title: Measuring parallelism of two parallel narrow beams based on differential defocusing principle.
abstract: We present a method of measuring the parallelism of two parallel narrow beams by positioning a CCD each before and after the focal plane of the collimation lens. Because of this differential defocused positioning of the two CCDs, the two beam spots cannot overlap on the CCD image plane even if they are nearly parallel, and the distance between the two spots on each CCD can be obtained simultaneously, which eliminates the influence of environmental noise. Our experimental results show that a satisfactory system stability and resolution of 0.1″ and 0.2″, respectively, can be obtained with the proposed method.
authors.forename: Zhengang
authors.initials: Z
authors.lastname: Lu
authors.forename: Miaomiao
authors.initials: M
authors.lastname: Li
authors.forename: Tao
authors.initials: T
authors.lastname: Zheng
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Jiubin
authors.initials: J
authors.lastname: Tan