Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1992-12-29
1994-10-04
Dzierzynski, Paul M.
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369 4423, 369112, 2502015, G11B 700
Patent
active
053532724
ABSTRACT:
In a sensor system for use in the read/write head of an optical information storage and retrieval system, a dual prism separates the resulting radiation beam into two radiation components, the radiation components having a division perpendicular to a projection of a data track or groove on the storage medium projected on the dual prism. Each of the two radiation components is focused by a focus sensor lens on one of two four-quadrant sensors, the four-quadrant sensors forming the system sensor array. The application of the two radiation components generates a tracking signal, a focusing error signal, and a data signal. The orientation of the dual prism results in reduced cross-talk between the tracking signal, which is derived from positive and negative diffraction components, and the focusing signal, which is derived from radiation components having contributions from both the positive and negative diffraction components. The optical components are selected to provide an astigmatism in the radiation components to minimize abrupt changes in the sensor response. For example, a cylindrical lens can be added in the optical path near the focus sensor lens to defocus the return radiation components in a direction perpendicular to a projection of the data track on the sensor array.
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Gage Edward C.
Kay David B.
Dzierzynski Paul M.
Eastman Kodak Company
Nguyen Kiet T.
Owens Raymond L.
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