Field curvature corrector
First Claim
1. An optical system which (a) forms an image of an object, (b) has a positive power, and (c) has a limiting principal ray associated with the system'"'"'s maximum field of view, said system comprising:
- at least one positive lens element; and
a field curvature corrector unit having a positive power and at least one aspheric surface;
wherein;
(i) the exact field curvature (EFC) of said field curvature corrector unit computed along at least one principal ray of the optical system is positive, where the exact field curvature of the field curvature corrector unit is given by;
space="preserve" listing-type="equation">EFC=-Σ
(n'"'"'-n)c/nn'"'"'where the summation is taken over the surfaces of the unit, and for each of said surfaces, n is the index of refraction on the object side of the surface, n'"'"' is the index of refraction on the image side of the surface, and c is the curvature of the surface at the intersection of the surface with the principal ray, c being positive if the center of curvature is on the image side of the surface; and
(ii) the system is free of lens elements having a negative power which provide substantial correction of the field curvature of the lens system.
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Accused Products
Abstract
A field curvature corrector is provided which has a positive power and a positive exact field curvature (EFC) value for at least one principal ray, where the EFC value is given by:
EFC=-Σ(n'"'"'-n)c/nn'"'"'
the summation being taken over the surfaces of the corrector, and for each of the surfaces, n is the index of refraction on the object side of the surface, n'"'"' is the index of refraction on the image side of the surface, and c is the curvature of the surface at the intersection of the surface with the principal ray, c being positive if the center of curvature is on the image side of the surface. By means of the corrector, the field curvature of a positive lens system can be corrected without the use of negative lens elements.
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Citations
26 Claims
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1. An optical system which (a) forms an image of an object, (b) has a positive power, and (c) has a limiting principal ray associated with the system'"'"'s maximum field of view, said system comprising:
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at least one positive lens element; and a field curvature corrector unit having a positive power and at least one aspheric surface; wherein; (i) the exact field curvature (EFC) of said field curvature corrector unit computed along at least one principal ray of the optical system is positive, where the exact field curvature of the field curvature corrector unit is given by;
space="preserve" listing-type="equation">EFC=-Σ
(n'"'"'-n)c/nn'"'"'where the summation is taken over the surfaces of the unit, and for each of said surfaces, n is the index of refraction on the object side of the surface, n'"'"' is the index of refraction on the image side of the surface, and c is the curvature of the surface at the intersection of the surface with the principal ray, c being positive if the center of curvature is on the image side of the surface; and (ii) the system is free of lens elements having a negative power which provide substantial correction of the field curvature of the lens system. - View Dependent Claims (3, 4, 5, 6, 7, 8)
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2. An optical system which (a) forms an image of an object, (b) has a positive power, and (c) has a limiting principal ray associated with the system'"'"'s maximum field of view, said system comprising:
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at least one positive lens element; and a field curvature corrector unit having a positive power and at least one aspheric surface; wherein; (i) the exact field curvature (EFC) of said field curvature corrector unit computed along at least one principal ray of the optical system is positive, where the exact field curvature of the field curvature corrector unit is given by;
space="preserve" listing-type="equation">EFC=-Σ
(n'"'"'-n)c/nn'"'"'where the summation is taken over the surfaces of the unit, and for each of said surfaces, n is the index of refraction on the object side of the surface, n'"'"' is the index of refraction on the image side of the surface, and c is the curvature of the surface at the intersection of the surface with the principal ray, c being positive if the center of curvature is on the image side of the surface; and (ii) the system is free of lens elements having a negative power, other than lens elements having a negative power which are associated with a color correcting doublet.
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9. An optical system which forms an image of an object, said system having an image end, an object end, and a limiting principal ray associated with the system'"'"'s maximum field of view, said system comprising:
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(a) a first unit at the object end which (i) forms an intermediate image of the object, (ii) has a positive power, and (iii) has an exit pupil, said first unit comprising a first field curvature corrector subunit and a second power subunit, said first field curvature corrector subunit having a positive power and comprising at least one aspheric surface; and (b) a second unit at the image end which reimages the intermediate image to form the image of the object, said second unit having an entrance pupil and a positive power; wherein the exact field curvature (EFC) of said first field curvature corrector subunit computed along at least one principal ray of the optical system is positive, where the exact field curvature of the field curvature corrector subunit is given by;
space="preserve" listing-type="equation">EFC=-Σ
(n'"'"'-n)c/nn'"'"'where the summation is taken over the surfaces of the subunit, and for each of said surfaces, n is the index of refraction on the object side of the surface, n'"'"' is the index of refraction on the image side of the surface, and c is the curvature of the surface at the intersection of the surface with the principal ray, c being positive if the center of curvature is on the image side of the surface. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A compounded magnifier comprising an objective lens element having a positive power, an eyepiece lens element having a positive power, and a field curvature corrector element having a positive power, wherein the exact field curvature (EFC) of said field curvature corrector element computed along at least one principal ray of the magnifier is positive, where the exact field curvature of the field curvature corrector element is given by:
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space="preserve" listing-type="equation">EFC=-Σ
(n'"'"'-n)c/nn'"'"'where the summation is taken over the surfaces of the element, and for each of said surfaces, n is the index of refraction on the object side of the surface, n'"'"' is the index of refraction on the image side of the surface, and c is the curvature of the surface at the intersection of the surface with the principal ray, c being positive if the center of curvature is on the image side of the surface. - View Dependent Claims (22, 23, 24, 25, 26)
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Specification