KR100601286B1 - Reference beam focus servo device of the holographic rom disk - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference light angle servo device of a holographic ROM system, and more particularly, to a first mirror for injecting reference light into an optical disk at a set angle at the time of recording, a first light detector for detecting light reproduced from the optical disk, A second mirror for reflecting the reference light generated in the reflection direction through the disk at an opposite angle incident to the optical disk, a second light detector for detecting the reference light reflected from the optical disk reflected by the second mirror, and a first light And a servo controller for controlling the reference light angle by adjusting the reflection angle of the first mirror by comparing the light detected by the detector and the second light detector with a set value. Therefore, the present invention can detect the reference light reflected from the optical disk to measure whether the reference light angle is correct, and perform servo control of the reference light angle by comparing the reflected light with the reproduced light from the optical disk.

Holographic ROM System, Reference Light Angle, Servo, Light Detector

Description

REFERENCE BEAM FOCUS SERVO DEVICE OF THE HOLOGRAPHIC ROM DISK}

1 is a block diagram showing a playback apparatus of a holographic ROM system according to the prior art;

2 is a block diagram showing a reference light angle servo device of the holographic ROM system according to the present invention;

3 is a view for explaining a recording process for generating reflected light during reproduction of a holographic ROM system according to the present invention;

<Description of the symbols for the main parts of the drawings>

100: light source 104: shutter

106: first mirror 108: optical disk

122: first objective lens 124: first slit

126: first condenser lens 128: first light detector PDIC1

130: second mirror 132: second objective lens

134: second slit 136: second condensing lens

138: second light detector (PDIC2)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo device of a holographic ROM (HROM) system, and more particularly, to detect an angle of reference light incident on a surface of a disc during reproduction of data recorded on an optical disc, which is a holographic recording medium. A reference light angle servo device of a holographic ROM system.

As the information industry develops, a large capacity of a device for storing information and a high speed of processing are required. As a result, the holographic ROM system, which is widely known for recording and reproducing holographic digital data, can store a large amount of information in one bit of an optical disc such as a CD or a DVD, and process the stored data in one bit unit. I / O speed is fast. Because of these advantages, holographic ROM systems are in the spotlight as the next generation of mass information storage.

On the other hand, the reproducing apparatus of the holographic ROM system detects the reference light is irradiated to the optical disk and the light diffracted from the optical disk passes through the pin hole of the slit. At this time, the size of the reference light is much larger than the size of the data track, and since the pinhole size of the slit has a track pitch size, a specific track is caused by run-out in the radial direction or the optical axis direction generated as the optical disk rotates. The light reproduced from the data pit of the slit hardly enters the pinhole of the slit.

Therefore, the servo device of the holographic ROM system detects light passing through the pinhole and adjusts the light to pass correctly into the pinhole according to the detected data. Therefore, the tracking servo in the holographic ROM reproducing device adjusts the position of the radial direction of the light so that the focused light is accurately positioned in the data track. The focus position of the light is adjusted in the direction of the optical axis so that it is exactly positioned at the focus point.

1 is a block diagram showing a playback apparatus of a holographic ROM system according to the prior art.

Referring to FIG. 1, a reproducing apparatus of a holographic ROM system includes a mirror 16 reflecting light generated from a light source 10 and reflecting the light from the optical disk 18 at a predetermined angle, and the reproduced image from the optical disk 18. The light includes a slit 24 for allowing only light having a data diameter of 1 bit to pass through the pinhole, and a photo detector (PDIC: Photo Detect IC) 28 for detecting light passing through the pinhole of the slit 24.

Here, a reducer 12 that deforms light between the light source 10 and the mirror 16 and an aperture that provides the light 16 passing through the reducer 12 to the mirror 16 through an opening ( 14) is included. An objective lens 22 is formed between the optical disk 18 and the slit 24 to form light reproduced from the optical disk 18. The slit 24 and the photodetector (PDIC) 28 are included. ) Includes a condenser lens 26 for condensing the light passing through the pinhole of the slit 24 and transmitting it to the photodetector (PDIC) 28.

In addition, although not shown in the drawings, a conventional holographic ROM system reproducing apparatus includes a servo control unit (uncentered) which performs servo control according to data detected through a photodetector (PDIC) 28, and a servo control unit. Accordingly, an actuator (not shown) for moving the objective lens 22 or the like to perform a focus or tracking servo may be further included.

The reproducing apparatus of the holographic ROM system according to the related art configured as described above operates as follows.

When the laser light of the light source 10 is incident on the mirror 16 through the reducer 12 and the aperture 14, the mirror 16 has the laser light (i.e., phase conjugated wave of the reference light) at the same incidence angle used at the time of recording. ) S1 is reflected on the optical disk 18.

The reference light S1 incident on the optical disk 18 is diffracted and reproduced by the data of the interference fringe recorded on the recording material layer inside the disk, and the reproduced light S2 is imaged by the objective lens 22. At this time, since the diameter of the reference light S1 incident on the optical disk 18 has a size of about 100 μm, the optical image formed through the objective lens 22 is also reproduced by data recorded on many tracks of the optical disk 18. This includes.

The reproduction light S2 formed on the objective lens 22 passes through the pinhole of the slit 24 and is collected by the condenser lens 26 and transmitted to the photodetector PDPD 28. At this time, since the pinhole size of the slit 22 has a size of one bit of data, only one data bit of one track passes through the pinhole among the many track data reproduced, and the reproduced light S2 passes through the condensing lens 26. It is transmitted to the photo detector (PDIC) 28 through.

The photodetector (PDIC) 28 including a two-division photo diode sensor or the like transfers the light quantity data detected in each divided sensor region to the servo controller. The servo controller compares whether or not the light quantity data of the two-segment sensor region transmitted from the photodetector (PDIC) 28 is the same as the set data, and if the two data are the same, does not perform servo control, but the two data are If they are different from each other, servo control is performed by driving an actuator or the like to adjust the position of the objective lens 22.

By the way, in the conventional reproducing apparatus of the holographic ROM system, the desired hologram data cannot be reproduced accurately unless the angle of reference light incident on the disc 18 is set at the same angle as that at the time of recording.

An object of the present invention is to detect the reference light reflected from the optical disk in order to solve the problems of the prior art as described above and to determine whether the reference light angle is correct and compare the reference light reflected by the light reproduced from the optical disk servo of the reference light angle The present invention provides a reference light angle servo device of a holographic ROM system capable of performing control.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a holographic ROM system in which reference light is incident to generate regenerated light of holographic data from an optical disk, comprising: a first mirror for incident a reference light into an optical disk at a predetermined angle when recording; A first light detector for detecting light reproduced from the optical disc, a second mirror for reflecting the reference light generated in the reflection direction through the optical disc at an opposite angle incident to the optical disc, and a reflection from the optical disc reflected by the second mirror. And a servo control unit for controlling the reference light angle by adjusting the reflection angle of the first mirror by comparing the light detected by the first light detection unit and the second light detection unit with a set value. .

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram illustrating a reference light angle servo device of the holographic ROM system according to the present invention. The reference light angle servo device of the holographic ROM system according to the present invention includes a light source 100, a first mirror 106, and an optical disk. 108, a first slit 124, a first light detector (PDIC1) 128, a second mirror 130, a second slit 132, and a second light detector (PDIC2) 138. At this time, reference numeral 120 denotes a spindle motor for rotating the optical disk 108 at a constant speed.

Here, the reducer 102 that deforms the light between the light source 100 and the first mirror 106 and the aperture 104 that provides the light passing through the reducer 102 to the first mirror 106 through the opening. ) Is provided. Here, the first mirror 106 reflects the reference light S1, which is the laser light generated by the light source 100 by the reflection mirror surface inclined at the set angle at the time of recording, to be incident on the optical disk 108.

A first objective lens 122 is formed between the optical disk 108 and the first slit 124 to form light reproduced from the optical disk 108. The first slit 124 and the first light detection unit ( A first condenser lens 126 is provided between the PDIC1 and 128 to collect and pass the light passing through the pinhole of the first slit 124 to the first light detector PDIC1 128.

Here, the optical disk 108 allows the reference light and the signal light as well as the reference light and the reflected light reflected from the data mask to be recorded in recording, so that the reproduction signal light and another reproduction light when the predetermined reference road S1 is incident on the road. (Light generated at the same angle as the incident angle) is generated. The first slit 124 passes only the light having a diameter of 1 bit of data from the light S2 reproduced from the optical disk 108 through the pinhole and transmits the light to the first condensing lens 126. The first light detector PDIC1 128 detects an amount of light of the 1-bit reproduction light S2 collected through the first condenser lens 126 and transmits the light amount to the servo controller (not shown).

In addition, between the optical disk 108 and the second slit 134, the light S3, which is reproduced in another direction from the optical disk 108, is reflected at the same angle as the angle set at the time of recording to the second objective lens 132. The second mirror 130 to be transmitted and the second objective lens 132 to form the reference light S3 transmitted from the second mirror 130 are provided. Between the second slit 134 and the second light detector (PDIC2) 138, a second light for collecting the light passing through the pinhole of the second slit 134 to the second light detector (PDIC2) (138) A condenser lens 136 is provided.

Here, the second mirror 130 reflects the light S3 reproduced in the reflection direction from the optical disk 108 by the reflection mirror surface inclined at the angle set at the recording time, at the same angle as the angle set at the recording time. Incident on the objective lens 132. The second slit 134 passes only the light having a data diameter of 1 bit among the light S3 reproduced in the reflection direction from the optical disk 108 through the pinhole and transmits the light to the second condensing lens 136. The second light detector PDIC2 138 detects an amount of light of the 1-bit reference light S3 collected through the second condenser lens 136 and transmits the light amount to the servo controller (not shown). At this time, the light S3 reproduced in the reflection direction from the optical disk 108 detected by the second light detector PDIC2 138 has an inverse phase opposite to the reference light S1 incident on the disk.

The servo controller compares the light quantity data detected by the first and second light detectors PDIC1 and PDIC2 128 and 138 with the set values, respectively, to perform servo control and tracking servo control of the reference light angle.

The reference light angle servo device of the holographic ROM system according to the present invention configured as described above operates as follows.

The reference light S1, which is a laser light generated by the light source 100, is transmitted to the first mirror 106 through the reducer 102 and the aperture 104. The first mirror 106 reflects the reference light S1 at the set angle and enters the optical disk 108 by the reflective mirror surface inclined at the set angle at the time of recording.

As shown in FIG. 3, in the optical disk 108, the signal light S and the reference light R transmitted through the pattern 202 of the data mask 200 form an interference pattern with each other when the pattern is recorded. The light R 'on which the reference light R is reflected by 202 and the reference light or signal light S interfere with each other and are recorded. When the reference light R is incident on the optical disk 108, the reproduction light appears in the extension line of the signal light and the extension line of the reflected light, respectively. At this time, since the reflected light appears only in a pattern that is a dark portion of the data mask, the two lower reproduction lights have a reversed shape.

The first reproduction light S2 diffracted and reproduced by the reference light S1 incident on the optical disk 108 is formed through the first objective lens 122, passes through the pinhole of the first slit 124, The light is collected through the first condenser lens 126 and transmitted to the first light detector PDIC1 128.

The reference light S1 incident on the optical disk 108 is reflected at the same angle as the incident angle through the recording of the reflected light R 'of the disk.

 Another second reproduction light S3 reproduced from the optical disc 108 is reflected back to the same angle set by the second mirror 130 at the time of recording and transmitted to the second objective lens 132 vertically. The reference light S3 formed in the second objective lens 132 passes through the pinhole of the second slit 134 and is collected through the second condenser lens 136 and transmitted to the second light detector PDIC2 138. do.

The first light detector PDIC1 128 detects an amount of light of the 1-bit first regenerated light S2 collected through the first condenser lens 126, and transmits the light to the servo controller, which is not shown. The detector PDIC2 138 also detects an amount of light of the 1-bit second reproduction light S3 focused through the second condensing lens 136 and transmits the amount of light to the servo controller (not shown). At this time, the light S3 reproduced in the reflection direction from the optical disk 108 detected by the second light detector PDIC2 138 has an inverse phase opposite to the reference light S1 incident on the disk.

By using angular selectivity, when the reference light angles are shifted, the intensity of the two reproduction lights decreases, and thus the point where the sum of the two reproduction lights becomes the maximum is the correct reference light incident angle. By using this, the servo controller for controlling the reference light angle may determine whether the sum (for example, A + B) of the light quantity data detected by the first and second light detectors PDIC1 and PDIC2 128 and 138 becomes the maximum value, respectively. In comparison, if the sum of the detected light amount data (for example, A + B) is equal to the maximum value, it is determined that the reference light angle is exactly the same as the recording time, and thus the reference light servo control is not performed. If the sum of the detected light quantity data (for example, A + B) is not the same as the set value, the servo controller may determine the amount of light quantity data detected by the first and second light detectors PDIC1 and PDIC2 128 and 138, respectively. The reference light angle is adjusted by moving the reflection angle of the first mirror 106 until the sum (for example, A + B) becomes a set value.

In addition, since the two reproduction lights have a reversed phase, it can be seen that the difference between the intensities of the two reproduction lights is on the correct track. If off the track, light from adjacent tracks is detected in the light detector, which serves to reduce the two differences. That is, when the tracks match, one light detector detects '1' and the other light detector detects '0'. Using this, the servo control unit is configured to set the maximum value A and B opposite to each other, for example, | AB |, to which the difference in the amount of light data detected by the first and second light detectors PDIC1 and PDIC2 128 and 138, respectively, is set. If the difference of the detected light quantity data (for example, | AB |) is equal to the set maximum value, it is determined that the tracking servo of the holographic ROM system is matched. Do not. However, if the difference between the detected light amount data (for example, | AB |) is not equal to the set value, the servo controller detects the light amount data detected by the first and second light detectors PDIC1 and PDIC2 128 and 138, respectively. Tracking servo control is performed by adjusting the position of the first objective lens 122 by driving the actuator until the difference (| AB |) becomes the set maximum value.

In addition, the reference light angle servo device of the holographic ROM system according to the present invention is a device of the first objective lens 122 to the first light detector PDIC1 128 for detecting the light S2 reproduced from the optical disk 108. Is detected, the amount of light of the reference light S3 detected through the second objective lens 132 to the second light detection unit PDIC2 138 which detects the light S3 reproduced in the reflection direction from the optical disk 108. The servo control of the reference light angle may be performed by comparing with the set value.

As described above, the present invention can detect the reference light reflected from the optical disk to measure whether the reference light angle is correct, and can perform servo control of the reference light angle by comparing two reproduction lights reproduced from the optical disk.

In addition, the present invention can perform tracking servo control using two reproduction lights reproduced from the optical disc.

On the other hand, the present invention is not limited to the above-described embodiment, various modifications are possible by those skilled in the art within the spirit and scope of the present invention described in the claims to be described later.

Claims (4)

A holographic ROM system which generates a reproduction light of hologram data from an optical disc by injecting reference light, A first mirror for injecting the reference light into the optical disk at a predetermined angle during recording; A first light detector for detecting light reproduced from the optical disc; A second mirror for reflecting the reference light generated in the reflection direction through the optical disk at an opposite angle incident to the optical disk; A second light detector for detecting light reproduced in the reflection direction from the optical disk reflected by the second mirror; A servo controller which controls the reference light angle by adjusting the reflection angle of the first mirror by comparing the light detected by the first light detector and the second light detector with a set value Reference light angle servo device of the holographic ROM system comprising a. The method of claim 1, A first slit for passing a portion of the reproduced light between the first light detector and the optical disk, and a second slit for passing a portion of the reflected reference light between the second light detector and the second mirror Reference light angle servo device of the holographic ROM system further comprising. The method of claim 1, The servo control unit may control the reference light angle by adjusting the reflection angle of the first mirror until the sum of the amounts of light detected by the first light detector and the second light detector is equal to a set value. Reference light angle servo unit in holographic ROM system. The method of claim 1, And the servo controller performs tracking servo control until the difference between the amounts of light detected by the first light detector and the second light detector is equal to a set value.

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