Surface characterization protocol for precision aspheric optics

RamaGopal V. Sarepaka; Siva Sakthibalan; Somaiah Doodala; Rakesh S. Panwar; Rajendra Kotaria

doi:10.1117/12.2279804

16 October 2017 Surface characterization protocol for precision aspheric optics

RamaGopal V. Sarepaka, Siva Sakthibalan, Somaiah Doodala, Rakesh S. Panwar, Rajendra Kotaria

Proceedings Volume 10448, Optifab 2017; 104481D (2017) https://doi.org/10.1117/12.2279804
Event: SPIE Optifab, 2017, Rochester, New York, United States

Abstract

In Advanced Optical Instrumentation, Aspherics provide an effective performance alternative. The aspheric fabrication and surface metrology, followed by aspheric design are complementary iterative processes for Precision Aspheric development. As in fabrication, a holistic approach of aspheric surface characterization is adopted to evaluate actual surface error and to aim at the deliverance of aspheric optics with desired surface quality. Precision optical surfaces are characterized by profilometry or by interferometry. Aspheric profiles are characterized by contact profilometers, through linear surface scans to analyze their Form, Figure and Finish errors. One must ensure that, the surface characterization procedure does not add to the resident profile errors (generated during the aspheric surface fabrication). This presentation examines the errors introduced post-surface generation and during profilometry of aspheric profiles. This effort is to identify sources of errors and is to optimize the metrology process. The sources of error during profilometry may be due to: profilometer settings, work-piece placement on the profilometer stage, selection of zenith/nadir points of aspheric profiles, metrology protocols, clear aperture – diameter analysis, computational limitations of the profiler and the software issues etc. At OPTICA, a PGI 1200 FTS contact profilometer (Taylor-Hobson make) is used for this study. Precision Optics of various profiles are studied, with due attention to possible sources of errors during characterization, with multi-directional scan approach for uniformity and repeatability of error estimation. This study provides an insight of aspheric surface characterization and helps in optimal aspheric surface production methodology.

Citation Download Citation

RamaGopal V. Sarepaka, Siva Sakthibalan, Somaiah Doodala, Rakesh S. Panwar, and Rajendra Kotaria "Surface characterization protocol for precision aspheric optics", Proc. SPIE 10448, Optifab 2017, 104481D (16 October 2017); https://doi.org/10.1117/12.2279804

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