JPH1049901A - Semiconductor laser driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser driving device capable of effectively solving the problem of unnecessary radiation when a plurality of optical pickups are loaded. SOLUTION: Optical pickups 22 and 23 share a high frequency oscillation circuit 4-1. A high frequency current from the collector C of the transistor Q9 of the high frequency oscillation circuit 4-1 is supplied to an LD driving circuit 9-0. Also, a high frequency current from the emitter E of the transistor Q9 of the high frequency oscillation circuit 4-1 is supplied to the LD driving circuit 9-1. A system controller 10-1 selects the optical pickups 22 and 23 based on enable signals EN-0 and EN-1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser driving device used for an optical disk drive equipped with a plurality of optical systems (optical pickups).

[0002]

2. Description of the Related Art At present, optical discs are widely used as recording media, and video tapes tend to be replaced with optical discs in applications for recording audio-visual (AV) signals. By the way, in image processing, a high transfer rate and a real-time property are required. The main methods for realizing these are (1) rotating the optical disk at high speed, (2) increasing the recording density of the optical disk (shorter wavelength, higher NA), and (3) using a plurality of optical systems. It is possible.

However, the method (1) has a problem that the recording power of the semiconductor laser needs to be increased, and the life is shortened. The method (2) has a problem of a system margin such as skew tolerance. As a result, technically and economically, the method (3) using a plurality of optical systems is practical. As the method (3), a laser diode (LD) array method is also conceivable. However, there are disadvantages such as the life and economy of the LD array and the density in the track pitch direction being not improved.

By the way, as a recording medium of an AV signal,
The direct overwrite type is desirable. As the media of the direct overwrite method, a magnetic field modulated magneto-optical (MO) disk, a light modulated direct overwrite MO, a phase change medium (P
C: Phase Change).

[0005] Here, it is difficult to realize a high transfer rate for the magnetic field modulated magneto-optical disk because the transfer rate is determined by the magnetic field head. There is also a problem that the magnetic field modulation magneto-optical disk can be used only on one side. In addition, the optical modulation direct overwrite MO can realize a high transfer rate, but has a problem that a medium is not yet common and a medium cost is high. In addition, phase change media has recently been commercialized,
Although it is considered to be a promising medium in the future, at present, there is a problem that it is inferior in terms of a high transfer rate and the number of times of repeated recording.

Therefore, if the problem of the transfer rate is solved, the magneto-optical disk is more promising than other direct overwrite media in improving the real-time property. In order to realize such a high transfer rate and pseudo overwrite, there is a magneto-optical disk drive equipped with a plurality of optical pickups as described above. In this magneto-optical disk drive, each optical pickup is provided with a high-frequency superimposing circuit. Such a high frequency superposition circuit generates a high frequency having a predetermined oscillation frequency using an LC oscillator. In such a magneto-optical disk drive, it is important to suppress unnecessary radiation from a plurality of optical pickups.

In this magneto-optical disk drive device, the output of laser light when writing (recording), reading (reproducing), and erasing a magneto-optical disk is different.
By irradiating a weaker laser beam than during recording,
Recorded information is read without destroying the recorded pits. The laser beam applied to the magneto-optical disk needs to be appropriately controlled in laser output in the recording, erasing and reproducing modes. for that reason,
The magneto-optical disk drive device includes a laser light output control circuit that switches the light output of the semiconductor laser for each mode and that inputs three types of reference signals so as to obtain an optimum output in each mode. .

FIG. 4 is a configuration diagram of a conventional laser light output control circuit. As shown in FIG. 4, the laser light output control circuit includes a semiconductor laser diode 1 (hereinafter also referred to as LD1), a light output monitoring photodiode 2 of LD1.
(Hereinafter also referred to as PD2), interlocking mode changeover switches 3a and 3b (reproduction R, recording W, erasure E), high-frequency oscillation circuit 4, current-voltage conversion circuit 5, error amplifier 6, and optical output in each mode are determined. A reference voltage 7, a recording signal generating circuit 8, and a current booster 9. A recording signal generating circuit 8 is connected to an input side of the current booster 9. PD2
The laser diode may be provided separately from the one in the same package as the LD 1 and in the optical path. In particular, in the case of a high-power semiconductor laser (30 mW or more) used for recording on a recordable optical disk, the latter is generally used. The current proportional to the light output obtained by the PD 2 is converted into a voltage by the current-voltage conversion circuit 5 and output to the error amplifier 6.

The error amplifier 6 includes a mode switch 3
The reference voltage switched in b is input, compared with the output voltage of the current-voltage conversion circuit 5, and the current of each mode controlled based on the error voltage output is supplied from the current booster 9 to the LD1, The light output in each mode is kept constant.

In general, when a semiconductor laser is used in an optical system for an optical disk, the optical disk is irradiated with focused light to obtain an information signal and a servo signal from the optical disk. Return. Depending on the amount of light returning to the LD 1 and the optical path length, etc.
Scoop noise and mode hopping noise due to interference between return light and irradiation light are generated, which is a factor that causes C / N deterioration of a reproduced signal. The generation of these noises is remarkable in a high-power semiconductor laser.

In order to reduce mode hopping noise and the like due to return light, a harmonic superposition method is known. In this example, in order to superimpose a high-frequency current on the DC bias current of the LD1, a high-frequency oscillation circuit 4 for generating a high-frequency current is connected to the LD1 via the mode switch 3a and the capacitor C1. Then, a high-frequency current is supplied from the high-frequency oscillation circuit 4 to the LD 1 to reduce noise. The oscillation frequency of the high-frequency oscillation circuit 4 has an optimum value depending on the laser and the optical path length.
Hz.

FIG. 5 shows an improvement characteristic by the high frequency superposition method. IP curve shown in FIG. 5 (supply current-light output)
It is assumed that the above-described laser light output control circuit operates so that the light output becomes the read power P _R (mW). At this time, the laser current is I _R , which is 2 × (I
_R− I _th ) (I _th is a threshold current) or more (FIG. 5
(A)) as is obtained by on / off across the threshold current I _th, when superposing the output of the high-frequency oscillator circuit 4, the light output is obtained as shown in FIG. 5 (b), the resulting The laser is oscillated in multi-mode to prevent scoop noise and mode hopping noise.

The superposition level of the high frequency is, as described above,
It is necessary to amplify the current by (operating current−threshold current) × 2 or more, and it is necessary to turn off the LD1 with the current not more than the threshold current, and the effect of high-frequency superposition varies depending on the duty ratio of the LD1 to off and on.

FIG. 6 shows an example of a light emission waveform at the time of high frequency superposition. In this case, the superposition (oscillation) frequency is 235 MHz.
z, the duty ratio when LD1 is on is about 28
%. Here, two peaks are observed in the light emission waveform due to relaxation oscillation of the LD (2.3 GHz in this case). In FIG. 6, the horizontal axis represents time, and the vertical axis represents light output. The duty ratio when the LD1 is turned on during the high frequency superimposition has an optimum value depending on the LD1 and the optical path length of the optical system, etc., but generally, as shown in FIG. Have been done.

In order to reduce the duty ratio when the LD 1 is turned on, it is necessary to increase the peak level of the high frequency superposition, and in proportion thereto, the unnecessary radiation level due to the high frequency superposition is amplified, which may violate the radio wave regulations. . Optical system is 1
In one case, since the oscillation circuit is one circuit, the frequency of the unnecessary radiation is the fundamental frequency and its harmonic components, but when a plurality of optical systems are mounted, the individual oscillation frequencies are the same. Probability is very small and produces subtle differences. Accordingly, a beat component due to the frequency difference is generated in addition to the fundamental frequency and its harmonic components.

FIG. 7 is a specific circuit configuration diagram of a laser light output control circuit including a harmonic superimposing circuit. In FIG. 7, the transistors Q1, Q2, Q3, Q4, and Q5 form a differential switching laser drive circuit. In this differential switching type laser drive circuit, a current mirror circuit is formed by the transistors Q3 and Q4, and the current from the collector of the transistor Q4 to LD1
Is supplied with a drive current. Among these transistors, the transistors Q1, Q2, Q3 and Q4 form an LD current booster 9, and the transistor Q5 forms an LD current control circuit 13.

The D output from the recording signal generating circuit 8 is supplied to the base of a transistor Q2, and the inverted D (D) output is supplied to the base of a transistor Q1. By the D output and the inverted D output, the transistor Q2 or Q
1 is turned on, and each mode described later is set. When the transistor Q2 is turned on by the D output, the collector current of the transistor Q4 is supplied to LD1, and the APC circuit (A
utomatic Power Control) 14 to voltage DDR described later
V is applied to the base of transistor Q5 to control the collector current of transistor Q4, that is, the current supplied to LD1.

The transistor Q10 has a high frequency oscillation circuit 4
And the transistor Q10
Is connected to a transistor Q9 constituting a buffer. Only during reproduction, the oscillation output of the high-frequency oscillation circuit 4 is supplied to the base of the transistor Q5 via the transistor Q9 and the capacitor C1, whereby the collector current of the transistor Q5 is amplitude-modulated.
As a result, the high-frequency current is superimposed on the collector current of the transistor Q4. Here, a modified Colpitts circuit is configured by the transistor Q10, the capacitors C1 to C3, the coils L1 and L2, and the resistors R1 to R3, and the oscillation frequency f0
Is given by the following equation (1).

F0 = 1 / {2π (L1 × C0) ^1/2 )} (1) In the above equation (1), C0 = C1 // C2 // C3.

The MODON signal applied to the base of the transistor Q10 constituting the high-frequency oscillation circuit 4 becomes high level during reproduction, causing the high-frequency oscillation circuit 4 to oscillate. On the other hand, the MODON signal becomes low level except during reproduction, and the high-frequency oscillation circuit 4 does not oscillate.

When the MODON signal becomes high level and the high-frequency oscillation circuit 4 oscillates, the oscillation output is supplied to the base of the transistor Q5 constituting the LD current control circuit 13 via the buffer transistor Q9 and the capacitor C1. A high-frequency current is superimposed on the collector current of Q4.

The current-voltage conversion circuit 5 for converting a photocurrent proportional to the light output from the PD 2 into a voltage supplies the output voltage to the APC circuit 14. In the APC circuit 14,
In each mode (reproduction R, recording W, erasure E) selected by the switch SW under the control of the system controller 10, the light output is compared with the corresponding reference voltage, and the output voltage is compared with the LD current control circuit 13. Is input to the base of the transistor Q5 as DDRV, the collector current of the transistor Q4 is controlled, and the light output in each mode of the LD1 becomes constant.

The operation of each mode of the laser light output control circuit shown in FIG. 7 will be described below. <LD1 off> When the LD1 is turned off and no light is emitted, the recording signal generation circuit 8 outputs D = L (low level),
= H (high level) is output and DDRV = 0. As a result, the transistor Q1 is turned on,
The transistors Q2, Q3, and Q4 are turned off, the collector current of the transistor Q4 does not flow, and the light output of the LD1 is zero. <Reproduction Mode> In the case of the reproduction mode, D = H and D = L are output from the recording signal generation circuit 8, and DDRV = V
_R , MODON = H, the high-frequency oscillation circuit 4 oscillates, the collector current of the transistor Q4 on which the high-frequency current is superimposed flows through LD1, and a pulse light output is obtained, and the average light output is obtained. It is maintained at P _R. <Recording Mode> D = (H → L → H) and inverted D = (L → H → L) corresponding to the recording signal are output from the recording signal generating circuit 8, and MODON = L and DDRV = V _W In this state, the light output of the LD 1 is a pulse light emission of the peak light output P _W synchronized with the D and inverted D modulation signals. <Erase Mode> From the recording signal generation circuit 8, D = H, D = L, and MODON = L.

[0023]

However, the oscillation frequency of the high frequency generated by the LC oscillator has a variation of about ± 5 to ± 10%, and also varies with a temperature change. Therefore, when a high-frequency oscillation circuit is individually mounted on each of a plurality of optical pickups as in the related art, the high-frequency oscillation frequencies from the LC oscillators of the plurality of high-frequency superposition circuits are different from each other, and the beat component due to the difference is regarded as unnecessary radiation. Occurs. By the way, if the frequency difference is constant, the beat component is also constant. However, if the frequency difference is slightly shifted due to a temperature change, the level of the unnecessary radiation also changes due to the change in the beat component. Further, even if the high-frequency oscillation frequencies from the plurality of LC oscillators are the same, the unnecessary radiation level fluctuates when they have the same phase. Therefore, the conventional optical disk drive has a problem that unnecessary radiation from a plurality of optical pickups cannot be sufficiently suppressed.

An object of the present invention is to provide a semiconductor laser driving device capable of sufficiently suppressing unnecessary radiation generated when a plurality of optical pickups are provided.

[0025]

In order to solve the above-mentioned problems of the prior art and to achieve the above-mentioned object, a semiconductor laser driving device of the present invention detects an optical output from a semiconductor laser and detects the output. What is claimed is: 1. A semiconductor laser drive device used for an optical disk drive device equipped with a plurality of optical pickups controlling an optical output of the semiconductor laser based on a result, wherein the laser is shared by the plurality of optical pickups and drives the semiconductor laser. A high-frequency current generating means for generating a high-frequency current to be superimposed on the current;

In the semiconductor laser driving device of the present invention, a high-frequency current generating means shared by the plurality of optical pickups is provided instead of providing a high-frequency current generating means for each of the plurality of optical pickups. Therefore, as in the case where the high frequency current generating means is provided for each of the plurality of optical pickups, the beat component due to the difference in the oscillation frequency between the plurality of high frequency current generating means and the change in the beat component due to the temperature change. The influence is eliminated, and the unnecessary radiation level can be suppressed.

Further, the semiconductor laser driving device of the present invention comprises:
Preferably, the high-frequency current generating means is used for an optical disk drive device equipped with two optical pickups, and supplies high-frequency currents whose phases are mutually inverted to the two optical pickups.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a laser light output control circuit according to an embodiment of the present invention will be described. This laser light output control circuit is mounted on, for example, an optical disk drive that performs recording, reproduction, and erasure of a magneto-optical disk using a plurality of optical pickups. First Embodiment FIG. 1 is a configuration diagram of a laser light output control circuit 21 of the present embodiment. The laser light output control circuit 21 is used, for example, in an optical disk drive equipped with two optical pickups for performing double-sided reproduction of a magneto-optical disk. As shown in FIG. 1, the laser light output control circuit 21 includes two optical pickups 22 and 23, a high-frequency oscillation circuit 4-1 and a system controller 10-1. That is, in the laser light output control circuit 21, the optical pickup 2
2, 23 share the high-frequency oscillation circuit 4-1.

The system controller 10-1 supplies the optical pickup 22 with a D-0 output, an inverted D-0 output and an enable signal EN-0 according to the recording signal. Further, the system controller 10-1 outputs a D-1 output, an inverted D-1 output, and an enable signal E corresponding to the recording signal.
N-1 is supplied to the optical pickup 23. The collector (C) of the transistor Q9 constituting the high-frequency oscillation circuit 4-1 is connected to the buffer switch BS of the optical pickup 22.
Connected to −0. On the other hand, the emitter (E) of the transistor Q9 constituting the high-frequency oscillation circuit 4-1 is connected to the buffer switch BS-1 of the optical pickup 23. Here, since the phases appearing at the collector (C) and the emitter (E) of the transistor Q9 are inverted,
The high-frequency current supplied to the buffer switch BS-0 and the high-frequency current supplied to the buffer switch BS-1 have inverted phases.

Next, the configuration of the optical pickup 22 will be described in detail with reference to FIGS. The configuration of the optical pickup 23 is basically the same as the configuration of the optical pickup 22. FIG. 2 is a configuration diagram of the optical pickup 22. As shown in FIG. 1 and FIG.
Are the LD drive circuit 9-0 and the laser diode LD-
0, photodiode PD-0, current-voltage conversion circuit 5-
0, an APC circuit 14-0, and a buffer switch BS-0.

As shown in FIG. 2, the LD drive circuit 9-
0 has transistors Q1 to Q5, and the transistors Q1, Q2, Q3, Q4 and Q5 constitute a differential switching type laser drive circuit. In this differential switching type laser drive circuit, a current mirror circuit is formed by the transistors Q3 and Q4, and a drive current is supplied from the collector of the transistor Q4 to LD-0. Among these transistors, transistors Q1, Q2, Q3 and Q4 function as LD current boosters, and transistor Q5 functions as an LD current control circuit.

D- from the system controller 10-1
0 output is supplied to the base of transistor Q2,
The (D bar) -0 output is supplied to the base of the transistor Q1. By the D-0 output and the inverted D-0 output, the transistor Q2 or Q1 is turned on, and each mode described later is set. When the transistor Q2 is turned on by the D-0 output, the collector current of the transistor Q4 is supplied to the LD1, and a voltage DDRV described later is applied from the APC circuit 14-1 to the base of the transistor Q5, and the collector current of the transistor Q4, that is, LD-0
Can be controlled.

Next, the high-frequency oscillation circuit 4-1 shown in FIG. 1 will be described in detail. Note that a modified Colpitts oscillation circuit is used as the high-frequency oscillation circuit 4-1. A transistor Q9 forming a buffer is connected to the output side of the transistor Q10. Only during reproduction, the oscillation output of the high-frequency oscillation circuit 4-1 is supplied to the base of the transistor Q5 via the transistor Q9 and the capacitor C1-0, whereby the collector current of the transistor Q5 is amplitude-modulated. A high-frequency current is superimposed on the collector current of Q4.

The MODON signal applied from the system controller 10-1 to the base of the transistor Q10 is:
At the time of reproduction, the level becomes high, and the high-frequency oscillation circuit 4-1 oscillates. On the other hand, the MODON signal is
It becomes low level, and the high-frequency oscillation circuit 4-1 does not oscillate.

When the MODON signal goes high and the high-frequency oscillation circuit 4-1 oscillates, the buffer switches BS-0 and BS-1 are controlled by enable signals EN-0 and EN-1 from the system controller 10-1. In response to the APC circuit 14 via the buffer switches BS-0 and BS-1 of the optical pickups 22 and 23.
−0, 14-1. At this time, the enable signals EN-0 and EN-1 cause the APC circuit 14
When a high-frequency current is superimposed on both outputs of −0 and 14-1, the phase of the high-frequency current superimposed on the output of the APC circuit 14-0 and the high-frequency current superimposed on the output of the APC circuit 14-1 are different. Has been reversed.

The current-voltage conversion circuit 5 converts a photocurrent proportional to the optical output from the PD-0 into a voltage, and supplies the output voltage to the APC circuit 14-0. In the APC circuit 14-0, in each mode (playback R, record W, erase E) selected under the control of the system controller 10,
The light output is compared with a corresponding reference voltage, and the output voltage is input as DDRV to the base of the transistor Q5 of the LD drive circuit 9-0, the collector current of the transistor Q4 is controlled, and the light output of each mode of the LD1 is controlled. Becomes constant.

The operation of the laser light output control circuit 21 is based on an enable signal EN- from the system controller 10-1.
This is the same as the conventional laser light output control circuit described with reference to FIG. 7 except that the optical pickups 22 and 23 are selectively operated by 0 and EN-1.

As described above, in the laser light output control circuit 21, instead of providing a high-frequency oscillation circuit for each of the optical pickups 22 and 23, a high-frequency oscillation circuit 4-
1 was shared. Therefore, the optical pickup 2
As in the case where a high-frequency oscillation circuit is provided in each of the two high-frequency oscillation circuits, the effect of the change in the beat component due to the difference between the oscillation frequencies of the two high-frequency oscillation circuits and the change in the beat component due to the temperature change is eliminated, and the unnecessary radiation level is suppressed. Can be. In the laser light output control circuit 21, the phase of the high-frequency current superimposed on the output of the APC circuit 14-0 of the optical pickup 22 and the APC circuit 14
Since the phase of the high-frequency current superimposed on the output of −1 is in a reverse phase relationship, when both the optical pickups 22 and 23 are in the reproduction mode, the influence between the respective fundamental frequency components is different. Is canceled, and it is possible to prevent the fundamental frequency components from interacting with each other to increase the unnecessary radiation level.

Second Embodiment FIG. 3 is a configuration diagram of a laser light output control circuit 31 of the present embodiment. As shown in FIG. 3, the laser light output control circuit 3
1 denotes (n + 1) optical pickups 22-0 to 22-
n, a high-frequency oscillation circuit 4-2 and a system controller 10-2. Here, n is an arbitrary integer value.

The structure of the optical pickups 22-0 to 22-n is the same as that of the optical pickup 22 shown in FIGS. The configurations of the high-frequency oscillation circuit 4-2 and the system controller 10-2 are the same as those of the high-frequency oscillation circuit 4 shown in FIG.
-1 and the same as the system controller 10-1.

However, the emitter terminal of the transistor Q9 of the high-frequency oscillation circuit 4-2 is connected to the buffer switches BS-0 to BS-0.
It is connected to the base of transistor Q5 via BS-n and capacitors C1-0 to C1-n. The buffer switches BS-0 to BS-n are connected to enable signals EN-0 to EN-0 from the system controller 10-2.
It is turned on / off by EN-n, and when turned on, the emitter terminal of the transistor Q9 and the capacitor C
1-0 to C1-n are connected.

As described above, in the laser light output control circuit 31, the high frequency oscillation circuit 4-2 is shared instead of providing the high frequency oscillation circuit in each of the optical pickups 22-0 to 22-n. . Therefore, as in the case where a high-frequency oscillation circuit is provided in each of the optical pickups 22-0 to 22-n, the influence of the change in the beat component due to the difference between the oscillation frequencies of the two high-frequency oscillation circuits and the change in the beat component due to the temperature change is eliminated. In addition, the unnecessary radiation level can be suppressed.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the case where the Colpitts oscillation circuit is used as the high-frequency oscillation circuit has been described.
Alternatively, a Hartley oscillation circuit may be used as the oscillation circuit.

[0044]

As described above, according to the semiconductor laser driving apparatus of the present invention, the high-frequency current generating means is shared by each of the plurality of optical pickups, instead of providing the high-frequency current generating means. Therefore, as in the case where the high-frequency current generating means is provided in each of the plurality of optical pickups, the influence of the change in the beat component due to the difference between the oscillation frequencies of the two high-frequency current generating means and the change in the beat component due to the temperature change disappears, and unnecessary radiation is eliminated. The level can be suppressed. Further, according to the semiconductor laser driving device of the present invention, high-frequency currents whose phases are mutually inverted are supplied to the two optical pickups, respectively. Therefore, when both of the two optical pickups are in the reproduction mode. In addition, it is possible to prevent the mutual influence of the respective fundamental frequency components from being cancelled, thereby preventing the fundamental frequency components from mutually affecting each other and increasing the unnecessary radiation level.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a laser light output control circuit according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of the optical pickup shown in FIG. 1;

FIG. 3 is a configuration diagram of a laser light output control circuit according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional laser light output control circuit.

FIG. 5 shows an improvement characteristic by the high frequency superposition method.

FIG. 6 is an example of a light emission waveform at the time of high frequency superposition.

FIG. 7 is a specific circuit configuration diagram of a conventional laser light output control circuit including a harmonic superimposing circuit.

[Explanation of symbols]

LD-0 to LD-n laser diode, PD-0 to P
Dn: photodiode, BS-0 to BS-n: buffer switch, 5-0 to 5-n: current-voltage conversion circuit, 9
−0 to 9-n: LD drive circuit, 10-1: System controller, 14-0 to 14-n: APC circuit, 21
... Laser light output control circuit, 22, 23 ... Optical pickup

Claims (4)

[Claims] 1. A semiconductor laser drive device used in an optical disk drive device equipped with a plurality of optical pickups for detecting optical output from a semiconductor laser and controlling the optical output of the semiconductor laser based on the detection result, A semiconductor laser driving device which is shared by a plurality of optical pickups and has a high-frequency current generating means for generating a high-frequency current to be superimposed on a laser current for driving the semiconductor laser. 2. The optical disk drive device having two optical pickups mounted thereon, wherein the high-frequency current generating means supplies high-frequency currents whose phases are mutually inverted to the two optical pickups, respectively. 14. The semiconductor laser driving device according to claim 1. 3. The optical pickup according to claim 2, wherein said high-frequency current generating means includes an oscillation circuit, and supplies an emitter output and a collector output of a transistor provided at an output terminal of said oscillation circuit to said two optical pickups. 14. The semiconductor laser driving device according to claim 1. 4. The semiconductor laser driving device according to claim 1, wherein said high-frequency current generating means has a Colpitts oscillation circuit.