Computer-controlled light box with uniform luminance at selectable levels for observer performance studies

John M. Herron; Yuan-Hsiang Chang

doi:10.1117/12.207649

27 April 1995 Computer-controlled light box with uniform luminance at selectable levels for observer performance studies

John M. Herron, Yuan-Hsiang Chang

Author Affiliations +

Proceedings Volume 2431, Medical Imaging 1995: Image Display; (1995) https://doi.org/10.1117/12.207649
Event: Medical Imaging 1995, 1995, San Diego, CA, United States

Abstract

A computer-controlled light box (14' X 17') with uniform luminance across the field at selectable levels was assembled as a part of a study to determine the combined effects of brightness and resolution on observer performance. Six horizontal and two vertical hot- cathode type (T8) lamps were used with direct current drive to eliminate flicker. Polarity of the voltage across each lamp is alternated to prevent migration of the mercury to one end. An optical feedback system accurately controls the overall luminance. Silicon detectors monitor the light from the first of two diffusing screens and provide analog feedback for rapid luminance correction. The light box is connected and controlled via the parallel port of the computer that handles observer performance databases and scoring forms. One of three luminance selections is performed by the computer, and a check of luminance is done prior to every case read in the study. The luminance spatial variation is within 5% over the central 80% of the field, and luminance levels are maintained within 5% of the predetermined levels of 225, 75, and 25 ft-L used in the observer performance study. Using conventional technology, uniform luminance across the field at selectable levels is achieved and eliminates potential effects of non-uniformities on observer performance.

Citation Download Citation

John M. Herron and Yuan-Hsiang Chang "Computer-controlled light box with uniform luminance at selectable levels for observer performance studies", Proc. SPIE 2431, Medical Imaging 1995: Image Display, (27 April 1995); https://doi.org/10.1117/12.207649

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