Telescopic optical system

Claim 2

A catadioptric system comprising: a concave main mirror having a central light aperture; a first plural element correcting refractor positioned to intercept and refract light passing to said main mirror from outside said system, said first refractor comprising a first annular positive lens and a second annular negative lens positioned adjacent to said first lens and between said first lens and said main mirror, said first and second lenses being centered on the axis of said main mirror and said second lens being spaced from said main mirror with an air space therebetween; a second plural element correcting refractor positioned to intercept and refract light reflected from said main mirror and to reflect said light back to said light aperture, said second correcting refractor being positioned centrally of said first refractor and comprising a third negative lens and a Mangintype secondary mirror, said secondary mirror comprising a fourth positive lens and a concave reflector in contact with said fourth lens, said secondary mirror being positioned so that light reflected from said main mirror will pass through said fourth lens and be reflected back by said concave reflector, said third lens being positioned between said fourth lens and said main mirror so as to intercept and refract light passing to and from said secondary mirror; and an air space between said third lens and said main mirror; said third lens being made of a material having a different index of refraction than the material of which said fourth lens is made, and said third lens and said secondary mirror coacting to direct light reflected by said reflector back toward said central aperture and being adapted to form an erect real image between said third lens and said main mirror light aperture.

Claim 3

A system according to claim 1 further including an ocular comprising a refractive system positioned to receive light rays reflected by said secondary mirror through said aperture for viewing said image.

Claim 4

A system according to claim 1 wherein said mirrors are spherical.

Claim 5

A system according to claim 1 comprising at least one element having a zonal refractive portion that forms part of said first correcting refractor and a central refractive portion that forms part of said second correcting refractor.

Claim 6

A system according to claim 1 comprising a first element having a zonal refractive portion that forms part of said first correcting refractor and a central refractive portion that forms said fourth lens, and a second element having a zonal refractive portion that forms another part of said first correcting refractor and a central refractive portion that forms said third lens, said central portion of said first element having a convex surface and said reflector comprising a reflective coating on said convex surface.

Claim 7

A system according to claim 1 wherein said main mirror is a Mangin mirror.

Claim 8

A system according to claim 1 wherein the surfaces of said correcting refractors through which light passes to and from said mirrors are all spherical.

Claim 9

A system accordinG to claim 1 further including a tubular diaphragm surrounding said aperture, said diaphragm extending from said main mirror towards said secondary mirror a distance sufficient for it to prevent direct access of light from said first correcting refractor to said aperture.

Claim 10

A system according to claim 2 wherein said ocular is movable toward and away from said second correcting refractor.

Claim 11

A system according to claim 2 wherein said ocular is centered on and movable along the axis of said main mirror.

Claim 12

A system according to claim 1 wherein said third and fourth lens are in contact with one another with no air space therebetween.

Claim 13

A system according to claim 1 wherein said fourth lens is a convex-convex lens and said third lens is a concave-concave lens.

Claim 14

A catadioptric system comprising: a concave main mirror having a central light aperture; a refractive entrance pupil for passing light to said main mirror from outside said system, said entrance pupil comprising a first annular positive lens centered on the axis of said main mirror; a first annular refractive corrector centered on said main mirror axis and positioned between said entrance pupil and said main mirror so as to intercept and refract rays of light passing from said entrance pupil to said main mirror, said first corrector being disposed adjacent to said entrance pupil and spaced from said main mirror with an air gap between said first refractor and said main mirror; a secondary Mangin-type mirror positioned centrally of said first annular positive lens and comprising a concave reflector and a second positive lens in contact with said reflector, said secondary mirror being positioned so that light rays reflected from said main mirror will pass through said second positive lens and be reflected back by said concave reflector; a second negative refractive corrector positioned centrally of said first corrector between said secondary concave mirror and said main mirror so as to intercept and refract light rays passing to and from said secondary mirror, said second corrector being made of a material having a different index of refraction than the material of which said second positive lens is made, said second corrector and said secondary mirror coacting to direct light reflected by said reflector back toward said central aperture and to form an erect real image between said second corrector and said main mirror, said first positive lens being made of a material having a different index of refraction than the material of which said first corrector is made.

Claim 15

A catadioptric system comprising: a concave main mirror having a central light aperture; a refractive entrance pupil for passing light to said main mirror from outside said system, said entrance pupil comprising a first annular positive lens centered on the axis of said main mirror; a first annular refractive corrector centered on said main mirror axis and positioned between said entrance pupil and said main mirror so as to intercept and refract rays of light passing from said entrance pupil to said main mirror, said first corrector being disposed adjacent to said entrance pupil and spaced from said main mirror with an air gap between said first refractor and said main mirror; a secondary Mangin-type mirror positioned centrally of said first annular positive lens and comprising a concave reflector and a second positive lens in contact with said reflector, said secondary mirror being positioned so that light rays reflected from said main mirror will pass through said second positive lens and be reflected back by said concave reflector; a second negative refractive corrector positioned centrally of said first corrector between said secondary concave mirror and said main mirror so as to intercept and refract light rays passing to and from said secondary mirror, said second corrector being made of a material having a different index of refraction than the material of which said second positive lens is made, said second corrector and said secondary mirror coacting to direct light reflected by said reflector back toward said central aperture and to form an erect real image between said second corrector and said main mirror, said first positive lens being made of a material having a different index of refraction than the material of which said first corrector is made.