Patent ID: 7110122

Claim:
A method for calibrating an interferometer having first and second reflecting surfaces and an optical gap between the first and second reflecting surfaces, the method comprising the steps of: a) providing an actuator adapted to control the optical gap in response to application of an electrical signal; b) illuminating the interferometer with a beam of substantially monochromatic light having a predetermined wavelength, the beam being oriented at a first predetermined angle of incidence to at least one of the first and second reflecting surfaces; c) detecting light reflected from the interferometer at a second predetermined angle to the at least one of the first and second reflecting surfaces while varying an electrical signal applied to the actuator, thereby establishing a calibrated relationship between the applied electrical signal and an optical path length of the interferometer; and d) correcting the calibrated relationship for application to subsequently incident light having at least one second angle of incidence differing from the first predetermined angle of incidence.