JP2009211761A - Light reproduction device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light reproduction device capable of reproducing a signal light from a hologram as a phase conjugation reproduced light by a coaxial recording method and capable of improving a signal-to-noise ratio (SNR) of the signal light to be reproduced. <P>SOLUTION: An optical recording medium 28 is irradiated with a reference light from a spatial light modulator 24 to generate a normal reproduction signal light and a transmission reference light. The transmission reference light is passed through a 1/4 wavelength plate 34 and reflected by a light reflection section 36M of a partial reflection mirror 36, and passed through the 1/4 wavelength plate 34 and ejected to a side of a lens 32. The transmission reference light is condensed by the lens 32 and an area of the optical recording medium 28, whereon the hologram is recorded, is thereby irradiated as a readout light. From the optical recording medium 28, the phase conjugation reproduced light and the transmission reference light are ejected. The phase conjugation reproduced light is reflected to a direction of a sensor array 40 by a polarizing beam splitter 22 and detected by a sensor array 40. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical regenerator.

  Recently, as a recording / reproducing method for holographic memory, the optical system can be greatly simplified compared to the conventional two-beam interference method, and it has the advantages of being resistant to disturbances such as vibration and easy to introduce a servo mechanism. A recording method (collinear method) has been proposed. In this collinear method, the signal light and the reference light modulated by the spatial light modulator are collected by the same lens as a common optical axis, and interference is formed by interference between the signal light and the reference light. Stripes (diffraction gratings) are recorded as holograms on the optical recording medium. By displaying the signal light pattern obtained by two-dimensionally encoding the digital data on the spatial light modulator, the digital data is superimposed on the signal light.

  By irradiating the optical recording medium on which the hologram is recorded with the reference light as the readout light, the signal light is reproduced from the recorded hologram. The superimposed digital data can be decoded from the reproduced signal light. Although the optical system of the collinear holographic memory is greatly simplified, various optical elements are used in the optical system. These optical elements cause wavefront distortion in the process of light propagation. Due to this wavefront distortion (optical aberration), the reproduced image becomes a distorted image from the data pattern at the time of recording. As a result, the signal-to-noise ratio (SNR) and bit error rate (BER) of the reproduced image are degraded.

  In order to eliminate the distortion of the reproduced image caused by the optical system, phase conjugate reproduction is effective. In phase conjugate reproduction, the same optical element is used in the recording process and the reproducing process, and the light propagation direction is reversed between the recording process and the reproducing process, so that the distortion of the wavefront received in the recording process cancels out in the reproducing process. Is done. However, in the conventional collinear method, it is difficult to realize phase conjugate reproduction due to the complexity of the reference light wavefront.

  In the reproducing apparatus for a holographic recording medium described in Patent Document 1, two types of reproducing light, that is, normal reproducing light and phase conjugate reproducing light are acquired from the same hologram by a collinear method. However, normal reproduction light and phase conjugate reproduction light are emitted in the same direction and imaged. For this reason, it is necessary to detect and decode the difference between the normal reproduced image and the phase conjugate reproduced image by the camera.

JP 2005-243116 A

  An object of the present invention is an optical reproducing apparatus capable of reproducing signal light from a hologram as phase conjugate reproduced light and improving a signal-to-noise ratio (SNR) of the reproduced signal light in a coaxial recording system. Is to provide.

  In order to achieve the above object, an optical reproducing apparatus according to claim 1 is composed of a light source that emits coherent light and a plurality of pixel portions arranged in a two-dimensional manner, and uses light incident from the light source as a display pattern. A spatial light modulator that modulates and outputs each pixel in response to the hologram, which is recorded by coaxially irradiating a signal light and a reference light onto a transmission type optical recording medium, with a spatial light modulator. Reproducing means for reproducing the first signal light from the optical recording medium by irradiating the generated linearly polarized reference light as readout light, and the emission side of the first signal light reproduced from the optical recording medium by the reproducing means The first signal light incident from the optical recording medium side and the transmitted reference light transmitted through the optical recording medium are imaged and incident from the opposite side of the optical recording medium Optical system for condensing light on the optical recording medium The optical signal is coaxially disposed on the light emitting side of the optical system, transmits or absorbs the first signal light imaged by the optical system, and changes the polarization direction of the transmitted reference light imaged by the optical system. A selective reflection means that rotates in a direction orthogonal to the polarization direction and reflects the light toward the optical recording medium, and irradiates the hologram with transmitted reference light reflected by the selective reflection means as readout light; The second signal light is reproduced from the optical recording medium.

  According to a second aspect of the present invention, there is provided the optical reproducing apparatus according to the first aspect, further comprising a photodetector for detecting the second signal light reproduced from the optical recording medium.

  According to a third aspect of the present invention, there is provided the optical reproducing device according to the first or second aspect, wherein the selective reflection means is disposed on a light incident side of the reflection plate disposed in an optical path of the transmitted reference light. And a quarter wavelength plate that is disposed in close proximity or attached in parallel with the reflecting plate.

  The invention according to each claim of the present invention has the following effects.

  According to the first aspect of the present invention, signal light can be reproduced from the hologram as phase conjugate reproduction light by the coaxial recording method, and the signal-to-noise ratio (SNR) of the reproduced signal light can be improved. There is an effect that can be done.

  According to the second aspect of the invention, there is an effect that a reproduced image without distortion can be detected by the phase conjugate reproduced light, and a hologram can be reproduced with a high SNR.

  According to the third aspect of the invention, there is an effect that the polarization direction of the transmitted reference light incident on the selective reflection means can be more reliably rotated by 90 °.

Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.
(Schematic configuration of optical recording / reproducing apparatus)
FIG. 1 is a schematic diagram showing a configuration of an optical recording / reproducing apparatus according to an embodiment of the present invention. This optical recording / reproducing apparatus is an optical recording / reproducing apparatus of “coaxial recording system (collinear system)” that irradiates an optical recording medium with a signal beam having a common optical axis and a reference light as recording light of one light beam from the same direction. It is. In the present embodiment, a “coaxial transmission type” optical recording / reproducing apparatus using a reflection type spatial light modulator (SLM) and a transmission type optical recording medium will be described.

  The optical recording / reproducing apparatus is provided with a light source 10 that oscillates laser light that is coherent light. As the light source 10, for example, a laser light source that oscillates green laser light having an oscillation wavelength of 532 nm is used. On the light exit side of the light source 10, a shutter 12 that can be inserted into or retracted from the optical path (open / close), a half-wave plate 14 that gives a half-wave optical path difference between orthogonal linearly polarized light components, and a predetermined polarization A polarizing plate 16 that transmits light in the direction, a beam expander 18 that is an expansion / collimating optical system, and a reflection mirror 20 are arranged in this order along the optical path from the light source 10 side. The shutter 12 is opened and closed by being driven by a drive device (not shown) connected to a control device (not shown) such as a computer.

  On the light reflection side of the reflection mirror 20, a polarization beam splitter 22 that reflects light having a predetermined polarization direction and transmits light having a polarization direction orthogonal thereto is disposed. When viewed from the reflection mirror 20 side, on the light reflection side of the polarization beam splitter 22, a reflection type spatial light modulator 24 that polarizes and modulates incident light for each pixel is disposed. As the reflective spatial light modulator 24, DMD (digital micro-mirror device), LCOS (liquid crystal on silicon), or the like can be used. The spatial light modulator 24 is connected to a control device (not shown) via a pattern generator (not shown).

  The pattern generator two-dimensionally encodes the digital data supplied from the control device, and generates a signal light pattern to be displayed on the spatial light modulator 24. The signal light pattern is, for example, a digital pattern in which binary digital data “0, 1” is expressed as “dark (black pixels), light (white pixels)”. In addition to the signal light pattern, the spatial light modulator 24 displays a reference light pattern. The reference light pattern is, for example, a random pattern. The spatial light modulator 24 modulates the incident laser light according to the displayed signal light pattern or reference light pattern, and generates signal light or reference light. The spatial light modulator 24 reflects the generated signal light and reference light to the polarization beam splitter 22 side.

  FIG. 2A shows an example of a recording pattern displayed on the spatial light modulator 24 during recording. As shown in FIG. 2A, the recording pattern 64 includes a signal light pattern 66 that generates signal light and a ring-shaped reference light pattern 68 that generates reference light. The signal light pattern 66 is displayed on the central portion of the spatial light modulator 24. The reference light pattern 68 is displayed on the peripheral portion of the spatial light modulator 24 so as to surround the signal light pattern. The area for displaying the signal light pattern is the signal light area, and the area for displaying the reference light pattern is the reference light area. The shape of the signal light region and the shape of the reference light region can be appropriately changed according to the recording pattern.

  FIG. 2B is a plan view showing an example of a display area set on the display surface 24 </ b> A of the spatial light modulator 24. The size and pattern arrangement of the recording pattern are set in advance according to the size of the display surface 24A and the like. For example, in the present embodiment, as shown in FIG. 2B, the display surface 24A of the spatial light modulator 24 has a circular signal light region 24S and a ring-shaped reference light surrounding the signal light region 24S. Each region 24R is disposed.

  FIG. 3 is a diagram showing an example of a reproduction pattern displayed on the spatial light modulator 24 during reproduction. As shown in FIG. 3, the reproduction pattern 70 includes a ring-shaped reference light pattern 68 that is included in the recording pattern 64 and generates reference light. That is, at the time of reproduction, a pattern is displayed only on the reference light region 24R set on the display surface 24A of the spatial light modulator 24, and the incident laser light is modulated according to the displayed reference light pattern, so that only the reference light is obtained. Is generated.

  Signal light and reference light generated by the spatial light modulator 24 are incident on the polarization beam splitter 22. A lens 26 is disposed on the light transmission side of the polarization beam splitter 22 when viewed from the spatial light modulator 24. The lens 26 Fourier-transforms the recording light and irradiates the optical recording medium 28. The focal position of the lens 26 is a condensing position where the recording light is condensed. The hologram is recorded at a focal position near the surface of the optical recording medium 28.

  A holding stage 30 that holds the optical recording medium 28 is provided on the light emitting side of the lens 26. The holding stage 30 is driven by a driving device (not shown) connected to a control device (not shown), rotates, and moves in the optical axis direction or a plane direction perpendicular to the optical axis. In the present embodiment, during recording, the holding stage 30 is moved to a predetermined position so that the vicinity of the surface of the optical recording medium 28 is the focal position of the lens 26.

  The optical recording medium 28 is an optical recording medium capable of recording a hologram by a change in refractive index due to light irradiation. Examples of such an optical recording medium 28 include an optical recording medium using a recording material such as a photopolymer material, a photorefractive material, or a silver salt photosensitive material.

  On the light transmission side of the optical recording medium 28, a lens 32, a ¼ wavelength plate 34 that gives an optical path difference of ¼ wavelength between orthogonal linearly polarized light components, and a partial reflection mirror 36 are provided from the holding stage 30 side. They are arranged in this order along the optical path. The partial reflection mirror 36 is disposed on the imaging surface of the lens 32. The quarter-wave plate 34 and the partial reflection mirror 36 function as “selective reflection means” that rotates the polarization direction of the transmitted reference light transmitted through the optical recording medium 28 by 90 ° and reflects it to the optical recording medium 28 side. . The quarter wavelength plate 34 is disposed in parallel with the partial reflection mirror 36 so that light parallel to the optical axis is incident vertically. Further, the quarter-wave plate 34 is disposed close to the partial reflection mirror 36 in order to maintain a parallel positional relationship with the partial reflection mirror 36. Alternatively, it can be integrally formed by being attached to the partial reflection mirror 36.

  A sensor array 40 is disposed on the light reflection side of the polarization beam splitter 22 as viewed from the lens 26 side. The sensor array 40 is connected to a control device (not shown). The sensor array 40 is composed of an image sensor such as a CCD or CMOS array, converts the received reproduction light (diffracted light) into an electrical signal, and outputs it to a control device (not shown).

(Partial reflection mirror configuration)
Next, the configuration of the partial reflection mirror 36 will be described. As described above, the partial reflection mirror 36 is disposed on the imaging surface of the lens 32. As will be described later, when reading reference light is irradiated onto the optical recording medium 28 during reproduction, the irradiated reference light is diffracted by the hologram when transmitted through the optical recording medium 28, and transmitted diffracted light (reproduced). Signal light) is emitted to the lens 32 side. Hereinafter, the signal light reproduced from the hologram is referred to as “reproduction light” or “reproduction signal light”. Some reference light passes through the optical recording medium 28 without being diffracted (transmitted reference light). On the imaging surface of the lens 32, the reproduction light and the transmitted reference light that have passed through the quarter-wave plate 34 are imaged.

  The partial reflection mirror 36 is configured to transmit or absorb the reproduction signal light and reflect the transmitted reference light. FIG. 4A is a plan view showing an example of the partial reflection mirror 36. The partial reflection mirror 36 is composed of a light reflection portion 36M having a rectangular shape in plan view, and an aperture 36A is formed in the central portion thereof. The aperture 36A is provided in a region where the reproduction signal light is imaged. Accordingly, the reproduction signal light passes through the aperture 36A, and the remaining transmitted reference light is reflected by the light reflecting portion 36M.

  FIG. 4B is a plan view showing another example of the partial reflection mirror 36. In this example, the partial reflection mirror 36 includes a light reflection portion 36M having a rectangular shape in plan view, and a shielding portion 36B is formed at the center thereof. The shielding part 36B is provided in a region where the reproduction signal light of the light reflecting part 36M is imaged. The shielding part 36B can be formed, for example, by laminating a material containing a light absorbing material such as a black pigment on the light reflecting part 36M. Alternatively, an absorption sheet that absorbs the reproduction light signal light is attached and provided. In this example, the reproduction signal light is absorbed by the shielding unit 36B, and the remaining transmitted reference light is reflected by the light reflecting unit 36M.

  FIG. 4C is a plan view showing still another example of the partial reflection mirror 36. In this example, the partial reflection mirror 36 is composed of a transparent substrate 36T having a rectangular shape in plan view, and a ring-shaped light reflection portion 36RM is formed in the peripheral portion thereof. The light reflecting portion 36RM is provided in a region where the transmitted reference light of the transparent substrate 36T is imaged. The transparent substrate 36T is formed in a flat plate shape using a transparent material such as glass. The light reflecting portion 36RM can be formed by, for example, depositing a reflective material such as aluminum on the transparent substrate 36T. In this example, the reproduction signal light is transmitted through the transparent substrate 36T, and the remaining transmitted reference light is reflected by the light reflecting portion 36RM.

(Hologram recording operation)
Next, the recording operation of the hologram recording / reproducing apparatus shown in FIG. 1 will be briefly described.
When recording a hologram, the shutter 12 is opened and laser light is emitted from the light source 10. At the same time, digital data is output from the control device at a predetermined timing, and a recording pattern (see FIG. 2A) is displayed on the spatial light modulator 24. Further, the holding stage 30 is moved to a predetermined position so that the vicinity of the surface of the optical recording medium 28 becomes the focal position of the lens 26. The laser light oscillated from the light source 10 passes through the shutter 12, and the light intensity and the polarization direction are adjusted by the half-wave plate 14 and the polarizing plate 16. The light that has passed through the polarizing plate 16 is converted into large-diameter parallel light by the beam expander 18 and is irradiated on the reflection mirror 20.

  The light reflected by the reflection mirror 20 enters the polarization beam splitter 22. The incident light is reflected by the polarization beam splitter 22 in the direction of the spatial light modulator 24. In the spatial light modulator 24, the laser light is polarization-modulated according to the displayed pattern, and signal light and reference light are generated. The recording light polarization-modulated by the spatial light modulator 24 is applied to the polarization beam splitter 22 and transmitted through the polarization beam splitter 22 to be converted into linearly polarized amplitude distribution. Thereafter, the recording light (that is, the signal light and the reference light) is collected by the lens 26 and irradiated onto the optical recording medium 28 simultaneously and coaxially. Interference fringes formed by interference between the signal light and the reference light are recorded on the optical recording medium 28 as a hologram at a position where the signal light and the reference light are collected.

(Reproduction operation of hologram)
When reproducing the signal light from the hologram recorded on the optical recording medium 28, the shutter 12 is opened and the laser light is emitted from the light source 10. At the same time, digital data is output from the control device at a predetermined timing, and a reference light pattern (see FIG. 3) is displayed on the spatial light modulator 24 so that only the reference light is irradiated onto the optical recording medium 28.

  The laser light oscillated from the light source 10 enters the spatial light modulator 24 in the same manner as in recording. In the spatial light modulator 24, the laser light is polarization-modulated according to the displayed pattern, and the reference light is generated. The reference light generated by being subjected to polarization modulation by the spatial light modulator 24 is applied to the polarization beam splitter 22, passes through the polarization beam splitter 22, and is converted into an amplitude distribution of linearly polarized light. Thereafter, the reference light is condensed by the lens 26 and irradiated onto the area where the hologram of the optical recording medium 28 is recorded. In other words, the optical recording medium 28 is irradiated with only reference light as readout light.

  FIG. 5 is a schematic diagram showing a stage in which normal reproduction light is reproduced. As shown in FIG. 5, the reference light applied to the optical recording medium 28 is diffracted by the hologram when passing through the optical recording medium 28, and transmitted diffracted light (normal reproduction signal light) is emitted to the lens 32 side. Is done. Some reference light passes through the optical recording medium 28 without being diffracted (transmitted reference light). The reproduction signal light and the transmitted reference light emitted from the optical recording medium 28 are converted into parallel light by the lens 32, converted from linearly polarized light to circularly polarized light by the quarter wavelength plate 34, and irradiated to the partial reflection mirror 36. The

  The reproduction signal light and the transmitted reference light are imaged on the imaging surface of the lens 32. Here, a case where the partial reflection mirror 36 shown in FIG. 4A is used will be described. The reproduction signal light imaged by the lens 32 passes through the aperture 36A. The transmitted reference light imaged by the lens 32 is reflected to the optical recording medium 28 side by the light reflecting portion 36M. Note that a sensor array 42 may be arranged on the light transmission side of the partial reflection mirror 36 as indicated by a broken line so as to detect reproduction signal light (normal reproduction light).

  For example, when the polarizing beam splitter 22 that transmits P-polarized light and reflects S-polarized light is used, the P-polarized reference light that has passed through the polarizing beam splitter 22 is irradiated onto the optical recording medium 28. From the optical recording medium 28, P-polarized reproduction signal light and transmitted reference light are emitted.

  FIG. 6 is a schematic diagram showing the stage where the phase conjugate reproduction light is reproduced. As shown in FIG. 6, the transmitted reference light reflected by the light reflecting portion 36M of the partial reflection mirror 36 is converted from circularly polarized light to linearly polarized light by the quarter wavelength plate 34, and is emitted to the lens 32 side. The transmitted transmitted reference light is collected by the lens 32 and irradiated to the area where the hologram of the optical recording medium 28 is recorded. That is, the optical recording medium 28 is irradiated with transmitted reference light as readout light. Since the spatial frequency of the transmitted reference light is the same as the reference light used during recording, it is possible to reproduce the signal light.

  The transmitted reference light applied to the optical recording medium 28 is diffracted by the hologram when transmitted through the optical recording medium 28, and transmitted diffracted light (reproduced signal light by phase conjugate reproduction) is emitted to the lens 26 side. Hereinafter, the reproduction signal light by the phase conjugate reproduction is referred to as “phase conjugate reproduction light”. Some reference light passes through the optical recording medium 28 without being diffracted. The phase conjugate reproduction light and transmitted reference light emitted from the optical recording medium 28 are converted into parallel light by the lens 26 and enter the polarization beam splitter 22. The incident light is reflected in the direction of the sensor array 40 by the polarization beam splitter 22.

For example, when using a polarization beam splitter 22 that transmits P-polarized light and reflects S-polarized light,
The P-polarized transmitted reference light emitted from the optical recording medium 28 passes through the quarter-wave plate 34, is reflected by the light reflecting portion 36M by the partial reflection mirror 36, and passes through the quarter-wave plate 34 again. Conversion from P-polarized light to S-polarized light. The transmitted reference light converted into S-polarized light is applied to the optical recording medium 28 as readout light. From the optical recording medium 28, S-polarized phase conjugate reproduction light and transmitted reference light are emitted. The S-polarized phase conjugate reproduction light and the transmitted reference light are converted into parallel light by the lens 26 and reflected by the polarization beam splitter 22 in the direction of the sensor array 40.

  The sensor array 40 converts the received phase conjugate reproduction light and transmitted reference light into electrical signals and outputs them. That is, the sensor array 40 captures a reproduced image formed on the light receiving surface, and outputs image data of the captured reproduced image to a control device (not shown). Based on this image data, the data superimposed on the reproduction signal light is decoded from the phase conjugate reproduction light. In the sensor array 40, it is preferable to perform oversampling in which one pixel of signal light data is received by a plurality of light receiving elements. For example, 1-bit data is received by four (2 × 2) light receiving elements.

  The phase conjugate reproduction light propagates in the opposite direction on the same optical path as the signal light at the time of recording. For this reason, the wavefront distortion received in the recording process is canceled in the reproduction process, and the signal light has a wavefront distortion smaller than that of normal reproduction light. In the present embodiment, the phase conjugate reproduction light is emitted in a direction different from that of the normal reproduction light, so that the phase conjugate reproduction light can be detected separately from the normal reproduction light. By reproducing using this phase conjugate reproduction light, the distortion of the reproduction image formed on the sensor array 40 is reduced, and the SNR and BER of the reproduction signal are improved.

  Further, also during hologram recording, phase conjugate reproduction light is generated by the transmitted reference light. The phase conjugate reproduction light is detected by the sensor array 40 to obtain the signal light intensity (diffracted light intensity), and the diffraction efficiency of the recorded hologram can be calculated from the obtained signal light intensity and the known reference light intensity. . Therefore, during recording, it is possible to monitor the phase conjugate reproduction light and control the exposure time so that the diffraction efficiency becomes a desired magnitude.

It is the schematic which shows the structure of the optical recording / reproducing apparatus which concerns on embodiment of this invention. (A) is a figure which shows an example of the pattern for recording displayed on a spatial light modulator at the time of recording. (B) is a top view which shows an example of the display area set to the display surface of a spatial light modulator. It is a figure which shows an example of the pattern for reproduction | regeneration displayed on the spatial light modulator 24 at the time of reproduction | regeneration. (A)-(C) are top views which show an example of a partial reflection mirror. It is the schematic which shows the step in which normal reproduction | regeneration light is reproduced | regenerated. It is the schematic which shows the step in which phase conjugate reproduction light is reproduced.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light source 12 Shutter 14 1/2 wavelength plate 16 Polarizing plate 18 Beam expander 20 Reflecting mirror 22 Polarizing beam splitter 24 Spatial light modulator 24R Reference light area 24S Signal light area 24A Display surface 26 Lens 26 Spatial light modulator 28 Optical recording Medium 30 Holding stage 32 Lens 34 1/4 wavelength plate 36 Partial reflection mirror 36A Aperture 36B Shielding part 36T Transparent substrate 36M Light reflection part 36RM Ring-shaped light reflection part 40 Sensor array 42 Sensor array 64 Recording pattern 66 Signal light pattern 68 Reference light pattern 70 Reproduction pattern

Claims (3)

A light source that emits coherent light, and a spatial light modulator that is configured by a plurality of pixel units arranged in a two-dimensional shape and that modulates and outputs light incident from the light source for each pixel according to a display pattern The optical recording is performed by irradiating a hologram, which is recorded by coaxially irradiating signal light and reference light on a transmission type optical recording medium, as readout light with linearly polarized reference light generated by a spatial light modulator. Reproducing means for reproducing the first signal light from the medium;
The first signal light incident from the optical recording medium side and the transmitted reference light transmitted through the optical recording medium are coaxially arranged on the emission side of the first signal light reproduced from the optical recording medium by the reproducing means. And an optical system for condensing the light incident from the opposite side of the optical recording medium on the optical recording medium,
It is coaxially arranged on the light emitting side of the optical system, transmits or absorbs the first signal light imaged by the optical system, and changes the polarization direction of the transmitted reference light imaged by the optical system. Selective reflection means for rotating in a direction orthogonal to the polarization direction and reflecting to the optical recording medium side;
With
Irradiating the hologram with transmission reference light reflected by the selective reflection means as readout light to reproduce second signal light from the optical recording medium;
An optical regenerator.   The optical reproducing apparatus according to claim 1, further comprising a photodetector that detects the second signal light reproduced from the optical recording medium.   The selective reflection means includes: a reflection plate disposed in the optical path of the transmitted reference light; and a quarter-wave plate disposed in close proximity to or attached to the light incident side of the reflection plate in parallel with the reflection plate. The optical regenerator according to claim 1, wherein the optical regenerator is configured.