Optical keyboard with common light transmission members

Claim 1

A keyboard comprising: a plurality of keys arranged in an M row by N column matrix format; a plurality of at least N light sources for generating N light beams, there being at least one light source for each column; a first light transmission member having at least N common light transmission paths each for transmitting at least one of said light beams from one of said N light sources to M terminal points, there being a terminal point for each row; a second light transmission member having at least M common light transmission paths, one for each row, each path having N light receptors, each N light receptor of a M light transmission path being aligned with a terminal point of a different light transmission path of said first light transmission member to form a light path therebetween; a plurality of interrupters each responsive to the depression of different key and each uniquely located between a terminal point and corresponding light receptor for interrupting the light path therebetween upon key depression; a plurality of M light sensors each aligned with a different one of said M light transmission paths for sensing the presence or absence of light transmitted along its associated second light transmission path; logic means for timewise sequencing said light sources and for gating the output signals of said sensors to provide a logic indication indicating the depressed key; wherein the improvement comprises: said first light transmission member having a plurality of M reflecting surfaces along the transmission path of each of said N light beams, each reflecting surface deflecting a portion of its associated light beam vertically from its first plane of travel within said first transmission member to a second plane of travel within said first transmission member; said first light transmission member having a second plurality of M reflecting surfaces for deflecting said portions of said light beams along a third plane of travel within said first transmission member vertically displaced from said first plane of travel and in a direction approximately orthogonal to the direction of travel of said light beam in said first plane of travel; said second light transmission member having a plurality of at least N reflecting surfaces for each of said M light transmission paths for directing light from said light receptors to said light sensors along each M common light transmission path.