JP2555538B2 - Optical information recording method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus used as a semiconductor laser light source, and more particularly to an optical information recording / reproducing apparatus capable of stabilizing the output of a semiconductor laser which is a light source.

[0002]

2. Description of the Related Art Conventionally, as a method for stabilizing the output of a semiconductor laser, one of the light beams emitted from the two wall-opened surfaces of the semiconductor laser is used as a light beam for a light source and the other is used as a light beam for stabilizing the output. The method of controlling the current of the laser drive power source by detecting the light flux of the laser beam with a photodetector and detecting the output fluctuation of the semiconductor laser is used. This method is disclosed in, for example, Japanese Patent Laid-Open No.
No. 0-81695 and JP-A No. 51-29821 are proposed.

[0003]

However, this stabilizing method has a problem in stabilizing the light flux for the light source because the light emitted from the laser end face is not necessarily the same on both end faces. In particular, optical information recording in which a light beam from a semiconductor laser is focused on a recording medium by an optical system, reflected light from the recording medium is separated from a light beam directed to the recording medium by a light separating element, and the reflected light is detected. In the reproducing device, the reflected light from the recording medium cannot be completely extracted by the light separation element,
Since a part of it is returned to the semiconductor laser, the amount of light emitted from the laser end face is different on both end faces due to the self-coupling effect of the semiconductor laser, and the above-described output stabilization method cannot be used. On the other hand, it is conceivable to provide a light separating optical element in the optical path for guiding the light flux from the semiconductor laser to the recording medium and take out a part of the light flux, but in this way a special optical element is provided for stabilizing the output. However, since the structure of the optical system that guides the light beam from the semiconductor laser to the recording medium becomes complicated and the intensity of the light beam toward the recording medium decreases, it is disadvantageous in terms of the life of the semiconductor laser. Particularly, in the optical information recording / reproducing apparatus like the present invention, it is necessary to move the relative position of the optical system for condensing the light flux from the semiconductor laser onto the recording medium at a high speed, and this optical system is as small as possible. It is important to be lightweight. Therefore, providing a special configuration only for stabilizing the output is extremely disadvantageous for high-speed access. Further, the output of the semiconductor laser is generally small, and in the optical information recording / reproducing apparatus, it is necessary to use the semiconductor laser near the rated output because high output is required at the time of recording. For this reason, it is extremely disadvantageous from the viewpoint of the life of the semiconductor laser to provide the light separating optical element only for stabilizing the output and impair the intensity of the light flux toward the recording medium. Optical separation optics only for such output stabilization
Regarding the problem of the technology for providing the element, see SAIKAI 53-1.
7174.

The present invention has been made in view of these points. A semiconductor laser is used as a light source, a light beam from the semiconductor laser is condensed on a recording medium by an optical system, and reflected light from the recording medium is reflected. A technique in which a light separating element separates a light beam directed toward a recording medium and extracts the reflected light from the recording medium by a photodetector, and a simple structure is used without using a special structure for stabilization. Can make the intensity of the light beam focused on the recording medium constant.
The purpose is to provide a method .

The present invention relating to an optical information recording method
Uses a semiconductor laser as the light source, and
The laser light is guided to the recording medium by an optical system and recorded as a light spot.
Convergent irradiation is performed on the recording medium, and the energy of the laser light is applied to the recording medium.
By giving it to the body, the recording medium is locally altered or altered.
Shape and record. In such technology, recording
The energy of light given to the recording medium during operation, that is,
The important issue is to control the output accurately to the desired value.
Becomes If the optical output during recording is lower than the specified value, record
You can't record in the right place, and the output during playback is too high.
For example, it may lead to the destruction of recorded data. Obey
In order to maintain the light output irradiated on the recording medium at the desired value.
In order to monitor the intensity of the light output actually radiated on the medium
However, it is necessary to control the light output according to the result.

[0006]

According to the present invention, in an optical information recording / reproducing apparatus, an optical element for separating the reflected light from the recording medium from the light beam directed to the recording medium and taking out the light beam other than the light beam directed to the recording medium. In view of the fact that there is a light beam extracted in a direction different from the reflected light from the recording medium, by detecting this light beam with a photodetector, an output proportional to the light beam directed to the recording medium is obtained, and the output of the semiconductor laser It controls the intensity of the luminous flux.

That is, the present invention uses a semiconductor laser such as an optical video disk or an optical data recorder as a light source and detects a light beam generated by reflection in an optical system for minutely condensing light from the semiconductor laser on a recording medium. The detection output stabilizes the output of the semiconductor laser.

A particularly characteristic part is that the light flux from the semiconductor laser is focused on the recording medium by the optical system, the reflected light from the recording medium is separated from the light flux directed to the recording medium by the light separating element, and the light is extracted. In an optical information recording / reproducing apparatus that detects reflected light, of the light flux traveling from the semiconductor laser to the recording medium, the light flux that is separated from the light flux irradiated on the recording medium by the light separation element originally provided in the optical system. By detecting this with a photodetector,
An output proportional to the intensity of the entire light flux toward the recording medium is obtained,
That is, the strength can be maintained accurately and stably. The light flux detected by this photodetector is the light flux originally lost in the optical information recording / reproducing apparatus, and is detected by the photodetector and fed back to the semiconductor laser. It is not necessary to provide a special optical element for stabilization.

[0009]

According to the present invention, since the light beam extracted from the light separating element originally possessed by the optical information recording / reproducing apparatus is used, it is not necessary to provide a special optical element for stabilizing the output, The light flux originally lost by the separation element does not impair the intensity of the light flux directed to the recording medium for stabilizing the output. Moreover, since the entire light flux directed to the recording medium is used, an output proportional to the intensity of the entire light flux directed to the recording medium can be obtained, and the intensity of the light flux irradiated on the recording medium can be more accurately stabilized. it can.

[0010]

Embodiments will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. The semiconductor laser 1 is oscillated by the laser drive power source 2, and a regular laser output is supplied to the front optical system. The condensing lens 3 condenses the laser light flux, and the light flux passes through the prism 4 galvanometer mirror 5 and is converged into a minute spot by the converging lens 6. The light flux incident on the recording medium 7 and reflected from the recording medium 7 is again reflected. Information is reproduced through the aperture lens 6 and the galvanometer mirror 5.

Thus, in the prism constituting the optical system, the light flux from the semiconductor laser 1 produces a reflected light flux 9 other than the light flux directed to the recording medium 7. Therefore, according to the present invention, the reflected light beam 9 from the prism 4 is received by the photodetector element 10,
The output is fed back to the laser drive power source 2 through the amplifier 11. FIG. 2 shows the inside of the laser drive power supply. In the comparator 21, the setting signal 22 corresponding to the laser output and the optical output signal (output of the amplifier 11) 23 are compared, and the output 24 of the comparator 21 is output. The output of the semiconductor laser is controlled so that the output of the comparator 21 becomes 0, that is, a constant light output.

FIG. 3 is a diagram showing another embodiment of the present invention. The same numbers as in FIG. 1 indicate the same elements. The feature of this embodiment is that a photodetector having two light receiving surfaces is used. The weakly reflected light beam 9 from the prism 4 is incident on one of the two light-receiving surfaces of the photodetection element 10 ', and a differential output of both light-receiving surfaces is generated by the differential amplifier 12 and fed back to the laser drive power source 2. According to the above, more precise output control is performed than in the above embodiment.
That is, since the differential outputs of both the light receiving surfaces are taken, 2
This is because the temperature drift components of the two light receiving elements cancel each other out, and only the fluctuation component of the optical output is fed back. Since the reflected light beam from the prism 4 is a divergent light beam, if the beam diameter is larger than the light receiving surface of the photodetection element 10 ', a convex lens is inserted after the prism 4 to form a convergent light beam, so that a light beam to one light receiving surface is obtained. Incident is possible. As described above, the present invention is intended to stabilize the output of the semiconductor laser by using the light flux created by the optical system, and therefore the stabilization of the output of the semiconductor laser is not required for the stabilization. Can be achieved.

[0014]

As described above, according to the present invention, it is not necessary to provide a special optical element for stabilizing the output, and the output of the semiconductor laser, which is the light source, is reduced without lowering the light utilization efficiency. Optical information record that can be kept constant
A method is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention.

FIG. 2 is a block diagram showing a main part.

FIG. 3 is a block diagram for explaining another embodiment of the present invention.

[Explanation of symbols]

 1 ... Semiconductor laser, 4 ... Optical separation element, 7 ... Recording medium.

Front page continuation (72) Inventor Takeshi Maeda 1-280, Higashi Koigokubo, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (56) Reference JP-A-52-67303 (JP, A) JP-A-51-29821 ( JP, A) JP 52-134705 (JP, A) SAIKAI 53-17174 (JP, U) Journal of the SM PTE Vol. 83 1974Julie P. 554-559

Claims (1)

(57) [Claims] 1. A semiconductor laser, a recording medium on which predetermined information is recorded, an optical system having means for condensing light traveling from the semiconductor laser toward the recording medium as a light spot on the recording medium, and the semiconductor. A light separating element that receives the light traveling from the laser toward the recording medium and the reflected light from the recording medium, and separates a part of each of the incident light ;
One of the reflected lights from the recording medium separated by the light separating element
An optical information recording method by a system having a signal reproducing detector for detecting a portion and a monitor detector for detecting a part of light traveling from the semiconductor laser to the recording medium separated by the light separating element. , The optical spot on the recording medium is output based on the detection signal of the monitor detector.
An optical information recording method for monitoring force and optically recording information on the recording medium while controlling the output of the semiconductor laser according to the monitoring result .