KR20000055150A - Track Servo Control Method in Optical Disc Apparatus and Apparatus Thereof - Google Patents

Abstract

PURPOSE: A method and an apparatus for controlling the track servo of an optical disk apparatus are provided to achieve a stable tracking servo by equalizing tracking servo signals of different sizes detected in a recorded domain and an unrecorded domain. CONSTITUTION: An optical pickup(2) converts lights reflected from a disk into an electrical signals. A pre-amp(4) is connected to the light detector of the optical pickup(2) in serial. An actuator driving driver(12) drives an actuator of the optical pickup(2). A reference contact(62a) of a transfer unit(62) is connected to the actuator driving driver(12). A recorded/unrecorded domain detector(52) and a microcomputer(60) are connected in serial between the high frequency signal output terminal of the pre-amp(4) and the control signal input terminal of the transfer unit(62). A gain adjustment amplifier(54) and a servo filter(56) are connected in serial between the tracking error signal output terminal of the pre-amp(4) and a first selection contact(62b) of the transfer unit(62) and are connected to the microcomputer(60) respectively. A pause signal generator(58) is connected between a second selection contact(62c) of the transfer unit(62) and the microcomputer(60).

Description

Track Servo Control Method in Optical Disc Device and Apparatus {Track Servo Control Method in Optical Disc Apparatus and Apparatus Thereof}

The present invention relates to a servo control method of an optical disc apparatus for recording or reproducing information on an optical disc. More particularly, the present invention relates to a track servo control method and apparatus for equalizing tracking servo signals detected at different sizes in a recording area and an unrecorded area. will be.

In general, optical discs such as CDs and DVDs are irradiated with a laser beam on a recording surface so that information is recorded or reproduced. Such optical discs are classified into play-only and rewritable media. In the former case, there are ROM types such as CD-ROM and DVD-ROM. In the latter case, the write once read many (WORM) type, the rewritable type, and the RAM are based on the number of rewritable times. It is divided into types.

An optical disc apparatus for recording / reproducing an optical disc is provided with a tracking servo control apparatus which performs tracking servo based on a tracking error signal.

Referring to FIG. 1, an optical pickup 2 for photoelectrically converting light reflected from the disk by irradiating light onto the optical disk, an actuator 12 for driving an objective lens, an optical pickup 2 and an actuator 12 A conventional track servo control device is shown having a preamp 4, a gain adjustment amplifier 6, a servo filter 8, and an actuator drive driver 10 connected in series therebetween. The reflected light reflected from the disk is converted into an electrical signal by a two or four split photodetector of the optical pickup 2. The preamplifier 4 detects the tracking error signal TE by differentially amplifying the two-split reflected light signal supplied from the photodetector and adds and amplifies the two-split reflected light signal in the track direction to generate a high frequency signal RF. Will be detected. Since the gain adjusting amplifier 6 has a difference in reflectance according to the type of optical disk, the gain adjusting amplifier 6 amplifies the tracking error signal TE so that the level of the tracking error signal is greater than or equal to a predetermined reference value. For example, since the reflectance of the CD-RW is about 1/5 lower than that of the CD-ROM or the CD-R in the CD optical disc, the tracking error signal TE detected is very low. Accordingly, the gain adjusting amplifier 6 amplifies the tracking error signal TE at a larger amplification rate when the CD-RW is accessed than when the CD-ROM or the CD-R is accessed. In addition, the gain adjusting amplifier 6 adjusts the gain based on either the recording area or the unrecorded area if the optical disc currently accessed is a recordable optical disc, for example, CD-RW or CD-R. The servo filter 8 compensates the low pass gain required in the servo system by compensating the low pass gain and the phase compensation in the high frequency band for the tracking error signal TE amplified by the gain adjustment amplifier 6. The actuator driving driver 10 amplifies the output signal of the servo filter 8 with a driving power suitable for driving the actuator 12.

However, in the conventional tracking servo device, when accessing a recordable optical disc, the gain of the tracking servo loop is referred to as an already recorded area (hereinafter referred to as "recording area") and an unrecorded area (hereinafter referred to as "unrecorded area"). Tracking control becomes unstable because it is fixed based on any one region. This will be described in detail with reference to FIG. 2.

Referring to Fig. 2, in a recordable optical disc, tracks of hills and valleys are arranged in a spiral or concentric shape. Data is recorded in the form of a pit on a track of a valley in an optical disc such as a CD-RW, and in the form of a pit in both mountain and valley tracks in an optical disc such as a DVD-RAM. In the recording area, the reflectance of the light reflected by the light is diffused by the pit is low, and in the unrecorded area, the mirror section without the pit is continuously and almost totally reflected, so that the intensity of the reflected light is high. Therefore, the high frequency signal RF, which is detected as the sum signal of the two split reflection light signals in the track direction photoelectrically converted by the photodetector, is detected only in the recording area and not in the unrecorded area depending on whether pits are present. In addition, the tracking error signal TE is detected at a larger pick-to-pick level in the unrecorded area than when detected in the recording area.

In the conventional track servo controller, tracking in the unrecorded area becomes unstable if the servo loop gain is fixed with respect to the recording area relative to the optical disk currently accessed. In other words, in order to perform tracking servo correspondingly to a defective area, the servo loop gain should be small. If the servo loop gain is fixed based on the recording area, the servo loop gain becomes relatively large in the unrecorded area. When the defect area exists, the tracking servo becomes very unstable. In addition, if the servo loop gain is fixed on the basis of the unrecorded area, the servo loop gain is reduced in the recording area. Therefore, the seek speed for the target track takes longer in the recording area when tracking servo is performed.

On the contrary, in order to perform tracking servo according to the disc eccentricity, the servo loop gain must be large. However, if the servo loop gain is fixed relative to the unrecorded area, the servo loop gain becomes relatively small in the recording area. The tracking servo becomes very unstable with respect to eccentricity when performing servo. In addition, if the servo loop gain is fixed based on the recording area, the search speed for the target track takes a long time when the tracking servo is performed in the unrecorded area.

As described above, when the optical pickup moves across the plurality of recording areas and the unrecorded area from the playback position a to the recording position b and records the information, as shown in FIG. The tracking servo becomes very unstable and time consuming to seek the desired track.

On the other hand, in an optical disc such as a DVD-RAM, a user information area in which user data is recorded in both mountain and valley tracks, and a header area including identification information for the user information area are alternately arranged in the user information area. . In such an optical disc, the phase of the tracking error signal TE should be reversed in the tracks of the hills and valleys, and the tracking servo should be controlled only in the user information area.

3 is a block diagram showing a tracking error signal detection circuit for a DVD-RAM.

In the configuration of FIG. 3, the tracking servo device of the DVD-RAM includes a first amplifier 21 and an adder 25 to which the tracking error signal TE1 is commonly input from the preamplifier 4, and the first amplifier 21. The first switch 22, the first low pass filter & holder 23, the second amplifier 24, and the output terminal of the adder 25 are connected in series between the output terminal of the output terminal and the input terminal of the adder 25. The connected inverter 26 and the buffer 27, the second switch 28 commonly connected to the inverter 26 and the buffer 27, and a second connected to the output terminal of the second switch 28. The low pass filter & holder 29 and the 3rd amplifier 30 connected to the output terminal of the 2nd low pass filter & holder 29 are provided.

In the first switch 22, a mirror window determination signal indicating a mirror window area is input as a control signal. Here, the mirror window area is disposed in the user information area for a predetermined period to detect a DC offset included in the tracking error signal TE1 as the objective lens is deviated from the optical axis. The second switch 28 includes a mountain / goal determination signal having different logical values in the mountain track and the goal track so as to identify the mountain track and the goal track in the user information area, the header area and the user information. A header area determination signal having different logic values in the header area and the user information area is input as a control signal to identify the area.

The tracking error signal TE1 detected from the preamplifier 4 based on the two-split reflected light signal is amplified by the first amplifier 21 by a predetermined gain value and input to the first switch 22. The first switch 22 connects the reference contact 1a to the second selection contact 1c if the area currently accessed according to the logic value of the mirror window determination signal is the mirror window area, and is a user information area or a header area. In this case, the reference contact 1a is connected to the first selection contact 1b. Accordingly, the first switch 22 detects a DC offset included in the tracking error signal TE1 in the mirror window area. This DC offset is integrated by the first low pass filter & holder 23 and amplified by the second amplifier 24 to be level matched with the tracking error signal TE1 detected from the preamplifier 4 and adder 25. ) Is entered. The adder 25 removes the DC offset included in the tracking error signal TE1 by adding the tracking error signal TE1 input from the preamplifier 4 and the DC offset input from the adder 24. The tracking error signal from which the DC offset is removed is input to the inverter 26 and the buffer 27 in common. The second switch 28 selectively selects the reference contact 2a, the first selection contact 2b, the second selection contact 2c, or the third according to the logic value of the mountain / goal track determination signal and the header region determination signal. It is connected to the selection contact 2d. The reference contact 2a of the second switch 28 is the third selection contact 2d to the first selection contact 2b or the first selection contact at the time when the logic value of the mountain / goal track determination signal changes. 2b) is connected to the 3rd selection contact 2d. Further, the reference contact 2a of the second switch 28 is connected to the second selection contact 2c when the area currently accessed by the header area determination signal is determined as the header area. Accordingly, the tracking error signal output from the adder 25 is inverted at a point in time when the area currently accessed is moved from the track of the hill to the track of the goal or from the track of the goal to the track of the mountain, and in the header area the hold ( hold)

On the other hand, the peaking level of the tracking error signal detected from the DVD-RAM also varies depending on the amount of light reflected between the recording area and the unrecorded area as in the CD-R or CD-RW. Referring to FIG. 4, the tracking error signal TE2 output from the third amplifier 30 is held in the header area and its peak level is different depending on whether or not the user information area is recorded. That is, the peak level of the tracking error signal TE2 detected from the recording area in the user information area is larger than that of the tracking error signal TE2 detected from the unrecorded area. Therefore, if the tracking servo loop gain is fixed to either the recording area or the unrecorded area, it becomes boundless. In addition, optical discs such as DVD-RAM have a higher density of disc structures than CD-based optical discs, so that tracks are denser and more precise tracking servos are required.

Accordingly, it is an object of the present invention to provide a track servo control method and apparatus for an optical disc apparatus in which a tracking error signal is made uniform in a recording area and an unrecorded area.

1 is a block diagram schematically showing a conventional track servo controller.

Fig. 2 is a diagram showing tracking error signals detected in a recording area and an unrecorded area in a recordable optical disc.

3 is a block diagram showing a tracking servo device for a DVD-RAM;

4 is a voltage waveform diagram showing a high frequency signal and a tracking error signal detected from a DVD-RAM;

5 is a block diagram showing a track servo control apparatus of the optical disk apparatus according to the embodiment of the present invention.

FIG. 6 is a voltage waveform diagram illustrating a pause signal generated from the pause signal generator shown in FIG. 5 and a tracking error signal detected from the preamplifier during the pause period.

FIG. 7 is a voltage waveform diagram of output signals detected in each unit shown in FIG. 5 in a recording area and an unrecorded area in a recordable optical disc; FIG.

8 is a flowchart illustrating a track servo control method of an optical disk device according to an embodiment of the present invention, in order of control.

<Description of the code | symbol about the principal part of drawing>

2: optical pickup 4: preamplifier

6,54: Gain adjustment amplifier 8,56: Servo filter

10: actuator driving driver 12: actuator

21,30,24: amplifier 22,28,62: switch

23,29: low pass filter & holder 25: adder

26 Inverter 27 Buffer

52: record / unrecorded area determiner 58: pause signal generator

60: micom

In order to achieve the above object, the track servo control method of the optical disk apparatus according to the present invention comprises the steps of determining the recording area and the unrecorded area, and moving the object lens between the recording area and the unrecorded area according to whether or not to record, and then stopping the objective lens. Detecting the magnitude of the tracking error signal, and comparing the tracking error signal detected before the area move with the tracking error signal detected after the area move, and adding or subtracting the magnitude of the tracking error signal detected after the area move.

The track servo control apparatus of the optical disc apparatus according to the present invention comprises area discrimination means for discriminating between a recording area and an unrecorded area, and moving the objective lens temporarily after moving the area between the recorded area and the unrecorded area depending on whether to record or not, and thus the magnitude of the tracking error signal. And an error signal detecting means for detecting a signal, and servo control means for comparing the tracking error signal detected before the area move and the tracking error signal detected after the area move to add or subtract the magnitude of the tracking error signal detected after the area move.

Other objects and features of the present invention in addition to the above object will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 5 to 8.

Fig. 5 is a block diagram showing a track servo control apparatus of the optical disk apparatus according to the first embodiment of the present invention.

In the configuration of Fig. 5, the track servo control apparatus of the optical disk apparatus according to the present invention is provided with an optical pickup 2 for photoelectrically converting light reflected from the disk by irradiating the optical disk with light, and in series with the photodetector of the optical pickup 2; The preamplifier 4 connected to the actuator, the actuator driving driver 12 for driving the actuator of the optical pickup 2, the switch 62 connected to the actuator driving driver 10, and the reference contact 62a; A recording / unrecording area detector 52 and a microcomputer (μ-Com) 60 connected in series between the high frequency signal output terminal of the preamplifier 4 and the control signal input terminal of the switch 62; A gain adjusting amplifier 54 and a servo filter 56 connected in series between the tracking error signal output terminal of the amplifier 4 and the first selection contact 62b of the switch 62 and connected to the microcomputer 60, respectively. And a pause signal generator connected between the second selection contact 62c of the switch 62 and the microcomputer 60 ( 58).

The optical pickup 2 is used as a laser diode used as a light source, an objective lens for condensing a light beam generated from the light source on a disk in the form of a micro spot, and used as a photodetector for photoelectric conversion of light reflected from the disk. Photo diode, an actuator for guiding the optical beam generated from the light source toward the objective lens, and an optical system for guiding the reflected light beam reflected from the disc toward the photodetector toward the photodetector in two directions in the tracking and focusing directions It will include. The preamplifier 4 detects the tracking error signal TE1 by differentially amplifying the two split reflected light signal in the track direction supplied from the photodetector, and adds and amplifies the two split reflected light signal in the track direction to generate a high frequency signal RF. Will be detected. The recorded / unrecorded area detector 52 supplies the microcomputer 60 with a recording area identification signal having a specific logic (for example, high logic) value in the section where the high frequency signal 52 is detected, and the high frequency signal 52. In the section in which is not detected, the uncompressed area identification signal having a logic (for example, low logic) value having a different logic value from the recording area identification signal is supplied to the microcomputer 60. Since the gain adjusting amplifier 54 has a difference in reflectance depending on the type of optical disk, the gain adjusting amplifier 54 amplifies the tracking error signal TE1 so that the level of the tracking error signal TE1 is equal to or greater than a predetermined reference value. In addition, the gain adjusting amplifier 54 adjusts the optimum gain for either the recording area or the unrecorded area if the optical disk that is currently accessed at the initial access is recordable, for example, CD-RW or CD-R. Done. In addition, the gain adjusting amplifier 54 detects the peak level of the tracking error signal TE1, that is, the magnitude thereof, and supplies it to the microcomputer 60 and controls the tracking error signal TE1 with different gain values under the control of the microcomputer 60. ), The tracking error signal TE1 is supplied to the servo filter 56 by adjusting the magnitude of the tracking error signal TE1. The servo filter 56 performs low pass gain compensation and phase compensation in the high frequency band of the correction tracking error signal TE2 from the gain adjusting amplifier 54 under the control of the microcomputer 60, thereby requiring the low pass gain required by the servo system. To compensate. The pause signal generator 56 generates the pause signal PC of one cycle as shown in FIG. 6 under the control of the microcomputer 60 to pause the objective lens on an arbitrary track. The switch 62 connects the reference contact 62a to the first select contact 62b or the second select contact 62c under the control of the microcomputer 60 to switch the current path. The actuator driving driver 10 power amplifies a signal supplied from the reference contact 62a of the switch 62 with a driving power suitable for driving the actuator.

The microcomputer 60 determines whether the area currently accessed by the recording area determination signal or the unrecording area determination signal supplied from the recording / unrecording area detector 52 is the recording area or the unrecorded area.

When the optical pickup 2 moves from the recording area to the unrecorded area by the sled servo system, the microcomputer 60 controls the sled servo system when an unrecorded area determination signal is generated from the record / unrecorded area detector 52. The optical pickup 2 is stopped and the pause signal generator 58 is driven to generate the pause signal PC. At the same time, the microcomputer 60 controls the switch 62 to connect the reference contact 62a to the second selection contact 62c so that the pause signal PC is supplied to the actuator drive driver 10, and the focus is supplied. The servo is turned on and the tracking servo is turned off so that a tracking error signal is detected when the objective lens is paused by driving the actuator.

In contrast, when the optical pickup 2 moves from the unrecorded area to the recording area, if a recording area determination signal is generated from the recording / unrecording area detector 52, the microcomputer 60 controls the sled servo system to control the optical pickup 2 In addition, the pause signal generator 58 is driven to generate the pause signal PC. At the same time, the microcomputer 60 controls the switch 62 to connect the reference contact 62a to the second selection contact 62c so that the pause signal PC is supplied to the actuator drive driver 10, and the focus is supplied. The servo system is turned on and the tracking servo is turned off so that a tracking error signal is detected when the objective lens is paused by driving the actuator.

After the optical pickup 2 moves from the recording area to the unrecorded area, the microcomputer 60 pauses the gain value of the gain adjusting amplifier 54 when the magnitude of the tracking error signal detected by pausing is increased. do. On the contrary, if the tracking error signal detected by pausing after the optical pickup 2 moves from the unrecorded area to the recording area in the reproduction mode, the gain value of the gain adjusting amplifier 54 is increased. Accordingly, the correction tracking error signal TE2 can be detected by the gain adjusting amplifier 54 in a uniform size in the recording area and the unrecorded area as shown in FIG.

8 is a flowchart illustrating a track servo control method of an optical disk apparatus according to an embodiment of the present invention according to a control procedure.

First, in the initial access, the microcomputer 60 adjusts the gain value of the gain adjusting amplifier 54 to adjust the optimum gain for any one of the recording area and the unrecorded area in the disc type or recordable disc. Step S1) and the microcomputer 52, by the recorded / unrecorded area determination signal supplied from the recorded / unrecorded area detector 52 when the disk currently accessed is a recordable disk, for example, CD-R or CD-RW. The area currently accessed is determined. (Step S2) If the area currently accessed is determined to be a recording area by the recording area determination signal, and a recording command is input, the microcomputer 12 controls the recording processing unit (not shown) to record. The recording will be performed in the area. If there is no more space to record in the recording area, the microcomputer drives the sled servo system to move the optical pickup 2 to the unrecorded area (steps S3 and S4). If it is determined that the reproduction command is input, the microcomputer 12 controls the reproduction processing system (not shown) to reproduce the information recorded in the recording area. In step S4, after the optical pickup 2 is moved to the unrecorded area, when the unrecorded area determination signal is generated from the recorded / unrecorded area detector 52, the microcomputer 60 may pause the pause signal generator 58 and the switch 62. Are simultaneously driven to cause the objective lens to be temporarily paused on the track on the unrecorded area by the pause signal PC. (S5) In addition, the microcomputer 60 turns on the focus servo and turns off the tracking servo. In this state, the gain adjusting amplifier 56 detects the magnitude of the tracking error signal TE1. (Step S6) The tracking error signal TE1 detected when the objective lens is paused on the unrecorded area is as described above. The peak level becomes larger than the recording area. The tracking error signal TE1 of which the magnitude is increased in this way is reduced in the gain value of the gain adjusting amplifier 54 by the control of the microcomputer 60, so that the magnitude thereof is equal to the magnitude of the tracking error signal TE1 detected in recording. The microcomputer 60 controls the recording processing system (not shown) to move the optical pickup 2 to the recording position on the unrecorded area, and then records the information. step)

In step S2, when the area currently accessed by the unrecorded area determination signal is determined to be the unrecorded area and a playback command is input, the microcomputer 12 drives the sled servo system to move the optical pickup 2 to the recording area. On the other hand, when the currently accessed area is determined to be an unrecorded area and a recording command is input, the microcomputer 12 drives the sled servo and the tracking servo to move the optical pickup 2 to the recording position, and then records. The processing system (not shown) is controlled to record the information. In step S10, after the optical pickup 2 is moved to the unrecorded area, when the recording area determination signal is generated from the recorded / unrecorded area detector 52, the microcomputer 60 generates the pause signal generator 58 and the switch 62. Are simultaneously driven to cause the objective lens to be temporarily paused on the track on the recording area by the pause signal PC. (S11) In addition, the microcomputer 60 turns on the focus servo and turns off the tracking servo. In this state, the gain adjusting amplifier 56 detects the magnitude of the tracking error signal TE1. (Step S12) The tracking error signal TE1 detected when the objective lens is paused on the recording area is as described above. The peak level becomes smaller than that of the unrecorded area. As described above, the tracking error signal TE1 having the reduced magnitude is increased by the gain value of the gain adjusting amplifier 54 under the control of the microcomputer 60, and the magnitude thereof is equal to the magnitude of the tracking error signal TE1 detected in the unrecorded area. The same level is corrected (step S13). The microcomputer 60 controls a playback processing system (not shown) to reproduce the information recorded on the recording area. (Step S8)

On the other hand, in the embodiment, by adjusting the gain of the gain adjusting amplifier 54, the size of the tracking error signal TE1 whose magnitude increases or decreases according to the recording area and the unrecorded area is corrected. However, as shown in FIG. Since each of the amplifier 4, the servo filter 56, and the actuator driver 10 has a gain value, the gain value of the preamplifier 4, the servo filter 56, or the actuator driver 10 is adjusted for tracking. The magnitude of the error signal TE1 may be corrected.

On the other hand, in the tracking servo method for the optical disc such as the DVD-RAM, the recording area and the unrecorded area are discriminated in the user information area and the objective lens is paused in the record area and the unrecorded area as in the above-described embodiment of the present invention. During the pause, the amplitude of the tracking error signal is detected and the gain of the preamplifier 4 or the third amplifier 30 is adjusted in FIG. 3 to control the tracking error signal to have the same magnitude in the recording area and the unrecorded area. Tracking servo can be implemented.

As described above, the track servo control method and apparatus of the optical disk apparatus according to the present invention can realize stable tracking servo by making the signal level of the tracking error signal detected in the recording area and the unrecorded area the same.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (9)

Determining a recording area and an unrecorded area; Detecting the magnitude of the tracking error signal by temporarily stopping the objective lens after moving the area between the recording area and the unrecorded area according to whether or not to record; And comparing the tracking error signal detected after the area move with the tracking error signal detected after the area move and adding or subtracting the magnitude of the tracking error signal detected after the area move. Way. The method of claim 1, And the recording area and the unrecorded area are discriminated according to the presence or absence of a high frequency signal detected as a sum signal of two-split reflected light in the track direction. Area discrimination means for discriminating between the recording area and the unrecorded area; Error signal detecting means for detecting the magnitude of the tracking error signal by temporarily stopping the objective lens after moving the area between the recording area and the unrecorded area depending on whether or not to record; And a servo control means for comparing the tracking error signal detected before the area movement with the tracking error signal detected after the area movement and adding or subtracting the magnitude of the tracking error signal detected after the area movement. Servo control. The method of claim 3, wherein And the area discriminating means discriminates the recording area and the unrecorded area according to the presence or absence of a high frequency signal detected as a sum signal of two-split reflected light in the track direction. The method of claim 3, wherein A preamplifier connected to an output end of an optical pickup and detecting the tracking error signal; An actuator for driving the objective lens as the objective lens is mounted and a driving current is applied thereto; A servo filter connected between the error signal detecting means and the actuator to perform low-pass gain compensation and phase compensation in a high frequency band with respect to the tracking error signal; An actuator driver connected between the servo filter and the actuator to drive the actuator; A pause signal generator for generating a pause signal by the control of the servo control means; And a switch for switching a signal path between the servo filter and the actuator driver and a signal path between the pause signal generator and the actuator driver. The method of claim 3, wherein And the servo control means adjusts a gain value of the error signal detecting means differently in the recording area and the unrecorded area. The method according to claim 3 or 5, wherein And the servo control means adjusts a gain value of the preamplifier differently in the recording area and the unrecorded area. The method according to claim 3 or 5, wherein And the control means adjusts a gain value of the servo filter differently in the recording area and the unrecorded area. The method according to claim 3 or 5, wherein And the control means adjusts a gain value of the actuator driver in the recording area and the unrecorded area differently.