Electro-optical mouse

A position control system for a cursor or the like comprising,

• a surface having a pattern of passive, position-related lines thereon, with a first group of lines characterized by reflection of one color and absorption of a second color and a second group of lines characterized by reflection of the second color and absorption of the first color,
• a detector means, movable over the surface, having a light source directed at the surface, alternately emitting light of said first and second colors, upon receipt of clock pulses, and a light detector positioned for receiving light reflected from the surface and producing electrical output signals representing reflection from lines in said first and second groups of lines,
• clock means connected to said source and detector for generating clock pulses timing said light source and synchronizing the detector output signals to the source, and
• counter means connected to receive said electrical signals for counting said lines during detector motion over the surface, thereby deriving a position signal for a cursor or the like.