Improvement in the fabrication of large solid-state focal plane array photonic sensors has emphasized the need for telescopes with flat and wide angular fields of high resolution and with large spectral passbands. To increase the angular field of Cassegrain-like telescopes, various designs of correctors have been incorporated in the optical train. This paper compares specific designs based on the Dall-Kirkham format of prolate ellipsoid primary and spherical secondary mirrors, in which excellent correction is achieved over a significant field angle. The attraction of the Dall-Kirkham format is the relative ease of fabrication to a very high accuracy by simple null tests of the concave prolate-ellipsoid primary by specific separation of light source and knife-edge, and of the convex secondary by interference-matching with a previously null-tested concave spherical master. Null tests of the more common Ritchie-Chretien design require the additional fabrication of two "Hindle spheres" or other auxiliary optics such as holograms for testing of the hyperboloidal primary and for the hyperboloidal secondary. If the Dall-Kirkham format is modified to include variants in which the "Cassegrain" image is imperfect or even afocal, it is possible to design simple corrector relays with exceptional final imaging characteristics. Examples are presented that provide distortionless, diffraction-limited, flat-field imaging over usefully wide fields and large passbands at speeds of f/5 - f/4, and having an unusually compact layout.

Date Published: 26 August 2005
PDF: 12 pages
Proc. SPIE 5874, Current Developments in Lens Design and Optical Engineering VI, 58740H (26 August 2005); doi: 10.1117/12.613292

Published in SPIE Proceedings Vol. 5874:
Current Developments in Lens Design and Optical Engineering VI
Pantazis Z. Mouroulis; Warren J. Smith; R. Barry Johnson, Editor(s)