JP2507162B2 - Laser light intensity control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser drive circuit used in an optical disk device or the like.

2. Description of the Related Art FIG. 2 shows the configuration of a conventional laser light amount control device.

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

202 is a laser element 20 that is optically coupled to the laser element 201.
A light amount detector that detects the light amount of 1 and 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 for switching the target light amount, 2
05 indicates that when the current light amount is larger than the target light amount set by the target light amount switch 204, the drive current of the drive circuit 206 is small, and conversely, when it is smaller than the target light amount, the drive circuit 206
Is a control filter for increasing the drive current of the.

Reference numeral 207 is a test light emitting circuit that operates in the servo bite area or laser light amount correction area of the recording medium, and 208 is attached to the laser element 201 and is a high frequency modulation peak when it is not necessary to reproduce the magneto-optical signal of the recording medium. A high frequency modulator (hereinafter referred to as HF
It is called a modulator).

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

In FIG. 2, the operation of the conventional device is roughly divided into
There are two types of control, (1) reproduction light amount control and (2) recording / erasing light amount control. These two items will be described below separately.

(1) Reproduction light amount control In order to improve the S / N ratio of the magneto-optical signal to be reproduced, the HF modulator 208
To work. 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 from the laser element 201 is detected by the light amount detector 202 in the servo bite area of the recording medium.
The light amount is received, and the output of the light amount detector 202 is output to the holding circuit 203, and the holding circuit 203 holds the current light amount value.

The control filter 205 is configured so that the current light quantity value is the target light quantity switch 2
When it is larger than the target light quantity set in 04, the drive circuit 206 is instructed to decrease the drive current, and conversely, when the light quantity is smaller than the target light quantity, increase the drive current.

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.

With such feedback control, the laser device 20
It operates to make the light intensity of 1 equal to the current reproduction light intensity.

(2) Recording / erasing light amount control Since it is not necessary to reproduce the magneto-optical signal during recording / erasing, it is also for preventing the laser element 201 from being damaged by the peak current of the HF modulator. Stop the operation.

In the state where the recording medium rotates and the above-described reproduction light amount control is working, the target light amount switching unit 204 is set to a value corresponding to the recording / erasing light amount.

The test light emission circuit 207 operates in the servo bite area or the laser light amount correction area of the recording medium, and a current corresponding to the recording / erasing light amount is supplied to the laser element 201 via the drive circuit 206.

The light amount detector 202 receives the light emitted from the laser element 201, and thereafter, in the same manner as the reproduction light amount control in the above item (1),
It operates so that the light quantity of the laser element 201 becomes equal to the target recording / erasing light quantity.

FIG. 3 shows another configuration of the conventional laser light amount control device. In FIG. 3, reference numeral 301 denotes a laser element, which emits light to a recording medium, and 302, a light amount detector which detects the light amount of the laser element 301, which is optically coupled to the laser element 301.

Reference numeral 303 denotes a holding circuit that holds the detection output of the light quantity detector 302, and 304 denotes a modulator 310 for the drive circuit 305 when the current light quantity value held by the holding circuit 303 is larger than the target reproduction light quantity. Control to reduce the drive current,
When the current light amount value held in the holding circuit 303 is smaller than the target reproduction light amount value, the drive circuit 305 is set to H
It is a control filter that controls to increase the drive current of the F modulator 310.

The drive circuit 305 drives the HF modulator 310 so that the current designated by the control filter 304 flows through the laser element 301.

Further, 306 is a holding circuit for holding the detection output of the light amount detector 302, 307 is a laser element 30 when the current light amount value held in the holding circuit 306 is larger than the target recording / erasing light amount.
The drive circuit 308 is controlled to reduce the drive current of 1.
On the contrary, when the current light quantity value is smaller than the target light quantity value, the drive circuit 3 is set so that the current of the laser element 301 becomes large.
It is a control filter that controls 08.

The drive circuit 308 is a drive circuit for driving the laser element 301 in accordance with an instruction from the control filter 307 and flowing a current according to the instruction value of the control filter 307 to the laser element 301.

Reference numeral 309 denotes a test light emitting circuit that operates in the laser light amount correction region of the recording medium. When the test light emitting circuit 309 operates, the drive circuit 308 drives the HF modulator 310 so that a current is supplied to the laser element 301. It is supposed to do.

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

In FIG. 3, the operation of the conventional device is roughly divided into two types: (A) reproduction light amount control and (B) recording / erasing light amount control. These two items will be described below.

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

The control filter 305 gives an instruction to decrease the drive current of the laser element 301 when the current light quantity value is larger than the target reproduction light quantity, and conversely to increase the drive current of the laser element 301 when it is small. 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.

By such feedback control, the laser device 30
It operates so that the light intensity of 1 becomes equal to the current playback light intensity.

(B) Control of recording / erasing light amount In this case, the HF modulator is also used, as in the conventional example shown in FIG.
Stop the operation of 310. In the state where the recording medium is rotated and the reproduction light amount control of the above item (A) is working, the test light emitting circuit 309 operates in the laser light amount correction area of the recording medium, and the laser element 301 is roughly passed through the drive circuit 308. A current corresponding to the amount of recording / erasing light is applied.

The light amount detector 302 receives the light emitted from the laser element 301, and the holding circuit 306 holds the current light amount value.

The control filter 307 reduces the drive current of the laser element 301 when the current light quantity value is larger than the target recording / erasing light quantity, and vice versa.
An instruction is output to the drive circuit 308 to increase the drive current of 1.

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

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

By such feedback control, laser device
It operates so that the light amount of 301 is equal to the target recording / erasing light amount.

As shown in the two conventional examples of FIGS. 2 and 3 above,
The conventional laser light amount control device can also make the reproduction light amount and the recording / erasing light amount follow the target values.

However, in the conventional laser light amount control device of FIG. 2 described above, the same control loop is used for the reproduction light amount control and the recording / erasing light amount control. , Or vice versa, there is a problem that it takes a long time determined by the response time of the system.

Further, since the reading of the servo signal is performed by the reproduction light amount at the time of reproduction and at the recording / erasing light amount at the time of recording / erasing, the servo signal reproducing amplifier located in a part different from the laser light amount control device has a gain corresponding to the recording / erasing light amount. Since it is necessary to add a switching circuit, there is a problem that the circuit in the high frequency part becomes large.

Further, in the conventional laser light amount control device of FIG.
Along with the switching of the light amount, when the operation and stop of the HF modulator 310 are switched, an offset generated in the output of the light amount detector 302 causes a large tracking error in the recording / erasing light amount, and the power supplied from the HF modulator 310 is changed. There was a problem that a relatively long settling time determined by the response time of the system was required for absorption.

The present invention is to solve such conventional problems, it is possible to switch the light amount at high speed, the operation of the HF modulator,
An object of the present invention is to provide an excellent laser light amount control device capable of correcting the difference in light amount due to stoppage and not complicating the design of a servo signal reproducing amplifier that handles high frequencies.

Means for Solving the Problems In order to achieve the above object, the present invention provides a light quantity detecting means for detecting the light quantity of a laser light source, and a first holding means for holding a first light quantity value detected by the light quantity detecting means. During reproduction light amount control, when the current light amount value held by the first holding means is larger than the target reproduction light amount,
Outputs an instruction to reduce the drive current of the laser light source,
Further, when the current light quantity value held by the first holding means is smaller than the target reproduction light quantity, a first control filter which outputs an instruction to increase the drive current of the laser light source, and the first control filter First driving means for driving the high frequency modulator in order to supply a driving current to the laser light source with the driving current based on the instruction of the control filter, and second driving for supplying the driving current to the laser light source during recording / erasing light amount control. A test light-emitting circuit for causing the recording / erasing light quantity control means to operate in a laser light quantity correction area of a recording medium and to cause a current corresponding to the recording / erasing light quantity to flow into the laser light source to the second drive means. A light amount correction circuit that outputs a correction amount that cancels out an offset amount of the light amount detection amount of the light amount detection means when the high frequency modulator is stopped during the recording and erasing; The detected value of the light emission amount of the laser light source detected by said light quantity detecting means during the operation of the bets emission circuit,
Second holding means for holding a light quantity value obtained by adding the detected value of the emitted light quantity of the laser light source and the correction quantity, and the light quantity value held by the second holding means is larger than the target recording / erasing light quantity. A second control filter for indicating the drive current value of the laser light source depending on whether the value is small or not, and only offsetting a decrease in the emitted light amount of the laser light source due to the stop of the high frequency modulator during the recording and erasing. Drive current correction circuit for outputting the correction amount of the above, and the correction value of the drive current correction circuit and the instruction value of the second control filter are added to give a drive current to the laser light source to the second drive means. It is configured to include an adder circuit for supplying.

According to the present invention, therefore, the output characteristic of the light amount detecting means and the current-light output characteristic of the laser element, which change depending on the operation or stop of the HF modulator, are corrected by correcting the detected light amount and the laser drive current. It is possible to correct the change of the light quantity and to switch between the reproducing light quantity and the recording / erasing light quantity at a high speed, and to omit the gain switching circuit according to the recording / erasing light quantity in the servo signal reproducing amplifier that handles high frequencies. It has the effect of being able to.

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

Further, 103 is a holding circuit for holding the light amount value detected by the light amount detector 102, 104 is a laser depending on whether the current light amount value held by the holding circuit 103 is larger or smaller than the target value. The control filter outputs an instruction to increase / decrease the laser drive current of the element 101 to the drive circuit 105.

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

Further, 113 is an addition circuit for adding the light amount value detected by the light amount detector 102 and the correction amount output from the light amount correction circuit 111, and the light amount correction circuit 11 causes the HF modulator 110 to operate during recording and erasure. The correction amount enough to cancel the offset amount of the detected light amount caused by the stop is output to the addition circuit 113.

Reference numeral 106 denotes a holding circuit that holds the light amount value output from the adding circuit 113, and 107 indicates whether the current light amount value held by the holding circuit 106 is larger or smaller than the target recording / erasing light amount. The control filter outputs an instruction to increase / decrease the drive current of the laser element 101 to the adder circuit 114.

The adder circuit 114 is for adding the output of the control filter 107 and the output of the drive current correction circuit, and the drive current correction circuit 112 is a laser output of the laser element 101 generated when the HF modulator 110 is stopped. It outputs a correction amount enough to offset the decrease.

Reference numeral 108 denotes a drive circuit which inputs the output of the addition circuit 114 and drives the laser element 101 during light quantity control during recording and erasing.
This is a test light emitting circuit that operates in the laser light amount correction area of the recording medium during reproduction light amount control. By operating this test light emitting circuit 109, the drive circuit 108 replaces the drive of the HF modulator 110 with the laser element 101. A current equivalent to the amount of recording / erasing light is supplied.

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

In FIG. 1, the operation is broadly divided into two types, (a) reproduction light amount control and (b) recording / erasing light amount control. The following two items (a) and (b) will be described below.

(B) Reproduction light intensity control In order to improve the S / N ratio of the magneto-optical signal to be reproduced, the HF modulator 1
Operate 10 Next, the recording medium is rotated, and the light amount detector 102 receives the light emitted from the laser element 101 in the servo bite area of the recording medium, and the detection output thereof is held by the holding circuit 103.
Then, the holding circuit 103 holds the current light amount value.

The control filter 104 reduces the drive current of the laser element 101 when the current light amount value held in the holding circuit 103 is larger than the target reproduction light amount, and conversely, when the light amount value is small, the laser element 101 The drive circuit 105 is instructed to increase the drive current.

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.

By such feedback control, laser device
It operates so that the light quantity of 101 becomes equal to the current reproduction light quantity.

(B) Recording / erasing light amount control Since it is not necessary to reproduce the magneto-optical signal during recording / erasing, in order to prevent the laser element 101 from being damaged by the peak current of the HF modulator, Stop the operation.

In the state where the recording medium is rotated and the generated light amount control of the above item (a) is working, the test light emitting circuit 109 operates in the laser light amount correction area of the recording medium, and the output thereof causes the laser beam to pass through the driving circuit 108 and the driving circuit 108. A current corresponding to an approximately recording / erasing light amount is passed through the element 101.

In response to this current, the light amount detector 102 receives the light emitted from the laser element 101 and outputs the detection output to the addition circuit 113.

On the other hand, the light amount correction circuit 111 outputs a correction to the output of the light amount detector 102 to offset the offset amount of the detected light amount caused by the stop of the HF modulator 110, and outputs it to the addition circuit 113, and the addition circuit 113. At the light amount detector 102
And the output of the light amount correction circuit 111 are added, the addition result is output to the holding circuit 106, and the holding circuit 106 holds the corrected light amount value.

The control filter 107, when the current light amount value held in the holding circuit 106 is larger than the recording / erasing light amount, the laser element.
The addition circuit 104 is instructed to decrease the driving current of the laser element 101, and vice versa.

The drive current correction circuit 112 outputs to the adder circuit 114 in order to add a correction for canceling the reduction in the laser output caused by stopping the HF modulator 110.

As a result, the adder 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 sends a current after correction to the laser element 101 based on the addition result of the addition circuit 114. As a result, a total of the current by the reproduction light amount control, the current by the recording / erasing control and the correction current for stopping the HF modulator 110 flows in the laser element 101.

By such feedback control, laser device
The light amount of 101 is set to be equal to the target recording / erasing light amount.

As described above, according to the above-described embodiment, this is caused by stopping the HF modulator 110 at the time of recording / erasing. Since both the offset of the detected light amount and the decrease of the laser output are canceled by the light amount correction circuit 111 and the drive current correction circuit 112, respectively,
Not only the reproducing light amount but also the recording / erasing amount can be made to follow the correct target value.

In addition, according to the above-described embodiment, since the above correction is added at the same time when the light amount is switched, there is an advantage that the laser output can be quickly raised to the target light amount.

As described above, according to the present invention, the light amount detection means for detecting the light amount of the laser light source, the first holding means for holding the first light amount value detected by the light amount detection means, and the reproduction light amount control , When the current light quantity value held by the first holding means is larger than the target reproduction light quantity,
Outputs an instruction to reduce the drive current of the laser light source,
Further, when the current light quantity value held by the first holding means is smaller than the target reproduction light quantity, a first control filter which outputs an instruction to increase the drive current of the laser light source, and the first control filter First driving means for driving the high frequency modulator in order to supply a driving current to the laser light source with the driving current based on the instruction of the control filter, and second driving for supplying the driving current to the laser light source during recording / erasing light amount control A test light-emitting circuit for causing the recording / erasing light quantity control means to operate in a laser light quantity correction area of a recording medium and to cause a current corresponding to the recording / erasing light quantity to flow into the laser light source to the second drive means. A light amount correction circuit that outputs a correction amount that cancels out an offset amount of the light amount detection amount of the light amount detection means when the high frequency modulator is stopped during the recording and erasing; The detected value of the light emission amount of the laser light source detected by said light quantity detecting means during the operation of the bets emission circuit,
Second holding means for holding a light quantity value obtained by adding the detected value of the emitted light quantity of the laser light source and the correction quantity, and the light quantity value held by the second holding means is larger than the target recording / erasing light quantity. A second control filter for indicating the drive current value of the laser light source depending on whether the value is small or not, and only offsetting a decrease in the emitted light amount of the laser light source due to the stop of the high frequency modulator during the recording and erasing. Drive current correction circuit for outputting the correction amount of the above, and the correction value of the drive current correction circuit and the instruction value of the second control filter are added to give a drive current to the laser light source to the second drive means. It is configured to include an adder circuit for supplying.

Therefore, by correcting the detected light quantity and the laser drive current, the output time characteristics of the light quantity detecting means and the change in the current-light output characteristics of the laser element, which change due to the operation and stop of the HF modulator, are corrected. It is possible to switch between the reproducing light quantity and the recording / erasing light quantity at high speed, and to the servo signal reproducing amplifier that handles high frequency,
The gain switching circuit according to the recording / erasing light amount can be omitted.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a laser light amount control device in one embodiment of the present invention, FIG. 2 and FIG.
It is a block diagram which shows the schematic structure of the conventional laser light amount control apparatus, respectively. 101 …… Laser element, 102 …… Light intensity detector, 103,106 ……
Holding circuit, 104, 107 ... Control filter, 105, 108 ... Driving circuit, 109 ... Test emission circuit, 110 ... HF modulator, 11
1 ... Light intensity correction circuit, 112 ... Drive current correction circuit, 113 ...
… Addition circuit.

Claims (1)

(57) [Claims] 1. A light quantity detecting means for detecting a light quantity of a laser light source, a first holding means for holding a first light quantity value detected by the light quantity detecting means, and the first holding means during reproduction light quantity control. When the current light quantity value held by is larger than the target reproduction light quantity, an instruction to decrease the drive current of the laser light source is output, and the current light quantity value held by the first holding means is the target. Is smaller than the reproduction light amount of, the first control filter outputs an instruction to increase the drive current of the laser light source, and the drive current is supplied to the laser light source with the drive current based on the instruction of the first control filter. First driving means for driving the high frequency modulator, second driving means for supplying a driving current to the laser light source at the time of controlling the recording / erasing light quantity, and laser for the recording medium to the recording / erasing light quantity control means. A test light emitting circuit which operates in the amount correction region and causes a current corresponding to the recording / erasing light amount to flow into the laser light source to the second driving means; and the stoppage of the high frequency modulator during the recording / erasing. A light amount correction circuit that outputs a correction amount that offsets the offset amount of the light amount detection amount of the light amount detection means, and a detected value of the emitted light amount of the laser light source detected by the light amount detection means during operation of the test light emitting circuit, Second holding means for holding a light quantity value obtained by adding the detected value of the emitted light quantity of the laser light source and the correction quantity, and the light quantity value held by the second holding means is larger than the target recording / erasing light quantity. A second control filter for instructing the drive current value of the laser light source depending on whether it is small or small, and the light emitted from the laser light source when the high frequency modulator is stopped during the recording / erasing Of the driving current correction circuit that outputs a correction amount that cancels out the decrease amount of the above, and the correction value of the driving current correction circuit and the instruction value of the second control filter are added to the second driving means. A laser light amount control device comprising: an adder circuit for supplying a drive current to the laser light source.