Development of optical noncontact sensor for measurement of 3D profiles using the depolarized component of backscattered light

摘要

Abstract: To measure profiles of an object with 3D free-form surfaces, a new optical noncontact sensor is proposed in this paper. Two linearly polarized laser beams from the sensor, which are used for rough and fine positioning of the sensor, are focused on an object surface to be measured. The depolarized components of backscattered light from the object surface are detected, with the exception of specularly reflected light, using optical components. The triangulation method is applied to the sensor in order to obtain a signal which is proportional to the displacement of the object surface for rough positioning of the sensor. Moreover, the astigmatic focus error method is applied to the sensor in order to detect a focused positioning signal of the object surface for fine positioning of the sensor. The measuring instrument for 3D profiles of an object surface mainly consists of a newly designed optical noncontact sensor and tables. In the case of detection based on the astigmatic focus error method for fine positioning of the sensor, one special light detector for the sensor is proposed. Using the measuring instrument, 3D profiles of diffuse reflection surfaces and metal surfaces on which both specular reflection and diffuse reflection occur can be measured. Adverse effects of surface roughness, scratches, and diffraction on measurements can be reduced. !9