Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1992-12-29
1994-11-01
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
369 4423, G01J 120
Patent
active
053609700
ABSTRACT:
The radiation resulting from interaction with a data track or groove on a storage surface of an optical information storage and retrieval system is separated into three components and detected to provide tracking, focussing, and data signals. The separation is performed using a dual diffraction grating in a single optical path. The division between grating elements in the dual diffraction grating is oriented perpendicular to the data track or groove projected on the grating element. Diffraction radiation components generated by the dual diffraction grating are applied to a first and a second dual sensor elements. The first and second dual sensor elements provide a focusing signal. The undiffracted radiation component transmitted by the dual grating is applied to a third dual sensor. The division between sensors of the third dual senor is perpendicular to the division of the dual grating. Signals from the third dual sensor elements provide the tracking signal and the data signal. Several embodiments of the basic configuration are disclosed including a variety of configurations for defocusing the undiffracted transmitted radiation on the third dual sensor. In addition, a cylindrical lens can be used to defocus the radiation components from the diffraction grating in a single dimension.
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Eastman Kodak Company
Nelms David C.
Owens Raymond L.
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