KR100579634B1 - Angle Servo Control for Holographic Playback System - Google Patents

Abstract

The present invention relates to an angle servo control apparatus for a holographic reproducing system, comprising: a first optical system for providing a first optical path for injecting a reproduction reference light generated from a light source into a holographic recording medium at a predetermined angle; And a reproduction light detector for detecting the reproduction signal light diffracted by the data layer of the recording medium through a second optical system providing a second optical path, and at the center of the reproduction signal light at the normal angle of the reproduction reference light incident on the recording medium. First and second angle servo light detectors disposed at a predetermined distance apart in a positive (+) direction and a negative (-) direction, respectively, for detecting a reproduction signal light through a second optical system, and a first and second angle servo light detectors; And a control unit for adjusting angle of incidence of the reproduction reference light incident on the recording medium according to the comparison result of the light detection values. In addition, according to the comparison result of the light quantity values detected by the plurality of angle servo light detectors for receiving the reproduction signal light emitted from the holographic recording medium, an accurate angle servo control can be performed using the characteristic curve characteristic. have.

Description

Angle servo control device for holographic reproduction system {APPARATUS FOR CONTROLLING ANGLE-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 of the holographic recording medium and the angle of reproduction light to explain the basic principle of the angle servo control device according to the present invention;

3A and 3B show a reproduction angle and a reproduction light angle of a disc-shaped holographic recording medium for explaining the basic principle of the angle servo control device according to the present invention;

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

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

6A and 6B illustrate light detection states before and after angle servo completion in an angle servo control device in order to explain the angle servo control process by the angle servo control device according to the present invention.

The present invention relates to an angle servo control apparatus for a holographic reproducing system, and more particularly to an angle servo for adjusting an angle at which a reproduction reference light is incident on a recording medium in order to reproduce data stored in a recording material layer of the holographic recording medium. It relates to a 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.

As shown in FIG. 1, the pickup apparatus for reproducing the data stored through the recording process according to the related art is generated from the light source 10 through a first optical system providing the first optical path L1. A mirror 20 for reflecting the incident reproduction reference light and entering the recording medium 1 at a predetermined angle; and an actuator for adjusting the incidence angle of the recording reference light 1 of the reproduction reference light by adjusting the arrangement angle of the mirror 20. 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, since the holographic reproducing system uses an angular superposition technique in recording data on the disc as described above, in order to reproduce the angular superimposed recorded data, an angle servo control for adjusting the incident angle when the reproduction reference light is incident on the recording medium. Is required.

However, the holographic reproduction system is currently in the research and development stage. In particular, the angle servo control technology has not been researched in spite of its importance, and the development of the angle servo control device has remained a research subject. .

The present invention is a result of research and development for solving such a problem of the prior art, the angle servo which can adjust the angle of incidence of the reproduction reference light to the recording medium to reproduce the data stored in the recording material layer of the holographic recording medium The object is to provide a control device.

An angle servo control apparatus for a holographic reproducing system according to the present invention for achieving the above object comprises: a first optical system for providing 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 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, and a normal angle of the reproduction reference light incident on the recording medium. First and second angle optical detectors for first and second angle servos, which are arranged to be spaced apart from each other in a positive (+) direction and a negative (-) direction by a center of the reproduction signal light, respectively, and detect the reproduction signal light through the second optical system. Angle servo control is performed by adjusting the angle of incidence of the reproduction reference light incident on the recording medium according to the comparison result of the light detection values by the servo light detection unit. And a control unit for performing.

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.

Before explaining an angle servo control apparatus for a holographic reproduction system according to the present invention, the basic principle 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. 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.

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

The holographic reproducing system to which the angle servo control apparatus of the present invention which follows the angle servo basic principle described with reference to FIGS. 2 to 4 is applied as shown in FIG. 5. FIG. 5 is a configuration diagram of a holographic ROM reproducing system to which an angle servo control device according to the present invention is applied, and in comparison with the holographic ROM reproducing system shown in FIG. 1, the same components have the same reference numerals.

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. An actuator for adjusting the incidence angle of the recording medium 1 of the reproduction reference light by adjusting the placement angle of the mirror 20 according to the mirror 20 to be incident at an angle and the angle servo control signal of the control unit 200 (not shown). A reproducing light detector 30 for detecting a reproducing 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 the recording medium 1 First and second angle optical detectors 110 and 120 for detecting the reproduction signal light incident on the diffraction layer and diffracted in the recording material layer through a second optical system provided by the second optical path L2, and first and second angles; According to the comparison result of the light detection values by the servo light detection units 110 and 120, Is configured to generate a servo control signal and a controller 200 for performing servo control angle for adjusting the reproducing reference beam incident angle is incident on the recording medium 1 through the actuator.

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 reproduction signal lights a 'and 2a' can be detected and detected by the first and second angle servo light detectors 110 and 120.

The first angle servo light detector 110 is spaced apart from the center of the reproduction signal light by the normal angle in a negative (-) direction, and the second angle servo light detector 120 is located at the center of the reproduction signal light by the normal angle. The first and second angle servo light detectors 110 and 120 are disposed to be symmetrical with respect to the light detector 30 at a predetermined distance from the positive (+) direction.

The pickup and angle 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 an actuator (not shown) 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.

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

Here, the light quantity values detected by the first and second angle servo light detectors 110 and 120 are transmitted to the controller 200, respectively, and the controller 200 is the first and second angle servo light detectors 110 and 120. A new angle servo control signal is generated in accordance with the comparison result of the light detection values by H1), and the actuator corrects the incident angle of the reproduction reference light incident on the recording medium 1 in accordance with the angle servo control signal.

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 angle servo light detectors 110 and 120 are detected.

Since the first angle servo light detector 110 and the second angle servo light detector 120 are arranged symmetrically with respect to the light detector 30, the center of the reproduction signal light a 'is the same as that of FIG. 6A. On the contrary, the center of the reproduction signal light 2a 'is closer to the second angle servo light detector 120 when it is far from the one angle servo light detector 110. In this case, the second angle servo light detection unit 120 detects the light detection value of the first angle servo light detection unit 110 by the selectivity curve characteristics of the reproduction signal lights a 'and 2a'. The light detection 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 angle servo light detection unit 110 is greater than the light detection value of the second angle servo light detection unit 120.

6B, the separation distance between the center of the reproduction signal light a 'and the first angle servo light detector 110 is separated from the center of the reproduction signal light 2a' and the second angle servo light detector 120. If the distance is the same, the accurate angle servo is completed and the light detection value by the first angle servo light detector 110 and the second angle servo light detector 120 are the same.

Here, the accurate angle servo is completed, the first and second angle servo light detectors 110 and 120 after the light detection value is set to the same angle or threshold range with each other, the first and second angle servo light detector 110, Even when the light detection difference of 120 is included in the threshold range, it may be determined as a normal angle servo state.

As described above, the light detection values of the first angle servo light detector 110 and the second angle servo light detector 120 are detected by the reproduction light detector 30 at the same position while performing the angle servo control. To play graphic data.

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 present invention performs accurate angle servo control using the characteristic curve characteristic according to the comparison result of the light quantity values detected by the plurality of angle servo light detectors for receiving the reproduction signal light emitted from the holographic recording medium. There is an advantage to this.

Claims (3)

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. First and second angle servo optical detection unit, A control unit for performing angle servo control by adjusting an incident angle of the reproduction reference light incident on the recording medium according to a comparison result of light detection values by the first and second angle servo optical detection units; Angle servo control device for a holographic playback system comprising a. The method of claim 1, And the control unit is configured to complete the angle servo control at positions where the light quantity values detected by the first and second angle servo light detectors are the same. The method of claim 1, And the controller is configured to complete the angle servo control at a position at which a difference between the light quantity values detected by the first and second track light detectors falls within a preset threshold range.

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