The JWST infrared Scanning Shack Hartman System: a new in-process way to measure large mirrors during optical fabrication at Tinsley

Craig Kiikka; Daniel R. Neal; John Kincade; Robert Bernier; Tony Hull; David Chaney; Steve Farrer; John Dixson; Avery Causey; Steve Strohl

doi:10.1117/12.672887

7 July 2006 The JWST infrared Scanning Shack Hartman System: a new in-process way to measure large mirrors during optical fabrication at Tinsley

Craig Kiikka, Daniel R. Neal, John Kincade, Robert Bernier, Tony Hull, David Chaney, Steve Farrer, John Dixson, Avery Causey, Steve Strohl

Author Affiliations +

Proceedings Volume 6265, Space Telescopes and Instrumentation I: Optical, Infrared, and Millimeter; 62653D (2006) https://doi.org/10.1117/12.672887
Event: SPIE Astronomical Telescopes + Instrumentation, 2006, Orlando, Florida , United States

Abstract

Tinsley, under JWST funding, has led the team that has developed a novel and highly versatile piece of ground support equipment for optical surface testing of JWST beryllium mirror segments during optical fabrication. The infrared Scanning Shack Hartmann System (SSHS) offers the advantage of being able to characterize mid-to-high spatial frequency structure on a mirror from early stages of fabrication when slopes may be high and surface irregular, eliminating the need for an extra polishing step before metrology. Working at 9.3μm, the system will accept and measure a wide dynamic range of surface characteristics, including roll-off near the edge of the segment. Knowledge of these surface features at the early grinding stage is imperative if characteristics such as mirror edge roll-off are to be minimized. WaveFront Sciences, producer of commercial COAS and Columbus Shack Hartmann systems, has provided systems engineering and component support for the SSHS system. The SSHS system is based around a special Long Wave Infrared (LWIR) wavefront sensor developed by WaveFront Sciences that is scanned over the mirror surface, making sub-aperture measurements. The smaller, high-resolution measurements are then stitched together to provide high-resolution measurement of the entire mirror surface, even though the surface is in a rough ground state. The system leverages technology from smaller visible instrumentation produced by Wavefront Sciences, especially those for surface sub-aperture measurements of semiconductor wafers. This paper will describe the implementation of the first infrared scanning Shack Hartmann system at Tinsley to address optical fabrication optimization of the JWST Primary Mirror Segments.

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Craig Kiikka, Daniel R. Neal, John Kincade, Robert Bernier, Tony Hull, David Chaney, Steve Farrer, John Dixson, Avery Causey, and Steve Strohl "The JWST infrared Scanning Shack Hartman System: a new in-process way to measure large mirrors during optical fabrication at Tinsley", Proc. SPIE 6265, Space Telescopes and Instrumentation I: Optical, Infrared, and Millimeter, 62653D (7 July 2006); https://doi.org/10.1117/12.672887

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