Color-corrected optical systems and method of selecting optical materials therefor
AssigneeLockheed Missiles & Space Company, Inc.
InventorsRomeo I. Mercado, Paul N. Robb
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Abstract
A method is described for selecting optical materials to use in designing color-corrected optical systems. Various dioptric, catadioptric and anamorphic optical systems are described, which use only two different types of optical materials to obtain precise axial color correction at three, four or five wavelengths (depending upon the particular optical materials), with only very small chromatic aberration occurring at wavelengths between the precisely color-corrected wavelengths. Examples of color-corrected lens systems comprising more than two glasses are also described.
Claims28
A method of manufacturing an optical system that is color-corrected at a number of discrete wavelengths, said manufacturing method including a process for selecting compatible optical materials from among available optical materials for fabricating optical elements of said system, each of said available optical materials having a characteristic dispersive power, said process for selecting compatible optical materials comprising:
- a) representing the dispersive power of each available optical material by a polynomial expression in a variable that is a function of wavelength, the polynomial expression for each available optical material being of a degree that is numerically one less than the number of wavelengths for which color correction of said system is required;
- b) comparing a ratio of coefficients in the polynomial expression for one of said available optical materials with corresponding ratios of coefficients in the polynomial expressions for others of said available optical materials;
- c) identifying particular optical materials from among said others of said available optical materials for which said corresponding ratios of coefficients are substantially equal to said ratio of coefficients for said one of said available optical materials;
- and
- d) choosing said compatible optical materials from among those particular optical materials for which said corresponding ratios of coefficients are substantially equal, said compatible optical materials so chosen being used for fabricating said optical elements as specified in a design form that provides color correction for said system at said discrete wavelengths.
An optical system color-corrected at more than three discrete wavelengths, said system comprising a plurality of optical elements, at least one of said elements being made of a first optical material and at least one other of said elements being made of a second optical material, said first and second optical materials having different indices of refraction, the indices of refraction of said first and second optical materials being related to each other so that said elements of said system can coact to produce a substantially identical effect on said more than three discrete wavelengths.
A lens doublet that is color-corrected at more than three discrete wavelengths, each lens element of said doublet being made of a different optical material in accordance with a design form such that said doublet causes zero paraxial marginal ray height at a focal surface of said doublet for said discrete wavelengths.
A lens doublet that is color-corrected at more than four discrete optical wavelengths, each lens element of said doublet being made of a different optical material in accordance with a design form such that said doublet causes zero paraxial marginal ray height at a focal surface of said doublet for said discrete wavelengths.
In a process for manufacturing an optical system that is color-corrected at a plurality of discrete wavelengths, said process including selection of compatible optical materials from which optical elements of said system are made, said optical elements being configured and disposed with respect to each other so that said system is color-corrected at said wavelengths, each of said optical materials having a characteristic dispersive power that is a function of wavelength, said optical materials being selected by a method comprising:
- a) representing the dispersive power of each optical material by a polynomial expression in a variable that is a function of wavelength;
- b) comparing a ratio of coefficients in a polynomial expression for one of said optical materials with corresponding ratios of coefficients in the polynomial expressions for others of said optical materials;
- c) identifying particular optical materials from among said others of said optical materials for which said corresponding ratios of coefficients are substantially equal to said ratio of coefficients for said one optical material;
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- d) choosing optical materials for making said optical elements of said system from among those particular optical materials for which said corresponding ratios of coefficients are substantially equal.
A dioptric optical system color-corrected at three discrete wavelengths, said system comprising lens elements made of only two optical materials, namely, Schott FK51 glass and Schott K51 glass, said lens elements being configured and disposed with respect to each other in accordance with a design form such that paraxial marginal ray height at a focal surface of said system is zero for said three discrete wavelengths.
A dioptric optical system color-corrected at four discrete wavelengths, said system comprising lens elements made of only two optical materials, namely, Corning-France 486817 glass and Ohara LAK14 glass, said lens elements being configures and disposed with respect to each other in accordance with a design form such that paraxial marginal ray height at a focal surface of said system is zero for said four discrete wavelengths.
A dioptric optical system color-corrected at five discrete wavelengths, said system comprising lens elements made of only two optical materials, namely, Schott PK51 glass and Hoya LAC7 glass, said lens elements being configured and disposed with respect to each other in accordance with a design form such that paraxial marginal ray height at a focal surface of said system is zero for said five discrete wavelengths.
A method of selecting optical materials from among available optical materials for use in fabricating optical elements of an optical system that is color-corrected at a number of discrete wavelengths in a particular wavelength region, said elements of said system being configured and disposed with respect to each other in accordance with a design form such that said elements produce a substantially identical effect on said discrete wavelengths, each available optical material having a characteristic dispersive power D(.lambda.) represented by an nth degree polynomial in a variable .omega.(.lambda.), said polynomial being of the form:
- ##EQU83## where .omega.(.lambda.)=.delta..lambda./(1+.alpha..delta..lambda.), where .delta..lambda. represents change in wavelength with respect to a base wavelength and .alpha. is a constant that is substantially independent of optical material;
- and where .eta..sub.i are coefficients of terms in said variable .omega.(.lambda.), said polynomial having n terms in said variable .omega.(.lambda.), said method of selecting optical materials comprising use of a digital computer for:
- a) calculating said coefficients .eta..sub.i for a plurality of specified wavelengths in said wavelength region for each available optical material;
- b) calculating ratios .eta..sub.i /.eta..sub.j, where j.noteq.i, for each available optical material;
- c) comparing corresponding ratios .eta..sub.i /.eta..sub.j for said available optical materials;
- and
- d) identifying candidate optical materials for use in fabricating said elements of said system from among those available optical materials for which said corresponding ratios .eta..sub.i /.eta..sub.j are substantially equal.
Dependencies are inferred from the claim text.