title: Focusing errors in a collimating lens or mirror: use of a moiré technique.
abstract: The Fresnel diffraction pattern of a grating periodically gives an exact reproduction of the grating. By superposing a second grating on such an image, we form a moiré pattern that depends upon the degree of parallelism of the incident beam. We present here the possibility of using this technique for studying the focusing errors in a collimating lens or a mirror.
authors.forename: J C
authors.initials: JC
authors.lastname: Fouéré
authors.forename: D
authors.initials: D
authors.lastname: Malacara