Storage Technology Corporation

Krishna Swaminathan

Leonard Laub

Charles Reilly

Apparatus for reading information stored in a track pattern on a radiation reflecting record comprises a source of radiation such as a laser, a diffraction grating for providing at least a zero order beam component and a pair of first order beam components, an objective lens assembly, a photodetector array, the photodetector array comprising a unitary data photodetector disposed for impingement of the zero order beam component for sensing stored information and at least first and second paired photodetector arrays adjacent to the data photodetector including separated sectors disposed along an axis including the data photodetector for providing at least focus error correction signals to the objective lens assembly, and means provided in the optical path between the objective lens assembly and the photodetector array for providing a first portion of the reading beam components which remains relatively fixed in size and a second portion of the reading beam components which varies substantially linearly in size as the record deviates from a plane of focus.

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Santa Monica, CA, United States of America

Krishna Swaminathan