JPH07129956A - Optical disk device - Google Patents

Abstract

PURPOSE:To attain a simultaneous verification by a single light source and to ensure an exact operation without adjustment by dividing the beam from the single light source into two beams and providing various kinds of means which make the interval between the beams a value of an integer multiple of a channel bit interval plus the half of the former. CONSTITUTION:A laser diode (LD) 1 is driven by an LD modulation circuit 2. The beam emitted from the LD1 becomes a parallel beam by a collimate lens 3 and is divided into two beams, i.e., a main beam and a sub-beam by a diffraction grating 4. The gap between the main beam and the sub-beam is made a value of an integral multiple of a channel bit interval plus the half of the former. During a writing, the period when a second level erase power is raised to a first level write power is made approximately the half of a channel period. Moreover, a data reproducing is performed by the sub-beam in synchronism with a clock which has an opposite phase to a main clock. Thus, a simultaneous verification is exactly performed using a single light source without gain adjustment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an optical disk device which is a light modulation recording system and which performs verification when data is recorded by a single light source.

[0002]

2. Description of the Related Art Generally, in an optical disk device, a verify operation is performed after recording data to confirm whether the data has been written correctly. In a normal optical disk device, since only one light beam is used for recording / reproducing data, the disk is further rotated once after writing the data, and after the portion where the data has been written appears again, the data is reproduced and the verify operation is performed. Will be done. As a method of eliminating the time required for this verify operation and shortening the write time, a method called simultaneous verify, in which data writing and verify are performed at the same time using a plurality of beams, or a method called read after write is being studied.

By the way, as a method for writing data on an optical disk, an optical modulation method for modulating a laser serving as a light source is generally used. However, when the beam emitted from a single laser is divided into a recording beam and a verifying beam when the above-mentioned simultaneous verifying is performed by an optical modulation method, the verifying beam is intensity-modulated together with the recording beam. Since the reproduced signal amplitude is not constant, the verify operation cannot be performed correctly. This problem can be solved by separately providing a laser serving as a light source for the recording beam and a light source for the verifying beam, but there is a drawback that the cost of the apparatus increases.

Therefore, in order to correctly perform simultaneous verification by using a single light source, a method of detecting a modulation component of laser light and performing a verification operation with a reproduction signal corrected for the modulation component is disclosed. It is disclosed in Japanese Patent Publication No. 2-5222.

[0005]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2-522
The technique disclosed in Japanese Patent Publication No. 2 is that a monitor signal for monitoring the output of a laser serving as a light source and a reproduction signal reproduced by a verifying beam are appropriately amplified and then subtracted to cancel the modulation component. However, while the monitor signal is directly determined by the laser output, the reproduction signal is affected not only by the laser output but also by the reflected light of the disk.
Since the reflectance of the disc varies from disc to disc, the amplification gain before subtraction must be adjusted at least for each disc. Further, even with the same disc, the reflectance fluctuates slightly depending on the location, so the fluctuation component of the reflectance remains in the reproduced signal after subtraction, and the correct verify reproduced signal cannot be obtained, and the verify operation fails. there is a possibility.

[0006] The applicant of the present invention, in Japanese Patent Laid-Open No. 5-36110, simultaneously uses so-called pulse magnetic field modulation (a method of changing an external magnetic field according to recording data, and further performing pulse modulation of a laser with recording power to perform magneto-optical recording). The verification method is proposed. This is for performing simultaneous verification by a signal reproduced by a verifying beam while the laser is emitting light at the recording power. However, even if this method is applied to the optical modulation recording as it is, there is a period (data is “0” portion) where the recording power emission is not performed depending on the recording data, and therefore the data can be reproduced by the verify beam. Can not.

The present invention has been made in view of the above circumstances, and provides an optical disk device which can realize simultaneous verification by a single light source even in an optical modulation recording method and can perform an accurate operation without adjustment. Is intended.

[0008]

In order to solve the above-mentioned problems, an optical disk apparatus of the present invention is an optical disk apparatus for recording information on an optical disk so that the recording linear density is substantially constant along an information track. First clock generating means and second clock generating means for generating first and second clocks having the same frequency and substantially opposite phases, and driving in synchronization with the first clock according to information to be recorded. Modulating means for generating a signal, a light source driven by the modulating means, a beam splitting means for splitting emitted light of the light source into at least two of a main beam and a sub beam, and a main beam split by the beam splitting means. And sub-beams on the information track, d an interval of one channel bit of data on the information track, and N an arbitrary integer. And a first light receiving means and a second light receiving means for receiving the reflected light of the main beam and the reflected light of the sub beam from the optical disk, respectively. Is provided.

Further, in the optical disc apparatus, at the time of recording information, the modulating means should form a mark with a time width of less than one clock cycle centering on the rising or falling of the first clock and forming a mark. The light source is caused to emit light at a level, and the light source is caused to emit light at a second level which is substantially a regulated level during the other period to record information by the main beam, and at the same time, according to the second clock, the second light is emitted. Information is reproduced based on the output of the light receiving means and collated with the recorded data.

[0010]

[Operation] In the structure of the above invention, the distance between the main beam and the sub beam on the information track is approximately (N + 0.5) × d, and the first clock and the second clock are approximately Since the phases are opposite to each other, when the data is written by the main beam according to the first clock, the second clock almost coincides with the data position (identification point) of the signal reproduced by the sub beam. Also, the light source is the first
Since the period of emitting light at the level is less than 1 clock cycle,
The light source always emits a substantially constant amount of light at the second level near the rise or fall of the second clock having the opposite phase to the first clock.

Therefore, if the signal reproduced by the sub-beam is read out in accordance with the second clock, the light source always emits light at the second level near the rising edge of the second clock, so that the influence of modulation by the recorded data is exerted. Therefore, the simultaneous verify operation can be performed without any special adjustment.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 relate to a first embodiment of the present invention, FIG. 1 is a block diagram of an optical disk device, FIG. 2 is a timing chart of the device shown in FIG. 1, and FIG. 3 is an explanatory view showing a positional relationship between a main beam and a sub beam. It is a figure.

This embodiment will be described by taking an optical disk device using a phase change (PC) type optical disk as a recording medium as an example.

FIG. 1 is a diagram showing a schematic configuration of an optical disk apparatus according to this embodiment, in which a recording / reproducing system is mainly shown and a servo system and the like are omitted.

The optical disk device 21 shown in FIG. 1 is a laser diode (hereinafter sometimes referred to as LD) 1 serving as a light source.
An LD modulation circuit 2 for driving the LD1 by modulated recording data (WRITE DATA), a collimator lens 3 for making the laser light emitted by the LD1 parallel light, and a light beam for separating the parallel light into at least two light beams. A diffraction grating (grating) 4 as a separating means, a beam splitter 5 that transmits the two light beams separated by the diffraction grating 4, and an objective that irradiates the optical disk 7 with the light passing through the beam splitter 5 as two light spots. It has a lens 6 and a condensing lens 8 as a condensing means for injecting the two lights reflected by the optical disk 7 through the beam splitter 5. Further, the optical disk device 21 includes a photodetector 9 as a first light receiving means for receiving and photoelectrically converting one of the light beams condensed by the condenser lens 8 and the other of the light beams condensed by the condenser lens 8. It has a photodetector 10 as a second light receiving means for receiving light and photoelectrically converting it. Here, the one light is a main beam and is used as a recording beam,
The other light is a sub beam and is used as a verifying beam.

The optical disk device 21 further includes a main clock generating circuit 15 for generating a reference main clock, a sub-clock generating circuit 11 for receiving the main clock and generating a sub clock, and the photodetector 9.
The first reproducing circuit 12 for generating reproduction data (READ DATA) based on the signal detected by the photodetector, and the second reproducing circuit 13 for generating reproduction data for collation based on the signal detected by the photodetector 10. And a collation circuit 14 for receiving the output of the second reproduction circuit 13 and comparing the recorded data with the reproduction data for collation. The optical disc device 21 supplies recording data to the LD modulation circuit 2 and
It has a control circuit (not shown) for receiving the reproduction data of the reproduction circuit of No. 1 and the collation result of the collation circuit 14.

The main clock is also supplied to the LD modulation circuit 2.

As the optical disk 7, here, Z-
The CAV type shall be used. In Z-CAV, the disk is divided into a plurality of zones in the radial direction, and the data write clock is switched for each zone so that the data density on the disk becomes approximately constant. The frequency of the data channel clock is set higher toward the outer zone. The conventional CAV method has a low recording density on the outer circumference, but the Z-CAV method has an advantage that the storage capacity per disk can be increased because information can be recorded at a high density on the entire disk.

The optical disk 7 is a disk for performing phase change recording as described above. In phase change recording, the irradiation power of laser light is changed to change the state of the medium between a crystalline state and an amorphous state, and marks are formed to record information. At the time of reproduction, a laser beam having a weaker power than that at the time of recording is irradiated, and the mark is detected by the intensity change of the reflected light. Details of phase change recording are introduced in, for example, Japanese Patent Laid-Open No. 4-141827.

Next, the operation of the optical disk device of this embodiment will be described. FIG. 2 is a timing chart of the operation.

The LD modulation circuit 2 drives the laser diode 2 according to the recording data. The light emitted from the laser diode 2 is collimated by the collimator lens 3 and then split into two beams by the diffraction grating 4. Here, a beam that passes straight through the diffraction grating 4 is a main beam, and a beam that is obtained as diffracted light and is inclined to the right side in FIG. 1 is a sub-beam. Here, the light amount ratio k of the main beam and the sub beam is E / k> R, W / k <with respect to the write power W that is the first level, the erase power E that is the second level, and the read power R. It must be chosen so that E holds.

These two beams pass through the beam splitter 5 and are formed by the objective lens 6 on the optical disc 7 at minute intervals in the direction along the track. This beam spacing is the channel bit spacing on the disc d (Z-
Since it is a CAV method, it is almost constant),
It should be about (N + 0.5) × d. However, N
Is a positive integer. That is, the interval between the main beam and the sub beam on the optical disk is an integral multiple of the channel bit interval and its half. This state is shown in FIG. When the main beam 31 is at the channel bit position on the disc, the sub-beam 32 is set to be located between the channel bit positions.

The two beams are reflected by the optical disk 7, pass through the objective lens 6 again, and then the beam splitter 5
Is reflected by the condenser lens 8 and is condensed on the photodetectors 9 and 10 by the condenser lens 8. The reflected light of the main beam enters the photodetector 9, while the reflected light of the sub beam enters the photodetector 10.

At the time of recording data, the LD modulation circuit 2 modulates the recording data in synchronization with the main clock supplied from the outside and changes the laser drive current according to the modulation data. The LD modulation circuit 2 is, for example, as shown in FIG.
The emission power is changed as shown in. In phase change recording, the laser power is controlled in three ways: write power, erase power, and read power. As shown in FIG. 6B, light is emitted with write power at a portion where a mark is to be formed (a portion where the data is “1”) on the disc, and a portion where the mark is not formed (a mark is erased) (when the data is “0”). In the part), the light is emitted with erase power. Here, the period of light emission with write power is centered on the rising edge of the main clock and is less than one clock cycle, for example, about 5
The time is about 0%. Even if "1" continues, a period for returning to the erase power must be provided between them.

The period for emitting light with write power may be the same period as described above centered on the fall of the main clock.

In parallel with this operation, a simultaneous verify operation is performed using the sub beam. In the sub beam, data reproduction is performed in synchronization with the sub clock generated by the sub clock generation circuit 11. The sub clock is
It is assumed that the main clock is inverted as shown in FIG.

The mark previously written by the main beam is detected by the sub beam with a delay of a time difference corresponding to the interval between the two beams (FIG. 7 (d)). However, since the light sources of the sub-beam and the main beam are the same laser diode, the intensity of the sub-beam is also modulated in synchronization with the write data, and the reproduction signal by the sub-beam shows the mark on the disc and its mark as shown in FIG. It will be modulated by both of the write data at that time. For example, in the part (1) of FIG. 6D, the reproduction signal of the verify beam is detected by the sub-beam after being delayed by the beam interval from the component due to the light power emission of the laser at that time (FIG. 6B). Is modulated by the component due to the mark on the disc.

However, since the write power emission period is set to about 50% of the main clock cycle and the main clock and the sub clock have opposite phases, the rising portion of the sub clock (the portion marked with a circle in FIG. 2D). ), The laser always emits with erase power. Further, since the interval between the main beam and the sub beam is set to (N + 0.5) × d, the identification point (data position) of the signal reproduced by the sub beam coincides with the rising edge of the sub clock. Therefore, if the data is reproduced at the rising edge of the sub clock, the data written on the disc can be correctly reproduced.

If the light emission period of the write power is a period centered on the falling edge of the main clock, then if the data is reproduced at the falling edge of the sub clock, the data can be correctly reproduced in the same manner.

In this way, the verifying operation for confirming whether or not the writing is correctly performed can be performed by comparing and verifying the data reproduced by the sub beam and the recorded data by the verifying circuit 14. Verify
It may be checked whether the reproduction result by the sub beam and the recorded data match for each channel bit, or whether the write data before modulation and the result of demodulating the reproduction result match. Alternatively, even when the two do not completely match, it is possible to consider that the writing has been normally completed if the difference is such that it can be sufficiently corrected by using the error correction function.

In the normal data read operation, the laser is emitted so that the main beam has the read power,
Data may be reproduced by the first reproducing circuit 12.

As described above, according to this embodiment, the interval between the main beam and the sub beam is (N + 0.5) × d (where N is a positive integer and d is the bit interval on the disc),
At the time of writing, the period during which the erase power is increased to the write wiper is about half of the channel clock period, and the data is reproduced by the sub-beam in synchronization with the clock that is out of phase with the main beam. Therefore, the data for verification is reproduced with the erase power, and is not affected by the optical modulation at the time of writing the data. Therefore, the simultaneous verification using the single light source and the optical modulation recording method can be accurately performed without gain adjustment and the like, and the data writing speed including the verification can be dramatically improved.

Although the inverted clock of the main clock is used as the sub clock when reading the verify reproduction signal in this embodiment, the main clock may be delayed to be used as the sub clock. In that case, the delay time Δt
May be Δt = Δx / v. Here, Δx is the distance between the main beam and the sub beam, and v is the linear velocity of the disc. The linear velocity v is different between the inner circumference and the outer circumference of the disc, but since the radial position can be known if the track number is known, the linear velocity can be obtained by multiplying the disc rotation speed [rad / s] by the radius [m]. A programmable delay line or the like can be used to set the delay time.

4 and 5 relate to the second embodiment of the present invention, FIG. 4 is a block diagram of the optical disk device, and FIG. 5 is a timing chart for explaining the appropriateness of the arrangement relationship between the main clock and the sub clock. Is.

In the first embodiment, the case of so-called continuous servo has been described, but this embodiment is an example applied to the case of the sample servo system.

A disk format called the Z-CAV method, which is the sample servo method, is disclosed in, for example, Japanese Patent Laid-Open No. 3-2.
The details are introduced in Japanese Patent No. 54471. This divides the disk into zones in the radial direction, and the channel clock for servo is constant in all zones, but the channel clock for data is switched for each zone, and the density of data on the disk becomes approximately constant. To do so. Since the disk is rotated at a constant rotation speed, the frequency of the data channel clock becomes higher toward the outer zone.

In the case of the sample servo system, a channel clock, which is a reference clock for operation, is reproduced with reference to a specific pit called a clock pit as a unique mark provided on the disk. Since the details of the clock reproducing method are known, the description thereof will be omitted.

The structure of the optical disk device is as shown in FIG. The optical disk device 25 shown in FIG. 4 includes a main clock reproducing circuit 26 for reproducing a main clock based on the detection signal of the photodetector 9 and a subclock for reproducing a subclock based on the detection signal of the photodetector 10. It has a reproducing circuit 27. Main clock recovery circuit 2
The main clock reproduced by 6 is supplied to the LD modulation circuit 2 and the second reproduction circuit 12. In addition, the subclock regenerated by the subclock regeneration circuit 27 is the first subclock.
Is supplied to the reproduction circuit 13 of FIG. Other configurations and operations similar to those of the first embodiment are designated by the same reference numerals and description thereof will be omitted.

The optical disk device 25 is configured to reproduce the main clock from the reproduction signal of the main beam and generate the sub clock from the sub beam.
Both clocks are generated independently of each other, but the interval between the main beam and the sub beam is (N + 0.5) × d (where N
Is a positive integer, and d is a bit interval on the disk), the main clock and the sub clock have approximately opposite phases.

In the sample servo method, as a method of binarizing the read waveform, the reproduction signal level is sampled in accordance with the clock, and the difference detection for binarizing is performed from the distribution thereof. For example, in the format called DBF, 4/11 modulation is used, but this is a modulation method in which the number of "1" s in one byte is always 4, and four bits with large levels are sampled from the reproduction signal sampling result. Binarization can be performed by selecting. In this way, the difference detection method used in the sample servo is
Originally, if the reproduction signal level at the identification point (rising position of the reference clock) is obtained, the binarization can be surely performed. Therefore, the optical disk device of the present invention can obtain better results when applied to the sample servo system.

Of course, also in this case, the sub clock may be generated by delaying the main clock. The amount of delay may be determined by calculating the linear velocity based on the track number as described above, or by setting the time as the amount of delay by measuring the difference in time at which clock pits appear. You may do it.

As described above, according to the present embodiment, the simultaneous verification in the light modulation recording system using a single light source is possible even in the sample servo system without gain adjustment or the like.

By the way, the longer the distance between the main beam and the sub beam, the easier the separation in the photodetector.
In addition, if the distance is extremely short, the sub beam may read the mark before the mark is completely formed, and thus an error is likely to occur. From this point of view, it is advantageous to set the beam interval to a certain length. However, even in the Z-CAV system, since the linear velocities are slightly different between the inner circumference and the outer circumference in the zone, the phase difference between the main clock and the sub clock changes between the inner circumference and the outer circumference. When the timing is fixed by using the sub clock as the reverse phase clock of the main clock, the rising edge of the sub clock and the actual data position are slightly deviated between the inner circumference and the outer circumference.
This state is shown in FIG.

If the reference position is set at a position where the main clock shown in FIG. 5A and the subclock shown in FIG. 5C are in opposite phase, the linear velocity becomes smaller on the inner peripheral side than that. For this reason, the time difference until the sub beam reads the mark written by the main beam becomes large,
The phase of the sub clock will be delayed by that amount. If the delay amount becomes too large, as shown in FIG. 5 (f), the rising edge of the sub-clock and the light emission period of the main beam shown in FIG. 5 (e) will overlap, making simultaneous verification impossible. Note that FIG. 5B shows the light emission period at the reference position.

Since the fluctuation of the phase between the two clocks appears more prominently as the distance between the beams becomes longer, the narrower the beam interval is, the better from this viewpoint. Therefore, as a concrete example, it is considered that about 10 μm is suitable as the beam interval. If the beam spacing is within this range, the fluctuation of the phase difference within the zone does not matter.

In the above embodiment, the case of the phase change recording system is explained. However, even in the magneto-optical recording system, if the laser power is always returned to a constant value near the fall of the channel clock at the time of recording, The present invention can be applied.

The format of the optical disk is ZC.
The present invention can be applied to any method other than the AV (M-CAV) method as long as the recording linear density is substantially constant, for example, the CLV method or the M-CLV method.

When the recording linear density greatly differs between the inner circumference and the outer circumference as in the CAV method, the beam interval on the disk is changed according to the change in the linear velocity by, for example, moving the position of the diffraction grating. Then, the present invention can be applied.

[0049]

As described above, according to the optical disk device of the present invention, the beam from the single light source is divided into the main beam and the sub beam, and the interval between the main beam and the sub beam is (N + 0.5) × d (however, N is a positive integer, d is a bit interval on the disc), and the second
The period for increasing the level from the first level to the first level is set to about half of the channel clock period, and the data for the verify operation is reproduced because the data for the verify operation is reproduced by the sub-beam in synchronization with the clock that is almost in antiphase with the main beam. Is reproduced by the light emitted at the second level,
It is completely unaffected by light modulation when writing data.
Therefore, according to the present invention, it is possible to perform simultaneous verification in a light modulation recording method using a single light source without gain adjustment or the like, and it is possible to dramatically improve the data writing speed including verification. effective.

[Brief description of drawings]

FIG. 1 to FIG. 3 relate to a first embodiment, and FIG. 1 is a configuration diagram of an optical disk device.

FIG. 2 is a timing chart of the device shown in FIG.

FIG. 3 is an explanatory diagram showing a positional relationship between a main beam and a sub beam.

4 and 5 relate to a second embodiment, and FIG. 4 is a configuration diagram of an optical disk device.

FIG. 5 is a timing chart for explaining the appropriateness of the arrangement relationship between the main clock and the sub clock.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser diode 2 ... LD modulation circuit 7 ... Optical disk 9, 10 ... Detector 11 ... Sub clock generation circuit 12 ... 1st reproduction circuit 13 ... 2nd reproduction circuit 14 ... Collation circuit 31 ... Main beam 32 ... Sub beam d ... Channel bit interval N ... Positive integer

Claims (3)

[Claims] 1. An optical disk device for recording information on an optical disk so that the recording linear density is substantially constant along an information track, and first and second clocks having the same frequency but opposite phases. A first clock generating means and a second clock generating means, a modulating means for generating a drive signal synchronized with the first clock according to information to be recorded, and a light source driven by the modulating means, Ray splitting means for splitting the light emitted from the light source into at least two of a main beam and a sub beam; a main beam and a sub beam split by the ray splitting means on the information track; and d on the information track. And a condensing means for condensing and irradiating at intervals of about (N + 0.5) × d when N is an arbitrary integer. A first light receiving unit and a second light receiving unit that receive the reflected light of the main beam and the reflected light of the sub beam from the optical disk are provided, and when recording information, the modulating unit causes the first clock to rise or rise. The light source is caused to emit light at a first level at which a mark is to be formed with a time width of less than one clock cycle centered on the fall, and at a second level which is substantially a regulated level in other periods, and at a second level. An optical disk device, wherein information is recorded by the main beam, and at the same time, information is reproduced based on the output of the second light receiving means in accordance with the second clock to collate the recorded data. 2. A unique mark is intermittently provided in advance on the information track, and the first clock generating means outputs the first clock from the unique mark by the output of the first light receiving means. 2. The optical disk device according to claim 1, wherein the second clock generating means reproduces the second clock from the unique mark by the output of the second light receiving means while reproducing. 3. The main beam and the sub beam are generated by delaying the second clock with respect to the first clock by a time difference for irradiating the same point on the information track. Claim 1 characterized
2. The optical disk device according to item 2 or 3.