JPH0668469A - Optical disk device - Google Patents

Abstract

PURPOSE:To obtain an accurate recording mark by performing the control of a semiconductor laser in the recording of light information based on a differential signal between a reference light output selected by a selection means and a detected light output. CONSTITUTION:An optical beam emitted from the semiconductor laser 101 to an objective lens 108 is divided by an optical divider 102, and the recording of information is performed on an optical disk 109 with the optical beam on one side. Also, the light output of the optical beam on the other side is detected 103, and difference between the output and a reference light output signal 105 is obtained by a subtractor 106, thereby, the output of the semiconductor 101 can be controlled. A desired reference light output signal 105 is selected corresponding to recorded information from a storage means 110 which stores plural reference light output signals 105 and the plural reference light output signals 105 in the means 110 by the selection means 107. The control of the semiconductor laser 101 when the light information is recorded is performed by the differential signal between the reference light output signal 105 selected by the selection means 107 and a detected light signal 104.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for recording and reproducing information.

[0002]

2. Description of the Related Art In an optical disk information recording / reproducing apparatus, when recording or reproducing information on an optical disk, an information recording / reproducing optical head is moved in a radial direction to a target track position and a light beam emitted from the optical head is aimed. Access to the track to record and play the mark. When recording and reproducing marks, the amount of light emitted to the rear side of the laser (hereinafter back laser light) is detected instead of the light emitted from the semiconductor laser toward the objective lens (hereinafter front laser light). The laser light output was controlled at a low speed. However, since the front laser light and the back laser light are not in a proportional relationship, it was impossible to accurately control the light beam output applied to the disc.
Further, since the laser power during recording is not feedback-controlled, the recording power fluctuates greatly with respect to the ambient temperature change. When the mark is recorded with a constant output, the record mark has a teardrop shape which is asymmetric with respect to the recording direction. A method of performing recording compensation with a pulse waveform is being studied, but in this case, it is difficult to shorten the rise time and fall time of the recording pulse, so it is possible to obtain accurate recording in a short time for a short recording pulse. It was difficult to compensate.

[0003]

The conventional optical disk device has a problem that the light output cannot be accurately controlled because the light directed to the objective lens is not detected and controlled. Further, if a constant optical output mark is recorded, there is a problem that the recording mark becomes a teardrop shape that is asymmetric with respect to the recording direction. SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical disc device capable of accurately controlling the light output and making the recording mark symmetrical in order to solve the above-mentioned problems.

[0004]

According to the present invention, a reference light output signal read from a semiconductor memory device and a detection signal of a front laser light output are compared with each other to feed back a semiconductor laser drive current to obtain a recording light output waveform. To get At this time,
The semiconductor memory device stores a plurality of reference light output waveforms in advance, and the recording light output is changed by selectively reading the reference light output signal (waveform) from the semiconductor memory device at the time of recording to change the optical power of the semiconductor laser. It changes the output.

[0005]

According to the present invention, by changing the optical output at the time of writing the mark according to the waveform recorded in the semiconductor memory device, the mark becomes symmetrical, so that the intersymbol interference of the reproduced signal is reduced and the reproduced signal is reduced. Error is reduced.

[0006]

FIG. 1 is a diagram showing an embodiment of the present invention. The collimator lens 117 is emitted from the semiconductor laser 101.
The light beam directed to the objective lens 108 via is split by the beam splitter 102, and the semiconductor laser light output is detected by the photodetector 103. As the semiconductor laser 101, for example, a red laser with a wavelength of 690 nm is used as the objective lens 1.
As 08, for example, a lens with NA = 0.6 can be used. The difference between the semiconductor laser light output detection signal 104 and the reference light output signal 105 is detected by the subtractor 106 and amplified by the compensation amplifier 107 to drive the current of the semiconductor laser 101. The optical output of the semiconductor laser is fast feedback controlled. On the other hand, the light beam passing through the beam splitter 102 and heading for the objective lens 108 reaches the optical disc 109 to record and reproduce marks. Since the front laser light emitted from the semiconductor laser and directed to the objective lens is split and detected to control the light output of the semiconductor laser, the laser light output can be accurately controlled. The waveform of the reference light output signal 105 is read from the semiconductor memory device 110 and converted into an analog signal by the D / A converter 111. A plurality of optical output waveforms are recorded in the semiconductor memory device 110 as digital data, and the recording optical output waveform is selected according to information such as the recording radius, the recording linear velocity, the recording signal pattern, and the sensitivity of the recording medium. The address generator 112 determines the recording light output waveform to be read based on information such as the recording radius data 113, the recording linear velocity data 114, the recording signal pattern data 115, and the sensitivity data 116 of the recording medium, and the recording light output waveform is recorded. Generated address. By changing the recording light output waveform, it is possible to perform recording compensation adapted to the recording data pattern. FIG. 2 is a diagram showing the recording light output waveform, the temperature of the recording medium, and the mark shape. When recording is performed with a constant recording power in a write-once medium such as Ag-TeC having a small heat conduction constant, the temperature gradient in the front part of the mark becomes the temperature gradient in the rear part of the mark as shown in FIG. On the other hand, it becomes smaller, and the jitter at the edge in front of the mark becomes larger. Therefore, the S / N of the reproduced signal is deteriorated. Further, the recording mark shape becomes a teardrop shape. As shown in FIG. 2B, when the recording timing is delayed and the recording light output is increased only for the initial time of recording, the temperature gradient in the front part of the recording mark becomes large and the jitter in the front part of the mark becomes small. The signal S / N can be improved. The temperature gradient at the front of the mark can be increased without changing the mark position. The reference light output waveform that gives the target recording light output waveform is recorded in the semiconductor memory device as digital data. If it takes a long time to read this digital data,
It may be read in a high-speed semiconductor memory device such as an ECL memory.

FIG. 3 shows an example of the recording data pattern and the recording mark shape. When the heat conduction constant is large, for example, in the case of the phase change medium InSbTe, the mark has a teardrop shape as shown in FIG. As shown in FIG. 3 (b),
A reference light output waveform pattern that increases the recording light output at the beginning of recording and then obtains a recording light output waveform that gradually decreases is stored in the semiconductor memory device.
When the recording light output is changed as shown in FIG. 3B by reading the reference light output waveform from the semiconductor memory device,
The shape of the recording mark front part and the recording mark rear part are the same,
The recording mark shape is symmetrical with respect to the recording direction.

In the present invention, since the recording light output is changed in an analog manner to perform the recording compensation, the recording compensation can be performed even for a short time recording such as when recording the inner circumference of the optical disk. Further, since the laser light output is controlled at high speed up to the recording signal band, laser noise in the recording signal band can be reduced. In addition, since the recording laser output waveform is controlled by the reference light output signal, the recording power can be stabilized against changes in the ambient temperature and stable recording can be performed even on a medium having a small power margin such as an overwrite recording medium.

FIG. 4 shows another embodiment of the present invention. The light output of the front beam light emitted from the semiconductor laser 401 is detected by the photodetector 402 and converted into digital data by the A / D converter 403. The digital data and the reference light output waveform read from the semiconductor memory device 404 are subtracted by the digital subtractor 405. Digital subtractor 40
The output of 5 drives a semiconductor laser through a digital compensation calculator 406 and a D / A converter 407. The address generator 408 stores the recording radius data 409 and the recording linear velocity data 41.
0, the recording signal pattern data 411, the sensitivity data 412 of the recording medium, and the like determine the recording light output waveform to be read, and the address at which the recording light output waveform is recorded is generated. Then, the recording light output waveform corresponding to this address is input to the digital subtractor 405 as the reference light output waveform. In this way, by changing the recording light output waveform, it is possible to perform recording compensation adapted to the recording data pattern.

FIG. 5 shows another embodiment of the present invention. The light output of the front beam light emitted from the semiconductor laser 501 is detected by the photodetector 502 and converted into digital data by the A / D converter 503. This digital data is taken into the microcomputer 504, and the semiconductor memory device 5
It is compared with the reference light output waveform read from 05. The comparison result is calculated according to the software-implemented semiconductor laser light output control routine, and is output to the D / A converter 506 to drive the semiconductor laser. Microcomputer 504
Is the recording radius data 507, the recording linear velocity data 508, the recording signal pattern data 509, and the sensitivity data 5 of the recording medium.
The recording light output waveform to be read is determined based on the information such as 10, an address at which the recording light output waveform is recorded is generated, and the reference light output data is read from the semiconductor memory device 505.

[0011]

According to the present invention, since the recording light output can be changed in an accurate and analog manner, the recording light output waveform can be precisely controlled, and a desired accurate recording mark can be obtained. . By changing the recording light output waveform during recording, the recording mark becomes symmetrical, and it is possible to reduce intersymbol interference of the reproduced signal. For this reason,
Since the intersymbol interference is reduced, the eye of the reproduction signal eye pattern is opened, the wind margin is increased, and the error is reduced. Since light output is controlled at high speed, light output noise is reduced. The signal-to-noise ratio of the reproduced signal is improved and the error is reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical head of the present invention.

FIG. 2 is a control block diagram of the present invention.

FIG. 3 Noise spectrum of laser light

FIG. 4 Recording waveform and recording mark shape

FIG. 5: Recording waveform and recording mark shape

[Explanation of symbols]

 101 semiconductor laser 102 optical beam splitter 103 photodetector 104 semiconductor laser light output detection signal 105 reference light output signal 106 subtractor 107 compensation amplifier 108 objective lens 109 optical disk 110 semiconductor memory device 111 D / A converter 112 address generator 113 recording Radius data 114 Recording linear velocity data 115 Recording signal pattern data 116 Recording medium sensitivity data 117 Collimator lens 118 Convex lens 119 Convex lens 120 Reproduction signal photodetector 401 Semiconductor laser 402 Photodetector 403 A / D converter 404 Semiconductor storage device 405 Digital subtractor 406 Digital compensation calculator 407 D / A converter 408 Address generator 409 Recording radius data 410 Recording linear velocity data 411 Recording signal pattern data 12 Sensitivity data of recording medium 501 Semiconductor laser 502 Photodetector 503 A / D converter 504 Microcomputer 505 Semiconductor memory device 506 D / A converter 507 Recording radius data 508 Recording linear velocity data 509 Recording signal pattern data 510 Recording medium Sensitivity data

Claims (1)

[Claims] 1. A light beam emitted from a semiconductor laser toward an objective lens is split by a light splitter, and one light beam split by this light splitter records information on an optical disc while the other light beam is split. In the optical disc device for detecting the light output of the light beam and controlling the current of the semiconductor laser by the difference signal between the detected light output and the reference light output signal, a storage unit for storing a plurality of the reference light output signals, Selecting means for selecting a desired reference light output signal according to the information to be recorded from the plurality of reference light output signals of the storage means, and controlling the semiconductor laser at the time of recording the optical information, An optical disk device, characterized in that it is performed based on a difference signal between the reference light output signal selected by the means and the detected light output.