Multi-special decentered catadioptric optical system

Abstract

A multi-spectral decentered catadioptric-type optical system suitable for use with long range oblique aerial reconnaissance camera systems, spectrum analyzers, astronomical imagers, remote sensing, and other applications is described. The optical system includes an aspheric primary mirror receiving incident radiation and defining a central aperture. An aspheric secondary mirror is provided for receiving the radiation from the primary mirror. The primary and secondary mirrors are positioned and constructed such that entrance aperture of the system is displaced or decentered relative to the optical axis of the system, so as to thereby increase the modulation transfer function of the optical system as compared to a centrally obscured system. The aspheric secondary mirror directs the incident radiation onto a means for splitting the radiation to a first optical path and a second optical path. A first field optical assembly is placed in the first optical path for directing radiation in a first portion of the electromagnetic spectrum onto a first radiation receiving device, such as a film camera or electro-optical detector. A second field optical assembly is placed in the second optical path for directing radiation in a second portion of the electromagnetic spectrum, for example, wavelengths in the infrared portion of the spectrum, onto a second radiation receiving device, such as an electro-optical detector. The optical system permits dual spectrum imaging by the first and second detectors of both visible and infrared portions of the spectrum, while providing improved modulation transfer functions for both portions of the spectrum. Further, the optical system is especially suitable for applications requiring a long focal length of the optical system and a wide field of view, such as long range aerial reconnaissance camera systems and astronomical imagers.