Approach to real-time contrast enhancement for airborne reconnaissance applications

Michael A. Henson; David Petro

doi:10.1117/12.47748

1 March 1991 Approach to real-time contrast enhancement for airborne reconnaissance applications

Michael A. Henson, David Petro

Proceedings Volume 1396, Applications of Optical Engineering: Proceedings of OE/Midwest '90; (1991) https://doi.org/10.1117/12.47748
Event: Applications of Optical Engineering: Proceedings of OE/Midwest '90, 1990, Rosemont, IL, United States

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

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Michael A. Henson and David Petro "Approach to real-time contrast enhancement for airborne reconnaissance applications", Proc. SPIE 1396, Applications of Optical Engineering: Proceedings of OE/Midwest '90, (1 March 1991); https://doi.org/10.1117/12.47748

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KEYWORDS

Cameras

Image processing

Control systems

Sun

Imaging systems

Signal processing

Optical engineering

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