JPH04252437A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent significant information from being dissipated by providing a laser output control means which controls the output of a laser based on the output of a first light detecting means, a second light detecting means which monitors the strength of a laser beam, and a stopping means for the laser output control means based on the output of the detecting means. CONSTITUTION:Recording/reproduction is performed by irradiating an information carrier 5 with the laser beam emitted from the laser 1 by an optical head. Also, the strength of the laser beam is monitored by the first light detecting means 8, and the output of the laser 1 is controlled based on the output of the first light detecting means 8. Furthermore, the strength of the laser beam is monitored by the second light detecting means 10, and it is compared with a reference power source 11 by a comparator 12, and the output of the laser output control means 9 is stopped by a switch 13 based on the output of the second light detecting means 10. Thereby, it is possible to stop the radiation of the laser beam before information on the disk 5 is impaired due to the occurrence of abnormality in reproduction and the increment of the output of the laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical recording/reproducing apparatus using a write-once optical disc or the like.

[Conventional technology] The configuration of a conventional example will be explained with reference to FIG.

FIG. 3 is a configuration diagram showing a conventional optical recording/reproducing apparatus disclosed in, for example, Japanese Utility Model Application Publication No. 113419/1983.

In Figure 3, (1) is a semiconductor laser that emits a laser beam, (2) is a collimating lens that converts the laser beam emitted from the semiconductor laser (1) into a parallel beam, and (3) is a beam that separates the beam. Splitter, (4) is an objective lens that condenses a parallel light beam, (5) is a disk that is an information carrier, and (6) is a photodetector that detects the light beam reflected by the disk (5) and reproduces information. (7) is a condenser lens (8) that condenses the light beam reflected by the beam splitter (3) among the laser light emitted from the semiconductor laser (1) and converted into a parallel light beam by the collimating lens (2); is a photodetector that receives the light beam focused by the condenser lens (7), and (9) is a photodetector that feeds back the signal detected by the photodetector (8) to adjust the output of the semiconductor laser (1) to a specified output. This is a laser drive output control circuit that controls the

Next, the operation of the conventional example described above will be explained.

A light beam emitted from a semiconductor laser (1) is converted into a parallel light beam by a collimating lens (2) and enters a beam splitter (3). A part of the light beam incident on the beam splitter (3) is reflected, and the rest is transmitted. The transmitted light beam is focused by an objective lens (4) and then directed to a disk (5).
is irradiated to.

The reflected light from the disk (5) passes through the objective lens (4) and enters the beam splitter (3), and the reflected light flux reaches the photodetector (6).

For example, if the disk (5) is a WORM disk with holes, when there are holes, the amount of light received by the photodetector (6) is small, and when there are no holes, the amount of light received by the photodetector (6) is small. ), the amount of light received by the photodetector (6) increases.
) The information recorded on the disc (5) can be reproduced based on the strength of the signal detected by the disc (5).

Furthermore, when recording, information is recorded by making a hole in the disk (5) by increasing the output of the semiconductor laser (1).

On the other hand, the light beam emitted from the semiconductor laser (1) and reflected by the beam splitter (3) is condensed by a condenser lens (7) and received by a photodetector (8). Since the output of the photodetector (8) is proportional to the output of the laser light actually emitted from the semiconductor laser (1), the laser is driven so that the output of the photodetector (8) becomes a predetermined value. Output control circuit (
9) makes it possible to control the laser light output to the level required for recording during recording and to the level required for reproduction during playback.

[Problems to be Solved by the Invention] In the conventional optical recording/reproducing device as described above, if a foreign object such as dust gets between the beam splitter (3) and the photodetector (8), the semiconductor laser (1) ), the output of the photodetector (8) does not reach the predetermined value even though the output necessary for reproduction is output from the laser drive output control circuit (9).
) outputs more power than is necessary for playback, and important information recorded on the disc (5) is recorded over it even during playback, resulting in important information being lost. A similar problem occurs when a malfunction occurs in the circuit system connecting the photodetector (8) and the laser drive output control circuit (9).

This invention was made to solve the above-mentioned problems, and aims to provide an optical recording/reproducing device that can prevent loss of important information.

[Means for Solving the Problems] An optical recording/reproducing apparatus according to the present invention includes the following means.

[1] An optical head that performs recording and reproduction by irradiating an information carrier with laser light emitted from a laser.

[2] First light detection means for monitoring the intensity of the laser beam.

[3] Laser output control means for controlling the output of the laser based on the output of the first light detection means.

[4] Second light detection means for monitoring the intensity of the laser beam.

[5] Output stopping means for stopping the output of the laser output control means based on the output of the second light detection means.

[Operation] In the present invention, the optical head irradiates the information carrier with laser light emitted from a laser to perform recording and reproduction.

Further, the intensity of the laser beam is monitored by the first light detection means, and the intensity of the laser beam is monitored by the first light detection means, and the intensity of the laser light is monitored by the first light detection means.
The output of the laser is controlled based on the output of the light detection means.

Furthermore, the intensity of the laser beam is monitored by the second light detection means, and the output of the laser output control means is stopped by the output stop means based on the output of the second light detection means.

[Embodiment] The configuration of an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram showing one embodiment of the present invention, and the semiconductor laser (1) to the laser drive output control circuit (9) are completely the same as those of the conventional device.

In Figure 1, (10) is a photodetector that detects the light emitted backward from the semiconductor laser (1), and (11) is a standard for setting the voltage for comparison with the output of the photodetector (10). The power source (12) is the output of the photodetector (10) and the reference power source (
11), and when the output of the reference power supply (11) is greater than the output of the photodetector (10), the output is O.
N, and the output of the reference power supply (11) is the photodetector (10).
When the output is smaller than the output, it is turned off. (13) is a switch circuit that stops the output of the laser drive output control circuit (9) according to the output of the comparator (12), and when the output of the comparator (12) is ON, the switch circuit (
13) is turned ON, and when the output of the comparator (12) is OFF, the switch circuit (13) is turned OFF.

FIG. 2 shows a semiconductor laser (1
) and a photodetector (10
) is a perspective view showing the.

By the way, the optical head of the present invention includes a semiconductor laser (1) to an objective lens (4) in the above-described embodiment of the present invention.
and a photodetector (6), and the first photodetection means of the present invention is composed of a condenser lens (7) and a photodetector (8) in one embodiment, and the laser output control means of the present invention. In one embodiment, the second light detection means of the present invention is composed of a photodetector (10), and the output stop means of the present invention is composed of a laser drive output control circuit (9). , in one embodiment, a reference power supply (11), a comparator (12)
and a switch circuit (13).

Next, the operation of the embodiment described above will be explained.

The recording/reproducing operation is the same as the conventional one. Semiconductor laser (
The light beam emitted from the beam splitter (3) is focused by the condenser lens (7) and sent to the photodetector (8).
), and the output of this photodetector (8) is proportional to the output of the laser beam actually emitted from the semiconductor laser (1), so the output of this photodetector (8) reaches a predetermined value. The laser light output can be controlled to a predetermined output by the laser drive output control circuit (9) so that.

On the other hand, the light emitted from the rear of the semiconductor laser (1) is
It is detected by a photodetector (10), the output of which is led to one of the input terminals of a comparator (12), and the output of the reference power supply (11) to the other input terminal.

The output Va of the reference power supply (11) is larger than the output Vb of the photodetector (10) when the predetermined laser light is output during reproduction, and the laser light starts to damage the information on the disc (5) due to the laser light. When the output is smaller than the output of the photodetector (10
) is set to be smaller than the output Vc.

Therefore, normally, when the laser light output is the output at the time of predetermined reproduction, the output of the photodetector (10) is the same as that of the reference power supply (11).
Since it is smaller than , the output of comparator (12) turns ON,
The switch circuit (13) is also in the ON state. In other words, the light emitted from the semiconductor laser (1) is controlled by the laser drive output control circuit (
A loop controlled by 9) is formed.

However, if foreign matter such as dust gets between the beam splitter (3) and the photodetector (8), or if the photodetector (8)
If a malfunction occurs in the circuit system connecting the laser drive output control circuit (9) and the laser drive output control circuit (9), the photodetector (8) may
) does not reach a predetermined value, the laser drive output control circuit (9) operates to increase the laser light output. At this time, the output of the photodetector (10) becomes larger than the output Va of the reference power source (11), and the output of the photodetector (10) becomes larger than the output Va of the reference power source (11).
The output of 2) is OFF, and the switch circuit (13) is also OFF.
Since it becomes an FF, the output from the laser drive output control circuit (9) to the semiconductor laser (1) is stopped, and the emission of laser light is stopped.

That is, the reference power source (11) is set so that Vb<Va<Vc, and even if an abnormality occurs during playback, the output of the laser beam increases and the information on the disk (5) is Since the laser beam emission is stopped, it is possible to prevent important information from being accidentally lost during reproduction.

Although not shown, it goes without saying that this function is disabled when recording.

Furthermore, if a photodiode, which is originally included in the package of the semiconductor laser (1) as shown in FIG. 2, is used as the photodetector (10), a device for providing this function There is no need to worry about it becoming too large.

Also, as is clear, the functions of the photodetector (8) and the photodetector (10) described above are reverse combinations (photodetector (10)).
8) detects an abnormal increase in the output of the semiconductor laser (1). ).Furthermore, if the reliability of the device is high, the photodetectors (8) and (10) may be integrated instead of being separated into the photodetectors (8) and (10).

[Effects of the Invention] As explained above, the present invention includes an optical head that performs recording and reproduction by irradiating an information carrier with laser light emitted from a laser, and a first light detection means that monitors the intensity of the laser light. a laser output control means for controlling the output of the laser based on the output of the first light detection means; a second light detection means for monitoring the intensity of the laser beam; and a second light detection means for monitoring the intensity of the laser beam. and an output stop means for stopping the output of the laser output control means based on the output of the laser output control means, it is possible to prevent loss of important information.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is a perspective view showing a part of an embodiment of the invention, and Fig. 3 is a conventional optical recording/reproducing device. FIG. In the figure, (1)...semiconductor laser, (2)...collimating lens, (3)...beam splitter, (4)...objective lens, (5)...disk, (6)...photodetector, (7)...collector. Optical lens, (8)...Photodetector, (9)...Laser drive output control circuit, (10)...Photodetector, (11)...Reference power supply, (12)...Comparator, (13)...Switch circuit. be. In each figure, the same reference numerals indicate the same or equivalent parts. Agent Michishiro Soga

Claims (1)

[Claims] an optical head that performs recording and reproduction by irradiating a laser beam emitted from a laser onto an information carrier; a first photodetector that monitors the intensity of the laser beam; a laser output control means for controlling the output of the laser beam; a second light detection means for monitoring the intensity of the laser beam;
An optical recording/reproducing apparatus comprising: an output stop means for stopping the output of the laser output control means based on the output of the second light detection means.