JPH08221786A - Recording waveform control method - Google Patents

Abstract

PURPOSE: To prevent a recording light pulse output from fluctuating due to return light by sampling a bias light level when high frequency superimposition being a recording rest section between recording pulses is turned off and controlling so that the bias light level becomes a target value. CONSTITUTION: In a bottom level part/recording level part 16 a sample and hold circuit 12 operating only when the high frequency superimposition to a laser drive circuit is turned off samples bias light by a bias current by a backward or forward monitor 11, and the bias light is compared with the setting bottom power of the target value by a differential circuit 13. Then, the monitored bias light is feedback-controlled so as to become the target value, and it becomes a low power state in a recording rest period, and such a situation that a laser output is affected by the return light, is prevented, and no temp. distribution on a disk by recording irradiation is changed, and the lowering in an S/N due to dispersion of a recording mark is suppressed.

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 / reproducing method and apparatus for recording / reproducing information on / from an optical recording medium using a laser beam.

[0002]

2. Description of the Related Art Conventionally, in an optical disk device, there has been a problem that the return light laser noise due to the formation of an external resonator between the disk surface and the single mode laser end surface lowers the read SN ratio during data reproduction. This laser noise increases particularly in reproduction when the optical output is at the threshold value of the laser.

As a method of solving this problem, a high SN has been realized by reducing the laser noise by superimposing a high frequency on the laser drive circuit in accordance with the amount of the optical path of the external resonator to form a pseudo multimode. Further, at the time of recording, since the laser output becomes high, the return light noise becomes small.
Therefore, when the maximum output of the laser is required as in recording, the high frequency superposition is turned off, and when the laser output has a margin, the high frequency superposition is turned on and the recording pulse current is applied.

[0004]

In the above-mentioned conventional example, since the high frequency superimposition is not applied during recording, the level between the recording pulse and the next recording pulse, that is, the rest period of the recording pulse is DC bias. This is a low power output state determined by the current and is affected by the returning light, so the optical output fluctuates. Further, when recording with the high frequency superimposition turned on, the high frequency superimposition is added to the recording pulse with the same amplitude and frequency values as during reproduction. Since the intensity is different from that at the time of reproduction, the wavelength and the degree of modulation to be superimposed are different from those at the time of reproduction, and the return light noise may be reduced. Therefore, it is impossible to completely suppress the fluctuation of the recording mark due to the influence of the return light noise during recording.

An object of the present invention is to solve the above problems and reduce the influence of return light laser noise even during recording,
It is another object of the present invention to provide an optical disc recording / reproducing method for forming a stable recording mark having a high SN ratio.

[0006]

Means for Solving the Problems A bias light level due to a bias current when high frequency superimposition is turned off is monitored and controlled to a target value. Alternatively, information is recorded on a recording medium using a comb-shaped laser pulse waveform,
Information is reproduced by irradiating a recording medium with a laser beam of approximately DC level by reflected light from the medium, and a high frequency is superposed on a driving current of a semiconductor laser at the time of reproducing, and a high frequency is not superposed on a driving current of a semiconductor laser at a recording time. During reproduction, the DC level is controlled to be maintained at a predetermined value, and during recording, the level between the comb teeth of the laser pulse waveform is controlled to be maintained at a predetermined value. Further, high frequency superposition is applied even during recording, and the superposition amplitude and frequency during reproduction are changed. That is, the method of superimposing high frequencies is changed at the time of recording, reproducing, erasing, or the like.

[0007]

Since the output of the recording light pulse does not change due to the returning light, the temperature distribution on the disk does not change due to the irradiation of the recording light. Therefore, it is possible to prevent a decrease in SN of the reproduced signal due to variations in the shape and size of the recording mark.

[0008]

EXAMPLE FIG. 1 shows an example of the present invention.

FIG. 1A shows a laser drive circuit. It consists of multi-channel D / A converters 2, 3, 4, 5 and current switches 6, 7, 8, 9 and drives the laser 1 with these current addition signals to generate multi-valued optical pulse waveforms. . The high frequency generation circuit 10 drives the semiconductor laser 1 with a drive current on which a high frequency is superimposed to reduce noise. It is possible to control ON / OFF of the high frequency by the recording gate signal, and for example, it is possible to superimpose the high frequency only during reproduction. Here, as the optical recording waveform control method including the optical pulse waveform irradiated at the time of recording, the method described in JP-A-6-84224 was used.

FIG. 2 shows a recording waveform control method described in JP-A-6-84224. The recording light is composed of optical pulses having multi-valued levels of Pw1, Pw2, Pas, and Pr, and Pas is controlled in order to reduce the fluctuation of the recording mark due to the change in the environmental temperature of the device during data recording. As described in Japanese Patent Laid-Open No. 6-84224, before recording user data at the target recording position,
The specific pattern is recorded in advance, and the value of the multi-valued level Pas is controlled based on the reproduction signal of the recording mark string.

Here, when the high frequency superimposition is not applied at the time of recording, the level Pas between the recording pulse and the next recording pulse, that is, the rest period of the recording pulse is a low power output state which is determined by the DC bias current and returns. Affected by light. For this reason, the optical output changes. As a result, as shown by the dotted line 201 in FIG.
The recording mark fluctuates, and the detected edge shift slightly increases. FIG. 1 (b) shows an apparatus configuration for the purpose of forming a more complete and stable mark. In this embodiment, the bias light level due to the bias current when the high frequency superposition is turned off during recording is monitored,
The Pr level is controlled to reach the target value. In FIG. 1B, in order to monitor the output of the laser, a front monitor that divides a part of the light applied to the optical disc to receive the light,
Alternatively, the rear monitor 11 for detecting the laser output on the rear end face side of the laser is used. The sample hold circuit 12 samples the output during the rest period of the recording pulse and holds it at other times. The control circuit 16 switches the sample timing.
To do. A differential output of the output sampled by the differential circuit 16 and a preset set bottom power is formed. After this, for example, the differential output is converted to A / D converter 14 and D / A converter
Through 5, set the Pr level of the laser drive circuit.

Further, the Pr level may be set in a specific area when the disc is inserted into the device, or the Pr level may be set in a specific area for each zone in the zone CAV method. In addition, the device temperature should be changed regularly.
You may set the level of Pr.

When reproducing information, the laser is normally driven with a reproducing power of DC level. Also in this case, the output from the monitor 11 is compared with the set reproduction power in the differential circuit 19, and the laser output is maintained at a predetermined value. The power control operation during recording and reproduction can be switched by controlling the switches 21 and 22 using a recording gate signal.

Further, since the optimum power at the time of recording changes with the reflectance of the disc, as shown in FIG. 1, the amount of light reflected from the disc is detected by the detector 15 and the difference from the standard amount of reflected light is also detected. By setting the bottom level 20 set to and and controlling the Pr level, more stable recording marks can be recorded.

FIG. 3 shows a second embodiment. When recording information,
By changing the setting of the amplitude and frequency of the high frequency superimposition at the time of erasing and reproducing the information by the setting circuit 301, the semiconductor laser can be driven by superimposing the optimum high frequency in each mode,
It is possible to further reduce the S / N ratio deterioration due to the influence of the return light.

[0016]

Since the output of the recording light pulse does not change due to the returning light, the temperature distribution on the disk does not change due to the recording irradiation. Therefore, it is possible to prevent a decrease in SN due to variations in recording marks.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a waveform diagram of a recording waveform and recording marks.

FIG. 3 is a principle diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1 ... Semiconductor laser, 20 ... Set bottom power.

Claims (8)

[Claims] 1. When recording modulated data on a disc,
A recording control method characterized in that, in an optical recording / reproducing apparatus that switches the recording irradiation power at multiple levels, the lowest power level is controlled to a certain target value. 2. The method according to claim 1, wherein the first level is
A recording waveform control method characterized in that the detection value of an optical output monitor of a recording light source is controlled to be a constant value. 3. The method according to claim 1, wherein the first level is
A recording waveform control method characterized by controlling proportionally to changes in the amount of light reflected from the disk surface. 4. The method according to claim 1, wherein a specific pattern is recorded in advance before the user data is recorded at the target recording position, and the multilevel level is controlled based on the reproduction signal of the recording mark row. Characterized recording control method. 5. A recording control method characterized by changing the amplitude and frequency settings of high frequency superposition during recording, erasing and reproducing. 6. An optical recording method for recording information on a recording medium using a comb-shaped laser waveform in which pulsed laser light is superimposed on DC laser light, the level of the DC laser light is detected, and the level is detected. An optical recording method characterized by controlling so as to maintain a predetermined value. 7. An optical recording method for recording information on a recording medium by using a comb-shaped laser waveform in which pulsed laser light is superimposed on bottom-level laser light, wherein the pulsed laser light is pulsed between predetermined pulses. An optical recording method characterized by controlling so that the bottom level is maintained at a predetermined value. 8. Information is recorded on a recording medium using a comb-shaped laser pulse waveform, the recording medium is irradiated with a laser beam of approximately DC level, and the information is reproduced by the reflected light from the medium. At the time of reproduction, a semiconductor is used. High frequency is superimposed on the laser drive current, and high frequency is not superimposed on the semiconductor laser drive current during recording.
An optical recording / reproducing control is performed so that the DC level is maintained at a predetermined value during reproduction, and a level between the comb teeth of the laser pulse waveform is maintained at a predetermined value during recording. Method.