KR100546587B1 - Apparatus and method for track servo in optical recording/playback apparatus - Google Patents

Abstract

The present invention relates to a tracking servo device and method in an optical recording / reproducing apparatus having a structure of a land and a valley, in which information is recorded and reproduced on tracks of a mountain and a valley, respectively. Since there is a difference in the amount of light reflected from an untracked track, the presence or absence of a signal recording of an adjacent track is determined by using the difference in the amount of light of the side beams reflected from the outer track and the inner adjacent track of the current track. By correcting the tracking error signal detected from the optical pickup, an offset can be prevented from occurring in the tracking error signal by a signal existing in the adjacent track, so that accurate tracking on can be performed.

Tracking

Description

Apparatus and method for track servo in optical recording / playback apparatus

1 is a block diagram of a general optical recording and reproducing apparatus

2 is a block diagram of a general optical detector by a one-beam method

3A to 3C show the difference between the ideal amount of light and the actual amount of light detected by the photodetector as shown in FIG. 2 when a signal is recorded in only one of the outer and inner adjacent tracks of the track currently being tracked. Shown drawing

Figure 4 is a block diagram showing an example of a three-beam optical detector for tracking servo according to the present invention

5 is a block diagram of a tracking servo device according to the present invention;

FIG. 6 illustrates an example in which a tracking error signal is corrected using a difference in side beams when a signal is recorded in only one of the outer and inner adjacent tracks of a track currently tracked.

Explanation of symbols for main parts of the drawings

501,502: adder 503: gain control unit

504,506 Subtractor 505

507: servo DSP

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording and reproducing apparatus, and more particularly, to a tracking servo apparatus and method in an optical recording and reproducing apparatus having a structure of a hill and a valley to record and reproduce information on tracks of a hill and a valley respectively. will be.

In general, rewritable optical discs have signal tracks in the form of hills and valleys, which enable tracking control even on blank discs in which no information signal has been recorded, and in recent years, the tracks of hills and valleys have been designed to increase the recording density. The information signal is recorded.

To this end, the wavelength of the laser light of the optical pickup for recording / reproducing is shortened, and the numerical aperture of the objective lens for condensing is increased to reduce the size of the light beam for recording and reproducing.

In addition, in order to increase the recording density, the distance between signal tracks, that is, the signal track pitch, is reduced.

In such an optical recording / reproducing apparatus, in order to record information or to reproduce the recorded information, focus control and tracking control of the optical pickup are performed.

1 is a block diagram of a general optical recording and reproducing apparatus for focus control and tracking control. An optical disk 11, an optical pickup 12 for recording and reproducing information on the optical disk 11, and the optical pickup ( A focus error signal detector 13 for detecting a focus error signal FE from an electrical signal outputted from 12), and a tracking error signal detector for detecting a tracking error signal TE from an electrical signal outputted from the optical pickup 12; 14, the focus of the optical pickup 12 is controlled using the focus error signal FE output from the focus error signal detector 13, and the tracking error signal TE output from the tracking error signal detector 14. A high frequency reproduction signal (RF) is detected from a servo digital signal processor (DSP) 15 for controlling tracking of the optical pickup 12 using the optical pickup 12 and an electrical signal output from the optical pickup 12. Signal It consists of a data processing unit (16) for.

The optical pickup 12 in FIG. 1 configured as described above causes the light beam focused on the objective lens to be placed on the signal track of the optical disc 11 under the control of the servo DSP 15, and also returns the light reflected by the signal recording surface. After the light is collected by the objective lens, the light is incident on the photo detector to detect the focus error signal and the tracking signal.

FIG. 2 is an example of the one-beam optical detector, and includes four photodetectors (PDA, PDA, PDC, PDD) that are specifically divided in four directions, i.e., in the signal track direction and the radial direction of the optical disk 11. have.

At this time, the electrical signals A, B, C, and D, which are proportional to the amount of light obtained by each of the photodetectors PDA, PDB, PDC, and PDD, are focused on the focus error signal detector 13 and the tracking error signal detector 14, and It is input to the data processing part 16, respectively.

For example, the focus error signal detection unit 13 performs a focus error signal by (A + C)-(B + D) the electrical signals A, B, C, and D output from the photodetector as shown in FIG. (FE) is detected and output to the servo DSP 15.

The servo DSP 15 moves the optical pickup 12 up and down according to the focus error signal FE so that the optical disk 11 follows the vertical movement along with the rotation. If the focus is not correct, that is, if the light is not focused on the disc's signal plane correctly, the information recorded on the disc may not be read correctly, so the servo DSP 15 may set a distance between the lens and the signal plane of the optical disc 11. Keep it.

For example, the data processor 16 detects a high frequency reproduction signal by (A + B + C + D) the electrical signals A, B, C, and D output from the photodetector as shown in FIG. The high frequency reproduction signal is then subjected to digital signal processing to obtain information recorded on the optical disc 11.

On the other hand, the tracking error signal detection unit 14 tracks the electrical signals A, B, C, and D output from the photodetector as shown in FIG. 2 by (A + D)-(B + C). The error signal TE is detected and output to the servo DSP 15.

The servo DSP 15 moves the main body and the objective lens of the optical pickup 12 in the radial direction in accordance with the tracking error signal TE to correct the position of the beam and track a predetermined track. That is, the track center line of the optical pickup 12 and the disk 11 is controlled to match with the tracking error signal TE. The tracking error signal TE becomes zero at this time, and this state is called tracking on (or on track). Conversely, a state in which the light error is shifted left and right from the track center and the tracking error signal TE has a + or-value is called tracking off (or off track).

In other words, if the tracking is not turned on during recording / reproducing to the disc, the recording or reproducing of the data may not be performed correctly, or the data may be recorded or reproduced in another track, so that the servo DSP 15 may track the tracking to be turned on. The tracking off amount is measured from the error signal TE to perform servo control.

However, as the disc becomes denser, the track pitch between adjacent tracks becomes smaller, and information can be recorded on both hills and valleys. When signals exist in adjacent tracks, there is a possibility that a track off amount occurs even though the track is on. Is higher. In particular, when a signal is recorded in only one of the tracks outside or inside the track adjacent to the current track, the probability of misjudgment is further increased.

That is, since the head of the optical pickup 12 reproduces the signal recorded along the track center line of the optical disk by the servo DSP 15 at the time of disc reproduction, as shown in FIG. Each of the photodetecting elements A, B, C, and D of the photodetector forms an image as shown in FIG. 3B.

At this time, since the amount of beams detected by each of the photodetectors A, B, C, and D, that is, the amount of light is the same, the tracking error signal is 0 (= (A + D)-(B + C)).

However, as shown in FIG. 3A, if a signal is recorded in only one of the outer and inner adjacent tracks of the signal track to be currently tracked, each of the photodetectors A, B, C, and D of the photo detector in the track on state. There is an image as shown in FIG. 3C. That is, a difference occurs in the amount of light detected by each of the photodetecting elements A, B, C, and D depending on the presence or absence of signal recording in adjacent tracks. Here, the part with the pit has a low reflectance, resulting in a dark shadow and a small amount of light detected.

At this time, since the amount of light detected by the photodetectors A and D is less than the amount of light detected by the photodetectors B and C, the tracking error signal has a-value. That is, although tracking is on, an offset occurs in the tracking error signal.

Therefore, the servo DSP 15 moves the objective lens of the optical pickup 12 toward the track where no signal is recorded to correct the position of the beam. This in turn results in an off track where the head of the optical pickup 12 is actually off center of the track, so that correct tracking is not performed.

The present invention is to achieve the above object, an object of the present invention is to determine whether or not the signal recording of the neighboring track using the difference in the amount of light of the side beam and the tracking servo device to correct the tracking error signal using the determination result and In providing a method.

The tracking servo device in the optical recording and reproducing apparatus according to the present invention for achieving the above object comprises: a signal recording detecting unit for determining the presence or absence of a signal in an adjacent track and outputting a tracking error correction signal according to the determination result; A correction unit for correcting a tracking error signal detected from an electrical signal of the optical pickup according to the tracking error correction signal output from the signal recording detection unit, and moving the optical pickup in the radial direction according to the tracking error signal output from the correction unit. It comprises a servo DSP that performs tracking.

The signal recording detector may detect a side beam reflected from an adjacent track and determine whether a signal exists in an adjacent track.

The signal recording detecting unit compares the light amount of the side beam reflected from the outer adjacent track of the currently following track with the light amount of the side beam reflected from the inner adjacent track, and records the signal only in one of the outer and inner adjacent tracks. And a tracking error correction signal is output if it is determined that the signal is recorded in only one track.

The correction unit adjusts the gain of the tracking error signal detected from the optical pickup according to the tracking error correction signal provided by the signal recording detection unit.

The tracking servo method in the optical recording and reproducing apparatus according to the present invention comprises the steps of confirming the presence or absence of a signal in an adjacent track, and correcting the tracking error signal detected from the optical pickup when a signal is present in the adjacent track. Characterized in that made.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

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

The present invention is to determine the presence or absence of signal recording of neighboring tracks by using the difference in the amount of light of the side beams reflected from the outer and inner adjacent tracks of the track currently being tracked, and to adjust the gain of the tracking error signal according to the presence or absence of signal recording.

4 is an example of the optical detector of the present invention for such a tracking servo, an optical detector for detecting the amount of light of the main beam and outputting an electrical signal proportional thereto, and detecting an amount of light of the side beam and outputting an electrical signal proportional thereto The photodetecting device for detecting the amount of light of the main beam comprises four photodetecting devices (PDA, PDB, PDC) that are divided in four directions, i.e., in the signal track direction and the radial direction of the optical disk 11, respectively. PDD), and the photodetectors for detecting the light amount of the side beams are two photodetectors (PDE, PDF) respectively positioned at the top and bottom of the photodetectors (PDA, PDB, PDC, PDD). have.

Fig. 5 is a block diagram showing the configuration of a tracking servo device in the optical recording and reproducing apparatus according to the present invention, wherein the electric signals A and D are output from the optical detection elements PDA, PDB, PDC, PDD of the optical detector of the optical pickup. A first adder 501 for adding the second adder, a second adder 502 for adding the electric signals B and C, and a gain adjusting unit for adjusting gain of the signal output from the first adder 501 according to a control signal 503, a first subtractor 504 for outputting a difference between the electric signals E and F output from the photodetecting elements PDE and PDF, and a signal recording of a neighboring track from the output of the first subtracter 504 After checking whether there is a control unit 505 for outputting a gain control signal to the gain adjusting unit 503, the difference between the output of the gain adjusting unit 503 and the output of the second adder 502 is obtained. Light according to a second subtractor 506 for outputting TE) and a tracking error signal TE output from the second subtractor 506. It consists of a servo DSP 507 which controls the pickup.
In the present invention, for convenience of description, the first subtractor 504 and the control unit 505 are referred to as a signal recording detector, and the first and second adders 501 and 502, the gain adjusting unit 503, and the second subtractor are described. 506 is referred to as a correction unit.

In addition, the gain adjusting unit 503 may be disposed at the output terminal of the second adder 502 instead of the output terminal of the first adder 501 to adjust the gain of the addition result of the second adder 502 or the first. The gains of the addition results of the first and second adders 501 and 502 may be adjusted by disposing at the output terminals of the second adders 501 and 502, respectively. This may vary depending on the designer.

The present invention configured as described above only describes the tracking servo.

That is, during disc reproduction, the first adder 501 adds the electrical signals A and D output from the photodetecting elements PDA, PDB, PDC and PDD of the photodetector for detecting the light amount of the main beam (A + D). The gain adjuster 503 outputs the second adder 502 to the second subtractor 507 by adding the electric signals B and C (B + C).

The first subtractor 504 obtains the difference between the electrical signals E and F output from the photodetecting elements PDE and PDF of the photodetector for detecting the light amount of the side beam, and outputs the difference to the controller 505. The control unit 505 detects the presence or absence of signal recording of a neighboring track from the output signal of the first subtractor 504.

The first subtractor 504 obtains the difference between the two signals by subtracting the electrical signal F output from the photodetecting device PDF from the electrical signal E output from the photodetecting device PDE, and FIG. Assuming that a signal is recorded only in a track following the side beam detected by the photodetecting device PDE among the outer and inner neighboring tracks of the signal track to be currently tracked as shown in FIG. 6, the output of the first subtractor 504 is output. Has a value. This is because the amount of light detected by the photodetecting device on the side where the pits, i.e., the signal is recorded, is smaller than that on the other side, and the output of the photodetecting device outputs an electrical signal proportional to this amount of light.

In addition, when all or none of the signals are recorded in the outer and inner neighboring tracks of the currently following signal track, the first subtractor 504 outputs 0 and is detected by the photodetecting device PDF. When a signal is recorded only in a track followed by the side beam, a + value is output.

Accordingly, the controller 505 can know whether the signal pit is recorded in the outer and inner neighboring tracks of the track currently being tracked from the output of the first subtractor 504.

In particular, if it is determined that the signal is recorded only in one of the outer and inner neighboring tracks according to the presence or absence of signal recording on the adjacent track, the controller 505 sends the gain control signal accordingly to the gain adjusting unit 503. Output

The gain adjusting unit 503 adjusts the gain of the signal output from the first adder 501 according to the gain control signal, and then outputs it to the second subtractor 506, and the second subtractor 506 gains the gain. The corrected tracking error signal (TE = R (A + D)-(B + C)) is detected by subtracting the output of the second adder 502 from the adjusted signal and then outputting to the servo DSP 507. Herein, the gain amount R multiplied by the output of the first adder 501 in the gain adjusting unit 503 is a value at which the output of the second subtractor 506 becomes zero in the tracking on state.

At this time, the gain when the signal is recorded only in the track following the side beam detected by the photodetector PDE and the gain when the signal is recorded only in the track following the side beam detected by the photodetector PDF The magnitude is reversed.

The servo DSP 507 controls the tracking by moving the objective lens in the radial direction by driving the tracking actuator of the optical pickup according to the corrected tracking error signal TE.

Therefore, even when signals are recorded in adjacent tracks, it is possible to prevent the misjudgment that an offset occurs in the tracking error signal.

As described above, according to the tracking servo device and method in the optical recording and reproducing apparatus according to the present invention, since the amount of light reflected from the track on which the signal is recorded and the track not recorded is different, the outer side of the track currently being tracked. The presence or absence of signal recording of adjacent tracks is detected using the difference in the amount of light of the side beams reflected from the inner neighboring tracks, and by correcting the tracking error signal detected from the electrical signal of the photodetector according to the presence or absence of signal recording. By preventing an offset from occurring in the tracking error signal by the signal, accurate tracking on is performed.

Claims (12)

A tracking servo device that detects a tracking error signal in an optical recording / reproducing apparatus that records and reproduces information by using both tracks of peaks and valleys of an optical recording medium, and controls the head of the optical pickup to follow the center of the track. A signal recording detection unit for determining the presence or absence of a signal in an adjacent track of a track currently followed by the head of the optical pickup, and outputting a tracking error correction signal in accordance with the determined presence or absence of a signal in the adjacent track; A correction unit for correcting a tracking error signal detected from an electrical signal of the optical pickup according to a tracking error correction signal output from the signal recording detection unit; And a servo controller which performs tracking according to a tracking error signal output from the correction unit. The method of claim 1, wherein the signal recording detection unit A tracking servo device in an optical recording and reproducing apparatus, characterized by detecting the presence or absence of a signal of an adjacent track by detecting a side beam reflected from an adjacent track of a track currently being tracked. The method of claim 1, wherein the signal recording detection unit Tracking in the optical recording / reproducing apparatus characterized by comparing the amount of light from the side beams reflected from the outer adjacent track of the currently following track with the amount of light from the side beams reflected from the inner adjacent track Servo device. 4. The signal recording detector of claim 3, wherein the signal recording detecting unit From the difference in the amount of light from the side beams reflected from the outer adjacent track of the currently following track and the amount of light from the side beams reflected from the inner adjacent track, it is determined whether the signal is recorded in only one of the outer and inner adjacent tracks. And a tracking error correction signal is output when it is determined that a signal is recorded in only one track. The method of claim 4, wherein When the light detector in the optical pickup which detects the amount of light of the reflected main beam, converts it into an electrical signal, and outputs the light detector is divided into two in the track direction and the radial direction, the correction unit A first adder for adding two electrical signals A and D of the main beam detected in one of the two regions divided in the track direction; A second adder for adding two electrical signals B and C of the main beam detected in the other one of the two regions divided in the track direction; A gain adjusting unit adjusting a gain of the addition result A + D of the first adder according to a tracking error correction signal provided by the signal recording detecting unit; And a subtractor configured to obtain a difference between a signal whose gain is adjusted by the gain adjusting unit and an addition result (B + C) output from the second adder and output a corrected tracking error signal. Tracking servo device. The method of claim 4, wherein When the light detector in the optical pickup which detects the amount of light of the reflected main beam, converts it into an electrical signal, and outputs the light detector is divided into two in the track direction and the radial direction, the correction unit A first adder for adding two electrical signals A and D of the main beam detected in one of the two regions divided in the track direction; A second adder for adding two electrical signals B and C of the main beam detected in the other one of the two regions divided in the track direction; A gain adjusting unit adjusting the gain of the addition result (B + C) of the second adder according to the tracking error correction signal provided by the signal recording detecting unit; And a subtractor for outputting a tracking error signal corrected by obtaining a difference between a signal whose gain is adjusted by the gain adjusting unit and an addition result (A + D) output from the first adder. Tracking servo device. The method of claim 4, wherein When the light detector in the optical pickup which detects the amount of light of the reflected main beam, converts it into an electrical signal, and outputs the light detector is divided into two in the track direction and the radial direction, the correction unit A first adder for adding two electrical signals A and D of the main beam detected in one of the two regions divided in the track direction; A second adder for adding two electrical signals B and C of the main beam detected in the other one of the two regions divided in the track direction; A gain adjusting unit for adjusting gains of the adding result of the first adder and the adding result of the second adder in accordance with a tracking error correction signal provided by the signal recording detecting unit; And a subtractor for outputting a tracking error signal corrected by obtaining a difference between two signals whose gain is adjusted in the gain adjusting unit. A tracking servo method for detecting a tracking error signal and controlling a head of an optical pickup to follow the center of a track in an optical recording / reproducing apparatus that records and reproduces information by using both mountain and valley tracks of an optical recording medium. A signal recording detection step of determining the presence or absence of a signal in the adjacent track of the track currently followed by the head of the optical pickup, and outputting a tracking error correction signal in accordance with the determined presence or absence of the signal in the adjacent track; A tracking error correction step of correcting a tracking error signal detected from an electrical signal of the optical pickup according to a tracking error correction signal output in the signal recording detection step; And a tracking servo step of performing tracking in accordance with the tracking error signal corrected in the tracking error correcting step. The method of claim 8, wherein the signal recording detection step is A tracking servo method in an optical recording and reproducing apparatus, characterized by detecting the presence or absence of a signal of an adjacent track by detecting a side beam reflected from an adjacent track of a track currently being tracked. The method of claim 8, wherein the signal recording detection step is From the difference between the light amount of the side beam reflected from the outer adjacent track of the currently following track and the light amount of the side beam reflected from the inner adjacent track, it is determined whether a signal is recorded in only one of the outer and inner adjacent tracks. And a tracking error correction signal is output when it is determined that a signal is recorded in only one track. The method of claim 1, wherein the signal recording detection unit A subtractor for obtaining a difference between an electrical signal proportional to an amount of light of a side beam reflected from an outer adjacent track of a track currently being tracked and an electrical signal proportional to an amount of light of a side beam reflected from an inner adjacent track; The control unit outputs a tracking error correction signal to the correcting unit by using the output of the subtractor to determine whether a signal is recorded in only one of the outer and inner adjacent tracks and if only one track is recorded. A tracking servo device in an optical recording / reproducing apparatus, characterized by the above-mentioned. A tracking servo device that detects a tracking error signal in an optical recording / reproducing apparatus that records and reproduces information by using both tracks of peaks and valleys of an optical recording medium, and controls the head of the optical pickup to follow the center of the track. When the light detector in the optical pickup which detects the amount of light of the main beam reflected from the optical record carrier, converts it into an electrical signal, and outputs the light is divided into two tracks and two radial directions, A first adder for adding and outputting two electrical signals A and D of the main beam detected in one of two regions divided in the track direction; A second adder for adding and outputting two electrical signals B and C of the main beam detected in the other one of the two regions divided in the track direction; A first subtractor that obtains and outputs a difference between an electrical signal proportional to an amount of light of a side beam reflected from an outer adjacent track of a currently following track and an electrical signal proportional to an amount of light of a side beam reflected from an inner adjacent track; A control unit for determining whether a signal is recorded in only one of the outer and inner adjacent tracks from the output of the first subtractor, and outputting a tracking error correction signal if it is determined that the signal is recorded in only one track; A gain adjusting unit adjusting a gain of one output signal of the output of the first adder and the output signal of the second adder according to the tracking error correction signal output from the controller; A second subtractor for outputting a corrected tracking error signal by obtaining a difference between a gain-adjusted signal and a gain-ungain signal in the gain adjusting unit; And a servo controller which performs tracking in accordance with the corrected tracking error signal output from the second subtractor.

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