Introduction To Long Focal Length Catadioptric Systems

Satisfaction of intelligence needs using high-altitude stand-off photography requires angular resolution that can only be achieved with large aperture optics. Unfortunately, straightforward application of purely refractive optical designs often leads to unacceptable large and/or massive optical systems. For these large aperture requirements, the less familiar catadioptric design approach offers a viable alternative to the opto-mechanically simpler refractive system. Design considerations for catadioptric photographic systems are discussed and specific refractive and catadioptric designs are compared. Particular attention is given to the potential for lightweight, thermally stable, catadioptric systems.