Many optical methods have been developed in non-contact 3D profile measuring fields, but these methods can not be used to measure the profile of a metal surface well, due to the influence of the specular reflection, steep slope and the roughness. In this paper a new optical displacement sensor called optical ring image sensor is presented. In order to verify the possibility applying this sensor to measure the profile shape of a metal surface, the light scattering characteristics of the metal surface are analyzed using computer simulation, and then the light intensity distribution detected by a CCD line sensor is investigated based on the theory of Kirchhoff diffraction. Furthermore, an experimental system of the sensor is constructed and the measuring experiments are carried out for a metal workpiece (S55C) with Rq=0.33μm. The experimental and theoretical results show that the sensor can be applied to measure the profile shape of a metal surface such as mold and die.
