Autofocus system

Details Autofocus system Autofocus system

1988-11-18

1991-01-08

McElheny, Jr., Donald

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369121, G11B 700

Patent

active

049842293

ABSTRACT:
Autofocus apparatus for use in an optical system utilizing a recording medium formed from a birefringent medium and a radiation-sensitive medium. The autofocus apparatus automatically focuses radiation through the birefringent medium and substantially at the interface between the birefringent medium and the radiation-sensitive medium and includes a source of linearly polarized radiation, a quarter-wave plate to convert the linearly polarized radiation to circularly polarized radiation, and an actuator controlled lens for focusing the radiation onto the recording medium, whereby radiation reflected from the first surface of the birefringent medium and the interface between the birefringent medium and the radiation-sensitive medium passes back through the lens and quarter-wave plate and is deflected by a beamsplitter to a polarization detector. The polarization detector isolates polarization components which arise from reflection at the interface and the isolated polarization components impinge upon a detector. The detector provides a focus-error signal which is applied, in turn, to the actuator to maintain focus.

REFERENCES:
patent: 4873678 (1989-10-01), Nakamura et al.
patent: 4918675 (1990-04-01), Lee

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