  Traditional methods to achieve high localization accuracy with tactile
sensors usually use a matrix of miniaturized individual sensors distributed on
the area of interest. This approach usually comes at a price of increased
complexity in fabrication and circuitry, and can be hard to adapt for non
planar geometries. We propose to use low cost optic components mounted on the
edges of the sensing area to measure how light traveling through an elastomer
is affected by touch. Multiple light emitters and receivers provide us with a
rich signal set that contains the necessary information to pinpoint both the
location and depth of an indentation with high accuracy. We demonstrate
sub-millimeter accuracy on location and depth on a 20mm by 20mm active sensing
area. Our sensor provides high depth sensitivity as a result of two different
modalities in how light is guided through our elastomer. This method results in
a low cost, easy to manufacture sensor. We believe this approach can be adapted
to cover non-planar surfaces, simplifying future integration in robot skin
applications.
