Aspherical mirror testing with an area detector array

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Abstract
A deep aspherical surface testing method using an interferometer and an area array sensor is presented. The method is based on a fringe-scanning phase-detecting method. The method has high accuracy and does not require an aspherical reference surface, a null lens, or a hologram. After calculating the object-wavefront phase, a computer displays the sag difference map between a measured surface and an ideal aspherical surface. Results for testing an ƒ/3 200-mm diam parabolic mirror are presented.