Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1995-07-28
1996-07-30
Ben, Loha
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369110, 369 4423, G11B 700
Patent
active
055419062
ABSTRACT:
An optical head for reading and/or writing information from and/or from a magneto-optical record medium including a semiconductor laser, a composite prism having a glass prism, a birefringent prism and a dielectric multilayer film interposed between the glass prism and birefringent prism, an objective lens and fist and second photodetectors. A laser beam emitted by the semiconductor laser impinging upon the glass prims is reflected by the dielectric film and is projected onto the record medium by the objective lens. A return beam reflected by the record medium is incident upon the dielectric film via the objective lens, and a part of the return beam transmitted through the dielectric film is separated by the birefringent prism into a first ordinary beam and a second extraordinary beam which are received by the first and second photodectors, respectively. The glass prism and birefringent prism are made of materials which satisfy a condition that a difference between refractive indices of the birefringent prism for ordinary light and extraordinary light is not less than 0.03 and a difference between a refractive index of the glass prism and at least one of the refractive indices of the birefringent prism is not less than 0.15.
REFERENCES:
patent: 4771414 (1988-09-01), Yoshimatsu
patent: 5077723 (1991-12-01), Yoshimatsu
patent: 5189655 (1993-02-01), Ogata et al.
patent: 5272685 (1993-12-01), Ando
patent: 5293371 (1994-03-01), Koyama
patent: 5293569 (1994-03-01), Koyama
Ose, et al, "Optical Engineering Handbook", pp. 306-328, 1988.
Ben Loha
Olympus Optical Co,. Ltd.
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