Optical glass compatibility for the design of apochromatic systems

The design of apochromatic systems is difficult because of two problems: the glass sorts compatibility and the c1/ca arbitrary input ratio. The optical glass manufacturers offer a wide range of sorts, so that the choice of triplet compatible glasses becomes itself an important separate problem. The paper provides a solution of mathematical modeling for the glass compatibility and, practically, analyses the sorts presented by Schott GmbH. The original software provided 22 compatible glass triplets. The authors explored the possibilities of enlarging the c1/ca ratio from the value 0.6 indicated in the literature to a range of [0.5?0.8]. Therefore, they designed and analyzed a set of 88 triplets. A correct glass choice can insure twice-larger apertures than the traditional ones for best quality apochromats (diffraction-limited).