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Proceedings Paper

Criteria For Testing Of Afocal Visual Instruments
Author(s): G. J. Burton
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Paper Abstract

The aim of this paper is to identify possible objective test methods for afocal visual instruments which are relevant to user requirements. The problems associated with testing image quality of such instruments are introduced and discussed. A direct concern in this work is providing quality assurance specifications pertaining to sights of a fixed design but constructed in large production runs, not to small numbers of specially assembled sights. The experimental work is divided into two parts. The original investigation examines the levels of correlation obtainable between existing types of MTF-related image quality specifications and subjective resolution tests. It is demonstrated that greater care must be taken, than hitherto, in choosing appropriate test methods. In addition, very low levels of correlation are obtained between subjective resolution tests and objective MTF-related measures. The discussion of possible reasons leads, naturally, to the new investigation. A well-controlled analytical experiment was devised specifically to test the aspect unique to afocal visual instruments: coherent coupling between the sight and the eye. The investigation attempts to mimic, by subjective means, the variables and conditions relevant to (objective) MTF measurements. This investigation has not yet been completed; but the preliminary results do show, however, that expectations of quantitative agreement between subjective and objective test techniques are not borne out. The comparison fails spectacularly, suggesting that coherent coupling effects represent a major source of discrepancy. Some details are given of current measurements aimed at elucidating the precise factors involved in the optical coupling between an afocal sight and the eye.

Paper Details

Date Published: 29 October 1981
PDF: 11 pages
Proc. SPIE 0274, Assessment of Imaging Systems II, (29 October 1981); doi: 10.1117/12.931849
Show Author Affiliations
G. J. Burton, Royal Armament Research and Development Establishment (United Kingdom)

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

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