JPS59129948A - Optical information processing device - Google Patents

Abstract

PURPOSE:To maintain a noise of a reproducing time at a low level by photodetecting at least a part of semiconductor laser light, and positively feeding back an output of its photodetecting means to a control means of a semiconductor laser device. CONSTITUTION:A positive feedback circuit is constituted of a monitor photodetector 12, capacitors 7, 8 and a positive feedback amplifier 9. In this way, a semiconductor laser 1 is photodetected by the detector 12, only a high frequency variation portion of laser light is amplified from an output of this detector 12, and returned to a laser driving current, and by executing said operation, a high frequency oscillation is executed. As a result, the semiconductor laser 1 generates an oscillation of a vertical mode. The capacitors 7, 8 or a filter 14 fulfills a function of a filter circuit so that a component of a necessary band is not fed back positively. Accordingly, a frequency component which is much higher than a signal band is fed back positively, and a laser oscillation is converted to a multi-mode.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an information processing apparatus that uses a semiconductor laser device as a light source to illuminate and reproduce an information surface.

[Prior art]

Conventionally, in information processing devices using semiconductor laser devices, a problem has been that when reflected light from an optical component or an information surface, such as a disk plate, returns to the laser resonator, the laser resonance state is disturbed and noise is generated. It becomes. Information processing devices include optical disk devices, such as video
There are disk devices, audio disk devices, memory file devices, and the like.

In particular, when a single mode semiconductor laser device is used as a light source, the reflectance of the resonator end face is low, so coupling with the outside is strong and it is easily affected by reflected light. Another problem is noise when the wavelength jumps to a longer wavelength due to a rise in temperature.

To avoid this effect, a multi-mode oscillation laser is a candidate, but as mentioned above, it is less susceptible to the effects of reflected light and temperature, but the base level of noise is high, and when the noise of a single-mode laser is low, the S /N has the problem of being bad.

Furthermore, it is difficult to make a stable multi-mode oscillation laser from a manufacturing standpoint.

OBJECTS OF THE INVENTION The present invention provides an optical information device that has a low noise level during information reproduction and is stable against changes in reflected light and ambient temperature.

[Summary of the invention]

In order to achieve the above purpose, the following structure is adopted.

In an optical information processing device that irradiates and reproduces an information surface with semiconductor laser light, at least a portion of the semiconductor laser light is optically detected, and the output of the optical detection means is positively fed back to the control means of the semiconductor laser device. be.

Among the frequency components of the output of the photodetecting means, it is preferable that the components outside the required signal band be used as positive feedback.

Further, it is usually preferable to amplify the output of the photodetecting means upon positive feedback.

[Embodiments of the invention]

FIG. 1 is a top view of one embodiment of the present invention. In the figure, 21 is a disk on which information is recorded in a spiral shape, 22 is the center, 23 is a track on which information is recorded, 24 is a housing in which a semiconductor laser, a lens, etc. are arranged, and 25 is a housing. motors 26 and 27 for moving the disk 3;
and an arrow indicating the direction of movement of the housing.

FIG. 2 is a partially enlarged explanatory diagram of the information reproducing section of the present optical information processing apparatus.

1 is a semiconductor laser, 2.3 is a lens, and 21 is a disk plate. 4 is a polarizing prism, 5 is a single plate, and 6 is a photodetector. Information from the disk plate 21 is obtained by irradiating the tracks of the disk plate 21 with laser light emitted from a semiconductor laser, and using the reflected light to read a large number of information using an isolator composed of a polarizing prism 4 and a plate 5. The light is read by guiding the light to the light emitting device 6.

When reading this information, a portion of the laser light returns to the semiconductor laser again, producing noise.

To counter this problem, the present invention makes it possible to maintain the noise level of the optical information processing device at a low level by providing the following positive feedback circuit.

This positive feedback circuit includes a monitor photodetector 12, a capacitor 7.
8 and a positive feedback amplifier 9. In addition, 13 is DC
A power supply (temperature-controlled constant output DC power supply), 11 is a choke that passes only the l)C portion of the monitor output, and 10 is a choke that prevents high frequency components from entering the DC power supply 13.

In some cases, as shown in FIG.
A high-pass filter 14 may be inserted between the positive feedback amplifier 9 and the positive feedback amplifier 9. FIG. 3 shows only the positive feedback circuit portion as an equivalent circuit.

In this way, the semiconductor laser is received by the light receiver, and only the high frequency fluctuation of the output of the light receiver is amplified and returned to the laser drive current, thereby causing high frequency oscillation.

As a result, longitudinal multimode oscillation occurs in the semiconductor laser.

A specific example of the configuration is as follows. High pass filter 1
The cutoff frequency of the amplifier 9 is 400 MHz, and the gain is 40 dB.The semiconductor laser 1 used is an AI!GaAs-based visible laser with a double heterostructure, and the main drive If this method is not used, basically the longitudinal mode oscillates in a single mode.A silicon photodiode is used as the photodetector 12.The circuit shown by 15 is the main component of the present invention, and this The configuration with the exception of 1 is almost the same as the conventional semiconductor laser drive system.

FIG. 4 is a diagram showing a comparison of 1 is level to show the effect of applying the present invention. Curve 16 is when the present invention is not applied, curve 17 is when the conventional multi-mode laser is used,
18 is an example of application of the present invention. The horizontal axis indicates the amount of feedback of the laser beam.

In this way, it can be seen that when positive feedback modulation is performed, the noise level 18 is reduced by more than an order of magnitude compared to 16 when it is not performed. This level is also lower than the noise level 17 obtained with a conventional multimode laser. .

The capacitor 7.8 or the filter 14 serves as a filter circuit to prevent components in the necessary signal band from being fed back positively. Therefore, the frequency components much higher than the signal band are positively fed back, and as shown in FIG.
2 is arranged in the same direction as the exit side of the laser beam that irradiates the disk plate 3. In this case as well, as in the case of Figure 2, etc.
Shows the same effect. Note that in FIG. 5, the same reference numerals as in FIG. 2 indicate the same parts. Furthermore, a method of using a half prism as an isolator is also effective.

It goes without saying that the present invention can be applied to a reproducing apparatus that uses a method of reproducing information such as applying a laser beam to the information surface and reading the transmitted light, or reading the reflected light. do not have.

By incorporating such a drive circuit into the same package, it is possible to use it in the same way as a conventional semiconductor laser. Furthermore, if an integrated circuit is created by integrating these on the same chip, it will be advantageous in terms of stability and cost.

In this method, it is sufficient that the optical output fluctuates at a frequency higher than the frequency band used in the system. Therefore, depending on the frequency used in the system, it is possible to use an amplifier with a narrower frequency band than the amplifier shown in the above embodiment.

In addition, near the natural vibration frequency of the semiconductor laser (2 to 3 GH
It will be more effective if return is performed using z).

The present invention is of course applicable not only to the At Ga AB type semiconductor laser shown in the embodiment, but also to other type semiconductor lasers, such as the InP-InGaAsP type semiconductor laser using a ■-V group compound semiconductor.

〔Effect of the invention〕

As explained above, according to the present invention, noise during reproduction in an optical information processing device can be maintained at a low level. That is, the noise does not particularly increase even when the laser beam is returned to the semiconductor laser or when there is a change in the ambient temperature.

[Brief explanation of the drawing]

FIG. 1 is a top view showing an example of an optical information processing device according to the present invention, FIGS. The figure shows a comparison of noise. 3: Disk plate, 1: Semiconductor laser, 12: Photoreceiver, 1
4: Filter, 9: Amplifier, 13: DC power supply. Agent Patent Attorney Akira Takahashi f5) Figure 1 Figure r2

Claims (1)

[Scope of Claims] (1) In an optical information processing device that irradiates and reproduces an information surface with semiconductor laser light, a means for optically detecting at least a part of the semiconductor laser light; An optical information processing device comprising at least means for providing positive feedback to a control means. 2. The optical information processing apparatus according to claim 1, further comprising means for providing positive feedback to components outside the required signal band among the frequency components of the output of the optical detection means.