Patent ID: 6940605
Filing Date: 2005-09-06
Classification: G01B

Abstract:
1. An interference measurement method using an interferometer, the interferometer comprising: an interference optical system which conducts light emitted from a light source to both a detected surface and a reference surface, and which causes interference between detected light that is generated by the reflection of the emitted light from the detected surface, and reference light that is generated by the reflection of the emitted light from the reference surface, and a light-receiving element which is disposed in a light path of an interference light formed by the detected light and the reference light, and which outputs interference signals corresponding to an intensity of an incident light, wherein said interference measurement method includes: a modulation scanning procedure which creates a difference between the period of variation in the intensity of required signal components in the interference signals that vary according to the phase difference between the reference light and the detected light, and the period of variation in the intensity of coherent noise components that are generated as a result of noise light that has passed through portions of the light path of the detected light and the light path of the reference light, the modulation scanning procedure creates the difference by simultaneously varying both the optical distance of the detected-light light path and the optical distance of the reference-light light path during a scan that varies the phase difference between the detected light and the reference light, and a calculation procedure which determines the phase difference between the detected light and the reference light as shape information for the detected surface, on the basis of the interference signals that are output from the light-receiving element when the modulation scanning procedure is being performed.