A method for improving the measurement accuracy of lateral shearing interferometry

A systematic error calibration method is presented to improve the measurement accuracy of lateral shearing interferometry (LSI). This method is used to remove the most significant errors: geometric optical path difference (OPD) and detector tilt error. Difference fronts in the 0° and 90° directions are used to reconstruct wavefront using difference Zernike polynomial fitting. And difference fronts in the 45° and 135° directions are also used to reconstruct wavefront. The coefficient differences between the reconstructed wavefront are generated from geometric OPD and detector tilt error. The relationship between Zernike coefficient differences and systematic parameters are presented based on shear matrix. Thus, the distance of diffracted light converging point ( d ) and detector tilt angle can be calculated from the coefficient difference. Based on the calculated d and detector tilt angle, the geometric OPD and detector-tilt induced systematic errors are removed and the measurement accuracy of LSI is improved.