Measuring CRT display image quality: effects of phosphor type, pixel contrast and luminance

Abstract

There is much interest in methodology for accurate measurements of display image quality that is suitable for evaluation and Quality Control purposes. This work aimed to assess the image qualities of two mammography Cathode Ray Tube (CRT) displays for the detection of small targets simulating microcalcifications. Twenty five test patterns containing single pixel targets with variable background values and contrasts, and uniform background test patterns, were generated. Each test pattern was displayed on a P-45 and a P-104 five mega-pixel monitor and images were acquired with a CCD camera. An existing method for measuring Signal to Noise Ratio (SNR) of targets on uniform backgrounds was adapted by including a crucial step to suppress the spurious effects due to the raster lines in the display. It was found that SNR scaled linearly with target contrast and increased with background luminance. The P-45 phosphor was superior at low luminance. Preliminary indications are that this method may be the preferred way to evaluate AMLCD displays.