Infrared interferometer with a scanned aperture

A Twyman-Green interferometer operating at a 3.39-microm wavelength has been built in which the collimator aperture was scanned by a laser beam. The scanning was produced by reflecting the laser beam from a mirror supported by four piezoelectric elements and oscillated about two orthogonal axes. The radiation transmitted by the interferometer was measured by a stationary detector of small area. The complete system offers a cheap and efficient alternative to conventional ir interferometers.