Definition of autocollimation in English:

autocollimation

Pronunciation /ˌɔːtə(ʊ)ˌkɒlɪˈmeɪʃn/

noun

  • The procedure of passing a beam of light though a converging lens on to a plane surface that reflects it back the way it has come (initially as a parallel beam); the use of an autocollimator; an instance of this.

    The procedure is used for purposes such as ascertaining the angle of a reflecting surface and measuring the alignment of machine parts.

Origin

Late 19th century; earliest use found in Nature: a weekly journal of science. From French autocollimation from auto- + collimation.