KR100624264B1 - Apparatus for controlling angle/tracking servo in a holographic regeneration system - Google Patents

Abstract

The present invention relates to an angle / tracking servo control apparatus for a holographic reproduction system, comprising: a first optical system for providing a first optical path for injecting a reproduction reference light into a holographic recording medium at a predetermined angle; and a data layer of the recording medium. The reproduction signal detector for detecting the reproduction signal light diffracted by the second optical system providing a second optical path and the center of the reproduction signal light by the normal angle of the reproduction reference light incident on the recording medium, respectively, in the positive and negative directions. The result of mutual comparison of the light detection value by the 1st, 2nd servo light detector which consists of several light-receiving elements which are arrange | positioned at distance, respectively, and detects a reproduction signal light via a 2nd optical system, and the 1st, 2nd servo light detection part. The light-receiving elements which generate an angle servo control signal in accordance with the above, and constitute one of the light detectors of the first and second servo light detectors A control unit for generating a tracking servo control signal according to a result of comparing light detection values, a first actuator for performing angle servo by adjusting an angle of incidence of a recording medium of the reproduction reference light according to the angle servo control signal, and a tracking servo control signal And a second actuator that performs tracking servo by adjusting the playback position on the recording medium by the reproduction optical detector according to the present invention, and supports both angle servo control and tracking servo control with minimized components. Not only the structure of the system is simplified, but also the manufacturing cost of the system is reduced.

Description

Angle / Tracking Servo Control System for Holographic Playback System {APPARATUS FOR CONTROLLING ANGLE / TRACKING SERVO IN A HOLOGRAPHIC REGENERATION SYSTEM}

1 is a block diagram of a typical holographic ROM playback system;

2A and 2B are views showing the angle of reproduction and the angle of reproduction light of the holographic recording medium to explain the angle servo basic principle of the angle / tracking servo control apparatus according to the present invention;

3A and 3B are diagrams showing the reproduction angle and the reproduction light angle of the disc-shaped holographic recording medium in order to explain the angle servo basic principle of the angle / tracking servo control apparatus according to the present invention;

4 is a view showing an arrangement position of a servo light detector for receiving servo reproduction light for servo control in an angle / tracking servo control device according to the present invention;

5 is a configuration diagram of a holographic ROM reproducing system to which an angle / tracking servo control device is applied according to the present invention;

6a and 6b is a view showing a light detection state before and after the completion of the angle servo to explain the angle servo control process by the angle / tracking servo control device according to the present invention;

7A and 7B illustrate light detection states before and after completion of a tracking servo to explain a tracking servo control process by the angle / tracking servo control device according to the present invention.

The present invention relates to an angle / tracking servo control apparatus for a holographic reproducing system, and more particularly to an angle servo control and a tracking servo control for reproducing data stored in a recording material layer of a holographic recording medium. An angle / tracking servo control device.

Currently, research and development of holographic recording / reproducing apparatuses capable of storing hundreds to hundreds of Gbytes in optical recording media such as optical disks for the large-capacity and high-speed processing of data storage memories are actively underway.

Referring to a general holographic recording process, a data mask is disposed on a disk, which is a holographic recording medium, and a conical mirror is disposed below the disk. When parallel light is projected onto the data mask, the parallel light passes through a bit pattern in the form of a hole in the data mask and is irradiated to the disk as signal light. Parallel light is projected to the lower part of the disk, and the reference light having a constant angle in the radial direction of the disk is irradiated through the inclined surface of the conical mirror. This signal light and the reference light meet the recording material layer of the disc, and the holographic data in bits according to the pattern of the first data mask is recorded. Instead of the conical mirrors used, conical mirrors with different mirror tilt angles can be used to write new data to the disc using Angular Multiplexing.

A pickup device for reproducing data stored through such a recording process according to the related art is incident through a first optical system that is generated from the light source 10 and provides a first optical path L1 as shown in FIG. 1. A mirror 20 for reflecting the reproduced reference light to be incident on the recording medium 1 at a predetermined angle, and an actuator for adjusting the incident angle of the recording medium 1 of the reproduction reference light by adjusting the arrangement angle of the mirror 20 (not shown) And a light detector 30 for detecting the reproduction signal light incident on the recording medium 1 and diffracted in the recording material layer through a second optical system provided by the second optical path L2.

The first optical system includes a reducer 50 that deforms the light emitted from the light source 10, and an aperture that scans the light passing through the reducer 50 to the mirror 20 through pores to provide a reproduction reference light. (aperture) 60. The second optical system includes an objective lens 71, a slit 73, and a condenser lens 75 for injecting light diffracted from the recording medium 1 into the light detector 30.

In the holographic pickup device configured as described above, when the reproduction reference light is incident on the recording medium 1 at a predetermined angle (reference light incident angle using oxygen) by the mirror 20 whose arrangement angle is adjusted by an actuator (not shown). The reproduction signal light diffracted in the recording material layer of the recording medium 1 is detected by the light detector 30. Then, new data can be reproduced from the recording medium 1 by adjusting the placement angle of the mirror 20 through an actuator (not shown) to adjust the incident angle of the recording medium 1 of the reproduction reference light.

On the other hand, the holographic ROM reproducing system uses an angular superposition technique for recording data on the disc as described above, so that in order to reproduce the angular superimposed recorded data, an angle servo for adjusting the incident angle when the reproduction reference light is incident on the recording medium is used. Control is essential.

As an angle servo control technology for this purpose, the applicant has proposed a "angle servo control device for holographic reproduction system" of patent application No. 2004-091732 (November 11, 2004).

The angle servo control device of the arc comprises a first and second angle servo optical detectors spaced apart from each other in a positive (+) direction and a negative (-) direction at a center of the reproduction signal light by the normal angle of the reproduction reference light incident on the recording medium. The angle servo control is performed by adjusting the incident angle of the reproduction reference light incident on the recording medium according to the comparison result of the light detection values by the first and second angle servo light detectors.

In addition, the holographic ROM reproducing system requires tracking servo control to accurately reproduce data recorded on a desired track when the recording medium, i.e., the optical disc rotates at high speed.

As a tracking servo control technique for this purpose, various methods have been proposed, such as a technique of performing a tracking servo control by using a tracking signal reproduced by a track pattern after recording a track pattern having a constant data value when recording holographic data.

However, the conventional angle servo control technique and the tracking servo control technique as described above are essential to be applied to the holographic ROM regeneration system, but are proposed as separate techniques using different principles. The holographic ROM reproducing system employing both the angle servo control device and the tracking servo control device has a problem in that its structure is complicated and the manufacturing cost of the system is increased.

The present invention has been proposed to solve such a problem of the prior art, and the optical detection means for receiving the reproduction signal light for angle servo control in the "angle servo control device for holographic reproduction system" of the patent application 2004-091732 The purpose of the present invention is to improve tracking function and to support tracking servo control.

An angle / tracking servo control apparatus for a holographic reproducing system according to the present invention for achieving this object comprises a first optical path for injecting a reproduction reference light generated from a light source into a holographic recording medium at a predetermined angle. A reproduction optical detector for detecting a reproduction signal light incident on the recording medium and diffracted by the data layer of the recording medium through a second optical system providing a second optical path, and a normal angle of the reproduction reference light incident on the recording medium First and second servo light comprising a plurality of light-receiving elements arranged to be spaced apart from each other in a positive (+) direction and a negative (-) direction by a center of the reproduction signal light by the second optical system. An angle servo control signal is generated according to a result of the mutual comparison between the detection unit and the light detection values of the first and second servo light detection units. A control unit for generating a tracking servo control signal according to a result of comparing the light detection values of the light receiving elements constituting any one of the light detection units with each other, and the angle of incidence of the recording medium of the reproduction reference light according to the angle servo control signal. A first actuator for adjusting the angle servo and a second actuator for adjusting the reproducing position on the recording medium by the reproducing optical detector according to the tracking servo control signal to perform the tracking servo.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. This embodiment allows for a better understanding of the objects, features and advantages of the present invention. However, the present invention is not limited to this embodiment, of course.

Prior to describing the angle / tracking servo control device for the holographic reproduction system according to the present invention, the basic principle of the angle servo control will be described with reference to FIGS.

As shown in Fig. 2A, when the data is recorded on the holographic recording medium at an angle indicated by a straight line and the data is reproduced at an angle indicated by a dotted line, the reproduction signal light emitted from the holographic recording medium is reduced in intensity. In addition, the exit angle changes. FIG. 2B shows the angle of light to be reproduced upon reproduction with conjugation light. 0, a, 2a, 3a on the holographic recording medium; If a data is recorded at an angle of angular selectivity (a is called an angular selectivity) and then played back at an a / 2 angle during playback, a layer that is 0 degrees is considered to be incident at a relative + a / 2 angle. At the time of reproduction, the reproduction signal light is reproduced while showing an angle difference of a / 2 relative to the angle at which the signal light is incident upon recording.

FIG. 3A shows a state in which the basic principles of FIGS. 2A and 2B have been applied to the disc-shaped holographic recording medium 1. Assuming that the linear light b1 is the correct angle (normal angle) for data reproduction, the reproduced light is emitted as a straight line, and when the dashed light b2 is incident for the data reproduction, the reproduced light is an angle that is distorted at the normal angle. Is emitted as shown by the dotted line in FIG. 3A. Accordingly, it can be seen that when the data recorded in the disc-shaped holographic recording medium 1 is reproduced in 3a / 2, the data recorded in a and 2a are reproduced as shown in Fig. 3B. The effect of incident on the layer a at an angle of + a / 2 is shown, and the effect of incident on the layer 2a at -a / 2 is shown, so that the reproduction signal light has an angle as shown in FIG. 3B.

According to the basic principle as described with reference to FIGS. 2A to 3B, when the plurality of servo light detectors 100 are arranged on the extension line of the reproduction signal light as shown in FIG. 4, the reproduction signal light detected by each servo light detector 100 is provided. When the powers are the same, it can be said that the angle of the reproduction reference light incident on the disc-shaped holographic recording medium 1 is correct.

The holographic reproducing system to which the angle / tracking servo control device of the present invention which follows the angle servo basic principle described above with reference to FIGS. 2 to 4 is applied as shown in FIG. 5. FIG. 5 is a block diagram of a holographic ROM reproducing system to which an angle / tracking servo control device according to the present invention is applied, and in comparison with the holographic ROM reproducing system shown in FIG.

Referring to FIG. 5, the angle servo control apparatus of the present invention reflects the reproduction reference light incident from the light source 10 and incident through the first optical system providing the first optical path L1 to the recording medium 1. Reproducing light detecting unit 30 for detecting the reproduction signal light incident on the recording medium 1 and diffracted in the recording material layer through the second optical system provided by the second optical path L2. And first and second servo light detectors 110 and 120 for detecting the reproduction signal light incident on the recording medium 1 and diffracted in the recording material layer through a second optical system provided by the second optical path L2. And a control unit 200 for generating an angle servo control signal and a tracking servo control signal according to the comparison result of the light detection values by the first and second servo light detection units 110 and 120, and the angle servo of the control unit 200. By adjusting the placement angle of the mirror 20 according to the control signal, An actuator (not shown) for adjusting the angle of incidence of the medium 1 to perform angle servo, and a reproducing position on the recording medium 1 by the reproducing optical detector 30 according to the tracking servo control signal of the control unit 200. And an actuator (not shown) to adjust tracking to perform tracking servo.

The first optical system includes a reducer 50 that deforms the light emitted from the light source 10, and an aperture 60 that scans the light passing through the reducer 50 to the mirror 20 through pores to provide a reproduction reference light. It includes. The second optical system includes a lens 71, a slit 73, and a lens 75 for injecting light diffracted from the recording medium 1 into the light detector 30.

A plurality of slits 73 are diffracted by a layer recorded at an initial incidence angle and a close angle as shown in FIG. 3B in a state where the initial incident angle of the reproduction reference light is determined by the control unit 200 and exits from the recording medium 1. Has a wide hole so that the reproducing signal lights a 'and 2a' can be detected and detected by the first and second servo light detectors 110 and 120, and according to the tracking servo control signal of the controller 200. Its position is adjusted by an actuator (not shown) that performs tracking servo.

The first servo light detector 110 is spaced a predetermined distance from the center of the reproduction signal light by the normal angle in a negative (-) direction, and the second servo light detector 120 is fixed at the center of the reproduction signal light by the normal angle. The first and second servo light detectors 110 and 120 are disposed to be symmetrical with respect to the light detector 30 at a distance of +) in a predetermined distance. 7A and 7B, the first servo light detector 110 includes a plurality of light receiving elements A and B, and the second servo light detector 120 also includes a plurality of light receiving elements. It consists of (C, D).

The pickup and angle / tracking servo control process by the holographic reproduction system according to the present invention configured as described above will be described in detail as follows.

First, the controller 200 determines the initial angle of the reproduction reference light incident on the recording medium 1, and then controls the actuator to adjust the placement angle of the mirror 20. As a result, the light emitted from the light source 10 is reflected by the mirror 20 in which the arrangement angle is adjusted, and the reproduction reference light is incident on the recording medium 1 at a predetermined angle (proximity of the reference light incident angle using oxygen).

The reproduction signal light incident on the recording medium 1 is diffracted by the data layer of the recording medium 1 so that the reproduction signal light is incident on the lens 71 through the second optical path L2.

As a result, the reproduction signal light diffracted in the data layer passes through the lens 71, the slit 73, and the lens 75 sequentially to the reproduction light detector 30 and the first and second servo light detectors 110 and 120. Is detected.

Here, the light amount values detected by the individual light receiving elements A, B, C, and D constituting the first and second servo light detectors 110 and 120 are transferred to the control unit 200, respectively, and the control unit 200. ) Generates a new angle servo control signal according to the comparison result of the light detection values by the first and second servo light detection units 110 and 120, and the actuator is incident on the recording medium 1 according to the angle servo control signal. The incident angle of the reproduction reference light is corrected.

In the angle servo control process, when the reproduction reference light is incident on the recording medium 1 by the initial arrangement angle of the mirror 20, as shown in FIG. 6A or FIG. The plurality of reproduction signal lights a 'and 2a' diffracted by the first and second servo light detectors 110 and 120 are detected.

Since the first servo light detector 110 and the second servo light detector 120 are arranged symmetrically with respect to the light detector 30, the center of the reproduction signal light a 'is the first servo as shown in FIG. 6A. On the contrary, the center of the reproduction signal light 2a 'is closer to the second servo light detector 120 when away from the molten light detector 110. At this time, the light detection by the second servo light detection unit 120 is higher than the light detection value by the first servo light detection unit 110 due to the selectivity curve characteristics of the reproduction signal lights a 'and 2a'. The value is larger, and the control unit 200 controls the actuator through the angle servo control signal to correct the incident angle of the reproduction reference light incident on the recording medium 1. On the contrary, the angle servo control is performed even when the light detection value of the first servo light detection unit 110 is greater than the light detection value of the second servo light detection unit 120.

As shown in FIG. 6B, the distance between the center of the reproduction signal light a 'and the first servo light detector 110 is equal to the distance between the center of the reproduction signal light 2a' and the second servo light detector 120. When the same angle servo is completed, the light detection value by the first servo light detector 110 and the light detection value by the second servo light detector 120 are the same. That is, the controller 200 may include the sum of the light detection values of the light receiving elements A and B of the first servo light detection unit 110 and the light receiving elements of the second servo light detection unit 120. When the sum of the light detection values by C and D is the same as each other, it is determined that the correct angle servo is completed.

Here, the state where the correct angle servo is completed is an angle at which the light detection values of the first and second servo light detectors 110 and 120 are the same. However, even after the threshold range is set, even when the light detection difference between the first and second servo light detectors 110 and 120 is included in the threshold range, it may be determined to be a normal angle servo state.

Next, referring to the tracking servo control process, when the plurality of reproduction signal lights a 'and 2a' are detected by the first and second servo light detectors 110 and 120 by the initial position of the slit 73, The control unit 200 compares the light detection values of the light receiving elements A and B of the first servo light detecting unit 110 with each other, and the light receiving elements of the second servo light detecting unit 120. The light detection values by (C, D) are compared with each other.

Here, when the position of the slit 73 is incorrect, as shown in FIG. 7A due to poor tracking, the reproduction signal light represented by the dotted line is received toward the A and C elements among the light receiving elements, or the B and D elements are received. It is received toward the side.

Accordingly, the controller 200 determines a mismatch as a result of comparing the light detection values of the light receiving elements A and B constituting the first servo light detection unit 110 with each other, and the second servo light detection unit. As a result of comparing light detection values by the light receiving elements C and D constituting 120 with each other, a mismatch is also determined. As a result, the control unit 200 generates a tracking servo control signal, and the actuator performs tracking servo control in which the actuator adjusts the position of the slit 73 according to the tracking servo control signal.

After the tracking servo control is performed to adjust the position of the slit 73 and the slit 73 is disposed at the correct position, as shown in FIG. 7B, the reproduction signal light represented by the dotted line is the light receiving elements A and B. , C and D) are received symmetrically about the boundary line.

Accordingly, the controller 200 determines a match as a result of comparing the light detection values of the light receiving elements A and B constituting the first servo light detection unit 110 with each other, and the second servo light detection unit. As a result of comparing the light detection values by the light receiving elements C and D constituting 120 with each other, a match is also determined. At this time, the controller 200 recognizes that the tracking servo control is completed. Here, the tracking servo control can be performed even if only the light detection values of the light receiving elements of the first and second servo light detection units 110 and 120 are compared with each other. In the state where the accurate tracking servo is completed, the light detection values of the individual light receiving elements in the first and second servo light detectors 110 and 120 are the same angle. However, even after the threshold range is set, it may be determined to be a normal tracking servo state even when the light detection difference is included in the threshold range.

As described above, the holographic data is reproduced according to the light quantity value detected by the reproduction light detector 30 in the state where the angle servo and tracking servo control are completed.

In the foregoing description of the present invention, only one embodiment has been described, but it is obvious that the technology of the present invention can be easily modified by those skilled in the art. Such modified embodiments should be included in the technical spirit described in the claims of the present invention.

As described above, the angle / tracking servo control apparatus of the present invention supports both angle servo control and tracking servo control with minimal components, thereby simplifying the structure of the holographic ROM reproducing system and making the system cost less. There is a saving effect.

Claims (5)

A first optical system providing a first optical path for causing the reproduction reference light generated from the light source to enter the holographic recording medium at a predetermined angle; A reproduction light detector for detecting a reproduction signal light incident on the recording medium and diffracted by the data layer of the recording medium through a second optical system providing a second optical path; Spaced apart from each other in a positive (+) direction and a negative (-) direction at a center of the reproduction signal light by the normal angle of the reproduction reference light incident on the recording medium to detect the reproduction signal light through the second optical system, respectively. A first and second servo light detector comprising a plurality of light receiving elements; An angle servo control signal is generated according to a result of mutual comparison of light detection values by the first and second servo light detectors, and the light receiving elements forming one of the light detectors from the first and second servo light detectors. A control unit for generating a tracking servo control signal according to a result of comparing light detection values with each other, A first actuator configured to perform angle servo by adjusting an angle of incidence of a recording medium of the reproduction reference light according to the angle servo control signal; A second actuator for performing tracking servo by adjusting the reproduction position on the recording medium by the reproduction optical detection unit according to the tracking servo control signal Angle / tracking servo control device for a holographic reproduction system comprising a. The method of claim 1, And the control unit is configured to complete the angle servo control at a position where the light quantity values detected by the first and second angle servo light detectors are equal to each other. The method of claim 1, The control unit controls the angle / tracking servo control for the holographic reproducing system, wherein the angle servo control is completed at a position where a difference between the light quantity values detected by the first and second angle light detectors falls within a preset threshold range. Device. The method of claim 1, The controller is configured to complete the tracking servo control at a position where the amount of light detected by the light receiving elements of the first and second servo light detectors is equal to each other. Angle / tracking servo control for the system. The method of claim 1, The controller may be configured to complete the tracking servo control at a position where a difference between the light quantity values detected by the light receiving elements of the first and second servo light detectors is included in a preset threshold range. Angle / tracking servo control for a holographic playback system.

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