WO2012032600A1

WO2012032600A1 - Optical information record-playback device and optical information record-playback method

Info

Publication number: WO2012032600A1
Application number: PCT/JP2010/065274
Authority: WO
Inventors: 岡野　英明; 渡部　一雄; 小川　昭人; 隆碓井
Original assignee: 株式会社東芝
Priority date: 2010-09-07
Filing date: 2010-09-07
Publication date: 2012-03-15

Abstract

An optical information record-play device comprises a first controller unit, a reflector element, a second controller unit, and an image capture unit. The first controller unit controls a recording medium, whereon information is recorded as a hologram by interference between an information beam which includes the information that is recorded and which is emitted by a coherent light source and a reference beam having the same wavelength as that of the information beam, to rotate in a constant direction in a first period. The reflector element reflects the reference beam that passes through the recording medium. The second controller unit controls the reflector element to rotate such that an angle of incidence of a reflected reference beam that is reflected from the reflector element to the recording medium is constant in a second period. The image capture element captures a playback beam of the reflected reference beam passing through the recording medium in a third period within the second period.

Description

Optical information recording / reproducing apparatus and optical information recording / reproducing method

Embodiments described herein relate generally to an optical information recording / reproducing apparatus and an optical information recording / reproducing method for recording and reproducing information as a hologram.

Optical information recording media represented by CDs (Compact Discs), DVDs (Digital Versatile Discs), BDs (Blu-ray Discs), etc. have hitherto been used mainly for shortening the wavelength of laser light and the numerical aperture (NA) of objective lenses. The increase corresponds to the increase in recording density. However, all of them are said to be approaching the limits due to technical reasons and the like, and an increase in the recording transfer rate by other means or methods is desired.
In recent years, volume recording type high-density recording (hereinafter referred to as “HDS: Holographic Digital Storage”) using a hologram and an HDS recording / reproducing apparatus are being developed. In contrast to the so-called surface recording method, in which recording marks are recorded on the recording surface, such as a DVD, the hologram optical disk is a volume recording method capable of recording in the thickness direction of the information recording layer. Large recording density can be obtained.
One method for increasing the recording density of HDS is an angle multiplex recording method. This angle multiplex recording method is a method that has not been seen in conventional CDs or DVDs, and is an important recording method in the two-beam interference method. The two-beam interference method is a two-dimensional bar generated at an interference position between information light that holds information to be recorded and reference light that has the same wavelength as the information light and is generally generated from the same light source. In this method, information expressed by code-like interference fringes (hereinafter referred to as page data) is recorded on an information recording layer of an optical information recording medium. In addition, when reproducing page data from an angle-multiplexed optical information recording medium, the optical information recording / reproducing apparatus can be miniaturized by using a technique called phase conjugate reproduction.

US Patent Application Publication No. 2006/0279823 JP 05-165390 A

However, when reproducing the data recorded by the two-beam interference method, the laser light must be incident on the optical information recording medium at the same angle as that at the time of recording. The angle accuracy with respect to the information recording medium is required to be very high. For example, when angle multiplex recording is performed by changing the angle of the optical information recording medium, if the multiplex angle interval is 0.1 degrees or less, the angle accuracy is desirably 0.025 degrees or less. Further, in order to perform angle multiplex recording, it is necessary to intermittently perform a rotation operation and a stop operation. Since the control time such as rotation and stop in this case directly affects the data transfer rate, it is necessary to rotate as fast as possible and stop as fast as possible. However, since the optical information recording medium is relatively large and heavy, and the recording medium itself does not have much rigidity, it is very difficult to satisfy all of the angular accuracy, rotation, and stationary speed.
The present disclosure has been made to solve the above-described problem, and an object thereof is to provide an optical information recording / reproducing apparatus and an optical information recording / reproducing method capable of increasing a data transfer rate during phase conjugate reproduction. To do.

The optical information recording / reproducing apparatus according to the present embodiment includes a first control unit, a reflective element, a second control unit, and an imaging unit. The first control unit records the information as a hologram when information light including information to be recorded emitted from a coherent light source interferes with reference light having the same wavelength as the information light. The recording medium is controlled to rotate in a certain direction for the first period. The reflective element reflects the reference light transmitted through the recording medium. The second control unit controls the reflection element by rotating the reflection element so that an incident angle of the reflected reference light reflected by the reflection element to the recording medium is constant for a second period. An imaging part images the reproduction | regeneration light which the said reflected reference light permeate | transmitted the said recording medium in the 3rd period in the said 2nd period.

1 is a block diagram showing an optical information recording / reproducing apparatus according to a first embodiment. The figure which shows the optical information recording and reproducing apparatus at the time of recording and reproducing. FIG. 5 is a diagram illustrating an example of the operation of the phase conjugate reproducing mirror according to the first embodiment. The figure which shows the relationship between the incident angle to the optical information recording medium of reference light, and time. FIG. 6 is a diagram illustrating an example of a phase conjugate reproducing mirror according to a modification of the first embodiment. The figure which shows the phase conjugate reproduction | regeneration at the time of using a galvanometer mirror.

Hereinafter, an optical information recording / reproducing apparatus and an optical information recording / reproducing method according to the present embodiment will be described in detail with reference to the drawings. Note that, in the following embodiments, the same reference numerals are assigned to the same operations, and duplicate descriptions are omitted as appropriate.
In the present embodiment, a two-beam optical system is used, in which the information light and the reference light are incident so as to interfere with each other in the information recording layer in the optical information recording medium via separate objective lenses. To do.

(First embodiment)
An optical information recording / reproducing apparatus according to a first embodiment will be described with reference to FIG.
An optical information recording / reproducing apparatus 100 according to the first embodiment includes a laser light source 101,

shutters

102 and 104,

polarization beam splitters

103 and 106,

relay lenses

105, 108, and 114, a spatial light modulator 107, an aperture 109, and an objective lens. 110, half-

wave plates

111 and 116,

reflection mirrors

112 and 113, a system controller 115, and an actuator 116. Information is recorded on the optical information recording medium 150 using the optical information recording / reproducing apparatus 100. The system controller 115 and the actuator 116 are also collectively referred to as a first control unit.

In the optical information recording medium 150, a photopolymer is sandwiched by a glass substrate or the like with a thickness of 0.2 mm to 2.0 mm. Thereby, an information recording layer is formed on the optical information recording medium 150. When light strikes this information recording layer, the refractive index of that portion changes. Thereby, as a result of the two-beam interference between the information light and the reference light, the light intensity distribution is written as a change in the refractive index due to the interference fringes. That is, information is recorded on the optical information recording medium 150 as this refractive index change.
The laser light source 101 is a light source that emits laser light for recording and reproduction, and generally uses a combination of a green or blue-violet semiconductor laser and an external resonator (not shown) for stabilizing the wavelength. Note that the laser light source 101 may be a light source that emits laser light such as other wavelengths or a so-called DFB laser, SHG laser, solid-state laser, and gas laser.
The

shutters

102 and 104 open or close to allow light to pass or block light.
Polarization beam splitters (hereinafter also referred to as PBSs) 103 and 106 split the laser light into two light beams. Note that the light beams divided by the PBSs 103 and 106 become S-polarized light and P-polarized light whose polarization directions are different from each other by 90 degrees.
The

relay lenses

105, 108, and 114 are a combination of two or more lenses, and the beam diameter is enlarged to be parallel light.

The spatial light modulator 107 is, for example, a ferroelectric reflective liquid crystal display device (FLCOS), a transmissive liquid crystal display device, a DMD (digital micromirror device), and the like, and spatially modulates laser light to generate a page. Information light carrying data is generated.
The aperture 109 is installed at a place where the light incident on the relay lens 108 is once condensed before passing through the relay lens 108.
The objective lens 110 is used to collect information light on the optical information recording medium 150.
The half-

wave plates

111 and 116 convert the polarization of light. Specifically, mutual conversion is performed from S-polarized light to P-polarized light and from P-polarized light to S-polarized light.
The reflection mirrors 112 and 113 reflect light.
The system controller 115 generates a control signal that controls the operation of the actuator 116.
The actuator 116 receives a control signal from the system controller 115 and controls driving of the optical information recording medium 150 according to the control signal. Specific operation of the actuator 116 will be described later.

<Information recording method>
Next, a method for recording information on the optical information recording medium 150 by the optical information recording / reproducing apparatus 100 will be described.
Parallel light generated from the laser light source 101 passes through the shutter 102 and enters the polarization beam splitter 103. The incident parallel light is split into S-polarized light and P-polarized light by the polarization beam splitter 103. S-polarized light is reflected by the polarization beam splitter 103 and used as information light, and P-polarized light is transmitted and used as reference light.
The reflected S-polarized light passes through the shutter 104 and enters the relay lens 105. In the relay lens 105, the beam diameter of the information light is expanded so that the S-polarized light is incident on the spatial light modulator 107 with a certain degree of uniform intensity. After that, the information light whose beam diameter has been enlarged is reflected by the PBS 106 and enters the spatial light modulator 107, and is polarization-modulated by the spatial light modulator 107 with page data. Specifically, the OFF bit is output as S-polarized light, and the ON bit is modulated into P-polarized light.
When the information light modulated by the spatial light modulator 107 passes through the PBS 106, the information light is amplitude-modulated by transmitting the ON bit and reflecting the OFF bit. The beam diameter of the amplitude-modulated information light is adjusted by the relay lens 108 in accordance with the incident diameter of the objective lens 110.

In the relay lens 108, an aperture 109 is once installed at a place where information light is once condensed. The place where the information light is collected is the Fourier transform plane of the intensity distribution in which the information light is modulated by the spatial light modulator 107 and the PBS 106. The Fourier transform image of the information light has a conjugate relationship with the information light at the condensing position in the vicinity of the optical information recording medium 150. Depending on the size of the aperture 109, the Fourier transform image of the information light near the position incident on the optical information recording medium 150 is obtained. The size of the information light is determined. When recording information on the optical information recording medium 150, the information light in the vicinity of the optical information recording medium 150 can be taken into consideration if recording is performed at a step interval that is also parallel to the medium plane of the optical information recording medium 150. The smaller the size is, the smaller the step can be recorded, and the higher the recording density is. Therefore, it is desirable to make the size of the aperture 109 as small as possible within a range where a reproduced image acceptable by the system can be obtained.
The information light that has passed through the relay lens 108 enters the half-wave plate 116 and is converted from P-polarized light to S-polarized light. The information light converted into S-polarized light is incident on the objective lens 110 and given a lens power, and is condensed on the optical information recording medium 150. Note that the condensing position of the information light is not limited to the inside of the optical information recording medium 150 but may be outside the optical information recording medium 150.

On the other hand, the reference light transmitted through the PBS 103 is converted into S-polarized light by the half-wave plate 111. The reference light converted to S-polarized light is reflected by the reflection mirror 112 and the reflection mirror 113 and enters the relay lens 114. The incident reference light is converted by the relay lens 114 into a beam diameter that is substantially the same as the beam diameter of the information light on the optical information recording medium 150. Thereafter, the reference light is incident on the same position as the position of the optical information recording medium 150 on which the information light is incident. At this time, the information light and the reference light interfere to generate interference fringes, and the interference fringes are written in the information recording layer of the optical information recording medium 150 as a refractive index change. When the information light condensing position is outside the optical information recording medium 150, interference fringes are generated by the reference light before (converging light) or after (diverging light) the information light condensing position, It is also possible to record information as a change in refractive index in the information recording layer.

Here, an xyz orthogonal coordinate system fixed to the information recording layer of the optical information recording medium 150 is considered. Using the recording spot on the medium surface of the information recording layer by the information light and the reference light as the origin, the z-axis is perpendicular to the thickness direction of the optical information recording medium 150 (that is, the direction perpendicular to the medium surface), that is, information An x-axis and a y-axis perpendicular to each other are taken in the surface direction of the recording layer.
When performing angle multiplex recording, the optical information recording / reproducing apparatus 100 according to the present embodiment performs multiple recording of θy while changing the angle by rotating the optical information recording medium 150 around the y axis (around the in-plane axis). Do. Note that θy is a unit angle for rotating the optical information recording medium 150 in angle multiplexing recording. Specifically, the system controller 115 operates the actuator 116 to rotate the optical information recording medium 150 about the y axis by θy steps (Δθy) (hereinafter referred to as θy rotation), and refers to the information light at each θy step. Information is recorded by simultaneously irradiating the optical information recording medium 150 with light. By rotating θy, the relative angle between the information light and the reference light and the optical information recording medium 150 changes, and different page data is recorded.
In this embodiment, θy multiplex recording is performed, but the present invention is not limited to this. For example, θz multiplex recording may be performed in which information is recorded while the optical information recording medium 150 is rotated by θz steps (Δθz) around the z axis (hereinafter referred to as θz rotation). Further, a recording method using both θy multiplex recording and θz multiplex recording may be employed. Further, the θy step and the θz step need not always be constant, and the step width may be changed according to the incident angle of the reference light.

<Information playback method>
Next, the optical information recording / reproducing apparatus 200 during information reproduction will be described with reference to the block diagram of FIG.
Here, it is assumed that page data is recorded by the angle multiplex recording method. In the angle multiplexing recording method, there are a case where the angle of the reference light incident on the optical information recording medium is changed and a case where the angle of the optical information recording medium itself is changed. In the latter case, when the page data recorded in a multiplexed manner is changed by changing the angle of the optical information recording medium, the angle of the optical information recording medium is controlled so that the angle is the same as the recorded page data. When the reproduction stops at a position where there is no problem in reproduction, page data is reproduced by reference light reflected by the mirror and re-entered on the optical information recording medium (hereinafter referred to as reflected reference light). Subsequently, the optical information recording medium is controlled so as to have an angle at which the adjacent page is recorded. Similarly, when the page is stopped at a position where there is no problem in reproducing the page data, the adjacent page data is reproduced.

In addition to the configuration of the optical information recording / reproducing apparatus 100 shown in FIG. 1, the optical information recording / reproducing apparatus 200 includes a quarter-wave plate 201, a phase conjugate reproducing mirror 202, a phase conjugate reproducing mirror control unit 203, an actuator 204, And an imaging unit 205. The phase conjugate reproduction mirror control unit 203 and the actuator 204 are collectively referred to as a second control unit.
The quarter wave plate 201 converts the polarization of the reference light.
The phase conjugate reproduction mirror 202 is, for example, a galvanometer mirror, and reflects the reference light so that the phase of the reference light is conjugate.
The phase conjugate reproduction mirror control unit 203 generates a control signal for operating the actuator 204.
The actuator 204 receives a control signal from the phase conjugate reproduction mirror control unit 203 and controls the angle of the phase conjugate reproduction mirror 202.
The imaging unit 205 is a light receiving element configured by, for example, a CMOS sensor, and images page data recorded on the optical information recording medium 150.

Subsequently, a basic information reproducing operation of the optical information recording / reproducing apparatus 100 according to the first embodiment will be described.
Although not shown here, a medium moving mechanism that rotates the optical information recording medium 150 by θy rotation or scans in the xy plane may be included. Further, although not shown, a drive control unit that controls the medium moving mechanism or a signal processing unit that processes the output of the imaging unit 205 may be included.
The parallel light emitted from the laser light source 101 passes through the shutter 102 and enters the PBS 103. In the PBS 103, S-polarized light is reflected and P-polarized light is transmitted. Here, the S-polarized light is shielded by closing the shutter 104. On the other hand, P-polarized light is used as reference light. The transmitted reference light is converted to S-polarized light by the half-wave plate 111, reflected by the reflection mirror 112 and the reflection mirror 113, and enters the relay lens 114. The reference light is enlarged or reduced to a desired beam diameter by the relay lens 114 and enters the optical information recording medium 150.

The reference light incident on the optical information recording medium 150 passes through the optical information recording medium 150, passes through the quarter-wave plate 201, and is reflected by the phase conjugate reproducing mirror 202. The reflected reference light from the phase conjugate reproducing mirror 202 is again transmitted through the quarter-wave plate 201 and converted to P-polarized light.
The reference light converted into the P-polarized light is transmitted again through the optical information recording medium 150. At this time, the incident light to the optical information recording medium 150 is adjusted to be equal to that at the time of recording, and the reproduction light is reproduced. Since the reference light is P-polarized light, the reproduction light is also P-polarized light. The reproduction light passes through the objective lens 110, passes through the half-wave plate 116, is converted into S-polarized light, the beam diameter is enlarged or reduced by the relay lens 108 and the aperture 109, and is reflected by the PBS 106. Thereafter, the reproduction light is incident on the imaging unit 205 and picked up, and reproduced page data is acquired.

Next, a method for reproducing multiplexed data by changing the angle of the optical information recording medium 150 about the y-axis center will be described with reference to FIGS.
FIG. 3 is a diagram showing an angle change of the reflected reference light from the phase conjugate reproduction mirror 202 and a time series of the rotation operations of the optical information recording medium and the phase conjugate reproduction mirror 202. From FIG. 3A to FIG. 3C, when reproducing page 1 on which information is recorded with the incident angle of the reference light to the optical information recording medium 150 being θy1, FIG. 3D to FIG. Up to f) is the case where the page 2 on which information is recorded with the incident angle of the reference light to the optical information recording medium 150 being θy2 is reproduced.

As shown in FIGS. 3A to 3F, the optical information recording medium 150 rotates in a certain direction around the y axis (clockwise in this case) while keeping the angular velocity constant. When the incident angle of the reference light on the optical information recording medium 150 approaches the incident angle θy1 at which the page 1 is recorded, the phase conjugate reproduction mirror 202 is controlled so that the reflected reference light enters the optical information recording medium 150. Rotate so that the angle is θy1. As a specific example, the phase conjugate reproduction mirror 202 is rotated in the same direction as the optical information recording medium 150 at an angular velocity that is half the angular velocity at which the optical information recording medium 150 rotates, and the reflected reference light from the phase conjugate reproduction mirror 202 is reflected. The incident angle θy1 to the optical information recording medium 150 can be kept constant.
When the optical information recording medium 150 continues to rotate, the incident angle of the reflected reference light to the optical information recording medium 150 approaches from θy1 to θy2. When approaching θy2, page jump as shown in FIG. 3C to FIG. 3D is performed. Specifically, the phase conjugate reproducing mirror 202 rotating so that the incident angle of the reflected reference light to the optical information recording medium 150 is constant at θy1 is reversely rotated as shown in FIG. Then, the phase conjugate reproduction mirror 202 is controlled so that the incident angle of the reflected reference light to the optical information recording medium 150 becomes θy2. Thereafter, as shown in FIGS. 3E and 3F, the phase conjugate in the same direction as the optical information recording medium 150 so as to keep the incident angle θy2 of the reflected reference light to the optical information recording medium 150 constant. The reproduction mirror 202 is rotated.

Next, the time change of the incident angle of the reference light to the optical information recording medium 150 and the incident angle of the reflected reference light to the optical information recording medium 150 from FIG. 3A to FIG. Shown in
(A) to (f) in FIG. 4 correspond to the time series from FIG. 3 (a) to FIG. 3 (f), respectively.
An angle 401 and an angle 402 are incident angles of the reflected reference light to the optical information recording medium 150. The angle 401 indicates the incident angle θy1 and the angle 402 indicates the incident angle θy2. An angle 403 indicates an incident angle of the reference light to the optical information recording medium 150. It is assumed that a page jump occurs between (c) and (d). A period 404 and a period 405 indicate page data read periods for page 1 and page 2, respectively.
Since the optical information recording medium 150 rotates continuously in a certain direction, the angle 403 increases in proportion to time. Accordingly, by controlling the rotation of the phase conjugate reproduction mirror 202, the incident angle of the reflected reference light to the optical information recording medium 150 is kept constant. Specifically, as indicated by the

angles

401 and 402, the incident angle of the reflected reference light to the optical information recording medium 150 is maintained at θy1 during the period from (a) to (c), and from (d) to (f ) Until θy2. Therefore, during the period in which the incident angle of the reflected reference light to the optical information recording medium 150 is constant, the reproduction light of the page is imaged by the imaging unit 205 in the

periods

404 and 405, and the recorded page data is acquired respectively. Can do.

Note that the readout period (period 404, period 405) is set to a period in which the total luminance of the reproduction light of the page is equal to or higher than the threshold in this embodiment, but is not limited to this, and the optical information of the reflected reference light It is sufficient that the phase conjugate reproduction mirror 202 can be controlled so that page data can be reproduced, for example, the incident angle to the recording medium 150 is within a threshold value.

Since the optical information recording medium 150 is a relatively large medium, it is difficult to quickly perform control such as stop or start of rotation. Therefore, by controlling the rotation of an element smaller than the optical information recording medium 150 such as the phase conjugate reproducing mirror 202, the rapid rotation stop and start of the optical information recording medium 150 can be easily performed.

According to the first embodiment described above, a relatively large optical information recording medium is rotated with a constant angular velocity in a certain direction, and the rotation of the phase conjugate reproducing mirror having a smaller element configuration than the optical information recording medium. By controlling this, it is possible to reduce the load on the drive mechanism. Furthermore, since control such as rotation stop or reverse rotation of the phase conjugate reproduction mirror is easier than controlling the optical information recording medium, angle accuracy and control speed during phase conjugate reproduction can be improved. It is possible to increase the data transfer rate at the time of reproducing information recorded by angle multiplexing.

(Modification of the first embodiment)
In the first embodiment, assuming that the mirror surface of the phase conjugate reproduction mirror has one mirror surface, a plurality of page data is imaged by controlling the rotation of the phase conjugate reproduction mirror during information reproduction. The difference is that a polygon mirror is used as the phase conjugate reproducing mirror.
An example using a polygon mirror will be described with reference to FIG.
As shown in FIG. 5, a polygon mirror 501 that is a polyhedron and has a plurality of mirror surfaces is used as a phase conjugate reproducing mirror. The angular velocity between the optical information recording medium 150 and the polygon mirror 501 is made constant by optimizing the multiple recording angle step when recording information on the optical information recording medium 150 in a multiplexed manner and the number of faces of the polygon mirror 501. can do. For example, the angular velocity may be set to the same angular velocity as that of the optical information recording medium 150 or may be set to a constant angular velocity that is half the angular velocity of the optical information recording medium 150. By doing so, the incident angle of the reflected reference light to the optical information recording medium 150 is kept constant for a certain period without controlling the stop or reverse rotation of the optical information recording medium 150 and the phase conjugate reproducing mirror. It is possible to perform a series of operations for keeping and acquiring page data and performing page jump to the next page.
According to the modification of the first embodiment shown above, by optimizing the multiple recording angle step in the case of recording information on the optical information recording medium and the number of faces of the polygon mirror polyhedron, Each page data can be taken one after another by automatically performing page jump while rotating at a constant angular velocity, and control during information reproduction can be further facilitated.

(Second Embodiment)
In the first embodiment, the relative angle between the information light and the reference light and the optical information recording medium 111 is changed by rotating the optical information recording medium 150. However, in the second embodiment, the relative angle is changed. The difference is that the direction of the reference light is controlled in order to change.
An example of controlling the direction of the reference light is shown in FIG.
In this case, a galvanometer mirror 601 is installed instead of the fixed reflection mirror 113. The relay lens 114 is disposed so that the reflection surface of the galvano mirror 601 and the page data recording position of the information recording layer of the optical information recording medium 150 are conjugated. Then, by rotating the phase conjugate reproducing mirror 202 and the galvanometer mirror 601, the relative angle can be changed while the optical information recording medium 150 is fixed.

According to the second embodiment described above, the same effect as that of the first embodiment can be obtained while the optical information recording medium is fixed by controlling the direction of the reference light by a galvanometer mirror or the like.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 100,200 ... Optical information recording / reproducing apparatus, 101 ... Laser light source, 102, 104 ... Shutter, 103, 106 ... Polarizing beam splitter (PBS), 105, 108, 114 ... Relay lens , 107 ... Spatial light modulator, 109 ... Aperture, 110 ... Objective lens, 111, 116 ... Half-wave plate, 112, 113 ... Reflection mirror, 150 ... Optical information recording medium 115 ...

System controller

116, 204 ... Actuator 201 ... Quarter wave plate 202 ... Phase conjugate reproduction mirror 203 ... Phase conjugate reproduction mirror controller 205 ... imaging unit, 401, 402, 403 ... angle, 404, 405 ... period, 501 ... polygon mirror, 601 ... galvanometer mirror.

Claims

A recording medium on which the information is recorded as a hologram is interfered by information light including information to be recorded emitted from a coherent light source and reference light having the same wavelength as the information light. A first control unit that controls to rotate in a certain direction;
A reflective element that reflects the reference light transmitted through the recording medium;
A second control unit that rotates and controls the reflection element so that an incident angle of the reflected reference light reflected by the reflection element to the recording medium is constant for a second period;
An optical information recording / reproducing apparatus comprising: an imaging unit that captures an image of reproduction light transmitted through the recording medium by the reflected reference light in a third period of the second period.
The optical information recording / reproducing apparatus according to claim 1, wherein the third period is a period in which the total luminance of the reproduction light is equal to or greater than a first threshold.
2. The third period is a period in which a difference between an incident angle of the reference light to the recording medium and an incident angle of the reflected reference light to the recording medium is within a second threshold. 2. An optical information recording / reproducing apparatus according to 1.
2. The optical information recording / reproducing apparatus according to claim 1, wherein the second control unit reversely rotates or stops the reflecting element when performing a page jump when reading recorded information. 3.
The optical information recording / reproducing apparatus according to claim 1, wherein the reflective element is a galvanometer mirror.
The optical information recording / reproducing apparatus according to claim 1, wherein the reflective element is a polygon mirror.
The first control unit does not change the angle between the information light and the reference light, and changes the angle of the recording medium at a constant interval, thereby making the relative relation between the information light and the reference light and the recording medium. The optical information recording / reproducing apparatus according to claim 1, wherein the angle is changed.
A recording medium on which information is recorded as a hologram is fixed for a first period by interference of information light including recorded information emitted from a coherent light source and reference light having the same wavelength as the information light. A first control unit that controls to
A first reflecting element that reflects the reference light and changes an incident angle on the recording medium;
A second reflective element that reflects the reference light transmitted through the recording medium;
A second control unit that rotates and controls the second reflective element so that an incident angle of the reflected reference light reflected by the second reflective element to the recording medium is constant for a second period;
An optical information recording / reproducing apparatus comprising: an imaging unit that captures an image of reproduction light transmitted through the recording medium by the reflected reference light in a third period of the second period.
A recording medium on which the information is recorded as a hologram is interfered by information light including information to be recorded emitted from a coherent light source and reference light having the same wavelength as the information light. Control to rotate in a certain direction,
Providing a reflective element for reflecting the reference light transmitted through the recording medium;
Rotating and controlling the reflective element so that the incident angle of the reflected reference light reflected by the reflective element to the recording medium is constant for a second period;
An optical information recording / reproducing method comprising: imaging the reproduction light transmitted through the recording medium by the reflected reference light in a third period of the second period.