JP2006301141A - Pickup for hologram recording medium and reproducing apparatus for hologram recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pickup for a hologram recording medium in which the number of components can be reduced by integrating a light source and angle adjusting mechanisms. <P>SOLUTION: When a prescribed voltage is applied to the angle adjusting mechanisms 52a, 52b, distortion deformation occurs respectively in the piezoelectric elements constituting the angle adjusting mechanisms 52a, 52b and therefore, the attitude of a movable base 53 is brought down toward the figure 1α with the angle adjusting mechanism 52a as a fulcrum and then, the angle of inclination of the optical axis O-O of reference light Br can be changed. Consequently, the reference light is eventually diffracted by data (interference fringe) to form the page corresponding to the angle of inclination after the change and the reproduction is performed by acquiring the diffracted light output from the recording medium 1 by an imaging means 57. Since the light source 54 and the angle adjusting mechanisms 52a, 52b can be integrally provided, the realization of the reduction of the number of components and space saving is made possible. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pickup for a holographic recording medium that is a recording medium that is angle-multiplexed or wavelength-multiplexed using a hologram, and in particular, a hologram that can reduce the number of parts by integrating a light source and an angle adjusting mechanism. The present invention relates to a pickup for a recording medium and a method for reproducing a hologram recording medium.

  A hologram recording / reproducing apparatus has been developed that irradiates a hologram recording medium with reference light and spatially modulated object light, and records interference fringes of the reference light and object light on the hologram recording medium. At the time of reproduction, the object light at the time of recording can be reproduced by irradiating the hologram recording medium on which interference fringes are recorded with the same reference light as at the time of recording.

  At the time of reproducing a volume hologram using Bragg diffraction, if the irradiation angle of the reference light deviates from the angle of the reference light at the time of recording, phase mismatch occurs and the diffraction efficiency is lowered. When this deviation increases, the diffraction efficiency of the hologram decreases rapidly, making reproduction impossible.

  Hologram angle multiplex recording utilizes such angle selectivity, and if holograms are recorded using reference light with different incident angles, each hologram is only used with reference light having the same incident angle as during recording. Played.

  In addition, phase mismatch occurs in the same way not only with respect to angle but also with changes in wavelength. Therefore, if holograms are recorded using reference light of different wavelengths (wavelength multiplex recording), each hologram is the same as during recording. Reproduction is possible only with reference light of a wavelength.

As a prior art document relating to the above hologram recording medium and its reproducing apparatus, for example, there is the following Patent Document 1.
FIG. 7 etc. in Japanese Patent Laid-Open No. 9-101735

  In the hologram reproducing apparatus described in Patent Document 1, the angle of incidence on the recording medium is adjusted by a galvanometer mirror (angle adjusting mechanism), but a surface emitting laser (VCSEL; Vertical Cavity Surface-Emitting forming light emitting means). Since it is necessary to form the laser (light source) and the galvanometer mirror as separate members, there is a problem that it is difficult to reduce the number of components of the light emitting means itself.

  On the other hand, in the case of the wavelength multiplex recording method, it is only necessary to change the wavelength during reproduction, and thus it is theoretically possible to make the galvanometer mirror unnecessary.

  However, a light source (surface emitting laser) is generally assembled to a base substrate with a heat dissipation function using an adhesive such as a metal bond, and the thickness of the metal bond is controlled to be uniform. That is, it is difficult to fix the light source to the base substrate with high accuracy.

  For this reason, since the light source is fixed at various angles with respect to the base substrate, the laser light emitted from the light source causes an angle shift and can illuminate the entire interference fringe. However, since the light is illuminated in a state in which a part of the interference fringes is missing, there is a problem in that the diffraction efficiency of the hologram is lowered and incomplete reproduction is likely to occur.

  In this respect, if the angle is adjusted by providing a galvanometer mirror between the surface-emitting laser and the recording medium as in the angle multiplex recording method, it is possible to illuminate the entire interference fringes, and the diffraction efficiency is improved. However, if the same galvano mirror is provided alone in the case of the above angle multiplexing, the number of parts increases and the meaning of the wavelength multiplexing is diminished. is there.

  An object of the present invention is to provide a pickup for a hologram recording medium in which the number of parts can be reduced by integrating a light source and an angle adjustment mechanism.

  Another object of the present invention is to provide a hologram recording medium pickup and a method for reproducing a hologram recording medium, which can be reliably reproduced even when the leading end of the reference beam deviates from the recording position on the recording medium. It is said.

The present invention provides a light source that emits reference light that illuminates a recording surface of a recording medium, an imaging unit that acquires diffracted light output from the recording medium, and a tilting posture of the light source that is changed at predetermined angles to form the recording medium. A hologram recording medium reproducing method comprising: a movable base having an angle adjustment mechanism for adjusting an inclination angle of the reference light with respect to the recording surface; and a moving means for moving the movable base,
The recording medium has a large number of recording positions, and each recording position is recorded with multiple data for each page corresponding to the inclination angle or wavelength of the reference light,
When the data recorded on the first page at each recording position is reproduced, the movable base is moved in a state where the inclination angle is set to the first inclination angle, and recorded on the second data at each recording position. When reproducing data, the movable base is moved in a state where the tilt angle is set to a second tilt angle different from the first tilt angle.

  In the above, it is preferable that a movable base for holding the light source is provided, and the angle adjusting mechanism is provided between the movable body and the movable base.

The angle adjusting mechanism is preferably a piezoelectric element.
With the above means, the angle adjustment mechanism can be easily configured.

The present invention also provides a light source that emits reference light that illuminates a recording surface of a recording medium, an imaging unit that obtains diffracted light output from the recording medium, and an inclination posture of the light source that is changed every predetermined angle to perform the recording. A method for reproducing a hologram recording medium, comprising: a movable base having an angle adjustment mechanism for adjusting an inclination angle of the reference light with respect to a recording surface of the medium; and a moving means for moving the movable base,
The recording medium has a large number of recording positions and each recording position is recorded with multiple interference fringes for each angle or wavelength of the reference light,
When the first interference fringe is reproduced, the movable base is moved in a state where the inclination angle is set to the first inclination angle, and when the second interference fringe is reproduced, the inclination angle is the first inclination. The movable base is moved in a state where the second inclination angle different from the angle is set.

  In the above, when the front end of the reference light that illuminates the recording surface of the recording medium is shifted from a predetermined recording position, the movable base is moved so that the front end coincides with the predetermined recording position. It is preferred that

  Furthermore, it is preferable that the moving direction of the movable base is the same as the moving direction of the optical axis of the reference light that moves according to the change in the tilt angle.

  In the above-mentioned means, since the shift direction of the tip of the reference light is the same as the moving direction of the movable base, it is possible to reliably reproduce.

  In the pickup for the hologram recording medium of the present invention, the angle adjustment mechanism for adjusting the tilt angle and the light source can be provided integrally, so that the number of parts can be reduced and space saving can be realized. Therefore, the pickup for the hologram recording medium can be reduced in size.

  In the method for reproducing a hologram recording medium, for example, even if the tip of the reference light deviates from the recording position corresponding to the target address, the reference light is adjusted by adjusting the amount of movement of the movable base. Since the tip of the recording medium can be aligned with the recording position corresponding to the target address, reproduction can be performed even when the light source is roughly attached to the movable base.

  FIG. 1 is a sectional view showing a hologram reproducing apparatus as an embodiment of the present invention, and FIG. 2 is a partial sectional view showing a part of FIG.

  A hologram reproducing apparatus A shown in FIG. 1 is for reading out hologram information recorded on the recording medium 1, and is mounted on an electronic apparatus such as a computer or a video reproducing apparatus.

  As shown in FIG. 1, the hologram reproducing apparatus A includes a holding unit 10 that holds the recording medium 1 and a reproduction mechanism unit (pickup) 20 provided above the holding unit 10.

  The recording medium 1 shown in this embodiment is a reflective recording medium. As shown in FIG. 1 or 2, the recording medium 1 has a card shape or a chip shape, and is provided with a first flat plate 1a having light transmissivity provided on the recording surface side (Z1 side) and a back surface (Z2). And a second flat plate 1b provided on the side). A gap 1c is formed between the first flat plate 1a and the second flat plate 1b. The gap 1c is filled with the optical recording material 2. Sealing members 1 d and 1 d for preventing leakage of the optical recording material 2 are provided at both ends of the recording medium 1.

  Such a recording medium 1 can record these interference fringes on the optical recording material 2 by irradiating laser light from a light source as reference light and as object light via a spatial modulator. . At this time, by changing the wavelength of the laser light or the angle of the reference light, it is possible to perform three-dimensionally multiplex recording at the same recording position, and such interference is caused at each recording position 3 on the recording medium 1. Stripes are recorded in multiple.

  As the optical recording material 2, for example, a photopolymer or a known silver chloride-based material can be used. Such an optical recording material 2 is described in, for example, Japanese Patent Application Laid-Open No. 11-52824.

  Such a recording medium 1 can have various shapes such as a disk shape, a card shape, or a chip shape. Even in the case of a chip shape of several centimeters, it has an extremely large capacity of 1 TB (terabyte) or more. It is. Therefore, it is very convenient as a recording medium (removable recording medium) that can be easily carried when it is made into a card or a chip.

  The recording medium 1 is inserted from an insertion port (not shown) provided in a housing (not shown) and is held by holding means 10 provided in an electronic device. The holding means 10 has holding portions 13 and 13 and biasing members 14 and 14 provided on both sides in the X direction. The recording medium 1 is urged by the urging members 14 and 14, and both end portions thereof are brought into contact with the holding portions 13 and 13. That is, the recording medium 1 is elastically held while being sandwiched between the urging members 14 and 14 and the holding portions 13 and 13. An opening 10A is provided between one holding part 13 and the other holding part 13, and the recording surface of the recording medium 1 is exposed in the Z1 direction through the opening 10A.

  The reproduction mechanism means (pickup) 20 has a holder 30 formed in a U-shaped cross section and a movable base 40 provided inside the holder 30. Legs 30A and 30B are provided at both ends in the X direction of the holder 30, and through holes 30a and 30b penetrating in the Y direction are formed in the leg portions 30A and 30B in parallel with each other. Yes.

  A female screw is threaded on the inner wall of one through hole 30a, and a screw shaft 31 having a male thread threaded on the outer peripheral surface is inserted into the through hole 30a. A guide shaft 32 is inserted through the other through hole 30b. Both ends of the screw shaft 31 and the guide shaft 32 are provided between support members (not shown) so as to be parallel and horizontal to each other. One screw shaft 31 is rotatably supported by the support member. A drive motor, a reduction gear mechanism, and the like (not shown) are provided on the support member, and the screw shaft 31 and the motor output shaft of the drive motor are connected via the reduction gear mechanism. For this reason, when the drive motor rotates, the driving force is transmitted to the motor output shaft, the reduction gear mechanism, the screw shaft 31 and the internal thread of the through hole 30a of the holder 30, so that it depends on the rotation direction of the motor output shaft. Thus, the holder 30 can be screwed forward and backward in the Y direction (direction perpendicular to the paper surface) in the figure. That is, the pair of screw shaft 31 and guide shaft 32, the drive motor, the motor output shaft, the reduction gear mechanism, and the like constitute first moving means for screw-feeding the holder 30 in the Y-axis direction.

  On the other hand, between one leg 30A and the other leg 30B of the holder 30, a pair of screw shafts 41 and guide shafts 42 extending in the X direction shown in the drawing are spaced from each other at a predetermined interval in the Y direction shown in the drawing. It is installed in a parallel and horizontal state. The screw shaft 41 and the guide shaft 42 are respectively inserted into through holes (not shown) provided in the movable base 40. The holder 30 is equipped with a drive motor (not shown), a reduction gear mechanism, and the like that constitute the second moving means, and by applying a drive force to the screw shaft 41, the movable base 40 is connected to the drive motor. Screws can be fed in the X-axis direction shown in the figure according to the direction of rotation.

  That is, the first moving means can move the holder 30 carrying the movable base 40 in the Y direction, and the second moving means can move only the movable base 40 in the X direction. The first moving means and the second moving means function as moving means for moving the movable base 40 in the horizontal direction (X and Y directions).

  As shown in FIG. 1, the movable base 40 has a case 40A having a substantially box shape, and a reproducing means 50 is provided in the case 40A.

  As shown in FIGS. 1 to 3, the reproducing means 50 has a base member 51 serving as a reference. The base member 51 may be separate from the case 40 </ b> A, or the ceiling surface of the case 40 </ b> A may also serve as the base member 51.

  On the lower surface of the base member 51, an angle adjusting mechanism 52 (indicated by 52a and 52b individually) for adjusting the optical axis tilt angle of the reproduction light and an imaging means 57 are fixed. The angle adjusting mechanisms 52a and 52b are formed of, for example, a piezoelectric element, and can be deformed and deformed according to the voltage application direction. The image pickup means 57 is an element that reads information of the reproduction light diffracted by the recording medium 1 and converts it into an electrical signal, such as a CCD or CMOS image sensor.

  A movable base 53 having a substantially trapezoidal shape is fixed to the lower ends of the angle adjusting mechanisms 52a and 52b. The movable table 53 is formed with a slope 53a and an opening hole 53b penetrating perpendicularly to the slope 53a. A light source 54 made of a surface emitting laser (VCSEL) is provided in the opening hole 53b. Therefore, the optical axis OO of the laser light (reference light) emitted from the light source 54 is perpendicular to the inclined surface 53a and is incident on the recording surface of the recording medium 1 (90 ° -θ). ) And is set to be illuminated. A cylindrical lens holder 56 is fixed around the light source 54, and a focusing lens 55 for holding the laser beam to a certain point on the recording medium 1 is held in the lens holder 56. The light source 54 and the focusing lens 55 constitute light emitting means for irradiating the recording medium 1 with the laser light as reference light Br.

  As indicated by a broken line in FIG. 2, the imaging means 57 may also be configured to be fixed to the inclined surface 58a of the pedestal 58 having a predetermined inclined surface 58a. In this configuration, since the surface of the imaging means 57 and the optical axis of the diffracted light are easily orthogonal, it is possible to acquire diffracted light as a clearer image, and reduce the generation of error signals during reproduction. Can do.

  Further, the hologram reproducing apparatus A is provided with control means (not shown) for controlling the operations of the first and second moving means, the light emitting means, the angle adjusting mechanism 52, the imaging means 57, and the like.

The reproducing operation of the hologram reproducing apparatus will be described.
(Basic playback operation)
When the recording medium 1 is held by the holding means 10, the control means starts the respective drive motors constituting the first moving means and the second moving means, whereby the holder 30 and the movable base 40 are started. Move. At this time, the movable base 40 is moved so that the reference light Br emitted from the light emitting means mounted inside comes to the initial recording position (initial address) on the recording medium 1. Alternatively, when the reproduction start position is designated by an operator or the like, the control means moves to the corresponding address on the recording medium 1.

  Further, the control means gives a predetermined voltage to the light source 54 and causes the light source 54 to output laser light. At this time, the laser light illuminates the initial recording position on the initial address as reference light. Next, the control means applies a predetermined voltage to one or both of the angle adjustment mechanisms 52a and 52b, thereby causing distortion deformation in the piezoelectric elements constituting the angle adjustment mechanisms 52a and 52b. For example, in the case indicated by the broken line in FIG. 3, no voltage is applied to one angle adjustment mechanism 52a, and only the other angle adjustment mechanism 52b is shown in the Z direction in the figure by applying a voltage only to the other angle adjustment mechanism 52b. And is deformed in a contracting direction. As a result, the posture of the movable base 53 can be tilted in the α1 direction shown in the figure. For this reason, the inclination posture of the light source 54 is changed, and the optical axis O-O (initial inclination angle = θ) of the reference light Br is composed of an optical axis O1-O1 having an inclination angle θ1 indicated by a broken line in the drawing. The light Br1 can be transferred.

  As a result, the reference beam Br1 forms interference fringes that form, for example, data (index data or the like) recorded on the first page among a plurality of data multiplexed and recorded for each page at the initial recording position. The diffracted light at this time is emitted from the recording medium 1 toward the image pickup means 57.

  Therefore, the control means can reproduce the data recorded on the first page from the electric signal obtained by converting the diffracted light by the imaging means 57. The contents of this data are re-recorded on a memory or hard disk in the computer or displayed on a display, for example.

(Continuous playback operation)
Next, the control means continuously reproduces predetermined data (data to be read) recorded over a plurality of pages at a plurality of recording positions on the recording medium 1 by the following reproducing method.

  First, the control means moves the first moving means and / or the second moving means in a state where the optical axis OO of the light source 54 is fixed to an arbitrary inclination angle (for example, an initial inclination angle = θ). Driven to move the movable base 40 in the X direction and / or Y direction. At this time, the reference light Br emitted from the reproducing means mounted on the movable base 40 can sequentially illuminate each recording position along the moving direction of the movable base. For this reason, only data (interference fringes) recorded on a page corresponding to an arbitrary inclination angle at each recording position can be reproduced in order.

  For example, in FIG. 1, when the movable base moves in the X1 direction with the first tilt angle set, the first page at the recording position 3a → the first page at the recording position 3b → the recording position 3c. Only data (interference fringes) recorded on the first page in the order of the first page → can be reproduced.

  When the reproduction of the first page is completed, the control means changes the combination of voltages applied to the angle adjusting mechanisms 52a and 52b, and the data forming the second page when the reference light Br illuminates each recording position. The angle is changed to the second inclination angle at which diffraction occurs due to (interference fringes). In this state, similarly to the above, the movable base 40 is moved in the X1 direction in the order of the recording position 3a → the recording position 3b → the recording position 3c →. Only data can be continuously reproduced in order.

  Similarly, the movable base 40 is moved in the X1 direction in the order of the recording position 3a, the recording position 3b, the recording position 3c, and so on, with the inclination angle corresponding to each page being set. The data recorded on each page can be reproduced continuously in order.

  In addition, even when the movable base 40 is moved in the Y direction perpendicular to the paper surface while the optical axis OO of the light source 54 is fixed at a certain inclination angle, it is recorded on each page at each recording position. It is possible to continuously reproduce the data that are present.

  However, in the case of a reproducing method in which both the direction in which the optical axis OO of the reference light Br moves in accordance with the change in the tilt angle θ and the direction in which the movable base 40 moves are in the X direction in the figure, the light source When the inclination angle θ of the reference light Br is set to a predetermined angle by swinging the inclination angle 54 in the X direction, for example, the tip (spot) of the reference light Br is displaced from the recording position corresponding to the target address. Even in such a case, by adjusting the moving amount of the movable base 40, it is possible to easily align the tip of the reference light Br to the recording position corresponding to the target address.

  The angle adjustment mechanism in this case may be the angle adjustment mechanism 52 that adjusts the inclination angle of the light source 54 as described above, or a conventional galvanometer mirror instead of the angle adjustment mechanism 52. There may be. However, the above configuration is advantageous in that the angle adjusting mechanism and the light source 54 can be integrally formed, and thus the number of partial points is reduced and the size is reduced due to space saving.

  By the way, the reproduction of data multiplexedly recorded on the recording medium 1 can be performed by setting the inclination angle θ as long as the black diffraction conditional expression (2 d sin θ = nλ, d is the inter-grating distance, θ is the inclination angle, and λ is the wavelength). Not only the method of changing (angle modulation method) but also the direction of changing the wavelength λ (wavelength modulation method) is possible. In this case, a light source 54 capable of selectively outputting a wavelength is used instead of the angle adjusting mechanism 52.

  However, if the small light source 54 has a narrow selectable wavelength band and the mounting accuracy of the light source 54 fixed to the base member 51 is low, the laser light emitted from the light source 54 is likely to cause an angle shift. The laser light (reference light) cannot illuminate the entire interference fringes recorded at each recording position, and as a result, the diffraction efficiency of the hologram is lowered, resulting in incomplete reproduction.

  Therefore, also in the wavelength modulation method, the tilt angle θ of the reference light Br can be adjusted by changing the posture of the movable base 53, that is, the tilt posture of the light source 54, using the angle adjustment mechanism as in the case of the angle modulation method. Thus, even when the reproduction is incomplete only by changing the wavelength, the reference light Br illuminates the entire interference fringes recorded at each recording position by driving the angle adjusting mechanism in an auxiliary manner. Therefore, complete hologram reproduction can be performed. That is, it is preferable that the wavelength modulation type reproducing apparatus be configured such that the same angle adjustment mechanism as described above can be used supplementarily.

  Note that such an angle adjustment mechanism may be the angle adjustment mechanism 52 that adjusts the attitude of the movable base as described above, or may be a conventional galvanometer mirror. In the wavelength modulation hologram reproducing apparatus having such an angle adjusting mechanism, it is possible to use a reproducing method in which the movable base 40 is moved in accordance with the driving of the angle adjusting mechanism as described above.

Sectional drawing which shows the hologram reproduction apparatus as embodiment of this invention, The fragmentary sectional view which expands and shows a part of FIG. FIG. 2 is a partial sectional view similar to FIG. 2 showing the operation of the angle adjustment mechanism;

Explanation of symbols

1 Recording medium 10 Holding means 20 Reproducing mechanism means (pickup)
30 Holder 40 Movable base 50 Reproducing means 51 Base members 52, 52a, 52b Angle adjustment mechanism (piezoelectric element)
53 Movable base 54 Light source (surface emitting laser (VCSEL))
55 Converging lens 56 Lens holder 57 Imaging means

Claims (6)

A light source that emits laser light as reference light; a focusing lens that focuses the reference light and irradiates the recording medium; an imaging unit that acquires diffracted light output from the recording medium; and at least the light source, the focusing lens, and A pickup for a hologram recording medium comprising an imaging means and a movable base provided movably along the recording medium,
A pickup for a hologram recording medium, wherein the light source has an angle adjustment mechanism for adjusting an inclination angle formed between an optical axis of the reference light and a recording surface of the recording medium.   A pickup for a hologram recording medium, wherein a movable base for holding the light source is provided, and the angle adjusting mechanism is provided between the movable body and the movable base.   3. The pickup for a hologram recording medium according to claim 1, wherein the angle adjusting mechanism is a piezoelectric element. A light source that emits reference light that illuminates the recording surface of the recording medium, an imaging unit that acquires diffracted light output from the recording medium, and an inclination posture of the light source is changed at predetermined angles with respect to the recording surface of the recording medium. A method for reproducing a hologram recording medium, comprising: a movable base having an angle adjustment mechanism for adjusting an inclination angle of the reference light; and a moving means for moving the movable base,
The recording medium has a large number of recording positions, and each recording position is recorded with multiple data for each page corresponding to the inclination angle or wavelength of the reference light,
When the data recorded on the first page at each recording position is reproduced, the movable base is moved in a state where the inclination angle is set to the first inclination angle, and recorded on the second data at each recording position. A method for reproducing a hologram recording medium, wherein when reproducing data, the movable base is moved in a state where the inclination angle is set to a second inclination angle different from the first inclination angle.   The movable base is moved so that the tip of the reference light that illuminates the recording surface of the recording medium is displaced from a predetermined recording position so that the tip matches the predetermined recording position. The method for reproducing a hologram recording medium according to claim 4.   6. The method for reproducing a hologram recording medium according to claim 4, wherein the moving direction of the movable base is the same as the moving direction of the optical axis of the reference light that moves according to the change in the tilt angle. .

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