US Patent No. 9,285,245

ABSOLUTE ENCODER


Patent No. 9,285,245
Issue Date March 15, 2016
Title Absolute Encoder
Inventorship Yoshiyuki Okada, Sakura (JP)
Assignee CANON KABUSHIKI KAISHA, Tokyo (JP)

Claim of US Patent No. 9,285,245

1. An absolute encoder comprising:
a scale on which a first mark and a second mark are arrayed;
a light source configured to emit light with which the scale is irradiated;
a detector configured to detect light from the scale, and to output periodic signals in which peak values, including a first
peak value corresponding to the first mark and a second peak value corresponding to the second mark and smaller than the first
peak value, periodically appear; and

a processor configured to obtain a code sequence by binarization of the first peak value and the second peak value in the
periodic signals output from the detector,

wherein the processor has a function of performing calibration so that the first peak value becomes larger than a threshold
for the binarization and the second peak value becomes smaller than the threshold,

the processor being further configured to
specify a largest first maximum value and a smallest second maximum value among maximum values of the periodic signals with
regard to respective periods thereof, and

set an intensity of the light emitted by the light source so that the first maximum value is not smaller than a first reference
value larger than the threshold, and the second maximum value is not larger than a second reference value smaller than the
threshold.