Surveillance system

A solid, three optical surface, catadioptric element of an optical system, wherein the said catadioptric element provides the structural support and alignment stability between other optical elements and a mirror of the said optical system, and also provides the protective environmental enclosure of the optical elements and the mirror, and introduces no obscuration and/or vignetting of images for the field of view about the optical axis and where one surface of said catadioptric element is the last surface, excluding films and coating surfaces, of the optical system, and where the said catadioptric element's three effective surfaces listed sequentially from the focal plane side, comprise:

• a. a first surface, normal to and symmetric about the optical axis, primarily optimized for aberration correction, focus control and secondarily for field angle magnification between image and object space;
• b. a second surface which is a mirror normal to and symmetric about the optical axis and optimized as the primary transfer function between radial distance in the focal plane and the object surface and with the mirror surface redirecting the rays between the first surface and a third surface in accordance with basic reflection equations where the reflected and incident angles are of equal magnitude relative to the instantaneous surface normal;
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• c. a third surface, which is part of the physical surface connecting the first and the second optical surfaces, which is nominally parallel with, and a radial function of, the axial distance along the optical axis and is optimized as the secondary transfer function between radial distance in the focal plane and the object surface, said third surface redirecting the rays between the second surface of the catadioptric element and the object surface in accordance with Snell's basic refraction equation of n.sub.1 Sin .theta..sub.1 =n.sub.2 Sin .theta..sub.2, where n is the media's index of refraction, .theta. is the ray angle relative to the instantaneous surface normal and the subscripts 1 and 2 indicate the media of the ray, and the shape of this surface also provides modification for aberration correction and focus control.

A solid, four optical surface, catadioptric element of an optical system, wherein the said catadioptric element provides the structural support and alignment stability between other optical elements and a mirror of the said optical system, and also provides the protective environmental enclosure for the optical elements and the mirror, and introduces no obscuration and/or vignetting of images for the field of view about the optical axis and where one surface of said catadioptric element is the last surface, excluding films and coating surfaces, of the optical system, and where the said catadioptric element's four optical surfaces listed sequentially from the focal plane side, comprises:

• a. a first physical surface which is normal to and symmetric about the axis and has two optical surfaces herein identified as the first optical surface and third optical surface, where:
• i. the first optical surface is a transparent central core and may be the system's aperture stop at or near the vertex of a third optical surface;
• ii. the third optical surface is a reflective aspheric surface, about the first surface, and is the second reflective element after the aperture stop, where this mirror is optimized as the primary transfer function between radial distance in the focal plane and the object surface, and this surface redirects the rays between the second optical surface, which is also a mirror, and a fourth optical surface in accordance with basic reflection equations where the reflected and incident angles are of equal magnitude relative to the instantaneous surface normal;
• b. a second optical surface which is a mirror that is normal to and symmetric about the axial axis, and may be flat or optimized as either, or both, a low power aspheric or an axicon, where its primary function is to redirect the rays of the first optical surface to the third optical surface in accordance with basic reflection equations where the reflected and incident angles are of equal magnitude relative to the instantaneous surface normal;
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• c. a fourth optical surface, which is part of the physical surface connecting the second and the third optical surfaces, and which is nominally parallel with, and a radial function of, the axial distance along the optical axis and optimized as a transfer function between radial distance in the focal plane and the object surface by redirecting the rays between the catadioptric element's third optical surface and the object's surface in accordance with Snell's basic refraction equation of n.sub.1 Sin .theta..sub.1 =n.sub.2 Sin .theta..sub.2, where n is the media's index of refraction, .theta. is the ray angle relative to the instantaneous surface normal and the subscripts 1 and 2 indicate the media of the ray, and the shape of this surface also provides modifications for aberration correction and focus control.