JPH06208723A - Optical disk and its manufacture - Google Patents

Abstract

(57) [Summary] [Structure] The clock pits 16 for detecting the timing of the reproduction signals of the tracking servo pits 4 and 5 are formed in the disc radial direction at a pitch of 1/4 to 1/2 of the track pitch, or Tracking servo pit 4,
An optical disc that is formed sufficiently away from 5. [Effect] The clock can be stably reproduced, high-speed seek is possible, and the tracking servo can be reliably and reliably performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk, and more particularly to a rewritable magneto-optical disk.

[0002]

2. Description of the Related Art Writing information by using a laser beam,
One of so-called rewritable optical disks that can be erased and read is a so-called magneto-optical disk.

In such a magneto-optical disk, each track is divided into a plurality of sectors, and each sector is further divided into a plurality of segments. A servo area for tracking is provided for each of these segments.

FIG. 11 shows an example of a sector format for each sector. According to this, although FIG. 11A shows one sector composed of a header area and 31 data segments, the length of the header area and each data segment is 24 bytes.

The header area is, as shown in FIG. 11B,
There is a 5-byte servo area at the beginning, and thereafter, an address area consisting of a 1-byte sector address SA and a track address TA as the subsequent 5 bytes is located.

A 6-byte check code is added to the sector address SA and the track address TA for error detection and / or correction code.
Furthermore, A with a length of 6 bytes is passed through a 1-byte margin.
An area for LPC (Automatic Laser Power Control) is provided.

The header area is preformatted and cannot be rewritten.

As shown in FIG. 11C, the data segment has a servo area of 5 bytes, which is the same as the header area, followed by a data area having a length of 19 bytes. The data area is irradiated with a laser beam, and data is recorded and reproduced by the magneto-optical effect.

Then, by using the pre-formatted tracking servo pits in the above-mentioned servo area, S
Tracking is controlled by the F method (sample servo method).

For this tracking control, as shown in FIG. 12, a servo area 2 is arranged in front of the address area 1, and the servo area 2 has the same amount in the direction away from the track center 3. 2 wobble pits (tracking servo pits) with offset of
4 and 5 are formed, and a clock pit 6 is formed between both servo pits 4-5 on the track center 3.

[0011] Specifically, the servo pits 4 and 5, inside or outside the respective radial direction of the disk at a distance of (1/4 of the track pitch t _p) from the track center 3 1/4 track pitch t _p Has been formed. In the address area 1, address pre-pits (address pits) 7 are formed on each track center.

In the sample servo type optical disk recording / reproducing apparatus, the data in the servo area 2
A tracking error signal is generated from the difference signal of the reproduction signal levels of the two servo pits 4 and 5, and based on this, tracking is controlled so that the laser beam is positioned at the track center 3. In this case, the clock pit 6
The servo pits 4 and 5 are sampled and used to determine the reproduction timing.

However, when the present inventor examined the above-mentioned conventional disk of the sample servo system, it was found that there were the following drawbacks (1) to (3).

(1) In FIG. 12, from the on-track state in which the laser beam 8 is irradiated onto the track center 3 as shown by the one-dot chain line s ₀ to the off-track state as shown by the two-dot chain line s ₁ (for example, seek). Time), the irradiation amount of the laser beam 8 to the clock pit 6 may be significantly reduced. In this case, since the signal of the clock pit 6 is hardly obtained, the address cannot be stably decoded at the seek time.

(2) A PLL (phase locked loop) is pulled in to generate a clock at the start of reproduction of a disc, but if a certain number of clock pit signals cannot be obtained in the on-track state at this time, the PLL is locked. Cannot be withdrawn. However, as described above, when the irradiation amount is greatly reduced during off-track and the degree of modulation of clock pits is greatly reduced, it takes time until the clock pit signals are counted to a predetermined number, and the seek time becomes long. .

(3) Clock pit 6 is servo pit 4
Since it exists between −5, the waveform of the reproduction signal of the clock pit 6 does not become an independent waveform due to the influence of crosstalk of the servo pits 4 and 5 (intersymbol interference), which causes the jitter of the clock. Was becoming. When jitter occurs in the clock in this way, the timing of sampling the servo pits 4 and 5 shifts, which causes detrack, and when detrack occurs, jitter in the clock occurs, which is a vicious cycle.

FIG. 13 shows sample servo signals in the on-track state and the off-track state when the sample servo is performed in the above format. However, the horizontal axis is the distance in the track direction, and the optical parameter is the laser beam wavelength (λ) = 780 nm,
Numerical aperture (NA) of objective lens = 0.55, light quantity distribution (A / W) when laser beam enters the objective lens =
0.7 (line direction or track direction), 1.4 (disk radial direction), pit length = 0.6 μm, pit width = 0.6
μm and pit depth ≈λ / 4.

According to this, in the on-track state, three peak values (the central peak is due to the clock pits, the peaks on both sides are due to the servo pits) show a sufficient magnitude, but as a whole in the off-track state. The peak value becomes smaller or varies. When the off-track amount is 1/4 track pitch, the fluctuation of the servo pit signal is large, but this is due to intersymbol interference with the clock pit.

Further, when the off-track amount is 1/2 track pitch, the servo pit signal has almost the same intensity as the servo pits of the adjacent tracks are reproduced, but the clock pit signal becomes extremely small. Will end up.

[0020]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disk capable of reproducing a stable clock, capable of high-speed seek, and reliable and reliable tracking servo, and a manufacturing method thereof.

[0021]

According to the present invention, as shown in an enlarged plan view of an essential part of an example of the present invention, tracking servo pits 4 and 5 which are offset from each other with respect to a track center are formed. The clock pits 16 for detecting the timing of the reproduction signals of the tracking servo pits 4 and 5 are formed in the disc radial direction at a pitch of 1/4 to 1/2 of the track pitch t _p (for example, 1/4 track pitch). To do.

Further, according to the present invention, the tracking servo pits 4 and 5 which are offset from each other via the track center are formed respectively, and the clock pits for detecting the timing of the reproduction signal of the tracking servo pits 4 and 5 are formed. 16 is formed at a position sufficiently distant from the tracking servo pit.

Further, according to the present invention, the tracking servo pits 4 and 5 which are offset from each other with respect to the track center are formed, respectively, and the clock pit 16 for detecting the timing of the reproduction signal of the tracking servo pits 4 and 5 is formed. 1/4 of track pitch
The clock pits 1 have a configuration in which they are formed in a disc radial direction at a pitch of ½ (for example, ¼ track pitch).
6 is formed in combination with a structure in which the tracking servo pits 4 and 5 are formed at positions sufficiently separated from each other.

According to the present invention, the photoresist film coated on the substrate is subjected to a developing process after drawing a recording pattern with a laser beam to form a mask of the photoresist film on the substrate, followed by a plating process. In a method for manufacturing an optical disc, in which a metal stamper is manufactured by performing a laser irradiation, a laser beam is irradiated around a track to move a track pitch in a substantially radial direction to draw a recording pattern in a spiral shape. By drawing the recording pattern by returning 3/4 track pitch in the substantially radial direction of the substrate for each circumference, the clock signal and the servo signal are recorded at ¼ to ½ track pitch.

[0025]

As described above, according to the present invention, the clock pits 16 are formed in the disk radial direction at a pitch of 1/4 to 1/2 of the track pitch t _p , or the tracking servo pits 4 and 5 are sufficiently formed. By forming them at positions separated from each other, it is possible to always include a required number of clock pits in the spot of the light beam even in the off-track state. Therefore, even in the off-track state, a sufficient reproduction signal (pit modulation degree) of the clock pit can always be obtained as in the on-track state, and high-speed seek can be easily realized.

Particularly, when the clock pit is provided at a position sufficiently distant from the servo pit, the intersymbol interference due to the crosstalk between the pits before and after the servo pit is eliminated, the waveform is not distorted during the clock reproduction, and the jitter is not generated. The sampling servo can be accurately timed, and the tracking servo can always be performed well.

Furthermore, according to the present invention, the recording pattern for one track is moved in the radial direction for one track and drawn, and then returned for the 3/4 track pitch in the radial direction of the disk to generate the clock signal and the servo signal. Since it is drawn, it is possible to form a clock signal or a tracking servo signal which is deviated from ¼ pitch to ½ track pitch simply by controlling the normal feed pitch of the cutting machine.

That is, when it is desired to form a clock pit or a servo pit at a position deviated from the track center by 1/4 to 1/2 track pitch as described above, for example, an AOD (acousto-optic device) is used to perform photo A method is conceivable in which the laser beam for exposing the resist film is oscillated left and right in the track extension direction.

However, when the AOD is used as described above, the work of adjusting the amount of pit deflection is complicated and requires a relatively long time, which may lead to a decrease in productivity. Further, if an AOD is provided in the middle of the optical path, a decrease in output of about 30% is unavoidable before and after passing through this element, resulting in a decrease in coupling efficiency. Also, the adjustment of AOD itself is complicated,
The amount of pit swing fluctuates with each AOD change,
This causes variations in characteristics.

On the other hand, according to the above-mentioned configuration of the present invention,
Without using such an AOD element,
It is possible to form pits with a 1/2 track pitch, thus improving the coupling efficiency of the optical system, facilitating the setting and installation of the optical system of the disc manufacturing device, and controlling the amount of pit deflection accurately. As a result, it is possible to significantly reduce the variation in the amount of pit deflection.

Further, sufficient exposure can be performed even when the output of the laser light source is relatively low. Therefore, when the change over time of the laser light source such as the solid-state laser element is the same as the conventional one, the life of the laser light source can be substantially extended.

[0032]

EXAMPLES Examples of the present invention will be described below. 1 to 3 show a first embodiment in which the present invention is applied to a rewritable magneto-optical disk.

The magneto-optical disk according to this embodiment is shown in FIG.
As a pre-format of the sample servo area of the sector format as shown in FIG. 1, as clearly shown in FIG. 1, a clock pit is not provided between the pair of tracking servo pits 4-5 on both sides of the track center 3, and A clock pit 16 is formed in the mirror portion 10 between the area 2 and the address area 1, and a large number of clock pits 16 are formed at an arrow d at a quarter track pitch t _p (here, track pitch t _p = 1.5 μm). It is formed uniformly in the radial direction of the disk.

Therefore, the clock pits 16 are arranged so as to be continuously connected (radially) in the radial direction of the disk when viewed optically. A method of forming the clock pit 16 will be described in detail later.

With this structure, the following remarkable effects (A) to (C) can be obtained in comparison with the above-mentioned conventional example.

(A) In FIG. 1, even if the on-track state of the laser beam 8 shown by the one-dot chain line changes to the off-track state (for example, the off-track amount of 1/2 track pitch) as shown by the two-dot chain line, the laser beam The eight spots always include the required number of clock pits 16 (for example, a minimum of three).

Therefore, the reproduction signal (pit modulation degree) of the clock pit 16 is always sufficiently obtained even in the off-track state as in the on-track state, so that the clock reproduction and the address decoding can be stably performed at the seek time. It will be. Even if the address is not subjected to tracking servo, the clock for decoding the address may operate stably.

(B) Since the same clock pit modulation degree can be obtained during off-track as during on-track,
Addresses can be stably decoded even during seek, and a predetermined number of clock pit signals can be quickly counted during seek, so high-speed seek can be easily realized.

(C) Since the clock pits 16 are provided not in the servo pots 4-5 but in the mirror section 10 sufficiently separated from these servo pits, there is no intersymbol interference due to crosstalk between the pits before and after the servo pits. , The waveform will not be distorted and jitter will occur during clock reproduction. As a result, the timing for sampling the servo pits 4 and 5 can be accurately taken, and the tracking servo can always be performed well.

FIG. 2 shows the reproduction signal of the clock pit 16 (the horizontal axis is the distance in the track direction), but the reproduction signal of the clock pit 16 is the same as that in the on-track (on-pit) state even in the off-track state (off-pit). It can be seen that it indicates the degree of modulation. Here, as optical parameters, the wavelength (λ) of the laser beam is 780 nm, the numerical aperture (NA) of the objective lens is 0.55, and the light amount distribution (A / W) when the laser beam is incident on the objective lens is 0. 7 (line direction or track direction), 1.4 (disk radial direction), pit length = 0.6 μm, pit width = 0.6 μm, and pit depth≈λ / 4.

Since there is almost no difference in the pit modulation degree between on-track and off-track as described above, the clock pits 16 optically appear to be continuously connected radially in the disk radial direction. This means that the clock is stable even during the seek operation, and the address decoding during the seek operation can be stably performed.

The result of FIG. 2 is that the clock pit 16
It shows that there is no intersymbol interference with the pits before and after the reproduction. This is because the clock pit 16 is formed in the mirror portion 10 (that is, a position sufficiently distant from the servo pits 4 and 5) where intersymbol interference does not occur.

FIG. 3 shows the pit depth dependence of the pit modulation degree by the clock pits 16 for each pit length. Therefore, it can be seen that the modulation degree is improved depending on the pit depth, and the modulation degree is improved when the pit length is short. Even if the pit length is 1.0 μm, the modulation factor is 0.5
The above can be secured.

FIG. 4 shows a second embodiment in which the present invention is applied to a rewritable magneto-optical disk.

The feature of this example is that the clock pits 16 shown in FIG. 1 are formed between the tracking servo pits 4-5. That is, although the positions of the clock pits are the same as those in the conventional example, a large number of clock pits 16
Are arrayed and formed at a pitch of 1/4 track pitch in the disk radial direction indicated by arrow r. In FIG. 4, parts corresponding to those in FIG. 1 are designated by the same reference numerals and redundant description will be omitted.

Therefore, the clock pits 16 are arranged so as to be continuously connected (radially) in the radial direction of the disk indicated by the arrow r, as in the above example. The position of the clock pit 16 in the line direction does not substantially need to be changed from the conventional specifications.

With this structure, the remarkable effects of the terms A and B, which are described in comparison with the conventional example in the description of the first embodiment, can be obtained.

That is, even in the off-track state, since the required number of clock pits 16 (for example, a minimum of 3) are always included in the spot of the laser beam 8, the pit modulation degree is off-track. Even in the state, it is possible to always obtain a sufficient amount as in the on-track state, and it is possible to stably reproduce the clock and decode the address when seeking. Moreover, the address can be stably decoded even during the seek operation, and a predetermined number of clock pit signals can be quickly counted, so that high-speed seek can be easily realized.

Further, since the clock pits 16 are formed so as to be connected radially, the degree of modulation (reproduction signal amount) is increased, and the influence of intersymbol interference due to the crosstalk between the pits before and after the pits is reduced, and the clock Jitter during playback is reduced.

FIG. 5 shows a third embodiment in which the present invention is applied to a rewritable magneto-optical disk.

In this example, the mirror portion 10 is characterized in that only one clock pit 26 is formed at the track center in the disk radial direction, that is, at one track pitch. That is, the number of clock pits is the same as in the conventional example, but the clock pits 26 are formed in the mirror section 10. In FIG. 5, parts corresponding to those in FIG. 1 are designated by the same reference numerals and redundant description will be omitted.

According to this structure, in particular, C described as a comparison with the conventional example in the above description of the first embodiment is described.
A significant effect of the item can be obtained.

That is, although one clock pit 26 is formed at the track center as viewed in the disk radial direction indicated by the arrow r, its position is at the tracking servo pits 4, 5.
Since it is located in the mirror section 10 that is sufficiently away from, the intersymbol interference due to the crosstalk of the pits before and after it is eliminated, and the jitter during clock reproduction does not occur. Since only one clock pit 26 needs to be formed at the track center in the radial direction of the disc, the cutting can be easily performed.

FIG. 6 shows a fourth embodiment in which the present invention is applied to a rewritable magneto-optical disk.

This example is a combination of the example shown in FIG. 4 and the example shown in FIG. 5, in which a large number of clock pits 16 are uniformly distributed in the disk radial direction at a quarter track pitch between the tracking servo pits 4-5. And one clock pit 26 at the track center when viewed in the radial direction of the disc.
Is characteristically formed on the mirror portion 10. 6, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and duplicate description will be omitted.

According to this structure, it is possible to obtain the operational effect of the second embodiment and the operational effect of the third embodiment at the same time. That is, the clock pits 16 have a sufficient pit modulation degree, which enables stable clock reproduction, address decoding, and high-speed seek, and the clock pits 26 mainly eliminate jitter due to intersymbol interference.

Although the respective embodiments of the present invention have been described above, the respective embodiments described above can be further modified based on the technical idea of the present invention.

For example, in the above-mentioned first and second embodiments, the clock pits 16 are formed with a 1/4 track pitch, but this pitch may be arbitrarily changed.
It can also be formed in the disk radial direction at a pitch within the range of 4 track pitch to 1/2 track pitch. When the clock pits 16 are formed with a 1/2 track pitch, there are clock pits that always enter the laser beam irradiation area even during off-track, and the pit modulation degree is good.

When clock pits having different pitches are combined as in the above-described fourth embodiment, the pitch change can be further arbitrarily set. First mentioned above
It is also conceivable to combine the third embodiment and the conventional example (example of FIG. 12).

Further, for example, although the clock pit is formed in the mirror portion in the above-mentioned first embodiment, it is not limited to the mirror portion as long as the position is sufficiently separated from the tracking servo pit. It can also be formed at a position (not shown). Further, not only the pitch of the clock pits but also their length, depth, shape, etc. may be changed.

Although the above-mentioned examples are all related to the servo area in front of the address area, the same servo pits and clock pits as those in the above-mentioned example are also applied to the servo area of the data segment (see FIG. 11). be able to.

The present invention can be applied to various optical disks other than the above-described rewritable magneto-optical disk.

Next, clock pits are provided at 1/4 track pitch intervals in the pit structure shown in the first embodiment described in FIG. 1, that is, in the so-called mirror portion between the servo area and the address area. A method of manufacturing an optical disc will be described in detail with reference to the explanatory diagram of FIG. In FIG. 7, alternate long and short dash lines t ₀ , t ₁ , t ₂ , ...
Each t _n represents the track center from the 0th track to the nth track. Further, the numbers (1) to (4 (n + 1) +1) are the recordings of the respective pits, that is, the tracking servo pits 4 and 5, the clock pit 16, and the address pit 7 for each ¼ track pitch. The positions are schematically shown, and (2), (6), (10), ... (4n + 2) ... correspond to the center of each track.

In such an optical disk, a recording pattern is drawn on the photoresist film coated on the substrate as described above with a laser beam, and then development processing is performed to form a mask of the photoresist film on the substrate. After forming the metal stamper, a metal stamper is formed by plating, and then a transparent substrate can be formed by resin molding or the like.

That is, the pulse at the start position is received from the cutting machine, and from there, the signal generator starts operation and starts outputting the signal of the pit train. When forming a signal with a 1/4 track pitch shift with normal cutting,
The beam is scanned over the center of the track, and when the servo pit is reached, a voltage is applied to the AOD so that the laser beam is drawn by swaying the track center by 1/4 track pitch.

However, in this embodiment, the clock pit or the pit of the data signal is output from the signal generator in the first rotation, and the beam is emitted, and in the second rotation,
When the initial position is reached, the track pitch is returned by 3/4 and recording is performed.

That is, in the present embodiment, the laser beam is irradiated for one round of the track and is moved in the radial direction by one track pitch to draw a recording pattern in a spiral shape. The operation of drawing the recording pattern by returning the track pitch by 3/4 in the radial direction is repeated for each track, and the clock signal and the servo signal are set to 1
Record at / 4 to 1/2 track pitch.

By doing so, the track 1
Although the feed of the 1/4 track pitch is performed for each circumference, the recording of the 1/2 track pitch is performed by alternately repeating, for example, the case where the recording is performed and the case where the recording is not performed with respect to the movement of the one cycle. It is also possible, and when recording is performed every time, recording with a ¼ track pitch can be performed.

By using such a method, the disk having the structure shown in FIG. 1 can be formed by the following operation.

That is, in this case, as shown in FIG.
At the position of (1) of the lap, the recording pattern of only the clock pit 16 is drawn, and at the position of (2) of the lap, the recording pattern of the tracking servo pit 4 and the clock pit 16 is drawn, and the third lap. In the position (3), clock pit 16 and address pit 7, ROM (Read Only Disc)
In the case of, the data pit, the tracking servo pit 5 and the clock pit 16 at the position of (4) on the fourth lap, and the position of the clock pit 16 at the position of (5) on the fifth lap are the same as the position of (1). The drawing is repeated.

Next, a method of manufacturing a stamper for manufacturing such an optical disc will be described with reference to FIGS. Here, the apparatus shown in FIG. 8 shows the configuration of an optical recording apparatus (laser cutting apparatus) used for producing an optical disk master, which is a pre-stage of a stamper.

As shown in the figure, this apparatus has a gas laser light source 21 using a gas as an amplification medium, and a horizontal electro-optical device for intensity-modulating the laser light L emitted from the gas laser light source 21 according to an input signal electric field. Modulator (Erectro Op
tic Modulator; hereinafter simply referred to as EOM) 22 and the above EOM 22 based on the ultrasonic wave modulated by the recording signal.
Acousto-optical modulator (Acou
sto Optic Modulator; hereinafter simply referred to as AOM) 23
And the laser light L intensity-modulated by the AOM 23,
The mirror 25 is guided to the cutting head 24.

The cutting head 24 uses the laser light L.
An objective lens 28 for condensing the light on a photoresist film 27 formed on a circular glass substrate 26, and the mirror 2
5 and a mirror 29 that reflects the light L guided by 5 to the objective lens 28 side. In particular, the objective lens 28 is
The photoresist film 27 is disposed so as to face the photoresist film 27 with a predetermined gap. And this cutting head 24
Moves in the radial direction of the glass substrate 26 by a known moving mechanism mainly including the stepping motor 50.

The position of the cutting head 24 is below the slit (laser scale) attached to the cutting head 24 or the stepping motor 50.
It is adapted to be detected by an encoder 11 composed of a code plate or the like attached to the shaft of the. The glass substrate 26 is fixed on the circular stage 12 by, for example, vacuum suction, and the stage 12 is rotationally driven by the spindle motor 13,
It is designed to rotate in a CAV (constant rotation angle) system.

Particularly in the present invention, the index pulse I _p is sent to the control circuit (CPU; central processing unit) 51 from the spindle motor 13 that rotationally drives the stage 12 for each rotation, and based on this, one cycle is performed. Stepping motor 5 to return 3/4 track every time a minute is recorded
0 is controlled to control pickup feed of the cutting head 24.

Here, when the photosensitive material of the photoresist film 27 is a positive type, the laser light L having an oscillation wavelength of 458 nm for the Ar laser and 442 nm for the He-Cd laser is selected. Recently, 400n
A Kr laser having an oscillation wavelength near m may also be used. Further, these gas lasers are emitted as linearly polarized laser light L through the Brewster window.

The EOM 22 is, for example, ADP (NH_Four
H₂PO_Four) And KDP (KH₂PO _Four) Composed of crystals
The variable DC power supply 14 between the electrodes of this EOM 22
Only connected. Normally, this variable DC power supply 14
Output a constant level DC voltage V. And
Linearly polarized laser light L incident on the EOM 22, especially the medium
Optical phase difference Δφ between two orthogonal polarization components in quality
However, when the DC voltage V is supplied from the variable DC power source 14,
The polarization state of the laser light L is controlled by this control.
Change.

The laser light L that has passed through the EOM 22 is
Since it becomes elliptically polarized light, it is converted into intensity-modulated light by the analyzer 15 composed of a ¼ wavelength plate and an analyzer in the subsequent stage. That is, the elliptically polarized laser light output from the EOM 22 is
First, it is returned to the linearly polarized laser light L by the quarter-wave plate, but since the vibrating surface of the electric vector is rotated by an angle Δφ / 2 proportional to the DC voltage V as compared with the incident light, then It is converted into intensity-modulated light by the analyzer. In this case, the laser light L output from the EOM 22 is an optical output (light quantity) proportional to the characteristic curve sin ² (V) shown in FIG.
Becomes

In this embodiment, the EOM22
By arranging a half mirror or a beam splitter (hereinafter, referred to as a half mirror) 16 in the latter stage (more accurately, in the latter stage of the analyzer 15), the laser light L transmitted through the EOM 22 is divided into two, and the two The photodetector 17 is arranged on the first optical path extending to the transmission optical path of the EOM 22 in the optical path branched into the optical path, and the voltage control circuit 18 is connected to the subsequent stage. Then, the voltage control circuit 18 and the variable DC power supply 14 are connected. That is, EOM22, photodetector 1
7, the voltage control circuit 18, and the variable DC power supply 14 constitute one feedback system 19. The photodetector 17 is
The optical output of the laser beam L that has passed through the EOM 22 is converted into a signal current (detection signal) Ss, which can be configured by a photodiode, for example.

For example, as shown in FIG. 9, the voltage control circuit 18 detects the difference between the preamplifier 51 for converting the detection signal Ss from the photodetector 17 into a voltage and the voltage signal Vi from the preamplifier 51 and the reference voltage Vr. Difference amplifier 5
2 and a drive amplifier 53 that amplifies the difference signal Δv from the difference amplifier 52 with a predetermined gain. Here, the reference voltage Vr is set to a voltage corresponding to a desired light output (light quantity). The variable DC power supply 14 is composed of a reference voltage source 54 and an adder 55 that adds the reference voltage Vb from the reference voltage source 54 and the amplification difference signal ΔV from the drive amplifier 53.

The operation of the feedback system 19 will be described. First, a part of the laser beam L that has passed through the EOM 22 is incident on the photodetector 17 via the half mirror 16 or the like. The photodetector 17 outputs a signal current (detection signal) Ss corresponding to the amount of incident laser light L.
The detection signal Ss from the photodetector 17 is converted into a voltage by the preamplifier 51 in the subsequent stage, and is output as a voltage signal Vi having a voltage level corresponding to the current level of the detection signal Ss.

Then, the difference amplifier 52 in the next stage outputs the difference signal Δv indicating the level difference between the voltage signal Vi and the reference voltage Vr. When the level of the voltage signal Vi is higher than the level of the reference voltage Vr, the negative level difference signal Δv is output, and conversely, when the level of the voltage signal Vi is lower than the level of the reference voltage Vr, the positive level difference signal Δv. Is output.

The difference signal Δv from the difference amplifier 52 is
The drive amplifier 53 in the subsequent stage is amplified with a predetermined gain. For example, as shown in the characteristic diagram of FIG. 10, this gain is a fixed variation Δ based on the light quantity at the operating point P corresponding to the reference voltage Vb of the variable DC power supply 14 in advance.
The phase difference Δφa at point A in I is calculated, and the difference signal Δ output from the difference amplifier 52 at this time is calculated.
It is set based on v and the phase difference Δφa.

Then, the adder 55 in the subsequent stage adds the amplification difference signal ΔV from the drive amplifier 53 and the reference voltage Vb from the reference voltage source 54, and the added voltage signal V is applied between the electrodes of the EOM 22. Is supplied to. That is, EO
The reference voltage (EOM) is set so that the light quantity of the laser light L passing through M22 becomes the reference light quantity corresponding to the reference voltage Vr.
The voltage V) applied to 22 will change. Therefore, the optical output (amount of light) of the laser light L transmitted through the EOM 22
However, even when the temperature fluctuates due to a change in temperature, the amount of light becomes constant by the feedback system 19.

On the other hand, in the optical path branched into two by the half mirror 16 or the like, on the second optical path through which the laser light L reflected by the half mirror 16 or the like passes, the beam reducing lens 31, the AOM 23 and the beam expanding lens. 32 are arranged in order. An ultrasonic wave generator 33 is connected to the AOM 23. The ultrasonic wave generator 33 outputs a generated ultrasonic wave to a recording signal (a recording pattern to be drawn on the photoresist film 27 is supplied to an input terminal φin). The signal is modulated based on the (electrically converted signal) Sw. The ultrasonic wave W modulated by the ultrasonic wave generator 33 is
It is supplied to the AOM 23.

The AOM 23 is composed of, for example, a TeO ₂ crystal, and the phase diffraction grating due to the change in the refractive index generated in the crystal by the ultrasonic wave supply from the ultrasonic wave generator 33 is used for the Bragg diffraction. The first-order diffracted light is used for signal recording. The intensity of the diffracted light is determined by the ultrasonic power, and the diffraction direction is determined by the carrier frequency. Therefore, in principle, there is no bias fluctuation as in the EOM 22. Further, recently, with the improvement of the crystal device and the generator, it is possible to obtain the modulation bandwidth equivalent to that of the EOM22. Moreover, since feedback control is not performed, stable optical modulation can be performed on any duty signal or low frequency signal.

The recording signal Sw is created by the recording signal generator 34. The recording signal generator 34 creates the recording signal Sw based on the clock signal Sc generated by the PLL 35 and the recording data Dp from the control unit 36. PLL
Reference numeral 35 generates a clock signal Sc based on the rotation timing signal St from the spindle motor 13.

The control unit 36 sets the recording data (pit pattern data) registered in the pattern memory 37 to P
Read based on the clock signal Sc from LL35,
The signals are sequentially supplied to the recording signal generator 34. Then, the recording signal generator 34 outputs a recording signal Sw according to the recording data Dp from the control unit 36. The recording signal Sw has a signal waveform of high level when the recording data Dp is logically "1" and low level when the recording data Dp is "0", for example.

The control unit 36 receives the position data D from the encoder 11 based on the clock signal Sc from the PLL 35.
Is read, and the corresponding power modulation data Dm is read from the memory 37 by using the position data D as an address.
The read power modulation data Dm is transferred to the D / A converter 3
It is converted into an analog power modulation signal Sm at 9 and supplied to the amplitude modulation circuit 38. Then, in the amplitude modulation circuit 38, the amplitude of the recording signal Sw sent from the recording signal generator 34 is modulated according to the level of the power modulation signal Sm, and the output of the signal obtained inside and outside the disk is equal. Is adjusted to the level of.

The beam diameter of the laser beam L intensity-modulated by the AOM 23 is restored by the beam expanding lens 32 in the subsequent stage, and further guided to the objective lens 28 side by the mirrors 25 and 29 in the subsequent stage. The light is condensed by the objective lens 28, and the photoresist film 27 is irradiated with the light. At this time, the glass substrate 26
However, the spindle motor 13 is rotating in one direction by the CAV method, and the moving mechanism causes the cutting head 24 to return by 3/4 track pitch every time one cycle of drawing is performed, as described above, and substantially. Since it moves in the radial direction of the glass substrate 26 by 1/4 track pitch, the recording pattern based on the recording signal Sw is drawn on the photoresist film 27 at 1/4 to 1/2 track pitch, and the drawing is performed. It is exposed along the recording pattern.

The exposed portion is dissolved by the developing solution in the subsequent developing process. That is, in the developing process, the exposed portion is removed and a mask made of the photoresist film 27 is formed. At this point, a master of a magneto-optical disk is obtained.

After that, for example, electroless plating is performed,
After making the photoresist film 27 conductive, metal plating is performed to form a metal plating film on the entire surface of the photoresist film 27. After that, the metal stamper is peeled off to complete the metal stamper.

When a magneto-optical disk is manufactured using the stamper, after the above process, the mass copying process is performed, and the stamper is used as a mold, for example, an injection molding method, a compression molding method or a photopolymerization (2p) method. Can be used to duplicate magneto-optical disks.

As described above, in this example, A
Since tracking servo pits and clock pits can be recorded and formed at a pitch of 1/4 to 1/2 track without using an OD, it is necessary to have the same device configuration as the conventional one, that is, to significantly modify the cutting equipment. Therefore, the disk having the structure of the present invention can be manufactured.

Further, the current stepping motor 50 can perform slide feeding of about 1/4 track pitch with sufficient accuracy. In addition, it is not necessary to position each pit, and it is possible to manufacture an optical disc extremely easily and surely.

Furthermore, the optical system of the optical recording apparatus has an AOD
In the case of using, the output is reduced by about 70%, but in the present example described above, since this is not used, the decrease in coupling efficiency can be avoided, and the life of the laser light source is effectively extended. be able to.

In the above example, the case where the invention is applied to the manufacture of the optical disk described in FIG. 1 is explained.
The method of the present invention can be applied to the production of the optical disc having the configuration of the present invention shown in each of the other examples, and to the production of various other discs. Further, it goes without saying that the optical recording device as an example thereof is not limited to the above-mentioned configuration and can be variously modified and changed.

[0098]

As described above, according to the present invention, the clock pits for detecting the timing of the reproduction signal of the tracking servo pits are formed in the disc radial direction at a pitch of 1/4 to 1/2 of the track pitch, or the tracking pits are formed. Since it is formed sufficiently away from the servo pits, the required number of clock pits is always included in the spot of the light beam even in the off-track state. Therefore, the reproduction signal (pit modulation degree) of the clock pit can always be sufficiently obtained even in the off-track state as in the on-track state, so that the clock can be stably reproduced during the seek, and the high-speed seek can be performed. Easy to implement.

Since the clock pits are provided sufficiently away from the servo pits, the intersymbol interference due to the crosstalk between the pits before and after the servo pits is eliminated, and the waveform is not distorted and the jitter is not generated during the clock reproduction. As a result, the timing for sampling the servo pits can be accurately taken, and the tracking servo can always be performed well.

Furthermore, according to the present invention, since recording is performed by returning to 3/4 tracks after performing recording for one round, servo pits of substantially 1/4 to 1/2 track pitch,
The clock pit can be easily formed.

Further, at this time, since the recording can be performed by controlling the stepping motor without using the AOD, it can be manufactured by the conventional cutting equipment on the mastering line without making a great modification.

Further, it is possible to avoid a decrease in the coupling efficiency of the optical system, and it is possible to prolong the effective life of the laser light source.

[Brief description of drawings]

FIG. 1 is an enlarged plan view of a main part of a disc according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a reproduction signal of a clock pit in the first embodiment of the present invention.

FIG. 3 is a diagram showing the pit depth dependency of the clock pit modulation degree in the first embodiment of the present invention.

FIG. 4 is an enlarged plan view of an essential part of a disk according to a second embodiment of the present invention.

FIG. 5 is an enlarged plan view of an essential part of a disk according to a third embodiment of the present invention.

FIG. 6 is an enlarged plan view of an essential part of a disk according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram of the manufacturing method according to the first embodiment of the present invention.

FIG. 8 is a configuration diagram of an example of an optical recording device.

FIG. 9 is a configuration diagram showing an example of a feedback system circuit of the optical recording apparatus.

FIG. 10 is a diagram showing input-output characteristics of EOM.

FIG. 11 is an explanatory diagram of a sector format of a conventional rewritable magneto-optical disk.

FIG. 12 is an enlarged plan view of a disk main part of the magneto-optical disk.

FIG. 13 is a diagram showing a sample servo signal in the magneto-optical disk.

[Explanation of symbols]

 1 Address Area 2 Servo Area 3 Track Center 4, 5 Tracking Servo Pits 6, 16, 26 Clock Pits 7 Address Pits 8 Laser Beam 10 Mirror

Claims (4)

[Claims] 1. Tracking servo pits offset from each other with respect to the track center are formed, and clock pits for detecting the timing of a reproduction signal of the tracking servo pits are 1/4 to 1/2 of the track pitch. An optical disc, wherein the optical disc is provided in the radial direction of the disc at a pitch of. 2. Tracking servo pits that are offset from each other with respect to the track center are formed respectively, and clock pits for detecting the timing of the reproduction signal of the tracking servo pits are located at positions sufficiently separated from the tracking servo pits. An optical disc characterized by being provided in. 3. Tracking servo pits offset from each other with respect to the track center are formed, and clock pits for detecting the timing of a reproduction signal of the tracking servo pits are 1/4 to 1/2 of the track pitch. An optical disc comprising a combination of a structure formed in the disk radial direction at a pitch of 1 and a structure formed such that the clock pits are sufficiently separated from the tracking servo pits. 4. A photoresist film coated on a substrate is subjected to a development process after drawing a recording pattern with a laser beam to form a mask of the photoresist film on the substrate, and then a plating process is performed. In the method of manufacturing an optical disc for manufacturing a metal stamper, the laser beam is irradiated around the track for one track, and the track is moved in the radial direction by one track pitch to draw a spiral recording pattern. 3 in almost the radial direction of the above-mentioned substrate every one turn
/ 4 track pitch is restored and the recording pattern is drawn, so that the clock signal and the servo signal are 1/4 to 1/2.
A method for manufacturing an optical disc, wherein recording is performed at a track pitch.