Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Reexamination Certificate
1998-05-20
2001-02-06
Pham, Hoa Q. (Department: 2877)
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
C369S044230, C369S044120
Reexamination Certificate
active
06184512
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a semiconductor laser apparatus used as a laser source of an optical pickup apparatus which records/reproduces information on an optical recording medium. More specifically, it relates to a semiconductor laser apparatus which feedback-controls the amount of light from a semiconductor laser.
b) Description of the Related Art
The amount of laser beam light (determined by the intensity of the laser beam light) emitted from a semiconductor laser largely varies depending on temperature and a change in time. Therefore, it is a common practice to feedback-control the amount of light from the semiconductor laser for obtaining a constant amount of light from the semiconductor laser. For example, in a semiconductor laser described in Tokkai H4-349687, a step is formed on the surface of a semiconductor substrate wherein a semiconductor laser is placed at the lower surface of the step and an optical detector for monitoring is formed on the side wall of the step. As a result, the semiconductor laser and the optical detector for monitoring are placed opposite from each other while an optical detector for detecting signals is formed at a location other than the side wall of the step.
Nonetheless, in the above semiconductor laser apparatus of Tokkai H4-349687, the configuration is such that the semiconductor laser and the optical detector for monitoring are placed opposite from each other by using a step formed on the semiconductor substrate. Therefore, a drawback exists in that the optical detector for monitoring cannot be formed on a semiconductor substrate having a flat surface; in turn, it is difficult to form the optical detector for detecting signals and the optical detector for monitoring on the same surface. As a result, the two optical detectors are formed in separate processes such that costs for manufacturing the semiconductor laser apparatus are dramatically increased.
If a light receiving plane of the optical detector for monitoring is formed on a semiconductor having a flat surface, on the other hand, only a small part of a laser beam emitted from the semiconductor laser reaches the light receiving plane; as a result, precision in detection of light beams deteriorates.
OBJECT AND SUMMARY OF THE INVENTION
Therefore, a primary object of the present invention is to provide a semiconductor laser apparatus in which a laser beam, emitted from a semiconductor laser horizontally in relation to a surface of a semiconductor substrate, can be effectively received in spite of an optical detector for monitoring having its light receiving plane on a flat surface of the substrate and to provide an optical pickup apparatus using the same.
In accordance with the invention, a semiconductor laser apparatus comprises a semiconductor substrate, a semiconductor laser which is fixed on the semiconductor substrate and a prism having a slanted plane. The prism is placed such that its slanted plane faces a side across from the semiconductor laser. The apparatus also includes an optical detector for monitoring which is formed on the surface of the semiconductor substrate. The surface is covered by the prism. The following are formed on the slanted plane of the prism: a reflection region on which the surface is processed for reflecting a part of an emitted light beam from the semiconductor laser and a transmissive refraction region on which the surface is processed such that the remaining part of the emitted light beam is transmitted and refracted to be guided to a light receiving plane of the optical detector for monitoring.
REFERENCES:
patent: 5005162 (1991-04-01), Mitsumori et al.
patent: 5396061 (1995-03-01), Taniguchi et al.
patent: 5727111 (1998-03-01), Kume et al.
patent: 5804814 (1998-09-01), Musha et al.
patent: 5814807 (1998-09-01), Musha et al.
patent: 4-349687 (1992-12-01), None
Hayashi Yoshio
Higashiura Kazuo
Takeda Tadashi
Pham Hoa Q.
Reed Smith Shaw & McClay LLP
Sankyo Seiki Mfg. Co. Ltd.
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