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Proceedings Paper

Intercomparison Of Calculated And Measured Optical Transfer Function (OTF) For A Standard Triplet Lens
Author(s): K. G. Birch; A. C. Marchant
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Paper Abstract

This paper discusses the design, manufacture and testing of a standard 100 mm f/4 triplet lens and its subsequent use for checking the accuracy of OTF measuring equipment. The tolerances on individual lens parameters, established in the design stage, correspond to a maximum uncertainty in MTF of ±0.05 at 20 c/mm (on-axis at full aperture). Precautions necessary during manufacture to achieve this level of agreement between theoretical and measured performance for the assembled lens are described. Interferometric methods were used to assess the accuracy of manufacture, the wavefront aberration so determined being compared with results of calculation from the basic lens design data. The OTF was derived from the measured wavefront data, confirming that performance within the ±0.05 MTF tolerance band had been achieved. The MTF was also measured directly, using the SIRA-BECK Eros IV equipment at RAE Farnborough, and compared with the calculated performance. One result of this comparison was to indicate the presence of an unsuspected source of error in the measurement procedure adopted for this particular test. This demonstrates very clearly the value of having a lens such as this available as a primary standard of reference, and that the lens amply fulfils its original purpose.

Paper Details

Date Published: 29 October 1981
PDF: 8 pages
Proc. SPIE 0274, Assessment of Imaging Systems II, (29 October 1981); doi: 10.1117/12.931832
Show Author Affiliations
K. G. Birch, National Physical Laboratory (United Kingdom)
A. C. Marchant, Royal Aircraft Establishment (United Kingdom)


Published in SPIE Proceedings Vol. 0274:
Assessment of Imaging Systems II
Thomas L. Williams, Editor(s)

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