JPH0438624A - Optical disk device - Google Patents

Abstract

PURPOSE:To accurately record on an optical disk without being affected by a flaw of the disk or a vibration due to a disturbance by supplying a semiconductor laser with a comparatively high driving current to obtain a focus error signal more than a prescribed value. CONSTITUTION:When the focus error signal is inputted to a window comparator 9 at the time of recording, a high level power-up signal is outputted by the window comparator 9 at the time when the focus error signal exceeds a threshold as shown in the Figure with a broken line. A recording data is formed on the optical disk 2 with the semiconductor laser 4 which is turned on and off by a laser driver with the driving current for recording in response to a recording data signal from a modulator 10. Then, when the high level power-up signal is inputted from the window comparator 9, the semiconductor laser 4 is turned on and off by a still higher level driving current. By this method, even when the laser spot becomes largely out of focus by a flaw of the optical disk or the vibration due to disturbance, the accurate recording can be performed because the light quantity of the semiconductor laser is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc device for recording and reproducing images, audio, data, and the like.

Conventional technology In general, this type of optical disk device includes a semiconductor laser that emits a beam, an objective lens that shapes the beam into a spot light and irradiates it onto an optical disk, and a lens that focuses the reflected light. In addition to the reproduction data signal, a light-receiving element etc. is used to obtain a focus error signal indicating whether the focal position of the beam is near or far with respect to the optical disk surface, and a tracking error signal indicating the positional deviation of the beam with respect to the track of the optical disk. The optical pickup is configured such that a beam is focused on the optical disk surface by a focus error signal during recording and reproduction (focus servo).

However, due to the limitations of the focus servo's ability, the defocus becomes large due to vibrations caused by scratches and disturbances on the optical disk, and also because the light intensity (power) of the semiconductor laser decreases over time, vibrations caused by scratches and disturbances on the optical disk. The impact will be even greater.

Conventionally, this type of optical disk device maintains the output power of a semiconductor laser at a relatively high level and controls it to have a large tolerance for defocus, thereby achieving accurate performance without being affected by scratches on the optical disk or vibrations caused by external disturbances. It is configured so that it can be recorded.

Problems to be Solved by the Invention However, in the conventional optical disk device described above, the output power of the semiconductor laser is set to such a high level in order to prevent the output power of the semiconductor laser from becoming excessive when the beam is less defocused. The problem is that it cannot be done.

Further, in the conventional optical disk device described above, since the output power of the semiconductor laser is kept constant at a relatively high level, there is a problem that the life of the semiconductor laser is shortened.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, an object of the present invention is to provide an optical disc device that can accurately record data without being affected by scratches on the optical disc or vibrations caused by external disturbances, and can extend the life of a semiconductor laser. With the goal.

Means for Solving the Problems In order to achieve the above object, the present invention supplies a relatively high drive current to a semiconductor laser when the focus error signal exceeds a predetermined value. The configuration supplies a relatively high drive current to the semiconductor laser only when the beam is sharply defocused, making it possible to record accurately without being affected by scratches on the optical disk or vibrations caused by external disturbances. Since a relatively high drive current is not constantly supplied to the semiconductor laser, the life of the semiconductor laser can be extended.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of an optical disc device according to the present invention, and FIG. 2 is a timing chart showing main signals of the optical disc device of FIG.

In FIG. 1, numeral 1 is a motor for rotating an optical disc 2, which is a recording medium, and numeral 3 is an optical pickup movable in the radial direction of the optical disc 2 in order to roughly seek a track on the optical disc 2.

The optical pickup 3 includes a semiconductor laser 4 that emits a beam.
Then, the beam is shaped into a spot light and irradiated onto the optical disc 2, and an objective lens 6 is used to collect the reflected light, and the objective lens 6 is slightly moved in the axial direction of the optical disc 2 to direct the beam onto the optical disc 2. A focus actuator 6a for focusing; a tracking actuator 6b for moving the objective lens 5 minutely in the radial direction of the optical disc 20 to make the beam follow the tracks of the optical disc 2 or move between tracks; A detector 6 uses reflected light to detect a focus error signal indicating whether the focal position of the beam is far or near with respect to the optical disk surface, and the reflected light detects a reproduced data signal and a position shift of the beam with respect to the track of the optical disk 2. A detector 7 and the like are provided for detecting a tracking error signal indicating a tracking error signal.

Note that when the beam is focused on the optical disc 2, the beam shape is a perfect circle, and when the focal position of the beam is in either a far or near direction with respect to the optical disc 2, the shape is determined depending on the direction and the amount of deviation. It is an ellipse.

Therefore, by configuring the detector 6 with a plurality of photodiodes, etc., as shown in FIG. 2(a), when the beam is focused on the optical disk 2,
Furthermore, when the focal position of the beam is in either a far or near direction with respect to the optical disc 2, it is possible to obtain a focus error signal with a polarity corresponding to the direction and a level corresponding to the amount of deviation thereof.

8 is a focus servo circuit that controls the focus actuator 6a so that the beam is focused on the optical disk 2 according to the focus error signal from the detector 6;
Reference numeral 9 includes a differential amplifier and the like, and as will be described later, a window comparator for controlling the light amount of the semiconductor laser 4 according to the level of the focus error signal from the detector 6; 1o a modulator for modulating recording data; 11; teeth,
A laser driver that supplies a relatively high drive current to the semiconductor laser 4 during recording according to the modulated recording data from the modulator 1o and the control of the window comparator 9, and supplies a relatively low drive current to the semiconductor laser 4 during reproduction. be.

12, the beam follows the track of the optical disk 2 due to the tracking error signal from the detector 7;
A tracking servo circuit 13 that controls the tracking actuator 6b to move between tracks is a demodulator that demodulates modulated reproduction data from the detector 7.

Next, the operation of the above embodiment will be explained with reference to FIG.

During recording, when a focus error signal as shown in FIG. 2(a) is input to the window comparator 9, the window comparator 9 outputs a signal as shown in FIG. Outputs a high-level power-up signal like this.

The laser driver turns on and off the semiconductor laser 4 with a recording drive current according to the recording data signal from the modulator 1o to form recording data on the optical disk 2, and receives a high-level power-up signal from the window comparator 9. When inputted, the semiconductor laser 4 is turned on and off with an even higher level drive current.

Therefore, even if defocus increases due to scratches on the optical disk or vibrations caused by disturbances, the amount of light from the semiconductor laser increases, so the amount of tolerable defocus increases, and the amount of light necessary for recording can be obtained.

Furthermore, since a high amount of light is obtained only when the defocus is large, the life of the semiconductor laser can be extended.

As described in detail, the present invention supplies a relatively high driving current to the semiconductor laser when the focus error signal exceeds a predetermined value, so that the semiconductor laser is driven only when the beam defocus is large. In order to supply a relatively high drive current, it is possible to record accurately without being affected by scratches on the optical disk or vibrations caused by external disturbances, and in order not to constantly supply a relatively high drive current to the semiconductor laser,
The life of the semiconductor laser can be extended.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an optical disc device according to the present invention, and FIG. 2 is a timing chart showing main signals of the optical disc device of FIG. 2... Optical disk, 4... Semiconductor laser, 6...
Focus error signal detector, 9... window comparator, 11... laser driver.

Claims (1)

[Claims] Using a semiconductor laser that emits a beam to irradiate the optical disc and the reflected light of the beam irradiated onto the optical disc, a focus error signal is detected that indicates whether the focal position of the beam is near or far from the optical disc surface. and means for supplying a relatively high drive current to the semiconductor laser when the focus error signal exceeds a predetermined value when recording data on the optical disc.