Patent ID: 7952799

Claim:
An optical system adapted to operate in either a narrow field of view mode or a wide field of view mode of an object, the optical system comprising: a first entrance aperture; a second entrance aperture; moveable field of view changing fold mirror; a reflective beam expander; a reflective imager; and an imaging detector; wherein in the narrow field of view mode: the moveable field of view changing fold mirror is located out of an optical beam path; the reflective imager includes: a primary mirror positioned to receive and reflect a first optical beam that passed through the first entrance aperture; a secondary mirror positioned to receive and reflect the first optical beam reflected from the primary mirror; and a tertiary mirror positioned to receive and reflect the first optical beam reflected from the secondary mirror; the imaging detector is positioned to receive the first optical beam reflected from the tertiary mirror and to image the object; wherein in the wide field of view mode: the reflective beam expander includes: a tertiary mirror positioned to receive and reflect a second optical beam that passed through the second entrance aperture; a stationary fold mirror positioned to receive and reflect the second optical beam reflected from the tertiary mirror; a secondary mirror positioned to receive and reflect the second optical beam reflected from the stationary fold mirror; and a primary mirror positioned to receive and reflect the second optical beam reflected from the secondary mirror; the moveable field of view changing fold mirror is located in the optical beam path and positioned to be a first component to receive the second optical beam reflected from the primary mirror in the reflective beam expander and to reflect the second optical beam to the reflective imager; the reflective imager includes: the primary mirror is positioned to receive and reflect the second optical beam reflected from the moveable field of view changing fold mirror; the secondary mirror is positioned to receive and reflect the second optical beam reflected from the primary mirror; and the tertiary mirror is positioned to receive and reflect the second optical beam reflected from the secondary mirror; and the imaging detector is positioned to receive the second optical beam reflected from the tertiary mirror in the reflective imager and to image the object.