METHOD FOR MEASURING INTERFERENCE AND APPARATUS FOR MEASURING INTERFERENCE

摘要

Both the optical distance of the detected -light light path and the optical distance of the reference-light light path are simultaneously varied according to respective specified patterns, so that differences are created between the period of variation in the intensity of the required signal component (in the interference signals) and the periods of variation in the intensities of the coherent noise components. When the modulation scanning procedure is performed, the phase difference between the detected light and reference light in a specified state is determined as shape information for the above-mentioned detected surface on the basis of the interference signals output from the light-receiving element. As a result, it is possible to securely reduce the effects of coherent noise components generated as a result of the interference of specified noise light that has passed through at least portions of the detected-light light path and reference-light light path with the detected light or reference light. <IMAGE>