Phase-shifting interferometry is a powerful tool for high accuracy optical measurement. It operates by change the optical
path length in the reference arm or test arm. This method practices by move optical device. So it has much problem when
the optical device is very large and heavy. For solve this problem, the wavelength-shifting interferometry was put
forwarded. In wavelength-shifting interferometry, the phase shifting angle was achieved by change the wavelength of
optical source. The phase shifting angle was decided by wavelength and OPD (Optical Path Difference) between test and
reference wavefront. So the OPD is an important factor to measure results. But in measurement, because the positional
error and profile error of under testing optical element is exist, the phase shifting angle is different in different test point
when wavelength scanning, it will introduce phase shifting angle error, so it will introduce optical surface measure error.
For analysis influence of OPD on optical surface error, the relation between surface error and OPD was researched. By
simulation, the relation between phase shifting error and OPD was established. By analysis, the error compensation
method was put forward. After error compensation, the measure results can be improved to great extend.