JPH1153772A - Optical recording medium, optical cutting method and optical cutting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an effect of an offset to a regenerative signal and to sufficiently obtain clock information also by wobbling groove both side edges so as to become a phase opposite to each other and recording a clock signal with a change of a groove width. SOLUTION: Since a groove G whose both side edges are wobbled at the phase opposite to each other, it becomes the state being width modulated so that the groove width is fluctuated periodically. A land L between the grooves G is similar also. Although the user data containing redundancy such as an error correction code, etc., are recorded/reproduced on a clock area, a data part, by that the groove is width modulated, an external clock is generated from this signal, and the user data are recorded/reproduced synchronized with this. In the groove G, the wobble is left/right symmetric when viewing from a track center, and return light is changed by a track width change, and e.g. when a bisected photodetector is used, a return light change is detected by a sum signal. On the other hand, in the groove G, address information is obtained from an address area wobbled at the same phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium capable of high-density recording, and more particularly to an optical cutting method and an optical cutting apparatus suitable for manufacturing such an optical recording medium.

[0002]

2. Description of the Related Art In a rewritable high-density optical recording medium, in particular, a magneto-optical recording medium, a disk substrate is made as thin as 0.6 mm to enable a numerical aperture NA of an optical system of 0.6, and furthermore to enable a magnetic field modulation. Recording / reproducing laser wavelength: 630-650 nm, track pitch: 0.6 μm
m, recording linear density 0.20 μm / bit on one side (diameter 12
A format that realizes a large capacity of 5 to 7 GB (a so-called CD size of cm) has been proposed.

In this case, as a groove structure, a land / groove recording method which is advantageous for high density is adopted.

In the land / groove recording method, the format is such that recording and reproduction can be performed on both the land and the groove, and the optical disk has a two spiral structure of the land and the groove. Then, the address information and the clock information are inserted by wobbling the groove, and especially, the efficiency is improved by sharing the clock information with the data portion.

[0005] The land / groove format is an effective format for narrowing track pitch, and its characteristic is that when a tracking signal is obtained by a push-pull signal,
Since signals can be obtained from two tracks, an equivalent error signal can be produced up to a track pitch which is half the conventional one, and the land side and the groove side can be distinguished by their polarities.

[0006] In reproducing from a magneto-optical recording medium,
Optical masking can be performed based on the difference in depth between the land and the groove from the reproduction side, and crosstalk from an adjacent track can be reduced by properly selecting the depth.

[0007]

By the way, in the data section, user data including various kinds of redundancy are recorded and reproduced. By wobbling the groove at a certain frequency, an external clock is generated from this signal. Recording and reproduction are performed in synchronization with this clock.

However, if the groove is simply wobbled, there arises a problem that the direction of deflection of light fluctuates due to the wobbled groove and the reproduced signal is offset.

Accordingly, the present invention has been proposed in view of such a conventional situation, and provides an optical recording medium capable of suppressing the influence of an offset on a reproduction signal and sufficiently obtaining clock information. It is intended to do so. Further, it is an object of the present invention to provide an optical cutting method and an optical cutting device suitable for application when manufacturing such an optical recording medium.

[0010]

In order to achieve the above-mentioned object, an optical recording medium of the present invention is wobbled such that both side edges of a groove have opposite phases, and a clock signal is generated by a change in the width of the groove. Is recorded.

If the wobble is performed so that the both side edges of the groove have opposite phases, the groove becomes symmetrical when viewed from the center of the track, and the above-described offset works in the left and right sides and is canceled. As a result, the influence on the reproduction signal is suppressed, and clock information can be obtained efficiently.

When manufacturing the optical recording medium as described above,
It is conceivable that the width modulation of the clock section is realized by changing the laser power. However, since the wobble amount is as small as about 30 nm, it is difficult to control the laser power and to obtain a target wobble width. Further, even if it is obtained, there arise problems such as a difference between the inner and outer circumferences within the same master and a variation in the wobble amount for each stamper.

The optical cutting method and optical cutting device of the present invention have been devised to solve such a problem.

That is, the optical cutting method of the present invention exposes a resist while wobbling an exposure beam at a high frequency, and modulates the high frequency wobble into an envelope corresponding to the groove shape, thereby patterning into a desired groove shape. Alternatively, the resist is exposed by two beams that are wobbled in opposite phases to each other, and a groove whose width changes by superimposing the two beams is patterned.

Further, in the cutting apparatus of the present invention, a light source for emitting an exposure beam, a deflecting element for wobbling the exposure beam at a high frequency, and modulating a high frequency input to the deflecting element into an envelope corresponding to a groove shape. Or a light source for emitting an exposure beam, a beam splitter for splitting the emitted exposure beam into two beams, and a deflecting element for wobbling each of the split beams. And control means for controlling the deflection element so that the wobbles of the two beams have phases opposite to each other.

According to the optical cutting method and the optical cutting apparatus, a groove whose width is modulated is formed stably.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an optical recording medium of the present invention, for example, a magneto-optical disk, spiral or concentric grooves are formed, and user data is recorded and reproduced on both the grooves and the lands between the grooves. Configuration.

FIG. 1 shows the shapes of the groove G and the land L in the magneto-optical disk.

In the clock domain, both sides of the groove G are wobbled with phases opposite to each other, and as a result, the groove width is periodically changed, that is, in a so-called width-modulated state. The same applies to the lands L between the grooves G.

In the clock domain, that is, the data portion, E
User data including redundancy such as CC (Error Correction Code) is recorded and reproduced. In the present invention, an external clock is generated from this signal by width-modulating the groove.
Recording and reproduction are performed in synchronization with this clock.

In the groove G, the wobbles are symmetrical when viewed from the center of the track, and the return light changes due to the change in the track width. For example, when the two-divided photodetector is used, the return light Can be detected as a sum signal.

On the other hand, the groove G has an address area wobbled in the same phase, and address information can be obtained by an address signal recorded in this area.

Explaining the frame structure and the principle of wobble addresses in the magneto-optical disk, one track is divided into N frames in the magneto-optical disk of the present embodiment, and each frame has a data portion of 2 kB, a track address,
It is composed of an address section in which a frame address is recorded.

When one sector is handled as 2 kB, 1
If a frame and one sector match, and one sector is 32 kB, 14 sectors constitute one sector. The address part is further divided into a first address and a second address.

Here, since the address information is recorded by wobbling the groove G, the address information is distributed so as to be valid alternately as shown in FIG.

That is, on the groove G side, the first address,
Although any of the second addresses can be reproduced, only the portion where the same wobble is performed on the left and right tracks (grooves) can be reproduced on the land L side.

Therefore, in the land L and the groove G,
Although the same address is shared, as shown in FIG. 3, in order to select the first address or the second address,
There are two types of address mark polarities, and it is possible to recognize which is valid. Since the address mark is wobbled with a larger amplitude than the address portion, it can be detected from the difference in amplitude.

It is to be noted that the address portion is configured to wobble only on one side as shown in FIG. 4, so that the address is reproduced by the land L and the groove G without having the first address and the second address. However, in this case, if the amount of wobble is increased to increase the detection accuracy, crosstalk from an adjacent track increases,
As a result, the reading ability deteriorates.

In manufacturing the above-described magneto-optical disk, the following optical cutting may be performed to pattern the width-modulated groove shape.

FIG. 5 shows an example of the configuration of an optical cutting apparatus which constitutes a two-beam wobble optical system, inputs a wobble signal into each of them, and superimposes them to implement width modulation optical cutting.

This optical cutting device performs an exposure laser (Kr 413 nm) 1, beam splitters 2 and 3 for dividing a laser beam from the exposure laser 1 into two beams, and modulates (ON / OFF) each beam. Light modulating elements 4 and 5, light deflecting element 6 for wobbling each beam,
And a formatter 8 for controlling the light deflecting elements 6 and 7. Each of the beams wobbled by the light deflecting elements 6 and 7 is split into beam splitters 9, 10 and 11 and mirrors 12 and 1.
/ 4 wavelength plate 13, aperture lens 14, objective lens 15
It is configured to irradiate the resist master 16 via an optical system such as.

The laser beam from the exposure laser 1 is monitored by a photodetector 18 via an electro-optic modulator (EOM) 17, and when there is a change in intensity, feedback is provided by an APC driver 19.
The EOM 17 is controlled to keep the strength constant.

Further, a reflected light monitor camera 20 for monitoring the reflected light from the resist master 16 is provided.

In the optical cutting apparatus having the above-described configuration, the formatter 8 supplies a voltage of 30 mV and a frequency of 1.21.
A sine wave of 5 MHz and a sine wave of the opposite phase are generated and input to the optical deflection elements 6 and 7, respectively.

As a result, as shown in FIG. 6A, the beams B ₁ and B ₂ are wobbled in opposite phases to each other, and on the surface of the resist master 16, the interval between these two beams B ₁ and B ₂ is set. The groove width is determined. Then, as shown in FIG. 6B, a narrow portion and a wide portion are periodically formed in the groove by the reversed-phase wobble.

Since the address is a wobble in the radial direction which does not change the groove width, the address is formed by inputting the wobble signal to the optical deflection elements 6 and 7 in the same phase.

At the time of address exposure, it is also possible to turn off the reverse phase wobble output and perform exposure with one beam. In this method, it is not necessary to switch the output of the formatter, and it is possible to realize simpler cutting with the formatter. Is done.

The formatter 8 has a configuration as shown in FIG. 7 and first divides an external or crystal reference clock by 1 / X, and outputs a reference signal (15...) For spindle rotation control of the cutting machine. 75 kHz:
450 rpm).

Since the land and groove formats are used, the laser beam is transmitted for two tracks. However, the laser must be wobbled in the same phase when the disk makes one rotation. Must be exactly synchronized with In other words, a signal that has been wobbled by the groove can be reproduced by itself, but an adjacent groove must be read on the land, so that the signal cannot be reproduced without synchronization.

Therefore, for the same reference clock, M
A / N times master clock is generated by the PLL circuit 21. The frequency division value (M, N) can be used to generate a clock corresponding to each zone by dividing the disk into zones when cutting with CAV and changing parameters according to the zones.

This master clock is divided into 1/16 to generate a byte clock. The frequency divider 22 at this time
Counter address is SI for clock wobble
It is used as a table address for converting into N waves. After being converted as the amplitude information of the SIN wave, D
The signal enters the / A converter 23 and becomes an analog signal (clock wobble signal).

The byte clock becomes a frame clock by dividing the frequency by 1/2850. The top 96
Since the byte portion becomes an address portion, by using a signal (ADR portion) indicating this portion as an enable of the SIN wave conversion table 24, it is possible to control so as not to generate a generation pattern in the address portion.

Further, when this frame clock is counted 66, for example, at the outermost periphery, one track is obtained. The values of the frame counter 25 and the track counter 26 are put into a conversion table, and after performing modulation such as gray coding, the data is parallel-serial converted by a parallel-serial converter 27 (address wobble signal).

In order to perform wobbling in the same phase in the address section and in the opposite phase in the clock section, an inverted signal is also generated as the clock wobble signal, and two beams are added by adding the address wobble signal to the two polarity signals. Is generated.

In order to correct the relative positional relationship between the two beams, these two signals have a structure in which the time delay can be changed by delays 28 and 29, and are driven in accordance with the position on the disk surface. The signal is shifted.

FIG. 8 shows another optical system for two-beam exposure.

In the optical system shown in FIG. 5, modulation (ON / OFF) and deflection of the laser beam are performed by separate elements, but in the optical system shown in FIG. , The deflection is realized.

In the example shown in FIG. 5, an acousto-optic device (AOM) is used for the light modulators 4 and 5, and a laser beam is narrowed down by a single lens for high-speed modulation by the AOM.
Although the OM is provided, the AOM is shifted from the focal point to enable both the modulation and the deflection.

When this optical system is employed, the number of device assembly adjustment steps is reduced by half, and high-speed wobble of two beams can be easily performed.

On the other hand, it is possible to form a width modulation groove by forming a one-beam wobble optical system and sweeping the exposure beam B at a high frequency in the radial direction as shown in FIG. At this time, desired patterning can be realized by performing modulation in the same manner as a groove shape for obtaining an input high-frequency envelope.

As the optical system, as shown in FIG. 10, it is simplest to use only a portion corresponding to one beam of the optical system shown in FIG. 5, but when the beam is oscillated at a high frequency, the deflection element is used. You need to pay attention to the characteristics of

This is because when the AOM is used, the beam quality is deteriorated due to the cylindrical effect, and it is necessary to avoid this. Therefore, it is necessary to use a device such as an EOM as the deflecting element or to narrow the beam incident on the AOM. If the latter is adopted, one of the optical systems described in FIG. 8 may be used. Alternatively, in the optical system shown in FIG. 8, the AOM can be placed at a position shifted from the focal point of the aperture lens.

The frequency used in the experiment was 4 to 8 times the clock frequency of 1.215 MHz, and was 4.86 MHz each.
z was set to 9.72 MHz. This is to make it possible to form a smooth pattern by setting the wobble spatial frequency to an integral multiple of the clock spatial frequency.

By overwriting with a frequency four times or more, a smooth envelope can be obtained. The higher this frequency is, the better, but it is actually limited by the AOM band, and currently the limit is about 8 times used in this experiment.

The circuit configuration of the formatter for one-beam exposure is almost the same as that for two-beam exposure,
As shown in FIG. 11, the calculation part of the final stage is different in order to perform high-frequency superposition with one beam. That is, D /
A signal obtained by offsetting the master clock using the A-converted address wobble signal is added to a signal obtained by amplitude-modulating the master clock using the clock wobble signal. This signal controls the wobble of the beam.

In this example, the master clock is used. However, in principle, the frequency may be about four times the frequency of the clock wobble. Therefore, the master clock is generated using a signal obtained by dividing the master clock by 1/4. No problem.

The clock formation and the address formation have been described above. However, in the above description, the address is referred to only in the case of both-side wobbles. As the address recording method, one-sided wobble, width modulation, and the like may be considered, but basically, the above-described method is applied, and a signal corresponding to a pattern is input from the formatter, so that both-sided wobble is recorded. It can be formed as in the case.

[0058]

As is clear from the above description, in the optical recording medium of the present invention, the influence of the offset on the reproduction signal can be suppressed, and the clock information can be sufficiently obtained.

Further, according to the optical cutting method and the optical cutting apparatus of the present invention, the above-mentioned width modulation groove can be formed stably without variation.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing shapes of grooves and addresses.

FIG. 2 is a diagram showing an address configuration.

FIG. 3 is a schematic diagram for explaining a method of identifying an address mark.

FIG. 4 is a schematic diagram showing another example of an address shape.

FIG. 5 is a schematic diagram showing a configuration example of an optical cutting device of a two-beam exposure system.

FIG. 6 is a schematic view showing an exposure pattern by two-beam exposure.

FIG. 7 is a block diagram illustrating a circuit configuration of a formatter when performing two-beam exposure.

FIG. 8 is a schematic diagram showing another example of an optical cutting device of a two-beam exposure system.

FIG. 9 is a schematic view showing an exposure pattern by one-beam exposure.

FIG. 10 is a schematic diagram showing an example of an optical cutting device of a one-beam exposure system.

FIG. 11 is a block diagram showing a circuit configuration of a formatter when performing one-beam exposure.

[Explanation of symbols]

G groove, L land, 1 exposure laser, 6, 7
Optical deflection element, 8 formatters, 16 resist masters

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Toshiyuki Kashiwagi 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (7)

[Claims] 1. An optical recording medium characterized in that both sides of a groove are wobbled so as to have opposite phases, and a clock signal is recorded by a change in the width of the groove. 2. The groove according to claim 1, wherein the groove has an area wobbled so that both side edges have the same phase, and an address signal is recorded in this area.
The optical recording medium according to the above. 3. A resist is exposed while wobbling an exposure beam at a high frequency, and the high-frequency wobble is modulated into an envelope according to a groove shape, so that both sides are wobbled so as to have opposite phases or the same phase. An optical cutting method characterized by patterning into a groove shape. 4. The optical cutting method according to claim 3, wherein the exposure beam is wobbled at a spatial frequency that is at least four times the clock spatial frequency. 5. An optical cutting method, comprising exposing a resist with two beams wobbled in opposite phases to each other and patterning a groove whose width changes by superimposing the two beams. 6. A light source that emits an exposure beam, a deflecting element that wobbles the exposure beam at a high frequency, and a control unit that modulates a high frequency input to the deflecting element into an envelope corresponding to a groove shape. Characteristic optical cutting device. 7. A light source that emits an exposure beam, a beam splitter that splits the emitted exposure beam into two beams, a deflection element that wobbles each of the split beams, and the wobbles of the two beams have phases opposite to each other. Control means for controlling the deflection element as described above.