JP2002063721A - Optical information recording method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the width in the radial direction of an optical disk of a pit to be formed from unnecessarily becoming large even when the diameter of a beam spot is larger with respect to a track pitch of the optical disk. SOLUTION: The pit longer than the spot diameter of the beam spot formed on the recording surface of the optical disk by a laser beam is formed, and an RF signal is obtained from this pit, then a recording pulse is corrected so that a bottom level of this RF signal becomes constant, i.e., so that the signal level at a point (a) representing the time point whereon the beam spot of the RF signal waveform is saturated with the pit, becomes equal to the signal level at a point (b) representing the time point whereon the pit beings to get out from the beam spot.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording method and an optical information recording apparatus, and more particularly to an optical information recording method and an optical information recording apparatus for preventing a pit width of an optical disk from increasing in a radial direction.

[0002]

2. Description of the Related Art At present, the thickness of a disc and the wavelength of a laser used remain the same as the CD standard, and the CD-R (Compact Disc Recorder)
dable) that enables higher density recording than
R (DDCD-R) is being developed.

Here, generally, in order to achieve a high density of an optical disk, it is necessary to realize two points of 1) high density in a linear velocity direction and 2) high density in a track pitch direction.

For this reason, for example, a DVD (Digital Vers.
atile Disc) and DVD-R (DVD-Recordable)
In (2), the disc thickness is set smaller than that of the CD standard (disc thickness: 1.2 mm, laser wavelength used: 780 nm).
6 mm) and short wavelength laser light (wavelength 635-660)
nm), the diameter of the beam spot formed by the laser beam on the recording surface is reduced, thereby realizing the above two densities.

[0005]

However, a high-density CD
In the -R, the first consideration is compatibility with existing CD-Rs. Therefore, in order to make the system cheaper without largely changing the current CD-R, the disk thickness and laser wavelength are not changed. It is necessary to cope with this by making the laser spot slightly smaller.

Accordingly, in a high-density CD-R, even if the laser spot is slightly narrowed, the minimum pit size for the laser spot is smaller than that of the CD-R.

Further, compared to CD-R, high density CD-R
In, the width of the pit becomes relatively large with respect to the track pitch, and the following problem occurs.

(1) Crosstalk due to pits in an adjacent track increases, and the jitter of a reproduced signal increases.

(2) Since the crosstalk due to the pits of the adjacent track increases and the pit width of the main track increases, the jitter of the wobble signal increases, and the reading accuracy of the absolute time information (ATIP) deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problem, and when a beam spot has a larger diameter than a pit to be formed, the width of the pit formed by the beam spot is determined by using a recording pulse. It is an object of the present invention to prevent this by controlling and improve the accuracy of a reproduced signal.

The present invention is applicable not only to high-density CD-Rs but also to CD-Rs and DVD-Rs.

[0012]

In order to achieve the above-mentioned object, the present invention provides a method of irradiating a laser beam corresponding to a recording pulse along a recording track of an optical disk to thereby record the recording pulse on the recording track of the optical disk. In the optical information recording method for forming a pit having a length corresponding to the pulse width of the pit, the output energy of the laser beam corresponding to the pit is controlled to be smaller at least at the central portion in the recording track direction of the pit than at other portions. Thus, the width of the pit in a direction orthogonal to the recording track direction is controlled to be substantially constant.

As a method of forming a laser beam in which the output energy is controlled to be smaller at least at the central portion in the recording track direction than at other portions, (1) the recording pulse corresponding to the pit is decomposed into a plurality of pulses. (2) controlling the duty ratio at least in the central portion of the multi-pulse to be smaller than that of other portions, and modulating the laser beam based on the controlled multi-pulse. (2) The recording pulse corresponding to the pit Is divided into a plurality of pulses to form a multi-pulse, a level of at least a central portion of the multi-pulse is controlled to be smaller than other portions, and a method of modulating the laser beam based on the controlled multi-pulse is provided.

Further, according to the present invention, a recording pulse corresponding to each pit is divided into a plurality of pulses, and a laser beam is modulated by the multi-pulse as a multi-pulse. In an optical information recording method of forming a pit having a length corresponding to the recording pulse on a recording track of the optical disk by irradiating, a pulse other than a pulse interval between a last pulse of the multipulse and a pulse immediately before the multipulse. By controlling the interval to a correction pulse interval wider than the pulse interval between the last pulse and the pulse immediately before the last pulse, a method of controlling the width of the cut in a direction orthogonal to the recording track direction to be substantially constant. provide.

Here, the control method of the correction pulse interval is as follows: (1) A read signal corresponding to a predetermined pit is obtained from an optical disk in which pits are formed in advance, and the peak portion of the amplitude of the read signal is substantially flat. (2) detecting a read signal corresponding to a predetermined pit and a crosstalk signal thereof from an optical disk in which pits are formed in advance, and detecting the amplitude of the crosstalk signal with respect to the amplitude of the read signal. A method for controlling the correction pulse interval so that the ratio of the correction pulses falls within a range of a predetermined value set in advance.

According to the present invention, a pit having a length corresponding to the pulse width of the recording pulse is formed on the recording track of the optical disk by irradiating a laser beam corresponding to the recording pulse along the recording track of the optical disk. The optical information recording apparatus according to claim 1, further comprising control means for controlling the output energy of the laser beam corresponding to the pit to be smaller at least at the center of the pit in the recording track direction than at other portions.

Here, the control means includes a multi-pulse generation means for decomposing the recording pulse corresponding to the pit into a plurality of pulses to generate a multi-pulse, and a means for adjusting a pulse interval of the multi-pulse. Or
Multi-pulse generation means for decomposing the recording pulse corresponding to the pit into a plurality of pulses to make a multi-pulse,
Means for adjusting the level of the multi-pulse.

A recording pulse corresponding to each pit is divided into a plurality of pulses, and a laser beam is modulated by the multi-pulse as a multi-pulse, and the modulated laser beam is irradiated from an optical pickup along a recording track of an optical disk. A recording pit having a length corresponding to the recording pulse on a recording track of the optical disk, wherein the optical pickup uses a predetermined pit from an optical disk in which pits are previously formed by the optical pickup. And a control means for controlling the correction pulse interval such that a peak portion of the amplitude of the read signal read by the read means becomes substantially flat. Recording pulse generator.

Further, a recording pulse corresponding to each pit is divided into a plurality of pulses, and a laser beam is modulated by the multi-pulse as a multi-pulse, and the modulated laser beam is irradiated from an optical pickup along a recording track of an optical disk. A recording pit having a length corresponding to the recording pulse on a recording track of the optical disc by a recording pit generating circuit in the optical information recording apparatus. Reading means for reading a read signal corresponding to the above, detecting means for detecting, by the optical pickup, a crosstalk signal corresponding to the read signal read by the reading means, and detecting the amplitude of the read signal read by the reading means Clost detected by means Recording pulse generating apparatus characterized by comprising control means the ratio of the click signal amplitude to control the correction pulse interval to be within the range of a preset predetermined value.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an optical information recording method and apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

Generally, an optical disk such as a CD-R has a basic structure in which a recording layer made of an organic dye film is provided on a transparent substrate provided with spiral recording tracks, and a reflective layer is further provided thereon. This type of optical disk rotates at a constant linear velocity and irradiates a laser beam along the recording track of the recording layer from the transparent substrate side to form a pit row corresponding to recording information on the recording track.
Information is recorded on the optical disc.

When recording information, a laser beam is irradiated corresponding to a recording pulse generated based on the recording information. For example, when the recording pulse is at a high level, the laser beam is irradiated with a high intensity to irradiate the recording layer of the optical disk. A pit is formed on the recording track by altering the recording track, and when the reference recording pulse is at a low level, irradiation is performed at a low intensity to perform servo control such as tracking of the recording track without altering the recording layer of the optical disc.

However, if a high-intensity laser beam is uniformly irradiated during the high-level period of the recording pulse, that is, during the pit forming period, the formed pits are distorted due to the influence of the excess heat accumulated in the recording layer.

Therefore, a method is used in which each recording pulse is constituted by a multi-pulse composed of several small pulses, and the amount of energy supplied by laser beam irradiation is controlled.

The basic one of the multi-pulse is, for example,
From a rectangular recording pulse serving as a reference corresponding to the recording information as shown in FIG. 1A, a pulse having a width of less than 1T follows a leading pulse having a width of 3T as shown in FIG. 1B. The configuration is such that they are periodically arranged at intervals so as to be 1T in total. By turning on and off the laser beam in synchronism with the multi-pulse, the amount of energy supplied to the recording layer of the optical disk is adjusted, so that excess heat is prevented from accumulating in the recording layer and distortion in the formed pits is prevented. prevent.

Turning the laser beam on and off means that the laser beam is divided into two stages: high power (ON) for forming pits and low power (OFF) for performing servo control such as tracking without forming pits. Switching of beam output.

Further, there is a method of controlling the amount of energy supplied by laser beam irradiation by changing the level of each recording pulse.

In this method, for example, the level of the leading part of a recording pulse of a fixed level as shown in FIG.
By setting it high as shown in (c), it is used for the purpose of, for example, steep rise of the thermal response of the recording layer of the optical disc to prevent displacement of the leading edge of the pit.

The present invention provides a correction pulse effective for forming a pit having a constant width in the radial direction of an optical disk, and a method of generating such a correction pulse.

First, a correction pulse effective for controlling the pit width of the optical disk in the radial direction to be constant will be described.

(First Correction Pulse) This correction pulse is
It is characterized in that the pulse interval at the center of the multipulse is set to be long.

That is, as shown in FIG. 2A, the pulse interval other than the interval between the last pulse of the multi-pulse and the pulse immediately before it is set longer (the OFF time is longer and the ON time is shorter).

That is, in order to maintain the correspondence with the recording pulses, the pulse width of the pulses other than the foremost pulse and the last pulse is narrowed (widened) by the amount of the pulse interval being widened (narrowed). Thus, the length of the entire multi-pulse is not changed.

According to such a multi-pulse, FIG.
As shown in (d), the front edge and the rear edge portions are firmly formed, pits having a small width at the middle portion can be formed, and the pit width in the radial direction of the optical disc can be prevented from spreading. .

(Second Correction Pulse) This correction pulse is
It is characterized in that the level of the pulse at the center of the multipulse is set low.

That is, as shown in FIG. 2B, the levels of the pulses other than the frontmost and last pulses of the multi-pulse are set lower than the levels of the frontmost and last pulses. .

With such a multi-pulse, FIG.
An effect similar to that of the multi-pulse shown in FIG.
As shown in (d), the front edge portion and the rear edge portion are firmly formed, and a pit having a small width at the middle portion can be formed.

(Third Correction Pulse) This correction pulse is
It is characterized in that the level at the center of the recording pulse is set low.

That is, as shown in FIG. 2 (c), by generating a pulse having a concave portion at the center, the pulse shown in FIG.
2C, the same effect as that of the multi-pulse shown in FIG. 2C can be obtained. As shown in FIG. 2D, the leading edge and the trailing edge are formed firmly, and the pit having a small width at the middle is formed. Can be formed.

Next, a specific example of a recording pulse correction method for generating the above-described correction pulse will be described.

(First Correction Method) FIG. 3 is a diagram showing the basic concept of this embodiment.

Generally, the amount of return light when irradiating a pit with a laser beam is smaller than the amount of return light when irradiating a land. Therefore, a laser spot formed on an optical disk by irradiation of a laser beam has a smaller intensity. The light amount of the return light changes depending on the ratio of the pits, and an RF signal is generated based on the change in the light amount.

Therefore, if the pit width in the radial direction of the optical disk is constant, the level of the RF signal changes only when the pit edge passes through the beam spot, as shown in FIG. The RF signal takes a constant value when it is saturated by a pit longer than its own diameter in the pit longitudinal direction.

However, as shown in FIG. 3B, when the width of the pit in the radial direction of the optical disk fluctuates due to the influence of excess energy or the like, the beam spot is saturated by the pit longer than its own diameter in the pit longitudinal direction. Also, the level of the RF signal fluctuates according to the fluctuation amount of the pit width in the radial direction of the optical disk.

This embodiment provides a method for correcting a recording pulse and generating the above-described correction pulse by utilizing such a phenomenon.

FIG. 4 is a diagram showing a configuration of a recording pulse generating apparatus according to this embodiment. FIG. 5 is a flow chart for explaining a flow of a pulse interval adjusting method of a multi-pulse in the recording pulse generating apparatus shown in FIG. is there.

In the optical information recording / reproducing apparatus shown in FIG. 4, first, a recording pulse corresponding to a pit (for example, 11T pit) longer than the spot diameter is input to the multi-pulse generation circuit 12.

The multi-pulse generation circuit 12 stores an initial set value for converting the input recording pulse into a multi-pulse. For the time being, based on the initial set value, the recording corresponding to the input 11T pit is performed. Multi-pulse the pulse.

The LD driver 11 controls a laser diode (not shown) included in the optical pickup 10 based on the multi-pulse generated by the multi-pulse generation circuit 12 to irradiate a laser beam in a test writing area of the optical disk 2 to generate an 11T laser beam. Form pits (Step 40)
1).

Then, the RF signal reproducing unit 13 reproduces the RF signal from the information read from the pit formed in step 401 by the optical pickup 10 (step 402).

The level comparing section 14 is provided with the RF signal reproducing section 13
The RF signal level of the point a indicating the time when the beam spot is saturated with the pit and the point b indicating the time when the pit starts to escape from the beam spot in the RF signal waveform input from the step 403 are detected (step 403). It is determined whether or not the RF signal level at the point = the RF signal level at the point b (step 404), and the RF signal level at the point a ≠ b
If the RF signal level of the point is (NO in step 405), the pulse interval correction instruction signal is sent to the multi-pulse generation circuit 1
2 and upon receiving the pulse interval correction instruction signal, the multi-pulse generation circuit 12 generates a correction value obtained by correcting the initial setting value, and based on the correction value, 11T
The recording pulse corresponding to the pit is multi-pulsed.

The above operation is repeated, and when the RF signal level at point a = the RF signal level at point b (step 40)
5) (YES), the multi-pulse generation circuit stores the correction value at that time, and converts the recording pulse into a multi-pulse based on the input recording information based on the correction value.

It should be noted that exactly "RF signal level at point a = b
It is difficult to adjust the RF signal level at the point “a”, so that the difference between the RF signal level at the point a and the RF signal level at the point b is smaller than a predetermined value, The recording pulse is corrected so that the ratio between the signal level and the RF signal level at point b takes a value within a predetermined range centered at 1.

Although the method of using the test writing area of the optical disk has been described here, the above-described adjustment is performed in advance for each optical disk or optical pickup, and the set value is stored in the memory of the optical disk recording apparatus. Is also good.

(Second Correction Method) FIG. 6 is a diagram showing the basic concept of this embodiment.

In general, before starting to record information on an optical disc, a PCA provided on the innermost circumference of the optical disc is used.
OPC (Optical Power Cont) for finding the optimum recording power of the laser beam for each temperature and each optical disc in an area called (Power Caliblation Area)
rol), and the optimum recording power of the laser beam is determined based on the result of the OPC.

More specifically, test writing is performed by changing the recording power by a certain step, and the area in which the test writing is performed is reproduced to calculate an asymmetry value (an index indicating the asymmetry of the RF signal) to obtain an optimum asymmetry value. Is determined as the optimum recording power.

The asymmetry value particularly depends on the accuracy of the pit edge. That is, the OPC adjusts the recording power of the laser beam so that a pit having an optimum length can be formed in the track direction. However, the width of the pit in the radial direction of the optical disk is not considered.

Therefore, in this embodiment, the above O
After the optimum recording power of the laser beam is determined by the PC, a recording pulse correction method for further optimizing the pit width in the radial direction of the optical disk is provided.

FIG. 7 is a diagram showing a configuration of a recording pulse generating apparatus according to this embodiment. FIG. 8 is a flow chart for explaining a flow of a method of adjusting a pulse interval of a multi-pulse in the recording pulse generating apparatus shown in FIG. is there.

First, the optimum recording power is set by OPC (step 601).

Next, the multi-pulse generating circuit 12 converts the input recording pulse into a multi-pulse based on a preset initial value for converting the recording pulse into a multi-pulse. The laser diode (not shown) of the optical pickup 10 is controlled with the optimum recording power set based on the multi-pulse generated by the pulse generation circuit 12 to form an appropriate series of pit rows in the PCA area of the optical disk (step 60).
2).

Next, the PCA is
The information of the area is read, and the RF signal reproducing unit 13 is read.
Reproduces the RF signal S1 of the recording track 51 in which the pit train is formed and the RF signal S2 of the unrecorded track 52 adjacent to the recording track 51 where no pit is formed from the information read by the optical pickup 10 ( Steps 603 and 604).

Here, the RF signal S2 obtained by reproducing the unrecorded track 52 is
2 is detected because the spot 53 that scans 2 reads a part of the pits formed on the adjacent recording track 51. Therefore, the RF signal S
2 can be said to be the crosstalk component itself from the adjacent track.

That is, if the width of the pits formed in the recording track 51 in the radial direction of the optical disk is appropriate, the value of the RF signal S2 should be zero unless a part of the spot 53 leaks into the recording track 51. is there.

However, in an ordinary optical disk recording apparatus, since a part of a spot for scanning a desired recording track often leaks to an adjacent track, the RF signal S
The value of 2 never goes to zero.

Therefore, the amplitude comparing section 15 outputs the RF signal S2
Is calculated (step 605). If the result of the calculation is equal to or larger than a predetermined value (YES in step 605), the radius of the optical disk of the pit formed on the recording track 51 is determined. It determines that the width in the direction is large, and outputs a pulse interval correction instruction signal to the multi-pulse generation circuit 12.

When receiving the pulse interval correction instruction signal from the amplitude correction unit 15, the multi-pulse generation circuit 12 generates a correction value obtained by correcting the initial setting value, and converts the input recording pulse based on the correction value into a multi-pulse. (Step 606).

[0069]

As described above, according to the present invention, even when the diameter of the beam spot is larger than the pit to be formed, the width of the pit formed by the beam spot is increased, and the recording pulse is generated. Since this can be prevented by controlling, there is an effect that the quality of the reproduced signal is improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a basic correction pulse.

FIG. 2 is a diagram showing an example of a correction pulse according to the present invention.

FIG. 3 is a diagram showing an example of a recording pulse correction method according to the present invention.

FIG. 4 is a diagram showing an example of a recording pulse correction device for performing the recording pulse correction method shown in FIG.

FIG. 5 is a flowchart illustrating a flow of a recording pulse correction method illustrated in FIG. 3;

FIG. 6 is a diagram showing an example of a recording pulse correction method according to the present invention.

FIG. 7 is a diagram showing an example of a recording pulse correction device for performing the recording pulse correction method shown in FIG.

FIG. 8 is a flowchart illustrating a flow of a recording pulse correction method illustrated in FIG. 6;

[Explanation of symbols]

 Reference Signs List 10 optical pickup 11 driver 12 multi-pulse generating circuit 13 signal reproducing unit 14 level comparing unit 15 amplitude comparing unit 15 amplitude correcting unit 2 optical disk 51 recording track 52 unrecorded track 53 beam spot

Claims (9)

[Claims] 1. An optical information recording device, comprising: irradiating a laser beam corresponding to a recording pulse along a recording track of an optical disk to form a pit on the recording track of the optical disk having a length corresponding to the pulse width of the recording pulse. In the method, the width of the pit in a direction perpendicular to the recording track direction is reduced by controlling the output energy of the laser beam corresponding to the pit to be smaller than at least a central portion of the pit in the recording track direction than other portions. An optical information recording method, wherein the optical information recording method is controlled to be constant. 2. The method according to claim 1, wherein the recording pulse corresponding to the pit is decomposed into a plurality of pulses to form a multi-pulse, and a duty ratio in at least a central portion of the multi-pulse is controlled to be smaller than other portions. 2. A laser beam whose output energy is controlled to be smaller at least at a central portion in the recording track direction than at other portions by modulating the laser beam based on the laser beam.
The optical information recording method described in the above. 3. The recording pulse corresponding to the pit is decomposed into a plurality of pulses to form a multi-pulse, a level of at least a central portion of the multi-pulse is controlled to be smaller than that of another portion, and based on the controlled multi-pulse. 2. The laser beam according to claim 1, wherein the laser beam is modulated to form a laser beam whose output energy is controlled to be smaller at least at a central portion in the recording track direction than at other portions.
The optical information recording method described in the above. 4. A recording pulse corresponding to each pit is divided into a plurality of pulses, and a laser beam is modulated by the multi-pulse as a multi-pulse, and the modulated laser beam is irradiated along a recording track of an optical disk. In an optical information recording method for forming a pit having a length corresponding to the recording pulse on a recording track of the optical disc, a pulse interval other than a pulse interval between a last pulse of the multi-pulse and a pulse immediately before the multi-pulse is set as By controlling the correction pulse interval to be wider than the pulse interval between the last pulse and the immediately preceding pulse, the width of the bit in the direction orthogonal to the recording track direction is controlled to be substantially constant. Information recording method. 5. A read signal corresponding to a predetermined pit is obtained from an optical disk on which pits have been formed in advance, and the correction pulse interval is controlled so that the peak portion of the amplitude of the read signal becomes substantially flat. The optical information recording method according to claim 4, wherein 6. A read signal corresponding to a predetermined pit and a crosstalk signal thereof are detected from an optical disk in which pits have been formed in advance, and a ratio of the amplitude of the crosstalk signal to the amplitude of the read signal is set to a predetermined value. 5. The correction pulse interval is controlled so as to fall within the range of
The optical information recording method described in the above. 7. A recording pulse corresponding to each pit is divided into a plurality of pulses, and as a multi-pulse, a laser beam is modulated by the multi-pulse and the modulated laser beam is irradiated along a recording track of an optical disk. In an optical information recording apparatus for forming a pit having a length corresponding to the recording pulse on a recording track of the optical disc, a pulse interval other than a pulse interval between a last pulse of the multi-pulse and a pulse immediately before the multi-pulse is set to Multi-pulse control means for controlling the correction pulse interval larger than the pulse interval between the last pulse and the pulse immediately before the last pulse to control the width of the cut in the direction orthogonal to the recording track direction substantially constant. An optical information recording device characterized by the above-mentioned. 8. A recording pulse corresponding to each pit is divided into a plurality of pulses, a laser beam is modulated by the multi-pulse as a multi-pulse, and the modulated laser beam is irradiated from an optical pickup along a recording track of an optical disk. A recording pit having a length corresponding to the recording pulse on a recording track of the optical disc by the optical pickup; And a control means for controlling the correction pulse interval so that the peak portion of the amplitude of the read signal read by the read means becomes substantially flat. Recording pulse generator. 9. A recording pulse corresponding to each pit is divided into a plurality of pulses, and a laser beam is modulated by the multi-pulse as a multi-pulse, and the modulated laser beam is irradiated from an optical pickup along a recording track of an optical disk. A recording pit having a length corresponding to the recording pulse on a recording track of the optical disc by a recording pit generating circuit in the optical information recording apparatus. Reading means for reading a read signal corresponding to the above; detecting means for detecting, by the optical pickup, a crosstalk signal corresponding to the read signal read by the reading means; and detecting the amplitude of the read signal read by the reading means. Crosstalk detected by means Control means for controlling the correction pulse interval so that the signal amplitude ratio falls within a range of a predetermined value set in advance.