INTERFEROMETRY METHOD BASED ON CHANGING FREQUENCY

An interferometry method using a laser of nominally fixed-but unknown and changing-frequency and phase angle, for example, attributable to laser drift. The interference pattern is periodically sampled at a frequency considerably higher than the phase shift of the object. The wavelength is reconstructed from the sampled patterns using a correlation algorithm. The phase angle is determined using an n-bucket algorithm. After all of the complex information has been determined at all of the multiple wavelengths, the surface of the object is calculated using conventional interferometry techniques. Accordingly, laser drift-typically considered a negative attribute-is used positively.