Multitouch touchless — A new approach with optical proximity sensing

This paper introduces a new approach to detect multiple inputs for touchless human machine interfaces. It is based on optical proximity sensing with visible or infrared light. It is described the principle of modulation, demodulation and system design. In the last part, some applications are presented to use this approach. The approach is based on multiple modulated light sources. The modulation is a form of direct sequence spread spectrum technique. One main advantage of the design is, that only one receiver is needed to detect multiple inputs. This held the system cost low.