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Proceedings Paper

Zoom lens calibration for wind tunnel measurements
Author(s): Alpheus W. Burner
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Paper Abstract

This report summarizes an investigation of zoom lens calibration, with emphasis on the effects of lens-image-plane misalignment. Measurements have been made of the photogrammetric principal point and radial (symmetrical) and decentering (asymmetrical) distortion components as a function of the principal distance (zoom setting) of several zoom lenses. Data were also taken with the axis of symmetry (optical axis) of a zoom lens aligned and misaligned to the same solid-state video camera. An explanation is offered regarding the variation of the principal point as a function of zoom setting based on these measurements. In addition the relationship of the decentering distortion to radial distortion, principal distance, and lens- image-plane misalignment angle is discussed. A technique for determining the proper point of symmetry to be used for distortion computations (as opposed to the principal point) is also suggested. A simple technique for measuring the misalignment angle of zoom lenses when attached to video cameras is presented, along with measurements for seven solid-state cameras. A method to reduce the additional error introduced by zoom lens misalignment is presented. The implications of this study are that special measures to properly align a zoom lens to the sensor image plane are probably not necessary, but that as the accuracy obtainable in digital photogrammetry approaches the 0.01 or less pixel level, additional calibration including the point of symmetry for distortion computation should be considered.

Paper Details

Date Published: 13 September 1995
PDF: 15 pages
Proc. SPIE 2598, Videometrics IV, (13 September 1995); doi: 10.1117/12.220901
Show Author Affiliations
Alpheus W. Burner, NASA Langley Research Ctr. (United States)

Published in SPIE Proceedings Vol. 2598:
Videometrics IV
Sabry F. El-Hakim, Editor(s)

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