KR20000066460A - Method for recording/playback of optical recording medium - Google Patents

Abstract

PURPOSE: A method of reproducing a record of an optical recording medium detects a detract from a potential difference between a wobble signal recorded on a track and a lead channel 2 signal detected in a header area and then compensates the potential difference. CONSTITUTION: A method of reproducing a record of an optical recording medium comprises steps of detecting a wobble signal in a data area, calculating a difference between the wobble signal and a signal detected in a non-recording area and then outputting as a first difference signal, calculating a difference between the wobble signal and a signal detected in other non-recording area having a different phase with the non-recording area and then outputting as the first difference signal, obtaining a second difference signal between the first difference signals, determining as a detract if the second difference signal is beyond a reference value and then outputting a result value, and performing a tracking servo according to the result value. In the method, the difference signal is calculated using only a desired portion of the non-recording area or a variable frequency oscillator area of the non-recording area.

Description

Method for recording and reproducing an optical recording medium {Method for recording / playback of optical recording medium}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high density optical recording medium system, and more particularly to a method of recording and reproducing an optical recording medium for detecting and compensating for detrack of an optical recording medium.

In general, optical recording media are largely divided into three types: read-only ROM, write-once worm type, and rewritable rewritable type. Lose.

Among them, an optical recording medium freely and repeatedly rewritable, for example, a rewritable compact disc (CD-RW) and a rewritable digital versatile disc (DVD-RW, DVD-RAM), etc. There is this.

The above-described rewritable optical recording medium, such as an optical disc such as a DVD-RAM, has a signal track having a structure of land and groove, so that tracking control can be performed even on a blank disc in which no information signal is recorded. Recently, in order to increase the recording density, information signals are recorded in tracks of lands and grooves, respectively. To this end, the wavelength of the laser light of the optical pickup for recording / reproducing is shortened, and the numerical aperture of the objective lens for condensing is increased to reduce the size of the light beam for recording and reproducing.

Further, in such a high density optical disc, the distance between signal tracks, that is, the signal track pitch, is reduced in order to increase the recording density.

In this case, in the case of a rewritable disc, since the first disc has no information, disc control and recording are impossible.

For this purpose, disc tracks are created in lands and grooves, and information is recorded along the tracks. Information for random access and rotation control is recorded separately on the disc, so that tracking control can be performed on a blank disc in which no information signal is recorded. To do it.

The control information may be recorded by pre-formatting the header area at the start of the sector for each sector as shown in FIG. 1, or may be recorded in a wobbling shape along the track.

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.

The header area preformatted at the start of each sector is further composed of four header fields (header 1 field and header 4 field). Here, in the header 1 to header 4 fields, there is a variable frequency oscillator (VFO) region for generating a reference clock to synchronize bit synchronization of read channels. At this time, in the present invention, the VFO areas in each header field (header 1 field to header 4 field) are referred to as VFO1 to VFO4, respectively.

That is, VFO1 and VFO3 are in the header 1 and 3 fields, VFO2 and VFO4 are in the header 2 and 4 fields, and the length of the VFO1 and VFO3 areas in the header 1 and 3 fields is VFO2 and VFO4 in the header 2 and 4 fields. It is longer than the length of the area and the detection of the signal is more stable.

At this time, the four header fields are arranged staggered from the track center, Figure 1 is an example, the structure of the header field for the first sector in one track. 1, it can be seen that the track boundary of the user area in which actual data is recorded is wobbled.

In such an optical recording / reproducing apparatus, in order to record information or to reproduce the recorded information, tracking control is performed through optical pickup.

That is, the tracking control, for example, the tracking servo detects a tracking error signal from an electrical signal generated corresponding to the beam trace state and radially rotates the objective lens of the optical pickup by driving a tracking actuator in the optical pickup according to the tracking error signal. Direction to correct the position of the beam and follow a predetermined track.

At this time, even if the tracking error signal is zero, a detrack may occur in which the optical focus is shifted from the track center. This detrack was not a problem in the CD world.

However, in an optical disc capable of recording and reproducing data in both land and groove, such as a DVD-RAM, the track pitch is narrow for high density, and such detracking has a great effect on the next track.

In addition, even if the tracking is correct in the track of the land by the depth difference between the land and the groove, if it is applied to the track of the groove as it is, the groove may not be on-track. That is, detracking may occur. Similarly, when tracking is tracked on the groove track, detrack may occur in the track of the land due to the depth difference between the land and the groove.

Therefore, in such a detrack state, since the beam easily passes to the adjacent track, crosstalk is generated a lot, and data recording / reproducing, such as erasing the data of the adjacent track, becomes difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to detect a detrack from a potential difference between a wobble signal recorded on a track and a read channel 2 signal detected in the VFO1 and VFO3 areas in the header area. The present invention provides a method of recording and reproducing an optical recording medium to compensate.

1 shows the arrangement of a header preformatted at the start of each sector in a typical rewritable disc.

2 is a block diagram of an optical disk recording / reproducing apparatus for detrack control according to the present invention;

3 is a diagram illustrating an example of a light detector of the optical pickup of FIG. 2;

4 is a graph showing examples of the read channel 2 signals detected in the VFO1 and VFO3 areas in the header area due to the change of the detrack offset.

5A to 5C show examples of the potential difference between the read channel 2 signal and the wobble signal detected in the VFO1 and VFO3 areas in the header area due to the detrack offset change.

Explanation of symbols for main parts of the drawings

201: optical disc 202: optical pickup

203: error signal generation unit 204: detrack detection unit

205: servo control unit 206: tracking drive unit

According to an aspect of the present invention, there is provided a method of recording and reproducing an optical recording medium, wherein the shape of the data area is divided between recordable data areas in which information capable of recognizing a reference frequency is wobbling on a track. A plurality of sections having different phases are arranged for each other, and in each section, a wobble signal of the data area is detected when recording and reproducing a disc that is continuously present by repeatedly alternating non-recording areas having position information in the disk of the data area. Obtaining a difference between the wobble signal and a signal detected in the non-recorded area and outputting the difference as a first difference signal, and detecting the wobble signal in a non-recorded area having a phase different from that of the wobble signal and the non-recorded area. Obtaining a difference between the signal and outputting it as a first difference signal, and between each first difference signal of the steps Obtaining a second difference signal, determining that the second difference signal exceeds a predetermined reference value, outputting a result value, and performing a tracking servo from the result value. .

The step of obtaining the difference signal is characterized by using only a portion of the non-recorded area.

The step of obtaining the difference signal is characterized by using the VFO area of the non-recorded area.

The obtaining of the difference signal may include using a read channel 2 signal generated from an electrical signal output in proportion to the amount of light reflected from the optical recording medium.

The potential of the wobble signal in the step of obtaining the difference signal is characterized in that the center voltage of the wobble signal detected from the read channel 2 signal.

In the detrack detection step, if the second difference signal does not exceed a predetermined reference value, it is determined as a track center and outputs a result value.

In the performing of the tracking servo, the detrack size is detected from the value of the second difference signal.

In the performing of the tracking servo, the detrack direction is detected from the sign of the second difference signal.

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

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

The present invention compares the potential difference between the wobble center of lead channel 2 and the VFO1,3 signals in the header region in a system where the headers are staggered from the track center to detect the detrack size and direction to compensate for the detrack.

FIG. 2 is a block diagram illustrating an optical disc recording / reproducing apparatus for performing the detrack control method according to the present invention, and shows only a portion related to the detrack.

2, an optical disk 201 capable of rewriting data, an optical pickup 202 for recording and reproducing information on the optical disk 201, an RF signal from an electrical signal output from the optical pickup 202, and the like. An error signal generator 203 for generating a servo error signal, a detrack detector 204 for detecting the magnitude and direction of the detrack from the read channel 2 signal of the error signal generator 203, and the detrack detector 204 Servo control unit 205 for generating a tracking drive signal from the size and direction of the detrack detected by the control unit, and a tracking driver 206 for controlling the optical pickup 202 according to the tracking drive signal to compensate for the detrack. do.

Here, the optical pickup 201 is provided with a photo detector for detecting the light amount of the beam and converting it into an electrical signal, the optical detector is an example of the signal track direction and the radial direction of the optical disk 201 as shown in FIG. In this case, it is possible to configure four specific photodetectors (PDA, PDB, PDC, PDD).

In the present invention configured as described above, the optical disc 201 has a signal track having a structure of lands and grooves, and data can be recorded or reproduced not only on the tracks of the lands or grooves, but also on the tracks of the lands and grooves. have.

In addition, wobble signals of a predetermined frequency are recorded on tracks of the sectors of the land and the grooves, for example, at the interface, and preformats in which the header 1, 2 fields and the header 3, 4 fields are alternately arranged at the start positions of the sectors are shown. It is arranged. In other words, the phases of the header 1,2 fields are reversed to the header 3,4 fields.

Thus, the laser light emitted by the laser diode of the optical pickup 202 during mounting or recording / reproducing of the optical disk 201 is placed on the signal track of the rotating optical disk 201, where the reflected light is directed to the optical detector. Incident.

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 error signal generator 203.

If the photo detector is configured in a one-beam system as shown in FIG. 3, the photo detector generates an error signal by generating electrical signals a, b, c, and d in proportion to the amount of light obtained from each of the photo detector elements PDA, PDB, PDC, PDD. Output to the unit 203.

The error signal generator 203 combines the electrical signals a, b, c, and d to read-read channel 1 signals (or RF signals) for data reproduction and read-channel 2 signals for servo control. To generate a focus error signal. Here, the read channel 2 signal may be obtained by (a + d)-(b + c) the electrical signal output from the photo detector, and the tracking error signal may be obtained by processing the read channel 2 signal.

If the photodetector is divided into two in the signal track direction, the read channel 2 signals I1 to I2 are detected from the light quantity balance of both photodiodes I1 and I2. That is, a + d in FIG. 3 corresponds to I1 and b + c corresponds to I2.

At this time, the wobble signal recorded on each track is detected only in the read channel 2 as shown in FIG.

Therefore, the present invention detects the detrack by using the difference between the VFO1, VFO3 signal level and the wobble level in the header region of read channel 2. FIG. Here, the signals of the VFO1 and VFO3 regions are used because the VFO1 and VFO3 regions are the longest, stable and easy to detect.

To this end, the read channel 2 signal among the error signals detected by the error signal generator 203 is input to the detrack detector 204.

At this time, the magnitudes of the VFO1 and VFO3 signals of the read channel 2 due to the change of the detrack offset in the focus-on and tracking-on states are insignificant as shown in Table 1 below.

Detrack [] VFO1 [V] VFO3 [V] 0.00 0.201 0.183 1.00 0.187 0.194 2.00 0.183 0.190 3.00 0.192 0.185 4.00 0.183 0.197 5.00 0.183 0.201 6.00 0.187 0.206 7.00 0.185 0.185 8.00 0.176 0.181 9.00 0.169 0.178 10.00 0.160 0.171

4 is a graph representing Table 1, VFO1-VFO3 ?? At zero, the magnitudes of the two signals are nearly constant.

That is, even if you move the track center, for example,_k- ≤ VFO1 + VFO3 ≤ V_{k +} Is constant.

However, as shown in FIGS. 5A to 5C, it can be seen that the center of the wobble signal (hereinafter, referred to as wobble center) is shifted up and down by the detrack offset change.

Therefore, when the potential difference between the wobble center of the read channel 2 and the VFO1 signal (VFO1 potential-wobble center potential = Vpp1) and the potential difference between the wobble center and the VFO3 signal (VFO3 potential-wobble center potential = Vpp2) are compared, (= Size) and direction are known.

That is, FIGS. 5A to 5C are examples of the read channel 2 signal detected while only changing the track offset value after track on and focus on in the tilt 0 (= mechanism 0) state. 5A to 5C, the signal appearing on the upper left side is the lead channel 2 signal detected in the VFO area of the header 1,2 fields, and the signal appearing on the lower right side in the reverse phase is detected in the VFO area of the header 3,4 fields. Read channel 2 signal.

At this time, since the wobble center changes according to the detrack offset and thus the voltage V _WC detected at the wobble center changes, the voltages detected at VFO1 and VFO3 become reference levels.

Here, when there is no detrack, that is, when the optical focus is well-suited to the track center, the potential difference between the wobble center and the VFO1 signal (Vpp1 = V _VFO1 -V _WC ) and the potential difference between the wobble center and the VFO3 signal (Vpp2 = V _VFO3 -V _WC ) are almost the same as in FIG. 5B.

This is expressed by the following equation (1).

In this case, the V _VFO1 / V _VFO3 is obtained by holding the peak and bottom of the VFO1 / VFO3 signal, respectively, and can be compared with the wobble center voltage, or obtained by holding the center of the VFO1 / VFO3 signal You can also compare with voltage.

According to the present invention, when the potential difference Vpp1 between the VFO1 signal and the wobble center and the potential difference Vpp2 between the VFO2 signal and the wobble center are different, that is, the difference between two potential differences (= Vpp1-Vpp2) is constant as shown in Equation 2 of the semester. If it exceeds the reference value (V _Th1 ), it is determined that a detrack has occurred, and if it does not exceed a certain reference value (V _Th1 ), the optical focus is determined to be an on-track that fits well with the track center.

Vpp1-Vpp2 ≤ V _Th1

When Equation 2 is normalized, the following Equation 3 is obtained.

In addition, when it is determined that the difference between the two potential differences Vpp1 and Vpp2 is greater than the predetermined reference value V _Th1 , the detrack has occurred, the magnitude of the detrack can be known by the difference between the two potential differences, The sign indicates the direction of the detrack.

If the value of Vpp1-Vpp2 is α, and α is larger than V _Th1 , the magnitude of the detrack can be determined by the α value, and the direction of the detrack can be known by the sign of α.

Therefore, if the sign of α is-, the detrack may be compensated by α in the + direction, and if the sign of α is +, the detrack may be compensated by α in the-direction. That is, the detrack may be compensated in a direction in which the magnitudes of the two potential differences Vpp1 and Vpp2 are the same.

To this end, the detrack detection unit 204 outputs a detrack error signal corresponding to α and a direction corresponding to a sign to the servo control unit 205, and the servo control unit 205 outputs the detrack error signal. The signal is converted into a tracking driving signal by signal processing and output to the tracking driving unit 206.

The tracking driver 206 drives the tracking actuator of the optical pickup 202 and the disk 201 by driving the tracking actuator in the optical pickup 202 according to the tracking drive signal, that is, in the + or-direction by the size of the detrack. Control it to match.

As described above, according to the recording and reproducing method of the optical recording medium according to the present invention, the lead channel 2 signals detected in the VFO1 and VFO3 regions of the header regions that are staggered from the track center and whose phases are different from each other according to the degree of detrack Since the size of the wobble center changes while the magnitude is constant, the potential difference between the wobble center and the VFO1 signal and the potential difference between the wobble center and the VFO3 signal are compared to detect the size and direction of the detrack, and then compensate for the detrack, thereby recording and playing back. It prevents the quality of data due to CD tracks and operates the system stably.

Claims (9)

A plurality of sections having different phases are arranged between the recordable data areas in which information capable of recognizing a reference frequency is wobbed on the track to distinguish the shape of the data areas, and each section includes a plurality of sections within the disk of the data area. A method of recording and reproducing a disc in which non-recorded areas having positional information are alternately alternately present continuously, Detecting a wobble signal in the data area; Obtaining a difference between the wobble signal and a signal detected in the non-recorded area and outputting the difference as a first difference signal; Obtaining a difference between the wobble signal and a signal detected in a non-recorded region having a phase different from that of the non-recorded region and outputting the difference as a first difference signal; Obtaining a second difference signal between each first difference signal of the steps; Determining that the second difference signal exceeds a predetermined reference value as a detrack and outputting a result value; And performing a tracking servo from the resultant value. The method of claim 1, Obtaining the difference signal And using only a portion of the non-recorded area. The method of claim 1, Obtaining the difference signal And a variable frequency oscillator (VFO) area of the non-recorded area. The method of claim 1, Obtaining the difference signal And a read channel 2 signal generated from an electrical signal output in proportion to the amount of light reflected from the optical recording medium. The method of claim 4, wherein Obtaining the difference signal And a center voltage of the wobble signal detected from the read channel 2 signal. The method of claim 1, The detrack detection step is And if the second difference signal does not exceed a predetermined reference value, the optical focus is determined to be on-track at the track center and the resultant value is output. The method of claim 1, The tracking servo performing step And detecting the detrack size from the result of the second difference signal. The method of claim 1, The tracking servo performing step And detecting the detrack direction from the sign of the second difference signal. The method of claim 1, The tracking servo performing step And compensating for the detrack in the direction in which the magnitudes of the first difference signals obtained in the above steps become equal.