Title: Scanning photoelectric autocollimator

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Abstract: An electro-optical apparatus is disclosed which provides outputs proportional either to the surface profile and the first derivative of the surface profile of a reflecting surface or to some light beam deviating property of a transparent article in a non-contacting manner over a plurality of lines over the article being measured. A narrow beam of laser light is scanned in a raster pattern over the article to be measured. A uniformly rotating, multi-faceted reflector device which has suitably chosen pyramidal angles and which is placed near the focal point of a collimating lens moves the scanning laser beam, denoted the measurement beam, across the article to be measured in a series of laterally spaced lines. The scanning beam is nominally perpendicular to the article being measured. The measurement beam is either reflected by the surface of a reflective test article, or auto-reflected by a master reflector surface for double-pass transmission through a transparent test article. After probing the test article, the measurement beam is focused onto a two-axis photoelectric position sensor by the collimating lens. Electronic circuitry processes the signals generated by the photoelectric position sensor to provide outputs indicative of the surface profile and the first derivative of the surface profile, or some light beam deviating property of a transparent article, independent of the tilt of the test article surface relative to the scanning measurement beam. Most importantly, the apparatus provides outputs over the entirety of the test article which are solely a function of the properties of the article being measured.


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