We describe a new method of multi-touch sensing which can be unobtrusively added to existing displays. By coupling individually controlled optoelectronics to the edge of a planar waveguide, our scanning approach overcomes prior disadvantages of optoelectronic multi-touch sensing. Our approach allows for a completely transparent touch surface and easy integration with existing LCD displays. Author Keywords Multi-touch, Frustrated total internal reflection, touch, tactile, interfaces, input devices ACM Classification Keywords H.5.2 Information Interfaces and Presentation: User Interfaces—Input Devices General Terms Design, Experimentation