Fast separation method of misalignment errors for cylindrical full-surface interferometry

Abstract

Right-angle conical mirror is widely used for wavefront conversion, which can construct a null interferometric optical path to achieve interferometric measurement of the cylindrical full-surface topography. However, the effect of the misalignment error on measurements is very significant, due to the difficulty in adjusting the position and attitude of the right-angle conical mirror and the measured cylindrical surface to the ideal state. The pure tilt misalignment errors will lead to parallel interference fringes. Based on this important finding, we propose a fast separation method of translation and tilt misalignment errors. First, adjust the relative translation of the right-angle conical mirror and the cylinder to be measured until all interference fringes are parallel. Then, perform measurement and remove the regular primary tilt from the result to separate the misalignment error effectively, so that the cylindrical full-surface topography is obtained. Under various misalignment errors, the extreme difference of all the PV values of the cylindrical surfaces measured by our method is less than 0.07λ. Experiments indicate that the proposed method can obtain essentially consistent measurements under different misalignment errors. Furthermore, the method is simple to operate and requires no data processing, laying the foundation for the practical application of cylindrical full-surface interferometry measurement.