OPTICAL POSITION DETECTION OF A TIMEPIECE CROWN STEM

摘要

The present invention concerns a method of detecting a movement of a timepiece setting stem (1) arranged to be moved axially along and/or rotated about its longitudinal axis. The method comprises: (a) a light source (5) illuminating a portion of the setting stem (1); (b) a light detector (12) receiving a reflected or diffracted light pattern (9) from the setting stem (1); (c) a processor (13) forming a first pixel pattern representative of the reflected light pattern at a first time instant; (d) the processor (13) forming a second pixel pattern representative of the reflected light pattern at a second, later time instant; and (e) determining that the setting stem (1) has been moved, if the second pixel pattern is different or shifted with respect to the first pixel pattern.