OPTICAL COUPLING OF LIGHT INTO TOUCH-SENSING SYSTEMS

摘要

A touch-sensitive apparatus operates by light frustration (FTIR) and comprises a light transmissive panel (1) with a front surface (5) and a rear surface (6). Light emitters (2) and light detectors are optically coupled to the panel (1) to define a grid of light propagation paths inside the panel (1) between pairs of light emitters (2) and light detectors. A light in coupling structure comprises a diffusively reflective element (20) on the rear surface (6) and a specularly reflective element (22) on the front surface (5). Each light emitter (2) is arranged to project a beam of light onto a transmissive surface portion (24) on the rear surface (6), such that at least a portion of the beam of light enters the light transmissive panel (1) through the transmissive surface portion (24), is specularly reflected against the specularly reflective element (22) and impinges on the diffusively reflective element (20) from inside the light transmissive panel (1).