126.96.36.199 Two corrector plates. Paul [4.4] investigated the case of a 2-plate corrector for a parabolic primary. His aim was the correction of coma and astigmatism. From (4.5) we have, then, the conditions
which is the same as the form given by Gascoigne [4.9] apart from a different normalization. Since f' and g are finite positive quantities and 0 < g < f', it follows that it is impossible to avoid introducing spherical aberration with a parabolic primary and two aspheric plates correcting coma and astigmatism. With g1 = f/10 and g2 = f/20, (4.17) gives
Was this article helpful?