Adjustable optical test apparatus including interferometer with micromirror and alignment observation system

An adjustable optical system for determining aberration in a source beam by comparison of a test beam with a reference beam, said optical system comprising:

• 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 said aberration component;
• and
• an interferometer interposed between said test source and wavefront analyzer, said interferometer including;
• a beamsplitter for splitting said source beam into a test beam traveling on a test beam path and a reference beam traveling on a reference beam path;
• an imaging device for detecting said test beam and said reference beam;
• a mirror disposed in said test beam path, said mirror reflecting said test beam toward said imaging device;
• a micromirror disposed in said reference beam path, said micromirror reflecting a central portion of said reference beam toward said imaging device and allowing an outer portion of said reference beam to pass thereby;
• alignment image means for collecting and detecting said outer portion of said reference beam so that said micromirror may be adjusted relative to said central and outer portions of said reference beam;
• and
• focusing means disposed in said reference beam path between said beamsplitter and said micromirror for focusing said reference beam on said micromirror, said micromirror having a lateral dimension not exceeding the approximate lateral dimension of a central lobe of said reference beam focused thereon by said focusing means so that when said test beam is reflected by said mirror and said central portion of said reference beam is reflected by said micromirror, said reflected test beam and said reflected portion of said reference beam are both incident upon said imaging device forming an interference pattern thereon, said interference pattern including a plurality of fringes which are converted into said fringe signal by said imaging device.