Optical prefilters, which make use of the double-refraction effect in crystalline quartz, reduce the amount of aliasing artifacts in the displayed image of a video system. This paper describes a new class of optical prefilter that produces different amounts of blur for different colors. This type of filter is useful with sensors that have unequal pixel densities in the three sensed colors.
John E Greivenkamp,
"Color-Dependent Optical Prefilter For The Suppression Of Aliasing Artifacts", Proc. SPIE 0900, Imaging Applications in the Work World, (11 May 1988); doi: 10.1117/12.944687; https://doi.org/10.1117/12.944687