JP2002288864A - Light source device for optical head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent the useless emission emitted from the light source device of an optical head including a semiconductor laser of single-mode oscillation and a semiconductor laser of multi-mode oscillation in its common package which changes the semiconductor laser of single-mode oscillation into that of multi-mode oscillation by a high-frequency oscillation circuit. SOLUTION: In the light source device 10 of the optical head, the semiconductor laser 11 of single-mode oscillation for a DVD reproduction, the high-frequency oscillation circuit 31 superposing a high-frequency current to a driving current and the semiconductor laser 12 of multi-mode oscillation for a CD recording and reproduction are embedded in the common package 13. Noise filters 41, 42, 43 and 44 are inserted in electricity-feeding lines 37, 38, 39 and an earthing line 36 so that each of these feeding lines may not be a useless-emission generating source due to the high-frequency oscillation of the high-frequency oscillation circuit 31. Therefore, it is possible to surely prevent the light source device 10 from becoming a noise-generating source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact disc (CD) and a digital versatile disc (DVD).
The present invention relates to a light source device of an optical head used for recording and reproduction of an optical recording medium such as a recording medium. More specifically, the present invention relates to a light source device for an optical head including a plurality of semiconductor lasers that oscillate in multimode and single mode.

[0002]

2. Description of the Related Art CD (Compact Disk) and DVD
2. Description of the Related Art An optical head used for reproducing an optical recording medium such as a (high-density optical disk) converges a laser beam emitted from a light source equipped with a semiconductor laser to a recording surface of an optical recording medium via an objective lens. The information is reproduced by detecting the return light reflected by the light source by a light receiving element arranged at a position conjugate with the light source.

A part of the return light reflected on the recording surface of the optical recording medium returns to the semiconductor laser by following the same optical path as the emitted light in reverse. When the propagation mode of the semiconductor laser light is a single mode, such a laser return light component has a bad influence on the light emitting operation of the semiconductor laser, and is a major cause of generating unwanted noise when recording and reproducing information. . Conventionally, in order to prevent this problem, a high-frequency oscillation circuit is used to superimpose a high-frequency current on a driving current of the semiconductor laser and supply the superposed current to the semiconductor laser, so that a single-mode oscillation semiconductor laser is multi-mode. It is trying to become.

Here, when a high-frequency oscillation circuit is arranged, a wiring portion such as a power supply line to the circuit becomes an EMI generation source. Therefore, an unnecessary radiation prevention element or a prevention circuit such as a noise filter is inserted into such a power supply line to
MI measures are taken.

On the other hand, an optical head capable of recording and reproducing information on and from optical recording media having different substrate thicknesses and recording densities, such as CDs and DVDs, requires laser beams of different wavelengths. In other words, 65 to playback of DVD
While 0nm laser light is required, CD-
Since R is a lower reflectance at 650nm wavelength range, in order of the reproduction and recording are required laser beam of 780nm wavelength.

Therefore, an optical head for reproducing a DVD and reproducing and recording a CD-R has a wavelength of 650 nm.
A semiconductor laser emitting a laser beam having a wavelength of 780 n
A light source device equipped with a semiconductor laser that emits m laser light is mounted.

[0007]

Recently, in order to respond to the demand for downsizing the optical head, such a light source device of a plurality of light sources is provided in a common package with a plurality of laser beams emitting different wavelengths. having a structure provided with a semiconductor laser has been proposed. In this case, the semiconductor laser that emits 650 nm laser light used for DVD reproduction is a single mode oscillation type, and the semiconductor laser that emits 780 nm laser light used for CD-R reproduction recording is a self-excited oscillation type. And two semiconductor lasers are selectively driven according to the type of the optical recording medium to be processed.

A high-frequency oscillation circuit is provided to drive a single-mode oscillation semiconductor laser for DVD reproduction with a high-frequency superimposed current. Therefore, it is necessary to take measures against EMI caused by the high-frequency current supplied from the high-frequency oscillation circuit.

Therefore, the present inventor has proposed a method for preventing unnecessary radiation such as a noise filter on a wiring portion which is assumed to be a source of unnecessary radiation during reproduction of a DVD in which the high frequency oscillation circuit operates, that is, a power supply line of the high frequency oscillation circuit. I connected the circuit, but found that the desired effect could not be obtained.

In view of the foregoing, an object of the present invention is to provide a light source device for an optical head in which a single mode oscillation semiconductor laser and a multimode oscillation semiconductor laser are incorporated in a common package. An object of the present invention is to surely prevent an adverse effect due to unnecessary radiation caused by a high-frequency oscillation circuit for superimposing a high-frequency current on a drive current.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a light source device in which a single-mode oscillation semiconductor laser and a multi-mode oscillation semiconductor laser are incorporated in a common package. The wiring line of the multi-mode oscillation semiconductor laser in the state is also focused on as an EMI source.

That is, the present invention provides a common package, a single mode oscillation semiconductor laser and a multi mode oscillation semiconductor laser contained in the package, and a method for converting the single mode oscillation semiconductor laser to a multi mode oscillation. A light source device for an optical head having a high-frequency oscillation circuit that generates a high-frequency current superimposed on the drive current of the semiconductor laser, further comprising an unnecessary radiation prevention unit for preventing unnecessary radiation caused by the high-frequency current, radiation prevention means is characterized in that it comprises a high-frequency component absorption circuit interposed in the feed line of the semiconductor laser of multi-mode oscillation.

Here, as the high frequency component absorbing circuit, a circuit capable of absorbing at least a fundamental frequency component of the high frequency current may be used. For example, a bandpass filter, a choke coil, or a ferrite bead can be used.

In a light source device for an optical head suitable for use in reproducing a DVD and reproducing and recording a CD-R, the multi-mode oscillation semiconductor laser emits 780 nm laser light, and the single-mode oscillation semiconductor laser emits 780 nm laser light. The laser may emit laser light of 635 or 650 nm.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of an optical head incorporating a light source device according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic structural view of the optical head of this embodiment. As shown in this figure, the optical head 1 of the present example has a CD,
A single mode oscillation semiconductor laser 11 for emitting a laser beam L1 having a wavelength of 650 nm and a multi-mode for emitting a laser beam L2 having a wavelength of 780 nm are provided for reproducing a CD-R and a DVD and recording a CD-R. A two-wavelength light source device 10 in which a mode-oscillating semiconductor laser 12 is housed in a common package 13 and a laser beam of each wavelength emitted from the two-wavelength light source device 10 is guided to the recording surface 2a of the optical recording medium 2 and reflected by the recording surface 2a. And a common optical system Lo for guiding the laser return light to the common light receiving element 3.

The common optical system Lo is provided with a diffraction grating 4 for straightening the laser beam L1 emitted from the light source device 10 and deflecting the laser beam L2 to align both optical axes, and a laser beam L1 having the same optical axis. , L2, a flat plate-shaped beam splitter 5, a collimating lens 6 for parallelizing the laser beams L1, L2 reflected by the beam splitter 5, and a laser beam L emitted from the collimating lens 6.
1, an objective lens 7 for converging L2 on the recording surface 2a of the optical recording medium 2 is provided. Recording surface 2 of the optical recording medium 2
The laser return light reflected by a returns along the same path as the laser light on the emission side, is separated from the laser light on the emission side in the beam splitter 5, and is guided to the common light receiving element 3 arranged on the rear side. .

Each part of the optical head 1 is driven and controlled by a control device 20 composed of a computer. That is, based on the laser return light from the common light receiving element 3, the information recorded on the optical recording medium 2 is reproduced, and a tracking error signal and a focusing error signal are generated.
Based on this, the objective lens drive mechanism 22 is driven via the drive circuit 21 to servo-correct the tracking error and the focusing error. Further, the drive of the laser drive control circuit 23 is controlled in accordance with the type of the optical recording medium 3 mounted, and the semiconductor lasers 11 and 12 are selectively driven. The output of each of the semiconductor lasers 11 and 12 is feedback-controlled.

When reproducing information on the DVD as the optical recording medium 3 in the thus configured optical head 1 of the present embodiment, the semiconductor laser 11 emits a laser beam L1 having a wavelength of 650 nm. This laser beam L1 is
Through the optical system L0, converges as a light spot on the recording surface of the DVD by the objective lens 7, and
The return light of the laser beam L1 reflected by the recording surface of (1) is focused on the common light receiving element 3 via the beam splitter 5. The information of the DVD is reproduced based on the signal detected by the common light receiving element 3.

[0020] On the other hand, CD as an optical recording medium 3
In the case of -R reproduction / recording, a laser beam L2 having a wavelength of 780 nm is emitted from the multimode oscillation type semiconductor laser 12.
Is emitted. This laser light L2 is guided to the common optical system Lo via the diffraction grating 4, and
It converged as a light spot on the recording surface of the -R, record of the information and
Playback is performed.

[0021] Figure 2 is a driving power wiring diagram of the light source device 10 and the common light receiving element 3. As shown in this figure, a high-frequency generation circuit 31 for multimode operation of the semiconductor laser 11 of single mode oscillation is mounted on a wiring board 10a of the light source device 10. A driving power supply terminal 32 for supplying driving power to the high-frequency oscillation circuit 31, a driving power supply terminal 33 for supplying driving power to the semiconductor laser 11, and a driving power supply terminal for supplying driving power to the semiconductor laser 12. A power supply terminal 34 and a common ground terminal 35 are arranged.

The high-frequency oscillation circuit 31 oscillates at a high frequency by the driving power supplied from the driving power supply terminal 32,
Semiconductor laser 11 supplied from drive power supply terminal 33
A high-frequency current is superimposed on the driving current, and the driving current on which the high-frequency current is superimposed is supplied to the semiconductor laser 11. On the other hand, the semiconductor laser 12 of multi-mode oscillation is connected between the drive power supply terminal 34 and the common ground line 36, and oscillates with the drive current supplied from the terminal 34.

Here, a noise filter 4 for absorbing or removing a high-frequency component is connected between the terminals 32 and 33 and the high-frequency oscillation circuit 31 and supplied to feed lines 37 and 38.
1, 42 are interposed. A similar noise filter 43 is also interposed in a power supply line 39 from the terminal 34 to the semiconductor laser 12. Furthermore, the common ground line 3
In FIG. 6, a similar noise filter 44 is also inserted in a portion between the ground line connection position of the high-frequency oscillation circuit 31 and the common ground terminal 35.

On the other hand, the common light receiving element 3 is
a is connected via a power supply line 52 to a drive power supply terminal 51 disposed at a, and the ground side thereof is connected to the common ground line 36 via a flexible wiring board (not shown) or the like. I have. A noise filter 53 for absorbing or removing high-frequency components is also interposed in the power supply line 52 of the common light receiving element 3.

[0025] In the light source apparatus 10 of the optical head 1 of the present embodiment having such a configuration, the semiconductor laser 1 of the single mode oscillation
When reproducing the DVD by driving 1, the high-frequency oscillation circuit 31 is driven to superimpose the high-frequency current on the laser driving current. Thereby, the semiconductor laser 11 is made multi-mode. Here, the high-frequency oscillator 31 the feeding line 41 due to the high frequency current that could become a source of unwanted radiation generated by and the high-frequency oscillating circuit of the ground line 36, absorbs the high frequency component or Removable noise filters 41, 42 and 44 are connected. Also, a noise filter 53 is connected to a power supply line 52 of the common light receiving element 3 which is grounded to the ground line 36 of the high frequency oscillation circuit. Therefore, it is possible to prevent these wiring portions from generating unnecessary radiation.

In addition, in this embodiment, the semiconductor laser 1
A similar noise filter 43 is connected to the power supply line 39 of the multi-mode oscillation semiconductor laser 12 which is in a non-driving state at the time of driving 1. The power supply line 39 is
Since this portion is disposed close to the high-frequency oscillation circuit 31, there is a possibility that this portion becomes a source of unnecessary radiation.
It was confirmed that unnecessary radiation from 0 could be reliably prevented.

Furthermore, in addition to the effect of preventing unnecessary radiation, the arrangement of the noise filter 43 can prevent a surge current intruding from the outside via the power supply line 39, thereby preventing electrostatic breakdown of the semiconductor laser. The effect is also obtained.

Here, the noise filter 4 as means for preventing unnecessary radiation caused by high frequency oscillation of the high frequency oscillation circuit 31
Reference numerals 1 to 44 and 53 denote bandpass filters having characteristics capable of removing or absorbing superimposed high-frequency components. Instead of noise filters, other high-frequency component absorbing elements such as choke coils and ferrite beads are used. be able to. These high frequency component absorbing elements
It is sufficient that the impedance has a characteristic that the impedance in the low frequency region used for controlling the output of the semiconductor laser 12 is minimal and the impedance in the superimposed high frequency region is maximal.

The high frequency component absorbing circuit for preventing unnecessary radiation, which is connected to the power supply lines of the semiconductor lasers 11 and 12, adjusts the fundamental frequency of the superposed high frequency component in order to efficiently oscillate multimode laser light. It is desirable to have a characteristic of absorbing or removing the harmonic component and passing it as it is.

[0030]

As described above, in the light source device of the optical head according to the present invention, the high-frequency component absorbing circuit is also connected to the power supply line of the multi-mode semiconductor laser which is not driven when the single-mode semiconductor laser is driven. The adopted configuration is adopted. Therefore, even when the single-mode laser and the multi-mode laser are incorporated in a common package, generation of unnecessary radiation from the light source device due to high-frequency oscillation of the high-frequency oscillation circuit can be reliably prevented. Further, by inserting this high-frequency component absorbing circuit into a power supply line to a multi-mode semiconductor laser, a surge current which may enter from an external wiring can be prevented, so that it is also effective in preventing electrostatic breakdown of the semiconductor laser. .

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical head to which the present invention is applied.

FIG. 2 is a schematic wiring diagram showing power supply wiring to a light source device and a common light receiving element of the optical head of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical head 10 Light source device 10a Wiring board 11 Single mode oscillation semiconductor laser 12 Multimode oscillation semiconductor laser 13 Common package 2 Optical recording medium 2a Recording surface 3 Common light receiving element 3a Wiring board 4 Diffraction grating 5 Beam splitter 6 Collimating lens 7 Objective lens 20 Control device 21 Drive circuit 22 Objective lens drive mechanism 23 Laser drive control circuit 31 High frequency oscillation circuit 32, 33, 34, 35, 51 Terminal 36 Common ground line 37, 38, 39, 52 Feeding line 41, 42, 43 , 44, 53 Noise filter

Claims (4)

[Claims] 1. A common package, a semiconductor laser of single mode oscillation and a semiconductor laser of multi-mode oscillation contained in the package, and the semiconductor laser for converting the semiconductor laser of single mode oscillation to multi-mode oscillation. A light source device for an optical head having a high-frequency oscillation circuit for generating a high-frequency current to be superimposed on a driving current of the laser, the light source device having an unnecessary radiation prevention unit for preventing unnecessary radiation caused by the high-frequency current, A light source device for an optical head, comprising: a high-frequency component absorbing circuit interposed in a power supply line of the multi-mode oscillation semiconductor laser. 2. The light source device for an optical head according to claim 1, wherein the high-frequency component absorbing circuit is capable of absorbing at least a fundamental frequency component of the high-frequency current. 3. The light source device for an optical head according to claim 1, wherein the high-frequency component absorbing circuit is a band-pass filter, a choke coil, or a ferrite bead. 4. The semiconductor laser according to claim 1, 2 or 3, wherein the multi-mode oscillation semiconductor laser emits 780 nm laser light, and the single mode oscillation semiconductor laser emits 635 or 650 nm laser light. A light source device for an optical head.