KR100285764B1 - Track Servo Control Method in Optical Disc Apparatus and Apparatus Thereof - Google Patents

Abstract

The present invention relates to a track servo control method for equalizing a tracking servo signal detected with different magnitudes in a recording area and an unrecorded area.

The present invention discriminates the recording area and the unrecorded area, detects the magnitude of the tracking servo signal detected in the recording area and the unrecorded area, and makes the servo loop gain constant in the recorded area and the unrecorded area by the magnitude of the tracking error signal. Adjust the loop gain.

According to the present invention, a stable tracking servo can be realized by making the signal levels of the tracking error signals detected in the recording area and the unrecorded area the same, as well as a case where there is a defective area or some eccentricity of the optical disc itself. In addition, stable tracking servo can be performed and the seek speed for the target track can be reduced.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 for equalizing tracking servo signals detected at different sizes in a recording area and an unrecorded area.

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 a power amplifier 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 TE1 by differentially amplifying the two-split reflected light signal in the track direction supplied from the photodetector. 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 TE1 so that the level of the tracking error signal is equal to or greater than 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-based optical disk, the tracking error signal TE1 detected is very low. Accordingly, the gain adjusting amplifier 6 amplifies the tracking error signal TE1 at a higher amplification factor 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 for the low frequency gain and the phase compensation in the high frequency band with respect to the tracking error signal TE2 supplied from the gain adjusting amplifier 6. The power amplifier 10 serves to amplify 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 a 'recording area') and an unrecorded area (hereinafter referred to as an '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 reflected by the pit becomes low, and in the unrecorded area, since the mirror section without the pit is continuously totally reflected almost, the intensity of the reflected light becomes 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. Further, the tracking error signal TE1 is detected at a larger peak level (or magnitude) 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, when the servo loop gain is fixed based on the recording area, the seek 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 adder 25 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 tracking error signal detected from the DVD-RAM also changes its peak level due to the difference in the amount of light reflected between the recording area and the unrecorded area as in the above-described 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 insecure tracking servo as described above. 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 disk 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 error signal detection circuit 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 illustrating a track servo control apparatus of the optical disk apparatus according to the embodiment of the present invention.

6 is an output waveform diagram of the track servo control device shown in FIG. 5;

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

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

<Description of the reference numerals for the main parts of the drawings>

2: optical pickup 4: preamplifier

6,16 gain adjustment amplifier 8,18 servo filter

10,20: power amplifier 12: actuator

21,30,24: amplifier 22,28: switcher

23,29: Low pass filter & holder 25: Adder

26 Inverter 27 Buffer

32: Recorded / unrecorded area judge 34: Tracking error signal magnitude measuring instrument

36 controller

In order to achieve the above object, the track servo control method of the optical disc apparatus according to the present invention comprises the steps of determining a recording area and an unrecorded area, detecting a magnitude of a tracking error signal detected in the recording area and an unrecorded area, and tracking. And adjusting the servo loop gain such that the servo loop gain is constant in the recording area and the unrecorded area by the magnitude of the error signal.

An apparatus for controlling a track servo of an optical disk apparatus according to the present invention includes area discriminating means for discriminating a recording area and an unrecorded area, magnitude detecting means for detecting the magnitude of a tracking error signal detected in the recording area and an unrecorded area, and tracking error signal. And control means for adjusting the servo loop gain such that the servo loop gain is constant in the recording area and the unrecorded area by the magnitude.

Other objects and features of the present invention in addition to the above object will be 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.

5 is a block diagram illustrating 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 includes an optical pickup 2 for photoelectrically converting light reflected from the disk by irradiating light onto the optical disk, and an actuator 12 for driving an objective lens. And a preamplifier 4, a gain adjustment amplifier 16, a servo filter 18 and a power amplifier 20 connected in series between the optical pickup 2 and the actuator 12, and an output terminal of the optical pickup 2; A recording / unrecording area determiner 32 connected to a high frequency signal RF, a tracking error signal magnitude measuring device 34 connected to an output terminal of the preamplifier 4, and receiving a tracking error signal TE1; And a controller 36 connected in common to the output terminals of the recorded / unrecorded area determiner 32 and the tracking error signal magnitude measuring instrument 34, and connected to the control signal input terminal of the gain adjusting amplifier 16. 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 split-split reflected light signal in the track direction photoelectrically converted from the optical pickup 2 is added by an adder not shown. The high frequency signal RF detected by this adder amplifier is input to the recorded / unrecorded area determiner 32. The recorded / unrecorded area determiner 32 generates an area judgment signal having a specific logic value according to the presence or absence of a high frequency signal RF input thereto, and supplies it to the controller 36. 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. The tracking error signal magnitude measuring unit 34 detects a peak-to-peak value level, that is, a magnitude, of the tracking error signal TE1 input from the preamplifier 34 and supplies it to the controller 36. Since the gain adjusting amplifier 16 has a difference in reflectance according to the type of optical disc, the tracking error signal TE1 is amplified so that the level of the tracking error signal is greater than or equal to a predetermined reference value. In addition, the gain adjusting amplifier 16 controls the control of the controller 36 with respect to the tracking error signal detected in 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 gain value adjusted by the amplify the tracking error signal. That is, the gain adjusting amplifier 16 amplifies the size of the tracking error signal that varies depending on the type of optical disk to be equal to or greater than a predetermined reference value, and amplifies the size of the tracking error signal that varies depending on the recording area or the unrecorded area to different gain values. The tracking error signal TE2 having a uniform magnitude is supplied to the servo filter 18. The servo filter 18 compensates the low pass gain required in the servo system by compensating for the low frequency gain and the phase compensation in the high frequency band with respect to the tracking error signal TE2 supplied from the gain adjusting amplifier 16. The power amplifier 20 amplifies the output signal of the servo filter 18 with a driving power suitable for driving the actuator 12. The actuator 12 includes an objective lens and a bobbin (not shown) installed in the optical pickup 2 so as to be movable by wire springs or leaf springs, depending on the polarity and level of the current supplied from the power amplifier 20. The lens moves in the inner circumferential direction or the outer circumferential direction to follow the center of the track.

The controller 36 determines the area currently accessed according to the area determination signal input from the recorded / unrecorded area determiner 32, and shows different sizes M1 and M2 in the recorded area and the unrecorded area as shown in FIG. The gain value of the gain adjusting amplifier 16 is adjusted so that the tracking error signal TE1 detected as is equal to the same predetermined reference magnitude M_ref.

FIG. 6 is a waveform diagram showing an output waveform of the track servo control device shown in FIG. 5, in which an optical pickup detects a tracking error signal detected when a disc having a repeated recording / unrecording area is moved from position a to position b. (TE1), the high frequency signal RF and the tracking error signal TE2 corrected by the gain adjustment adjusted according to the recording area and the unrecorded area.

Referring to FIG. 6, the tracking error signal supplied from the gain adjusting amplifier 16 to the servo filter 18 by adjusting the gain value of the gain adjusting amplifier 16 by the controller 36 according to the recording area and the unrecorded area. The size of TE2) has the same predetermined reference size M_ref regardless of the recording area and the unrecorded area. Therefore, when the optical pickup moves across the plurality of recording areas and unrecorded areas from the playback position a to the recording position b and records the information, a defective area exists in the recording area or the unrecorded area, or the eccentricity of the optical disc itself is somewhat present. In this case, it is possible to perform stable tracking servo and reduce the seek speed for the target track.

Further, the present invention adjusts the gain of the gain adjusting amplifier 16 according to the recording area and the unrecorded area as in the above-described embodiment so that the magnitude of the tracking error signal is the same regardless of the recording area and the unrecorded area. As can be seen from FIG. 7 and FIG. 8, the gain of the servo filter 18 or the power amplifier 20 may be adjusted instead of the gain adjusting amplifier 16.

7 is a block diagram illustrating a track servo control apparatus of the optical disk apparatus according to the second embodiment of the present invention. In FIG. 7, blocks having the same function as the blocks shown in FIG. 5 are given the same reference numerals, and detailed description thereof will be omitted.

In the configuration of FIG. 7, the track servo control apparatus of the optical disk apparatus according to the present invention includes an optical pickup 2 for photoelectrically converting light reflected from the disk by irradiating the optical disk with light, and an actuator 12 for driving an objective lens. And a preamplifier 4, a gain adjustment amplifier 16, a servo filter 18 and a power amplifier 20 connected in series between the optical pickup 2 and the actuator 12, and an output terminal of the optical pickup 2; A recording / unrecording area determiner 32 connected to a high frequency signal RF, a tracking error signal magnitude measuring device 34 connected to an output terminal of the preamplifier 4, and receiving a tracking error signal TE1; And a controller 37 connected in common to the output terminals of the recording / unrecording area determiner 32 and the tracking error signal magnitude measuring instrument 34, and connected to the control signal input terminal of the servo filter 18. Since the gain adjusting amplifier 16 has a difference in reflectance according to the type of optical disc, the tracking error signal TE1 is amplified so that the level of the tracking error signal is greater than or equal to a predetermined reference value. The servo filter 18 compensates the low pass gain required in the servo system by compensating for the low frequency gain and the phase compensation in the high frequency band with respect to the tracking error signal TE2 supplied from the gain adjusting amplifier 16. In addition, the servo filter 18 controls the controller 36 for tracking error signals of different sizes detected in 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 overall gain of the servo loop is adjusted by the gain value adjusted by the control of. The power amplifier 20 amplifies the output signal of the servo filter 18 with a driving power suitable for driving the actuator 12. The controller 36 determines the area that is currently accessed according to the area determination signal input from the recorded / unrecorded area determiner 32, so that the tracking error signal TE1 detected by different sizes in the recorded area and the unrecorded area is the same. The gain value of the servo filter 18 is adjusted to have a reference size M_ref.

8 is a block diagram illustrating a track servo control apparatus of the optical disk apparatus according to the third embodiment of the present invention. In FIG. 8, blocks having the same function as the blocks shown in FIG. 5 are given the same reference numerals and detailed description thereof will be omitted.

In the configuration of FIG. 8, the track servo control apparatus of the optical disk apparatus according to the present invention includes an optical pickup 2 for photoelectrically converting light reflected from the disk by irradiating light onto the optical disk, and an actuator 12 for driving an objective lens. And a preamplifier 4, a gain adjustment amplifier 16, a servo filter 18 and a power amplifier 20 connected in series between the optical pickup 2 and the actuator 12, and an output terminal of the optical pickup 2; A recording / unrecording area determiner 32 connected to a high frequency signal RF, a tracking error signal magnitude measuring device 34 connected to an output terminal of the preamplifier 4, and receiving a tracking error signal TE1; And a controller 36 connected in common to the output terminals of the recorded / unrecorded area determiner 32 and the tracking error signal magnitude measuring instrument 34, and connected to the control signal input terminal of the power amplifier 20. Since the gain adjusting amplifier 16 has a difference in reflectance according to the type of optical disc, the tracking error signal TE1 is amplified so that the level of the tracking error signal is greater than or equal to a predetermined reference value. The servo filter 18 compensates the low pass gain required in the servo system by compensating for the low frequency gain and the phase compensation in the high frequency band with respect to the tracking error signal TE2 supplied from the gain adjusting amplifier 16. The power amplifier 20 is adapted to drive the actuator 12 to a tracking error signal detected in a recording area or an unrecorded area if the optical disk currently accessed is a recordable optical disk, for example, CD-RW or CD-R. In addition, the magnitude of the tracking error signal is adjusted by the gain value adjusted by the control of the controller 36 so that the overall gain of the servo loop becomes constant in the recording area or the unrecorded area. The controller 36 determines the area that is currently accessed according to the area determination signal input from the recorded / unrecorded area determiner 32, and servos according to the tracking error signal TE1 detected in different sizes in the recorded area and the unrecorded area. The gain value of the power amplifier 20 is adjusted so that the overall gain of the loop is the same.

On the other hand, the tracking servo method for an optical disc such as a DVD-RAM determines a recording area and an unrecorded area in the user information area and detects the magnitude of a tracking error signal in the record area and an unrecorded area as in the above-described embodiment of the present invention. 3, by adjusting the gain of the preamplifier 4 or the third amplifier 30 so that the tracking error signals have the same magnitude in the recording area and the unrecorded area, stable 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, as well as the optical disc itself. Even if a defective area exists or there is some eccentricity of the optical disc itself, stable tracking servo can be performed and the seek speed for the target track can be reduced.

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 detected in the recording area and the unrecorded area; And adjusting the servo loop gain such that the servo loop gain is constant in the recording area and the unrecorded area by the magnitude of the tracking error signal. 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; Magnitude detecting means for detecting the magnitude of the tracking error signal detected in the recording area and the unrecorded area; And control means for adjusting the servo loop gain such that the servo loop gain is constant in the recording area and the unrecorded area by the magnitude of the tracking error signal. 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 gain adjustment amplifier connected between the preamplifier and the actuator for amplifying the tracking error signal with a gain value different according to the type of the recording medium so as to be equal to or greater than a reference value for a tracking error signal whose size varies depending on the type of the recording medium. Wow, A servo filter connected between the gain adjusting amplifier and the actuator to perform low pass gain compensation and phase compensation in the high frequency band with respect to the tracking error signal; And a power amplifier connected between the servo filter and the actuator to amplify the output signal of the servo filter to a level suitable for driving the actuator. The method according to claim 3 or 5, wherein And the control means is connected to the control terminal of the preamplifier and controls the gain value of the preamplifier differently according to the recording area and the unrecorded area. The method according to claim 3 or 5, wherein And the control means is connected to a control terminal of the gain adjusting amplifier to control a gain value of the gain adjusting amplifier differently according to the recording area and the unrecorded area. The method according to claim 3 or 5, wherein And the control means is connected to a control terminal of the servo filter to control gain values of the servo filter differently according to the recording area and the unrecorded area. The method according to claim 3 or 5, wherein And the control means is connected to a control terminal of the power amplifier so as to control gain values of the power amplifier differently according to the recording area and the unrecorded area.