JP2007280453A - Laser drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that an oscillation output adjustment circuit may not be able to adjust to a stated oscillation optical output due to occurrence of deterioration of laser by eddy current etc. , since variation in semiconductor laser is large and when a variable resistance is used, the resolution is low and hard to adjust. <P>SOLUTION: A laser drive device is equipped with; a semiconductor lasers 1a and 1b which oscillate in different wavelengths; APC circuits 3a and 3b which control oscillation optical output of the semiconductor lasers 1a and 1b; and a target oscillation optical output regulator 10 which adjusts target oscillation optical output of the APC circuits 3a and 3b. The target oscillation optical output regulator 10 consists of combined resistance values of a fixed resistance 5 and a variable resistor 4 and controls the APC circuits 3a and 3b based on the configuration resistance value concerned. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser driving device of an optical pickup device of an optical disk drive for reproducing or recording an optical disk such as a DVD.

  An optical pickup device that reads information recorded on an optical disk such as a DVD or CD irradiates a recording signal surface of the optical disk with laser light emitted from a semiconductor laser, receives reflected light from the optical disk, and receives a reproduction signal or a control signal. Have gained. In general, since the oscillation light output of a semiconductor laser changes depending on the ambient temperature, aging, etc., the optical pickup device uses an oscillation light output adjustment circuit and an automatic power control (abbreviation: APC) circuit to drive the semiconductor laser. Is controlled, and the oscillation light output is kept constant.

  Incidentally, in the CD, the wavelength of the light source is approximately 0.78 μm, and the numerical aperture of the converging lens (hereinafter abbreviated as NA) is approximately 0.45, whereas in the DVD optical disk, the wavelength of the light source is approximately 0. 63 μm to 0.68 μm, NA is approximately 0.6. Accordingly, when recording and reproducing two types of optical disks, ie, CD and DVD optical disks, with one optical information processing apparatus, an optical head apparatus having two optical systems is required. In particular, the recordable CD-R, which is a derivative form of CD, which has been widely used in recent years, is optimized for a wavelength of 0.78 μm for the reflective film on the disc. Since reproduction cannot be performed at a wavelength, an optical information processing apparatus that performs CD-R recording / reproduction in addition to DVD and CD needs to include two light sources having wavelengths of approximately 0.78 μm and 0.63 μm to 0.68 μm.

  On the other hand, in order to reduce the size, thickness, and cost of optical head devices, CD and DVD optical systems are in the direction of being shared as much as possible. For example, only a converging lens is used for DVD optical disks and CDs. These two types of converging lenses can be switched, or the converging lenses can be shared, so that only the NA is changed mechanically or optically so that it is larger for DVD optical discs and smaller for CDs. Yes. Furthermore, in recent years, a technique has been developed in which a light source is also integrated by forming a light emitting layer of an infrared laser and a light emitting layer of a red laser on a one-chip semiconductor laser. A two-wavelength light source in which two types of semiconductor laser chips are mounted in one package has also been developed. Hereinafter, the two light sources described above are collectively referred to as a two-wavelength laser for convenience. A method for driving the two-wavelength laser is proposed in Patent Document 1, for example.

  FIG. 5 shows a simplified configuration diagram of the two-wavelength laser driving apparatus proposed in Patent Document 1, and the driving operation of the semiconductor laser will be briefly described. In the figure, an oscillation light output adjuster that adjusts the target oscillation light output of the APC circuits 3a and 3b, where 1a is a first semiconductor laser, which is a different light emitting layer of one semiconductor laser chip, and 1b is a second semiconductor laser. The target oscillation light output adjustment circuit is set to 10. When driving the first semiconductor laser 1a, the first APC circuit 3a operates and the first semiconductor laser 1a emits light. When a part of the emitted light of the first semiconductor laser 1a is received by the photodiode 2, a current flows to the ground terminal via the monitoring light receiving element 2 and the variable resistor 4a according to the intensity of the emitted light, and is variable. A voltage is generated across the resistor 4a. The APC circuit 3a keeps the optical output of the first semiconductor laser 1a constant by controlling the current flowing through the first semiconductor laser 1a so that the voltage of the variable resistor 4a becomes a predetermined voltage. The resistance value of the variable resistor 4a is adjusted so that the optical output of the first semiconductor laser 1a becomes a desired value.

  Next, when driving the second semiconductor laser 1b, the second APC circuit 3b operates and the second semiconductor laser 1b emits light. Since the two-wavelength laser often has only one output monitor photodetector for the two light sources as shown in FIG. 5, even when the second semiconductor laser chip 1b emits light, the second semiconductor laser chip A part of the laser light irradiated to the optical disk from 1b is also received by the monitor light receiving element 2.

Since a current flows through the monitor light-receiving element 2 through the second variable resistor 4b, a voltage is generated based on the adjustment value of the second variable resistor 4b, and the resistance value of the second variable resistor 4b is adjusted. The second semiconductor laser 1b can emit light with a desired light output.
JP 2001-266388 A

  However, in the configuration of the above two-wavelength laser driving device, the variable resistors 4a and 4b are required. In recent years, there has been an increasing demand for miniaturization and price reduction of optical pickup devices, and adjusting each of the two variable resistors requires man-hours and costs, and requires a mounting area. There was a problem of becoming an obstacle to the transformation.

  SUMMARY OF THE INVENTION The present invention has been made for the purpose of providing a laser driving device for an optical pickup device that does not require man-hours, is easy to adjust, and has a small mounting area.

  In order to solve this problem, a laser driving device according to the present invention irradiates an optical disk with a semiconductor laser that oscillates laser light having a plurality of wavelengths and laser light emitted from the semiconductor laser, and the signal of the optical disk is reflected. A light receiving element that receives the laser light and an oscillation light output adjuster that adjusts a target oscillation light output of an automatic output control circuit that controls the oscillation light output of the semiconductor laser, and the oscillation light output adjuster Since it is composed of one variable resistor connected in series to the element and a plurality of parallel-connected pattern wirings connected in series to the variable resistor and corresponding one-to-one to the plurality of semiconductor lasers. By adjusting the resistance, the oscillation light output of a plurality of semiconductor lasers can be adjusted at a time, and the cost can be reduced by downsizing and simplifying the adjustment process.

  As described above, according to the laser driving device of the present invention, it is possible to reduce the number of adjustment steps and reduce the size of the optical pickup.

  The best embodiment of the laser driving device of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram relating to oscillation light output control according to an embodiment of the laser driving apparatus of the present invention. In the figure, when the first semiconductor laser 1a is driven, the first APC circuit 3a operates and the first semiconductor laser 1a emits light. When a part of the emitted light of the first semiconductor laser 1a is received by the monitoring light receiving element 2, a current flows to the ground terminal via the monitoring light receiving element 2 and the variable resistor 4 according to the intensity of the emitted light. A voltage is generated across the variable resistor 4. The APC circuit 3a keeps the optical output of the first semiconductor laser 1a constant by controlling the current passed through the first semiconductor laser 1a 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 optical output of the first semiconductor laser 1a becomes a desired value.

  Next, when driving the second semiconductor laser 1b, the second APC circuit 3b operates and the second semiconductor laser 1b emits light. Since a current flows through the monitor light receiving element 2 through the second variable resistor 4 and the fixed resistor 5, a voltage is generated based on a combined resistance value of the variable resistor 4 and the fixed resistor 5.

  Oscillation light output of two semiconductor lasers is emitted from one semiconductor laser chip and uses the same optical system and the same light receiving element. Therefore, an optical pickup in which a semiconductor laser chip is mounted on each conventional CD / DVD. Since it is possible to suppress variations more than the apparatus, the difference in light output between the first semiconductor laser 1 a and the second semiconductor laser 1 b is determined by the fixed resistor 5.

(Embodiment 2)
FIG. 2 is a configuration diagram relating to oscillation light output control of another embodiment of the laser driving device of the present invention. In the figure, when the first semiconductor laser 1a is driven, the first APC circuit 3a operates and the first semiconductor laser 1a emits light. When a part of the emitted light of the semiconductor laser 1a is received by the monitoring light receiving element 2, a current flows to the ground terminal via the monitoring light receiving element 2 and the variable resistor 4 according to the intensity of the emitted light, and the variable resistance A voltage is generated across 4. The APC circuit 3a keeps the optical output of the first semiconductor laser 1a constant by controlling the current passed through the first semiconductor laser 1a 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 optical output of the first semiconductor laser 1a becomes a desired value.

  Next, when driving the second semiconductor laser 1b, the second APC circuit 3b operates and the second semiconductor laser 1b emits light. Since a current flows through the variable light resistance circuit 6 including the variable resistance 4, the fixed resistance, and the resistance value change-over switch, a voltage is generated based on the combined resistance value of the variable resistance 4 and the variable resistance circuit 6. To do.

  Since the oscillation light outputs of the two semiconductor lasers are emitted from one semiconductor laser chip and use the same optical system and the same light receiving element, the conventional optical pickup device in which the semiconductor laser chip is mounted on each CD / DVD Therefore, even the variable resistance circuit 6 having a low resolution can adjust the optical output of the semiconductor laser 1b to a desired value.

  With a resistance value that reduces the oscillation light output, emit the semiconductor laser, irradiate the recording signal surface of the optical disk with the laser light of the semiconductor laser, and measure the reproduction signal obtained by receiving the reflected light from the optical disk Then, the oscillation light output can be adjusted within a certain range by switching the resistance value switch according to the reproduction signal amount.

  In the variable resistance circuit 6, the fixed resistors are configured in series, but may be configured in parallel.

(Embodiment 3)
FIG. 3 is a configuration diagram relating to oscillation light output control according to another embodiment of the laser driving device of the present invention. In the figure, when the first semiconductor laser 1a is driven, the first APC circuit 3a operates and the first semiconductor laser 1a emits light. When a part of the emitted light of the first semiconductor laser 1a is received by the monitoring light receiving element 2, the fixed light resistance that constitutes the monitoring light receiving element 2, the variable resistor 4, and the variable resistance circuit 7 according to the intensity of the emitted light. A current flows to the ground terminal via, and a voltage is generated across the fixed resistors constituting the variable resistor 4 and the variable resistor circuit 7. The APC circuit 3a controls the current flowing through the first semiconductor laser 1a so that the voltages of the fixed resistors constituting the variable resistor 4 and the variable resistor circuit 7 become a predetermined voltage, whereby the first semiconductor laser 1a Keep the light output constant. The resistance value of the variable resistor 4 is adjusted so that the optical output of the first semiconductor laser 1a becomes a desired value.

  Next, when driving the second semiconductor laser 1b, the second APC circuit 3b operates and the second semiconductor laser 1b emits light. Since a current flows through the monitor light-receiving element 2 through the variable resistor circuit 7 constituted by the second variable resistor 4, the fixed resistor, and the resistance value changeover switch, based on the combined resistance value of the variable resistor 4 and the variable resistor circuit 7. Voltage is generated.

  FIG. 4 illustrates an example in which the resistance changeover switch according to the second embodiment or the third embodiment is configured by the soldered land 8 and the solder 9 configured by the copper foil of the electric circuit pattern. With this configuration, a circuit can be configured with a smaller mounting area and without adding components.

  Note that at least one of the fixed resistors constituting the variable resistance circuit 7 is a temperature correction resistor, so that the resistance value increases and the oscillation light output decreases as the temperature rises, or vice versa. In addition, the circuit configuration may be such that the resistance value is positively increased when the temperature rises to decrease the oscillation light output, thereby suppressing the rise in the chip temperature of the semiconductor laser and extending the operable temperature range.

  Since the optical pickup device according to the present invention can be reduced in size and cost, it is useful for applications such as an optical pickup device of an optical disc drive for reproducing or recording an optical disc such as a DVD.

1 is a block diagram of the main part of an embodiment of a laser driving apparatus according to the present invention. The principal part block diagram of other embodiment in the laser drive device of this invention The principal part block diagram of another embodiment in the laser drive device of this invention (A) is a conceptual block diagram of the open state of the resistance changeover switch applicable to the laser drive device of this invention, (b) is a conceptual block diagram of the short state of the resistance changeover switch. Schematic configuration diagram of a conventional laser driving device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a 1st semiconductor laser 1b 2nd semiconductor laser 2 Light-receiving element for monitoring 3a, 3b APC circuit 3a
DESCRIPTION OF SYMBOLS 4 Variable resistor 5 Fixed resistance of light emission amount difference 6, 7 Variable resistance circuit for light emission amount difference adjustment 8 Solder land 9 Solder and solder land 10 Target oscillation light output adjustment circuit

Claims (2)

A semiconductor laser that oscillates laser light of a plurality of wavelengths;
A light receiving element that irradiates an optical disc with laser light emitted from the semiconductor laser and receives laser light reflected from a signal of the optical disc;
An oscillation light output adjuster for adjusting a target oscillation light output of an automatic output control circuit for controlling the oscillation light output of the semiconductor laser;
The oscillation light output regulator includes one variable resistor connected in series to the light receiving element,
A laser driving device comprising: a plurality of patterns connected in series to the variable resistor and corresponding to the plurality of semiconductor lasers in a one-to-one correspondence. The oscillation light output regulator includes one variable resistor connected in series to the light receiving element,
2. The laser driving device according to claim 1, comprising a plurality of fixed resistors and resistance value changeover switches which are connected in series to the variable resistors and correspond one-to-one to the plurality of semiconductor lasers.