Motion Sensing by Monitoring Intensity of Light Redirected by an Intensity Pattern

A displacement measuring system comprising:

• (i) a back electromotive force (bEMF) sensing system to acquire a first displacement signal that relates to a time dependence of a displacement of a mass, wherein the displacement is relative to a datum of the displacement measuring system;
• (ii) an optical sensing system comprising
• an intensity pattern that is coupled with the mass and comprises two or more tiles separated from each other by corresponding one or more tile borders, wherein the tile borders are at known locations relative to each other;
• a light source that is at rest relative to the datum to illuminate the intensity pattern with a light beam, wherein multiple tile border crossings occur while the first displacement signal is being acquired, wherein a tile border crossing is said to occur when a tile border of the intensity pattern crosses through the light beam;
• and
• a photodetector that is at rest relative to the datum to acquire an intensity signal corresponding to intensity of the light beam redirected to the photodetector from the intensity pattern, wherein the intensity signal is indicative of the tile border crossings;
• and
• (iii) a processor to
• spatially resolve the tile border crossings indicated by the intensity signal, at least in part, based on whether the first displacement signal increases or decreases at a time when a tile border crossing has occurred;
• and
• determine the displacement of the mass based on the spatially resolved tile border crossings.