A switch panel having a touch plate, image generator, and imaging system.
The touch plate includes an optically transparent layer having first and
second sides. The optically transparent layer having an index of
refraction greater than that of air. A light source generates a light
signal that is reflected between the first and second sides of the touch
plate within the transparent layer. The imaging system records an image
of the first surface. An image generator displays an image that includes
a plurality of button positions to a person viewing the touch plate from
the first side. A portion of the light signal is reflected toward the
second surface at an angle greater than the critical angle in the
optically transparent layer when the first surface is touched. The
imaging system determines the location of the touch from the location of
the reflected light.