KR100588957B1 - Method and apparatus for compensating tracking error in holographic digital data storage system - Google Patents

Abstract

The present invention relates to the difference in distance between pinholes using the error clock pulse and the cumulative number of times calculated through the difference in distance between the pinholes for linear servo driving, linear velocity, and clock pulse period among the three pinholes of the slit. To compensate for the tracking error caused by the operation, the action for this is a first step of setting the cumulative number of times, a second step of reflecting the laser light emitted from the light source to the reproduction signal light for tracking servo control, tracking servo A third process of injecting each reproduction signal light for control into the photodetector through the left pinhole F and the right pinhole E of the slit, and a fourth process of calculating an error clock pulse between the left pinhole and the right pinhole of the slit Of the sum of the cumulative number of times and the error clock pulses, the light amount of the right pinhole is accumulated up to the cumulative number of times and the error clock pulse is skipped. Only the fifth process of the cumulative amount of light of the left pin hole, using the difference of the right and left pin holes accumulated light amount pin cumulative amount of light holes and a sixth process of controlling the tracking. Therefore, the count of the cumulative number of times and the error clock pulse, that is, the light amount of the right pinhole E and the light amount of the left pinhole F up to 16 counts is tracked as the light quantity is equal by the above-described calculation process. Even when the inner track is rotated at high speed or the cumulative recovery area is increased, the cumulative light amount of the right pinhole E and the cumulative light amount of the left pinhole F are the same, so that the tracking servo can be accurately driven. .

Description

Tracking error compensation method of holographic digital data storage system and its device {METHOD AND APPARATUS FOR COMPENSATING TRACKING ERROR IN HOLOGRAPHIC DIGITAL DATA STORAGE SYSTEM}

1 is a block diagram showing a servo device of a holographic ROM player according to the prior art;

FIG. 2 is a diagram illustrating reproduction signal light transmitted through three pinholes in the slit shown in FIG. 1;

FIG. 3 is a diagram illustrating reproduction signal light transmitted through three pinholes while the track in the optical disc shown in FIG. 1 is moved;

4 is a configuration diagram for a tracking error compensation device of a holographic digital data storage system according to the present invention;

5 is a detailed flowchart for a tracking error compensation method of a holographic digital data storage system according to the present invention;

FIG. 6 is a diagram illustrating a sampling clock between reproduction signal light transmitted through a pinhole for tracking servo among three pinholes while the track in the optical disc shown in FIG. 4 is moved.

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

200: light source 202: reducer

204: aperture 206: reflection mirror

208, 212 Optical lens 210 Slit

214: PDIC 216: servo control unit

1: optical disc

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking error compensating method and apparatus therefor in a holographic digital data storage system (HDDS). Particularly, in a holographic ROM, three pinholes of a slit are pinned. The present invention relates to a method and an apparatus capable of compensating for a tracking error caused by a distance between holes.

In general, as the information industry develops, a larger capacity of a device for storing information and a higher processing speed are required. As a result, the holographic ROM, which is widely used 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. fast. Because of these advantages, holographic ROMs are in the spotlight as the next generation of mass information storage.

On the other hand, the servo operation in the holographic ROM player is different from an optical disc reproducing apparatus such as a general CD or DVD. In other words, the optical disk reproducing apparatus focuses the light to have a track size and detects the light reflected from the data pit. Therefore, the tracking servo adjusts the position of the light in the radial direction so that the focused light is accurately positioned in the data track, and the focus servo is the focus position of the light so that the reflective surface of the disk is exactly at the focus of the light. To adjust in the optical axis direction.

However, in the holographic ROM player, the reference light is irradiated to the optical disk, and since the reference light is much larger than the data track size, it is not necessary to accurately position the light in the radial direction. In other words, even if a run-out in the radial direction occurs to some extent during the rotation of the optical disc, the track to be reproduced is in the reference light so that a tracking servo such as an optical disc reproducing apparatus is not necessary. In addition, a large diameter light has a large depth of focus (for example, a light having a diameter of 100 μm has a depth of focus of about 4.7 mm). Since it is located within the depth of focus range of the reference light, a focusing servo such as an optical disk reproducing apparatus is not necessary.

Therefore, tracking and focusing servo operation in the holographic ROM player allows the light emitted from the data pit of the optical disc to pass through the pinhole of the slit, unlike the optical disc reproducing apparatus. Since the pinhole size has a track pitch size, the light reproduced from the data pit of a specific track is precisely drawn into the pinhole of the slit by run-out in the radial direction or the optical axis direction generated as the optical disk rotates. It's hard to come. Therefore, it is the servo operation in the holographic ROM regenerator that detects light passing through the pinhole and adjusts the light to pass correctly into the pinhole according to the detected data.

1 is a block diagram showing a servo device of a holographic ROM player according to the prior art, in which the conventional servo device reflects light generated from the light source 10 and enters the optical disk 1 at a predetermined angle. ), A slit 70 for allowing only light having a data diameter of 1 bit to pass through the pinhole in the light reproduced from the optical disk 1, and a light detector for detecting light incident through the pinhole of the slit 70. : Photo Detect IC) 90, and a servo controller 100 that performs servo according to data detected through the PDIC 90.

Here, a reducer 20 deforming light between the light source 10 and the reflecting mirror 40 and an aperture that irradiates the reflecting mirror 40 with light passing through the reducer 20 through an opening. 30 is included. An objective lens 60 is formed between the optical disk 1 and the slit 70, and an slit 70 is formed between the slit 70 and the PDIC 90. A condenser lens 80 for condensing light passing through the pinhole is included.

The servo device of the conventional holographic ROM player configured as described above operates as follows. When the laser light of the light source 10 is incident on the reflecting mirror 40 through the reducer 20 and the aperture 30, the reflecting mirror 40 has the laser light (i.e., phase of the reference light) at the same incidence angle used at the time of recording. Conjugated wave) is reflected on the optical disk 1.

Light incident on the optical disc 1 is reproduced by diffraction in the recording material layer inside the disc, and the reproduced light is imaged by the objective lens 60. At this time, since the diameter of the light incident on the optical disk 1 has a size of about 100 μm, the light formed through the objective lens 60 includes many track data of the optical disk 1. The regenerated light passes through the pinhole of the slit 70 and is collected by the condenser lens 80 and transmitted to the PDIC 90. At this time, since the pinhole size of the slit 70 has a data size of 1 bit, only data bits of one track among the many track data reproduced are passed through the pinhole and focused on the PDIC 90 through the condenser lens 80.

The PDIC 90, which is composed of a two-part photo diode, transmits light quantity data detected in each divided sensor region to the servo control unit 100, and the servo control unit 100 transmits two data transmitted from the PDIC 90. Servo control for adjusting the position and the like of the objective lens 60 is performed by comparing whether or not the light amount data of the split sensor region is equal to the set data.

However, in the above-described holographic ROM player, the servo controller 100 determines whether the reproduced light passes through the pinhole center of the slit 70 based on the measured light quantity data of the PDIC 90. There was a problem that it is difficult to accurately measure whether passed through. As a result, in the holographic ROM player, servo control for passing the light reproduced from the optical disk through the center of the pinhole of the slit could not be accurately performed.

In order to solve this problem, as shown in FIG. 2A, three pinholes of the slit 70 are blocked to prevent all light, and only the light from the three pinholes is obtained through the PDIC 90. It can be improved somewhat. Here, the signal obtained from the RF is converted into actual data through signal processing, and the tracking servo is driven using the signals obtained from E and F.

In other words, when tracking is normally performed, the amounts of light of E and F are similar to each other, whereas when tracking errors occur, the values of E and F change as shown in FIGS. 2B and 2C.

On the other hand, as shown in Fig. 3A, the values of E and F are greatly influenced by the on and off states of many tracks in the optical disc 1. That is, although tracking is normally performed, when the value of E is greater than F and E and F are obtained in real time to drive the tracking servo, data cannot be reproduced correctly, and E accumulated in a proper section. The tracking servo is driven using the average value of and F values.

However, as shown in FIG. 3B, when the track in the optical disc 1 moves, as shown in FIG. 3C, when the tracking servo is driven by simply accumulating E and F, different regions accumulate. As the difference between the E and F values also occurs, if the track in the optical disc 1 is rotated at high speed or the cumulative area is increased, the overlapping area of the E and F becomes larger and the tracking servo cannot be driven accurately. I have a problem.

Accordingly, the present invention has been made to solve the above problems, the object of the present invention is a holographic ROM (ROM), the distance between the pinhole for tracking servo drive of the three pinholes of the slit (slit) (slit) Tracking error compensation method of holographic digital data storage system (HDDS) that can compensate tracking error caused by distance difference between pinhole using error clock pulse and cumulative count calculated through difference, linear velocity, clock pulse period And providing the apparatus.

Tracking error compensation method of a holographic digital data storage system (HDDS) according to an aspect of the present invention for achieving the above object is a first step of setting the cumulative number of times, and tracking servo control of the laser light emitted from the light source A second process of reflecting the reproducing signal light for the second process; and a third process of injecting each reproducing signal light for the tracking servo control to the photo detector through the left pinhole F and the right pinhole E of the slit; The fourth process of calculating the error clock pulse between the pinhole and the right pinhole, and accumulates the amount of light in the right pinhole up to the cumulative number of times, and skips the error clock pulse and skips only the error clock pulse. The fifth process of accumulating the amount of light in the left pinhole up to the cumulative number of times, and tracking by using the difference between the amount of light in the right pinhole and the amount of light in the left pinhole is controlled. It characterized in that it includes a sixth step.

In addition, a tracking error compensator of a holographic digital data storage system (HDDS) according to another aspect of the present invention for achieving the above object is a servo control for tracking the laser light emitted from the light source and the laser light emitted from the light source A reflection mirror reflecting the reproducing signal light for the control, a slit for transmitting each reproducing signal light for the tracking servo control through the left pinhole F and the right pinhole E, and an error between the left pinhole and the right pinhole transmitted through the slit Calculate the clock pulse, and accumulate the amount of light in the right pinhole up to the cumulative number of times, and skip the error clock pulse, skip the error clock pulse only, and accumulate only the cumulative number of left pins. Tracking is performed using a photodetector that accumulates the amount of light in the hole, and a difference between the accumulated amount of light in the right pinhole and the amount of light accumulated in the left pinhole. It characterized in that it comprises a servo control unit for controlling.

Hereinafter, a plurality of embodiments of the present invention may exist, and a preferred embodiment will be described in detail with reference to the accompanying drawings. Those skilled in the art will appreciate the objects, features and advantages of the present invention through this embodiment.

4 is a block diagram of a tracking error compensation apparatus of a holographic digital data storage system (HDDS) according to the present invention. Referring to FIG. 4, the light source 200, a reflection mirror 206 that reflects light generated from the light source 200, and enters the optical disk 1 at a predetermined angle, and the light reproduced from the optical disk 1. The signal is converted into real data through signal processing using the reproduction signal light transmitted through the central pinhole RF of the slit 210, and transmitted through the left pinhole F and the right pinhole E of the slit 210. The difference between the cumulative light amount of the left pinhole F and the cumulative light amount of the right pinhole E obtained by the PDIC 214 and the cumulative light amount obtained by the PDIC 214 is obtained by using the reproduced signal light to obtain a cumulative value for driving the tracking servo, respectively. Servo control unit 216 for tracking control.

Here, the light source 200 and the reflection mirror 206 includes a reducer 202 for deforming the light, and an aperture 204 for irradiating the reflection mirror 206 with the light passing through the reducer 202 through the opening. An optical lens 208 is included between the optical disk 1 and the slit 210 to transmit light regenerated by the optical disk, and a central pinhole of the slit 210 between the slit 210 and the PDIC 214. The optical lens 212 transmits the reproduction signal light transmitted through the RF and the reproduction signal light transmitted through the left pinhole F and the right pinhole E of the slit 210.

Based on the above configuration, a method for compensating for a tracking error of a holographic digital data storage system (HDDS) will be described.

That is, when the laser light of the light source 200 is incident on the reflecting mirror 206 through the reducer 202 and the aperture 204, the reflecting mirror 206 reproduces the laser light at the same incidence angle used during recording. Reflected to the optical disk 1 with the reproduction signal light for the. At this time, the reproduction signal light for tracking servo control is reflected on the optical disk 1, respectively.

The reproduction signal light for reproducing data incident on the optical disc 1 passes through the optical lens 208 while diffracted in the recording material layer inside the disc, through the central pinhole RF of the slit 210, and the optical lens 212. Is incident on the PDIC 214.

Each of the reproducing signal light for the tracking servo incident on the optical disk 1 is diffracted by the disk to pass through the optical lens 208 and passes through the left pinhole F and the right pinhole E of the slit 210. And enters the PDIC 214 via the optical lens 212.

The PDIC 214 uses the linear velocity, the distance between the left pinhole F and the right pinhole E of the slit 210, and the period of the clock pulse, so that the left pinhole F and the right pinhole ( Compute the error clock pulse between E).

Subsequently, the PDIC 214 accumulates the light amount of the right pinhole E by the number of cumulative counts and error clock pulses, while increasing the count from " 0 " by 1, and the light accumulation method of the right pinhole E first starts. Accumulate up to the cumulative number of times and then skip up to the error clock pulse. At the same time, the light amount of the left pinhole F is accumulated, and the light amount accumulation method of the left pinhole F is first skipped only to an error clock pulse, and then accumulated only up to the cumulative number of times.

Thereafter, the PDIC 214 provides the servo controller 216 with the cumulative light amount of the right pinhole E and the cumulative light amount of the left pinhole F as many as the cumulative number of times and the error clock pulses.

Then, the servo controller 216 controls tracking by using the difference between the cumulative light amount of the right pinhole E and the cumulative light amount of the left pinhole F provided from the PDIC 214.

Referring to the flowchart of FIG. 5, a method for compensating tracking error of the holographic digital data storage system (HDDS) according to the present invention will be described in more detail based on the above-described configuration and compensation method description.

First, the optical disc 1 is a holographic medium in which data recorded in an angular overlapping manner is stored, and a linear velocity (e.g., 1 mu m / s) determined as a variable element by a motor (not shown) driven at the time of data reproduction. It is rotated constantly and is set to a distance (for example, 3㎛) between the left pinhole (F) and the right pinhole (E) of the slit 210, the clock pulse period (for example, 0.5㎳) It is already set. In addition, it is assumed that the cumulative number of times (eg, 10 times) is set in advance.

The light source 200 emits laser light to the reducer 202 (step 501). The reducer 202 then enters the laser light emitted by the light source into the reflective mirror 206 through the aperture 204 (step 502).

The reflection mirror 204 reflects (step 503) the laser light, i.e., the phase conjugate wave of the reference light, to the optical disk 1 as a reproduction signal light for data reproduction at the same incidence angle used during recording, and performs tracking servo control. The reproduction signal light for the data is reflected on the optical disk 1 with the reproduction signal light for data reproduction at the center and at regular intervals on both sides (steps 504 and 504-1).

The reproduction signal light for reproducing data incident on the optical disc 1 passes through the optical lens 208 while diffracted in the recording material layer inside the disc, through the central pinhole RF of the slit 210 (step 505). Incident on the PDIC 214 via the optical lens 212.

Each reproduction signal light for the tracking servo incident on the optical disk 1 is diffracted by the disk to pass through the optical lens 208, and the left pinhole F (step 506) and the right pinhole of the slit 210 are transmitted. (E) (step 507) and enters the PDIC 214 via the optical lens 212.

The PDIC 214 has a linear velocity (e.g., 1 mu m / m), a distance (e.g., 3 mu m) between the left pinhole F and the right pinhole E of the slit 210, and a period of the clock pulse (e.g., 0.5 ms) to calculate an error clock pulse between the left pinhole F and the right pinhole E of the slit 210 (step 508).

That is, when the error clock pulse is calculated with reference to FIG. 6, when the linear velocity is 1 μm / s, the distance between the left pinhole F and the right pinhole E is 3 μm, so the left pinhole F and the right pinhole are The time between (E) is 3 ms and one cycle of the clock pulse at that time is 0.5 ms, so the total error clock pulse is 6 pulses.

Then, count i starts from 0 (step 509). In symbol, i = 0.

As described above, since the cumulative number of times is ten, it is determined whether the cumulative number (number 10) is smaller than the count i started (step 510).

As a result of the determination 510, when the cumulative number of times (number 10) is not smaller than the count (i = 0), the light amount of the right pinhole E is accumulated (step 511), and the count is increased by one (i = i + 1). (Step 512). As a result of the determination 510, if the cumulative number of times is smaller than the count i, the count is increased by one without accumulating the light amount of the right pinhole E (step 512).

At the same time, since the error clock pulse is 6 pulses, it is determined whether the error clock pulse (number 6) is larger than the count (i = 0) at which it started (step 513).

As a result of the determination 513, when the error clock pulse (number 6) is not greater than the count (i = 0), the light amount of the left pinhole F is accumulated (step 514), and the count is increased by one (step 512). . As a result of the determination 513, when the error clock pulse is larger than the count i, the count is increased by one without accumulating the light amount of the left pinhole F (step 512).

In other words, if the cumulative number of times and the error clock pulse 6 pulses are combined, i = 15 through the above-described determination process (step 515), the cumulative number of times (10 times) while increasing the count from "0" by 1 Until the light amount of the right pinhole E is accumulated only from counts "0" to "9" (10 times) and the last "10" to "15" is skipped, and at the same time, the amount of light of the left pinhole F After skipping only "0" to "5" which are 6 pulses of the error clock pulse, the light amount of the left pinhole F is accumulated from "6" to "15".

Thereafter, the PDIC 214 calculates the cumulative light amount of the right pinhole E and the cumulative light amount of the left pinhole F as many as the count (10 + 6 pulses = 16 counts) of the cumulative number of times and the error clock pulse. 216) (step 516).

The servo controller 216 controls tracking by using the difference between the accumulated light amount of the right pinhole E and the accumulated light amount of the left pinhole F provided from the PDIC 214 (step 517).

Therefore, the count of the cumulative number of times and the error clock pulse, that is, the light amount of the right pinhole E and the light amount of the left pinhole F up to 16 counts is tracked as the light quantity is equal by the above-described calculation process. (1) Even when the internal track is rotated at high speed or the cumulative recovery area is increased, the cumulative light amount of E and F is the same, so that the tracking servo can be driven accurately.

As described above, according to the present invention, the sum of the cumulative number of times and the error clock pulse, that is, the light amount of the right pinhole E and the light amount of the left pinhole F up to 16 counts becomes the same light amount by the above-described calculation process. Therefore, even when tracking is normally performed and the track in the optical disc is rotated at high speed or the cumulative number of times is increased, the amount of accumulated light in the right pinhole E and the amount of accumulated light in the left pinhole F are the same, so that the tracking servo can be precisely adjusted. There is an effect that can be driven.

And, since the invention is disclosed as a right within the spirit and claims of the present invention, the present invention may include any modification, use, and / or adaptation using general principles, and as a departure from the description herein It includes all matters falling within the scope of known or customary practice in the art and within the scope of the appended claims.

Claims (12)

A tracking error compensation method of a holographic digital data storage system (HDDS), The first step of setting the cumulative number of times, A second process of reflecting the laser light emitted from the light source as the reproduction signal light for tracking servo control; A third process of injecting each reproduction signal light for the tracking servo control to the photo detector through the left pinhole F and the right pinhole E of the slit; A fourth process of calculating an error clock pulse between a left pinhole and a right pinhole of the slit; A fifth process of accumulating the light amount of the right pinhole up to the cumulative number of times and skipping the error clock pulse among the number of cumulative times and the error clock pulses, skipping only the error clock pulse and accumulating the light amount of the left pinhole up to the cumulative number of times; A sixth process of controlling tracking by using a difference between the accumulated light amount of the right pinhole and the accumulated light amount of the left pinhole. Tracking error compensation method of the holographic digital data storage system comprising a. The method of claim 1, The error clock pulse is calculated using the distance between the left and right pinholes of the slit, the linear velocity of the optical disk in the holographic digital data storage system, and the period of the clock pulse in the holographic digital data storage system. Tracking error compensation method of holographic digital data storage system, characterized in that. The method of claim 2, The linear velocity of the optical disk in the holographic digital data storage system is a variable element, the tracking error compensation method of the holographic digital data storage system. The method of claim 2, The distance between the left pinhole and the right pinhole of the slit and the period of the clock pulse in the holographic digital data storage system are fixed elements, the tracking error compensation method of the holographic digital data storage system. The method of claim 1, The slit is composed of three pinholes, the tracking error compensation method of the holographic digital data storage system, characterized in that for transmitting the reproduction signal light for data reproduction through the central pinhole (RF). The method of claim 5, wherein The three pinholes are applied to all optical storage media. The tracking error compensation method of the holographic digital data storage system. Tracking error compensation device of holographic digital data storage system, A light source for emitting laser light, A reflection mirror reflecting the laser light emitted from the light source as a reproduction signal light for tracking servo control; A slit for transmitting the respective reproduction signal light for the tracking servo control through a left pinhole F and a right pinhole E; Compute the error clock pulse between the left pinhole and the right pinhole transmitted through the slit, and accumulates the amount of light in the right pinhole up to the cumulative number of the error clock pulse and the preset cumulative number of times, and calculates the error clock pulse. A photodetector that skips, skips only error clock pulses, and accumulates the amount of light in the left pinhole up to a cumulative number of times; A servo controller for controlling tracking by using a difference between the accumulated light amount of the right pinhole and the accumulated light amount of the left pinhole. Tracking error compensation device of the holographic digital data storage system comprising a. The method of claim 7, wherein The error clock pulse is calculated using the distance between the left and right pinholes of the slit, the linear velocity of the optical disk in the holographic digital data storage system, and the period of the clock pulse in the holographic digital data storage system. Tracking error compensation device of a holographic digital data storage system, characterized in that. The method of claim 8, The linear velocity of the optical disc in the holographic digital data storage system is a variable element, the tracking error compensation device of the holographic digital data storage system. The method of claim 8, The distance between the left pinhole and the right pinhole of the slit and the period of the clock pulse in the holographic digital data storage system are fixed elements, tracking error compensation device of the holographic digital data storage system. The method of claim 7, wherein The slit is composed of three pinholes, tracking error compensation device of the holographic digital data storage system, characterized in that for transmitting the reproduction signal light for data reproduction through the central pinhole (RF). The method of claim 11, The three pinholes, tracking error compensation device of the holographic digital data storage system, characterized in that applied to all the optical storage media.

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