JPS62298034A - Optical head - Google Patents

Abstract

PURPOSE:To exactly measure a value of a laser light output by placing a laser light output measuring part on an optical path of a laser, except an optical path of a light beam which is reflected from an optical recording medium, in an optical head. CONSTITUTION:A laser light 2 which has been emitted from a laser light source 1 is sharped by a laser light shaping prism 3 and made incident on an optical recording medium. Also, a laser light output measuring photodiode 5 is fixed onto an optical path of a light beam 4 which has been reflected by the surface of the prism 3. A return light 6 from the optical recording medium is not made incident on the laser light output measuring photodiode 5. In this way, a return light component from the optical recording medium is not contained at all in a measured value outputted from the diode 5, therefore, the value having extremely high value is obtained, and this optical head can cope with the optical recording medium whose reflection factor is different, as well.

Description

[Detailed description of the invention] 3. Detailed description of the invention (Industrial application field) The present invention relates to an optical head used for an optical recording medium.

(Prior Art) The optical recording method is a recording method in an optical disk memory. Optical disk memory is considered to be a new memory that can replace the current magnetic disk memory because it is capable of high-density, large-capacity, and high-speed 7° access, and is attracting the most attention. The conventionally known optical head is as shown in Figure 3.
It includes at least a laser light source 1 and a laser beam shaping prism 3. The semiconductor laser used as the laser light source has the disadvantage that the output of the laser light 2 constantly fluctuates because it is easily influenced by the temperature and the temperature of the semiconductor laser. Further, even when the return light from the laser light source enters the laser light source, the laser light output is amplified due to the influence of the return light, and thus the laser light output fluctuates. However, in the optical recording system, changes in the laser light output of the optical head are a factor that greatly affects the recording, playback, and erasure characteristics of the optical recording medium, so in order to perform good recording, playback, and erasure, the laser light output must be It is necessary to eliminate fluctuations and control the laser light output with high precision.To do this, the laser light output must be controlled accurately at all times! Based on the measured value, it is necessary to supply appropriate power to the laser light source. A conventionally known method for measuring laser light output is to obtain a laser light output value from the output value of a photodiode built into a laser light source.

(Problems to be Solved by the Invention) However, it is inevitable that the return light from the optical recording medium will reach the laser light source. In addition, since the reflectance of optical recording media varies depending on the medium, the amount of returned light is not constant.For this reason, the conventional method of measuring laser light output includes even the returned light. could not be measured.

The present invention eliminates these conventional drawbacks, and provides a compact optical head that can control laser light output with high precision and is compatible with optical recording media having widely different reflectances. It's about doing.

(Means for Solving the Problems) According to the present invention, in an optical head that includes at least a laser light source and a laser beam shaping section that shapes the laser beam, a light path other than the optical path of the return light reflected from the optical recording medium is provided. In addition, the laser light output measuring section is arranged on the optical path of the laser light emitted from the laser light source.

(Function) The present invention solves the problems of the prior art by adopting the above-described configuration. The measured value output from the laser light output measuring section is a highly accurate value because it does not at all obscure the components of the return light reflected from the optical recording medium, and it is also a value that is highly accurate even when optical recording media with different reflectances are used. Not affected at all by By inputting the measurement value output from the laser light output measuring section to the auto power control circuit of the laser light source, it is possible to control the laser light output with high precision, and the reflectance is large. It can also be used with different optical recording media.

(Example) Examples of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a partial configuration diagram of a head showing an embodiment of the present invention. The laser beam 2 emitted from the laser beam rA1 is shaped by a laser beam shaping prism 3 and then enters the optical recording medium.

A photodiode 5 for measuring laser light output is fixed on the optical path of the light 4 from which the laser light 2 is reflected by the surface of the laser light shaping prism 3. The return light 6 from the optical recording medium passes through the light shaping prism 3 and returns to the laser light source 1, but never enters the laser light output measuring photodiode 5.

FIG. 2 is a partial configuration diagram of a head showing an embodiment of the pond of the present invention. A laser beam 2 emitted from a laser light source 1 is shaped by laser beam shaping prisms 3 and 7 and is incident on an optical recording medium. Laser light output measurement photodiodes 1 to 5 are fixed on the optical path of the light 4 that is reflected by the laser light 2 and reflected by the surface of the laser light shaping prism 3.

The return light 6 from the optical recording medium passes through the light shaping prism 3 and returns to the laser light source 1, but never enters the laser light output measuring photodiode 5.

Further, the laser beam 2 is transmitted through a laser beam shaping prism 7.
A photodiode 9 for measuring laser light output is fixed on the optical path of the light 8 reflected by the surface of the laser beam.

The return light 6 from the optical recording medium passes through the light shaping prism 7 and returns to the laser light source 1, but never enters the laser light output measuring photodiode 9.

(Effect of the invention) In the conventional optical head having the configuration shown in FIG. 3, it is not possible to accurately measure the value of the laser light output due to the return light to the laser, but by using the optical head of the present invention, the value of the laser light output can be measured. Values can be measured accurately.゛

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1.2 is a schematic diagram showing an embodiment of the optical head of the present invention, and FIG. 3 is a schematic diagram of a portion of a conventional optical head 1. In the figure, 1...-racer light source, 2. Laser light, 3
, 7... Laser beam shaping prism, tl, 8-- Light reflected from the laser beam by the surface of the laser beam shaping prism, 5.9... Photodiode for laser beam output measurement, 6... Return from optical recording medium')ゝ・

Susumu Ueban, patent attorney representing C:, -1 -2' O 1 Fig. O 2 Fig.'; + 3 Fig.

Claims (2)

[Claims] (1) In an optical head that includes at least a laser light source and a laser beam shaping section, the laser light output measuring section is arranged outside the optical path of the reflected light from the optical recording medium and on the optical path of the laser beam emitted from the laser light source. An optical head characterized by: (2) The optical head according to claim 1, wherein the laser beam output measuring section is arranged on the optical path of the light reflected by the laser beam shaping section.