JP2009170086A - Holographic recording method and unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a data transfer rate by shortening time required for restoring an asking servo when performing recording on a holographic recording medium by means of a recording beam. <P>SOLUTION: In a hologram recording unit 50, while a hologram recording medium 12 is being driven, by use of an object light and a reference light as one pair to form an interference fringe on the holographic recording medium 12, a first recording beam out of two pairs of recording beams is radiated while shifting to an identical direction substantially in synchronization with the hologram recording medium 12 at the recording time, so as to be restored to an original position at the next restoration. At the above restoration time of the first recording beam, a second recording beam of the other pair is radiated while shifting to an identical direction substantially in synchronization with the hologram recording medium 12, so as to be restored to the original position during the restoration time of the above first recording beam. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a holographic recording method and apparatus for recording information on a holographic recording medium by interference fringes between object light and reference light.

  For example, in the holographic recording method described in Patent Document 1, recording and reproduction are performed by a recording beam in which object light and reference light are made into one set, and at this time, recording is performed by a tracking control mirror in synchronization with a rotating recording medium. The beam was moved in the same direction as the holographic recording medium, that is, asking servo was performed.

JP 2002-183975 A

  In the holographic recording method and apparatus described in Patent Document 1, the recording beam is moved in synchronization with the recording medium by the tracking control mirror, but recording or reproduction by the laser beam cannot be performed during the return time of the tracking control mirror. .

  Therefore, there is a problem in that the return time of the tracking control mirror, that is, the time required for returning the asking servo causes the data transfer rate to decrease.

  The present invention has been made in view of the above-described conventional problems, and provides a holographic recording method and apparatus capable of substantially increasing the data transfer rate by substantially reducing the return time of the asking servo. The purpose is to provide.

  This object is achieved by the present invention described below.

(1) While driving the holographic recording medium, one set of first recording beams among a plurality of recording beams including a set of object light and reference light for forming interference fringes on the holographic recording medium, During the recording time, irradiation is performed while moving in the same direction substantially in synchronism with the holographic recording medium, returning to the original position at the next return time, and at least one second recording beam of the plurality of sets remaining. Is irradiated while moving in the same direction substantially synchronously with the holographic recording medium during the return time of the first recording beam.

(2) The holographic recording medium is irradiated with the plurality of sets of recording beams sequentially shifted in at least one of a driving direction and a direction orthogonal to the driving direction. Graphic recording method.

(3) A recording medium driving device that drives a holographic recording medium capable of recording interference fringes between incident object light and reference light, a laser light source, and a laser beam emitted from the laser light source, Each of a plurality of sets of recording beams composed of object light and reference light is separately guided to the holographic recording medium, and the same number of recording beam optical systems as the number of recording beams, and object light in each recording beam optical system Are arranged in an object optical system that guides the reference light in each recording beam optical system, and a spatial light modulator that modulates the object light in accordance with information to be recorded. An optical shutter capable of blocking; a control device that controls the recording medium driving device, the optical shutters, and the spatial light modulators; and includes a plurality of recording beam optical systems. A tracking control mirror that reflects the recording beam of one recording beam optical system and advances and retreats the reflection point thereof; a next recording beam guided by the next recording beam optical system among the plurality of recording beam optical systems; and Next tracking control in which the one recording beam reflected from the tracking control mirror is reflected in the direction of the holographic recording medium, and the reflection point thereof advances and retreats in parallel with the advancing and retreating direction of the reflection point in the tracking control mirror. Each recording beam optical system is sequentially provided with a mirror, and each recording beam optical system sequentially shifts each recording beam in at least one of a driving direction in the holographic recording medium and a direction orthogonal thereto. It is set so as to be incident on a holographic recording medium, and the control device can control each tracking control mirror. Both of the recording beams are sequentially recorded on the holographic recording medium, and during recording, the recording beam is moved in synchronization with the driving direction of the holographic recording medium. The following control mirrors are controlled so that the recording beam is moved in the direction opposite to the driving direction, and the recording beam optical system is blocked by the optical shutter of the recording beam optical system of the recording beam that is not being recorded. A holographic recording apparatus characterized by being configured as described above.

  When recording on a holographic recording medium with a recording beam, it is possible to reduce the time required for returning the asking servo and increase the data transfer rate.

1 is an optical system diagram including a partial side view showing a holographic recording device according to an embodiment of the present invention. The top view which shows typically the recording state by the recording beam in the Example Schematic sectional view showing an enlarged main part of the same embodiment Schematic sectional view showing the main part in an enlarged manner Diagram showing the positional relationship between the recording positions of the first and second recording beams and the tracking control mirror in the same embodiment Timing chart showing the relationship between the recording time of each recording beam and the return state to the original position when there are three recording beams

  While driving the holographic recording medium, one set of first recording beams among a plurality of sets of recording beams, each of which includes object light and reference light for forming interference fringes on the holographic recording medium, is recorded in the recording time. Irradiating while moving in the same direction substantially synchronously with the holographic recording medium, returning to the original position at the next return time, and at least one set of the second recording beams among the remaining of the plurality of sets, During the return time of the first recording beam, the return time of the asking servo is made almost zero by irradiating it while moving in the same direction substantially in synchronization with the holographic recording medium. Achieve.

  Hereinafter, the holographic recording apparatus 50 according to the first embodiment of the present invention shown in FIG. 1 will be described in detail.

  The holographic recording apparatus 50 according to the first embodiment is configured to record two sets of object light and reference light that form interference fringes on the holographic recording medium 12 while driving the holographic recording medium 12. Among the beams, the first recording beam is irradiated while moving in the same direction substantially synchronously with the holographic recording medium 12 during the recording time, returned to the original position at the next return time, and another set of second recordings. The beam is irradiated while moving in the same direction substantially synchronously with the holographic recording medium 12 during the return time of the first recording beam, and returned to the original position during the recording time of the first recording beam. It is a thing.

  More specifically, the holographic recording device 50 includes a recording medium driving device 52 for driving the holographic recording medium 12 capable of forming interference fringes between incident object light and reference light, a laser light source 54, and the laser. First and second, which are branched from the laser beam emitted from the light source 54, each of two sets of recording beams, one set of object light and reference light, are separately guided to the holographic recording medium 12 as a recording beam. The first and second recording beam optical systems 56 and 58 and the first and second recording beam optical systems 56 and 58 are disposed in the object optical systems 56A and 58A, and modulate the object light according to the information of the recording apparatus. Arranged in the second spatial light modulators 60 and 62 and the reference optical systems 56B and 58B in the first and second recording beam optical systems 56 and 58, respectively. The first and second optical shutters 64 and 66 that can be blocked, the recording medium driving device 52, the first and second optical shutters 64 and 66, and the first and second spatial light modulators 60 and 62 are controlled. And a control device 68.

  The first recording beam optical system 56 is provided with a first follow-up control mirror 70 that reflects the recording beam and advances and retracts the reflection point.

  The second recording beam optical system 58 reflects the first recording beam reflected from the first tracking control mirror 70 in the direction of the holographic recording medium 12, and the reflection point of the first recording beam is reflected in the first tracking control optical system 58. A second follow-up control mirror 72 is provided for advancing and retreating in parallel with the advancing / retreating direction of the reflection point on the mirror 70.

  Further, the first and second recording beam optical systems 56 and 58 cause the respective recording beams 57 and 59 to be orthogonal to the driving direction in the holographic recording medium 12 as shown in FIG. Are alternately shifted (staggered) so as to be incident on the holographic recording medium 12.

  The control device 68 can control the advance and retreat of the first and second tracking control mirrors 70 and 72. More specifically, the control device 68 sequentially records the holographic recording medium 12 by the first and second recording beams, and during the recording, the first and second recording beams are holographically recorded. The first and second follow-up control mirrors 70 are moved in the movement direction of the recording medium 12 in synchronization therewith, and at the same time, other recording beams not being recorded are moved in the direction opposite to the driving direction. , 72 are controlled, and one of the first and second optical shutters 64 and 66 in the recording beam optical system for the recording beam not being recorded is blocked.

  Reference numerals 74, 76, and 78 in FIG. 1 denote beam splitters, respectively. The beam splitter 74 reflects part of the laser beam emitted from the laser light source 54 as object light in the first recording beam optical system 56.

  The beam splitter 76 reflects a part of the laser beam that has passed through the beam splitter 74 and serves as reference light in the first recording beam optical system 56.

  Further, the beam splitter 78 reflects a part of the laser beam that has passed through the beam splitter 76 and serves as reference light in the second recording beam optical system 58.

  The laser beam that has passed through the beam splitter 78 is used as object light in the second recording beam optical system 58.

  The first and second tracking control mirrors 70 and 72 have a reflection surface of 45 ° with respect to the bisector of the reference light and the object light in each of the first and second recording beams. Arranged at an angle.

  In the figure, reference numeral 80 denotes a mirror, and 82 denotes a Fourier lens provided in each of the object optical systems 56A and 58A and the reference optical systems 56B and 58B. Reference numerals 70A and 72A denote motors for driving the first follow-up control mirror 70 and the second follow-up control mirror 72, respectively, and 52A denotes a spindle motor that constitutes a part of the recording medium driving device 52.

  Next, with reference to FIGS. 3 and 4, the operation of the first and second tracking control mirrors 70 and 72 will be described in more detail.

First, if the first and second tracking control mirror 70, 72 from a state in which a solid line position in FIG. (A normal position), in which only the first following control mirror 70, moved by X ₁ in the right direction in FIG. 3 think of.

The reflection surfaces of the first and second tracking control mirrors 70 and 72 are at an angle of 45 ° with respect to the bisector of the reference light and the object light in the first and second recording beams, respectively. Since the first tracking control mirror 70 is disposed, the movement amount X ₁ in the right direction in FIG. 3, the reference light (referred to as reference light 1) of the first recording beam on the holographic recording medium 12, and the object A relational expression of Y ₁ = √2X ₁ is established between the movement amount Y _{1 of the} point where the light (shown as object light 1) intersects.

At the same time as the movement of X ₁ in the right direction in the drawing of the first tracking control mirror 70 shown in FIG. 3, the first sub control mirror 70 is moved in the direction of the drawing as shown in FIG. Consider the case where only X _{2 is} moved.

In this case, the movement amounts X ₁ and X ₂ , the object light 1, the reference light 1, and the reference light (referred to as reference light 2) of the second recording beam and the object light (referred to as object light 2) intersect each other. The relationship between the movement amounts Y ₁ and Y ₂ is Y ₁ = √2 (X ₂ −X ₁ ) and Y ₂ = √2X ₂ .

By simultaneously driving the first tracking control mirror 70 and the second tracking control mirror 72 in the right direction in the figure, the amount of movement of the first recording beam and the second recording beam at the point where the object beam and the reference beam intersect each other can be changed. In FIG. 4, the neutral points indicated by 0 are opposite to each other, and the amounts of movement of Y ₁ and Y ₂ are Y ₁ = √2 (X ₂ −X ₁ ), Y ₂ = √2X ₂ . Become.

That is, as shown by the solid line X ₁ and the alternate long and short dash line X ₂ in FIG. 5, when the follow-up control mirrors 70 and 72 are reciprocated in synchronization with each other, X ₁ and X ₂ at that time, The positions of the intersections of the reference beam and the object beam in the recording beam in the holographic recording medium 12 change in synchronization with each other in opposite directions as indicated by the two-dot chain line Y ₁ and the broken line Y _2. .

  Accordingly, during recording by the first recording beam, the second recording beam is in the process of returning to the original position, and conversely, during recording by the second recording beam, the first recording beam is in the process of returning to the original position, There is no blank time in the returning process of asking servo, and the data transfer rate can be increased to twice that in the case of recording / reproducing with one conventional spot.

  In the above embodiment, as shown in FIG. 2A, the first and second recording beams have the reference light and the object light at positions on the holographic recording medium 12 that are staggered with respect to the driving direction. However, the present invention is not limited to this, and as shown in FIG. 2 (B), the moving lines are separated in parallel by the first recording beam and the second recording beam. As shown in FIG. 2C, the first and second recording beams 57 and 59 may alternately enter the holographic recording medium 12 on the same movement line.

  In the above embodiment, the number of recording beams is two, and the first and second tracking control mirrors 70 and 72 are provided correspondingly. However, the present invention is not limited to this, Three or more recording beams may be used. For example, when there are three recording beams, the first tracking control mirror reflects only the first recording beam, the second tracking control mirror reflects the first recording beam reflected by the first tracking control mirror, and the second recording beam. The third tracking control mirror reflects the first recording beam reflected by the second tracking control mirror, the second recording beam reflected by the second tracking control mirror, and the third recording beam, respectively. Set to

  The relationship between the positions of the first to third recording beams on the holographic recording medium 12 and the time at that time is as shown in FIG. In FIG. 6, a straight line rising to the right indicates recording, and a straight line falling to the right indicates recovery.

DESCRIPTION OF SYMBOLS 12 ... Holographic recording medium 50 ... Holographic recording device 52 ... Recording medium drive device 54 ... Laser light source 56A, 58A ... Object optical system 56B, 58B ... Reference optical system 56 ... First recording beam optical system 57 ... First recording beam 58 ... second recording beam optical system 59 ... second recording beam 60 ... first spatial light modulator 62 ... second spatial light modulator 64 ... first optical shutter 66 ... second optical shutter 68 ... control device 70 ... first Tracking control mirror 72 ... Second tracking control mirror 82 ... Fourier lens

Claims (3)

  While driving the holographic recording medium, one set of first recording beams among a plurality of sets of recording beams, each of which includes object light and reference light for forming interference fringes on the holographic recording medium, is recorded in the recording time. Irradiating while moving in the same direction substantially synchronously with the holographic recording medium, returning to the original position at the next return time, and at least one set of the second recording beams among the remaining of the plurality of sets, A holographic recording method comprising irradiating the first recording beam while moving in the same direction substantially synchronously with the holographic recording medium during the return time of the first recording beam.   2. The holographic recording according to claim 1, wherein the plurality of sets of recording beams are sequentially irradiated to the holographic recording medium in at least one of a driving direction and a direction orthogonal to the driving direction. Method. A recording medium driving device for driving a holographic recording medium capable of recording interference fringes between incident object light and reference light;
A laser light source;
Branched from the laser beam emitted from the laser light source, each of a plurality of recording beams each consisting of object light and reference light is separately guided to the holographic recording medium, and the same number as the number of recording beams. Recording beam optical system of
A spatial light modulator disposed in the object optical system for guiding the object light in each recording beam optical system and modulating the object light in accordance with information to be recorded;
An optical shutter arranged in each of the reference optical systems for guiding the reference light in each recording beam optical system, and capable of individually blocking the reference light;
A control device for controlling the recording medium driving device, the optical shutters, and the spatial light modulators;
Having
A tracking control mirror that reflects the recording beam of one of the plurality of recording beam optical systems and advances and retracts the reflection point;
The next recording beam guided by the next recording beam optical system among the plurality of recording beam optical systems and the first recording beam reflected from the tracking control mirror are reflected in the direction of the holographic recording medium. In addition, each recording beam optical system is sequentially provided with the following tracking control mirror that advances and retracts the reflection point in parallel with the advancing and retreating direction of the reflection point in the tracking control mirror,
Each recording beam optical system is set so that each recording beam is sequentially shifted in at least one of a driving direction in the holographic recording medium and a direction orthogonal thereto, and is incident on the holographic recording medium,
The control device is capable of controlling each of the following control mirrors, and recording on the holographic recording medium is sequentially performed by each recording beam, and during recording, the recording beam is transmitted to the holographic recording medium. The following control mirrors are controlled so that the other recording beam is moved in the direction opposite to the driving direction at the same time, and the recording beam is not recorded. A holographic recording apparatus, wherein the recording beam optical system is blocked by the optical shutter of the beam optical system.

Images