JPH031333A - Optical information reproducing device - Google Patents

Abstract

PURPOSE:To accomplish the stable actuation of a semiconductor laser by outputting the last output of a driving control signal which is held in a hold output circuit part when a detected reflection returning light quantity is continuously less than a set value because there is dust or stain on the recording surface of an optical medium. CONSTITUTION:When there is dust or stain on an optical card, the reflection returning light quantity from the optical card which is detected by a photodetector 9 for an auxiliary monitor is continuously decreased, so that output voltage from a 2nd current/voltage circuit 16 is less than a hold set voltage and a hold command signal is outputted from a comparator 18. A sample-hold circuit 19 holds and outputs a voltage signal given from an amplification circuit 15 just before with the hold command signal. Such output is continued until the dust or the stain is eliminated, the reflection returning light quantity is increased and the output of the hold command signal from the comparator 18 is stopped. Therefore, a driving current for the semiconductor laser is kept constant and the output is maintained to be low even when the output of the detection signal of a photodetector 2 for monitor is lowered based on the dust or the stain. Thus, the semiconductor laser is stably actuated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical information reproducing device configured as an optical card recording/reproducing device or the like.

(Prior Art) FIG. 7 shows the configuration of a conventional optical card recording/reproducing device, in which 100 is a semiconductor laser as a light source, and a monitoring photodetector 101 is integrally provided on the rear side. There is. 102 is a collimating lens that converts the emitted light from the semiconductor laser 100 into parallel light, and lO3 is an objective lens that collects the parallel light and focuses it on the optical card 104. Both lenses 102 and 103 constitute an optical system. There is. 10
Reference numeral 5 denotes a signal processing circuit, which is provided to output a reproduction information signal based on a detection signal of the amount of returned light corresponding to the state of the pit 104a in the optical card 104 provided from the monitoring photodetector 101.

106 is an APC circuit (automatic output control circuit), which outputs a drive control signal so as to always keep the output of the semiconductor laser 100 constant based on the detection signal of the amount of returned light given from the monitoring light detection ztot. It is provided. The APC circuit 106 is provided to respond to changes in the output of the semiconductor laser 100 due to changes in environmental temperature, and because it is equipped with a low-pass filter, it does not respond to changes in the amount of returned light due to the pits 104a of the optical card 104. It is configured as follows.

(Problem to be solved by the invention) However, in the case of the above optical card recording/reproducing device, A.
Since the PC circuit 106 is provided, there are the following problems. The problem will be explained with reference to FIG.

FIG. 8 is a diagram showing the relationship between the amount of returned light detected by the monitoring photodetector 101, the drive current as a drive control signal output by the APC circuit 106, and the output of the semiconductor laser 100.

In the section indicated by , the drive current is maintained at a predetermined level, and the semiconductor laser! The output of 00 is also basically maintained at a predetermined level.

On the other hand, in the section indicated by Y, there is dust, dirt, etc. on the recording surface of the optical card 104, and the amount of returned light decreases continuously.
In this case, the APC circuit 10G performs a corresponding operation, so the drive current is increased while the amount of returned light is decreasing.
Correspondingly, the output of the semiconductor laser 100 is also increased.

Then, when transitioning from the above-mentioned section X to section Y, and from section Y to section X, the output of the semiconductor laser lOO changes to Ct,
It changes significantly at Ct, and C.

This is not so much of a problem in the case of a decreasing change in
If there is an excessive increase and change as in C1, it will damage the optical card 104, and if the output exceeds the rated maximum light output of the semiconductor laser 100, the semiconductor laser 100 itself will be destroyed or deteriorated. It became a thing.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an optical information reproducing device in which the output of a semiconductor laser is not affected by surface conditions such as dust and dirt on an optical medium.

(Means for Solving the Problems) In order to solve the above object, the invention of claim (1) provides a semiconductor laser as a light source that integrates a monitoring photodetector, and a semiconductor laser as a light source integrated with a monitoring photodetector. an optical system that guides light from the optical medium to an optical medium and guides reflected light from the optical medium to the semiconductor laser again; and an optical system that is connected to the semiconductor laser and reproduces based on a detection signal from the monitoring photodetector. a signal processing circuit that forms and outputs an information signal; and a semiconductor laser automatic output control circuit that is connected to the semiconductor laser and outputs a drive control signal to the semiconductor laser based on a detection signal from the monitoring photodetector. An optical information reproducing device comprising: an auxiliary monitoring photodetector for detecting the amount of reflected return light on the optical medium; A structure is adopted in which a holding output circuit unit is integrally provided, which holds and outputs the immediately preceding drive control signal output when the amount of returned light continues to fall below a set value.

In the invention of claim (2), a semiconductor laser as a light source is integrated with a monitoring photodetector, light from the semiconductor laser is guided to an optical medium, and light reflected from the optical medium is returned to the semiconductor laser. an optical system connected to the semiconductor laser, a signal processing circuit configured to form and output a reproduction information signal based on a detection signal from the monitoring photodetector, and a signal processing circuit connected to the semiconductor laser. , an optical information reproducing apparatus comprising: an automatic output control circuit for a semiconductor laser that outputs a drive control signal to the semiconductor laser based on a detection signal from the monitoring photodetector; The present invention is configured such that a holding output horn circuit unit is integrally provided to hold and output the immediately preceding drive control signal output when the amount of detected reflected return light based on the detection signal continues to be less than a set value.

(Function) According to the configuration of the invention of claims (1) and (2) above, if there is dust or dirt on the recording surface of the optical medium and the amount of detected reflected return light continues to fall below the set value, The automatic output control circuit holds and outputs the immediately previous drive control signal output by a holding operation of the holding output circuit section.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of an optical card recording/reproducing device.

In the figure, reference numeral 1 denotes a semiconductor laser, which is integrally equipped with a monitoring photodetector 2. 3 is a collimating lens,
4 is an objective lens, and 5 is a signal processing circuit.

The configuration including the above-mentioned elements is similar to that shown in the conventional example.

The present invention includes an auxiliary monitor light source 7, an auxiliary monitor photodetector 8, and a collimating lens 9.
As shown in FIG. 2, an APC circuit 11 is provided which integrally includes a holding output circuit section 10 that responds to a detection signal from the auxiliary monitoring photodetector 8.

The auxiliary monitor light source 7 is provided to irradiate a large area including the part of the optical card 6 where the light from the semiconductor laser 1 is focused from an oblique position, and is auxiliary to receive the reflected light from the optical card 6. A monitoring photodetector 8 is provided.

The APC circuit 11 converts an output current as a detection signal given from the monitoring photodetector 2 into a voltage signal.
a current/voltage conversion circuit 12; a subtraction circuit 13 that performs subtraction between the set voltage provided from the voltage setting section and the voltage provided from the first voltage/current conversion circuit 12; and a subtraction voltage signal provided from the subtraction circuit 13. A low-pass filter 14 that cuts fluctuations in the high frequency portion of the filter, and an amplifier circuit +5 that amplifies the signal from the low-pass filter 14.
, a second current/voltage conversion circuit 16 that converts the output current as a detection signal given from the auxiliary monitoring photodetector 8 into a voltage signal, and a hold setting voltage and a second current/° given from the hold voltage setting section. A comparator 18 compares the voltage given from the voltage circuit 6 and outputs a hold command signal if the given voltage is lower than the hold setting voltage, and when the hold command signal is given from the comparator 18, the immediately preceding amplifier circuit A sample and hold circuit 19 holds and outputs the signal given from the sample and hold circuit 15 as a current value command signal, and a current generation circuit 20 generates a drive current based on the current value command signal from the sample and hold circuit 19 and supplies it to the semiconductor laser I. It is configured.

Above APC circuit! ! In, the second current/voltage conversion circuit 16, the comparator 18 and the sample hold circuit 1
9 constitutes a holding output circuit $10.

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

In the section indicated by X where there is no dust or dirt on the optical card 6, the amount of reflected light returned from the optical card 6 detected by the auxiliary monitoring photodetector 8 is maintained at a constant level, and the second current /
The output voltage from the voltage circuit 16 exceeds the hold setting voltage, and no hold command signal is output from the comparator 18, so that the voltage signal from the amplifier circuit 15 is directly transmitted to the current generation circuit 20 via the sample and hold circuit 19.
The output of the semiconductor laser 1 is basically maintained at a constant level. Auxiliary monitor photodetector 8 in the above
Since the amount of reflected light returned from the optical card 6 detected in the above is detected in a large area of the optical card 6, it is hardly affected by the presence or absence of pits in the optical card 6.

On the other hand, in the section indicated by Y where there is dust or dirt on the optical card 6, the amount of reflected return light from the optical card 6 continues to decrease, so the output voltage from the second current/voltage circuit 16 is set to hold. As a result, the comparator 18 outputs a hold command signal. This hold command signal causes the sample and hold circuit I9 to hold and output the voltage signal given from the amplifier circuit 15 just before. It continues until the hold command signal is output from or it is stopped.

Therefore, even if there is a drop in the detection signal output from the monitoring photodetector 2 due to dust or dirt on the optical card 6, the driving current of the semiconductor laser l is maintained constant without being affected by the drop, and the drive current of the semiconductor laser l is maintained constant. As a result, the output of the semiconductor laser l is also maintained low, which causes the conventional problems c,...
Semiconductor laser in C2! No output change occurs either.

In the above, the reason why the drive current of the semiconductor laser 1 becomes a little high while the hold command signal is being output is because the hold timing is slightly delayed and the hold output is performed at the time when the drive current starts to increase a little.

FIG. 4 shows another embodiment, in which the objective lens 4
A half mirror 30 is interposed between the collimating lens 3 and the collimator lens 3, and a part of the reflected return light of the semiconductor laser I is captured by the half mirror 30 into the auxiliary monitoring photodetector 8. In other words, the auxiliary monitor shown in FIG. The configuration is such that a semiconductor laser 1 is also used as a monitor light source 7. The configuration of the APC circuit in this example is almost the same as that shown in the above example, but in this example, the reflected return light of the semiconductor laser beam is used, and the amount of the returned light is proportional to the pit. Since the output voltage changes, it is necessary to provide a low-pass filter also in the holding output circuit section so as not to be affected by the change.

FIG. 5 shows a circuit block diagram of yet another embodiment.

In this device, in the APC circuit 11, a signal obtained from the low-pass filter 4 is compared with a hold setting voltage by a comparator I8, and a hold command signal is given to the sample and hold circuit 19.
The configuration does not use the auxiliary monitoring photodetector 8 shown in the second embodiment.

In this embodiment, the follow-up frequency of the APC circuit 11 is further lowered by using the auxiliary low-pass filter 31, so that the change in the drive current of the semiconductor laser l when a hold command is given is reduced. It has become. Furthermore, when the hold is released due to the removal of dust, dirt, etc., the follow-up frequency of the APC circuit 11 is set low by the auxiliary low-pass filter 31, so the output of the semiconductor laser 1 will slightly overshoot, but it will not be that much. No problems occur.

FIG. 6 shows a modified embodiment of the one shown in FIG. 5, in which the low-pass filter 1 is
4 and the output from the sample and hold circuit 19 are switched and output. The switching command signal is outputted from the comparator 18 at the same time as the hold command signal. With this configuration, the overshoot phenomenon due to the follow-up delay in the embodiment shown in FIG. 5 described above can be suppressed to a lower level. Become.

(Effect of the invention) Therefore, claim (I) and claim (2) of the present invention
According to the invention, if there is dust or dirt on the recording surface of the optical medium,
When the amount of detected reflected return light continues to fall below the set value, the automatic output control circuit retains and outputs the previous drive control signal output by the retaining operation of the retaining output circuit section. The output of the semiconductor laser is not affected by the surface condition of the semiconductor laser, and the semiconductor laser can operate stably.

[Brief explanation of drawings]

1 to 6 relate to embodiments of the present invention, in which FIG. 1 is a configuration diagram of an optical card recording/reproducing device, FIG. 2 is a block circuit diagram thereof, and FIG. 3 is a return view, a semiconductor laser drive current, and a semiconductor laser. FIG. 4 is a block diagram of the second embodiment, FIG. 5 is a block circuit diagram of the third embodiment, and FIG. 6 is a block circuit diagram of the fourth embodiment. Figure 7 is a configuration diagram of a conventional example of an optical card recording/reproducing device;
The figure is a diagram corresponding to FIG. 3 in the conventional example. DESCRIPTION OF SYMBOLS 1...Semiconductor laser, 2...Photodetector for monitoring, 3...Collimating lens (optical system), 4...Objective lens (optical system), 5...Signal processing circuit, 6...・Optical card, 7...Light source for auxiliary monitor, 8...Photodetector for auxiliary monitor, 11...Automatic output control circuit (APC circuit)

Claims (2)

[Claims] (1) A semiconductor laser as a light source that integrates a monitoring photodetector; an optical system that guides light from the semiconductor laser to an optical medium and guides reflected light from the optical medium to the semiconductor laser again; and the semiconductor laser. a signal processing circuit connected to the laser and configured to form and output a reproduction information signal based on a detection signal from the monitoring photodetector; and a signal processing circuit connected to the semiconductor laser and configured to output a reproduced information signal based on the detection signal from the monitoring photodetector; an automatic output control circuit for a semiconductor laser that outputs a drive control signal to the semiconductor laser based on a detection signal of the optical information reproducing apparatus, the optical information reproducing device comprising: an auxiliary monitoring photodetector that detects the amount of reflected light on the optical medium; and a holding output circuit unit that causes the automatic output control circuit to hold and output the immediately previous drive control signal output when the amount of detected reflected return light from the auxiliary monitoring photodetector continues to be below a set value. An optical information reproducing device, characterized in that it is integrally provided with. (2) a semiconductor laser as a light source that integrates a monitoring photodetector; an optical system that guides light from the semiconductor laser to an optical medium and guides reflected light from the optical medium to the semiconductor laser again; and the semiconductor laser. a signal processing circuit connected to the laser and configured to form and output a reproduction information signal based on a detection signal from the monitoring photodetector; and a signal processing circuit connected to the semiconductor laser and configured to output a reproduced information signal based on the detection signal from the monitoring photodetector; an automatic output control circuit for a semiconductor laser that outputs a drive control signal to the semiconductor laser based on a detection signal, wherein the automatic output control circuit outputs a detected reflected return light amount based on the detection signal. 1. An optical information reproducing apparatus, characterized in that an optical information reproducing apparatus is integrally provided with a holding output circuit section that holds and outputs the immediately preceding drive control signal output when the output signal continues to fall below a set value.