KR20010057845A - Method for recording/playing of optical recording medium - Google Patents

Abstract

PURPOSE: A recording/reproducing method of optical recording media is provided to improve both recording and reproducing quality by using optimal focus offset and optimal track center detected from wobble signal previously for normal reproduction. CONSTITUTION: A BPF(203) detects wobble signal making a band pass filtering lead channel 2 signal generated from RF and servo error generating part(204). A wobble Vpp(peak to peak voltage) detecting part(205) detects voltage level of wobble signal which is output from the BFP(203) A servo control part(206) gets optimal focus offset and track center value for each land/groove using voltage level of wobble signal and land/groove switching signal detected at the wobble Vpp detecting part(205). A focus servo driving part(207) generates focus driving signal using signal of sum of focus error signal and offset signal which is output from the servo control part(206). A tracking servo driving part(208) generates tracking driving signal for turning on tracking based on track center which is output from the servo control part(207).

Description

Recording and playback method of optical recording medium {Method for recording / playing of optical recording medium}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a repeatable rewritable optical recording medium system, and more particularly to a method for controlling an optical recording medium having a wobble structure.

In general, a freely rewritable optical recording medium such as an optical disc may include a rewritable compact disc (CD-RW) and a rewritable digital versatile disc (DVD-RW, DVD-RAM). Etc.

The above-described rewritable optical disc, especially 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.

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 a sector for each sector, or may be recorded in a wobbling shape along the track. That is, wobbling means that address information is recorded on the track boundary using a constant frequency or frequency modulation / phase modulation (FM / PM) in order to increase the degree of address recording or control.

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

Fig. 1 is a general block diagram of such an optical disc recording / reproducing apparatus. In the optical disc 101, signal tracks have a structure of lands and grooves, and data is stored not only on tracks of lands or grooves, but also on tracks of lands and grooves. Can be recorded or played back.

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 disk 101 under the control of the servo control unit 106, and also 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 104.

The RF and servo error generator 104 combines the electrical signals to generate an RF signal for data reproduction, a tracking error signal TE for servo control, a focus error signal FE, and the like.

At this time, the RF signal is output to the decoder 105 for reproduction, servo error signals such as FE and TE are output to the servo controller 106, and a control signal for data recording is output to the encoder 103.

The encoder 103 encodes data to be recorded into recording pulses in a format required by the optical disk 101, and then records the data on the optical disk 101 through the optical pickup 102, and the decoder 105 transmits the RF. Restore the original form of data from the signal.

On the other hand, a host such as a PC may be connected to the optical disc recording and reproducing apparatus, and the host transmits a recording / playback command to the microcomputer 111 through the interface 110, and records to the encoder 103. The data is transmitted, and the reproduced data is transmitted from the decoder 105. The microcomputer 111 controls the encoder 103, the decoder 105, and the servo controller 106 according to a recording / reproducing command of the host.

In this case, the interface 110 generally uses an advanced technology attached packet interface (ATAPI). In other words, ATAPI is an interface standard between an optical recording / playback device such as a CD or DVD drive and a host, and it is a standard proposed to transmit data decoded by an optical recording / playback device to a host. It converts the protocol into an in-packet form and transmits it.

The servo controller 106 processes the focus error signal FE to output a driving signal for focusing control to the focus servo driver 107, and processes the tracking error signal TE to signal the tracking control. The driving signal is output to the tracking servo driver 108.

The focus servo driver 107 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 108 modifies the position of the beam by moving the objective lens of the optical pickup 102 in the radial direction by driving the tracking actuator in the optical pickup 102, and follows a predetermined track.

At this time, focus control must be performed even in an abnormal state in which the tracking servo is turned off, for example, in a free running or traverse state.

Here, the traverse state means detecting the servo error signal while rotating the disc and moving the optical pickup while the tracking servo is turned off and only the focus servo is turned on, and is mainly used for seek such as track jump and free. The free running state means detecting the servo error signal with the tracking servo off and the focus servo on, with the disc rotating and the optical pickup fixed. It is used to measure Shenyang.

At this time, the focus servo sets a rough constant value in advance and performs a focus search so that the distance between the objective lens and the optical disk falls within the depth of focus. That is, the focus offset is adjusted by detecting and compensating for an error between the DC level of the focus error signal generated from the optical pickup during focus search and the reference voltage used for control. Alternatively, the focus offset may be adjusted in a direction in which RF is greatly emitted.

However, in the case of the land / groove recording method, offsets may appear differently depending on the depth difference between the land and the groove. Therefore, if the above method is applied as it is, it greatly affects the recording quality at the time of recording. In addition, it plays a role in increasing reproduction jitter by affecting RF reproduction quality during reproduction.

On the other hand, the tracking servo estimates the track error center value at the time of free running and uses it as the track center value. In other words, the error value for the estimated track error center is represented by the DC-offset of the tracking error. However, if the optical detector or the like is optically wrong, the tracking error signal may occur asymmetrically, in which case the track error center is not the actual track center and the other point is the track center.

Therefore, there is a risk of starting control when the optical head is excessively out of track when starting tracking servo using the track error center value. In this case, initial stable tracking performance cannot be secured due to the transient response due to excessive tracking error. Therefore, the track center value must be accurate to set the appropriate tracking servo start time. In particular, if the tracking is turned on at a location other than the track center, recording is performed at the wrong position, so that the RF signal is smaller, the jitter characteristic is degraded, and in particular, the recording characteristic is further degraded.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an optimal focus offset and track center value in advance by using a wobble signal during free running or traverse instead of normal playback in a land / groove recording method. The present invention provides a recording and reproducing method of an optical recording medium used for reproduction.

1 is a block diagram of a general optical disc recorder

2 is a block diagram of an optical record player for recording and reproducing an optical record carrier according to the present invention;

3A is a waveform diagram of a tracking error signal.

3B is a waveform diagram of a wobble signal

Explanation of symbols for main parts of the drawings

101: optical disk 102: optical pickup

103: encoder 104,204: RF and servo error generation unit

105: data decoder 106,206: servo control unit

107,207: focus servo driver 108,208: tracking servo driver

203: BPF 205: Wobble Vpp detection unit

In the recording and reproducing method of the optical recording medium according to the present invention for achieving the above object, a wobble signal formed by the optical recording medium is wobbling on the track of the recordable data area when the recording and reproduction in the normal state is not performed And detecting the focus offset and track center which are control information from the detected voltage level of the wobble signal, and using the focus offset and tracking error center for recording and reproduction in the normal state. It is done.

The obtaining of the control information may include determining a position where the voltage level of the wobble signal becomes maximum as a focus offset.

The obtaining of the control information may include determining, as a track center, a position at which the voltage level of the wobble signal becomes maximum.

The normal recording and reproducing step is characterized by generating a focus driving signal for driving a focus actuator by adding the determined focus offset to a focus error signal detected from an electrical signal proportional to the amount of light.

The normal recording and reproducing step is characterized in that the tracking servo is turned on at the track center.

The present invention is to detect an optimum focus offset and an optimum track center before starting normal playback in an optical disc having a land / groove recording method and a wobble structure.

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.

FIG. 2 is a block diagram of an optical recording / reproducing apparatus for performing a recording / reproducing method of an optical recording medium according to the present invention. The wobble signal is obtained by band-pass filtering the read channel 2 signal generated by the RF and servo error generation unit 204. FIG. The voltage level and the land / groove of the wobble signal detected by the BPF 203, the wobble Vpp detector 205 for detecting the voltage level of the wobble signal output from the BPF 203, and the wobble Vpp detector 205 The servo control unit 206 obtains an optimal focus offset and track center value for each land / groove using a switching signal, and focus driving using a sum signal of the focus error signal and the offset signal output from the servo control unit 206. Focus servo driver 207 for generating a signal, and tracking for generating a tracking drive signal for turning on the tracking based on the track center output from the servo controller 207. The servo driver 208 is configured.

According to the present invention configured as described above, the optimum focus offset and track center are obtained for the land and the groove, respectively, using the voltage level of the wobble signal obtained during free running or traverse after focus on.

To this end, when the read channel 2 signal obtained by the RF and servo error generator 204 passes through the BPF 203, only the wobble signal is output to the wobble Vpp detector 205 as shown in FIG. This is because the BPF 203 only passes a region corresponding to the wobble frequency. The wobble Vpp detector 205 detects a voltage level (Vpp; peak to peak voltage) of the wobble signal as shown in FIG. The voltage level can be detected by holding the top and bottom of the wobble signal. Processing the read channel 2 signal results in a tracking error signal as shown in FIG. At this time, the wobble signal recorded on each track is detected only in the read channel 2.

At this time, the voltage level of the wobble signal has the highest value when the focus is best. This means that when the voltage level of the wobble signal is the largest, that is, the maximum, is in the positive focus state. Also, the track center is when the wobble signal has the highest voltage level.

Accordingly, the servo controller 206 adjusts the focus offset while comparing the voltage level of the wobble signal, and determines the final focus offset when the voltage level of the wobble signal has the largest value. This process is performed for each groove track and land track to determine the final groove and land focus offset. For example, if the target is placed on the groove track, it is a groove offset, and if it is placed on the land track, it is a land track offset, which is indicated by the land / groove switching signal.

Further, when the voltage level of the wobble signal becomes maximum in each of the groove track and the land track, the track center of the final groove and land track is determined. In particular, an accurate track center level can be obtained by averaging the tracking error values taken at the instant of the maximum voltage level of the wobble signal. For example, the detection accuracy can be improved by averaging the maximum value of the wobble signal detected within one period of tracking zero cross (TZC) during free running.

Then, the focus servo and the tracking servo may be performed by using the above described focus offset and track center during normal reproduction.

That is, the servo controller 206 adds the determined focus offset to the focus error driver 207 by adding the focus error signal output from the RF and the servo error generator 204, and the track center value is the tracking servo driver 208. )

The focus servo driver 207 maintains a constant distance between the objective lens and the optical disk by driving the focus actuator in the optical pickup with a focus drive signal corresponding to a signal amount of a focus error signal plus a focus offset.

That is, since the DC offset is different between the land and the groove, the optimum focus offset is determined from the change of the wobble signal while switching the land and the groove before the normal recording and reproduction, and the normal is added to the original focus error signal amount detected from the focus error signal. By performing the focus servo at the time of recording reproduction, a more accurate focus servo is performed.

In addition, the tracking servo driver 208 uses the track center value as the starting point of the tracking servo when the tracking servo is turned on after free running or traverse ends. That is, since the instant of the maximum value of the wobble signal is the point at which the optical head passes through the center of the track, the operation of the tracking servo driver 206 at the maximum value of the wobble signal obtains a relatively small transient response characteristic, thereby providing stable initial control performance. You can get it.

In particular, when the tracking error signal occurs asymmetrically because the optical detector or the like is optically wrong, the maximum position of the wobble signal becomes the actual track center.

At this time, in order to remove the influence of the header, the header area is masked using the header window signal. That is, since the wobble signal is not recorded in the header area, the signal detected in the header window is ignored.

As described above, according to the recording and reproducing method of the optical recording medium according to the present invention, the optimum focus offset and the optimum track center are detected in advance from the wobble signal before starting normal playback on an optical disc having a wobble structure and a land / groove recording method. Then, by using it for normal reproduction, the optimal recording and reproduction is performed by improving the recording and reproduction quality in the land / groove recording method in which offsets are different from each other due to the depth difference between the land and the groove. In addition, since the tracking servo is turned on at the actual track center position, initial stable tracking performance can be ensured.

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 (8)

A recording and reproducing method of an optical recording medium for performing focus control and tracking control by detecting a focus error signal and a tracking error signal from an electrical signal proportional to an amount of light output from an optical pickup. Detecting a wobble signal formed by the optical recording medium being wobbled on a track of a recordable data area at a time point when recording and reproduction in a normal state is not performed; Obtaining a focus offset and a track center as control information from the detected voltage level of the wobble signal; And using the focus offset and track center for recording and reproducing in a normal state. The method of claim 1, wherein the obtaining of the control information And a focus offset determining a position at which the voltage level of the wobble signal is maximized as a focus offset. The method of claim 1, wherein the obtaining of the control information And focusing the land and the groove tracks respectively to determine the position where the voltage level of the wobble signal is maximized as the focus offset of the land and the groove tracks, respectively. The method of claim 1, wherein the obtaining of the control information And a track center determines a position at which the voltage level of the wobble signal is maximized as a track center. The method of claim 4, wherein the obtaining of the control information And focusing the land and the groove tracks respectively to determine the position at which the voltage level of the wobble signal is maximized as the track center of the land and groove tracks, respectively. 2. The normal recording and reproducing step according to claim 1, wherein And a focus drive signal for driving a focus actuator by adding the determined focus offset to a focus error signal detected from an electrical signal proportional to the amount of light. 2. The normal recording and reproducing step according to claim 1, wherein And a tracking servo is turned on at the track center. The method of claim 1, wherein the obtaining of the control information When a plurality of non-recorded areas having different phases are disposed between the recordable data areas to distinguish the shape of the data area, signals detected in the plurality of non-recorded areas are not used for focus offset and track center determination. Recording and reproducing method of an optical recording medium.