Optical encoder with direction-dependent optical properties

A portable electronic device comprising:

• a housing;
• a display positioned within an opening of the housing;
• a crown positioned on the housing and configured to receive rotational input;
• an optical encoder operatively coupled to the crown and configured to measure the rotational input, the optical encoder comprising:
• a spindle;
• an optical sensor configured to detect light reflected from the spindle;
• and
• an array of alternating regions formed on and extending along a length of the spindle.

An optical encoder for an electronic device, the optical encoder comprising:

• a spindle;
• an optical emitter configured to illuminate a portion of the spindle;
• an optical detector configured to receive light from the illuminated portion of the spindle;
• and
• an array of features arranged along a length the spindle;
• wherein the array of features is configured to produce alternating light and dark reflections on the optical sensor.