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Catadioptric imaging system with dioptric assembly of the petzval type
| Details |
Inventors: Mercado, Romeo I.;
Assignee: Lockheed Missiles & Space Company, Inc. (Sunnyvale, CA)
Primary Examiner: Corbin; John K.
Assistant Examiner: Dzierzynski; P. M.
Attorney, Agent or Firm: Morrissey; John J.
A catadioptric optical imaging system comprises a dioptric assembly (20) and a catoptric assembly (21), which are positioned with respect to each other to form an imaging system of long focal length. The dioptric assembly (20) comprises two confocal paraboloidal mirrors (22, 23) arranged to form a telescope of the Mersenne type. The catoptric assembly (21) comprises lens elements arranged in two groups, viz., a field group (25) and a relay group (26), which are coaxially disposed with respect to the dioptric assembly (20). Only two different optical materials, viz., calcium fluoride crystal and Hoya LAC7 glass, are used in making the lens elements of the dioptric assembly (20). The dioptric assembly (20) is color-corrected at five wavelengths and has only negligible secondary and higher-order spectra in a wavelength band extending from the ultraviolet region to the near infrared region of the optical spectrum. |
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DETAILED DESCRIPTION I claim: 1.
A catadioptric imaging system comprising a catoptric assembly and a dioptric assembly, said catoptric assembly comprising a primary mirror for gathering light from a distant object and a secondary mirror for reflecting the gathered light as a nonconverging beam along an optic axis of the system, said dioptric assembly comprising a lens system of the Petzval type positioned on said optic axis, said lens system consisting of a plurality of lens elements of only two different kinds of optical materials, said plurality of lens elements coacting with each other so as to bring paraxial marginal rays passing through said lens system to a common focus at five wavelengths, said lens system thereby being color-corrected at exactly five wavelengths.
2.
The catadioptric imaging system of claim 1 wherein said optical materials comprise calcium fluoride crystal and a glass having a refractive index of approximately 1.
65 and an Abbe number of approximately 58.
15 at a wavelength of 0.
546 micron.
3.
The catadioptric imaging system of claim 2 wherein said glass is Hoya LAC7 glass.
4.
The catadioptric imaging system of claim 1 wherein said lens system comprises a first lens element, a second lens element, a third lens element, a fourth lens element and a fifth lens element, said first, second, third, fourth and fifth lens elements being consecutively disposed along said optic axis, said first lens element being made of calcium fluoride crystal, said second lens element being made of Hoya LAC7 glass, said third lens element being made of calcium fluoride crystal, said fourth lens element being made of Hoya LAC7 glass, and said fifth lens element being made of Hoya LAC7 glass.
5.
The catadioptric imaging system of claim 4 wherein said first lens element has a surface with a positive radius of curvature of approximately 0.
0433 times the focal length of the system and a surface with a negative radius of curvature of approximately 0.
0482 times the focal length of the system, said second lens element has a surface with a negative radius of curvature of approximately 0
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