JP2008299992A - Holographic memory recording device, holographic reproducing device, or holographic recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that tilt of a recording medium is changed and the incident angle of information light or reference light with respect to a recording medium is changed, so that an interference pattern on the recording medium changes, and a light receiving position in the light receiving sensor of obtained signal light may be changed. <P>SOLUTION: In the holographic memory recording and reproducing device, the device has a means for adjusting the incident angle of reference light to the recording medium, and adjusting the incident angle of the information light to the recording medium in accordance with the tilt of the recording medium, during recording. Also, the device has an adjusting means for adjusting the incident angle of the reference light to the recording medium is adjusted in accordance with the tilt of the recording medium, and receiving the signal light by the light receiving sensor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical information recording, reproducing, or recording / reproducing apparatus. In particular, information is recorded on a recording medium on which information is recorded using holography, and information is reproduced from the recording medium on which the information is recorded.

  In recent years, holographic memory has attracted attention in the field of practical use as next-generation ultra-high-density data storage. In particular, a digital hologram memory that develops image information or the like into two-dimensional digital pattern information, records the information on a recording medium using holography, and reproduces the information from the recording medium has attracted attention.

  As such a memory, there is a system in which two beams of information light and reference light are interfered to record holography on a recording medium, and reproduction is performed by irradiating only the reference light to the recording medium.

  In this case, the incident angle of the reference light for reproduction and the incident angle of the reference light for recording generated from the holographic interference pattern needs to be the same or shifted by 180 °. In particular, since the holographic storage medium has angle selectivity, the incident angle of the reproducing beam with respect to the holographic storage medium must be maintained very precisely.

  For this reason, Japanese Patent Laid-Open No. 2005-182975 discloses a tilt servo device that knows the tilt of a recording medium and corrects the incident angle of the reference light upon reproduction on the medium. This will be described with reference to FIG.

The tilt servo apparatus shown in FIG. 11 includes a light source 1, first and second detectors 2 and 3, a mirror 4, a tilt error signal generator 5, a recording medium 6, and a holographic plate 7. The reference light for reproduction is reflected by the storage medium 6 and received by the first and second detectors 2 and 3 via the holographic plate 7. Based on this, a tilt error signal is generated by the tilt error signal generator 5 and the mirror 12 is adjusted to adjust the incident angle of the reproduction beam. As described above, the influence caused by the inclination of the recording medium 6 can be reduced.
JP 2005-182975 A

  However, the conventional example has the following problems.

  For the sake of simplicity, a case is considered where the inclination of the recording medium at the time of recording is in the reference state and there is an inclination at the time of reproduction, and the recording medium at the time of recording is inclined and the inclination of the recording medium at the time of reproduction is in the reference state.

  FIG. 12 is a schematic diagram in the case where the inclination of the recording medium during recording is the reference state and there is an inclination φ2 during reproduction.

Here, the objective lens 9, the spatial light modulator (SLM 8) for generating information light, the reference light 100, the information light 200, the CMOS sensor 11 that receives the reproduced signal light 300, and the signal light for guiding the signal light to the CMOS sensor 11. The detection objective lens 10 of FIG. The same applies to FIG.
(A) shows the time of recording, and (b) shows the time of reproduction.

  It is assumed that the reference beam 100 is set so as to form an angle of φ1 with the recording medium 6 and recording is performed. Then, at the time of reproduction, it is assumed that the angle φ2 of the recording medium is corrected and the angle between the reference light 100 and the recording medium 6 is set to be φ1. Then, the obtained diffracted light has an angle of φ2 with respect to the recording time.

  In other words, the angle of the optical axis of the diffracted light during reproduction corresponding to the optical axis during recording (one-dot chain line) is φ2 in accordance with the inclination of the recording medium 6 and the optical axis (dotted line) of the tilt reproducing optical system. The optical axis of the diffracted light during reproduction and the optical axis of the reproduction optical system are separated by δ1 (= f1 · TANφ2). Here, f1 is a focal length from the objective lens 9 to the recording medium 6.

  FIG. 13 shows a schematic diagram in the case where the recording medium at the time of recording has an inclination of φ3 and the inclination of the recording medium at the time of reproduction is in a reference state.

  In this case, the optical axis of the information light 200 generated by the spatial light modulator (SLM 8) during recording has an inclination of φ3 with respect to the recording medium 6. As a result, during reproduction, the optical axis of the diffracted light and the reproduction optical system The angle formed by the optical axis is φ3, and the optical axis of the diffracted light during reproduction and the optical axis of the reproduction optical system are separated by δ2 (= f1 · TANφ3).

  As described above, in the above-described conventional example, a reproduction image shift occurs corresponding to the inclination of the recording medium, the correspondence between the SLM pixels and the CMOS sensor pixels is lost, and before and after the recording medium is attached or removed. It becomes difficult to ensure compatibility in recording and reproduction with the device.

  That is, with the conventional configuration, the tilt of the recording medium varies depending on the environment in which the drive is placed, and the incident angle of the information light or the reference light to the recording medium varies. Then, the light receiving position of the signal light obtained from the recording medium in the light receiving sensor may also fluctuate. Therefore, there has been a problem that good recording and reproduction cannot be performed due to the change in the inclination of the recording medium.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus that performs good recording and reproduction even when the tilt of the recording medium varies.

  In order to solve the above problems, the following is provided.

In a holographic memory recording apparatus for recording information by forming an interference pattern by information light and reference light on a recording medium,
Means for detecting the tilt of the recording medium;
Branching means for branching the light beam from the light source into two light beams;
A spatial light modulator for generating information light from the branched one light beam;
A mirror for adjusting an incident angle when the other branched light beam is incident on the recording medium as a reference light according to the inclination;
A holographic memory recording apparatus comprising adjusting means for adjusting an angle at which the information light is incident on the recording medium according to the inclination.

  Further, the following is provided.

In a holographic memory reproducing apparatus that reproduces the information by irradiating the reference light to a recording medium on which information is recorded by forming an interference pattern by the information light and the reference light.
Means for detecting the tilt of the recording medium;
A mirror for adjusting an incident angle when the reference light is incident on the recording medium according to the inclination;
A light receiving sensor for receiving the signal light having the information obtained by irradiating the interference pattern with the reference light;
A holographic memory reproducing apparatus, comprising: adjusting means for receiving the signal light, which fluctuates according to the inclination, by a light receiving sensor.

  Further, the following is provided.

Recording information by forming an interference pattern with information light and reference light on the recording medium,
In a holographic memory recording / reproducing apparatus for reproducing the information by irradiating the reference light to the interference pattern,
Means for detecting the tilt of the recording medium;
Branching means for branching the light beam from the light source into two light beams;
A spatial light modulator for generating information light from the branched one light beam;
A mirror for adjusting an incident angle when the other branched light beam is incident on the recording medium as a reference light according to the inclination;
A light receiving sensor for receiving the signal light having the information obtained by irradiating the interference pattern with the reference light;
First adjusting means for adjusting an angle of incidence of the information light on the recording medium according to the inclination;
A holographic memory recording / reproducing apparatus comprising: a second adjustment unit configured to receive the signal light with a light receiving sensor according to the inclination.

  Even if the recording medium is inclined due to the environment in which the drive is placed or the like, good recording and / or reproduction can be performed by the present invention.

  The present invention has the following configuration. This will be described in detail.

  When the spatial light modulator carries information according to the tilt of the recording medium, information light is generated by shifting the active area of the spatial light modulator and maintaining the desired incident angle on the recording medium. I do.

  Further, a means for shifting the optical axis is provided in the optical path from the spatial modulator to the recording medium, and the information light is guided to the objective lens by adjusting the shift amount according to the tilt amount, and the desired incident angle. Record information while maintaining Here, the means for shifting the optical axis is a parallel plate or a lens constituting a relay lens.

  At the time of reproduction, diffracted light from the recording medium obtained by irradiation of reference light is received as signal light by a CMOS sensor. Then, the diffracted light is received at a position where the active area of the CMOS sensor is shifted from the reference position in accordance with the tilt amount of the recording medium.

  Alternatively, it has means for shifting the optical axis by shifting the lens constituting the relay lens arranged in the optical path from the recording medium 6 to the CMOS sensor in a direction perpendicular to the optical axis. That is, by adjusting the means for shifting the optical axis according to the tilt amount of the recording medium 6, the signal light is shifted and made incident on the CMOS sensor. Thereby, it is possible to reduce the deviation of the signal light from the CMOS sensor.

  Here, the means for shifting the optical axis is a parallel plate or a lens constituting a relay lens.

  Accordingly, the information light, the reference light, and the angle of the recording medium are recorded in a substantially standard state regardless of the inclination of the recording medium. Further, it is possible to perform information reproduction without shifting the reproduction image on the CMOS sensor, and it becomes easy to ensure compatibility in recording and reproduction before and after the recording medium is attached / detached and in different apparatuses.

FIG. 1 is a block diagram showing a holographic memory device according to a first embodiment of the present invention.
(A) shows the time of recording, and (b) shows the time of reproduction.

  First, recording will be described.

  A light beam from the light source unit 21 is branched by a polarization beam splitter (PBS23). As a result, one light beam that passes through the polarization beam splitter (PBS 23) becomes reference light, is reflected by the galvano mirror 24 disposed between the recording medium 26 and the polarization beam splitter (PBS 23), and is guided to the scanning lens 25. It is burned. The scanning lens 25 irradiates the recording medium 26 with the reference light as recording reference light.

  Here, the half-wave plate 22 is variable in rotation, and at the time of reproduction to be described later, it is possible to change the polarization direction of the light beam incident on the PBS 23 so that light passing through the PBS 23 is not generated. .

  The other light beam reflected by the PBS 23 is reflected by the PBS 28 and enters the SLM 29. The incident light beam is reflected by being subjected to two-dimensional modulation corresponding to predetermined information by the spatial modulation function of the SLM 29, changes its polarization direction, and becomes information light. The light beam reflected by the SLM 29 passes through the PBS 28, and this information light is irradiated onto the recording medium 26 by the objective lens 32.

  Thus, an interference pattern between the recording reference light and the information light is generated, and information is recorded on the recording medium 26.

  Here, the expander 27 has a function of adjusting the diameter of a light beam that becomes information light. The relay lens 30 forms an image of a two-dimensional pattern by the spatial modulation function unit of the SLM 29 on the incident side focal plane of the objective lens 30. The half-wave plate 31 is switchable and is provided to change the polarization direction of the light beam from the recording medium 26 during reproduction, which will be described later.

  In the present embodiment, at the time of recording, the tilt of the recording medium 26 is detected by the tilt sensor 35, and the active region of the SLM 29 is shifted from the reference position by the controller 36 according to the tilt amount. Is generated.

  Next, playback will be described.

  During reproduction, the polarization direction of the light beam from the light source unit 21 is changed by the half-wave plate 22 so that the reflection by the PBS 23 does not occur. The light beam passing through the PBS 23 is reflected by the galvanometer mirror 24 and guided to the scanning lens 25. The scanning lens 25 irradiates the recording medium 26 with the reproduction reference light. At this time, diffracted light is generated by the interference pattern recorded on the recording medium 26, but this is not used as signal light.

  The light beam that has passed through the recording medium 26 is folded back by the galvanometer mirror 33 and enters the recording medium 26 as reference light for reproduction. The incident angle and re-incidence angle of the reproduction reference light to the recording medium 26 are controlled by the galvanometer mirror 24 and the galvanometer mirror 33. Here, it is not always necessary to adjust the angles of both the galvanometer mirror 24 and the galvanometer mirror 33. If the reference light 600 can re-enter the desired position at the desired incident angle with respect to the interference pattern of the recording medium 26, only the galvanometer mirror 33 may be angle-adjusted.

  The reproduction reference light that is irradiated back to the recording medium 26 generates diffracted light by the interference pattern recorded on the recording medium 26 and becomes signal light. This signal light is collected by the objective lens 32, the polarization direction is changed by the half-wave plate 31, and enters the PBS 28. The light beam incident on the PBS 28 is reflected by the PBS 28 and enters the CMOS sensor 34.

At the time of this reproduction, the tilt sensor 35 detects the tilt of the recording medium 26,
Depending on the amount of inclination, the CMOS sensor 34 becomes active at a position shifted from the reference position, and receives signal light.

  In this way, the light beam incident on the CMOS sensor 34 is converted into an electric signal by the image light receiving function unit of the CMOS sensor 34, and the two-dimensional pattern information corresponding to the desired interference pattern recorded on the recording medium 26 is reproduced.

  Here, the inclination detection of the recording medium 26 performed during recording and reproduction will be described. As shown in FIG. 2, the tilt detection is performed by receiving the reflected light from the recording medium 26 of the reference light 300 for recording or reproduction by the tilt sensor 35 divided into four.

The angle direction formed by the reference light 300 and the recording medium 26 is T, and the perpendicular direction is R, and the tilt in the R direction and the T direction from the amount of light received in each of the four areas A to D is expressed by the following equation. .
T direction Tilt = {(A + D)-(B + C)} / (A + B + C + D) (1)
R direction Tilt = {(A + B)-(C + D)} / (A + B + C + D) (2)
The tilt signal is detected as in (1) and (2).

Next, FIG. 3 is a conceptual diagram for explaining a situation where the active area of the SLM 29 during recording is shifted from the reference position.
(A) shows the reference state when the recording medium 26 is not inclined, and (b) shows the state when the recording medium is inclined from the reference state.
(C) shows the movement of the active area of the SLM 29 when the recording medium 26 is tilted from the reference state.

  First, in the reference state (a), the active region of the SLM 29 spreads around the optical axis (one-dot chain line) of the objective lens 32 to generate the information light 500. Then, the information light 500 and the recording reference light 400 set to θ1 with respect to the recording medium 26 interfere with each other in the recording medium 26 to form an interference pattern.

  Next, in the case where the recording medium 26 of (b) is tilted by θ2, the tilt of the recording medium 26 is detected, and the galvanometer mirror 24 so that the angle of the reference light 400 becomes θ1 with respect to the recording medium 26. Control with. At the same time, the active light 51 of the SLM 29 is moved from the reference position indicated by the dotted line area to the solid line area by d1 as shown in FIG.

  Here, when the magnification of the relay lens 30 is 1 and the focal length (f2) of the objective lens 32 is 3 mm and θ2 = 0.6 °, d1 = f2 · TANθ2≈31 μm.

  When the pixel pitch of the SLM 29 is 15 μm, it is about 2 pixels.

  Therefore, the controller 36 moves the active area 51 of the SLM 29 by two pixels. For example, when the pixel pitch of the SLM is 7 μm, the pixel moves by 4 pixels.

  Here, the number of moving pixels is set so that the error is ½ or less of the pixel pitch.

  Therefore, for example, when the pixel pitch is 15 μm, the pixel movement is not performed when the tilt amount is ± 0.14 ° or less.

  Thus, when the recording medium 26 is tilted, the active region of the SLM 29 is moved to generate the information light 500 so that the angle relationship between the recording reference light 400 and the information light 500 is the same as in the standard state. Thus, the same recording as in the reference state of (a) was made.

  That is, regardless of the inclination of the recording medium 6, the angle formed by the reference light 400, the information light 500, and the recording medium 6 is always kept constant.

Next, FIG. 4 is a conceptual diagram for explaining a situation where the active area of the CMOS sensor 34 during reproduction is shifted from the reference position.
(A) shows a reference state when the recording medium 26 is not inclined, and (b) shows a state when the recording medium 26 is inclined from the reference state. (C) shows an active region of the CMOS sensor 34 when the recording medium 26 is tilted from the reference state.

  First, in the standard state of (a), the signal light 700 by the reproduction reference light 600 set to the same θ1 as at the time of recording spreads around the optical axis of the objective lens 32. Correspondingly, an active area 52 of the CMOS sensor 34 is set, and information recorded on the recording medium 26 is reproduced.

  On the other hand, when the recording medium 26 of (b) is inclined by θ2, the galvanometer mirror 24 and the galvanometer mirror 33 are detected so that the tilt of the recording medium 26 is detected and the angle of the reference light 600 becomes θ1 with respect to the recording medium 26. To control. Here, it is not always necessary to adjust the angles of both the galvanometer mirror 24 and the galvanometer mirror 33. If the reproduction reference beam 600 can re-enter the desired position at a desired angle with respect to the interference pattern of the recording medium 26, only the galvanometer mirror 33 may be adjusted in angle.

  The reproduced signal light 700 is shifted by d2 from the reference state according to the inclination of the recording medium 26 and enters the CMOS sensor 34. Here, according to the tilt amount of the recording medium 26, the active area 52 of the CMOS sensor 34 is shifted by d2 from the reference position indicated by the dotted line area to the solid line area as shown in FIG.

  Here, when θ3 = 0.6 °, d1 = f2 · TANθ3≈31 μm.

  If the pixel pitch of the CMOS sensor 34 is 5 μm, it is about 6 pixels.

  Therefore, in this case, the active area 52 of the CMOS sensor 34 is moved by 6 pixels according to the inclination of the recording medium 26.

  For example, when the pixel pitch of the CMOS sensor 34 is 4 μm, it is shifted by 8 pixels.

  Then, the number of pixels moved in accordance with the inclination is set so that the error amount becomes 1/2 or less of the pixel pitch.

  Therefore, for example, when the pixel pitch is 5 μm, the pixel movement is not performed when the tilt amount is ± 0.04 ° or less.

  As described above, in this embodiment, it is necessary to use the CMOS sensor 34 having a light receiving region that can allow the fluctuation amount with respect to the light flux that fluctuates by the tilt amount.

  Thus, when the recording medium 26 is tilted, the active area of the CMOS sensor 34 is shifted, so that the relationship between the reference light 600 and the information light 700 is the same as that in the standard state, and the standard of (a). The same playback as the state was made.

  In this embodiment, the light beam is separated using the PBS 23 and transmission / non-transmission is determined by the wavelength selection plate. However, the present invention is not limited to this. That is, a beam splitter (BS) may be used. In this case, a shutter for shielding light or a parallel plate for shielding light may be inserted into the optical axis. The same applies to the following embodiments.

  Next, a second embodiment of the present invention will be described.

FIG. 5 is a block diagram showing a holographic memory device according to a second embodiment of the present invention.
(A) shows the time of recording, and (b) shows the time of reproduction. The description of the same configuration as that of the first embodiment is omitted.

  In this embodiment, in addition to the configuration of the first embodiment, a parallel plate 37, a parallel plate 38, a parallel plate driving means 39, and a parallel plate driving means 40 are newly added. Each function will be described later.

  First, recording will be described.

  In this embodiment, during recording, the tilt of the recording medium 26 is detected by the tilt sensor 35, and the parallel plate 37 is tilted with respect to the optical axis by the parallel plate driving means 39 based on the tilt amount. Thereby, the position at which the reflected light from the SLM 29 enters the objective lens 32 is shifted.

  Here, the tilt of the parallel plate 37 may be detected by a tilt sensor (not shown).

  Next, playback will be described.

  At the time of reproduction, the tilt of the recording medium 26 is detected by the tilt sensor 35, and information on the amount of tilt is acquired by the parallel plate driving means 40. Then, the parallel plate 38 is controlled to be inclined with respect to the optical axis according to the amount of inclination. Thereby, the signal light from the recording medium 26 is shifted, and the incident position on the CMOS sensor 34 is shifted.

  At this time, the tilt of the parallel plate 38 may be detected by a tilt sensor (not shown).

  In this way, the light beam incident on the CMOS sensor 34 is converted into an electric signal by the image light receiving function unit of the CMOS sensor 34, and the two-dimensional pattern information corresponding to the desired interference pattern recorded on the recording medium 26 is reproduced.

FIG. 6 is a conceptual diagram for explaining a situation where the parallel plate 37 is tilted with respect to the optical axis and the position where the reflected light from the SLM 29 is incident on the objective lens 32 during recording.
(A) shows a reference state when the recording medium 26 is not inclined, and (b) shows a state when the recording medium 26 is inclined from the reference state.

  First, in the reference state (a), the information light 500 generated by the SLM 29 is incident on the objective lens 32 around the optical axis of the objective lens 32 and is set to θ1 with respect to the recording medium 26. And the recording medium 26 interfere with each other to form the pattern.

  Next, when the recording medium 26 in (b) is tilted by θ4, the tilt of the recording medium 26 is detected and the incident angle of the recording reference light 400 with respect to the recording medium 26 is controlled to be θ1. . At the same time, the parallel plate 37 is tilted with respect to the optical axis by θ5 in accordance with the tilt amount of the recording medium 26, whereby the position incident on the objective lens 32 is shifted from the reference position indicated by the dotted line center to the one-dot chain line center. Move by d3.

  Here, when the magnification of the relay lens 30 is 1, the focal length (f2) of the objective lens 32 is 3 mm, and θ4 = 0.6 °, d3 = f2 · TANθ4≈31 μm.

  That is, the parallel plate 37 is tilted by θ5≈2.7 °, with the parallel plate 37 having a thickness of 1 mm and a refractive index of 1.52.

  Thus, when the recording medium 26 is tilted, the parallel flat plate 37 is tilted so that the relationship between the recording reference light 400 and the information light 500 is the same as that in the standard state. The same record was made.

Next, FIG. 7 shows a conceptual diagram for explaining a situation in which the signal light 700 from the recording medium 26 during reproduction is shifted to shift the incident position on the CMOS sensor 34.
(A) shows the reference state when the recording medium 26 is not inclined, and (b) shows the state when the recording medium 26 is inclined from the reference state.

  First, in the standard state (a), the signal light 700 generated by the reference light 600 set to the same θ1 as in recording is incident on the CMOS sensor 34 around the extension of the optical axis of the objective lens 32 and recorded. Information recorded on the medium 26 is reproduced.

  Next, when the recording medium 26 in (b) is tilted by θ6, the tilt amount of the recording medium 26 is detected so that the angle of the reference light 600 for reproduction becomes θ1 with respect to the recording medium 26. To control. Then, the signal light 700 to be reproduced shifts by d4 from the reference state and enters the CMOS sensor 34 according to the inclination of the recording medium 26. Accordingly, the parallel plate 38 is inclined with respect to the optical axis by θ7, and the position incident on the objective lens 32 is moved d4 from the reference position indicated by the dotted line center to the one-dot chain line center, and is incident on the same position as the reference state. To return.

  If θ6 = 0.6 °, d4 = f2 · TANθ6≈31 μm.

  Accordingly, the thickness of the parallel plate 38 is 1 mm, the refractive index is 1.52, and the parallel plate 38 is tilted by θ7≈2.7 ° so that the incident position on the CMOS sensor 34 is the same as the reference state.

  Thus, when the recording medium 26 is tilted, the parallel plate 38 is tilted so that the incident position of the information light 700 on the CMOS sensor 34 is the same as that in the reference state. It was made to play.

  A third embodiment will be described.

FIG. 8 is a block diagram showing a holographic memory device according to a third embodiment of the present invention.
(A) shows the time of recording, and (b) shows the time of reproduction. The description of the same configuration as that of the first embodiment is omitted.

  In the present embodiment, in addition to the configuration of the first embodiment, a driving unit 43 is newly added. The driving means 43 is for moving the lens 41 constituting the relay lens 30 described in the first embodiment in a direction perpendicular to the optical axis. The function is described in detail below.

  First, recording will be described.

  At the time of recording, the tilt of the recording medium 26 is detected by the tilt sensor 35, and the lens 36 constituting the relay lens 30 is driven by the controller 36 in the direction perpendicular to the optical axis by the controller 36 according to the tilt amount. The position where the reflected light from the SLM 29 enters the objective lens 32 is shifted.

  The amount of movement of the lens 41 is detected by a lens position sensor (not shown).

  Next, playback will be described.

  At the time of reproduction, the tilt of the recording medium 26 is detected by the tilt sensor 35, and the lens 41 constituting the relay lens 30 is driven by the controller 36 in the direction perpendicular to the optical axis by the controller 36 according to the tilt amount. To shift the signal light from the recording medium 26 to shift the incident position on the CMOS sensor 34.

  In this way, the light beam incident on the CMOS sensor 34 is converted into an electric signal by the image light receiving function unit of the CMOS sensor 34, and the two-dimensional pattern information corresponding to the desired interference pattern recorded on the recording medium 26 is reproduced.

FIG. 9 is a conceptual diagram for explaining a situation in which, during recording, the lens constituting the relay lens 30 is moved in the direction perpendicular to the optical axis and the position where the reflected light from the SLM 29 enters the objective lens 32 is shifted.
(A) shows a reference state when the recording medium 26 is not inclined, and (b) shows a state when the recording medium 26 is inclined from the reference state.

  In the standard state (a), the information light 500 generated by the SLM 29 is incident on the objective lens 32 around the optical axis of the objective lens 32, and is recorded with the reference light 400 set to θ1 with respect to the recording medium 26. Interference occurs in the medium 26 to form an interference pattern.

  Next, when the recording medium 26 in (b) is tilted by θ8, the tilt of the recording medium 26 is detected, and the angle of the reference light 400 is controlled by the galvano mirror 24 so as to be θ1 with respect to the recording medium 26. To do. At the same time, the lens 41 constituting the relay lens 30 is moved by d5 in the direction perpendicular to the optical axis in accordance with the tilt amount of the recording medium 26, and the position incident on the objective lens 32 is indicated by the dotted line center. Move from the position to the center of the one-dot chain line.

  When the focal length (f2) of the objective lens 32 is 3 mm and θ8 = 0.6 °, d5 = f2 · TANθ4≈31 μm is obtained, and when the magnification of the relay lens 30 is 1, d6 = d5.

  That is, the lens 41 is moved by 31 μm by the lens driving means 43.

  Thus, when the recording medium 26 is tilted, the lens 41 constituting the relay lens 30 is moved in the direction perpendicular to the optical axis so that the relationship between the reference light 400 and the information light 500 becomes the same as in the standard state. Thus, the same recording as in the reference state of (a) was made.

FIG. 10 is a conceptual diagram for explaining a situation where the lens 41 constituting the relay lens 30 is moved in the direction perpendicular to the optical axis to shift the incident position on the CMOS sensor 34 during reproduction.
(A) shows a reference state when the recording medium 26 is not inclined, and (b) shows a state when the recording medium 26 is inclined from the reference state.

  In the standard state of (a), the signal light 700 by the reference light 600 set to the same θ1 as at the time of recording enters the CMOS sensor 34 around the extension of the optical axis of the objective lens 32 and is recorded on the recording medium 26. The information being played is played back.

  Next, when the recording medium 26 in (b) is tilted by θ9, the tilt of the recording medium 26 is detected and the angle of the reference light 600 is controlled to be θ1 with respect to the recording medium 26. Then, the signal light 700 to be reproduced enters the CMOS sensor 34 with a d7 shift from the reference state in accordance with the inclination of the recording medium 26. Therefore, the lens 41 constituting the relay lens 30 is moved by d8 in a direction perpendicular to the optical axis, and the position incident on the CMOS sensor 34 is moved by d7 from the reference position indicated by the dotted line center to the one-dot chain line center. Return to the same position as in the reference state.

  Here, when θ9 = 0.6 °, d4 = f2 · TANθ6≈31 μm.

  Therefore, the lens 41 is moved by 31 μm.

  Thus, when the recording medium 26 is tilted, the lens 41 constituting the relay lens 30 is moved in the direction perpendicular to the optical axis so that the incident position of the signal light 700 on the CMOS sensor 34 is the same as in the reference state. Thus, reproduction similar to the reference state of (a) is performed.

  As described above, the relationship between the information light and the medium is recorded in a substantially reference state, and information reproduction without a shift of the reproduced image on the CMOS sensor can be performed. It becomes easy to ensure compatibility in recording and reproduction.

  As described above, in the present invention, a holographic memory recording device, a holographic memory reproducing device, and a holographic recording / reproducing that can perform good recording and / or reproduction even when the recording medium is inclined due to an environment in which the drive is placed or the like. Equipment was provided.

1 is a block diagram illustrating a holographic memory device according to Embodiment 1. FIG. It is a figure explaining the inclination detection of a recording medium. It is a conceptual diagram explaining the situation which shifts the active area | region of SLM at the time of recording which concerns on Example 1 from a reference position. It is a conceptual diagram explaining the condition which shifts the active area | region of the CMOS sensor at the time of the recording which concerns on Example 1 from a reference position. 6 is a block diagram showing a holographic memory device according to Embodiment 2. FIG. It is a conceptual diagram explaining the situation which inclines the parallel plate at the time of recording which concerns on Example 2 with respect to an optical axis, and shifts the position where the reflected light from SLM injects into an objective lens. It is a conceptual diagram explaining the situation which inclines the parallel plate at the time of reproduction | regeneration which concerns on Example 2 with respect to an optical axis, and shifts the position where the reflected light from SLM enters an objective lens. FIG. 6 is a block diagram illustrating a holographic memory device according to a third embodiment. FIG. 10 is a conceptual diagram illustrating a situation in which a lens constituting a relay lens at the time of recording according to Example 3 is moved in a direction perpendicular to an optical axis to shift a position where reflected light from an SLM enters an objective lens. FIG. 10 is a conceptual diagram illustrating a situation in which a lens constituting a relay lens at the time of reproduction according to Example 3 is moved in a direction perpendicular to the optical axis to shift a position where reflected light from an SLM is incident on an objective lens. It is a block diagram showing a conventional holographic memory device capable of detecting a tilt of a recording medium. It is a figure explaining the problem at the time of recording of the holographic memory device in which the tilt detection of the conventional recording medium is possible. It is a figure explaining the problem at the time of reproduction | regeneration of the conventional holographic memory device in which the tilt detection of a recording medium is possible.

Explanation of symbols

21 Light source 23, 28 PBS
24, 33 Galvano mirror 25 Scan lens 26 Recording medium 29 SLM
Reference Signs List 30 relay lens 32 objective lens 34 CMOS sensor 35 tilt sensor 36 controller 37, 38 parallel plate 39, 40 parallel plate drive means 43 lens drive means

Claims (15)

In a holographic memory recording apparatus capable of recording information by forming an interference pattern on a recording medium by irradiating information light and reference light,
Means for detecting the tilt of the recording medium;
Branching means for branching the light beam from the light source into two light beams;
A spatial light modulator for generating information light from the branched one light beam;
A mirror for adjusting an incident angle when the other branched light beam is incident on the recording medium as a reference light according to the inclination;
A holographic memory recording apparatus comprising adjusting means for adjusting an angle at which the information light is incident on the recording medium according to the inclination.   2. The holographic memory recording apparatus according to claim 1, wherein the adjusting means is means for moving an active area of the spatial light modulator.   2. The holographic memory recording apparatus according to claim 1, wherein the adjusting means is means for inclining a parallel plate disposed in an optical path from the spatial light modulator to the recording medium.   The adjusting means is means for driving a lens constituting a relay lens disposed in an optical path from the spatial light modulator to the recording medium in a direction perpendicular to the optical axis of the information light. The holographic memory recording device according to claim 1. Holographic memory reproducing apparatus for reproducing information by irradiating the reference light onto a recording medium on which information is recorded by forming an interference pattern by irradiating the information light and the reference light In
Means for detecting the tilt of the recording medium;
A mirror for adjusting an incident angle when the reference light is incident on the recording medium according to the inclination;
A light receiving sensor for receiving the signal light having the information obtained by irradiating the interference pattern with the reference light;
A holographic memory reproducing apparatus, comprising: adjusting means for receiving the signal light, which fluctuates according to the inclination, by a light receiving sensor.   6. The holographic memory reproducing device according to claim 5, wherein the adjusting means is means for inclining a parallel plate provided in an optical path from the recording medium to the light receiving sensor.   The adjusting means is means for shifting a lens constituting a relay lens provided in an optical path from the recording medium to the light receiving sensor in a direction perpendicular to the optical axis of the signal light. The holographic memory reproducing device according to claim 5. Holographic memory reproducing apparatus for reproducing the information by irradiating the reference light onto a recording medium on which information is recorded by forming an interference pattern by irradiating the information light and the reference light In
Means for detecting the tilt of the recording medium;
A mirror for adjusting an incident angle when the reference light is incident on the recording medium according to the inclination;
In order to receive the signal light having the information obtained by irradiating the interference pattern with the reference light, the light receiving region for receiving the signal light that varies according to the inclination of the recording medium is provided. A light receiving sensor;
A holographic memory reproducing apparatus comprising: Recording information by forming an interference pattern by irradiating information light and reference light to the recording medium,
In a holographic memory recording / reproducing apparatus for reproducing the information by irradiating the reference light to the interference pattern,
Means for detecting the tilt of the recording medium;
Branching means for branching the light beam from the light source into two light beams;
A spatial light modulator for generating information light from the branched one light beam;
A mirror for adjusting an incident angle when the other branched light beam is incident on the recording medium as a reference light according to the inclination;
A light receiving sensor for receiving the signal light having the information obtained by irradiating the interference pattern with the reference light;
First adjusting means for adjusting an angle of incidence of the information light on the recording medium according to the inclination;
A holographic memory recording / reproducing apparatus comprising: a second adjustment unit configured to receive the signal light with a light receiving sensor according to the inclination. Recording information by forming an interference pattern by irradiating information light and reference light to the recording medium,
In a holographic memory recording / reproducing apparatus for reproducing the information by irradiating the reference light to the interference pattern,
Means for detecting the tilt of the recording medium;
Branching means for branching the light beam from the light source into two light beams;
A spatial light modulator for generating information light from the branched one light beam;
A mirror for adjusting an incident angle when the other branched light beam is incident on the recording medium as a reference light according to the inclination;
A light receiving region for receiving the signal light having the information obtained by irradiating the interference pattern with the reference light, the light receiving region receiving the signal light varying according to the inclination of the recording medium A light receiving sensor having
First adjusting means for adjusting an angle of incidence of the information light on the recording medium according to the inclination;
A holographic memory recording / reproducing apparatus comprising:   11. The holographic memory recording / reproducing apparatus according to claim 9, wherein the first adjusting means is means for moving an active area of the spatial light modulator.   11. The holographic memory according to claim 9, wherein the first adjusting means is means for inclining a parallel plate disposed in an optical path from the spatial light modulator to the recording medium. Recording / playback device.   The first adjusting means is means for driving a lens constituting a relay lens disposed in an optical path from the spatial light modulator to the recording medium in a direction perpendicular to the optical axis of the information light. 11. The holographic memory recording / reproducing apparatus according to claim 9 or 10, wherein:   The holographic memory recording / reproducing apparatus according to claim 9, wherein the second adjusting unit is a unit that tilts a parallel plate provided in an optical path from the recording medium to the light receiving sensor.   The second adjusting means is means for shifting a lens constituting a relay lens provided in an optical path from the recording medium to the light receiving sensor in a direction perpendicular to the optical axis of the signal light. The holographic memory recording / reproducing apparatus according to claim 9, wherein:

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