US Patent 7110122 Interferometer calibration methods and apparatus

A method for calibrating an interferometer uses an actuator adapted to control an optical gap in response to application of an electrical signal. The interferometer is illuminated with a beam of light having a predetermined substantially monochromatic wavelength, oriented at a first predetermined angle of incidence, and light reflected from the interferometer at a second predetermined angle is detected 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.