JPH04123328A - Laser light quantity controller - Google Patents

Abstract

PURPOSE:To quickly switch the quantity of light and to easily design a servo signal reproducing amplifier by providing a driving current correcting circuit and an adding circuit which adds the indication value of a second control filter and the extent of correction of a driving current correcting circuit to supply a driving current to a laser light source. CONSTITUTION:A driving current correcting circuit 112 outputs the extent of correcting to an adding circuit 114 for the purpose of correcting the laser output to cancel the extent of reduction of this laser output due to stop of an HF modulator 110. The adding circuit 114 adds the indication of a control filter 107 and the output of the driving current correcting circuit 111 and outputs the addition result to a driving circuit 108. The driving circuit 108 allows the corrected current to flow in a laser element 101 based on the addition result of the adding circuit 114. Thus, the quantity of light for reproducing and that for recording/erasing are quickly switched, and a circuit to switch the gain in accordance with the quantity of light for recording/erasing is omitting in a servo signal reproducing amplifier which handles a high frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laser drive circuit used in optical disk devices and the like.

BACKGROUND ART FIG. 2 shows the configuration of a conventional laser light amount control device.

In FIG. 2, 201 is a laser element that emits light to a recording medium (not shown).

202 is a light amount detector that is optically coupled to the laser element 201 to detect the amount of light from the laser element 201; 203 is a holding circuit that holds the detection output of the light amount detector 202;

Further, 204 is a target light amount switching device that switches the target light amount;
205 is a control for reducing the drive current of the drive circuit 206 when the current light amount is larger than the target light amount set by the target light amount switch 204, and increasing the drive current of the drive circuit 206 when the current light amount is smaller than the target light amount. It's a filter.

207 is a test light emitting circuit that operates in the servo bite area or laser light amount correction area of the recording medium;
is a high frequency modulator (hereinafter referred to as H'F modulator) attached to the laser element 201, which prevents damage to the laser element 201 by peak current of high frequency modulation when there is no need to reproduce the magneto-optical signal of the recording medium. It is.

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

In Figure 2, the operations of the conventional device can be roughly divided into (
There are two types: 1) reproduction light amount control and (2) recording/erasing light amount control, and these two items will be explained below separately.

(1) Reproduction light amount control The HF modulator 208 is operated to improve the S/N ratio of the magneto-optical signal to be reproduced. The target light amount switch 204 is set to a value corresponding to the reproduction light amount.

Next, the recording medium is rotated, and the light emitted by the laser element 201 is detected by the light amount detection 82 in the servo bite area of the recording medium.
02 receives light, outputs the output of this light amount detector 202 to a holding circuit 203, and holds the current light amount value in this holding circuit 203.

Fl! The JIJ filter 205 controls a drive circuit 206 to reduce the drive current when the current light intensity value is larger than the target light intensity set by the target light intensity switch 204, and to increase the drive current when the current light intensity value is smaller. give instructions to.

The drive circuit 206 drives the HF modulator 208 so that the current indicated by the control filter 205 flows through the laser element 201 .

Through such feedback control, the laser element 20
It operates to make the light amount of 1 equal to the current reproduction light amount.

(2) Recording and erasing light intensity control During recording and erasing, it is necessary to reproduce the magneto-optical signal.
The operation of the HF modulator 208 is stopped in order to prevent the laser element 201 from being damaged by the peak current of the HP modulator.

While the recording medium is rotating and the above-mentioned reproduction light amount control is operating, the target light amount switch 204 is set to a value corresponding to the recording/erasing light amount.

Based on the servo byte area of the recording medium or the laser light intensity correction area ratio, the test light emitting circuit 207 operates and causes a current corresponding to the approximate recording/erasing light intensity to flow through the laser element 201 via the drive circuit 206.

The light intensity detector 202 receives the light emitted by the laser element 201, and thereafter operates in the same manner as the reproduction light intensity control in item (1) above to make the light intensity of the laser element 201 equal to the target recording/erasing light intensity. .

FIG. 3 shows another configuration of the conventional laser light amount control device. 31st! 1, 301 is a laser element that emits light to a recording medium, and 302 is a light amount detector that detects the amount of light from the laser element 301 and is optically coupled to the laser element 301.

303 is a holding circuit that holds the detection output of the light amount detector 302; 304 is a holding circuit that holds the detection output of the light amount detector 302; and 304, when the current light amount value held in the holding circuit 303 is larger than the target reproduction light amount, the drive circuit 305 controls the modulator 310; The drive current is controlled to be small, and if the current light amount value held in the holding circuit 303 is smaller than the target reproduction light amount value, the drive current of the HF modulator 310 is increased to the drive circuit 305. tree(
This is a control filter that controls the

The drive circuit 305 controls the HF modulator 3 so that the current instructed by the control filter 304 flows to the laser element 301.
10.

Further, 306 is a holding circuit that holds the detection output of the light intensity detector 302, and 307 is a holding circuit 3061': when the held current light intensity value is larger than the target recording/erasing light intensity, the drive current of the laser element 301 is reduced. This is a control filter that controls the drive circuit 308 so that the current of the laser element 301 increases when the current light amount value is smaller than the target light amount value.

The drive circuit 308 drives the laser element 301 according to instructions from the control filter 307, and
This is a drive circuit for causing current to flow in the laser element 301 according to the instruction value of 07.

Reference numeral 309 denotes a test light emitting circuit that operates in the laser light intensity correction area of the recording medium. When this test light emitting circuit 309 operates, the drive circuit 308 drives the HF modulator 310 so that approximately current flows through the laser element 301. It is supposed to be done.

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

In Figure 3, the operations of the conventional device can be roughly divided into (A
There are two types: () reproduction light amount control and (B) recording and erasing light amount control, and these two items will be explained below separately.

(A) Reproduction light amount control The HF modulator 310 is operated in the same way as in the conventional example shown in FIG. 2. A recording medium (not shown) is rotated, a light amount detector 302 receives light emitted by a laser element 301 in a servo bite area of the recording medium, and a holding circuit 303 holds the current light amount value.

The control filter 305 instructs to decrease the driving current of the laser element 301 when the current light amount value is larger than the target reproduction light amount, and to increase the driving current of the laser element 301 when tJz is smaller. is output to the drive circuit 305.

The drive circuit 306 drives the HF modulator 310 so that the current indicated by the control filter 304 flows through the laser element 301.

Through such feedback control, the laser element 30
It operates to make the light amount of 1 equal to the current reproduction light amount.

(B) Recording and erasing light amount control In this case as well, the operation of the HF modulator 310 is stopped as in the conventional example shown in FIG. The recording medium rotates and the above (
When the reproduction light amount control described in section A) is operating, the test light emitting circuit 309 operates in the laser light amount correction area of the recording medium, and a current corresponding to the approximate recording and erasing light amount is supplied to the laser element 301 via the drive circuit 308. flow.

A light amount detector 302 receives the light emitted by the laser element 301, and a holding circuit 306 holds the current light amount value.

The control filter 307 makes the drive current of the laser element 301 smaller when the current light amount value is larger than the target recording/erasing light amount, and conversely increases the drive current of the laser element 301 when it is smaller. , outputs an instruction to the drive circuit 308.

The drive circuit 306 causes a current indicated by the control filter 307 to flow through the laser element 301.

Therefore, the total of the current due to the reproduction light amount control and the current due to the recording/erasing control flows through the laser element 301.

Through such feedback control, the laser element 3
It operates to make the light amount of 01 equal to the target recording/erasing light amount.

Figure 2 above, Figure 31! ] As shown in the two conventional examples, it is also possible to make the reproduction light amount and the recording/erasing light amount each follow the target value using the conventional laser light amount control device.

However, the problem to be solved by the invention is the above-mentioned 21st problem! In the conventional laser light intensity side leg device of I, the same control loop is used for reproduction light intensity control and recording/erasing light intensity control, so the time required to switch the target light intensity from reproduction to recording/erasing, or vice versa, is shorter. There was a problem in that it took a long time, which was determined by the response time of the system.

Furthermore, in order to read the servo signal using the reproduction light intensity during playback and the recording erase light intensity during recording erasing, the servo signal reproducing amplifier, which is separate from the laser light intensity control device, is equipped with a gain that corresponds to the recording erase light intensity. There was a problem in that it was necessary to add a switching circuit, and the circuit for the high frequency part became large.

In addition, in the conventional laser light amount control device shown in FIG. 3, when the light amount is switched and the HFRWR unit 310 is switched between operation and stop, an offset occurs in the output of the light amount detector 302, resulting in a large tracking error in the recording/erasing light amount. In addition, there is a problem in that absorbing the power supplied from the HF modulator 310 requires a relatively long settling time determined by the response time of the system.

The present invention solves these conventional problems, and enables high-speed switching of the light amount, and improves the operation of the HF modulator.
It is an object of the present invention to provide an excellent laser light amount control device that can correct the difference in light amount due to stoppage and does not make the design of a servo signal regeneration amplifier that handles high frequencies complicated.

Means for Solving the Problems In order to achieve the above object, the present invention provides a light amount detection means for detecting the light amount of a laser light source, and a first holding means for holding a first light amount value detected by the light amount detection means. and, when controlling the reproduction light quantity, if the current light quantity value held by the first holding means is larger than the target reproduction light quantity, outputting an instruction to decrease the drive current of the laser light source; a first control filter that outputs an instruction to increase the drive current of the laser light source when the current light amount value held by the holding means is smaller than the target reproduction light amount; a first driving means for driving a high-frequency modulator to flow a driving current to the laser light source with a driving current based on the recording data; a test light emitting circuit that operates in the laser light amount correction area of the recording medium in the erasing light amount control means to cause the second driving means to flow a current approximately equivalent to the recording erasing light amount into the laser light source; a light amount correction circuit that outputs a correction amount that offsets the offset of the amount of light detected by the light amount detecting means due to the stoppage of the high frequency modulator, and the laser detected by the light amount detecting means when the test light emitting circuit is activated a second holding means for holding a light amount value obtained by adding the detected value of the amount of light emitted from the light source, the detected value of the amount of emitted light from the laser light source, and the correction amount; a second control filter for instructing a driving current value of the laser light source in accordance with whether the light amount value is larger or smaller than a target recording/erasing light amount; and a second control filter for controlling the driving current value of the laser light source when the high-frequency modulator is stopped during the recording/erasing operation. a drive current correction circuit that outputs a correction amount sufficient to offset the decrease in the amount of emitted light; and a drive current correction circuit that outputs a correction amount sufficient to offset the decrease in the amount of emitted light; The driving means is configured to include an addition circuit for supplying a driving current to the laser light source.

Therefore, according to the present invention, by correcting the detected light amount and the laser drive current, the output time of the light amount detection means that changes depending on the operation and stop of the HF modulator and the current-light output of the laser element are corrected. Changes in characteristics can be corrected, and the switching between the reproduction light amount and the recording/erasing light amount can be performed at high speed.In addition, a gain switching circuit according to the recording/erasing light amount can be added to the servo signal reproduction amplifier that handles high frequencies. This has the effect that it can be omitted.

Embodiment FIG. 1 shows an embodiment of the present invention. In FIG. 1, 101 is a laser element serving as a laser light source, which emits light to a recording medium. A light amount detector 102 is optically coupled to the laser element 101 and detects the amount of light from the laser element 101.

Further, 103 is a holding circuit that holds the light amount value detected by the light amount detector 102, and 104 is a holding circuit that holds the light amount value detected by the light amount detector 102. This is a control filter that outputs an instruction to increase or decrease the laser drive current of the element 101 to the drive circuit 105.

The drive circuit 105 drives the HF modulator 110 so that the drive current of the laser element 101 increases or decreases based on instructions from the control filter 104.

Further, 113 is an addition circuit that adds the light amount value detected by the light amount detector 102 and the correction amount output from the light amount correction circuit 111. This is to output to the adding circuit 113 a correction amount sufficient to offset the offset of the amount of detected light caused by the stoppage.

106 is a holding circuit that holds the light intensity value output from the addition circuit 113; 107 is a holding circuit that holds the light intensity value outputted from the adding circuit 113; This is a control filter that outputs an instruction to increase or decrease the driving current of the laser element 101 to the adding circuit 114.

The adder circuit 114 adds the output of the control filter 107 and the output of the drive current correction circuit. This outputs a correction amount sufficient to offset the decrease.

108 is a drive circuit that inputs the output of the adder circuit 114 and drives the laser element 101 when controlling the light amount during recording and erasing;
Reference numeral 109 denotes a test light emitting circuit that operates in the laser light amount correction area of the recording medium during reproduction light amount control, and when this test light emitting circuit 109 operates, the drive circuit 10g becomes H.
Instead of driving the F modulator 110, a current corresponding to approximately the amount of recording/erasing light is caused to flow through the laser element 101.

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

In FIG. 1, the operations can be broadly divided into two: (a) reproduction light amount control and (b) recording and erasing light amount control, and will be explained below by dividing into these two items (a) and (b).

(a) Reproduction light amount control The HF modulator 110 is operated to improve the S/N ratio of the magneto-optical signal to be reproduced. Next, rotate the recording medium,
A light amount detector 102 receives light emitted by a laser element 101 in a servo bite area of a recording medium, outputs the detection output to a holding circuit 103, and holds the current light amount value.

When the current light amount value held by the holding circuit 103 is larger than the target reproduction light amount, the control filter 104 controls
An instruction is issued to the drive circuit 105 to reduce the drive current of the laser element 101, or to increase the drive current of the laser element 101 when the drive current is small.

The drive circuit 105 drives the HF modulator 110 so that the current indicated by the control filter 104 flows through the laser element 101.

Through such feedback control, the laser element 1
It operates to make the light amount of 01 equal to the current reproduction light amount.

(b) Recording and erasing light control During recording and erasing, there is no need to reproduce the magneto-optical signal.
The operation of the HF modulator 110 is also stopped in order to prevent the laser element 101 from being damaged by the peak current of the HF modulator.

When the recording medium is rotating and the reproduction light amount control described in item (a) above is operating, the test light emitting circuit 109 operates in the laser light amount correction area of the recording medium, and its output is used to control the laser beam via the drive circuit 108. A current corresponding to the approximate amount of recording/erasing light is applied to the element 101.

Corresponding to this current, the light amount detector 102 receives the light emitted by the laser element 101, and adds the detection output to the adding circuit 1.
Output to 13.

On the other hand, the light amount correction circuit 111 outputs an output to the addition circuit 113 in order to add a correction to the output of the light amount detector 102 to offset the offset of the detected light amount caused by the HFR II device 110 body 10. , the output of the light amount detector 102 and the output of the light amount correction circuit 111 are added, and the addition result is output to the holding circuit 106, which holds the corrected light amount value.

The control filter 107 reduces the driving current of the laser element 101 when the current light amount held in the holding circuit 106 is larger than the recording/erasing light amount, and vice versa. An instruction is issued to the adder circuit 104 to increase the value.

The drive current correction circuit 112 outputs an output to the addition circuit 114 in order to add correction to the current to offset the decrease in laser output caused by stopping the HF modulator 110.

Thereby, the addition circuit 114 adds the instruction of the control filter 107 and the output of the drive current correction circuit 111, and outputs the addition result to the drive circuit 108.

The drive circuit 108 causes a corrected current to flow through the laser element 101 based on the addition result of the addition circuit 114. As a result, the laser element 101 receives a current due to the reproduction light amount control,
The sum of the current due to the recording/erasing control and the correction current related to stopping the HF modulator 110 flows.

Through such feedback control, the laser element 1
It operates to make the light amount of 01 equal to the target recording/erasing light amount.

In this way, according to the above embodiment, both the offset of the detected light amount and the decrease in laser output caused by stopping the HF modulator 110 during recording erasing are offset by the light amount correction circuit 111 and the drive current correction circuit 112, respectively. Therefore, not only the amount of playback light but also the amount of recorded data erased,
This has the effect of being able to follow the correct target value.

Further, according to the above embodiment, at the same time as switching the light amount,
Since the above correction is applied, there is an advantage that the laser output can be rapidly increased to the target light amount.

Effects of the Invention As described above, according to the present invention, a light amount detecting means for detecting the light amount of a laser light source, a first holding means for holding a first light amount value detected by the light amount detecting means, and a light amount detecting means for holding a first light amount value detected by the light amount detecting means; , when the current light amount value held by the first holding means is larger than the target reproduction light amount, outputting an instruction to decrease the driving current of the laser light source; A first control filter outputs an instruction to increase the driving current of the laser light source when the current light amount value is smaller than the target reproduction light amount; a first driving means for driving a high frequency modulator to flow a driving current to the light source; a second driving means for supplying a driving current to the laser light source when controlling the recording and erasing light amount; a test light emitting circuit that operates in a laser light intensity correction region of the medium and causes a current approximately equivalent to the recording erase light amount to flow into the laser light source to the second driving means; and stopping the high frequency modulator during the recording erase operation. a light amount correction circuit that outputs a correction amount that offsets the offset of the amount of light detected by the light amount detecting means, and detection of the amount of light emitted from the laser light source detected by the light amount detecting means during the operation of the test light emitting circuit; a second holding means for holding a light amount value obtained by adding the detected value of the emitted light amount of the laser light source and the correction amount; a second control filter for instructing the drive current value of the laser light source in accordance with whether the light intensity is larger or smaller than the light intensity; a drive current correction circuit that outputs an amount of correction sufficient to offset the amount of correction; The configuration includes an addition circuit that supplies a drive current.

Therefore, by correcting the detected light amount and the laser drive current, the output time of the light amount detection means that changes depending on whether the HF modulator is activated or stopped and the change in the current-light output characteristics of the laser element are corrected. This makes it possible to quickly switch between the reproduction light amount and the recording/erasing light amount, and it is also possible to omit a gain switching circuit according to the recording/erasing light amount in a servo signal reproducing amplifier that handles high frequencies. It has this effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of a laser light amount control device in an embodiment of the present invention, and FIGS. 2 and 3 are
FIG. 3 is a block diagram showing a schematic configuration of a conventional laser light amount control device. 101... Laser element, 102... Optical detector, l
○3.106...Holding circuit, 104.107...Control filter, 105.108...Drive circuit, 109-
...Test light emitting circuit, 110...HF modulator, 111
... light amount correction circuit, 112 ... drive current correction circuit,
113...Addition circuit.

Claims (1)

[Scope of Claims] A light amount detection means for detecting the light amount of a laser light source, a first holding means for holding a first light amount value detected by the light amount detection means, and the first holding means when controlling the reproduction light amount. When the current light amount value held by the first holding means is larger than the target reproduction light amount, an instruction to reduce the drive current of the laser light source is output, and the current light amount value held by the first holding means is a first control filter that outputs an instruction to increase the drive current of the laser light source when it is smaller than the target reproduction light amount; and a drive current that flows through the laser light source with a drive current based on the instruction of the first control filter. a first driving means for driving a high-frequency modulator for controlling the recording and erasing light quantity; a second driving means for supplying a driving current to the laser light source when controlling the recording and erasing light quantity; and a laser light quantity correction area of the recording medium in the recording and erasing light quantity control means. a test light emitting circuit that operates to cause the second driving means to flow a current approximately equivalent to the amount of recording and erasing light into the laser light source; and the light amount detecting means that detects the amount of light when the high frequency modulator is stopped during the recording and erasing. a light amount correction circuit that outputs a correction amount that offsets the offset of the detected amount of light from the laser light source; a second holding means for holding a light amount value obtained by adding the detected value of the emitted light amount of and the correction amount; and whether the light amount value held by the second holding means is larger or smaller than the target recording erasing light amount. a second control filter that instructs the drive current value of the laser light source in accordance with the above, and a correction amount sufficient to offset a decrease in the amount of light emitted by the laser light source due to the stoppage of the high frequency modulator during the recording erasure. a drive current correction circuit that outputs a drive current correction circuit; and an addition that causes the second drive means to supply a drive current to the laser light source by adding the instruction value of the second control filter and the correction amount of the drive current correction circuit. A laser light amount control device equipped with a circuit.