INTERFERENCE MEASURING METHOD AND APPARATUS

摘要

PROBLEM TO BE SOLVED: To achieve an accurate reduction in the effect of coherent noise components as generated by the interference between the light to be detected or the reference light and the specified noise light via at least a part of an optical path of the light to be detected or the optical path of the reference light by applying a fringe scan interference method concerning to an interference measuring method and apparatus for obtaining information on the shape of a surface to be detected by the fringe scan interference method. SOLUTION: Both of an optical distance of the optical path of the light to be detected and that of the optical path of the reference light are simultaneously changed in respective specified patterns to differentiate the cycle of change in the intensity of a signal component necessary out of an interference signal and the cycle of change in the intensity of the coherent noise component. As a result, the phase difference between the light to be detected and the reference light at a specified state is determined as information on the shape of a surface to be detected based on the interference signal to be outputted from a photo detector during the procedure of modulation scanning.