Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2006-04-25
2006-04-25
Pyo, Kevin (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S231180, C356S617000, C341S013000
Reexamination Certificate
active
07034283
ABSTRACT:
A position encoder uses a track encoded with a pattern of bit-widths in accordance with a sequence. The sequence may be any sequence having unique subsequences, and may be a pseudo-random noise (PRN) sequence such that each N-bit subsequence occurs only once on the track. Sensors detect transitions between the bits and bit-widths as the track moves with respect to the sensors to provide in-phase and quadrature-phase pick-off signals. The pickoff signals are summed and absolute value thresholded. The absolute value thresholded sum signal is sampled when the quadrature pairs are in the “00” or “11” quadrants, and latched when the sum signal goes high to distinguish between wide and narrow bit widths. The latch is shifted into a shift data register for use in determining the position of the encoder track. In the case of a PRN sequence having a length of 2Nbits, the position may be an absolute position when the number of valid bits in the shift data register is at least N. The position may be an incremental position when the number of transitions detected is less than N.
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Williams Darin
Wrigglesworth Walter
Alkov Leonard A.
Finn Thomas J.
Pyo Kevin
Raytheon Company
Vick Karl A.
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