JP2669408B2 - Driving method of semiconductor laser - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a semiconductor laser, and more particularly to a method of recording a semiconductor laser used as a light source of a digital optical disk at the time of recording. 2. Description of the Related Art In a conventional optical recording / reproducing apparatus which performs recording / reproducing using a laser beam, a rectangular wave as shown in FIG. 1 is used as a laser output waveform at the time of recording. However, in the recording method of an optical disc in which a recording hole (pit) is generated by melting a metal film with such a rectangular wave laser beam, preheating is required when the recording hole is generated. A part of the recording hole is used as preheating energy, and there is a problem that the diameter at the beginning of the recording hole is small and the diameter is large in the latter half (see FIG. 1). The recording hole with the above-mentioned shape may not be played back correctly during playback, so data recording and
This will reduce the reliability of reproduction. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of driving a semiconductor laser used as a light source of a conventional digital optical disk at the time of recording. To solve the above problems in
An object of the present invention is to provide a method of driving a semiconductor laser capable of adjusting the shape of a recording hole generated by a laser beam, stabilizing a reproduction waveform of the recording hole, and improving the reliability of data recording / reproduction. An object of the present invention is to provide a semiconductor laser driving method for driving a semiconductor laser by superimposing a pulse on a DC bias in an optically recordable / reproducible optical disk device. This is achieved by a method of driving a semiconductor laser, characterized in that the amplitude of the waveform of the superposed pulse is changed between the first half and the second half of the pulse. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a diagram showing a drive circuit for a semiconductor laser which is an embodiment of the present invention. The laser drive circuit 3 is composed of a transistor 4 for supplying a laser current during reproduction and transistors 5 and 6 for supplying a pulse current during recording. Pulse generation circuits 1 and 2 for generating a pulse at the rising edge of the recording data signal 9 are connected to the preceding stages of the recording pulse supply transistors 5 and 6, respectively. The pulse widths of the pulses 10 and 11 generated from the pulse generation circuits 1 and 2 are different as shown in the figure. In the circuit of this embodiment constructed as described above, the laser is driven during data recording as follows. A DC input is applied to the reproduction signal input 8, and the reproduction laser current value IR is controlled by this DC level. On the other hand, the recording data is input to 9 and two pulses 10 and 11 having different output pulse widths are generated from the pulse generation circuits 1 and 2 by the rise of this signal.
These pulses cause recording currents Iw1 and Iw2 to flow through the collectors of the recording pulse supplying transistors 5 and 6, respectively. A current, IR + Iw1 + Iw2, obtained by adding the collector currents of the respective transistors described above flows through the laser diode 7. FIGS. 3A and 3B show signal waveforms at respective points in FIG. 2, wherein FIG. 3A shows a reproduction signal input 8 and FIG.
Is shown. (C) shows the collector current of the reproduction power supply transistor 4, and (d) and (e) show the collector currents of the recording pulse supply transistors 5 and 6, respectively.
(f) shows the current flowing through the laser diode 7 obtained by adding these. As shown in FIG. 3 (f), the current flowing through the laser diode 7 has a large amplitude at the rising edge of the pulse and a small amplitude in the latter half. Accordingly, as shown in FIG. 4, the power of the laser diode 7 corresponding to this current waveform is such that the recording power corresponding to the beginning of the recording hole is increased. As a result, it becomes possible to sufficiently provide the preheating energy and secure the energy for drilling at the beginning of the drilling of the recording hole, and to make the shape of the recording hole close to a perfect circle (FIG. 5). it can. As described above, according to the present invention, there is provided a semiconductor laser driving method for driving a semiconductor laser by superimposing a pulse on a DC bias in an optically recordable / reproducible optical disk device. By changing the amplitude of the waveform of the superimposed pulse between the first half and the second half of the pulse, the shape of the recording hole written on the optical disk was adjusted.
This has a remarkable effect of stabilizing the reproduction waveform of the recording hole and improving the reliability of data recording / reproduction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a laser power and a shape of a recording hole generated in a conventional laser driving method. FIG. 2 is a circuit diagram showing an embodiment of the present invention. FIG. 3 is a diagram showing a signal waveform at each point in FIG. FIG. 4 is a diagram showing a relationship between a laser drive circuit and laser power. FIG. 5 is a diagram showing a laser power and a shape of a recording hole to be generated. [Description of Signs] 1, 2: pulse generating circuit, 3: laser driving circuit, 4: transistor for supplying reproduction power, 5, 6: transistor for supplying recording pulse, 7: laser diode.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Masahiro Takasago               2880 Kozu, Odawara-shi, Kanagawa Stock Association               Inside Odawara Plant of Hitachi, Ltd.                (56) References JP-A-55-139693 (JP, A)                 JP-A-56-158319 (JP, A)                 JP 55-143092 (JP, A)                 JP-A-56-17586 (JP, A)

Claims (1)

(57) [Claims] A method of driving a semiconductor laser that records information on an optical recording medium by driving a semiconductor laser serving as a light source and emitting laser light, wherein when recording information on the recording medium, a constant A first pulse current which flows a current and rises in synchronization with a signal input of the recording data, and has a pulse width narrower than the signal of the recording data; a pulse having an amplitude smaller than the amplitude of the first pulse current; A method for driving a semiconductor laser, comprising: driving a semiconductor laser by superimposing a second pulse current having a width smaller than a signal of the recording data on the constant current.