JP2001176071A - Optical recording and reproducing method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording and reproducing method and its device by which a multi-level recording with high precision can be attained with a simple configuration. SOLUTION: Wobble grooves 11 are formed in an optical disk recording medium as a guide groove. A reference clock is generated from a wobble signal which is obtained from a light reflection signal by the wobble groove and the light emission timing of a laser is controlled to change the shift amount of each recording mark position concerning the leading edge of the reference clock in accordance with multi-level recording data. At the reproduction of data recorded by a multi-level, the peak level position of an MO signal obtained by reproducing a recording mark is detected and multi-level data are discriminated on the basis of the phase difference between the leading edge of the reference clock and the peak level position of the MO signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing method and apparatus using an optical disk recording medium, and more particularly to an optical recording / reproducing method for performing multi-level recording by shifting the position of a recording mark according to recording data. Related to the device. The optical disk recording medium referred to here includes a so-called phase-change type optical disk and an optical modulation type or magnetic field modulation type magneto-optical disk. Accordingly, the optical recording / reproducing method and apparatus include not only phase-change optical recording / reproducing but also magneto-optical recording / reproducing.

[0002]

2. Description of the Related Art In recent years, optical disk recording media have been required to have higher capacities and higher densities. As one method for realizing higher capacity and higher density of an optical disc recording medium,
There is a multi-value record. Multi-level recording means that information is recorded / reproduced in association with three or more values, and is distinguished from binary recording in which recording / reproduction is performed in correspondence with a binary value of “0” or “1”. Is the concept of

The details of multi-value recording are described in, for example, Japanese Patent Application Laid-Open No. 6-76399. In this conventional example, in a mark edge type recording / reproducing method, multi-value information is recorded by shifting the edge position of a recording mark stepwise from a reference position in correspondence with recording data.

FIG. 3 shows the principle of multi-value recording in the above conventional example. In this conventional example, a fixed time (T / 2)
This is a magnetic field modulation type magneto-optical disk drive that records a recording mark by applying an external magnetic field whose polarity is inverted every time and irradiating a pulse with laser light. A reference clock (period T) is generated from a reproduction signal corresponding to prepits formed at regular intervals on the optical disc recording medium. The edges of the recording mark are set in steps (t = t0, t1, t2, t3) with reference to, for example, the rising edge of the reference clock.
To perform multi-value recording. At the time of reproduction, the reproduction signal is sampled by the reference clock, and the multilevel information is read by detecting the level.

In the above-described multi-level recording of the mark edge method,
The greater the number of shifts (the number of stages) of the edge position, the more advantageous in increasing the number of values, that is, increasing the density. However, in order to increase the number of shifts of the edge position with respect to the limited reference clock cycle, it is necessary to precisely control the formation of the edge. On the other hand, it is not easy to control the edge position of a recording mark formed by laser light irradiation.

Another conventional example is disclosed in Japanese Patent Application Laid-Open No. 8-28746.
The optical recording / reproducing method described in Japanese Patent Publication No. 8 realizes multi-value recording by a pit position method instead of the mark edge method as in the above-described conventional example. In this case, multi-level recording is performed by shifting the center position of the recording mark stepwise with respect to the edge of the reference clock. Therefore, problems such as the difficulty in controlling the edge position described above do not occur.

[0007]

However, even in the recording / reproducing method disclosed in JP-A-8-287468, the frequency of a reproduction signal corresponding to prepits formed at regular intervals on an optical disk recording medium is multiplied. Generating reference clock. Therefore, the phase relationship between the reference clock and the recording mark can be accurately controlled in the vicinity where the pre-pit for generating the reference clock is formed, but the phase relationship between the reference clock and the recording mark increases as the distance from the pre-pit increases. However, there is a problem that the accuracy of the image is deteriorated.

Accordingly, an object of the present invention is to solve the above-mentioned conventional problems and to provide an optical recording / reproducing method and apparatus which enable highly accurate multi-value recording with a simple configuration.

[0009]

According to an optical recording / reproducing method of the present invention, a guide groove formed on an optical disk recording medium is a wobble groove, and a reference clock is generated from a wobble signal obtained from a light reflected signal by the wobble groove. And recording and reproducing information on and from the optical disk recording medium by associating a phase difference between the reference clock and each recording mark with multi-valued information.

Further, the first aspect of the optical recording / reproducing apparatus according to the present invention.
The optical disk recording medium in which a wobble groove as a guide groove is formed; irradiating the optical disk recording medium with laser light; receiving reflected light reflected by the optical disk recording medium; An optical head that generates and outputs a wobble signal corresponding to a groove, a clock generation circuit that generates a reference clock from the wobble signal, and shifts the position of each recording mark with respect to the reference clock in multiple steps according to recording data. And a multi-value recording means for performing multi-value recording.

Preferably, the multi-level recording means generates a phase modulation signal from the reference clock and the recording data and outputs the phase modulation signal, and emits a pulse of light from the laser of the optical head according to the phase modulation signal. And a laser drive circuit for causing the

The second aspect of the optical recording / reproducing apparatus according to the present invention is as follows.
The wobble groove is formed as a guide groove, and the recording mark is recorded along the wobble groove in a multi-level recording by a pit position method, and the optical disk recording medium is irradiated with laser light. An optical head that receives light reflected by the optical disk recording medium, generates and outputs a wobble signal corresponding to the wobble groove and a reproduction data signal corresponding to the recording mark from a received light signal, and A clock generation circuit for generating a reference clock; and a multi-valued data reproducing means for generating and outputting multi-valued data based on a phase relationship between the reproduced data signal and the reference clock.

Preferably, the multi-value data reproducing means includes:
A signal processing circuit for detecting a peak level position of the reproduction signal; a data detection circuit for detecting a phase difference between the peak level position and an edge of a reference clock; and a demodulation circuit for demodulating and outputting reproduction data according to the phase difference. And

According to the optical recording / reproducing apparatus and method described above, a signal frequency obtained from a clock pit formed at predetermined intervals on a conventional optical disk recording medium is multiplied to generate a clock signal. By using a wobble signal obtained from a continuously formed wobble groove, a highly accurate reference clock can be obtained. Therefore, the phase relationship between the reference clock and the recording mark can be controlled more precisely than before, which contributes to further multi-value, that is, higher density.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the shapes of recording tracks (recording marks and guide grooves) of an optical disk recording medium used in an optical recording / reproducing apparatus according to an embodiment of the present invention, and each shape including a wobble signal (push-pull signal) obtained from the guide grooves. 3 shows a signal waveform. FIG. 2 is a block diagram showing the configuration of the optical recording / reproducing apparatus.

In FIG. 2, reference numeral 21 denotes an optical disk recording medium, and reference numeral 22 denotes an optical head which irradiates a laser beam onto the optical disk recording medium 21 and receives reflected light from the optical disk recording medium 21 and converts the reflected light into an electric signal. . The electric signal output from the optical head 22 includes a wobble signal (push-pull signal) obtained from the guide groove and an MO signal obtained from a recording mark.

The optical disk recording medium 21 used in the optical recording / reproducing method and apparatus of the present invention has a guide groove (ie, a wobble groove) meandering at a constant period as shown in FIG.
11 are formed. Then, a recording mark 12 is recorded in the guide groove 11 by pit position recording. The recording position of each recording mark 12 can be displaced in four steps as shown by a solid line and a broken line, thereby realizing 2-bit multi-value recording.

A clock serving as a reference for the recording position of each recording mark 12 is generated from a wobble signal (push-pull signal) obtained from a wobble groove (guide groove) 11. FIG.
If the guide groove 11 is meandering as shown in FIG.
A wobble signal as shown in FIG. The push-pull signal is a signal conventionally used for tracking servo. In the present invention, a reference clock (period T) for multi-value recording as shown in FIG.

The clock generation circuit 23 shown in FIG. 2 manages the generation of the reference clock. That is, the clock generation circuit 23
Is input to the clock generation circuit 2
The signal is amplified by the amplifier in 3, and is input to the PLL circuit through signal processing by an equalizer and a shaper, and a reference clock is generated. Since the process of such signal processing is well known, a detailed description is omitted. By using a wobble signal obtained from a continuously formed wobble groove as compared with a case where a signal frequency obtained from a clock pit formed at a predetermined interval on a conventional optical disk recording medium is multiplied to generate a clock signal. , A highly accurate reference clock can be obtained.

In the pit position recording according to the present embodiment, the recording marks 12 are recorded in accordance with the recording data.
The pulse of the laser of the optical head 22 is emitted at a timing corresponding to the position. That is, the phase modulation circuit 24 of FIG.
Performs phase modulation in accordance with the input reference clock and the recording data, and supplies a modulation signal including mark position information corresponding to the recording data to the laser driving circuit 25. The laser drive circuit 25 causes the laser of the optical head 22 to emit pulse light according to the applied modulation signal.

In this way, the recording position of each recording mark is displaced in four steps according to the recording data. In the example shown in FIG. 1, the center position of the recording mark can be shifted in four steps with reference to the rising edge of the reference clock. The center of the recording mark at the head position (shift amount is zero) of the four stages coincides with the rising edge of the reference clock.

A process for reading data from the optical disk recording medium 21 on which data (recording marks) are recorded as described above will be described below. When a low-power laser beam for reproduction is irradiated from the optical head 22 onto the optical disk recording medium 21 and the reflected light is received by the optical head 22, the wobble corresponding to the wobble groove (guide groove) 11 is transmitted from the optical head 22. The signal (push-pull signal) and the MO signal (FIG. 1) which is a reproduced data signal corresponding to the recording mark 12
(See (d)). The wobble signal (push-pull signal) is input to the clock generation circuit 23 and a reference clock is output, similarly to the above-described operation at the time of recording.

The MO signal is a pulse signal having a peak position at the center position of the recording mark 12, as shown in FIG. Therefore, by detecting the peak level position (phase with respect to the reference clock) of the MO signal, it is possible to determine which of the four types of data the recording mark is. The signal processing circuit 26, the data detection circuit 27, and the demodulation circuit 28 perform this processing.

The MO signal output from the optical head 22 is input to a signal processing circuit 26. The signal processing circuit 26
A differentiated signal obtained by differentiating the MO signal (FIG. 1 (e)
See). As can be seen from FIGS. 1D and 1E, the zero cross point of the differential signal coincides with the peak level position of the MO signal. The signal processing circuit 26 further generates a mark position detection signal as shown in FIG. 4F from the differential signal, and outputs the signal to the data detection circuit 27. This mark position detection signal is a rectangular wave signal rising from the zero cross point of the differential signal.

The data detection circuit 27 detects a phase difference (shift amount) between the rising phase of the reference clock supplied from the clock generation circuit 23 and the rising phase of the mark position detection signal, and outputs it to the demodulation circuit 28. This shift amount corresponds to four types (two bits) of information of each recording mark. The demodulation circuit 28 demodulates according to the shift amount and outputs reproduced data.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and can be implemented in various forms. For example, in the above embodiment, the guide groove (wobble groove) formed on the optical disk recording medium is meandering on both sides so that the width is constant, but the guide groove does not necessarily need to have a constant width. The wobble groove may be formed by meandering only one side of the guide groove at a constant period. Also,
The present invention is not limited to magneto-optical recording as in the above embodiment,
It can also be applied to phase-change type optical recording.

[0027]

As described above, according to the optical recording / reproducing apparatus and apparatus of the present invention, the clock frequency is obtained by multiplying the signal frequency obtained from the clock pit formed at a predetermined interval on the conventional optical disk recording medium. By using a wobble signal obtained from a continuously formed wobble groove, a highly accurate reference clock can be obtained as compared with a case where a signal is generated. Therefore, the phase relationship between the reference clock and the recording mark can be controlled more precisely than before, which contributes to further multi-value, that is, higher density.

[Brief description of the drawings]

FIG. 1 is a diagram showing a shape of a recording track of an optical disc recording medium used in an optical recording / reproducing apparatus according to an embodiment of the present invention, and a waveform of each signal including a wobble signal.

FIG. 2 is a block diagram illustrating a configuration of an optical recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing the principle of multi-level recording in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Guide groove (wobble groove) 12 Recording mark 21 Optical disk recording medium 22 Optical head 23 Clock generation circuit 24 Phase modulation circuit 25 Laser drive circuit 26 Signal processing circuit 27 Data detection circuit 28 Demodulation circuit

Claims (5)

[Claims] A guide groove formed in an optical disk recording medium is a wobble groove, a reference clock is generated from a wobble signal obtained from a light reflection signal from the wobble groove, and a phase difference between the reference clock and each recording mark is determined. An optical recording / reproducing method, wherein information is recorded / reproduced on / from the optical disc recording medium in association with multi-valued information. 2. An optical disk recording medium in which a wobble groove as a guide groove is formed; and irradiating the optical disk recording medium with laser light.
Receiving the reflected light reflected by the optical disk recording medium,
An optical head that generates and outputs a wobble signal corresponding to the wobble groove from a light receiving signal, a clock generation circuit that generates a reference clock from the wobble signal, and a position of each recording mark with respect to the reference clock according to recording data. An optical recording / reproducing apparatus comprising: a multi-level recording means for performing multi-level recording by shifting in multiple stages. 3. The multi-level recording means generates a phase modulation signal from the reference clock and the recording data and outputs the phase modulation signal, and causes the laser of the optical head to emit a pulse according to the phase modulation signal. 3. The optical recording and reproducing apparatus according to claim 2, further comprising a laser driving circuit. 4. An optical disk recording medium in which a wobble groove is formed as a guide groove, and a recording mark is recorded along the wobble groove by a pit position method in a multi-valued manner. The optical disk recording medium is irradiated with laser light.
Receiving the reflected light reflected by the optical disk recording medium,
An optical head for respectively generating and outputting a wobble signal corresponding to the wobble groove and a reproduction data signal corresponding to the recording mark from a light receiving signal; a clock generation circuit for generating a reference clock from the wobble signal; An optical recording / reproducing apparatus comprising: a multi-level data reproducing unit that generates and outputs multi-level data based on a phase relationship between a signal and the reference clock. 5. A multi-level data reproducing means, comprising: a signal processing circuit for detecting a peak level position of the reproduced signal; a data detecting circuit for detecting a phase difference between the peak level position and an edge of a reference clock; The optical recording / reproducing apparatus according to claim 4, further comprising a demodulation circuit that demodulates and outputs the reproduced data according to the phase difference.