configuration of fig5 a and 5 b and fig7 shows for comparison the same maltese band for the apf with no color prism for parallel tilt axes the maltese band of the color prism overlays and is parallel to that of the pbs this reduces the width of the resulting maltese band resulting in a decrease in the contrast ratio between the configuration used in fig3 and 4 without a color prism and that used for fig5 a and 5 b with a color prism the degradation of contrast outside the relatively narrow region around the reflection plane of the central ray may be attributed to the color prism this is evident from fig7 which shows the equivalent pupil image when the color prism is removed the digital camera used for these images automatically re scales the brightness of the image so direct comparisons between the two figures is not possible however the contrast ratio for the configuration of fig7 is about six times that for fig6 meaning that this dark state pupil image is six times darker than fig6 performance of apf cartesian pbs and color prism with perpendicular tilt axes because the maltese band for the pbs itself is so deep and broad we expect that there may be a minimal degradation in contrast resulting from the crossing of the maltese band due to the.