JPH083905B2 - Laser diode automatic output control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A. Industrial field of use B. Outline of invention C. Prior art D. Problems to be solved by the invention E. Means for solving the problems (Fig. 1) F. Action G. Example ( G-1) Disk format (Figs. 2 to 5) (G-2) Magneto-optical disk device (Fig. 6) (G-3) Laser drive circuit and APC circuit system (Figs. 7 and 8) H. Effects of the Invention A. Field of Industrial Application The present invention relates to an automatic output control circuit of a laser diode for holding the output of the laser diode at a predetermined value.

B. SUMMARY OF THE INVENTION The present invention relates to a laser diode automatic output control circuit for holding an output of a laser diode at a predetermined value, wherein a current source means for supplying a driving current to the laser diode is provided in a non-driving period of the laser diode. By turning the switch off, the useless power consumption can be suppressed and the problem of heat generation of the element can be eliminated.

C. Conventional Technology A magneto-optical disk has been known as a large-capacity recording medium capable of rewriting data.

As a structure of a laser drive circuit in a magneto-optical disk device for recording / reproducing data on / from the magneto-optical disk, for example, a laser diode is provided at one collector of a transistor pair commonly connected to transistors for respective emitter current sources. Has been connected, and a resistor has been connected to the other collector. This is because the signal for recording has a pulse shape and high-speed switching operation is required.

D. Problems to be Solved by the Invention By the way, in the laser drive circuit configured as described above,
During the period other than the driving period of the laser diode, that is, the non-driving period, all the current from the transistor for the current source flows through the resistor.

At this time, even if the current value of the transistor for the current source is 100 mA and the power supply voltage is 5 V, power of about 500 mW is constantly consumed, which is a waste of power. Further, there is a problem of heat generation by the element.

Therefore, the present invention has been proposed in view of the above-mentioned conventional problems, and in the non-driving period of the laser diode, wasteful power consumption is suppressed, and the problem of heat generation by the element can be eliminated. An object is to provide an automatic output control circuit for a laser diode.

E. Means for Solving Problems A laser diode automatic output control circuit according to the present invention, in order to solve the above problems, a laser diode and a current source means for supplying a drive current to the laser diode. A light receiving element for detecting the intensity of the laser beam output from the laser diode, and a switch means for selectively supplying a control signal or a predetermined voltage based on the detection output of the light receiving element to the current source means. In the driving period of the laser diode, a control signal based on the output detected by the light receiving element is supplied to the current source means through the switch means, and the output of the laser diode is held at a predetermined value. Together with the non-driving period of the laser diode, the predetermined voltage is supplied to the current source means via the switch means, It is characterized in that the current source means to the OFF state.

In FIG. 1 showing a basic configuration example of an automatic output control circuit for a laser diode according to the present invention, a laser diode 101 is connected to a collector of a transistor Q ₁₀₁ , and a resistor R ₁₀₁ is connected to a collector of a transistor Q _102. Has been done. The emitters of the transistors Q ₁₀₁ and Q ₁₀₂ are commonly connected to the collector of a transistor Q ₁₀₃ which is a current source means, and the emitter of the transistor Q ₁₀₃ has a resistor R
It is connected via ₁₀₂ to a terminal 102 which provides a voltage V _EE . The base of the transistor Q ₁₀₃ is connected to the switch 108 described later. The above transistor
Regarding Q ₁₀₁ and Q ₁₀₂ , for example, one base is supplied with a data pulse corresponding to write data, and the other base is supplied with a pulse having a phase opposite to that of the data pulse or a predetermined voltage V _BB . That is, the above transistor
When one of the transistors Q ₁₀₁ and Q ₁₀₂ is on, the other transistor is off and either the laser diode 101 or the resistor R ₁₀₁ is selectively connected to the transistor Q _103. It is like this.

The photodiode 103 as a light receiving element for detecting the intensity of the laser light output from the laser diode 101 is connected to the resistor R _103, and also connected to the switching element 105 via the operational amplifier 104 for DC amplification. Has been done. The switching element 105 is a capacitor C
It is connected to ₁₀₁ and an operational amplifier 106 serving as a high input impedance buffer. The switching element 105
Is supplied with a sample pulse SP ₀ of a predetermined cycle,
A sample and hold operation is performed in which the output of the photodiode 103 supplied via the operational amplifier 104 is sampled and held in the capacitor C ₁₀₁ . The output terminal of the operational amplifier 106 is connected to the inverting input terminal of the operational amplifier 107 via the resistor _R104 . This operational amplifier 1
The reference voltage V _REF is applied to the non-inverting input terminal of 07,
The output terminal is connected to the switch 108 which is a switch means. The switch 108 is also connected to a terminal 109 which provides a predetermined voltage, here a voltage V _EE equal to the voltage applied to the terminal 102. Further, the switch 108 is connected to the terminal 110 to which the switch pulse P _SW is supplied. The switch pulse P _SW is, for example, a pulse that becomes a high (H) level during the driving period of the laser diode 101, and the switch pulse P _SW causes the switch 1 to _operate.
08 switching control is performed, and the laser diode 101
The output from the operational amplifier 107 is supplied to the transistor Q ₁₀₃ during the driving period of, and the voltage V
_EE is supplied to the transistor Q ₁₀₃ .

That is, during the driving period of the laser diode 101, a control signal based on the detection output from the photodiode 103 from the operational amplifier 107 is supplied to the base of the transistor Q ₁₀₃ , and the output (light emission intensity) of the laser diode 101 is set to a predetermined value. Control retained (APC: Automatic Power Control)
Is done. Also, during the non-driving period of the laser diode 101 in which the transistor Q ₁₀₂ is turned on, the voltage of the terminal 109 is
V _EE is supplied to the base of the transistor Q ₁₀₃ , and the base and the emitter become approximately the same potential, so that the transistor Q ₁₀₃ is turned off and no current flows through the resistor R ₁₀₁ . Therefore, useless power consumption can be suppressed, and the problem of heat generation by the element can be eliminated.

In the non-driving period of the laser diode 101, A
Information for the PC is stored in capacitor C ₁₀₁ , AP
It does not hinder the operation of C. Further, in order to prevent the current from flowing through the resistor R ₁₀₁ , it is conceivable that the ground side of the resistor R ₁₀₁ is disconnected, but this is not preferable because the collector potential of the transistor Q ₁₀₂ floats. .

F. Action According to the present invention, during the non-driving period of the laser diode, a predetermined voltage is supplied to the current source means and the current source means is turned off.

G. Example Hereinafter, one example of an automatic output control circuit for a laser diode according to the present invention will be described in detail with reference to the drawings. In this embodiment, the present invention is applied to a magneto-optical disk device. Therefore, first, the format of the magneto-optical disk in this embodiment will be described.

G-1. Disc Format FIG. 2 schematically shows the recording pattern of the magneto-optical disc in this embodiment.

In FIG. 2, the magneto-optical disk 1 has a diameter of, for example, about 13 cm, and has a storage capacity of 300 Mbytes or more on one side. The disc 1 is rotated at a constant angular velocity, and data is recorded by forming concentric tracks 2 as one track per one rotation. The number of tracks on one side is about 18000 to 20000, and each track is divided into, for example, 32 sectors.

Further, as shown in an enlarged view in FIG. 3, each of the above-mentioned tracks is composed of a pit area 2a having servo pits and a data area 2b in which data is written, and these are alternately arranged along the circumferential direction. It is provided. Above pit area
When the lengths of 2a and data area 2b are converted into bytes, for example, the pit area 2a is 2 bytes and the data area 2b is 16 bytes.

As shown in FIG. 4, three pits P _A , P _B , and P _C are formed in each of the pit areas 2a. pit
P _A and P _B are formed with a vertical shift with the center line of the track formed on the disk 1 sandwiched therebetween, and also pits
P _C is formed on the center line. Each of these pits
The diameters of P _A , P _B and P _C are about 0.5 to 1.0 μm, and the actual length L of the pit area is about 15 to 30 μm.

FIG. 5 shows the arrangement of the pits P _A , P _B , and P _C in the radial direction of the disc 1 (the direction of the arrow in FIG. 2). That is, each of the pits P _B and P _C is linearly arranged, and every 16 pits P _A are arranged back and forth in the longitudinal direction of the track. The array of the pits P _A whose positions are shifted by every 16 is used to perform a traverse count, which will be described later, in order to obtain the track number of the track currently being scanned by the optical pickup. Also, the pit P above
_A is sampled by the sample pulse SP ₁ or the sample pulse SP ₂ , each pit P _B , P _C is sampled by the sample pulse SP ₃ , SP _5, respectively, and further, the pit P _B and the pit P _C are sampled. The mirror surface area between them is sampled by the sample pulse SP ₄ and used for various servos and clock generation described later.

G-2. Magneto-optical disk device FIG. 6 shows the overall structure of the magneto-optical disk device.

In this embodiment, the input terminal 11 is supplied with data D ₁ to be recorded from a computer or the like via an interface. This data D ₁ is sent to the modulation circuit 12 and subjected to predetermined modulation including bit conversion and the like, and then sent to the laser drive circuit 13. The laser drive circuit 13 is supplied with a control signal for each mode of writing, reading, or erasing from the above interface, and outputs a signal for driving the laser diode 21 of the optical pickup 20 in response to the control signal, and outputs the data. A drive pulse signal having a timing corresponding to a channel clock CCK serving as a reference clock at the time of recording and erasing, and a high frequency drive signal at the time of reading are supplied to the laser diode 21.

The optical pickup 20 includes the laser diode 21.
In addition, it comprises a photodiode 22 and two photodetectors 23 and 24 divided into four. The photodiode 22 detects the intensity of the laser light emitted by the laser diode 21. The photodetectors 23 and 24 detect reflected light of the laser light from the magneto-optical disk 1 via an analyzer, and one of them detects a plus direction component of the Kerr rotation angle,
The other detects the minus direction component of the car rotation angle.

The motor 14 is servo-controlled by, for example, a PLL (Phase Locked Loop) by a motor servo circuit 15, and rotates the disk 1 accurately at a predetermined speed (angular speed).

The laser light output from the laser diode 21 is applied to the magneto-optical disk 1 and is incident on the photodiode 22. The output of the photodiode 22 according to the light intensity of the laser light is supplied to a sample-and-hold (S / H) circuit 17 via a DC amplifier circuit 16. In this S / H circuit 17, the sample pulse SP ₄ (5th
The sample-and-hold operation is performed in response to the output of the laser drive circuit 13 via the APC amplifier circuit 18.
Is supplied as an APC (Automatic Power Control) control signal. Thus, the light intensity of the laser light output from the laser diode 21 is kept at a predetermined value.

Although the present invention is applied to this APC circuit system, its description is omitted here and will be described in detail later with reference to FIGS. 7 and 8.

The optical pickup 20 into which the reflected light of the laser light from the disk 1 is incident via an analyzer (not shown).
Are output to the preamplifier circuit 31, respectively. From the preamplifier circuit 31, a photodetection signal S _A (S _A = A + B + C + D + A ′ +) is a sum signal of the outputs from the respective light receiving regions of the photodetectors 23 and 24.
B '+ C' + D ' ) ( together containing a DC component) are sent directly to the focus servo circuit 32, the light detection signal and an output by the respective light receiving regions S _{B [S B = (AC-BD)} +
(A'C'-B'D ')] is sent to the focus servo circuit 32 through the S / H circuit 33 which performs a sample and hold operation in response to the sample pulse SP ₄ . Then, the focus servo control signal generated by the focus servo circuit 32 based on the signals S _A and S _B is sent to the optical pickup 20 to control the focus.

Further, the light detection signal S _C (S _C =
A + B + C + D + A '+ B' + C '+ D') is sent to the peak value detection circuit 41, S / H circuits 51, 52, 53 and sampling clamp circuit 61, respectively. The light detection signal S _C is a detection signal of a concave / convex pattern in the pit area 2a of the disc 1. The peak value detection circuit 41 detects the peak value of the light detection signal S _C , and the unique pattern detection circuit 42 uniquely gives it only between the pits P _B and P _C on the disc 1. The pit pattern having a space is detected to detect the pit P _C , and the detection output is sent to the pulse generation circuit 44 via the delay circuit 43. Then, in the pulse generation circuit 44, the unique pattern detection circuit 42
Generates a channel clock CCK as a reference clock synchronized with the pit P _C based on the detection output obtained at, and also generates a byte clock BYC and a servo byte clock.
SBC and sample pulses SP ₁ , SP ₂ , SP ₃ , SP ₄ , and SP ₅ are formed and output (see FIG. 5). Although not shown, the channel clock CCK is supplied to all circuit blocks. The sample pulse SP ₁ is supplied to the S / H circuit 51, sample pulse SP ₂ is supplied to the S / H circuit 52, sample pulse SP ₃ is supplied to the S / H circuit 52. The sample pulse SP ₄ is supplied to the S / H circuits 17 and 33 and the sampling clamp circuits 61 and 62. The sample pulse SP ₅ is used, for example, for detecting the moving direction of the optical pickup 20. Further, a gate pulse is supplied from the pulse generation circuit 44 to the peak value detection circuit 41 and the unique pattern detection circuit 42.

In each of the above S / H circuits 51, 52, 53, the light detection signal supplied
For S _C , the sample and hold operation is performed at each of the above sample pulses SP ₁ , SP ₂ , and SP ₃ . The output from the S / H circuit 51 and the output from the S / H circuit 52 are
Compare levels. This comparison output is inverted every 16 tracks in relation to the radial arrangement of the pits P _{A on} the disk 1, and is sent to the tracking servo / seek circuit 55 as a signal for traverse count and to the multiplexer 56. To be This multiplexer
From 56, the higher level signal of the signals from the respective S / H circuits 51, 52 is selectively output and sent to the subtraction circuit 57. The subtraction circuit 57 forms a difference signal between the signal from the multiplexer 56 and the signal from the S / H circuit 53 and sends it to the tracking servo / seek circuit 55 as a tracking error signal. The tracking servo / seek circuit 55 is used for the optical pickup 20.
Tracking control and feed control.

Further, the sampling clamp circuit 61 receives the light detection signal S _C , and the sampling clamp circuit 62 receives the light detection signal S _D [S _D = (A + B + C + D) − (A ′ +
B '+ C' + D ')] are respectively supplied from the preamplifier circuit 31. The light detection signal S _C is
As described above, it is the detection signal of the concavo-convex pattern in the pit area 2a of the disc 1. Further, the light detection signal S _D is
This is a detection signal of the data written in the data area 2b of the disk 1. Each sampling clamp circuit 61,6
In 2, each signal is clamped by the sample pulse SP ₄ and sent to the multiplexer 63. This multiplexer 63 has a switching selection operation of sync detection /
It is controlled by a control signal from the address decoding circuit 64. For example, if the photodetection signal S _C is first sent to the analog / digital (A / D) converter 65 via the sampling clamp circuit 61 and the multiplexer 63 and converted into a digital amount, then it is sent to the demodulation circuit 66. The output from the demodulation circuit 66 is sent to the sync detection / address decoding circuit 64 to detect the sync (synchronization signal) and to decode the address information. Then, according to the address information of the data to be read supplied from the computer or the like through the interface, by switching control of the multiplexer 63 when the address information and the actual address match,
The light detection signal S _D for the data area 2b is the A / D converter 65,
The data D ₀ is sent to the demodulation circuit 66, and the output terminal 67 outputs data D ₀ obtained by performing demodulation processing including bit conversion. This data D ₀ is sent to a computer or the like via the interface. Further, at the time of writing data, a control signal is sent from the sync detection / address decoding circuit 64 to the modulation circuit 12, and the data to be written from the modulation circuit 12 according to the control signal is the laser drive circuit.
It will be sent to 13.

G-3. Laser Driving Circuit and APC Circuit System FIG. 7 shows a specific configuration example of the laser driving circuit 13 and the APC circuit system to which the present invention is applied.

In this configuration example, a control pulse instructing a read operation is supplied to the terminal 71, and a control pulse instructing a write operation or an erase operation is supplied to the terminal 75.

The terminal 71 via the transistor Q ₁ transistor Q ₂
Connected to the base of. This transistor Q ₂ has a collector and an emitter commonly connected to the transistor Q ₃ . The collector of the transistor Q ₃ is connected to the base of the transistor Q ₄ and the resistor R ₁ . The emitter of the transistor Q ₄ is connected to the base of the transistor Q ₃ via the diode 72. Each of the transistors Q _3, Q ₄ and diode 72 constitute a ring oscillator. Also transistor Q ₃ transistor
In Q ₅ , each emitter is commonly connected to the collector of a transistor Q ₆ which is a current source means, and the emitter of the transistor Q ₆ is connected to a power supply terminal 73 via a resistor R ₂ .
Also, the base of the transistor Q ₅ is a predetermined base voltage.
Connected to terminal 74, which provides V _BB .

Further, the terminal 75 is connected to the base of the transistor Q ₈ via the transistor Q ₇ . This transistor Q ₈
The collector of is connected to the laser diode 21 and is also connected to the collector of the transistor Q ₅ . The collector of the transistor Q ₉ is installed via the resistor R ₃ , and the base thereof is connected to the terminal 74. Each of the transistors Q ₈ and Q ₉ has its emitter commonly connected to the collector of a transistor Q ₁₀ which is a current source means, and the emitter of the transistor Q ₁₀ has a resistor R
It is connected to the power supply terminal 73 via ₄ .

A photodiode 22 which is a light receiving element for detecting the intensity of laser light emitted from the laser diode 21.
Is connected to the resistor R ₅ and is also connected to the switching element 77 via the operational amplifier 76 for DC amplification. The switching element 77 is connected to the capacitor C ₁ and an operational amplifier 78 that serves as a high input impedance buffer. The sampling pulse SP ₄ is supplied to the switching element 77, and the output of the photodiode 22 supplied via the operational amplifier 76 is sampled by the sample pulse SP ₄ to the capacitor C ₁ . Performs sample hold operation to hold. The output terminal of the operational amplifier 78 is connected to the operational amplifiers 79 and 80.
It is connected to each inverting input terminal of R via a resistor R ₆ . Each of the operational amplifiers 79 and 80 has a reference voltage V _REF at each non-inverting input terminal.
Is given. The inverting input terminal of the operational amplifier 80 is connected to the terminal 81 via the resistor R ₇ . A control signal for switching and controlling the output of the laser diode 21 in the write operation mode and the erase operation mode is supplied to the terminal 81.

The output terminal of the operational amplifier 79 is connected to the base of the transistor Q ₆ via the switch 82, and the output terminal of the operational amplifier 80 is connected to the transistor Q ₆ via the switch 83.
Connected to the base of Q ₁₀ . In addition, each switch 8
Reference numerals 2,83 are respectively connected to a predetermined voltage, here, a terminal 84 which gives a voltage V _EE equal to the voltage applied to the power supply terminal 73. The switches 82 and 83 are switched and controlled by the switch pulse P _SW supplied to the terminal 85. That is, when the switch pulse P _SW is at a high (H) level, the transistor Q ₆ has an operational amplifier.
The output from 79 is supplied, and the output from the operational amplifier 80 is supplied to the transistor Q ₁₀ . When the switch pulse P _SW is at the low (L) level, the voltage V _{EE at the} terminal 84 is supplied to the transistors Q ₆ and Q ₁₀ , respectively.

 Next, the operation will be described.

When the terminal 71 is at the level, each transistor Q ₁ , Q ₂
Is held in the off state, and the ring oscillator including the transistors Q ₃ and Q ₄ performs high-frequency oscillation operation at, for example, about 700 MHz to 1 GHz. As a result, the laser diode 21 is driven at a high frequency by being supplied with a high frequency current having a peak value of the current i _CSH generated by the current source transistor Q ₆ via the transistor Q ₅ . When the terminal 71 is at the H level, the transistors Q ₁ and Q ₂ are held in the ON state, so that the current i _CSH generated by the transistor Q ₆ flows to the resistor R ₁ via the transistor Q _2. , The laser diode 21
Is stopped, and the oscillation operation of the ring oscillator is stopped.

Driving the laser diode 21 with a high frequency current,
This is performed by supplying a control pulse that becomes L level in the read operation mode to the terminal 71.

When the terminal 75 is at the L level, the transistors Q ₇ and Q ₈ are kept off, and the transistor Q for the current source is maintained.
_The current i _CSS generated by ₁₀ flows through the transistor Q ₉ to the resistor R ₃ and does not flow to the laser diode 21. Also, the above terminals
When 75 is at H level, the transistors Q ₇ and Q ₈ are turned on, and the current i generated by the current source transistor Q _{10 is
The CSS} passes the laser diode 21 through the transistor Q ₈ above.
Flows to In this embodiment, for example, in the write operation mode, by supplying a control pulse corresponding to data to the terminal 75, the laser diode 21
Are pulse-driven corresponding to the above data to write the data.

Further, it will be specifically described with reference to FIG. 8A to 8D show the waveform of the current value i _LD supplied to the laser diode 21, and the current waveform in the write operation mode is shown in FIG. 8A and in the erase operation mode. The current waveform is shown in FIG. 8B, the current waveform in the read operation mode is shown in FIG. 8C, and the current waveform in the standby operation mode is shown in FIG. 8D. Also, switch pulse P _SW in standby mode
Is shown in FIG. 8E.

In the write operation mode, the terminals 71 and 75 are both held at the L level during the period corresponding to the pit area 2a, so that the laser diode 21 is driven by the high frequency current as shown in FIG. 8A. To be done. Further, during the period corresponding to the data area 2b, the terminal 71 is held at the H level and the data pulse corresponding to the write data is supplied to the terminal 75, whereby the laser diode 21
Are pulse-driven to write data. The operation timing of this writing, that is, the timing of the data pulse is a standby operation mode timing that matches the channel clock CCK formed based on the detection output of the pit P _C.

Here, during the period corresponding to the pit area 2a, the laser diode 21 is always driven by the high frequency current and the reading operation is always performed even in various operation modes other than the write operation mode.

In the erase operation mode, during the period corresponding to the data area 2b, the terminal 71 is held at the H level, and the pulse is repeatedly supplied to the terminal 75, so that the laser diode is removed as shown in FIG. 8B. 21 is pulse-driven to perform a data erasing operation. The timing of this erase operation, that is, the timing of the repetitive pulse also coincides with the channel clock CCK.

In the read operation mode, each of the terminals 71, 7 during the period corresponding to the pit area 2a and the data area 2b, that is, the entire period.
By holding both 5 at the L level, as shown in FIG. 8C, the laser diode 21 is driven by a high frequency current to read data.

Further, in the standby operation mode, as shown in FIG. 8D, the terminal 75 is held at the L level during the period corresponding to the data area 2b, the driving of the laser diode 21 is stopped, and the pit area 2a. Read only for.

Here, in any of the above operation modes, during the driving period of the laser diode 21, the terminal 85 is at H level.
It is kept at a level and consists of photodiode 22 etc.
By the operation of the APC circuit system, the bases of the transistor Q ₆ and the transistor Q ₁₀ are APC controlled, and the output (light intensity) of the laser diode 21 is maintained at a predetermined value. In the erase operation mode, a control signal voltage applied to the terminal 81 is applied to the recording operation mode and the erase operation so that a larger drive current than that in the recording operation mode is passed through the laser diode 21 to ensure the erase operation. It is set to a different value depending on the mode.

In the standby operation mode, the switch pulse P _SW as shown in FIG. _8E , that is, the pit area 2a
A pulse which is at the H level during the driving period of the laser diode 21 corresponding to the above and is at the L level during the non-driving period of the laser diode 21 corresponding to the data area 2b is supplied to the terminal 85. Therefore, during the driving period of the laser diode 21, the output of the operational amplifier 79 is supplied to the base of the transistor Q ₆ and APC control is performed, but during the non-driving period, the voltage V _{EE at the} terminal 84 changes each transistor Q ₆ , Q ₁₀ are supplied to the respective bases of the transistors Q ₆ and Q ₁₀ , and the transistors Q ₆ and Q ₁₀ are turned off to prevent current from flowing in the resistors R ₁ and R ₃ . As a result, the power consumption can be suppressed to, for example, about 1/9 of the conventional one, and the problem of heat generation by the element can be eliminated.

If the switches 82 and 83 are controlled to be switched by different pulses, in the standby operation mode,
The transistor Q ₁₀ can be kept in the off state at all times, and power consumption can be further suppressed.

H. Effect of the Invention According to the laser diode automatic output control circuit of the present invention, since the current source means is turned off during the non-driving period of the laser diode, useless power consumption can be suppressed. Moreover, the problem of heat generation by the element can be eliminated.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a basic configuration example of an automatic output control circuit for a laser diode according to the present invention, and FIG. 2 is a schematic diagram showing a recording pattern of a magneto-optical disk according to an embodiment of the present invention. FIG. 3 is a schematic diagram showing the configuration of each track in the above embodiment, FIG. 4 is a schematic diagram showing the configuration of each pit area, and FIG. 5 is also a view along the radial direction of the disc. FIG. 6 is a schematic diagram showing an arrangement state of existing pits, FIG. 6 is a block diagram showing an overall configuration of the magneto-optical disk device, and FIG. 7 is a configuration of a laser drive circuit and an APC circuit system to which the present invention is applied. FIG. 8 is a circuit diagram showing an example, and FIG. 8 is a timing chart for explaining the operation of the circuit shown in FIG. 21,101 …… Laser diode 22,103 …… Photodiode 82,83,108 …… Switch Q ₆ , Q ₁₀ , Q ₁₀₃ … Transistor

Claims (1)

[Claims] 1. A laser diode, current source means for supplying a drive current to the laser diode, a light receiving element for detecting the intensity of laser light output from the laser diode, and a detection output by the light receiving element. Switch means for selectively supplying a control signal or a predetermined voltage to the current source means, and a control signal based on the detection output of the light receiving element during the drive period of the laser diode via the switch means. The current is supplied to the current source means to control the output of the laser diode at a predetermined value, and the predetermined voltage is supplied to the current source means via the switch means during the non-driving period of the laser diode. An automatic output control circuit for a laser diode, characterized in that the current source means is turned off.