JP2001266388A - Laser driving device, optical head device and optical information processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser driving device for realizing an optical head device and an optical information processor which are inexpensive and reliable while using plural light sources in order to obtain a light source of multi-wavelengths required for dealing with different kinds of optical disks such as CD, CD-R, DVD in recording and reproducing the optical disks. SOLUTION: With respect to 2 wavelengths LD consisting of the first semiconductor laser 1a, the second semiconductor laser 1b and a photodiode 2, the optical outputs of the lasers 1a and 1b are controlled by APC circuits 6a and 6b based on the voltage values of respective variable resistors 4a and 4b. Electronic switches 7a and 7b for selecting effective one from among the resistors 4a and 4b are arranged on an optical head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical information processing apparatus for recording / reproducing or erasing information on an optical medium or a magneto-optical medium such as an optical disk or an optical card. The present invention relates to an optical head device that emits a laser beam and a laser driving device used in the optical head device.

[0002]

2. Description of the Related Art Optical memory technology using an optical disk having a pit pattern as a high-density and large-capacity storage medium includes digital audio disks, video disks,
Applications such as document file disks and data files are expanding. In this optical memory technology, information is recorded / reproduced on an optical disk with high precision and reliability via a light beam which is narrowed down. This recording / reproducing operation depends solely on the optical system.

The basic functions of the optical head device, which is the main part of the optical system, are roughly classified into convergence for forming a diffraction-limited small spot, focus control and tracking control of the optical system, and detection of a pit signal. You. These functions are realized by a combination of various optical systems and photoelectric conversion detection methods according to the purpose and use.

On the other hand, in recent years, high-density, large-capacity optical disks called DVDs have been put into practical use, and have been spotlighted as information media capable of handling a large amount of information such as moving images. This DVD
The optical disc has a smaller pit size on the information recording surface in order to increase the recording density as compared with a conventional compact disc (hereinafter abbreviated as CD). Therefore, in an optical head device for recording / reproducing a DVD optical disk, a wavelength of a light source for determining a spot diameter,
Numerical Apert of the convergent lens
ure: abbreviated as NA) is different from the case of CD.

Incidentally, in the case of CD, the wavelength of the light source is approximately 0.7.
8 μm and NA are approximately 0.45, whereas the wavelength of the light source is approximately 0.63 to 0.68 μm and N
A is approximately 0.6. Therefore, when two types of optical disks, CD and DVD, are recorded and reproduced by one optical information processing device, an optical head device having two optical systems is required. Particularly in recent years, C which has been frequently used is
A write-once CD-R, which is a derivative of D, has a reflective film on the disk that is optimized for a wavelength of 0.78 μm, and cannot be reproduced at the wavelength for DVD. In addition, in an optical information processing apparatus that performs up to CD-R recording and reproduction, the wavelength is 0.78 μm and 0.63 to 0.68.
It is necessary to provide two μm light sources.

On the other hand, the demand for downsizing, thinning, and cost reduction of an optical head device has led to a tendency to share the optical system of a CD and a DVD as much as possible. For example, only a converging lens is used for a DVD optical disc. And two types of convergence lenses for CD and CD, and a common convergence lens, and mechanically or optically changing the NA so that only the NA is large for DVD optical disks and small for CDs. Has been taken. Further, in recent years, a technology has been developed in which a light emitting layer of an infrared laser and a light emitting layer of a red laser are formed on a one-chip semiconductor laser to integrate a light source.
Also, a two-wavelength light source in which two types of semiconductor laser chips are mounted in one package has been developed. Hereinafter, the above two light sources are collectively referred to as a two-wavelength LD for convenience. Hereinafter, a method of driving the two-wavelength LD will be described.

FIG. 8 is a block diagram of a conventional laser drive circuit. In FIG. 8, reference numeral 1 denotes a semiconductor laser, 2 denotes a photodiode, and a photodetector for monitoring the output of the semiconductor laser 1. 3 is a common terminal, 4 is a variable resistor, 5 is an operational amplifier, 6 is an auto power control circuit (hereinafter referred to as A
Reference numeral 31 denotes a region in the optical head of the laser drive circuit. The operation of the laser driving circuit configured as described above will be described below.

In FIG. 8, the common terminal 3 is held at a positive potential by a power supply (not shown). Next, when the APC circuit 6 starts operating, a current flows through the semiconductor laser 1 and the semiconductor laser 1 emits light. When a part of the light emitted from the semiconductor laser 1 is received by the photodiode 2, a current flows from the common terminal 3 to the ground terminal via the photodiode 2 and the variable resistor 4 according to the intensity of the emitted light, 4
Voltage is generated across The potential on the photodiode 2 side of the variable resistor 4 is detected by the operational amplifier 5 and fed back to the APC circuit 6. The APC circuit 6 keeps the optical output of the semiconductor laser 1 constant by controlling the current flowing through the semiconductor laser 1 so that the voltage of the variable resistor 4 becomes a predetermined voltage. The resistance value of the variable resistor 4 is adjusted so that the light output of the semiconductor laser 1 becomes a desired value.

In the above-mentioned conventional example, there is one output monitoring photodetector for one semiconductor laser. However, in a two-wavelength LD which has been recently developed, as shown in FIG. In contrast, there is often only one output monitoring photodetector.

FIG. 9 is a circuit block diagram of a two-wavelength LD, in which 1a is a first semiconductor laser,
1b is a second semiconductor laser. Reference numeral 2 denotes a photodiode, which is a photodetector for monitoring the output of a semiconductor laser. 3 is a common terminal. In order to reduce the cost and size of the light source, there is only one photodiode 2 and one output terminal of the photodiode 2. In FIG. 9, 1a and 1b are two semiconductor lasers, but may be different light emitting layers of one laser chip.

When the above-described laser driving circuit is used as a circuit for driving a two-wavelength LD as shown in FIG.
The configuration shown in FIG. FIG. 10 is a block diagram of a driving circuit for a two-wavelength LD. In FIG. 10, the same components as those in FIG. 9 are denoted by the same reference numerals and description thereof is omitted. In FIG. 8, reference numerals 4a and 4b denote variable resistors, reference numerals 5a and 5b denote operational amplifiers, reference numerals 6a and 6b denote APC circuits, reference numerals 7a and 7b denote electronic switches, and a broken line 31 denotes an area of the laser drive circuit in the optical head.

The operation of driving the semiconductor laser shown in FIG. 10 will be briefly described. When driving the first semiconductor laser 1a, the first electronic switch 7a is turned on and the electronic switch 7b is turned off. APC circuit 6
a, the first semiconductor laser 1a starts emitting light,
Since a current flows through the photodiode 2 through the variable resistor 4a by the action of the electronic switches 7a and 7b, a voltage is generated at both ends of the variable resistor 4a based on the adjustment value of the variable resistor 4a. By adjusting the resistance value of the variable resistor 4a similarly to the circuit, the first semiconductor laser 1a can be driven with a desired optical output.

Next, when driving the second semiconductor laser 1b, the first electronic switch 7a is turned off and the second electronic switch 7b is turned on. Since a current flows through the photodiode 2 through the second variable resistor 4b, a voltage is generated based on the adjustment value of the second variable resistor 4b, and the second variable resistor 4b is adjusted by adjusting the resistance value of the second variable resistor 4b. Semiconductor laser 1b can emit light with a desired optical output.

[0014]

However, the above-mentioned 2
In the configuration of the wavelength LD drive circuit, the variable resistors 4a and 4b
Are connected in series with the electronic switches 7a and 7b, respectively. The electronic switch has a slight resistance component even in the connected state, and a potential difference occurs when a current flows.
Therefore, the potential appearing on the photodiode side of the variable resistor is determined not only by the variable resistor but also by a potential difference caused by an electronic switch connected in series. When the variable resistance is adjusted so that the laser output becomes a desired value, the adjustment includes the resistance value of the electronic switch.

[0015] Therefore, when the optical head is incorporated in an arbitrary optical information processing apparatus, a connection state is established between an electronic switch on the apparatus and an electronic switch connected when the laser output was previously adjusted. If there is a difference between the resistance values, the output of the laser changes from a desired value. This has a problem that the recording / reproducing performance is unstable. Further, in order to compensate for this, a means for readjusting the optical output in the optical information processing apparatus is required, and there is a problem that the cost increases. Therefore, the optical head device equipped with the two-wavelength LD driven by the two-wavelength LD drive circuit, and eventually the optical information device, also have the problems that the cost increases and the recording / reproducing performance deteriorates.

The present invention solves the above-mentioned problems, and comprises an electronic switch connected in series to a variable resistor.
Laser drive circuit, optical head, and optical information processing device mounted in an optical head and reducing the laser output variation by adjusting the laser output including the variation in the resistance value of the electronic switch, and improving the stability of the recording / reproducing characteristics The purpose is to provide.

[0017]

SUMMARY OF THE INVENTION For this purpose, the present invention comprises a plurality of laser light sources mounted on an optical head, a photodetector for detecting light emitted from the laser light source, and a serially connected photodetector. One to one connected to multiple laser light sources
A plurality of variable resistors connected in parallel with each other, a plurality of electronic switches serially connected one-to-one with the variable resistor to select an effective one of the plurality of variable resistors, and a variable resistor And a means for controlling the output of the laser light source corresponding to the variable resistor outside the optical head so that the detected voltage value becomes a constant value. An electronic switch for selecting a variable resistor is mounted on an optical head.

Further, there is provided an optical head device provided with the above laser driving device.

Further, there is provided an optical information processing apparatus provided with the above laser driving device.

[0020]

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a circuit block diagram of a laser driving device according to Embodiment 1 of the present invention. In FIG. 1, 1a is a first semiconductor laser, 1b is a second semiconductor laser, 2 is a photodiode, 3 is a common terminal, 4a is a first variable resistor, 4b
Is a second variable resistor, 5a is a first operational amplifier, 5b is a second operational amplifier, 6a is a first APC circuit, and 6b is a second operational amplifier.
APC circuit, 7a is a first electronic switch, 7b is a second electronic switch
Electronic switch. Reference numeral 31 denotes an area included in the optical head including an optical system (not shown).

First, the case of driving the first semiconductor laser 1a will be described. When a current is supplied to the first semiconductor laser 1a by the first APC circuit 6a to emit light, the photodiode 2 receives a part of the light and the current starts flowing.

At this time, the second APC circuit 6b is stopped by control from a control circuit (not shown) or the like, and the second APC circuit 6b is stopped.
Is not emitting light, the first electronic switch 7a is in the connected state, and the second electronic switch 7b is in the disconnected state. Therefore, the current flowing out of the photodiode 2 is equal to that of the first semiconductor laser 1a. The current corresponds to the light emission output, and the current flows to the ground terminal through the first variable resistor 4a and the first electronic switch 7a.

At this time, the current at the end of the first variable resistor 4a on the photodiode 2 side depends on the sum of the resistance value of the first variable resistor 4a and the resistance value in the connection state of the first electronic switch 7a. Voltage is generated. This voltage is detected by the first operational amplifier 5a and fed back to the first APC circuit 6a.

The first APC circuit 6a controls the driving current of the first semiconductor laser 1a so that this voltage becomes a predetermined voltage. By adjusting the resistance value of the first variable resistor 4a, the first semiconductor laser 1a can emit light with a desired optical output.

Next, the case of driving the second semiconductor laser 1b will be described. When a current is supplied to the second semiconductor laser 1b by the second APC circuit 6b to emit light, a part of the light is received and a current flows out of the photodiode 2.

The difference from the operation of the first semiconductor laser 1a is that the electronic switch 7b is in the connected state and the first electronic switch 7a is in the disconnected state.
Since the current from the photodiode 2 flows to the ground potential through the second variable resistor 4b and the second electronic switch 7b, the second variable resistor 4b is connected to the terminal of the second variable resistor 4b on the photodiode 2 side by the current. A voltage is generated according to the resistance value in the connection state between 4b and the second electronic switch 7b.

This voltage is detected by the second operational amplifier 5b and fed back to the second APC circuit 6b. The second APC circuit 6b controls the drive current of the second semiconductor laser 1b so that this voltage becomes a predetermined voltage. By adjusting the resistance value of the second variable resistor 4b, the second semiconductor laser 1b can emit light with a desired output.

In the configuration described above, even if there is a variation in the resistance value of the connection state of the first electronic switch 7a, the first variable switch 4a is adjusted to include the variation at the time of adjustment. Since the combination of the first electronic switch 7a and the first variable resistor 4a does not change, the first optical laser output from the first semiconductor laser 1a is not affected by the optical head attached to any optical information processing device or optical output adjustment device. Of the variable resistor 4a does not change. Similarly, since the combination of the second electronic switch 7b and the second variable resistor 4b does not change, the voltage at the end of the second variable resistor 4b with respect to the optical output of the second semiconductor laser does not change, and the adjustment of the optical head is performed. Light can be emitted with the same light output as at the time.

Therefore, for example, when an optical information processing apparatus is manufactured, only the optical head is combined with a device exclusively for adjusting the optical output to adjust the optical output, and the optical head is attached to a separately manufactured optical information processing apparatus body. However, since the light can be emitted with the same light output as that at the time of adjusting the optical head, variations in the light output can be suppressed and stable recording / reproducing performance can be obtained.

Further, in order to suppress the variation, it is not necessary to adjust the optical output again after the optical disk device is mounted.

Further, even when it is necessary to replace only the optical head for repair or the like, it is possible to suppress variations in the optical output without re-adjusting the optical transfer power after the replacement.

In this embodiment, the number of semiconductor lasers is set to two. However, even in the case of three or more, the number of variable resistors is prepared by the number of semiconductor lasers and connected in series with an electronic switch to set the respective voltage. It goes without saying that the light output of each semiconductor laser can be controlled to be constant by detecting and feeding back the value.

(Embodiment 2) Hereinafter, Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a circuit block diagram of a laser driving device according to Embodiment 2 of the present invention. 2, components having the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

The difference from FIG. 1 is that the first electronic switch 7
The input of a and the input of the second electronic switch 7b are one for the optical head 31, and the polarity of connection and disconnection of the second electronic switch 7b with respect to the input is reversed. It is.

The operation of driving the first semiconductor laser 1a and the second semiconductor laser 1b in the laser driving apparatus constructed as described above is almost the same as in the first embodiment, but the first electronic switch 7a is connected. The second electronic switch 7b that receives the same input signal at the same time as the input for setting the state is turned off. Further, the second electronic switch 7b, which receives the same input signal at the same time as the input for turning off the first electronic switch 7a, is in a connected state.

For this reason, the two electronic switches 7a and 7
b cannot be connected at the same time,
As described in the first embodiment, the first semiconductor laser 1a
Is emitting light, the second semiconductor laser 1b is off, and when the second semiconductor laser 1b is emitting light, the first semiconductor laser 1a is off, and the two semiconductor lasers emit light simultaneously. There is no problem, so there is no problem. When the two lasers are turned off at the same time, both the first APC circuit 6a and the second APC circuit 6b are not operating, so the first electronic switch 7a and the second electronic switch 7b are connected and disconnected. It doesn't matter which of the states it is.

With the above configuration, the number of terminals for controlling the electronic switch connected to the optical head can be reduced to one, and the size of the laser driving device can be reduced.

(Embodiment 3) Hereinafter, Embodiment 3 of the present invention will be described with reference to FIG. FIG. 3 is a configuration diagram showing an optical head device according to the third embodiment. In FIG. 3, reference numeral 8 denotes a two-wavelength light receiving / emitting unit, which includes a two-wavelength LD, a photodetector for detecting light reflected from the optical information medium, and a hologram 9, and a driving device for the two-wavelength LD is used in the present invention. The laser driving device described in the first embodiment is used. Reference numeral 9 denotes a hologram, which has the function of diffracting light and leading it to the above-described photodetector. 10 is a condenser lens, 11 is a rising mirror, 12 is a wavelength-selective aperture, and 0.65
Light having a wavelength of μm is totally transmitted, and light having a wavelength of 0.78 μm is transmitted only in the range of 0.45 as the NA of the objective lens 13. 13 is an objective lens, 14 is C
D optical disk and 15 are DVD optical disks.

FIG. 3A shows a reproduction state of a CD, in which the wavelength 0.78 emitted from the two-wavelength light receiving / emitting unit 8 is used.
The μm laser light is converted into parallel light by the condenser lens 10, the optical path is bent by the rising mirror 11, and enters the wavelength-selective aperture 12. The light converged by the wavelength-selective aperture 12 is condensed on a CD optical disc 14 by an objective lens 13. The light reflected by the CD optical disk 14 returns to the objective lens 13, the rising mirror 11, and the condenser lens 10 in the reverse direction, and is diffracted by the hologram 9 and
The light is photoelectrically converted by the photodetector of the wavelength receiving / emitting unit 8 and detected as an electric signal.

Next, at the time of reproducing the DVD, the wavelength 0.65 μm emitted from the two-wavelength light receiving / emitting unit 8 in FIG.
m laser light is converted into parallel light by the condenser lens 10,
The optical path is bent by the rising mirror 11 and enters the wavelength-selective aperture 12. The light transmitted through the wavelength-selective aperture 12 is focused on the DVD optical disc 14 by the objective lens 13. The light reflected by the DVD optical disk 14 is divided into an objective lens 13, a rising mirror 11, and a condenser lens 10.
The light is diffracted by the hologram 9, photoelectrically converted by the photodetector of the two-wavelength light emitting / receiving unit 8, and detected as an electric signal.

The electrical signal photoelectrically converted and detected by the photodetector is used as an RF signal of a pit row on the optical disk and a servo signal for tracing the pit row. Although not particularly shown, a known three-beam method can be used for tracking servo during CD reproduction. Since the present optical head device uses the laser driving device of the present invention, it is possible to obtain a stable recording / reproducing performance with little variation in optical output.

(Embodiment 4) Hereinafter, Embodiment 4 of the present invention will be described with reference to FIG. FIG. 4 is a configuration diagram of an optical information processing apparatus according to Embodiment 4 of the present invention.
In FIG. 4, reference numeral 16 denotes an optical head device described in the third embodiment of the present invention, reference numeral 17 denotes an optical disk, and reference numeral 18 denotes a motor, which supports and rotates the optical disk 17. 19 is a circuit board, and 20 is a power supply.

The optical disk 17 is rotated by a motor 18. The optical head device 16 sends a signal corresponding to the positional relationship with the optical disc 17 to the circuit board 19. The circuit board 19 calculates this signal and outputs a signal for finely moving the optical head device 16 or the objective lens in the optical head device 16. The optical head device 16 or the objective lens in the optical head device 16 is driven by a driving mechanism (not shown).
Focus servo and tracking servo are performed on the optical disk 17, and information is read, written, or erased on the optical disk 17. Reference numeral 20 denotes a connection portion for a power supply or an external power supply, and a circuit board 1
9. Supply electricity to the drive mechanism of the optical head device, the motor 18 and the objective lens drive device. It should be noted that there is no problem even if a connection terminal for a power supply or an external power supply is provided in each drive circuit.

Embodiment 5 Hereinafter, Embodiment 5 of the present invention will be described with reference to FIG. FIG. 5 is a circuit block diagram of a laser driving device according to the fifth embodiment of the present invention. 5, components having the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

First, the case where the first semiconductor laser 1a is driven will be described. When a current is supplied to the first semiconductor laser 1a by the first APC circuit 6a to emit light, the photodiode 2 receives a part of the light and the current starts flowing.

At this time, the second APC circuit 6b is stopped by control from a control circuit (not shown) or the like, and the second APC circuit 6b is stopped.
Is not emitting light, the first electronic switch 7a is in the connected state, and the second electronic switch 7b is in the disconnected state. Therefore, the current flowing out of the photodiode 2 is equal to that of the first semiconductor laser 1a. The current corresponds to the light emission output, and the current flows to the ground terminal through the first electronic switch 7a and the first variable resistor 4a.

At this time, a voltage corresponding to the resistance value of the variable resistor 4a is generated by the current at the end of the variable resistor 4a on the first electronic switch 7a side. This voltage is detected by the operational amplifier 5a and fed back to the APC circuit 6a.

The APC circuit 6a controls the driving current of the first semiconductor laser 1a so that this voltage becomes a predetermined voltage. By adjusting the resistance value of the variable resistor 4a, the first
Semiconductor laser 1a can emit light with a desired optical output.

Next, the case of driving the second semiconductor laser 1b will be described. When a current is supplied to the second semiconductor laser 2b by the second APC circuit 6b to emit light, a part of the light is received and a current flows out of the photodiode 2.

The difference from the driving of the first semiconductor laser 1a is that the electronic switch 7b is in the connected state and the first electronic switch 7a is in the disconnected state.
The current from the photodiode is supplied to the second electronic switch 7b.
Since the current flows through the variable resistor 4b to the ground potential, a voltage corresponding to the resistance value of the variable resistor 4b is generated by the current at the terminal of the variable resistor 4b on the side of the electronic switch 7b.

This voltage is detected by the operational amplifier 5b and fed back to the APC circuit 6b. The APC circuit 6b controls the drive current of the second semiconductor laser 1b so that this voltage becomes a predetermined voltage. The second semiconductor laser 1b is adjusted by adjusting the resistance value of the variable resistor 4b.
Can emit light with a desired output.

In the above configuration, the potential of the first electronic switch 7a side terminal of the variable resistor 4a with respect to the ground potential is irrelevant to the resistance value of the connection state of the first electronic switch 7a. Even if there is a variation in the resistance value of the connection state of the electronic switch 7a, or even if the resistance value changes due to a change in the surrounding environment or the like, the end of the variable resistor 4a with respect to the optical output of the first semiconductor laser 1a. The voltage does not change, and light can always be emitted with the same light output as during adjustment.

Similarly, the potential of the electronic switch 7b side terminal of the variable resistor 4b is irrelevant to the variation of the resistance value of the connection state of the electronic switch 7b. Light can be emitted at the output.

Therefore, for example, at the time of manufacturing an optical information processing apparatus, it is assumed that the optical output is adjusted by combining only the optical head with a device exclusively for adjusting the optical output, and the optical head is mounted on a separately manufactured optical information processing apparatus body. However, since the light can be emitted with the same light output as that at the time of adjusting the optical head, variations in the light output can be suppressed and stable recording / reproducing performance can be obtained.

Further, in order to suppress the variation, it is not necessary to adjust the optical output again after mounting the optical information processing apparatus.

Further, even when it is necessary to replace only the optical head for the reason of repair or the like, it is possible to suppress variations in the optical output without having to readjust the optical transfer power after the replacement.

Further, a change in light output due to a change in the surrounding environment can be reduced, and stable recording / reproducing performance can be obtained.

In this embodiment, the number of semiconductor lasers is set to two. However, even when the number of semiconductor lasers is three or more, the number of variable resistors is prepared by the number of semiconductor lasers, connected in series with an electronic switch, and the respective voltages are set. It goes without saying that the light output of each semiconductor laser can be controlled to be constant by detecting and feeding back the value.

Embodiment 6 Hereinafter, Embodiment 6 of the present invention will be described with reference to FIG. FIG. 6 is a configuration diagram showing an optical head device according to the sixth embodiment. 6, components having the same functions as those in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 6, 38 is 2
A wavelength receiving / emitting unit, comprising a two-wavelength LD, a photodetector for detecting light reflected from an optical information medium, and a hologram 9; and a driving device for the two-wavelength LD, the laser described in the fifth embodiment of the present invention. A drive circuit is used.

FIG. 6A shows a reproduction state of a CD, in which the wavelength 0.7 emitted from the two-wavelength light receiving / emitting unit 38 is used.
The 8 μm laser light is converted into parallel light by the condenser lens 10, the optical path is bent by the rising mirror 11, and enters the wavelength-selective aperture 12. The light converged by the wavelength-selective aperture 12 is condensed on a CD optical disc 14 by an objective lens 13. The light reflected by the CD optical disk 14 returns to the objective lens 13, the rising mirror 11, and the condenser lens 10 in the reverse direction, and is diffracted by the hologram 9 and
The light is photoelectrically converted by the photodetector of the wavelength receiving / emitting unit 38 and detected as an electric signal.

Next, at the time of reproducing the DVD, the wavelength 0.65 emitted from the two-wavelength light receiving / emitting unit 38 in FIG.
The μm laser light is converted into parallel light by the condenser lens 10, the optical path is bent by the rising mirror 11, and enters the wavelength-selective aperture 12. The light transmitted through the wavelength-selective aperture 12 is transmitted to the DVD optical disk 14 by the objective lens 13.
Is collected. The light reflected by the DVD optical disk 14 returns to the objective lens 13, the rising mirror 11, and the condensing lens 10 in the reverse direction, is diffracted by the hologram 9, is photoelectrically converted by the photodetector of the two-wavelength light receiving / emitting unit 38, and is converted into an electric signal. Is detected as

The electric signal photoelectrically converted and detected by the photodetector is used as an RF signal of a pit row on the optical disk and a servo signal for tracing the pit row. Although not particularly shown, a known three-beam method can be used for tracking servo during CD reproduction. Since the present optical head device uses the laser driving device of the present invention, it is possible to obtain a stable recording / reproducing performance with little variation in optical output.

Embodiment 7 Hereinafter, Embodiment 7 of the present invention will be described with reference to FIG. FIG. 7 is a configuration diagram of an optical information processing apparatus according to Embodiment 7 of the present invention.
7, components having the same functions as those in FIG. 4 are denoted by the same reference numerals, and description thereof is omitted. In FIG.
Reference numeral 36 denotes the optical head device described in the sixth embodiment.

The optical disk 17 is rotated by a motor 18. The optical head device 36 sends a signal corresponding to the positional relationship with the optical disc 17 to the circuit board 19. The circuit board 19 calculates this signal and outputs a signal for finely moving the objective lens in the optical head device 36 or the optical head device 16. The optical head device 36 or an objective lens in the optical head device 36 performs focus servo and tracking servo on the optical disk 17 by a drive mechanism (not shown), and reads, writes, or erases information on the optical disk 17. Reference numeral 20 denotes a connection portion for a power supply or an external power supply, and a circuit board 1
9. Supply electricity to the drive mechanism of the optical head device, the motor 18 and the objective lens drive device. It should be noted that there is no problem even if a connection terminal for a power supply or an external power supply is provided in each drive circuit.

[0065]

As described above, according to the present invention, one photodetector corresponding to a plurality of semiconductor lasers, a variable resistor connected in series to the photodetector, and a variable resistor connected in series to the variable resistor. By adopting a configuration in which an electronic switch for selecting an effective variable resistor is provided in the optical head, it is possible to provide a laser driving device in which variation in optical output is suppressed.

Further, by using the laser driving device of the present invention, it is possible to provide an optical head device which has little variation in optical output and does not require readjustment of optical output when mounted on an optical information processing device.

Further, according to the present invention, it is possible to provide an optical information processing apparatus which is compatible with various optical disk media at low cost, has a small variation in light quantity, and has stable recording and reproducing performance.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a laser driving device according to a first embodiment of the present invention.

FIG. 2 is a circuit block diagram of a laser driving device according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing an optical head device according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing an optical information processing apparatus according to Embodiment 4 of the present invention.

FIG. 5 is a circuit block diagram of a laser driving device according to a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram showing an optical head device according to a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram illustrating an optical information processing apparatus according to a seventh embodiment of the present invention.

FIG. 8 is a block diagram of a conventional LD drive circuit.

FIG. 9 is a block diagram of a circuit of a two-wavelength LD.

FIG. 10 is a block diagram of a drive circuit for a two-wavelength LD.

[Explanation of symbols]

 1a first semiconductor laser 1b second semiconductor laser 2 photodiode 3 common terminal 4a first variable resistor 4b second variable resistor 5a first operational amplifier 5b second operational amplifier 6a first APC circuit 6b second APC circuit 7a First electronic switch 7b Second electronic switch 31 Area inside optical head

Continued on the front page (72) Inventor Hideki Hayashi 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshihiro Kanda 1006 Oji Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. Person Shinichi Kadowaki 1006 Kazuma, Kazuma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshiaki Kinma 1006 Kazuma, Kazuma Kadoma, Osaka Pref. AA21 AA41 BA01 FA08 HA36 HA68 5F073 BA06 EA15 GA02 GA22

Claims (8)

[Claims] A plurality of laser light sources mounted on an optical head; a photodetector detecting light emitted from the plurality of laser light sources; and a plurality of laser light sources connected in series to the photodetector. And a plurality of variable resistors that are connected in parallel with each other, and are connected in series with the plurality of variable resistors in a one-to-one relationship to select an effective one of the plurality of variable resistors. A plurality of electronic switches, and means for detecting the voltage of the variable resistor, and means for controlling the output of the laser light source corresponding to the variable resistor outside the optical head so that the voltage value becomes a constant value. A laser drive device comprising: an electronic switch mounted on an optical head for selecting an effective variable resistor. 2. The laser driving device according to claim 1, wherein the electronic switch is connected between the variable resistor and a reference potential. 3. A laser device comprising: two laser light sources; and two electronic switches corresponding to the laser light sources on a one-to-one basis.
3. The laser driving device according to claim 2, wherein the operation of the two electronic switches is opposite to the operation of connection and disconnection with respect to an input for switching between connection and disconnection. 4. A light comprising: the laser driving device according to claim 2; means for condensing light emitted from the laser driving device on an optical information medium; and a photodetector for detecting reflected light from the optical information medium. Head device. 5. An optical information medium, a driving mechanism of the optical information medium, an optical head device according to claim 4, and a focus servo using each of a focus error signal and a tracking error signal obtained from the optical head device. An optical information processing device having at least a mechanism, a tracking servo mechanism, an electric circuit for realizing the servo mechanism, and a power supply. 6. The variable resistor is provided between the electronic switch and a reference potential, and is connected to a means for detecting a voltage of the variable resistor between the variable resistor and the electronic switch. The laser driving device according to claim 1, wherein 7. A light comprising: the laser driving device according to claim 6; means for condensing light emitted from the laser driving device on an optical information medium; and a photodetector for detecting reflected light from the optical information medium. Head device. 8. An optical information medium, a driving mechanism of the optical information medium, an optical head device according to claim 7, and a focus servo using each of a focus error signal and a tracking error signal obtained from the optical head device. An optical information processing device having at least a mechanism, a tracking servo mechanism, an electric circuit for realizing the servo mechanism, and a power supply.