Position sensing systems for use in touch screens and prismatic film used therein

摘要

A dual light-source position detecting system for use in touch screens is provided that utilizes parallax to determine the position of an interposing object, and a prismatic film that is brightly retroreflective over a broad entrance angle to enhance to accuracy of the parallax determination of position. The position detecting system includes at least one camera positioned to receive light radiation traversing a detection area and that generates a signal representative of an image; two spaced-apart sources of light radiation, which may be LEDs, or IR emitters positioned adjacent to the camera for outputting light radiation that overlaps over at least a portion of a detection area, and a prismatic film positioned along a periphery of at least a portion of the detection area that retroreflects the light radiation from the two sources to the camera.

主权项

1. A position detection system comprising:
a camera positioned to receive electromagnetic radiation traversing a detection area that generates a signal representative of an image; a dual source of electromagnetic radiation positioned adjacent to said camera for outputting electromagnetic radiation that overlaps over at least a portion of a detection area, and a prismatic film positioned along a periphery of at least a portion of the detection area that retroreflects said electromagnetic radiation from said source to said camera, wherein the prismatic film includes a plurality of individual triangular cube corner retroreflective elements having dihedral angle errors e1, e2, and e3 such that e1≈e2≠0 and e3≈0, and wherein e1 and e2 are either both positive or both negative in each individual triangular cube corner element.