Achromatic three-wave (or more) lateral shearing interferometer

A new kind of lateral shearing interferometer, called the three-wave lateral shearing interferometer, was previously described [ Appl. Opt.32, 6242 ( 1993)]. As this instrument was monochromatic and its usable light efficiency was poor, the proposed setup was well suited only for a class of wave-front sensing problems, such as optical testing, in which the source can be easily adapted. A new achromatic setup adapted to low light level applications is presented. Three replicas of the analyzed wave front are obtained by Fourier filtering of the orders diffracted by a microlens array. An important feature of these new devices is their great similarity to another class of wave-front sensors based on the Hartmann test.