KR100577166B1 - Method for controlling servo of optical record/player - Google Patents

Abstract

A servo control method of an optical record player, wherein information about a data recording area is read from an unrecorded track adjacent to a record track, i. By determining the defocus based on the amount of change in the level, the focus servo is performed, thereby preventing deterioration of data due to defocus during recording and playback, and stably operating the system.

Defocus, LPP

Description

Servo control method of optical record player {Method for controlling servo of optical record / player}

1 is a block diagram of an optical recording / reproducing apparatus according to the present invention;

2 is a graph showing an example in which the level of the push-pull signal is changed by the defocus offset change.

3 (a) to 3 (h) show an example in which the level of the push-pull signal is changed by the defocus offset change.

Explanation of symbols for main parts of the drawings

101: optical disk 102: optical pickup

103: encoder 104: LD drive unit

105: RF and servo error generation unit 106: data decoder

107: servo control unit 108: focus servo drive unit

109: tracking servo drive 110: tilt drive

201: voltage level detector

The present invention relates to an optical recording medium system, and more particularly, to a servo control method of an optical recording player for detecting and compensating for defocus of an optical recording medium.

Optical recording media that can be freely and repeatedly rewritable, for example, optical discs include a rewritable compact disc (CD-RW) and a rewritable digital versatile disc (DVD-RW, DVD-RAM). have.

Here, the difference between DVD-RAM and DVD-RW is that, in the case of DVD-RAM, data is recorded in both lands and grooves, whereas DVD-RW only records data in grooves. In other words, the DVD-RW pre-pits the land track instead of the header 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. At this time, the location information recorded in the land is called a land-pre-pit (hereinafter referred to as LPP). The position information can also be recorded in a wobbling shape along the track, such as a CD-R or a CD-RW. Here, the wobbling is a modulated clock that modulates a constant clock to supply information to the disk, for example, information on the corresponding position, information about the rotation speed of the disk, and the like to the power of the laser diode, thereby controlling the information by changing the light beam of the laser. Is recorded at the boundary of the track.

In order to record information on such an optical disk or to reproduce the recorded information, focus control is performed through optical pickup.

At this time, if the optical focus is shifted from the disk surface during focus control, that is, the focus servo (hereinafter referred to as defocus), there is a problem in that data quality during recording and reproducing is deteriorated, resulting in unstable operation of the system. In particular, in the case of the above-described DVD-RW, the defocus has a great influence on the recording characteristics.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a servo control method of an optical recorder which detects and compensates defocus with a change in LPP level indicating a physical position of a recording track.

In the servo control method of the optical recording and reproducing apparatus according to the present invention for achieving the above object, optical information in which information about a data recording area is present on an unrecorded track (eg, land track) adjacent to a recording track (eg, groove track). And reading the information present in the unrecorded track of the recording medium, detecting the level, and performing the focus servo by determining the defocus based on the change amount of the level.

The level of the step is characterized in that the peak-to-peak voltage of the push-pull signal detected in the unrecorded track.

The servo control step is characterized in that if the level is less than the reference value is determined to defocus.

The servo control step may be characterized in that the focus servo is performed in a direction in which the level is maximized when it is determined as defocus.

The present invention is to detect the defocus by the level change of the push-pull signal detected in the LPP region and to perform the focus servo in the direction in which the level is maximized.

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.

1 is a block diagram of an optical recording and reproducing apparatus for defocus detection according to the present invention, wherein an optical disk 101 capable of rewriting data and an optical pickup 102 for recording and reproducing information on the optical disk 101 are shown in FIG. And an RF and servo error generator 105 for generating RF and servo error signals from the electrical signal output from the optical pickup 102, and RF and servo error generator if data to be written to the optical disc 101 is generated. An encoder 103 for encoding data to be recorded by the control signal of 105 into a recording pulse of a format required by the optical disk 101, and the recording pulse of the encoder 103 as the recording power of the laser diode LD. LD driver 104 for converting and driving LD in optical pickup 102, data decoder 106 for processing the RF signal detected by RF and servo error generator 105 and restoring data, RF and servo Poker detected by the error generator 105 The servo control unit 107 and the servo control unit which generate a focus driving signal and a tracking driving signal by processing a signal error signal FE and a push pull signal TE, respectively, and detect a tilt and a detrack from the push pull signal. The focus servo driver 108 which receives the focus drive signal output from the input signal 107 and drives the focus actuator in the optical pickup 102, and the optical pickup 102 which receives the tracking drive signal output from the servo controller 107. Tracking servo driver 109 for driving the tracking actuator in the inside, tilt driver 110 for compensating the tilt by controlling the optical pickup 102 according to the tilt drive signal output from the servo controller 107, and defocus detection In order to detect the peak-to-peak voltage of the push-pull signal detected by the RF and servo error generator 105, the voltage level detector 201 outputs the peak-to-peak voltage to the servo controller 107. It is.

In this case, the tilt driver 110 is a tilt servo mechanism that corrects the tilt by moving the optical pickup or the disk itself.

The push-pull signal is a tracking error signal detected by the push-pull method, and splits the reflected light from the optical disc into two and compares the respective intensities. That is, when the laser beam is irradiated to the pit, diffraction occurs. In the correct tracking state, the left and right diffraction light is symmetrical about the optical axis. When the reflected light is detected by the two-segment photodetector in the optical pickup 102, the output difference becomes zero. In other words, the push-pull signal becomes zero. However, if the spot deviates to the left with respect to the pit, the diffraction effect of the laser light incident on the left side of the pit decreases, and the diffraction light becomes asymmetrical to detect a push-pull signal in which the reflected light on the left side increases. On the contrary, if the signal deviates to the right side, a push pull signal in which the right side increases is detected. Since the land (LPP) area in which the groove track position information is physically pre-fitted and recorded is a non-recording area, the reflectance is high. Therefore, the push-pull signal greatly changes up and down to follow it in the LPP region.

In the present invention configured as described above, the optical disc 101 has a signal track structure of land and grooves, but since the land track is pre-fitted, data can be recorded or reproduced only in the groove track.

At this time, the optical pickup 102 causes the light beam focused on the objective lens to be placed on the signal track of the optical disc 101 under the control of the servo control unit 107, and further condenses the light reflected by the signal recording surface back to the objective lens. It then enters the photo detector for detection of the focus error signal and 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 105.

The RF and servo error generator 105 detects an RF signal for data reproduction, a focus error signal FE for servo control, a push-pull signal TE, and the like from the electrical signal output from the photo detector. At this time, the RF signal is output to the data decoder 106 for reproduction, servo error signals such as FE and push-pull signals are output to the servo control unit 107, and control signals for data recording to the encoder 103. Is output.

The encoder 103 encodes data to be recorded according to a control signal into a recording pulse of a format required by the optical disk 101, and then outputs the data to the LD driver 104. The LD driver 104 supplies the data to the recording pulse. The LD of the optical pickup 102 is driven at the corresponding recording power to record data on the optical disk 101.

In addition, when reproducing the data recorded on the optical disc 101, the data decoder 105 restores the original data from the RF signal detected by the RF and servo error generation unit 105.

The servo controller 107 processes a focus error signal FE to output a driving signal for focusing control to the focus servo driver 108, and processes a push-pull signal to signal a drive signal for tracking control. Output to the tracking servo driver 109.

At this time, the focus servo driver 108 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. In addition, the tracking servo driver 109 drives the tracking actuator in the optical pickup 102 to move the objective lens of the optical pickup 102 in a radial direction to correct the position of the beam and follow a predetermined track. do.

Meanwhile, the present invention should detect and compensate the defocus of the optical disc 101. For this purpose, the voltage detector 201 detects the peak-to-peak voltage Vpp of the push-pull signal and the servo controller 107 Will output

The servo controller 107 detects defocus using the peak-to-peak voltage Vpp of the push-pull signal detected in the LPP region.

That is, the level (mV) of the push-pull signal detected in the LPP region changes according to the defocus offset, and Table 1 shows this.

 Defocus Offset []    LPP [mV]        8      105        7.5      142        6.5      167        5.5      203        4.5      222        3.5      187        2.5      155        1.5      144

FIG. 2 is a graph of Table 1, in which the level of the push-pull signal (Vpp) in the LPP region, that is, the LPP level is not defocused, that is, the maximum in the positive focus state and defocused. Its size decreases in proportion to. For example, in Table 1, the point at which the defocus offset amount is 4.5 is the point at defocus zero.

3A to 3H show examples in which the level of the push-pull signal detected in the state where the focus servo and the tracking servo are turned on and fixed at tilt 0 and detrack offset 5.0 is different depending on the defocus offset. Since (e) of FIG. 3 is the defocus offset 4.5, the level Vpp of the push-pull signal is the largest, and it is determined that the focus is best controlled at this time. That is, the Vpp of the push-pull signal is the largest when it is positively focused as shown in (e) of FIG. 3, and the push-pull as shown in (a) to (d) and (f) to (h) of FIG. The Vpp of the signal is reduced. In this case, the wobble center does not change due to the defocus offset change, and the push-pull signal always maintains a symmetrical relationship with respect to the wobble center. That is, only the level of the push-pull signal changes due to the defocus offset change.

Therefore, when the Vpp of the push-pull signal detected in the LPP region is equal to or less than the preset reference value, it may be determined that the tilt has occurred.

Therefore, the servo control unit 106 performs the focus servo by detecting the defocus offset amount which becomes the positive focus by changing the defocus offset during recording / reproducing. That is, the focus servo driver 108 performs the focus servo in a direction in which the level of the push-pull signal is maximized under the control of the servo controller 106.

On the other hand, the defocus detection and compensation of the present invention can be applied to all of the disks (DVD-R, DVD-RW, ...) that are LPP.

As described above, according to the servo control method of the optical recorder according to the present invention, the focus is performed by detecting the defocus with the amount of change in the voltage level of the push-pull signal detected from the optical disk with the LPP, and performing recording and reproduction. It prevents the deterioration of data quality due to defocus and operates the system stably.

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 (4)

A servo control method for an optical recording medium in which information about a data recording area is present in an unrecorded track adjacent to a recording track, Reading information present in the unrecorded track to detect its level; And performing focus servo by determining the defocus based on the amount of change of the level. The method of claim 1, wherein the level of the step is And a peak-to-peak voltage of the push-pull signal detected by the unrecorded track. The method of claim 1, wherein the servo control step And if the level is smaller than the reference value, determining that the focus is defocused. The method of claim 1, wherein the servo control step And a focus servo is performed in a direction in which the level is maximized when it is determined to be defocused.

Images