| CPC G01D 5/34715 (2013.01) [G01D 5/3473 (2013.01); G06F 3/0312 (2013.01); G06F 3/0362 (2013.01)] | 16 Claims |
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1. An electronic device comprising:
a housing defining an opening;
a display at least partially covering the opening;
a crown, attached to the housing and operable to be rotated with respect to the housing;
a shaft coupled to the crown and positioned at least partially within the housing, the shaft comprising an array of retroreflective surface features arranged in a single row extending around a circumference of the shaft, wherein each of the retroreflective surface features are separated from adjacent retroreflective surface features;
a self-mixing interferometry (SMI) sensor having a resonant cavity, the SMI sensor mounted to the housing and operable to:
emit light from the resonant cavity toward the crown;
receive, within the resonant cavity, a portion of the emitted light that reflects from at least one retroreflective surface feature in the array of retroreflective surface features; and
generate a SMI signal in response to a self-mixing of light within the resonant cavity; and
processing electronics coupled to the SMI sensor, the processing electronics performing an analysis on the SMI signal and determining, at least partly in response to the analysis, at least one of a position or a movement parameter of the crown.
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