14 October 2004 Unique aspects of designing and tolerancing an optical testing system
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Abstract
The design & tolerancing of an optical testing system (OTS) presents a unique set of challenges not generally encountered during the typical optical design process. The authors have spent the past six years developing and using a series of optical systems designed to measure the surface figure & radius-of-curvature of various ultra-lightweight mirrors at 30 K. These mirrors were part of a technology development program to support NASA’s James Webb Space Telescope (JWST). The design of these systems required consideration of the following: (i) potentially large figure errors in the test mirror (due to gravity sag & cryo-distortion), (ii) cryo-shrinkage of the aperture and radius-of-curvature, (iii) figure changes due to the use of mirror actuators, and (iv) vibration between the OTS & the test mirror. In addition, an exhaustive tolerancing process was required for each system in order to reach a set of alignment tolerances that were achievable using the equipment available and within the test environment. The authors found many aspects of the OTS design process to be significantly different from the norm; at the same time, however, viewing the process as a typical optical design problem often-times brought clarification. This paper will describe both the differences and the similarities observed between the design of an OTS as opposed to a traditional imaging system.
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James B. Hadaway, Patrick J. Reardon, "Unique aspects of designing and tolerancing an optical testing system", Proc. SPIE 5523, Current Developments in Lens Design and Optical Engineering V, (14 October 2004); doi: 10.1117/12.557321; https://doi.org/10.1117/12.557321
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