Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2006-05-04
2008-11-11
Luu, Thanh X (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S231130
Reexamination Certificate
active
07449678
ABSTRACT:
A photodetector group includes a plurality of photodetector elements which are arranged one-dimensionally in a direction of movement of a scale. An optical encoder includes a differential signal calculating member which calculates a first differential signal of an output signal from one photodetector element and an output signal from other photodetector element, and a gate signal forming member which generates a gate signal which includes an area of zero crossing by the first differential signal, near a position where light emitted from a light source is incident on the photodetector group upon passing through a reference position pattern formed on a scale. The optical encoder outputs a reference position signal based on a point of zero crossing of the first differential signal and the gate signal.
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Luu Thanh X
Olympus Corporation
Scully , Scott, Murphy & Presser, P.C.
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