Comparing methodologies for determining resolution from contrast in projection display systems

The accurate measurement of spatial resolution can be critical in the characterizations of projection display systems. Techniques can be used to determine resolution of projection systems by measuring the contrast of alternating grille patterns or fully modulated sine waves of various spatial frequencies. Unfortunately, the measurement of the contrast of these patterns may be influenced by stray light, either from ambient and reflected light in the environment, or from veiling glare (light scattering) in the lens of the light-measuring device. Such stray-light corruption can lead to large errors in contrast determination, providing an inaccurate and misleading characterization of the projector. For large-area measurements, various tools and methodologies have been employed, including the use of frustums and masks, to minimize such unwanted effects and provide a more accurate measurement. With some modifications, these same tools may be used for small-area measurements with similar results. Results will be shown comparing resolution determinations using different test methodologies with and without stray light compensation.