Spatial noise suppression for LCD displays
William J. Dallas, Hans Roehrig, Jiahua Fan, Elizabeth Anne Krupinski, Jeffrey P. Johnson · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2009
We deal with monochrome high-resolution LCD monitors used for displaying medical images. We discuss reducing near-pixel-sized components of fixed-pattern noise. This noise is composed of irregularities in the LCD pixel structure and fine background structures between pixels. We display a series of test images on the monitor with controlled LCD digital driving levels or DDL's. A calibrated CCD camera is used to magnify and capture a portion of the monitor for each image. The captured CCD digital values, or DSL's for digital sensor levels, are converted to luminance. This conversion is necessary because we employ a subsequent local-area processing step that relies on linearity of image-spread being in energy flux-density. Because we are working with two digital systems, the CCD camera and the LCD display, there is no continuous map between the CCD DSL's and LCD DDL's. We map the discrete LCD DDL's to a quantized luminance space. Once we have determined the target luminance values, we use an error-diffusion algorithm to select luminance values from the discrete addressable set for each pixel and then map those values to LCD DDL's. The result is a set of adjusted LCD DDL's that reduces the fixed-pattern noise in a locally averaged sense.