JPH10320861A - Semiconductor laser control circuit for magneto-optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent shortening of a life of a semiconductor laser by preventing a pulse driving current from lowering more than necessary and diminishing a current swing amt. during a pulse driving time and to improve a jitter characteristic by simplifying a driving circuit and shortening a rising/falling time. SOLUTION: This semiconductor laser control circuit for a magnetooptical disk device is constituted by utilizing a pulse reproducing method of making pulsewise light emission of the semiconductor laser 3 in such a way that a high frequency with an amplitude IMDD is superimposed by a high frequency superimposing circuit 2 over pulse currents of a setting current IPH of a laser driving current exceeding a light emitting threshold ITH from a semiconductor laser driver part 1 and a setting current IPL which does not exceed the ITH, and a setting current IPL at the time of pulse suspension is set to be IPL>IMDD/2 and IPL<(ITH-IMDD/2), and a lower part of a peak value of the high frequency superimposed setting current IPH is repeatedly lower than the light emitting threshold ITH.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for optically recording / reproducing information from a magneto-optical disk, and more particularly to a semiconductor laser control apparatus for controlling a light beam applied to a magneto-optical disk.

[0002]

2. Description of the Related Art In recent years, in order to further increase the recording capacity of a magneto-optical disk (to increase the density), a new technique called magnetically-induced super-resolution (MSR) has been proposed.
Resolution) has been widely studied.

[0003] There are a plurality of types of magnetic super-resolution techniques. All of them utilize a difference between a high-temperature portion near the center of an irradiated beam light and a low-temperature portion around the same, and an arbitrary region can be used. As a mask area, and the other as a reproduction area,
By transferring only a part of the mark recorded on the recording layer to the reproduction area and reproducing the signal from the part, it is possible to obtain the same effect as the apparent decrease of the beam. For more information on this magnetic super-resolution technology,
It is described in "Next-generation optical disk technology" (supervised by Seiji Yonezawa, Chapter 6 of Trikeps. Published on July 24, 1995).

A method for reproducing a magneto-optical disk using such a magnetic super-resolution technique is disclosed in, for example, JP-A-7-292.
No. 38 and Japanese Patent Application Laid-Open No. Hei 7-161091 show that a laser beam for reproduction is radiated in a pulse shape to make the temperature distribution on the magneto-optical disk steeper and detect smaller marks. Is disclosed.
Hereinafter, this reproducing method is referred to as a pulse reproducing method.

Normally, when a semiconductor laser used for reproducing a magneto-optical disk is driven by a DC current, it oscillates in a single mode as shown in FIG. 5, and laser noise occurs due to mode hopping. In order to prevent this, in general, in a magneto-optical disk drive, several hundreds
A high frequency current of MHz is superimposed (high frequency superposition), and the semiconductor laser is turned on / off at high speed, so that the semiconductor laser is oscillated in a multi-mode as shown in FIG. This high-frequency superposition is described in detail in, for example, JP-A-56-37834, and the description thereof is omitted here.

[0006]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open Publication No. 7-2
As described in Japanese Patent Application Laid-Open No. 9238, even when a semiconductor laser is irradiated with a pulsed laser beam and pulse reproduction is performed from the laser beam, high-frequency superposition is required to reduce laser noise. It is necessary to do together.

However, when a pulse is emitted with high-frequency superposition performed, the semiconductor laser is actually activated even during the pulse pause because the high-frequency superposition current is added depending on the drive current level during the pulse pause. There is a possibility that the light is emitted and the original effect of the pulse reproducing method cannot be obtained.

To avoid this, the drive current during the pause of the pulse may be set low so that the semiconductor laser does not emit light erroneously. However, if the drive current is set low, the amplitude of the high-frequency superimposed current deviates most to the negative side. In such a case, the current value may become “zero” or less, which causes a reverse voltage to be applied to the semiconductor laser. As a result, the semiconductor laser may be damaged and its life may be shortened.

Further, the drive current at the time of pulse emission of the semiconductor laser needs to obtain a predetermined read power value or more.
It cannot be lower than that value. Therefore, if the setting of the drive current during the pause of the pulse is too small, the current swing amount of the pulse drive increases, and the load on the drive circuit increases. When designing and manufacturing a drive circuit corresponding to the increase,
This may lead to an increase in cost, and further, an increase in rise / fall time may increase jitter.

In the case of using the pulse reproducing method as described above, unless the drive current of the semiconductor laser is carefully set,
There are problems that the original characteristics of the pulse reproducing method cannot be obtained, the life of the semiconductor laser is shortened, and further, the reliability is reduced due to an increase in jitter and the cost of the drive circuit is increased.

Therefore, the present invention provides a semiconductor laser having a maximum amplitude of a high frequency superimposed current which is equal to or less than a light emission threshold of a semiconductor laser during a pulse rest period, does not emit light during a pulse rest period, and does not apply a reverse voltage. Magneto-optical system with improved jitter characteristics by simplifying the drive circuit and shortening the rise / fall time by preventing the current from being reduced, reducing the pulse drive current more than necessary, reducing the amount of current swing during pulse drive An object of the present invention is to provide a semiconductor laser control circuit of a disk device.

[0012]

In order to achieve the above object, the present invention has a reproducing layer and a recording layer, and utilizes a temperature distribution generated by a laser beam irradiated from a semiconductor laser to form the recording layer. A magnetic super-resolution type magneto-optical disk that partially transfers a mark recorded as information to the reproducing layer and reproduces an information signal from the reflected light of the laser light from the reproducing layer, In the semiconductor laser control circuit of the magneto-optical disk drive for reproducing the data, the drive current of the semiconductor laser is set to a first current arbitrarily set to emit light and a second current smaller than the first current. And a high-frequency superimposing unit configured to superimpose a high-frequency current having a frequency higher than the frequency of the pulse based on the number of pulses emitted by the semiconductor laser. The current value I _PL of the light emitting threshold current I _TH and the semiconductor laser, the amplitude I of the high frequency current
Against _MOD, to provide a semiconductor laser control circuit of the magneto-optical disk apparatus according to _{I PL <I TH -I MOD /} 2.

Further, in the semiconductor laser control circuit of the magneto-optical disk drive, the second current value I _PL is set to be I _PL > I _MOD / 2 with respect to the amplitude I _{MOD of the} high-frequency current. The semiconductor laser control circuit of the magneto-optical disk drive having the above-described configuration is configured such that the drive current of the semiconductor laser becomes equal to or less than the light emission threshold even if the high-frequency superimposed current has the maximum value of the amplitude during the pause of the pulse. During this time, the emission of the semiconductor laser is prevented, and the effect of pulse reproduction can be obtained. Also, even if the high-frequency superimposed current has the minimum value (maximum value on the minus side) during the pause of the pulse, the drive current of the semiconductor laser becomes zero or more, and the reverse voltage is applied to the semiconductor laser during the pause of the pulse. do not do. The pulse drive current does not decrease to a predetermined value or more, the amount of current swing during pulse drive is reduced, the load on the drive circuit is reduced, the rise / fall time is shortened, and the jitter characteristics are improved.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a first embodiment of a semiconductor laser control circuit according to the present invention, and will be described.

The semiconductor laser control circuit is roughly divided into a semiconductor laser driver 1 and a high-frequency superimposing circuit 2.
And a semiconductor laser 3. The driving current of the semiconductor laser 3 is the output current of the semiconductor laser driver 1.
ia and the output current ib of the high frequency superimposing circuit 2. The semiconductor laser driver unit 1 includes a current source 4 for supplying a drive current during a pulse emission period of the semiconductor laser 3 and a current source for setting a drive current during a pulse pause period (non-emission period) of the semiconductor laser 3. 5 and a switch 6 for selectively outputting the output of either the current source 4 or the current source 5. These current sources 4 and 5
Can be set by a controller (CPU or the like) 9 provided inside or outside the apparatus. The set current I _PH of the current source 4 for supplying current during the light emission period of the semiconductor laser 3 is the set current I _PL of the current source 5 during the light emission stop period.
Larger than.

The switch 6 selects which current source outputs the current in accordance with the selection instruction signal LDSW from the pulse source. By switching with the LDSW signal, the drive current of the semiconductor laser 3 can be modulated in a pulse shape, and the output value of the semiconductor laser 3 can also be modulated. It is assumed that the pulse frequency is about 40 to 50 MHz.

The high-frequency superimposing circuit 2 includes an oscillator 7 and A
And a capacitor 8 for C-coupling. Since the DC component of the high frequency superimposed current is cut by the capacitor 8, the current supplied from the high frequency superimposition circuit 2 to the semiconductor laser 3 is modulated in a positive / negative symmetry centering on “zero”.

By superimposing such a current on the current from the semiconductor laser driver 1 to the semiconductor laser 3 to turn on and off the semiconductor laser 3 at high speed, the light emission state is maintained in a multi-mode. Usually, a frequency of about 300 to 500 MHz is selected. However, if the frequency is too low, the time during which the semiconductor laser 3 is continuously turned on becomes long, so that light emission may be in a single mode. Therefore, the lower limit of the frequency is determined based on the individual characteristics of the semiconductor laser to be used within a range that does not cause the single mode.

Here, the amplitude I _MOD of the high-frequency superimposed current shown in FIG. 3 is determined during the light emission period of the semiconductor laser 3 (a state in which the set current I _PH is output from the semiconductor laser driver 1).
However, since it is necessary to temporarily turn off the laser beam, an amplitude (A shown in FIG. 3) at which the driving current is equal to or less than the emission threshold I _TH of the semiconductor laser 3 at the bottom of the superimposed current is required. Becomes The current amplitude I _MOD can be controlled by the controller 9. Also,
The setting of the current amplitude I _MOD and the set currents I _PH and I _PL may be performed, for example, by controlling a D / A converter (not shown) by the controller 9.

FIG. 2 schematically shows the configuration of a magneto-optical disk drive including such a semiconductor laser control circuit. Here, some parts that are not the gist of the present invention, such as a collimator lens, a beam splitter, and a wave plate, are omitted from the drawing.

The semiconductor laser 3 is incorporated in the optical system 10 together with the semiconductor laser driver 1 and the high frequency superimposing circuit 2. Further, the optical system 10 includes a part of the laser light emitted from the semiconductor laser 3 or the magneto-optical disk 15.
A beam splitter 11 for reflecting the reflected beams from the optical disc in opposite directions, a monitoring photodetector (MPD) 18 for monitoring the output power by the reflected laser light, and a reflected beam from the magneto-optical disk 15. A photodetector 17 for detecting a signal is incorporated.

The light emitted from the semiconductor laser 3 and transmitted through the beam splitter 11 is introduced into a movable carriage 13. The carriage 13 includes an objective lens 14 and a reflection mirror 12, and reflects laser light from the semiconductor laser 3 on the reflection mirror 12, and
And is emitted to the magneto-optical disk 15.

In this embodiment, the magneto-optical disk 15
Is a magnetic super-resolution (MSR) type. The magneto-optical disk 15 is rotated at a predetermined rotation speed by a spindle motor 16.

The beam reflected by the magneto-optical disk 15 is reflected again by the reflection mirror 12 and enters the photodetector 17 via the beam splitter 11. A mark formed on the magneto-optical disk 15 is read from an output signal of the photodetector 17, and an information signal is reproduced. The details of the configuration of the optical system, the method of signal reproduction, and the like are assumed to be general methods, and are not directly related to the gist of the present invention.

The operation of the semiconductor laser control circuit will be described with reference to FIG. The semiconductor laser driver output signal output from the semiconductor laser driver 1 shown in FIG. 3A is a pulse current that alternates between the set current I _PH and the set current I _PL . Here, this set current I
_{Since PH} is the drive current during the emission period of the semiconductor laser,
A value necessary to obtain a predetermined read power exceeding the light emission threshold I _TH is selected.

A high frequency superimposed current as shown in FIG. 3B is superimposed on the output signal of the semiconductor laser driver to form a drive current waveform of the semiconductor laser as shown in FIG. Here, the amplitude I _MOD of the high-frequency superimposed current, when superimposed on the drive current, has a minimum value equal to or less than the light emission threshold I _{TH of the} semiconductor laser, as in the case of performing signal reproduction using continuous light in the related art. The amplitude A) shown in FIG. 3C is selected.

Therefore, (I _PH -I _MOD / 2) <I _TH . On the other hand, the set current I _{PL serving as} the laser drive current during the pulse pause period can be freely selected within a range where the semiconductor laser 3 does not emit light. The simplest method is to set the set current I _PL to “zero”. It is.

However, it is very difficult to turn on / off the high frequency superimposing operation at high speed, so that the current (I _PL ) is set to “zero”.
Also during the period, the amplitude operation by the high frequency superimposition is continuously performed, and the driving current of the semiconductor laser 3 becomes intermittently negative. Actually, a reverse current does not flow because the semiconductor laser 3 has a diode characteristic, but a reverse voltage is temporarily applied, which may damage the semiconductor laser.

In such a case, during the emission period of the semiconductor laser, the current must swing from "zero" to the set current I _PH, which causes a problem that the load on the semiconductor laser driver unit 1 increases. .

Therefore, in order to avoid this problem, in the present embodiment, the laser drive current I _PL during the pulse rest period is
(I _PL −I _MOD / 2)> 0, that is, I _PL > I _MOD / 2
Set so that With such a setting, it becomes possible to keep the high-frequency superimposing operation in a continuous state during the read operation, similarly to the conventional signal reproduction using continuous light.

However, if the set current I _PL is set too high, the amount of current swing between the set current I _PL and the set current I _PH becomes smaller, but the drive current of the semiconductor laser (upper side of the high frequency superimposed current) during the pause period of the pulse is reduced. _May exceed the light emission threshold _ITH , and the semiconductor laser 3 may emit light.

As described above, when the semiconductor laser 3 emits light during the pulse rest period, a steep temperature distribution on the magneto-optical disk 15 which is a characteristic at the time of pulse irradiation cannot be obtained.
It approaches the case of conventional continuous light irradiation. Therefore, in this embodiment, the set current I _PL is further increased by (I _PL + I _MOD /
2) <I _TH , that is, I _PL <(I _TH −I _MOD / 2).

As a result, the light emission waveform of the semiconductor laser 3 becomes an LD light emission waveform as shown in FIG. 3D, and the semiconductor laser 3 does not emit light during the pulse rest period, and the original effect of pulse reproduction is reduced. It is possible to obtain.

As described above, according to the present embodiment,
The set current I _PL of the laser drive current at the time of the pause of the pulse is I _PL >
Since I _MOD / 2 and I _PL <(I _TH -I _MOD / 2) are set, no reverse voltage is applied to the semiconductor laser 3 or an unnecessary current swing is required.
In addition, the semiconductor laser 3 does not emit light during the pulse pause period, so that a semiconductor laser control circuit with high reliability and high-speed operation and with suppressed increase in cost can be realized.

Next, a semiconductor laser control circuit according to a second embodiment will be described. In the first embodiment described above, the case of using a fixed read power (drive current I _PH ) has been described. However, in the case of the magneto-optical disk of the magnetic super-resolution type, the mask area is controlled by the temperature distribution on the disk surface. Is formed and the signal is reproduced, so that the reproduction signal waveform greatly changes with the read power. Further, since the response is determined by heat, even if the read power is the same, if the environmental temperature is different, the reproduced signal waveform will be different.

For this reason, the control of the read power of the magneto-optical disk of the magnetic super-resolution type is more important than that of the conventional magneto-optical disk, and the read power is accurately adjusted to the optimum read power with respect to the environmental temperature and the like. There is a need. Further, it is necessary to reset the read power depending on the temperature change during the operation of the disk device and the inner / outer circumference of the disk.

In the present embodiment, a description will be given of a set current I _PL for driving during a pulse pause period when the set current I _PH of a semiconductor laser drive current during a pulse emission period is changed in order to change the read power. The configuration of the semiconductor laser control circuit of the present embodiment may be substantially the same as that of the first embodiment.

FIG. 4 is a diagram showing waveforms for explaining the operation of the second embodiment. This embodiment, in addition to the first embodiment described above, the laser drive current of the pulse emission period, is an example for realizing the increase in read power was varied from I _PH 1 to I _PH 2. In this case, simply setting current of the semiconductor laser unit output from the I _PH 1 Pulling I _PH 2, L
With the amplitude of the D drive current, the minimum value of the current that must be equal to or smaller than the threshold value I _TH exceeds the threshold value I _TH during the pulse emission period, the semiconductor laser 3 maintains the ON state, becomes single mode, and the laser noise is reduced. Occurs.

Therefore, while increasing the difference between the set currents I _PH and I _PL , the amplitude of the high frequency superimposed current is increased from I _MOD 1 to I _MOD 1.
_MOD 2, and the semiconductor laser 3 is reliably turned on / off to maintain the light emitting state in the multi-mode.
The reason for widening this difference is that if the set current I _PL during the pulse pause period remains unchanged, the high-frequency superimposed current I _MOD 2 whose amplitude has increased causes the L I that has not _{exceeded the} threshold I _TH to date.
The upper peak value of the D drive current (current at the time of high-frequency superposition with the set current _IPL ) intermittently exceeds the threshold _ITH , and the semiconductor laser 3 emits light even during the pulse pause period. since put away, along with pulling the set current I _PH 1 to I _PH 2, it is to lower the set current I _PL 2 from I _PL 1.

As described above, when the laser drive current I _PH during the pulse emission period is increased to increase the read power, the amplitude I _MOD of the high frequency superimposed current is increased, and the laser drive current during the pulse pause period is set. By lowering the current _IPL , it is possible to change the power without emitting light during the pulse pause, while maintaining the oscillation state of the semiconductor laser in the multimode. When lowering the read power, conversely, the current amplitude I _MOD is reduced and the difference between the set current I _PH and the set current I _PL is narrowed. That is, the set current I _PH is reduced and the set current I _PL is increased. I just need.

In this embodiment, when the read power is increased or decreased, both the high-frequency superimposed amplitude I _MOD and the set current I _PL are changed together with the change in the set current I _PH. By doing so, it is also possible to increase or decrease the read power.

However, if it is intended to change only the high frequency superimposed amplitude, the variable range of the amplitude for satisfactorily operating with respect to the set current _IPH is limited. Further, if the high-frequency superimposed amplitude is fixed, the variable range of the set current I _PH for satisfactorily operating is limited.

[0043] Therefore, in the case of relatively large changes the read power, together with a change set current I _PH, current amplitude I _MOD is also changed, or set according to change the current amplitude I _MOD current It is desirable to also change I _PH . Also, at the set current I _PL , the set current I _PH
In order to minimize the amount of current swing between them, it is desirable to change them together with them.

In the present embodiment, the high-frequency superimposed current has a sinusoidal shape. However, the current may have a different waveform, for example, a rectangular wave or a triangular wave. Waveform is not particularly limited. Alternatively, a waveform obtained by clipping a part of those waveforms can be used.

However, if a sine-wave or triangular-wave current waveform is superimposed, the peak value of the current becomes high and may exceed the maximum rating of the laser output. It is desirable to take measures such as clipping the peak value to reduce the maximum current value. Similarly, in the case of a rectangular wave, if the duty ratio is increased, the effect of reducing laser noise can be obtained without increasing the maximum current or the current amplitude.

As described above, according to each embodiment,
First, even if the pulse pause period, the drive current of the semiconductor laser is equal to or less than the light emission threshold even if the high-frequency superimposed current has the maximum value of the amplitude, the semiconductor laser does not erroneously emit light during the pulse pause period. The original effect of the pulse reproduction method can be obtained.

Second, during the pause period of the pulse, even if the high-frequency superimposed current has the minimum value (maximum value on the minus side), the drive current of the semiconductor laser is "zero" or more. The reverse voltage is not applied to the semiconductor laser during the period, and the adverse effect of shortening the life of the semiconductor laser is eliminated. Also, since the pulse drive current does not decrease more than necessary, the amount of current swing at the time of pulse drive can be reduced, the load on the drive circuit is reduced, the circuit configuration is simplified, and the jitter characteristics due to the shortened rise / fall time are reduced. Is improved.

Third, since the pulse current value and the high-frequency superimposed current amplitude can be set from an external controller, when the read power is reset when the temperature changes during operation or when the disk moves from the inner circumference to the outer circumference, the read power can be set. Each current value can be easily set to an optimum value.

Fourth, when the read power during signal reproduction is adjusted, if the pulse drive current during the light emission period is increased to increase the power, the laser noise is also increased to increase the high frequency superimposed current amplitude. Can be kept in a reduced state, and by further reducing the drive current during the pulse pause period, it is possible to prevent the increased high frequency superimposed current from exceeding the laser emission threshold during the pulse pause period. Thus, the effect of pulse reproduction can be stably obtained.

Conversely, when the pulse drive current during the light emission period is reduced to reduce the power, the current amplitude of the high frequency superimposition is reduced, and the drive current during the pulse pause period is increased, thereby increasing the high frequency. High-frequency superimposition and the amplitude of the pulse current can be reduced while maintaining the noise reduction effect of superimposition, so that power consumption can be reduced and the amount of noise radiated to the surroundings can be reduced.

Although the above embodiments have been described, the present invention includes the following inventions. (1) A mark having information recorded on the recording layer is partially transferred to the reproduction layer by using a temperature distribution generated by irradiating a laser beam from a semiconductor laser, having a reproduction layer and a recording layer. In a semiconductor laser control circuit of a magneto-optical disc device for reproducing at least information on a magnetic super-resolution type magneto-optical disc for reproducing an information signal from reflected light of the laser light from the reproducing layer, Driver means for modulating the drive current of the semiconductor laser in a pulse-like manner between a first current arbitrarily set to emit light and a second current smaller than the first current; comprising a high frequency superimposing means for superimposing even higher frequency of the high frequency current, and the second current value I _PL, light emission threshold current I _TH of the semiconductor laser, the amplitude I _MOD of the high frequency current, _PL <semiconductor laser control circuit of the magneto-optical disk apparatus characterized in that the I _TH -I _MOD / 2.

Therefore, even if the high-frequency superimposed current has the maximum amplitude during the pause of the pulse, the drive current of the semiconductor laser is equal to or less than the light emission threshold, so that the laser does not emit light during the pause of the pulse. Thus, the original effect of the pulse reproducing method can be obtained. (2) The magneto-optical disk device according to (1), wherein the second current value I _PL is set to be I _PL > I _MOD / 2 with respect to the amplitude I _{MOD of the} high-frequency current. Semiconductor laser control circuit.

Therefore, even if the high-frequency superimposed current has a minimum value (maximum value on the minus side) during the pause period of the pulse, the drive current of the semiconductor laser becomes zero or more. Is not added, and the laser life is not adversely affected. In addition, since the pulse drive current does not decrease more than necessary, the amount of current swing at the time of pulse drive can be reduced, so that the drive circuit can be simplified and the jitter characteristics can be improved by shortening the rise / fall time. (3) having a reproducing layer and a recording layer, and using a temperature distribution generated by irradiation of laser light from a semiconductor laser, partially transferring a mark recorded as information on the recording layer to the reproducing layer; In a semiconductor laser control circuit of a magneto-optical disc device for reproducing at least information on a magnetic super-resolution type magneto-optical disc for reproducing an information signal from reflected light of the laser light from the reproducing layer, A driver for modulating a drive current of the semiconductor laser in a pulse form between a first current and a second current smaller than the first current; and a high-frequency current having a frequency higher than the frequency of the pulse. A high-frequency superimposing means for providing a tatami mat, wherein at least the first current level, the second current level, and the amplitude of the high-frequency current can be set from a controller that controls the operation of the device. The semiconductor laser control circuit of the magneto-optical disk device, characterized in that the cormorants configuration.

(4) When increasing the output of the semiconductor laser, increasing the first current level and the amplitude of the high frequency superimposed current, decreasing the second current, and decreasing the output of the semiconductor laser. 4. The semiconductor laser control circuit according to claim 3, wherein the control is performed such that the first current level and the current amplitude of the high-frequency superposition are reduced and the second current is increased.

Therefore, when the read power at the time of signal reproduction is adjusted, if the pulse drive current during the light emission period is increased to increase the power, the laser noise is increased because the amplitude of the high frequency superimposed current is increased. The reduced state can be maintained, and by further reducing the drive current during the pulse pause period, it is possible to prevent the increased high frequency superimposed current from exceeding the laser emission threshold during the pulse pause period. The effect of reproduction can be stably obtained. Conversely, if the pulse drive current during the light emission period is reduced to reduce the power, the current amplitude of the high frequency superimposition is also reduced, and the drive current during the pulse pause period is increased. It is possible to reduce the power consumption and reduce the amount of noise radiated to the surroundings, while maintaining the reduction effect and reducing the amplitude of the high-frequency superposition and the pulse current.

[0056]

As described above in detail, according to the present invention, during the pulse pause period, the maximum amplitude of the high frequency superimposed current is equal to or less than the light emission threshold of the semiconductor laser, and during the pulse pause period, light emission and application of a reverse voltage are performed. And prevents the shortening of the life of the semiconductor laser, does not reduce the pulse drive current more than necessary, reduces the current swing during pulse drive, simplifies the drive circuit, and reduces the rise / fall time A semiconductor laser control circuit of a magneto-optical disk device with improved jitter characteristics due to the above can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a first embodiment of a semiconductor laser control circuit according to the present invention.

FIG. 2 is a diagram schematically illustrating a configuration of a magneto-optical disk device including a semiconductor laser control circuit according to the first embodiment.

FIG. 3 is a diagram showing waveforms for describing an operation of the semiconductor laser control circuit.

FIG. 4 is a diagram showing waveforms for explaining the operation of the second embodiment of the semiconductor laser control circuit according to the present invention.

FIG. 5 is a diagram showing an example of a single-mode waveform for driving a semiconductor laser.

FIG. 6 is a diagram illustrating an example of a multi-mode waveform for driving a semiconductor laser.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser driver part 2 ... High frequency superposition circuit 3 ... Semiconductor laser 4,5 ... Current source 6 ... Switch 7 ... Oscillator 8 ... Capacitor 9 ... Controller

Claims (3)

[Claims] 1. A recording layer having a reproducing layer and a recording layer, wherein a mark recorded as information on the recording layer is partially formed on the reproducing layer by utilizing a temperature distribution generated by a laser beam irradiated from a semiconductor laser. In a semiconductor laser control circuit of a magneto-optical disk device for reproducing information, a magnetic super-resolution type magneto-optical disk for transferring and transferring an information signal from the reflected light of the laser light from the reproducing layer, Driver means for modulating the drive current of the semiconductor laser in a pulsed manner between a first current arbitrarily set to emit light and a second current smaller than the first current; based on pulsed emission number, anda high frequency superimposing means for superimposing a higher frequency of the high frequency current than the frequency of the pulses, the second current value I _PL, light emission threshold current of the semiconductor laser A semiconductor laser control circuit for a magneto-optical disk drive, wherein I _PL <I _TH −I _MOD / 2 with respect to I _TH and the amplitude I _{MOD of the} high-frequency current. 2. The magneto-optical disk drive according to claim 1, wherein the second current value I _PL is set to be I _PL > I _MOD / 2 with respect to the amplitude I _{MOD of the} high-frequency current. Semiconductor laser control circuit. 3. A recording layer having a reproducing layer and a recording layer, wherein a mark recorded as information on the recording layer is partially formed on the reproducing layer by utilizing a temperature distribution generated by irradiation of laser light from a semiconductor laser. In a semiconductor laser control circuit of a magneto-optical disc device for reproducing at least information on a magnetic super-resolution type magneto-optical disc for transferring and reproducing an information signal from the reflected light of the laser beam from the reproducing layer. A driver for modulating a driving current of the semiconductor laser in a pulse form between a first current and a second current smaller than the first current; and a high frequency having a frequency higher than the frequency of the pulse. A high-frequency superimposing means for superimposing a current, wherein at least the first current level, the second current level, and the amplitude of the high-frequency current are controlled by a controller that controls device operation. A semiconductor laser control circuit for a magneto-optical disk drive, wherein the semiconductor laser control circuit is configured so as to be able to be set by the user.