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Proceedings Paper

A Practical Comparison Of Aberration Polynomials
Author(s): Ruixiang Liu; K G Birch
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Paper Abstract

A new approach to the numbering of detected interference fringes has been developed to enable computer analysis of interferograms containing closed-loop fringes, as captured by a TV-based lens testing Twyman-Green interferometer.3 The method requires some degree of operator intervention to set initial and maximum fringe numbers and information regarding the closed-loop fringes but otherwise is automatic. Following the fringe detection and numbering procedures the controlling computer evaluates "best-fit" values of the coefficients to predetermined aberration polynomials as used to represent the lens wavefront aberration presented in the interferogram. The wavefront aberration has been modelled by two different aberration polynomials, namely the Seidel and Zernike aberration polynomials. The latter polynomial includes additional terms to those in the former, enabling it to fit a wider range of asymmetries in the measured interferogram. It is therefore of considerable interest to compare the 'quality' of the fits obtained using the two aberration polynomials for a variety of interferograms. Results of the total process of data collection, polynomial fitting and lens Optical Transfer function evaluation are presented. The paper compares the residuals of fit, OTF curves and reconstructed interferograms derived from the same interferogram using the two polynomials. These suggest that, in general, the Zernike polynomials are more efficient than the Seidel polynomial.

Paper Details

Date Published: 14 May 1984
PDF: 9 pages
Proc. SPIE 0467, Image Assessment: Infrared and Visible, (14 May 1984); doi: 10.1117/12.941590
Show Author Affiliations
Ruixiang Liu, National Physical Laboratory (United States)
K G Birch, National Physical Laboratory (United States)

Published in SPIE Proceedings Vol. 0467:
Image Assessment: Infrared and Visible
Thomas L. Williams, Editor(s)

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