Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Mechanism control by the control signal
Patent
1987-10-23
1989-04-18
Sikes, William L.
Dynamic information storage or retrieval
Control of storage or retrieval operation by a control...
Mechanism control by the control signal
369112, 350 9611, G11B 700
Patent
active
048233315
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a focusing detection apparatus for detecting a focusing state of an optical recording medium.
2. Background Art
A focusing error signal representing a focusing state of an optical recording medium requires zero-crossing point symmetry, linearity near the zero-crossing point, elimination of reproduced signal mixing, and the like.
Japanese Patent Disclosure (Kokai) No. 60-217535 discloses a focusing detection apparatus 10 shown in FIG. 1A as a focusing detection apparatus satisfying the above requirements.
In the focusing detection apparatus 10, a beam 12 output from a light source 11 such as a laser diode is transmitted through a beam splitter 13, a collimator lens 14, and an objective lens 15 and is incident on an optical recording medium 16 such as an optical disk. A beam is reflected by the optical recording medium 16, is transmitted through the objective lens 15 and the collimator lens 14, and is reflected by the beam splitter 13. A beam 17 from the beam splitter 13 is split into first and second beams 22 and 23 by a beam splitter 21. A first photosensor 24 is spaced apart from the optical recording medium 16 by a distance longer than that between the optical recording medium 16 and a convergent point of the first beam 22. A second photosensor 25 is spaced apart from the optical recording medium 16 by a distance shorter than that between the optical recording medium 16 and a convergent point of the second beam 23. As shown in FIGS. 1B and 1C, a sum of detection signals from end photosensor elements 24a and 24c of the first photosensor 24 and a central photosensor element 25b of the second photosensor 25 is compared with a sum of detection signals from a central photosensor element 24b of the first photosensor 24 and end photosensor elements 25a and 25c of the second photosensor 25 to obtain a focusing error signal.
DISCLOSURE OF INVENTION
In such a focusing detection apparatus 10, the two beam splitters 13 and 21 are used. In addition, the light source 11, the beam splitters 13 and 21, and the photosensors 24 and 25 are independently arranged to complicate assembly, thus resulting in a bulky, expensive apparatus.
In order to solve the above problem, a focusing detection apparatus according to the present invention comprises a semiconductor laser fixed on a semiconductor substrate, a prism fixed on the semiconductor substrate, a first semi-transmissible reflecting surface formed on a prism surface opposite to the semiconductor laser, a second semi-transmissible reflecting surface constituted by a prism surface in contact with the semiconductor substrate and formed at a position where a beam passing through the first semi-transmissible reflecting surface is incident, a first photosensor including three photosensor elements formed on the semiconductor substrate at a position in contact with the first semi-transmissible reflecting surface and aligned in a predetermined direction, and a second photosensor including three photosensor elements aligned in a predetermined direction and formed on the semiconductor substrate at a position where the beam reflected by the second semi-transmissible reflecting surface is incident, wherein the optical recording medium is irradiated with the beam emitted from the semiconductor laser and reflected by the first semi-transmissible reflecting surface, a beam from the optical recording medium passed through the first semi-transmissible reflecting surface is converged after the beam is reflected by the second semi-transmissible reflecting surface but before the beam is incident on the second photosensor, and a sum of detection signals from end photosensor elements of the three photosensor elements of the first photosensor and a central photosensor element of the three photosensor elements of the second photosensor is compared with that from a central photosensor element of the three photosensor elements of the first photosensor and end photosensor elements of the three photosensor elements of the second photo
REFERENCES:
patent: 4468084 (1984-08-01), Hutcheson et al.
patent: 4542492 (1985-09-01), Leterme et al.
patent: 4654519 (1987-03-01), Ando
patent: 4672187 (1987-06-01), Fujita et al.
patent: 4716559 (1987-12-01), Hine
patent: 4718052 (1988-01-01), Kondo et al.
patent: 4720824 (1988-01-01), Hayashi
patent: 4725725 (1988-02-01), Ando
patent: 4737946 (1988-04-01), Yamashita et al.
patent: 4747090 (1988-05-01), Yamashita et al.
Ura et al., Electronics and Communications in Japan, Part 2, vol. 70, No. 2, 1987, "An Integrated-Optic Disk Pickup Device," pp. 92-100.
Kume Hidehiro
Matsumoto Yoshiyuki
Yoshitoshi You
Gonzalez Frank
Sikes William L.
Sony Corporation
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