THE SENSITIVITY OF THE COMMON FOCUS ERROR OF A REFERENCE LENS ON THE MEASUREMENT ACCURACY IN A FIZEAU INTERFEROMETER

A technique used to examine the performance of reference lens of inter ferometer is described. The defects in the reference lens that are pri marily due to the manufacturing errors or the assembly errors or both will result in the common focus error of reference lens at the centre of curvature of reference surface, which affects the measurement accur acy. The optical path difference between the reference wave front and the test wave front at the exit pupil is applied to analyse the influe nce of common focus error of reference lens on the measurement errors. A comparison of the experimental result with the numerical analysis i s made.