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Proceedings Paper

Approach to real-time contrast enhancement for airborne reconnaissance applications
Author(s): Michael A. Henson; David Petro
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Paper Abstract

A new approach to realtime control of image contrast is described that is based on local scene statistics such as mean value and standarddeviation. The standardcontrastcontrolmethod observations ofthehighestandlowestpixelvalues within each set (Threshold detection) involves an inherently nonlinear feedback mechanism and is therefore difficult to control. A contrast controlloop using statistical detection techniques provides greater dynamic performance while decreasing sensitivity to scene anomalies such as sun glint when compared to contrast control loops using the traditional Threshold method. The Statistical approach is shown to offeradditionaladvantages incontrastenhancement when appliedto specificlightordarkregions of a scene. 2. THE CONTRAST CONTROL PROBLEM In order for the viewer of an image to recognize details of the scene and understand the picture the image mus have adequate contrast. By observing distantobjects on foggy days one sees that more distantobjects in areas oflowercontrast are very difficult to discern from neighboring objects at similar distances from the observer. As the distance between the observer and the objects decreases the features of the objects become clearer and more easily distinguished. Although the atmosphere is normally much clearer than the foggy example cited above the effects of the atmosphere on acquisition ofreconnaissance imagery is similar. Dust pollutants and other sources ofatmospheric haze contribute to reduce the contrast of the target scene on the ground as observed from the airborne platform. The effective reduction of scene contrast is particularly aproblem inlongrange oblique photography (LOROP)applications

Paper Details

Date Published: 1 March 1991
PDF: 8 pages
Proc. SPIE 1396, Applications of Optical Engineering: Proceedings of OE/Midwest '90, (1 March 1991); doi: 10.1117/12.47748
Show Author Affiliations
Michael A. Henson, CAI Div. of Recon/Optical, Inc. (United States)
David Petro, CAI Div. of Recon/Optical, Inc. (United States)

Published in SPIE Proceedings Vol. 1396:
Applications of Optical Engineering: Proceedings of OE/Midwest '90
Rudolph P. Guzik; Hans E. Eppinger; Richard E. Gillespie; Mary Kathryn Dubiel; James E. Pearson, Editor(s)

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