Fast Ronchi test base on a liquid crystal display

A combination of a small liquid crystal display, conventional Ronchi test and fringe-scanning test is used to measure an aspheric wavefront or a large wavefront aberration system, faster and more exacting. Instead of a common grating and a step-motor, a movable image of grating is showed in a liquid crystal display. This gets rid of the error that caused by grating moving or motor rotating. A formula of the light intensity of the two dimensional grating, which a liquid crystal display owns, is derived. 12-step phase-shifting algorithm is used to test a lens, and the large wavefront aberration of the lens is restored.