Light-scattering-based high contrast optical touch sensor architectures in transmissive and reflective configurations

Abstract

Transmissive and reflective optical touch switch architectures based on the use of light scattering are proposed. Key features include high ON/OFF switching ratio, tunable sensitivity, ease of implementation, and no leakage optical beam incident on the user. Experimental proof of concept using a visible laser diode and a plastic Dove prism arranged in the transmissive configuration shows a high 24.4 dB contrast ratio which is a hundred times higher than obtained in the previous total internal reflection-based optical touch switch. In addition, switching response in milliseconds is also investigated for both lifting and sliding the fingertip out of the touching surface of the optical touch switch. Our light scattering-based optical touch switch also supports multiple keystroke operation.