Some simple methods for calculating the radii of curvature of the null mirrors for a given Ritchey-Chretein system are described. The cases considered include the null for the concave primary, the null for the convex secondary, and examples of unobscured design, on-axis design, and off-axis design.
The Fresnel rhomb is used for the production 0of 0cirularly
polarized light. In this paper, we propose a set of two 45 -90 -45 prisms
which is equivalent to the Fresnel rhomb. The analysis of polarization
properties of such a set of prisms was done and it was found that fo
orginary experiments on polarizatin, it may satisfactory to use two 45 -90-
45 prisms for producing the circularly polarized light. It is not necessary
to fabricate a special prism i.e. the Fresnel rhomb with special angles. If
the faces of the prisms are coated with antireflection coatings, a high
degree of circularly polarized light is obtained. The polarization
calculations were done and verified by experiment.