ACCURATE INTERFEROMETRIC RETARDATION MEASUREMENTS

A two-polarization Michelson interferometer with a low-retardance beam splitter and digital signal processing is used to measure the retarda nce of optical devices. Error analysis of the improved optical system and data processing shows that the measurement has an uncertainty of 0 .039 degrees for measurements of nominally 90 degrees retarders. Retar dance variations arising from coherent reflections in the retarder use d for intercomparison add an uncertainty of from 0.005 degrees to 0.03 degrees, increasing the combined measurement uncertainty to as much a s 0.049 degrees.