This investigation applied the technique of spatial filtering to a projection printer utilizing partially coherent illumination. The affect of filtering on image quality parameters such as resolution, edge gradient and MTF were determined for a black and white film. Edge gradient analysis was used to derive MTF data from sampled edges. A source diameter of 3 mm and spatial filter diameters of .6, 2.2, and 3.0 mm were used. Spatial filtering was seen to have a drastic affect on edge gradient and MTF. Increasing the filter diameter resulted in a decrease of cutoff frequency of the system. Spatial filtering had the affect of boosting low frequency modulation by up to 30 percent. Subjectively, however, changes could not be detected, indicating that the alterations made to the system are not significant to be detected visually. Resolution was found to fluctuate only 15 percent between the application of each filter. Despite gross changes in other imaging characteristics, resolution remained nearly unchanged, indicating that resolution is a poor discriptor of image quality
