KR100555921B1 - Track Servo Control for Holographic Playback System - Google Patents

Abstract

The present invention relates to a track servo control apparatus for a holographic reproducing system, comprising: a holographic recording medium on which a plurality of track patterns having a constant data value are recorded so as to be symmetrical about a data pattern, and a reproduction reference light generated from a light source; A data light detection unit for detecting a reproduction signal light incident on the recording medium and diffracted by a data pattern through a first optical system providing a first optical path incident on the medium at a predetermined angle, and a second optical system providing a second optical path And a first and second track light detectors for detecting a plurality of reproduction signal light incident on the recording medium and diffracted by the track pattern, respectively, through the second optical system, and a light detection value by the first and second track light detectors. And a control unit which performs tracking servo control by adjusting the light detection position of the data light detection unit in comparison with the hologram. When the recording medium is produced, a track pattern having a constant data value is recorded along with the data pattern, and then used as a tracking signal during playback to perform track servo control, so that accurate tracking control can always be performed regardless of the presence or absence of data. There is an advantage to that.

Description

Track servo control device for holographic reproduction system {APPARATUS FOR CONTROLLING TRACK SERVO IN A HOLOGRAPHIC REGENERATION SYSTEM}

1 is a block diagram of a general holographic playback system,

2 is a block diagram of a holographic reproduction system to which a track servo control device according to the prior art is applied;

3 is a block diagram of a holographic reproduction system to which a track servo control device according to the present invention is applied;

4 is a pattern configuration diagram of an optical disk recording medium used in the track servo control apparatus according to the present invention;

5 is a layout view of an optical disc recording medium and a slot and track optical detector according to the present invention;

6A and 6B show light detection states before and after completion of tracking in a track servo control device according to the present invention;

The present invention relates to a track servo control apparatus for a holographic reproducing system, and more particularly to a tracking servo control for reproducing data stored in a recording material layer of a holographic disc.

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

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 with 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 reproducing system requires track servo control in order to accurately reproduce data recorded on a desired track like other optical recording media when the optical disc rotates at a high speed. A track servo control device was proposed in 58675.

2 is a configuration diagram of a holographic reproduction system including a track servo control apparatus disclosed in Patent Application No. 2003-58675.

The holographic reproduction system disclosed in the same reference includes the light source 100, the shutter 102, the first and second half mirrors 104 and 108, the three-segment light detecting means 130, the optical disc 140, and the slit controller 150. And actuator 160. Here, an optical system 106 composed of optical lenses 106b and 106c and an ND filter 106a is formed between the first and second reflecting mirrors 104 and 108, and an optical lens between the optical disk 140 and the light detector. A slit 120 having 110a, 110b and three holes 120a, 120b, 120c through which reproduction signal light is transmitted is configured. In addition, the three-split light detecting means 130 is composed of three light receiving elements (A, B, C) corresponding to the respective holes (120a, 120b, 120c).

The optical disk 140 is a holographic medium in which data recorded in an angular overlapping manner is stored, and is rotated by a motor 145 driven when data is reproduced. A reproduction signal light including a signal of a plurality of tracks is diffracted by the reproduction reference light incident on the optical disk 140 through the first reflector 104 and the second reflector 108, and the interference fringe recorded on the optical disk 140 is incident. Is generated.

The slit 120 has three holes 120a, 120b, and 120c which are moved to the left and right by the actuator 160 and are capable of transmitting the reproduction signal light. In this case, the reproduction signal light that has passed through the holes 120a, 120b, and 120c is transmitted. When present, the reproduction signal light is detected by the light receiving element A, B or C, and the light receiving element A, B or C converts the reproduction signal light into a reproduction signal and provides it to the slit controller 150.

The three-split light detecting means 130 is composed of three light receiving elements A, B, and C installed in correspondence with the holes 120a, 120b, and 120c of the slit 120, respectively. , C receives the reproduction signal light transmitted through the holes 120a, 120b, and 120c to generate a reproduction signal, and the reproduction signal is provided to the slit controller 150. At this time, the reproduction signal light passing through the hole 120b is detected by the light receiving element B, and the reproduction signal light passing through the hole 120c is detected by the light receiving element C, and the reproduction signal light passing through the hole 120a is It is detected by the light receiving element A.

The slit control unit 150 generates a servo control signal for track servo control when the reproduction signal is input from the light receiving element B or C of the three-segment light detecting means 130 to drive the actuator 160 to drive the slit 120. In order to fix the slit 120, the signal is provided to the actuator 160 to fix the slit 120 when the reproduction signal is generated in the light receiving element A of the three-segment photodetector 130. At this time, the reproduction signal generated by the light-receiving element A of the three-segment light detecting means 130 is signal-processed by an unshown signal processor and output.

As such, the track servo control is performed using the holes 120b and 120c among the holes constituting the slit 120, and the data signal is detected using the position hole 120a at the center.

In detail, when the reproduction signal is input from the light receiving element B or C, the slit controller 150 determines that the track servo is not properly performed and provides the servo control signal to the actuator 160 to move the slit 120. In addition, the actuator 160 performs track servo control by moving the slit 120 left and right according to the servo control signal. In addition, when a reproduction signal is input from the light receiving element A, the slit controller 150 provides a signal for fixing the slit 120 to the actuator 160, and the actuator 160 is provided by the slit control unit 150. The slit 120 is fixed based on the signal. At this time, the reproduction signal detected by the light receiving element A is signal-processed and output by a signal processor not shown.

However, as described above, in the holographic track servo control according to the prior art, the track servo control is performed using the reproduction signal light diffracted by the data pattern of the optical disk which is a holographic recording medium, but no data exists in a specific section. If not, tracking control is difficult.

In addition, different amounts of light are detected in the light-receiving elements B and C used for the track servo control among the three-segment light detecting means, and precise tracking control cannot be performed because these are not taken into consideration. There is this.

SUMMARY OF THE INVENTION The present invention has been proposed to solve such a problem of the prior art, in which a track servo control is performed by recording a track pattern having a constant data value together with a data pattern at the time of manufacture of a holographic recording medium and using it as a tracking signal during reproduction. By doing so, the object of the present invention is to always perform accurate tracking control regardless of the presence or absence of data.

A track servo control apparatus for a holographic reproducing system according to the present invention for achieving this object comprises a holographic recording medium on which a plurality of track patterns having a constant data value are recorded so as to be symmetrical about a data pattern and a light source. A first optical system for providing a first optical path for injecting the reproduced reproduction reference light into the recording medium at a predetermined angle, and a second optical system for providing the second optical path for the reproduction signal light incident on the recording medium and diffracted by the data pattern A first and second track light detectors for detecting a data light detector for detecting, a plurality of reproduction signal light incident on the recording medium and diffracted by the track pattern, respectively, through the second optical system, and the first and second track light detectors A control unit which performs tracking servo control by adjusting the light detection position of the data light detection unit by comparing the light detection values with each other. It includes.

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.

3 is a configuration diagram of a holographic reproduction system to which a track servo control device according to the present invention is applied, and in comparison with the holographic reproduction system shown in FIG. 1, the same components have the same reference numerals.

4 is a pattern configuration diagram of an optical disk recording medium 210 fabricated for the track servo control device according to the present invention, in which a normal data pattern 216 is recorded, and a data pattern (around the data pattern 216) is formed. Track patterns 211 and 213 having constant data values are recorded so as to be symmetric about 216.

The holographic reproducing system for reproducing the recording medium 210 of FIG. 4 is a reproduction reference light incident from a light source 10 and incident through a first optical system providing a first optical path L1, as shown in FIG. Mirror 20 to reflect the light incident to the recording medium 210 at a predetermined angle, and an actuator (not shown) to adjust the angle of incidence of the recording medium 210 of the reproduction reference light by adjusting the arrangement angle of the mirror 20. And a data light detector 30 for detecting the reproduction signal light incident on the recording medium 210 and diffracted by the data pattern 216 through a second optical system provided with the second optical path L2, and the recording medium 210. The first and second track light detectors 230 and 240 for detecting the reproduction signal light incident on the light beam and diffracted by the track patterns 211 and 213 through a second optical system provided with the second optical path L2; Light detection position according to the light detection value by the 1, 2 track light detection unit 230, 240 Adjust to be configured to include a controller 250 that performs a tracking servo control.

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 a lens 71 and a slit 220 for injecting light diffracted from the recording medium 210 into the data light detector 30 and the first and second track light detectors 230 and 240. And a condenser lens 75.

As illustrated in FIG. 5, the slit 220 detects by the first and second track light detectors 230 and 240 by passing a plurality of reproduction signal lights by the track patterns 211 and 213 adjacent to the data pattern 216. The first track light detector 230 may be spaced a predetermined distance from the center of the reproduction signal light by the track pattern 213 in a negative (-) direction, and the second track light detector 240 may be The first and second track light centered on the light detector 30 by a predetermined distance away from the center of the reproduction signal light by the track pattern 211 adjacent to the positive (+) direction of the track pattern 213 in the positive (+) direction. The detectors 230 and 240 are arranged to be symmetrical with each other.

The pickup and tracking control process by the holographic reproduction system according to the present invention configured as described above will be described with reference to FIGS. 3 to 6.

First, the light emitted from the light source 10 is reflected by the mirror 20 whose arrangement angle is adjusted by an actuator (not shown), and is reproduced at a predetermined angle (reference light incident angle using oxygen) on the recording medium 210. Reference light is incident.

The reproduction signal light incident on the recording medium 210 is diffracted by the data pattern 216 and the track patterns 211 and 213 of the recording medium 210 so that the reproduction signal light is transmitted through the second optical path L2 to the lens 71. Is incident on.

As a result, the reproduction signal light generated by the data pattern 216 passes through the lens 71, the slit 220, and the lens 75 sequentially and is detected by the data light detector 30, and is detected by the track patterns 211 and 213. The reproduction signal light passes through the lens 71, the slit 220, and the lens 75 sequentially and is detected by the first and second track light detectors 230 and 240.

The light amount values detected by the first and second track light detectors 230 and 240 are transmitted to the controller 250, and the controller 250 is the light detection value by the first and second track light detectors 230 and 240, respectively. The light detection values of the first track light detector 230 and the second track light detector 240 are detected by the data light detector 30 at the same position while performing the tracking servo control by adjusting the light detection positions according to the Output the data.

Referring to the tracking servo control process, since the first track light detector 230 and the second track light detector 240 are symmetrically arranged around the light detector 30, the track pattern 213 is disposed on the track pattern 213 as shown in FIG. 6A. When the center of the reproduction signal light B1 is far from the first track light detector 230, the center of the reproduction signal light B2 by the track pattern 211 is closer to the second track light detector 240. In this case, the light detection value of the second track light detection unit 240 is greater than that of the first track light detection unit 230 due to the selectivity curve characteristics of the reproduction signal lights B1 and B2. Tracking servo control is performed to adjust the data light detection position toward the track pattern 213. On the contrary, if the light detection value by the first track light detection unit 230 is larger than the light detection value by the second track light detection unit 240, the tracking servo control for adjusting the data light detection position toward the track pattern 211 is performed. Perform.

As shown in FIG. 6B, the distance between the center of the reproduction signal light B1 by the track pattern 213 and the first track light detection unit 230 is the center of the reproduction signal light B2 by the track pattern 211 and the second distance. If the distance between the track light detector 240 is equal to the distance from the track light detector 240, accurate tracking is completed and the light detected value by the first track light detector 230 and the light detected value by the second track light detector 240 are the same. The light detector 30 detects data light at the current position.

In this state, the accurate tracking is completed, the light detection values of the first and second track light detectors 230 and 240 are equal to each other, and the light detection values of the first and second track light detectors 230 and 240 are set. Even when the difference is within the threshold range, it may be determined as a normal tracking state.

Although the foregoing description of the present invention has been limited to one embodiment, it is obvious that the techniques of the present invention can be easily modified and implemented 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 correlates with the presence or absence of data by performing track servo control by recording a track pattern having a constant data value together with a data pattern in the production of a holographic recording medium and then using the track signal as a tracking signal during playback. Accurate tracking control can always be performed without

In addition, by performing the track servo control in consideration of the light amount value detected by the track pattern, it is possible to perform more precise tracking control.

Claims (4)

A holographic recording medium on which a plurality of track patterns having a constant data value are recorded so as to be symmetrical about the data pattern; A first optical system providing a first optical path for causing the reproduction reference light generated from the light source to enter the recording medium at a predetermined angle; A data light detector for detecting a reproduction signal light incident on the recording medium and diffracted by the data pattern through a second optical system provided with a second optical path; First and second track light detectors for detecting a plurality of reproduction signal lights incident on the recording medium and diffracted by the plurality of track patterns, respectively, through the second optical system; A control unit which performs tracking servo control by adjusting the light detection position of the data light detection unit by comparing the light detection values of the first and second track light detection units with each other; Track servo control device for a holographic playback system comprising a. The method of claim 1, The first track light detector is spaced apart a predetermined distance from the center of the reproduction signal light by the first track pattern among the plurality of track patterns in a negative (-) direction, and the second track light detector detects the first track pattern. The first and second track light detectors are symmetrically arranged with respect to the data light detector and spaced apart from the center of the reproduction signal light by the second track pattern adjacent to the +) direction in a positive (+) direction. Servo control for holographic playback system. The method according to claim 1 or 2, And the control unit completes the tracking servo control at positions where the light quantity values detected by the first and second track light detectors are equal to each other. The method according to claim 1 or 2, And the controller is configured to complete the tracking servo control at a position where 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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