Interferometric surface profiler

An interferometric profiler capable of measuring the topography of a surface under test comprising a source of a first spatially coherent linearly polarized input beam;

• means optically aligned with said input beam for significantly reducing the spatial coherence of said input beam;
• means optically aligned with said coherence reduced input beam for producing a linearly polarized collimated second beam which has significantly reduced spatial coherence;
• means optically aligned with said surface under test and said second beam for splitting said second beam into a linearly polarized, reflected reference wavefront and a circularly polarized, transmitted measurement wavefront;
• said second beam splitting means including a flat reference surface spaced from said surface under test;
• means for varying the spacing between said reference surface and said surface under test;
• means optically aligned with said reference surface and sa id surface under test for recombining said reference wavefront and said measurement wavefront after it interacts with said surface under test;
• an imaging device optically aligned with said surface under test for photosensing and viewing either alignment spots or an interference pattern produced from said recombined reference and measurement wavefronts;
• means for imaging said surface under test onto said photosensitive elements;
• said imaging means comprising means for bringing a very smooth surface under test into focus onto said photosensitive elements;
• and means operatively connected to said imaging means for processing the output of said imaging device for providing a profile of said surface under test.