Spatial noise suppression for LCD displays

In our work with LCD monitors for medical images, we have created a computer-program simulation-suite that mimics the appearance of an LCD screen. It uses high-magnification digital-camera capture of individual monitor pixels to compose realistic the sub-pixel patterns used in the simulations. These patterns are then weighted by digital driving levels, DDL's, that correspond to the image being displayed and inserted into a digital monitor field so as to compose an image of pixels that correspond to those of a monitor. The program suite also simulates the area-capture of a screenimage by a digital camera at a selectable magnification. The research project to which we are currently applying this simulation is the reduction of near-pixel-sized fixed-pattern noise. In the actual experiment a camera is used to capture a magnified portion of the monitor. Typical magnifications are 4:1 and 8:1 CCD to LCD pixels. From this captured image, a fixed-pattern multiplicative-noise gain map is generated that is used to adjust DDL's in order to pre-compensate for that noise. In addition to the spatial characteristics of the LCD monitor and CCD camera sensor, our simulation addresses nonlinearities found in the display and capture processes. The nonlinearities become important because 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 fluxdensity. This presentation focuses specifically on the comparison of the simulation results to physical experiments.