KR100651966B1 - Method and apparatus for controlling tracking of optical record medium - Google Patents

Abstract

The present invention relates to a tracking control method and apparatus for an optical recording medium. In particular, a rewritable disc in which a mirror signal is not properly generated, particularly in a prepit area of a lead-in of a DVD-RAM, is formed by sliced an envelope waveform of a tracking error signal detected by the PP method. After detecting the mirror-corresponding signal, the direction difference of the objective lens is detected by comparing the phase difference with the TZC signal generated from the TE signal detected by the DPD method. This makes it possible to ensure the stability of the track servo and to improve the access performance of the lead-in area.

Objective direction, DPD, PP, Prefit

Description

Method and apparatus for controlling tracking of optical record carrier {Method and apparatus for controlling tracking of optical record medium}

1 is a view showing the structure of a typical DVD-RAM

2 is a block diagram of a general optical disc recording and reproducing apparatus;

3 is a view illustrating a structure of a general photodetector

4 is a block diagram of an optical disc recording and reproducing apparatus for tracking control according to the present invention;

5A to 5G are operation waveform diagrams of each part of FIG.

Explanation of symbols for main parts of the drawings

201: DPD signal generator 202: TZC generator

203: Brake pulse generator 204: Objective lens direction detection unit

205: PP signal generator 206: signal detector

207: PP mirror generation unit 208: track control unit

The present invention relates to an optical recording medium system, and more particularly, to a tracking control method and apparatus in a lead-in area of a rewritable optical recording medium.

In general, an optical recording medium, that is, an optical disc recording and reproducing apparatus for recording and reproducing an optical disc, reproduces data recorded on the optical disc using an optical disc such as a compact disc (CD), a digital versatile disc (DVD), or the like as a recording medium. And a device for recording data on the disc.

At this time, the DVD-RW, DVD-R, DVD-RAM, etc. of the DVD is a rewritable digital versatile disc.

Among them, the DVD-RAM records data in both lands and grooves, whereas the DVD-RW / R records data only in grooves. That is, the DVD-RW / R pre-pits the land track instead of the header area of the DVD-RAM indicating the position information to record the position information on the groove track, and does not record the data on the land track. In other words, information about the physical address of the groove track is previously recorded in the land in the form of a pit.

In addition, the position information may be recorded in a wobbling shape along the track boundary.

Here, the wobble is a control signal by changing the light beam of the laser by supplying information to be applied to the disk by modulating a constant clock, for example, information of the corresponding position, information about the rotation speed of the disk, and the like to the power of the laser diode. Is recorded at the boundary of the track.

Fig. 1 is a view showing the structure of the above-described DVD-RAM, which is composed of a lead-in area, a lead-out area, and a data area in which actual data is recorded.

At this time, the embossed data zone in the lead-in area does not have a land / groove structure, and there is no wobble and only a prepit. The re-writable data area, the data area and the lead-out area of the lead-in area have a land / groove structure, wobble, and can rewrite and reproduce data.

In addition, in the case of the DVD-RAM, control information such as position information is recorded by pre-formatting the header area at the start of the sector for each sector, and wobbling at a predetermined frequency along the track. Is formed.

Fig. 2 is a general block diagram of an optical disk recording and reproducing apparatus for recording data on such DVD-based optical disks and reproducing the recorded data, wherein the optical pickup 102 is controlled by the servo controller 104. The light beam focused on the optical disk 101 is placed on the signal track of the optical disk 101, and the light reflected from the signal recording surface is again focused by the objective lens and then incident on the photo detector for detection of the focus error signal and the tracking error signal.

The photo detector includes a plurality of photo detectors, and an electrical signal proportional to the amount of light obtained from each photo detector is output to the RF and servo error generator 103.

The RF and servo error generation unit 103 is an RF signal for reproducing data, a focus error (FE) signal for servo control, and a tracking error (TE) from an electrical signal output from each photodetector of the photodetector. Detect a signal or the like.

The detected RF signal is output to a data decoder (not shown) for reproduction, and servo error signals such as FE and TE are output to the servo controller 104.

The servo controller 104 processes the focus error (FE) signal to output a driving signal for focusing control to the focus servo driver 105, and processes the tracking error (TE) signal to process the driving signal for tracking control. Is output to the tracking servo driver 106.

At this time, the focus servo driver 105 moves the optical pickup 102 up and down by driving the focus actuator in the optical pickup 102 so that the optical disk 101 follows the vertical movement along with the rotation.

The tracking servo driver 106 moves the objective lens of the optical pickup 102 in the radial direction by driving the tracking actuator in the optical pickup 102 to correct the position of the beam and track a predetermined track. .

In this case, the tracking control used for the DVD-based optical disc in the RF and servo error generation unit 103 and the servo control unit 104 is generally a three-beam method, a push-pull (PP) method, phase difference detection ( Differential phase detection (DPD) methods are available.

Among these, the push-pull method divides the photodetector of the photodetector for detecting the reflected light from the optical disk into two tracks in the track direction, and then detects the tracking error signal from the light quantity balance of both photodetectors. This utilizes the fact that the intensity distribution of light diffracted and reflected by the pit and then incident on the objective lens changes with the relative positional change between the pit and the spot.

If the shadow of the pit is equally detected by both photodetectors, the tracking error signal TE becomes zero, which 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).

일 때 즉, 피트에 의한 회절이 가장 유효하고 변조도가 최대로 될 때에는 상기 푸시-풀법으로는 트랙킹 에러 신호를 얻을 수 없다. 즉, 피트의 깊이가

일 때의 패턴은 대칭 패턴이 되므로, 2분할된 광 검출기로부터는 트랙킹 에러 신호를 얻을 수 없다.At this time, the push-pull method has several conditions. One of them is called the wavelength of light, and the depth of the pit is

In other words, when the diffraction by the pit is most effective and the modulation degree is maximized, the tracking error signal cannot be obtained by the push-pull method. That is, the depth of the feet

Since the pattern at the time becomes a symmetrical pattern, the tracking error signal cannot be obtained from the photodetector divided into two.

On the other hand, the DPD method is an improvement of the push-pull method. Similar to the push-pull method, the DPD method uses a light intensity distribution according to a change in the relative position of the beam and the pit, but instead uses a quad split photo detector.

That is, in the DPD method, the light intensity distribution is divided into four light detectors to detect the phase difference to generate a tracking error signal.

의 피트 깊이에서도 트랙킹 에러 신호가 나오며, 광 검출기 상에서 빔이 움직이더라도 그 영향이 적은 것이 장점이다. Therefore, the influence of the pit depth is small, for example,

The tracking error signal is generated even at the pit depth of, and the effect is small even if the beam moves on the photo detector.

For example, the photodetector may include four photodetectors (PDAs) that are specifically divided, i.e., quadrature, divided into a signal track direction (or tangential direction) and a radial direction of the optical disk as shown in FIG. If it is composed of, PDB, PDC, PDD, the photo detector outputs electrical signals a, b, c, d proportional to the amount of light obtained from each of the photo detectors PDA, PDB, PDC, PDD.

At this time, the DPD method is based on the electrical signal of (a + c) and the electrical signal of (b + d) based on the RF signal (ie, a + b + c + d) obtained from the electrical signal output from the photo detector The phase difference is detected to obtain a tracking error signal. This is also called hetero dyne method.

Here, the push-pull error signal means a tracking error signal obtained by the push-pull method, and the DPD error signal means a tracking error signal obtained by the DPD method.

이기 때문에 푸시-풀법으로는 트랙킹 에러 신호를 검출할 수 없다. 그래서, DVD-ROM에서는 DPD법을 이용하여 트랙킹 에러 신호를 얻고 있다. 또한, DVD-R이나 DVD-RW는 신호가 기록된 영역을 재생하는 경우에는 DPD법으로 트랙킹 에러 신호를 검출하며, 신호를 기록하는 경우에는 PP법으로 트랙킹 에러 신호를 검출한다. 또한, DVD-RAM의 경우에는 프리피트 영역만 DPD법으로 트랙킹 에러 신호를 검출하고, 그 외의 영역에서는 PP법으로 트랙킹 에러 신호를 검출한다.At this time, the DVD-ROM generates a tracking error signal by the DPD method. That is, in the case of the DVD-ROM, the depth of the pit is

For this reason, the tracking error signal cannot be detected by the push-pull method. Therefore, in the DVD-ROM, a tracking error signal is obtained by using the DPD method. In addition, the DVD-R or DVD-RW detects the tracking error signal by the DPD method when reproducing the area where the signal is recorded, and detects the tracking error signal by the PP method when recording the signal. In the case of DVD-RAM, only the prepit area detects the tracking error signal by the DPD method, and in other areas, the tracking error signal is detected by the PP method.

That is, in case of a disc divided into a prepit area and a land / groove data area such as a DVD-RAM, a tracking control method (eg, a prepit area is a DPD method and a data area is a push-pull method) is defined differently. Since the tracking error signal is generated in the prepit area by the DPD control method and the tracking error signal is generated by the push-pull method in the non-prepit area, for example, the data area.

At this time, the relative direction between the track on the disk and the objective lens, that is, the direction in which the objective lens crosses the track, is a factor that must be defined very accurately in track servo control.

Therefore, in the pit format or groove recording method of the CD or DVD system, a mirror signal is generated from the RF signal to detect the direction of the tracking actuator.

In other words, the track between the tracks is called a mirror area, and the area where light is totally reflected, and the signal indicating that the tracking actuator is between the track and the track is a mirror signal.

However, in the case of DVD-RAM, mirror detection is not possible because it is a land / groove (hereinafter referred to as L / G) recording method. That is, in the L / G recording method, since data is recorded in both the land and the groove, the mirror signal cannot be formed from the RF signal. At this time, the tracking error does not form the mirror signal and the tracking error occurs in the same way as the groove recording method or the L / G recording method, and thus the direction of the tracking actuator cannot be detected. This will eventually disable the auto break system, making it impossible to perform a stable track servo properly.                         

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to stably detect and control a relative direction between a track on an disc and an objective lens in a prepit area of a rewritable optical recording medium. The present invention provides a control method and apparatus.

The tracking control method of the optical recording medium according to the present invention for achieving the above object comprises the steps of generating a tracking zero cross (TZC) signal from the tracking error signal detected by the DPD method, tracking by the push-pull method Detecting an envelope of an error signal and slicing it to a preset slice level, comparing a phase between the TZC signal and the sliced signal of the above step, detecting a moving direction of the objective lens from the comparison result, and using the tracking control Characterized in that comprises a.

The direction detecting step may further include generating a brake pulse in a direction opposite to the moving direction of the objective lens when the direction of the objective lens is detected.

In the slicing step, the bottom envelope of the tracking error signal detected by the push-pull method is detected, and the detected envelope waveform is sliced to a preset slice level.

The slicing step may be characterized by slicing the detected envelope waveform to a preset slice level after detecting the peak envelope of the tracking error signal detected by the push-pull method.

In the slicing step, the peak envelope and the bottom envelope of the tracking error signal detected by the push-pull method are respectively detected, and the difference between the detected two envelope waveforms is obtained, and the difference signal is sliced to a preset slice level.

In the direction detecting step, the direction of the objective lens is detected by checking the phase level of the TZC signal at the rising edge or the falling edge of the sliced signal.

The direction detecting step may be performed in a prepit area for controlling tracking with a tracking error signal detected by the DPD method.

An apparatus for controlling tracking of an optical recording medium according to the present invention includes a TZC generation unit for generating a tracking zero cross (TZC) signal from a tracking error signal detected by the DPD method, and an envelope of the tracking error signal detected by the push-pull method. After detecting, compare the phase of the TZC signal generated by the mirror generation unit, the TZC generation unit and the mirror generation unit and the sliced signal, and detects the moving direction of the objective lens from the comparison result And a controller configured to generate a brake pulse in a direction opposite to the detected movement direction of the objective lens to perform tracking control.

The controller detects the phase level of the TZC signal at the rising edge or the falling edge of the sliced signal, and detects a moving direction of the objective lens.                     

The control unit performs tracking control by detecting a moving direction of an objective lens in a prepit area that controls tracking using a tracking error signal detected by the DPD method.

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.

이므로 PP 에러 신호가 DVD-ROM과 달리 어느 정도 잘 생성되기 때문이다.The present invention detects a tracking zero cross (TZC) signal from a TE signal detected by a DPD method in a prepit area of a DVD-RAM, and then uses the phase relationship between the TZC signal and a TE signal detected by a PP method. It is used to detect the direction in which the and tracks cross, and use this for track control. This is because the lead-in area of the DVD-RAM is composed of prepits, and the land / groove depth difference is different.

This is because the PP error signal is generated to some extent unlike DVD-ROM.

Fig. 4 is a block diagram showing the construction of the optical recording medium recording and reproducing apparatus according to the present invention, showing only the track control portion.

Referring to FIG. 4, the DPD signal generator 201 generates a tracking error signal DPD_TE by receiving the electrical signals a, b, c, and d output from the photo detector in the optical pickup, and the DPD error signal ( A TZC generator 202 for generating a TZC signal from DPD_TE), and a PP for generating a tracking error signal PP_TE in a radial direction by a push-pull method by receiving the electrical signals a, b, c and d outputted from the photodetector. PP mirror for generating PP mirror signal by slicing the signal generator 205, the signal detector 206 for detecting the envelope of the PP error signal PP_TE, and the envelope waveform of the signal detector 206 to a preset slice level. The objective unit direction detection unit 204 for detecting the direction of the objective lens by comparing the phase of the generation unit 207, the PP mirror signal and the TZC signal of the TZC generator 202, and the direction of the objective lens and the TZC signal. To generate a brake pulse The rake pulse generator 203 is configured to receive a brake pulse, a DPD error signal, a direction signal of an objective lens, a TZC signal, and the like, and generate a tracking drive signal.

In this case, the signal detector 206 may detect only the peak envelope of the PP error signal and output it to the PP mirror generator 207, or may detect only the bottom envelope and output the PP envelope generator 207 to the PP mirror generator 207. After detecting both the envelope and the bottom envelope, the difference between the two envelope signals may be output to the PP mirror generator 207.

4 shows an example of detecting the peak envelope and the bottom envelope of the PP error signal and outputting the difference between the two envelope signals to the PP mirror generator 207. The peak envelope detector 206-1 and the bottom envelope detector are shown in FIG. 206-2, and the difference signal generation unit 206-3.

In the present invention, the bottom envelope of the PP error signal is detected and output to the PP mirror generator 207 in the embodiment.

In the present invention configured as described above, if the configuration of the optical detector in the optical pickup 102 is the same as that of FIG. 3, the DPD signal generator 201 receives the electrical signals a, b, c, d outputted from the optical detector and receives RF. After generating the signal, the phase difference between (a + c) and (b + d) is obtained from the RF slice point based on the RF signal, and the DPD error signal DPD_TE is detected as shown in FIG. The TZC generator 202 slices the DPD error signal DPD_TE into an internal reference level, that is, a center level, and generates a TZC signal as shown in FIG. That is, the TZC signal is a signal that is turned on / off at the track cross time.

Meanwhile, the PP signal generator 205 detects the tracking error signal PP_TE in the radial direction by ad-bc the electrical signals a, b, c, and d output from the photo detector as shown in FIG. The signal is then output to the signal detector 206.

5 (a) and 5 (b), the PP error signal PP_TE is small at the center of the pit signal which is the track control point (eg, arrow) of the DPD error signal DPD_TE, and at the center of the land. It can be seen that a lot of PP_TE) is detected.

Accordingly, the peak envelope detector 206-1 and the bottom envelope detector 206-2 of the signal detector 206 detect the peak envelope and the bottom envelope of the PP error signal PP_TE, respectively, to detect the difference signal generator 206. -3) The subtractor 206-3 subtracts the bottom envelope signal from the peak envelope signal and outputs the bottom envelope signal to the PP mirror generator 207.

FIG. 5C illustrates an example in which only a bottom envelope of the PP error signal PP_TE is detected and output to the PP mirror generator 207.

The PP mirror generator 207 slices the output signal of the signal detector 206 to a preset slice level to generate a PP mirror signal as shown in FIG.

The TZC signal of FIG. 5D and the PP mirror signal of FIG. 5E are input to the objective lens direction detector 204.

At this time, a phase difference is generated between the TZC signal and the PP mirror signal according to the relative direction between the track and the objective lens, that is, the direction in which the objective lens and the track cross each other. That is, as shown in (d) and (e) of FIG. 5, it can be seen that the PP mirror signal is in phase in comparison with the TZC signal in the outer circumferential direction, and in phase in the inner circumferential direction.

Accordingly, the objective lens direction detector 204 may generate the objective lens direction signal by detecting the phase level of the TZC signal at the rising edge of the PP mirror signal. For example, if the phase of the TZC signal is-at the rising edge of the PP mirror signal, that is, in the outer circumferential direction, a low signal as shown in (f) of FIG. Output In this case, the direction of the objective lens may be detected by comparing the phase level of the TZC signal at the falling edge of the PP mirror signal, or may be detected by comparing the phase level of the PP mirror signal at the rising or falling edge of the TZC signal. This can be varied by the designer.

The direction signal of the objective lens detected by the objective lens direction detector 204 is output to the brake pulse generator 203 and the track controller 208.

The break pulse generator 203 generates a break pulse according to a TZC signal output from the TZC generator 202 and a direction signal of an objective lens output from the objective lens direction detector 204. For example, as shown in (g) of FIG. 5, when the objective lens direction signal is high, that is, when the direction of movement of the objective lens is the inner circumference, a brake pulse is generated in phase with the TZC signal. If the outer periphery is generated, a brake pulse is generated in reverse with the TZC signal and output to the track control unit 208.

The track control unit 208 generates a tracking drive signal from the DPD error signal DPD_TE during normal servo in the prepit area of the disc, and the brake pulse generator 203 at the track on during traverse or after free running. Tracking control is generated by generating a tracking drive signal with the generated brake pulse. This improves the access performance of the lead-in area of the DVD-RAM and achieves stable and fast track control.

For example, when the track is turned on after free running after the disc is inserted or when the track is turned on in a traverse state such as seek or track jump, the automatic brake operation is turned on to track on. That is, a kick pulse is generated while only the focus servo is turned on, and is applied to the tracking actuator in the optical pickup. When the kick pulse is applied, the speed of the tracking actuator is increased and the objective lens of the tracking actuator is pushed in one direction by acceleration. When the automatic brake system is operated to track on, the brake pulse generator 204 generates a brake pulse from the TZC signal according to the objective lens direction signal and applies the tracking pulse to the tracking actuator to reduce the speed of the actuator. . The brake pulse is an inverted pulse of the kick pulse, which is generated to stop the actuator stably and accurately at a desired position.

On the other hand, the present invention can be applied to both DVD-based disks (eg, DVD-RAM, DVD-RW / R), etc., in which mirror signals are hardly detected.

As described above, according to the tracking control method and apparatus for an optical recording medium according to the present invention, a tracking error signal detected by the PP method in a pre-pit area of a rewritable disc, in particular, a lead-in of a DVD-RAM, in which a mirror signal is not properly generated. The envelope waveform is sliced to detect the mirror-corresponding signal, and then the phase difference is compared with the TZC signal generated from the TE signal detected by the DPD method to detect the direction of travel of the objective lens and use it for tracking control. Therefore, it is possible to easily and accurately detect the moving direction of the objective lens in the disc structure, especially in the lead-in area of the DVD-RAM, in which the mirror signal is not easily detected, thereby ensuring the stability of the track servo. Access performance can be improved.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (11)

Claims [1] A tracking control method of an optical recording medium in which a tracking error signal is generated by receiving an electrical signal proportional to an amount of reflected light output from an optical pickup and generating a tracking error signal using a differential phase detection (DPD) method or a push-pull method. Generating a tracking zero cross (TZC) signal from the tracking error signal detected by the DPD method; Detecting an envelope of the tracking error signal detected by the push-pull method and then slicing to a preset slice level; And And comparing a phase between the TZC signal and the sliced signal in the above step, detecting a moving direction of the objective lens from the comparison result, and using the tracking control for tracking control. The method of claim 1, wherein the direction detecting step is And if the direction of the objective lens is detected, generating a brake pulse in a direction opposite to the movement direction of the objective lens. The method of claim 2, And the brake pulse is generated in a reverse phase or in phase with the TZC signal according to the direction of the objective lens. The method of claim 1, wherein the slicing step And detecting the bottom envelope of the tracking error signal detected by the push-pull method, and then slicing the detected envelope waveform to a preset slice level. The method of claim 1, wherein the slicing step And detecting the peak envelope of the tracking error signal detected by the push-pull method, and then slicing the detected envelope waveform to a preset slice level. The method of claim 1, wherein the slicing step Detecting the peak envelope and the bottom envelope of the tracking error signal detected by the push-pull method, obtaining a difference between the detected two envelope waveforms, and then slicing the difference signal to a preset slice level. Control method. The method of claim 1, wherein the direction detecting step is And checking the phase level of the TZC signal at the rising edge or falling edge of the sliced signal to detect the direction in which the objective lens travels. The method of claim 1, wherein the direction detecting step is A tracking control method for an optical recording medium, characterized in that it is performed in a prepit area for controlling tracking with a tracking error signal detected by the DPD method. A tracking control apparatus for an optical recording medium that receives an electrical signal proportional to an amount of reflected light output from an optical pickup and generates a tracking error signal by using a differential phase detection (DPD) method or a push-pull method to perform tracking control. A TZC generation unit for generating a tracking zero cross (TZC) signal from the tracking error signal detected by the DPD method; A mirror generation unit for detecting an envelope of the tracking error signal detected by the push-pull method and then slicing to a preset slice level; And Comparing the phase between the TZC signal and the sliced signal generated by the TZC generator and the mirror generator, detect the movement direction of the objective lens from the comparison result, and generate a brake pulse in a direction opposite to the detected movement direction of the objective lens. And a control unit configured to perform tracking control of the optical recording medium. The method of claim 9, wherein the control unit And detecting the moving direction of the objective lens by checking the phase level of the TZC signal at the rising edge or the falling edge of the sliced signal. The method of claim 9, wherein the control unit A tracking control apparatus for an optical recording medium, characterized in that tracking control is performed by detecting a moving direction of an objective lens in a prepit area controlling tracking with a tracking error signal detected by a DPD method.

Images