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Optical Engineering

Experimental investigations on characterization of freeform wavefront using Shack–Hartmann sensor
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Paper Abstract

The metrology of freeform wavefront can be performed by the use of a noninterferometric method, such as a Shack–Hartmann sensor (SHS). Detailed experimental investigations employing an SHS as metrology head are presented. The scheme is of nonnull nature where small subapertures are measured using an SHS and stitched to give the full wavefront. For the assessment of complex misalignment errors during the spiral scanning, a library of residual slope errors has been created, which makes the alignment process fast converging for minimizing the scanning errors. A detailed analysis of the effects of slope and positioning error on reproducibility is presented. It is validated by null test where a null diffractive optical element has been used in a Mach–Zehnder configuration for compensating the freeform shape. A freeform optics is measured by both measurement schemes, and the results are in good agreement. Further, the nonnull-based scanning subaperture stitching scheme is also validated by performing measurements on an aspheric surface and compared with the measurements from the interferometric method (Zygo Verifire).

Paper Details

Date Published: 22 August 2017
PDF: 11 pages
Opt. Eng. 56(8) 084107 doi: 10.1117/1.OE.56.8.084107
Published in: Optical Engineering Volume 56, Issue 8
Show Author Affiliations
Dali R. Burada, Instrument Design Development Ctr. (India)
Kamal K. Pant, Instrument Design Development Ctr. (India)
Mohamed Bichra, Technische Univ. Ilmenau (Germany)
Gufran Sayeed Khan, Instrument Design Development Ctr. (India)
Stefan Sinzinger, Technische Univ. Ilmenau (Germany)
Chandra Shakher, Instrument Design Development Ctr. (India)

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