We propose a configuration of an off-axis three-mirror system for maximum compactness and brightness. The chief ray is arranged to cross three times inside the system, and the system has a round configuration for compactness. We introduced into the design a ray triangle formed by the reflection points of the chief rays at the mirrors. The ray triangle indicates the size and the brightness of the system. Based on the proposed configuration, a design example of a 4° × 4° field of view is shown. The F-number of the system is 2.2, in close agreement with the estimation from the ray triangle.
© 2005 Optical Society of America
Original Manuscript: April 26, 2004
Revised Manuscript: September 29, 2004
Manuscript Accepted: October 2, 2004
Published: February 10, 2005
Takayuki Nakano and Yasuhisa Tamagawa, "Configuration of an off-axis three-mirror system focused on compactness and brightness," Appl. Opt. 44, 776-783 (2005)