High precision monoscopic fringe reflectometry based on a reference plane

Fringe reflectometry is a favorite method for 3D measurement of specular surfaces with the advantages of simple structure, low cost and high precision. The traditional reflectometry method is based on the telecentric optical path assumption. When the surface has a large diameter or curvature, this assumption is hard to be guaranteed. In addition, the non-sinusoidal distortion of fringes will also introduce significant phase errors and degrade the measurement accuracy. To avoid these problems, a high precision monoscopic fringe reflection measurement model is proposed based on a reference plane. The relative phase change between the measured surface and the reference plane is used to get the accurate corresponding screen points for each point on camera imaging plane. With these correspondence point pairs, the normal vectors and the 3D geometry can be obtained. To validate the effectiveness of the proposed method, a concave spherical mirror was measured. The peak to valley value of the residue error can reach 0.784μm which demonstrates high accuracy of the method.