JPH04330646A - Laser output controller for optical information recording/reproducing device - Google Patents

Abstract

PURPOSE:To provide the laser output controller of an optical information recording/reproducing device which detects forwardly emitted light from a semiconductor laser chip and which is used for the prescribed control of laser output. CONSTITUTION:The laser output controller of the optical information recording/ reproducing device which records and reproduces information for a optical information recording medium and from it by using the output light of a semiconductor laser is provided with a light-receiving element 19 which light-receives peripheral light 5 in the forwardly emitted light from the semiconductor laser chip 1 in the semiconductor laser and the controller output-controls the semiconductor laser in accordance with the output of the light-receiving element.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser output control device for an optical information recording/reproducing apparatus for recording information on an optical information recording medium and reproducing information from the same. It relates to a device to be controlled.

0002

2. Description of the Related Art The output of a semiconductor laser fluctuates due to temperature changes or changes in the amount of returned light. On the other hand, optical information recording and reproducing devices require automatic output control (AP
C) is being carried out.

For example, in the optical information recording and reproducing apparatus shown in FIG. The light is then converted into a parallel light beam and enters the beam splitter 4. The beam splitter 4 separates the transmitted light 6 and reflected light 7, and the transmitted light 6 is focused by a focusing lens 8 and enters an information recording medium 9.
It is irradiated as a minute laser beam spot 10, and information is recorded or reproduced.

The reflected light from the information recording medium 9 travels back along the same path as when it was incident, is converted into a parallel light beam by the focusing lens 8, and the light transmitted through the beam splitter 4 is returned to the semiconductor laser chip 1. becomes. The reflected light 11 from the beam splitter 4 passes through the light receiving lens 12 and is received by the light receiving element 13 . In this way, the information signal from the light receiving element 13,
A focus control signal and a tracking control signal are extracted. In the APC operation, a part of the optical output of the semiconductor laser is detected by the monitor light receiving element 14 or 15, and a loop circuit is provided to amplify this detection output and feed it back to the semiconductor laser, so that the output of the laser beam is kept constant. The output is controlled so that

The monitor light receiving element 14 receives the backward emitted light 16 from the semiconductor laser chip 1 and outputs a signal 17, and the monitor light receiving element 15 receives the reflected light 7 of the beam splitter 4 and outputs a signal 18. It is configured so that

[0006]

[Problems to be Solved by the Invention] In this configuration, a monitor light-receiving element 14 that is built in a general semiconductor laser chip 1 is used, and the rear emitted light of the semiconductor laser chip 1 is extracted by this monitor light-receiving element 14. ing. However, since there is no perfect correlation between the forward emitted light and the backward emitted light of the semiconductor laser chip, there is a problem that the laser light output cannot be controlled at a constant level, and good APC operation cannot be performed.

Furthermore, since the monitor light-receiving element 15 receives the light from the beam splitter 4, it is forced to adopt a configuration that depends on the characteristics of the beam splitter 4. For example, in order to reduce the loss of transmitted light in the beam splitter 4 and improve the optical efficiency of the optical system, the beam splitter 4
If a polarizing beam splitter is used as a polarizing beam splitter, there is a problem that the reflected light 7 no longer exists because a quarter-wave plate is usually combined to form an optical isolator configuration, and a feedback signal cannot be obtained.

The present invention has been made in consideration of the above points, and provides a laser output control device for an optical information recording/reproducing device, which detects forward emitted light from a semiconductor laser chip and uses it to control constant laser output. The purpose is to provide

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an optical information recording and reproducing apparatus that records information on an optical information recording medium and reproduces information from the medium using output light of a semiconductor laser. In the laser output control device, the semiconductor laser is provided with a light-receiving element that receives ambient light in the forward emitted light from the semiconductor chip, and the output of the semiconductor laser is controlled according to the output of the light-receiving element. The present invention provides a laser output control device for an optical information recording/reproducing device characterized by the following features.

0010

[Operation] Of the light emitted from the semiconductor chip, the central light of the forward emitted light is incident on the collimator lens, the peripheral light is incident on the light receiving element, and a signal corresponding to the emitted light output from the semiconductor chip is output. This signal is given to the output control circuit of the semiconductor laser via the feedback circuit, so that if there is a fluctuation in the output from the semiconductor laser, the output is controlled accordingly.

[0011]

[Effects of the Invention] As described above, the present invention uses a light receiving element to extract a signal corresponding to the ambient light in the forward emitted light of the semiconductor laser chip and returns it to the semiconductor laser output control circuit to control the output. Therefore, there is no possibility of feedback control lacking correlation as in the case of conventional backward emitted light, and there is an effect that any type of beam splitter can be used as the beam splitter. Therefore, it is possible to realize a device that performs APC operation of a semiconductor laser well and efficiently.

0012

Embodiment FIG. 1 shows an embodiment of the present invention. In this figure, the same reference numerals as in FIG. 5 indicate the same elements. In the optical configuration of this embodiment, the light 4 near the center of the forward emitted light from the semiconductor laser chip 1 enters the collimator lens 3, becomes a parallel light beam, and enters the beam splitter 4. Beam splitter 4 may be a polarizing beam splitter. The contents of the operation from this point on are similar to those described with reference to FIG. 5, and an information signal, a focus control signal, and a tracking control signal are extracted from the light receiving element 13.

The characteristic configuration of the present invention is that the monitor light receiving element 19 is arranged closer to the semiconductor laser chip 1 than the collimator lens 3, and the output of this monitor light receiving element 19 is sent to the output control circuit 20 of the semiconductor laser. It is to return home. That is, in FIG. 1, of the forward emitted light from the semiconductor laser chip 1, near-center light 2 is incident on the collimator lens 3, and peripheral light 5 is incident on the monitor light receiving element 19. In this case, the rate at which the near-center light 2 enters the collimator lens 3 is determined, for example, by setting the NA (numerical aperture) of the collimator lens 3 to 0.0, which is often used in optical systems for recording and reproducing information.
If you select 3, it will be about 60% of the forward emitted light output of the semiconductor laser.
The remaining approximately 40% of the laser light output is included in the ambient light.

The monitor light receiving element 19 may have any shape as long as it can receive all or part of the peripheral light 5 of the forward emitted light from the semiconductor laser chip 1. For example, a donut-shaped element 19-1 as shown in FIG. 2(a)
or a square or rectangular element 19-2 with a hole in the center as shown in Figure 2(b), or an element divided into multiple pieces as shown in Figure 2(c) or (d). 19-3 or 19-4.

FIG. 3 shows another embodiment of the invention,
A mirror 21 is arranged at the position of the monitor light receiving element 19 in the above embodiment, and the element 22 is configured to receive the reflected light from the mirror 21. In this case, the shape of the mirror 21 and the light receiving element 22 is as shown in the element 19 shown in FIG.
-1 to 19-4 are applicable.

FIG. 4 shows still another embodiment of the present invention, in which a concave mirror is used as the mirror 21 in addition to a plane mirror. If a concave mirror is used, the reflected light from the mirror 21 can be focused on one point, so the light receiving element 22 can be miniaturized. Therefore, the capacitance between the electrodes of the light receiving element 22 can be reduced and the response speed can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an optical system in an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of a monitor light-receiving element in the embodiment of FIG. 1;

FIG. 3 is a diagram showing the main part configuration of an optical system in another embodiment of the present invention.

FIG. 4 is a diagram showing a main part configuration of an optical system in still another embodiment of the present invention.

FIG. 5 is a diagram showing the configuration of an optical system in a conventional optical information recording/reproducing device.

[Explanation of symbols]

1 Semiconductor laser chip 2 Light near the center of forward radiation light 3 Collimator lens 4 Beam splitter 5 Ambient light of forward radiation 6 Transmitted light 7 Reflected light 8. Focusing lens 9 Information recording medium 10 Microscopic laser light spot 11 Reflected light 12 Light receiving lens 13 Photo receiving element 14 Monitor light receiving element 15 Monitor light receiving element 16 Backward synchrotron radiation 17 Signal 18 Signal 19 Photo receiving element 20 Output control circuit 21 Mirror 22 Photo receiving element

Claims (3)

[Claims] 1. A laser output control device for an optical information recording/reproducing apparatus that records information on an optical information recording medium and reproduces information from the medium using output light of a semiconductor laser, wherein: A laser output control device for an optical information recording/reproducing device, comprising a light receiving element that receives ambient light in forward emitted light, and controlling the output of the semiconductor laser according to the output of the light receiving element. . 2. A laser output control device for an optical information recording/reproducing apparatus according to claim 1, wherein the light receiving element receives ambient light in the diffused light from the semiconductor chip. 3. A laser output control device for an optical information recording/reproducing device according to claim 1, further comprising means for reflecting diffused light from the semiconductor chip toward the light receiving element.