High-Resolution Tactile Imaging Sensor Using Total Internal Reflection and Nonrigid Pattern Matching Algorithm

A novel tactile imaging sensor, that is capable of measuring the elasticity of the touched object, is designed, implemented, and tested. In the proposed sensor, a multilayer Polydimethylsiloxane optical waveguide has been fabricated as the sensing probe. The light is illuminated at the critical angle to totally reflect within the flexible and transparent waveguide. When a waveguide is compressed by an object, the contact area of the waveguide deforms and causes the light to scatter. The scattered light is captured by a high-resolution camera. To find the elastic modulus of a touched object, multiple tactile images are taken from slightly different loading force values. The applied force has been estimated using the integrated pixel values of the tactile image. The strain has been estimated by matching the series of tactile images using the proposed nonrigid pattern matching algorithm. The measurement method was validated by the commercial soft polymer samples with the known elastic modulus. The experimental results showed that the tactile imaging sensor can measure the elastic modulus with the error less than 5.38%.