Patent attributes
A touch-sensitive apparatus comprises a light transmissive panel (1), an illumination arrangement and a detection arrangement. The illumination arrangement is configured to couple light into the panel (1) via an incoupling site (5B) such that the light propagates by total internal reflection (TIR) in opposite top and bottom surfaces (4, 5) of the panel and such that an object touching the top or bottom surface (4, 5) causes a change in the propagating light. The detection arrangement comprises a light detector arranged to detect the change in the propagating light. A compact and robust incoupling site (5B) is defined by a sheet-like micro-structured surface portion (22) which is fixedly arranged on one of the top and bottom surfaces (4, 5) and configured to transmit light having an angle of incidence that enables light propagation by TIR inside the panel (1). The surface portion (22) may be integrated in the panel or implemented by a thin and flexible film (20) of light transmissive plastic material, formed with the micro-structured surface portion and adapted for attachment to the top or bottom surface (4, 5).
