How to approach the design of a bilateral symmetric optical system

Two-mirror telescope design with third-order coma insensitive to decenter misalignment

“…Misalignments of the secondary mirror generate, among other aberrations, linear fielddependent astigmatism, which manifests as binodal astigmatism, and uniform coma. These aberrations may occur in plane-symmetric systems, as explained by Sasian [4]. For this type of systems third-order uniform coma is the most important misalignment-induced aberration [5].…”

“…When the axial symmetry is broken due to misalignments, different field-dependent aberrations may occur [4].…”

“…If linear and uniform coma are present in the system, the third-order zero-coma point (node) is not located in the center of the field. Misalignments will generate binodal astigmatism, that is two points in the field of view with zero-astigmatism [4,5].…”

“…This paper discusses a two-mirror, less-sensitive, telescope configuration, previously presented by Wilson [11], that is corrected for spherical aberration, and which is insensitive to decenter misalignments for field-uniform coma. Based on the wave aberration theory of plane-symmetric optical systems [4], which restricts surface tilts to one dimension with the gain of simplicity and ease of understanding, it is shown that for this configuration no uniform coma is generated by decenter misalignments. This feature makes the resulting RMS wave error to remain low even with considerable values of decenter in the secondary mirror.…”

“…The paper is organized as follows: Section 2 briefly describes two-mirror telescopes; Section 3 compares the sensitivity due to misalignments of a classical Cassegrain telescope, a Ritchey-Chrétien telescope and a similar configuration designed for the less-sensitive condition; Section 4 describes the aberrations generated in this system based on Sasian [4] approach for plane-symmetric systems; finally Section 5 concludes the paper.…”