Patent US 5,771,095

An optical system for determining aberration in a source beam by comparison of a test beam with a reference beam. The optical system includes a test source for producing a source beam having a spacial intensity distribution including an aberration component, a wavefront analyzer for processing a fringe signal associated with the aberration component, and an interferometer. The interferometer is provided with a beamsplitter for splitting the source beam into a test beam and a reference beam, an imaging device for detecting the test beam and the reference beam, and a mirror disposed in a test beam path for reflecting the test beam toward the imaging device. The interferometer also includes a micromirror disposed in a reference beam path for reflecting a portion of the reference beam toward the imaging device and a piezoelectric translator operatively linked to the mirror and controlled by the wave front analyzer. The mirror is capable of moving relative to the path of the test beam. The micromirror has a lateral dimension not exceeding the approximate lateral dimension of a central lobe of the reference beam as focused thereon by focusing means so that when the test beam is reflected by the mirror and the portion of the reference beam is reflected by the micromirror, the reflected test beam and the reflected portion of the reference beam are both incident upon the imaging device forming an interference pattern including fringes which are converted into the fringe signal.