Algorithm Based Metrology and Alignment Techniques for Measuring Optical Ground and Space Based Telescopes

Abstract

As manufacturing and optical metrology techniques continue to improve, optical systems are increasingly being designed to be more complex than ever. Not only increasing in complexity but also in size and Field of View (FOV) as well. This requires the use of more cumbersome ways of testing the performance both while in the manufacturing process and as the system is being assembled and aligned. This study discusses various techniques developed to aid in the inspection process during fabrication and alignment analysis of advanced and innovative optical systems, such as the grism instrument on board NASA’s Wide Field Infrared Survey Telescope (WFIRST). [1] This work presents three different techniques used to measure and verify ground and space based telescopes. The first technique provides the mathematical frame work to calculate the vertex radius of an asphere from measured sag values. The second technique uses measured data to obtain information about manufacturing errors which can contribute to poor system performance, such as misalignment when testing aspheres of varying asphericity or Diffractive Optical Elements (DOEs) with Computer Generated Holograms (CGHs). A parametric model was developed for this last case. The third technique is used to construct the alignment of a complex wide field optical system by methodically sampling its wide FOV and using the multi-field merit function regression method. [2, 3, 4] Each of the topics discussed has been researched, all main concepts tested, software and hardware solutions have been developed and verified by testing. Additionally, simulations and real data have been used to verify these algorithms and techniques.