3D Shape measurement of a transparent object with unknown refractive index by inverse ray tracing method

An optical measuring approach, by which to measure both the three-dimensional (3D) shape and the refractive index of a transparent object, was described. In order to obtain the 3D shape of a transparent object, contact-type sensors have been widely used in conventional approaches. However, the measurement accuracy of contact-type sensors is susceptible to various factors. The proposed measuring approach in the present work has two new characteristics. First, an inverse ray tracing approach was applied to measure the 3D shape of a transparent object or to an opaque object. Second, the refractive index could also be measured in this approach, the same as the measuring device used for the 3D shape measurement. According to the simulation results, the 3D-shape of an object as well as the refractive index was easily measured by means of the proposed range finding approach, which shows great potential for a wide range in industrial applications.