<title>Full Aperture Testing With Subaperture Test Optics</title>

Abstract

This paper is an overview of recent work of the Lockheed Palo Alto Research Laboratory on the use of subaperture test optics to evaluate the performance of large optical systems. Supported by selected subscale experiments, a theory has been developed that addresses two test conditions, each based on the use of a known test flat in a double-pass configuration with a collimated optical system of unknown quality. The two test conditions, in order of increasing theoretical complexity, are: (1) a single test flat covering only a portion of the full-system aperture, and (2) multiple (not necessarily coherent) test flats. Analyses predict limited utility of a single test subaperture as a function of a subaperture size and location, and aberration content. Multiple subapertures viewing the full system are shown to give good results for higher order aberrations even when the individual test flats are unphased and contain large relative tilt errors. The test techniques described here are fully scalable to future optical systems of arbitrary size. This paper summarizes the theoretical basis for subaperture testing, gives quantitative performance predictions for some selected cases, and presents the results of supporting experimental work.