JPS62298939A - Optical disk device - Google Patents

Abstract

PURPOSE:To prevent the laser power from exceeding an allowable value by detecting that the monitor signal of a laser back beam is not returned and turning off the laser before the laser outputs an abnormal power. CONSTITUTION:The dark current of a solar battery 2 used for monitor of the back beam of the laser is detected to discriminate the connection state between an operational amplifier 4 and the solar battery 2 and the operating state of the solar battery 2. When the solar battery is used, the dark current exists, and the dark current is conducted from the solar battery 2 to the operational amplifier 4 even if the laser is turned off. As the result, a voltage V3 corresponding to the dark current is generated as an offset in the output of the operational amplifier 4. However, the voltage V3 is minute, and an abnormality detection signal 16 goes to the high level when this voltage is amplified by an amplifying circuit 15 and is compared by a comparator 14. If the solar battery 2 is broken, the dark current is not conducted and the abnormality detection signal 16 goes to the low level. Consequently, the abnormal state is detected with the laser turned off, and a laser turning-on command 12 is turned off after this detection.

Description

DETAILED DESCRIPTION OF THE INVENTION 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to an optical disc device, and more particularly to laser protection and recording protection in an optical disc device for recording and reproducing information.

Conventional technology In optical disk devices that perform recording and playback, the optical properties of the recording film are changed by increasing or decreasing the laser power in pulses in accordance with the recording information during the recording mode, when the optical spot If is narrowed down on the disk. Record by doing this. In the reproduction mode, the recording film is irradiated with a laser power that does not cause any change, and the information is read by detecting all of the reflected light. Therefore, in each mode, it is necessary to keep the laser buff constant, and the laser power is controlled so that it is not affected by temperature or the like.

A conventional example will be explained using FIG. 7. Laser 1 is surrounded by a broken line in FIG. The solar cell 2 is included in a moving optical system (not shown) for data retrieval, and is connected to other circuits through connectors or the like. In response to the laser ON command 12, the switching circuit 11 is closed to enter the regeneration state, and the laser 1 emits light. the result,
Backlight enters the solar cell 2 and current flows. Electrician.

is input into the operational amplifier 4 (current-to-voltage conversion) and is converted into a voltage, and a laser driving current flows through Tr 3 accordingly. The laser monitor light is used as a negative feedback signal to control the laser drive current. If only the laser drive current is controlled to be constant, a constant output light amount cannot be obtained because the laser output light amount for the same current varies due to temperature changes.

Therefore, it is necessary to change the current while monitoring the laser light that is actually being emitted, and a backlight that provides a power proportional to the laser's front light (irradiated onto the disk) is used for monitoring. Note that during recording, the switching circuit 7 changes from 01 to . It will be turned off. Furthermore, the Tr8 is driven according to the potential of the recording power setting circuit 6, and the current is adjusted. flows.

Furthermore, during recording, the switching circuit 11 is turned off.

As mentioned above, the power is controlled using the monitor light (backlight, hereinafter abbreviated), and in the event of an abnormality (when a current exceeding the allowable value flows through the laser), the current flowing through the laser is controlled. By detecting (for example, monitoring both ends of a resistor 9.1°), an abnormal state was detected and the laser was turned off. An example of this is shown in Japanese Unexamined Patent Publication No. 189849/1984.

Problems to be Solved by the Invention However, in the past, the laser monitor light is used as a negative feedback signal, so if the monitor light signal is not returned, the negative feedback does not occur and the current exceeds the allowable value. will flow. In this case, the laser power increases instantaneously, and in the detection method described above, detection is performed after the current flows (power exceeding the allowable value is output), and the laser is turned off after a delay time in the circuit. Therefore, in the reproduction mode, a power exceeding the permissible value (recordable 8 degrees) is applied, albeit momentarily, resulting in destruction of recorded data, recording in unrecorded areas, etc. Furthermore, in the recording mode, abnormal power (abnormality in reproduction power control) is added to the recording power, resulting in recording errors and damage or deterioration of the laser. Reasons for not receiving a negative feedback signal (monitor light) include metal fatigue and poor contact in the connector portion due to repeated movement of the optical system.

However, the optical system is constantly moved in order to search all the data, and metal fatigue and poor contact in the connector parts accompanying this movement are unavoidable. In addition to this, a negative feedback signal may not be returned due to an abnormality in the solar cell. If these occur, not only will the laser be destroyed or deteriorated, but recording errors and double writing to the recording section will occur, greatly reducing the data error rate.

Therefore, these pose a huge problem in maintaining system reliability.

Means for Solving the Problems In order to solve the above problems, the present invention uses a laser as a light source and is configured to perform recording or reproducing depending on the magnitude of the output power, and also provides a light source for obtaining a monitor signal corresponding to the output power of the laser. The apparatus includes a detection means, a drive means for driving the laser, an abnormality detection means for detecting an abnormality in the light detection means, and a means for turning off the laser.

Effects The present invention has the above-described configuration, which prevents poor contact of connectors, etc.
It is possible to detect that the monitor signal of the laser backlight is not returned due to an abnormality in the solar cell, etc., and to turn off the laser before the laser outputs abnormal power. Therefore, the laser power above the permissible value is never exceeded even for a moment.

Embodiment FIG. 1 is a configuration diagram of an optical disc device in a first embodiment of the present invention. In FIG. 1, 13 is an operational amplifier, 14 is a comparator, 15 is an amplifier circuit, and the others are conventional examples (7th
Figure). Furthermore, in FIG. 7, the recording circuit section indicated by a dashed line is omitted.

The gist of this embodiment is to detect the dark current of the solar cell 2 (photodiode) used to monitor the backlight of the laser, thereby determining the connection status between the operational amplifier 4 and the solar cell 2 and the operation of the solar cell 2. It is for determining the condition.

If you use a solar cell (photodiode), dark current (
There is a current (current that flows even when no light is incident), and this value is generally on the order of several hundred nanoamperes to several microamperes. Therefore, even in the laser OFF state, dark current flows from the solar cell 2 to the operational amplifier 4 (current-voltage conversion). As a result, a voltage 3 corresponding to a dark current is generated as an offset in the output of the operational amplifier 4. However, since ■3 is minute, it is amplified by the amplifier circuit 16,
Konha v-Yu 14 (7) Comparison v Hell V2f, (Vl
- V3 is set as bond a1. FIG. 2 shows a relationship diagram of each potential.

If (2) satisfies this and the laser is in the OFF state, the comparator 14 compares (V - V ) and (2), and the abnormality detection signal 16 becomes "1-11."

Also, if the connection between the solar cell 2 and the operational amplifier 4 is broken or the solar cell 2 is broken, no dark current will flow, and v2 and ■
1, the abnormality detection signal 16 becomes "L". Therefore, an abnormal state can already be detected when the laser is turned off, and there is no abnormal power output. Similarly, laser O
It is possible to detect abnormal conditions even with N, but after detection, the laser
All you have to do is turn off the N command 12.

Further, FIG. 3 is a hardware configuration diagram of the laser OFF operation. Under normal conditions (dark current is flowing), the output of the comparator 14 is "H" (assumed to be +■A), but due to the diode D1, the potential at the 0 point becomes the forward potential of Dl (approximately 0). .7 ■). Therefore, point A and point 0 (approximately 0
,7V) (7) The voltage divided by the potential difference iR1°R2 is B
This becomes the potential at the point, which drives the laser 1. In the event of an abnormality (dark current does not flow), the comparator 14
The output becomes "L" (assumed to be -vA), and the point A and (-V
The potential difference in A) divided by R and (R2+R3) is
The potential is at point B. At this time, the potential 1Tr3 at point B is a force,
), the laser is turned off.

Next, a second embodiment will be described. FIG. 4 is a block diagram of an optical disc device according to a second embodiment of the present invention.

The gist of this embodiment is to add an offset current to a minute dark current by connecting the solar cell 2Vc resistor (R4) k in parallel to facilitate abnormality detection.

In Figure 4, R4 is added parallel to the solar cell 2 to create an offset current. is flowing. Tsumashi, laser OFF
In this state, (dark current + offset current) flows, and even if no light enters the solar cell 2, a voltage is generated at the output of the operational amplifier 4. At this time, ■. ) Since it becomes a dark current, an abnormal state can be detected without the amplifier circuit used in the first embodiment. The subsequent operations are the same as in the first embodiment and will be omitted.

Next, a third embodiment will be described. FIG. 6 is a block diagram of the optical disc device in the embodiment of FIG. 3. 17 is a detection level, 18 is a switching circuit, and 19 is a delay circuit. In this embodiment, as shown in FIG. 5, the laser ON command 12 is input to the delay circuit 19, and after being delayed by the time "T'', the switching circuit 18 is switched. Therefore, the detection level 17 is teV, v-sa0FF
- Becomes cV4. FIG. 6 is a timing chart of detection levels in the third embodiment. In Fig. 6(a), when the laser is turned on, the detection level is 1 after a delay of time ゛T''.
7 changes from V to ■5 (Figure 6 (b) dashed line)
. Further, when the laser is turned on, the potential at point A changes to v6 (broken line in FIG. 5). ■4 and A when the laser is OFF
By comparing the point potentials (1) (because the dark current is minute), and (4) > (1), it can be determined that the points are normal. Further, if it is normal, the detection level changes to ■5 and the potential at point A changes to ■6 when the laser is turned on. In an abnormal state (current does not flow into the operation up 4), the potential at point A remains at ■1, and ■1>■5 holds true, and the output of the comparator 14 becomes L'''.

After that, the laser is turned off as already shown in other embodiments.
be done.

Effects of the Invention As described above, according to the present invention, even if a monitor signal is not returned due to a poor contact of a connector or the like or an abnormality of a solar cell, there is no possibility of erroneous recording in the recording section or the unrecorded section. In this way, in the present invention, the laser is turned off before the laser power is output, whereas in the past, abnormal output is detected after the laser power exceeding the allowable value is output.

Therefore, it is useful for increasing the reliability of the system, and has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an optical disk device according to a first embodiment of the present invention, FIG. 2 is a diagram showing the relationship between each potential of the device, and FIG. 3 is a circuit for explaining the laser OFF operation of the device. Figures 4 and 5 show the second embodiment of the present invention. FIG. 6 is a circuit diagram of an optical disc device in the third embodiment, FIG. 6 is a timing chart of detection levels of the same device, and FIG. 7 is a circuit diagram of a conventional optical disc device. 1...Laser, 2...Solar cell, 4,
13... operational amplifier, 11.18...
Switching circuit, 15...Amplification circuit, 19...
...Delay circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Figure 5

Claims (5)

[Claims] (1) A light detection means configured to use a laser as a light source and perform recording or reproduction depending on the magnitude of output power, and obtain a monitor signal corresponding to the output power of the laser;
An optical disc device comprising: a driving means for driving the laser; an abnormality detecting means for detecting an abnormality in the light detecting means; and a means for turning off the laser. (2) The optical disc device according to claim 1, wherein the abnormality detection means monitors the dark current of the light detection means. (3) The optical disc device according to claim 1, wherein the abnormality detection means monitors a current flowing through a resistor added in parallel with the optical detection means. (4) Turn the detection level of the abnormality detection means on and off.
The optical disc device according to claim 1, wherein the optical disc device is changed by: (5) The optical disc device according to claim 1, 2, 3, or 4, wherein when an abnormality is detected, the laser is turned off by inputting a cutoff voltage to the drive means.