Patent ID: 8294903

Claim:
A surface shape measurement, apparatus comprising: a light source for emitting light; a plurality of wavelength filters having respective different transmission wavelengths; a changeover device for changing over among the plurality of wavelength filters; an interference optical system configured to divide light passed through one wavelength filter out of the plurality of wavelength filters among which changeover is performed by the changeover device, further irradiate with divided lights an object to be inspected and a reference surface, and superimpose lights respectively reflected by the object and the surface on each other for causing interference therebetween; an image pickup device configured to pick up an image of interference fringes resulted from the interference caused by the interference optical system; an interference-fringe phase detection unit for calculating a phase of interference fringes from the image created through the image pickup by the image pickup device; a filter angle adjustment unit which is configured to combine phases of interference fringes of at least two wavelengths, which have been calculated through changeover among the plurality of wavelength filters by the changeover device, to detect a wavelength difference therebetween, and, further, is configured to adjust an inclination angle of one wavelength filter out of the plurality of wavelength filters with respect to optical axis of the light incident to the wavelength filters, based on the wavelength difference; and an analysis unit configured to measure a surface shape of the object to be inspected, using the interference optical system, the image pickup device, and the interference fringe phase detection unit, at a state where the inclination angle of the one wavelength filter is adjusted.