JP2523464B2 - Driving method for semiconductor laser - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing method, and more particularly to driving of a semiconductor laser at the time of recording / reproducing information in an optical disc device using a semiconductor laser as a light source.

2. Description of the Related Art In a conventional optical recording / reproducing apparatus for recording / reproducing using a laser beam, a rectangular wave as shown in FIG. 1 is used as a laser output waveform during recording. However, in the recording method of the optical disc in which the recording holes (pits) are generated by melting the metal film by the rectangular-wave laser light, preheating is required when the recording holes are generated, and therefore the recording laser beam is used. There is a problem that a part of the above is used as preheating energy, the diameter of the opening of the recording hole is small, and the diameter is large in the latter half (see FIG. 1). The recording hole having the above-described shape may not be reproduced properly during reproduction, which reduces the reliability of data recording / reproduction.

In order to solve the above problems, for example, JP-A-55-13
Japanese Patent No. 9693 discloses the idea that, when information is written by irradiating an optical disk with laser light whose on / off control is performed, the irradiation intensity of the laser light at the rising time is higher than that of other portions.

However, in this technique, the light emitted from the laser light source is intensity-modulated by a specially provided optical modulator to form a shaped pit on the optical disc, and moreover, it was written on the optical disc. When playing the information,
How to drive the laser light source or the optical modulator is not particularly mentioned in the above-mentioned known example.

Object of the invention The first object of the present invention is to record and reproduce information on an optical recording medium by using the same semiconductor laser as a light source, and to further intensify the light emitted from the light source by using a special modulator. To provide an optical recording / reproducing method in which the reliability of recording / reproducing of information is improved by shaping the pit shape at the time of recording information by controlling the driving current of the semiconductor laser itself instead of modulating. It is in.

A second object of the present invention is to improve the reliability of recording and reproduction by directly driving the semiconductor laser with current when recording and reproducing information on an optical recording medium using the same semiconductor laser as a light source. An object of the present invention is to provide an improved semiconductor laser drive circuit.

General Description of the Invention In order to achieve the above object, a first invention is to record information on an optical recording medium by driving a semiconductor laser as a light source to emit a laser beam, and the recording medium has already been recorded. In the optical recording / reproducing method for reproducing the information recorded on the recording medium, when reproducing information from the recording medium, a constant current is passed to drive the semiconductor laser, and when recording information on the recording medium, a recording pulse is used. In synchronism with the rise of the pulse current, a recording current composed of a pulse current having a short pulse width and a large current value and a pulse current having a wide pulse width and a small current value is added to the constant current to drive the semiconductor laser. It was done.

A second invention is an optical recording / reproducing for recording information on an optical recording medium by driving the same semiconductor laser as a light source and emitting a laser beam, and reproducing the information already recorded on the recording medium. A driving circuit for a semiconductor laser in an apparatus, one end of which is connected to the semiconductor laser, a first transistor which allows a constant current to flow when reproducing information from the recording medium, and one end of which is connected to the semiconductor laser. It has a second transistor for supplying a current corresponding to a recording pulse when recording information on the recording medium, and turns on the first transistor and the second transistor when recording information.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment of the Invention FIG. 2 is a diagram showing a semiconductor laser drive circuit according to 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.
In front of the recording pulse supplying transistors 5 and 6, pulse generating circuits 1 and 2 for generating a pulse at the rising edge of the recording data signal 9 are connected, respectively. The pulse generation circuit
The pulse widths of the pulses 10 and 11 generated from 1 and 2 are different as shown in the figure.

In the circuit of this embodiment configured 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 I _R is controlled by this DC level. On the other hand, the recording data is input to 9, and the rise of this signal causes the pulse generating circuits 1 and 2 to generate two pulses 10 and 11 having different output pulse widths. These pulses cause recording currents I _W1 and I _W2 to flow through the collectors of the recording pulse supplying transistors 5 and 6. A current obtained by adding the collector currents of the respective transistors described above, I _R + I _W1 + I _W2 , flows through the laser diode 7.

FIG. 3 shows the signal waveform at each point in FIG.
(A) is a reproduction signal input 8 and (b) is a recorded data input 9
Is shown. Further, (c) shows the collector current of the reproducing power supply transistor 4, (d) and (e) show the collector currents of the recording pulse supply transistors 5 and 6, respectively, and (f) is the sum of these. Laser diode 7
It shows the current flowing through the.

As shown in FIG. 3 (f), the current flowing through the laser diode 7 has a large amplitude when the pulse rises and a small amplitude in the latter half. Therefore, as shown in FIG. 4, the power of the laser diode 7 corresponding to this current waveform becomes larger than that at the beginning of the opening of the recording hole. As a result, it is possible to sufficiently give preheating energy and secure the energy for drilling at the beginning of drilling of the recording hole, and it is possible to make the shape of the recording hole close to a perfect circle.

According to the first aspect of the present invention, information can be recorded and reproduced by using the same semiconductor laser, and by controlling the drive current of the semiconductor laser itself without using a special modulator. Since the pit shape at the time of information recording can be shaped, the reliability of information recording and reproduction is improved.

According to the second aspect of the invention, the same semiconductor laser can be directly current-driven at the time of recording and reproducing information by a relatively simple transistor circuit, and the reliability of recording and reproducing information is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a laser power and a shape of a recording hole to be generated in a conventional laser driving method, FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is at each point of FIG. FIG. 4 is a diagram showing the signal waveform, FIG. 4 is a diagram showing the relationship between the laser drive circuit and laser power, and FIG. 5 is a diagram showing the laser power and the shape of the generated recording holes. 1,2: pulse generation circuit, 3: laser drive circuit, 4: reproduction power supply transistor, 5, 6: recording pulse supply transistor, 7: laser diode.

Front page continued (72) Inventor Hiromi Senoo 2880, Kozu, Odawara City, Odawara Plant, Hitachi, Ltd. (72) Inventor Masahiro Takasago 2880, Kozu, Hitachi, Ltd. (56) Reference, Odawara, Hitachi Ltd. 55-139693 (JP, A) JP-A-57-33441 (JP, A)

Claims (2)

(57) [Claims] 1. An optical recording / reproducing method for recording information on an optical recording medium by driving a semiconductor laser serving as a light source to emit a laser beam, and reproducing the information already recorded on the recording medium. When reproducing information from the recording medium, a constant reproducing current is passed through the semiconductor laser to drive the semiconductor laser, and when information is recorded on the recording medium, in synchronization with signal input of recording data. A rising first pulse current having a different pulse width and a narrower pulse width than the recording data signal, and a second pulse current having a pulse width substantially equal to the recording data signal. To
An optical recording / reproducing method characterized by driving the semiconductor laser in addition to the constant reproducing current. 2. An optical recording / reproducing method of recording information on an optical recording medium by driving the same semiconductor laser as a light source to emit laser light and reproducing the information already recorded on the recording medium. In the semiconductor laser, one end is connected to the semiconductor laser, and a first transistor for flowing a constant current when reproducing information from the recording medium; and the one end is connected to record information on the recording medium. A second transistor which rises in synchronism with a signal of the recording data and has a pulse width narrower than that of the signal of the recording data, and which supplies a second current, and is connected to the one end when recording information on the recording medium. A third current that rises in synchronization with the recording data signal and has a pulse width that is substantially equal to the recording data signal
Optical recording, characterized in that the first transistor is turned on when reproducing information, and the first, second and third transistors are turned on when recording information. How to play.