Filtering photodetector for use in optical encoders

An optical encoder, comprising:

• a first part that includes a light source and a photodetector;
• and
• a second part that is moveable relative to the first part, the second part including an optic configured to project an illuminated pattern onto the photodetector based on light from the light source,
• wherein the photodetector includes a semiconductor, the semiconductor including:
• a plurality of doped regions disposed over an oppositely-doped substrate, the doped regions laterally spaced apart from one another and forming respective photodiodes with the substrate;
• and
• a light-receptive semiconductor region laterally adjacent to a first doped region of the plurality of doped regions, the first doped region forming a first photodiode with the substrate,
• wherein the light-receptive semiconductor region is constructed and arranged to respond to illumination by stimulating current flow in the first photodiode.