A laser system for measuring dimensional aberrations across a target surface includes a laser diode for producing a diverging beam of laser emission. A mask spaced from the diode in the beam has an aperture therein and can be moved so as to translate the aperture to selected locations laterally with...http://www.google.ca/patents/US5135307?utm_source=gb-gplus-sharePatent US5135307 - Laser diode interferometer
