A 3-DoF motion error measurement system based on film interferometry

To accomplish the simultaneous measurement of motion errors for a topography measurement system, a 3-DoF (Degree of Freedom) motion error measurement system based on film interferometry is proposed. An optical flat was the moving unit, whereas a prism group consisting of two equilateral prisms and a right-angle prism formed the stationary sensing head. There was an air wedge between the prism group and the optical flat. A horizontally incident laser beam was used to generate an interferogram, the phase shift of which was directly related to the standoff variation, yaw, and roll. The interferogram was captured by a camera and combined with an in-house -developed image processing algorithm, and the above three motion errors could be simultaneously obtained. The experimental results demonstrated that the linear and angular measurement accuracies of the system were & PLUSMN;0.08 & mu;m and & PLUSMN;0.55 & DPRIME;, and the repeatability represented by the standard deviation was within 40 nm and 0.4 & DPRIME;.

Automated summary

To simultaneously measure motion errors for a topography measurement system, a 3-DoF motion error measurement system based on film interferometry is proposed. The system utilizes an optical flat as the moving unit and a prism group as the stationary sensing head. A horizontally incident laser beam generates an interferogram, which is captured by a camera and processed to obtain the motion errors. Experimental results show high measurement accuracy and repeatability.