge the beam diameter of the laser light and make it parallel light, but the illustration is omitted here. In addition, a shielding plate that shields the peripheral portion so as not to irradiate the light other than the cell EH to be written on the optical paths of the object light and the reference light is provided, but the illustration is omitted here.

The coherent light source 10 emits coherent light (laser light). The coherent light source 10 can be constituted by, for example, a semiconductor laser that emits green laser light having a wavelength of 532 nm.
The coherent light source 10 emits coherent light to the light source separation unit 11. Here, the coherent light source 10 is controlled to turn on / off the emission of coherent light under the control of the hologram recording control device 20. For example, the coherent light source 10 includes a shutter (for example, an optical shutter) inside or in the vicinity of the emission port, and turns on / off the emission of coherent light according to an instruction from the hologram recording control device 20.

The light source separation unit 11 separates incident light in different directions. For example, the light source separation means 11 can be configured by a cross half mirror.
Here, the light source separation means 11 uses the light incident from the coherent light source 10 as light for generating object light via the mirrors (mirror 12 ₁ , half mirror 13) and first spatial light modulation means 14. The second spatial light modulator 17 is irradiated as light serving as reference light via a mirror (mirror 12 ₂ ).

The mirror 12 is a total mirror that totally reflects incident light. Here, the mirror 12 ₁ reflects one of the laser light separated by the light source separating means 11 to the half mirror 13. The mirror 12 ₂ reflects the other laser light separated by the light source separating means 11 to the mirror 170 of the second spatial light modulating means within 17.

The half mirror 13 reflects a part of the incident light and transmits the rest. Here, the half mirror 13 reflects the light reflected by the mirror 12 ₁ to the first spatial light modulating means 14. The half mirror 13 transmits the light reflected and modulated by the first spatial light modulator 14 and emits the light to the unnecessary light remover 15. The half mirror 13 can be composed of a polarizing beam splitter (PBS).

The first spatial light modulator (SLM) 14 modulates the light intensity distribution or phase distribution of the hologram data. The first spatial light modulator 14 can be composed of an SLM (Spatial Light Modulator).
The first spatial light modulator 14 displays hologram data input from the hologram recording control device 20 as page data, and emits light (complex amplitude distribution) modulated by the light emitted from the half mirror 13 as object light. To do.
In addition, the phase distribution or the intensity distribution of light can be modulated by using the SLM 14 that uses liquid crystal as the element, and the intensity distribution of light can be modulated by using the SLM 14 that uses the element as a DMD (Digital Mirror Device). be able to.

The unnecessary light removing unit 15 removes unnecessary light emitted from the SLM 14 together with the object light. The unnecessary light removing unit 15 allows only the first-order diffracted light that is object light among the diffracted light of the SLM 14 to pass therethrough. That is, the unnecessary light removing unit 15 removes the 0th-order diffracted light and the high-order diffracted light.
The unnecessary light removing unit 15 includes a lens 150, a shielding plate 151, and a lens 152. The

lenses

150 and 152 have the same focal length f. The lens 150 is disposed at a position separated from the SLM 14 by the focal length f, and the distance between the lens 150 and the shielding plate 151 and the distance between the shielding plate 151 and the lens 152 are the focal length f.

The lens 150 condenses the Fourier transform image (frequency distribution) of the object light transmitted through the half mirror 13 on the shielding plate 151, and is, for example, a convex lens.
The shielding plate 151 removes unnecessary light, and is a mask that shields half of the object light for performing the half zone plate processing.
The lens 152 converts a Fourier transform image (frequency distribution) of the object light that has passed through the shielding plate 151 into object light (distribution on the actual surface), and is, for example, a convex lens. Object light appears at a position separated by the focal length f of the lens 152 at the subsequent stage of the lens 152.
The object light from which unnecessary light has been removed by the unnecessary light removing means 15 is emitted to the imaging means 16.

The image forming unit 16 forms an image of light (complex amplitude distribution) emitted from the first spatial light modulation unit 14 from which unnecessary light has been removed, on the cell EH to be written on the hologram recording medium H. The imaging means 16 can be constituted by a lens (convex lens), for example. Here, when a lens having a focal length f is used as the imaging unit 16, the distance between the lens 152 and the imaging unit 16 may be 3f, and the distance between the imaging unit 16 and the hologram recording medium H may be 2f. .

The second spatial light modulation means 17 is for phase modulation of the light separated by the light source separation means 11. The second spatial light modulator 17 modulates the phase of the cell EH to be written according to the incident angle of light and emits it as reference light. Here, the second spatial light modulation unit 17 includes a mirror 170, a rotation mechanism 171, and a mirror moving unit 172.

The mirror 170 totally reflects incident light. Here, the mirror 170 is rotated by the rotation mechanism 171 of the two axes, the separated by the light source separating means 11 the laser beam reflected by the mirror 12 _2, as a reference light and reflects the cell EH. Note that the angle of the light reflection direction (reference light angle) of the mirror 170 is controlled by the rotation mechanism 171.

The rotation mechanism 171 holds the mirror 170 and rotates the mirror 170 by two rotation axes (horizontal and vertical). The rotation mechanism 171 has, for example, a gimbal structure, and the rotation drive of each axis is controlled by the hologram recording control device 20.

The mirror moving means 172 is arranged in parallel to the hologram recording medium H and moves the rotating mechanism 171 in two axial directions (horizontal direction and vertical direction). The mirror moving means 172 can be constituted by, for example, an XY stage, and the movement on the stage surface is controlled by the hologram recording control device 20.

The recording medium moving means 18 moves the hologram recording medium H, which is a target for recording interference fringes, in the horizontal direction and the vertical direction for each cell EH of the interference fringe writing unit. The recording medium moving means 18 can be constituted by, for example, an XY stage, and the movement of the stage surface is controlled by the hologram recording control device 20.

The hologram recording control device (control means) 20 controls the operation of the entire hologram recording device 1. The hologram recording control device 20 controls the recording medium moving unit 18 so that the center of the cell EH to be written is at the reference position (on the optical axis of the imaging unit 16), and the orientation of the mirror 170 is The rotation mechanism 171 and the mirror moving means 172 are controlled so that the angle of the reference light from the known illumination position (point light source position) to the cell EH is obtained.
Then, the hologram recording control device 20 displays hologram data corresponding to the cell EH on the SLM 14, opens the shutter of the coherent light source 10, generates object light and reference light, and records interference fringes in the cell EH.

Here, the configuration of the hologram recording control device 20 will be described with reference to FIG. 2 (refer to FIG. 1 as appropriate).
As shown in FIG. 2, the hologram recording control apparatus 20 includes a light source control means 21, a cell data display means 22, a second spatial light modulation control means 23, a cell position control means 24, and a synchronization means 25. Prepare.

The light source control means 21 controls ON / OFF of irradiation of the coherent light source 10. The light source control unit 21 opens and closes the shutter included in the coherent light source 10 according to an instruction from the synchronization unit 25.
Thereby, the hologram recording control apparatus 20 can irradiate the laser beam only when recording the interference fringes on the cell EH to be written on the hologram recording medium H.

The cell data display means 22 outputs hologram data to be displayed on the first spatial light modulation means (SLM) 14. The cell data display unit 22 inputs hologram data corresponding to the cell EH to be written from the outside according to an instruction from the synchronization unit 25 and outputs the hologram data to the first spatial light modulation unit (SLM) 14. The hologram data is generated by a general computer generated hologram (CGH).
Thereby, the hologram recording control apparatus 20 can output hologram data for generating object light corresponding to the cell EH to be written to the SLM 14.

The second spatial light modulation control means 23 controls the second spatial light modulation means 17. Here, the second spatial light modulation control unit 23 includes a reference light angle calculation unit 230 and a mirror driving unit 231.

The reference light angle calculation means 230 calculates the incident angle of the reference light to the cell EH to be written from the relative positional relationship between the hologram position at the time of hologram reproduction and the known illumination position (point light source position) input as light source information. Is calculated. That is, the reference light angle calculation means 230 virtually arranges the hologram recording medium H on the XY plane in the virtual three-dimensional space so that the center of the cell EH is the coordinate origin, and the same virtual three-dimensional space. The horizontal angle and the elevation angle with respect to the point light source position are calculated as the incident angle of the reference light. The reference light angle calculation unit 230 outputs the angle obtained for the calculation to the mirror driving unit 231.

The mirror driving unit 231 drives and controls the mirror 170 at a position and an angle at which the reference light is applied to the cell EH to be written at the angle calculated by the reference light angle calculating unit 230.
In other words, the mirror driving unit 231 drives the mirror moving unit 172 so that the mirror 170 is positioned in the incident angle direction of the reference light with respect to the cell EH to be written. The rotation mechanism 171 is driven so that the angle of the reflected light becomes the angle of the reference light. The mirror driving unit 231 notifies the synchronization unit 25 of the completion of driving after the driving of the mirror 170 is completed.

The cell position control means 24 drives and controls the recording medium moving means 18 so that the center of the cell EH to be written is arranged at the reference position where the object light and the reference light are irradiated. This reference position is on the optical axis of the imaging means 16.
The cell position control unit 24 controls the recording medium moving unit 18 so that the cell EH designated by the synchronization unit 25 is arranged at the reference position. After the driving is completed, the driving completion is transferred to the synchronizing unit 25. Notice.

The synchronization unit 25 controls the operation of the entire hologram recording apparatus 1 in synchronization. The synchronization means 25 instructs the cell position control means 24 to move the cell EH to be written by being instructed from outside. For example, the upper left cell of the hologram recording medium H is set as the first writing target, and the writing target is sequentially switched in the horizontal direction and the vertical direction.
Further, in synchronization with the movement of the cell EH, the synchronization unit 25 calculates the angle of the reference light to the cell EH to be written with respect to the second spatial light modulation control unit 23, and drives the mirror 170. To instruct.
The synchronization means 25 instructs the cell data display means 22 to display hologram data on the cell EH to be written in synchronization with the movement of the cell EH.

The synchronization unit 25 completes the driving of the cell EH in the cell position control unit 24, the driving of the mirror 170 in the second spatial light modulation control unit 23, and the display of hologram data in the cell data display unit 22. The light source controller 21 is instructed to open the shutter of the coherent light source 10 and irradiate the laser beam.
Thereby, the hologram recording control apparatus 20 can control the hologram recording apparatus 1 so as to record the interference fringes by irradiating the reference light from the position of the point light source for each cell of the hologram recording medium H.

Here, the relationship between the hologram recording medium H and the mirror 170 will be schematically described with reference to FIG. 3 (see FIGS. 1 and 2 as appropriate).
As shown in FIG. 3, it is assumed that the hologram recording medium H is driven on the XY plane of the XYZ coordinate system, and the center of the cell EH to be written exists at the coordinate origin. Further, it is assumed that the mirror 170 is driven on the xy plane of the xyz coordinate system whose Z coordinate is Z ₁ and parallel to the XY plane. At this time, the reference light angle calculation means 230 calculates the horizontal angle θ _V and the elevation angle θ _H with respect to the position of the point light source L from the XYZ coordinate origin.
Then, the mirror driving unit 231 moves the mirror 170 from the XYZ coordinate origin to a position (x ₁ , y ₁ ) corresponding to the horizontal angle θ _V and the elevation angle θ _H. Further, the mirror driving unit 231 controls the angle of the mirror 170 so that the reflected light of the laser beam from the mirror 170 is reflected in the direction of the center (XYZ coordinate origin) of the cell EH.
Thereby, the hologram recording apparatus 1 can record the interference fringes irradiated with the reference light from the point light source for each cell EH.

By configuring the hologram recording apparatus 1 as described above, the hologram recording apparatus 1 does not irradiate the entire hologram with parallel light having the same incident angle as reference light, but differs for each cell based on a point light source. The parallel light at the incident angle can be used as the reference light. Therefore, the hologram recording apparatus 1 can generate a hologram using the reference light in which the spherical wave from the point light source is reproduced in a pseudo manner as the entire hologram.
Accordingly, the hologram generated by the hologram recording apparatus 1 can accurately reproduce the original object light by arranging illumination as a point light source at the same position as the relative position at the time of hologram generation.

[Operation of hologram recording device]
Next, the operation (hologram manufacturing method) of the hologram recording apparatus 1 according to the first embodiment of the present invention will be described with reference to FIG. Here, it is assumed that light source information indicating the position of the point light source is set in advance in the second spatial light modulation controller 23.

First, in step S1, the hologram recording apparatus 1 moves the cell EH to be written to a reference position (writing position). That is, the hologram recording control apparatus 20 gives an instruction to move the cell EH to the reference position (writing position) from the synchronization means 25 to the cell position control means 24. Then, the cell position control means 24 drives and controls the recording medium moving means 18 to move the hologram recording medium H in the surface direction to move the cell EH to be written to the reference position (cell position control step).

In step S2, the hologram recording apparatus 1 displays hologram data corresponding to the cell EH to be written on the first spatial light modulation means (SLM) 14. That is, the hologram recording control apparatus 20 inputs hologram data corresponding to the cell EH to be written from the outside by the cell data display unit 22 according to an instruction from the synchronization unit 25 and outputs it to the SLM 14 (cell data display step). .

In step S3, the hologram recording apparatus 1 calculates the incident angle of the reference light to the writing target cell EH from the point light source position designated by the light source information. That is, the hologram recording control apparatus 20 uses the reference light from the point light source position with respect to the center direction of the cell EH to be written by the reference light angle calculation means 230 of the second spatial light modulation control means 23 according to an instruction from the synchronization means 25. Calculate the angles (horizontal angle and elevation angle).

In step S4, the hologram recording apparatus 1 moves the position of the mirror 170 and rotates the mirror 170 so that the reflected light has a position and an angle at which the reflected light becomes the reference light to the writing target cell EH. That is, the hologram recording control device 20 drives the mirror moving unit 172 to move the mirror 170 to the position corresponding to the reference light angle calculated in step S3 by the mirror driving unit 231, and drives the rotating mechanism 171. The mirror 170 is rotated in the reference light direction (second spatial light modulation control step).

Thereafter, in step S5, the hologram recording apparatus 1 irradiates the writing target cell EH with object light and reference light to record interference fringes. That is, the hologram recording control device 20 irradiates the laser beam by opening the shutter of the coherent light source 10 by the light source control unit 21 according to an instruction from the synchronization unit 25. As a result, the laser light separated by the light source separation means 11 is irradiated to the cell EH to be written as object light and reference light, respectively, and interference fringes are recorded. In addition, after the irradiation for the predetermined time for recording an interference fringe is completed, the light source control means 21 closes the shutter of the coherent light source 10, and stops irradiation of a laser beam.

In step S <b> 6, the hologram recording apparatus 1 determines whether or not recording to all the cells EH of the hologram recording medium H is completed by the synchronization unit 25.
Here, when the recording to all the cells EH is not completed (No), the hologram recording apparatus 1 returns to step S1 and continues the operation. On the other hand, when the recording to all the cells EH is completed (Yes), the hologram recording apparatus 1 ends the operation.
With the above operation, the hologram recording apparatus 1 can perform hologram recording using the reference light having a known illumination position as a point light source as a pseudo spherical wave.

<< Second Embodiment >>
[Configuration of hologram recording apparatus]
With reference to FIG. 5, the configuration of a hologram recording apparatus 1B according to the second embodiment of the present invention will be described. In the hologram recording apparatus 1 (FIG. 1), the second spatial light modulator 17 uses a pseudo spherical wave that is parallel light in cell units as reference light. However, the hologram recording apparatus 1B records interference fringes on the cell EH using light other than parallel light such as spherical waves as reference light.

As shown in FIG. 5, the hologram recording apparatus 1B includes a coherent light source 10, a light source separating unit 11, mirrors 12 (12 ₁ , 12 ₂ ), a half mirror 13 (13 ₁ , 13 ₂ ), and a first space. The light modulation means 14, the unnecessary light removal means 15, the imaging means 16 (16 ₁ , 16 ₂ ), the second spatial light modulation means 17B, the recording medium moving means 18, and the hologram recording control device 20B Prepare.
A half mirror 13 _2, the imaging unit 16 _2, other than the second spatial light modulator means 17B and the hologram recording control unit 20B structures is omitted because the same configuration as the hologram recording apparatus 1 described in FIG.

Half mirror 13 ₂ reflects a portion of incident light, but which transmits the rest. Here, the half mirror 13 ₂ reflects the light reflected by the mirror 12 ₂ to the second spatial light modulator means 17B. Further, the half mirror 13 ₂ reflects the second spatial light modulator means 17B through the modulated light is emitted to the imaging unit 16 _2. The half mirror 13 _2, it can be composed of a polarization beam splitter (PBS).

Imaging means 16 _2, the light emitted from the second spatial light modulator means 17B (complex amplitude distribution), is intended for forming a cell EH to be written in the holographic recording medium H. The imaging means 16 _2, for example, can be constituted by a lens (convex lens). Here, by the imaging means 16 _2, when using a lens of focal length f, and the distance between the SLM17B and the imaging unit 16 ₂ 2f, the distance between the imaging means 16 ₂ and the hologram recording medium H and 2f That's fine.

The second spatial light modulator (SLM) 17B modulates the light intensity distribution or phase distribution. The second spatial light modulator 17B can be composed of an SLM (Spatial Light Modulator).
The second spatial light modulator means 17B displays the page data of the complex amplitude distribution input from the hologram recording controller 20, the reference beam light modulated by the light incident (complex amplitude distribution) from the half mirror 13 ₂ To be emitted.

The hologram recording control device (control means) 20B controls the operation of the entire hologram recording device 1B. This hologram recording control device 20B controls the second spatial light modulator 17B so that the cell EH to be written is irradiated with reference light from a known light source position.
Functions other than the control of the second spatial light modulator 17B in the hologram recording control device 20B are the same as those of the hologram recording control device 20 (FIG. 1).

Here, the configuration of the hologram recording control apparatus 20B will be described with reference to FIG. 6 (refer to FIG. 5 as appropriate).
As shown in FIG. 6, the hologram recording control device 20B includes a light source control means 21, a cell data display means 22, a second spatial light modulation control means 23B, a cell position control means 24, and a synchronization means 25B. Prepare. The configuration other than the second spatial light modulation control unit 23B and the synchronization unit 25B is the same as the configuration of the hologram recording control apparatus 20 described in FIG.

The second spatial light modulation control means 23B controls the second spatial light modulation means 17B. Here, the second spatial light modulation control unit 23B includes a complex amplitude distribution calculation unit 232 and a complex amplitude distribution display unit 233.

The complex amplitude distribution calculation means 232 calculates a complex amplitude distribution (wavefront) when reference light from a known light source position reaches the hologram surface.
Specifically, the calculation method of the complex amplitude distribution calculation means 232 will be described with reference to FIG. As shown in FIG. 7, it is assumed that the xy coordinate system of the hologram recording medium H and the xy coordinate system where the point light source L exists are separated by a distance d in the same coordinate system. Further, it is assumed that representation _g of _(x 1, _{y 1)} the amplitude and phase of the point light source L in the complex. The wavelength is λ and the imaginary unit is j.
In this case, the complex amplitude distribution u (x ₂ , y ₂ ) of the cell EH to be written, which is the wavefront of the reference light on the hologram, can be expressed by the following formula (1) by the Fresnel approximation of diffraction. it can.

That is, the complex amplitude distribution calculation means 232 inputs a known point light source position as light source information, and performs the calculation of the above equation (1), whereby the complex amplitude distribution u (x ₂ ) of the reference light of the writing target cell EH. , Y ₂ ).
However, it is known that the area that can be used for the Fresnel approximation is limited, and it is preferable to change the calculation method of the complex amplitude distribution u (x ₂ , y ₂ ) according to the distance d.
Specifically, when the Fresnel approximation is used, for the shorter distance d, one side D of the opening of the cell EH that is a rectangular distribution range on the hologram surface of g (x ₁ , y ₁ ) is expressed by the following equation: (2) must be satisfied.

Therefore, when the distance d is in a range closer to the equation (2), the complex amplitude distribution calculating unit 232 uses another method such as the FDTD (Finite-difference time-domain) method to calculate the complex amplitude distribution u (x ₂ , Let y ₂ ) be obtained.
On the other hand, for the longer distance d, one side D of the opening of the cell EH that is a rectangular distribution range on the hologram plane of g (x ₁ , y ₁ ) needs to satisfy the following expression (3). is there.

Therefore, when the distance d is in a range farther than the equation (3), the complex amplitude distribution calculating unit 232 obtains the complex amplitude distribution u (x ₂ , y ₂ ) by Fraunhofer approximation. Note that the complex amplitude distribution calculation means 232 may designate a plurality of light sources as the light source information. In that case, the complex amplitude distribution calculation means 232 calculates the complex amplitude distribution of the reference light on the hologram by calculating the complex amplitude distribution u (x ₂ , y ₂ ) from each light source and obtaining the complex sum.
As a result, the complex amplitude distribution calculating means 232 can reproduce reference light from a line light source (fluorescent lamp), a plurality of point light sources (multiple light bulbs), etc., in addition to the point light source (light bulb).
The complex amplitude distribution calculation unit 232 outputs the calculated complex amplitude distribution to the complex amplitude distribution display unit 233.

The complex amplitude distribution display means 233 outputs the complex amplitude distribution to be displayed on the second spatial light modulation means (SLM) 17B. As a result, it is possible to irradiate the writing target cell EH with reference light other than parallel light according to the position and number of the light sources.

The synchronization means 25B controls the operation of the entire hologram recording apparatus 1B in synchronization. This synchronization means 25B is the same as the synchronization means 25 (FIG. 2) except for the control of the second spatial light modulation control means 23B.
The synchronization unit 25B calculates a complex amplitude distribution of the reference light to the cell EH to be written to the second spatial light modulation control unit 23B in synchronization with the movement of the cell EH, and the second spatial light modulation unit 17B is instructed to output.

The synchronization unit 25B completes the driving of the cell EH in the cell position control unit 24, the display of the complex amplitude distribution in the second spatial light modulation control unit 23B, and the display of the hologram data in the cell data display unit 22. The light source controller 21 is instructed to open the shutter of the coherent light source 10 and irradiate the laser beam.
As described above, the hologram recording control device 20B controls the hologram recording device 1B so as to record the interference fringes by irradiating the reference light from the position of the light source based on the light source information for each cell of the hologram recording medium H. be able to.

By configuring the hologram recording apparatus 1B as described above, the hologram recording apparatus 1B can generate a hologram using a spherical wave or complex reference light generated by a plurality of light sources based on light source information. it can.
Thus, the hologram generated by the hologram recording apparatus 1B can accurately reproduce the original object light by arranging one or more illuminations at the same position as the relative position at the time of hologram generation.

[Operation of hologram recording device]
Next, the operation (hologram manufacturing method) of the hologram recording apparatus 1B according to the second embodiment of the present invention will be described with reference to FIG. Here, it is assumed that light source information indicating the positions of one or more point light sources is set in advance in the second spatial light modulation control unit 23B.
Here, the operations of steps S1, S2, S5, and S6 are the same as the operations of the hologram recording apparatus 1 described with reference to FIG.

After step S2, in step S3B, the hologram recording apparatus 1B calculates a complex amplitude distribution on the hologram surface. That is, the hologram recording control device 20B calculates the complex amplitude distribution on the hologram surface from one or more point light source positions by the complex amplitude distribution calculating means 232 of the second spatial light modulation control means 23B according to an instruction from the synchronizing means 25B. To do.

In step S4B, the hologram recording apparatus 1B displays the complex amplitude distribution on the second spatial light modulator 17B. That is, the hologram recording control apparatus 20B displays the complex amplitude distribution calculated in step S3B on the second spatial light modulation unit 17B by the complex amplitude distribution display unit 233 (second spatial light modulation control step).
The subsequent operation is the same as the operation of the hologram recording apparatus 1 described with reference to FIG. 4. With the above operation, the hologram recording apparatus 1B generates a wavefront that becomes reference light from one or more known illumination positions, Hologram recording can be performed.

«Third embodiment»
[Configuration of hologram recording apparatus]
With reference to FIG. 9, a configuration of a hologram recording apparatus 1C according to the third embodiment of the present invention will be described. The hologram recording apparatus 1B (FIG. 5) performs recording once for one cell EH. On the other hand, the hologram recording apparatus 1C records a hologram using reference light having a plurality of incident angles (phase distributions) with respect to the cell EH.
As shown in FIG. 8, the hologram recording apparatus 1C is different from the hologram recording apparatus 1B (FIG. 5) only in the configuration of the hologram recording control apparatus 20C.
Therefore, only the hologram recording control device (control means) 20C will be described here.

As shown in FIG. 9, the hologram recording control device 20C includes a light source control means 21, a cell data display means 22C, a second spatial light modulation control means 23B, a cell position control means 24, and a synchronization means 25C. Prepare. Since the configuration other than the cell data display unit 22C and the synchronization unit 25C is the same as the configuration of the hologram recording control apparatus 20B described with reference to FIG.

The cell data display means 22C outputs hologram data to be displayed on the first spatial light modulation means (SLM) 14. The cell data display means 22C inputs hologram data corresponding to the cell EH to be written from the outside according to an instruction from the synchronization means 25C, and outputs it to the first spatial light modulation means (SLM) 14.
At this time, hologram data having different viewing angles are prepared as hologram data. For example, three hologram data having a viewing angle shifted every 30 ° are generated in advance.
Then, the cell data display unit 22C sequentially inputs hologram data having different viewing angles corresponding to the cell EH to be written from the outside in accordance with an instruction from the synchronization unit 25C, and outputs the hologram data to the first spatial light modulation unit (SLM) 14. To do.

The synchronization means 25C controls the operation of the entire hologram recording apparatus 1C in synchronization. This synchronization means 25C is the same as the synchronization means 25 (FIG. 2) except for the control of the cell data display means 22C and the second spatial light modulation control means 23.
The synchronization unit 25C controls the cell data display unit 22C and the second spatial light modulation control unit 23 so as to perform writing a plurality of times for one cell EH.
That is, the synchronization unit 25C instructs the cell data display unit 22C to display hologram data at one viewing angle, and instructs the second spatial light modulation control unit 23 to display a complex amplitude distribution. Then, the synchronization unit 25C performs hologram recording with object light, which is hologram data at a certain viewing angle, and reference light for each cell EH for each viewing angle.

Then, the synchronization unit 25C instructs the cell position control unit 24 to move the cell EH so that the interference fringes having different viewing angles are recorded in one cell EH, and the other cell EH is set as a writing target.
Accordingly, the hologram recording control apparatus 20C can irradiate the object light and the reference light with different viewing angles on one cell EH, and can record the interference fringes in a superimposed manner.

By configuring the hologram recording apparatus 1C as described above, the hologram recording apparatus 1C can be a complex wave generated by a spherical wave or a plurality of light sources based on the light source information, similarly to the hologram recording apparatus 1B (FIG. 5). A hologram can be generated using the reference beam. Further, holograms with different viewing angles can be recorded in multiple.

Thus, the hologram generated by the hologram recording apparatus 1C can accurately reproduce the original object light by arranging one or more illuminations at the same position as the relative position at the time of hologram generation. Further, the hologram generated by the hologram recording apparatus 1C can have a wider viewing angle than the hologram generated by the hologram recording apparatus 1B.
The operation of the hologram recording apparatus 1C (hologram manufacturing method) is the same as that of the hologram recording apparatus 1B (FIG. 5) described with reference to FIG. 8 except that multiplex recording is performed on one cell EH, and thus description thereof is omitted. .

As mentioned above, although embodiment of this invention was described, this invention is not limited to these embodiment.
Here, the imaging means 16 (16 ₁ ) is provided as means for guiding the object light to the cell EH. However, when the pixel size of the SLM 14 is several to several tens of times larger than the wavelength of the coherent light source 10, the imaging means 16 (16 ₁ ) is replaced with two imaging means (FIG. 11) having different focal lengths ( It can be replaced with a reduction optical system 30 comprising

convex lenses

31 and 32.

Here, when the focal length of the lens 152 and the imaging unit 31 is f ₁ and the focal length of the imaging unit 32 is f ₂ , the distance between the lens 152 of the unnecessary light removing unit 15 and the imaging unit 31 is 3f _1. The distance between the imaging means 31 and the imaging means 32 is 2f ₁ + 2f ₂ , and the distance between the imaging means 32 and the cell EH is 2f ₂ .
Accordingly, the reduction optical system 30 can reduce the pixel size of the SLM 14 equivalently on the surface of the cell EH at a ratio of f ₁ : f ₂ .

1, 1B, 1C Hologram recording apparatus 10 Coherent light source 11 Light source separation means 12 Mirror 13 Half mirror 14 First spatial light modulation means (SLM)
DESCRIPTION OF SYMBOLS 15 Unnecessary light removal means 16 Imaging means 17 2nd spatial light modulation means 170 Mirror 171 Rotating mechanism 172 Mirror moving mechanism 18 Recording medium moving means 20 Hologram recording control apparatus (control means)
21 Light source control means 22 Cell data display means 23 Second spatial light modulation control means 230 Reference angle calculation means 231 Mirror drive means 232 Complex amplitude distribution calculation means 233 Complex amplitude distribution display means 24 Cell position control means 25 Synchronization means

Claims

A hologram recording apparatus for recording interference fringes on a hologram recording medium in cell units,
A coherent light source that emits coherent light, a light source separation unit that separates the coherent light into two optical paths, a first spatial light modulation unit that modulates object light by one of the separated lights, and the other separated light A second spatial light modulating means for modulating the reference light, a recording medium moving means for moving the cell to be written to the irradiation position of the object light and the reference light, and a control means,
The control means includes
Cell position control means for controlling the recording medium moving means so as to move the cell to be written to the irradiation position;
Cell data display means for displaying hologram data corresponding to the cell on the first spatial light modulation means in synchronization with the movement of the cell;
Synchronously with the movement of the cell, the second spatial light modulation means generates the reference light by modulating the phase of the other light with the position of the light source at the time of hologram reproduction as the relative position of the reference light. Second spatial light modulation control means for controlling
A hologram recording apparatus comprising:
The second spatial light modulator is an SLM that generates a complex amplitude distribution that is wavefront data of the reference light,
The control means calculates a complex amplitude distribution calculating means for calculating a complex amplitude distribution in which the reference light reaches the hologram surface of the cell to be written from a relative position of the light source;
Complex amplitude distribution display means for displaying the complex amplitude distribution calculated by the complex amplitude distribution calculation means on the SLM;
The hologram recording apparatus according to claim 1, comprising:
The cell data display means sequentially displays two or more hologram data having different viewing angles in the same cell generated in advance on the first spatial light modulation means,
The complex amplitude distribution calculation means sequentially calculates the complex amplitude distribution corresponding to the viewing angle, and the complex amplitude distribution display means displays on the SLM.
The hologram recording apparatus according to claim 2, wherein interference fringes with different viewing angles are superimposed on the same cell for recording.
The second spatial light modulator includes a mirror including a rotation mechanism that reflects the other light, and a mirror moving mechanism that moves the mirror in the surface direction of the hologram recording medium,
The second spatial light modulation control means includes
Reference light angle calculating means for calculating an angle of reference light from the relative position to the irradiation position;
Mirror driving means for rotating the mirror by the rotating mechanism and moving the position of the mirror by the mirror moving mechanism so as to be the angle of the reference light calculated by the reference light angle calculating means;
The hologram recording apparatus according to claim 1, comprising:
A coherent light source that emits coherent light, a light source separation unit that separates the coherent light into two optical paths, a first spatial light modulation unit that modulates object light by one of the separated lights, and the other separated light A hologram recording apparatus comprising: a second spatial light modulating unit that modulates the reference light by: a recording medium moving unit that moves a cell to be written to an irradiation position of the object light and the reference light; and a control unit. A hologram manufacturing method for recording interference fringes on a hologram recording medium in cell units,
By the control means,
A cell position control step of controlling the recording medium moving means to move the cell to be written to the irradiation position;
A cell data display step of displaying hologram data corresponding to the cell on the first spatial light modulator in synchronization with the movement of the cell;
Synchronously with the movement of the cell, the second spatial light modulation means generates the reference light by modulating the phase of the other light with the position of the light source at the time of hologram reproduction as the relative position of the reference light. A second spatial light modulation control step for controlling
A method for manufacturing a hologram, comprising: