Optical head and information recording apparatus

Details Optical head and information recording apparatus Optical head and information recording apparatus

1992-04-08

1994-11-01

Young, W. R.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4412, 369 4426, 369 4434, 369 4435, G11B 700

Patent

active

053612442

ABSTRACT:
Disclosed herein is a compact, adjustment-free, unitary optical head wherein diffraction grating made of a birefrigence material and having convexities and concavities of grating grooves so set that the difference of their optical path lengths is some multiples and a half of the wavelength for an ordinary beam and an extraordinary beam, a diffraction grating providing astigmatisms to .+-.1 order beams, a quarter wavelength plate, and other optical components, are interposed between a semiconductor laser and a focussing lens and are stored inside an optical head body filled with a dry nitrogen gas. A focus error detection signal is obtained from the difference of the degrees of modulation of the .+-.1 order reflected beams by pre-wobbled pits, and adjustment of the optical beam can be carried out by driving the body by a two-directional head actuator.

REFERENCES:
patent: 4689479 (1987-08-01), Tatsuno et al.
patent: 4978844 (1990-12-01), Ujihara
patent: 5050155 (1991-09-01), Kurata et al.
patent: 5062098 (1991-10-01), Hori et al.
patent: 5095472 (1992-03-01), Uchino et al.
patent: 5132948 (1992-07-01), Ishibashi
patent: 5161148 (1992-11-01), Hori et al.

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