Range sensing based on shearing interferometry

We report an optical range sensor that combines the advantages of focus sensing and interferometry. It works for specularly reflecting objects and for diffusely reflecting objects. The sensor is simple, robust against vibrations, and has high depth resolution. The aperture is very small, hence the sensor is small and minimizes shading problems. The sensor is based on the following principle: A light spot is projected onto the object under test. The radius of the wave that is scattered at the object is measured with high accuracy by shearing interferometry.