Image focusing system

Claim 2

An image focusing system comprising two lens assemblies defining an optical axis; and a reflecting element for folding said optical axis of the system and disposed between said lens assemblies; wherein each lens assembly comprises a plurality of lens elements having optical surfaces of which at least some are air-to-glass surfaces, said optical surfaces being arranged in a first group having a negative power and being disposed closer to the reflecting element and in a second group having a positive power and disposed further from the reflecting element, the ratio of the powers of the second group to the first group being within the range from -1:1 and -3:1, and wherein all said air-to-glass surfaces are concave towards said reflecting element.

Claim 3

An image focusing system according to claim 1 wherein in each assembly the lens element which is closest to the reflecting element is a meniscus.

Claim 4

An image focusing system according to claim 1 wherein said first group of optical surfaces is provided by a meniscus and a cemented doublet, the meniscus being closer to the reflecting element than said doublet.

Claim 5

An image focusing system comprising two lens assemblies defining an optical axis and a reflecting element for folding said optical axis and being disposed along said optical axis between the two lens assemblies, each lens assembly comprising the elements a, b, c, d and e substantially in accordance with the following: ______________________________________ Axial thick- Sur- Radii of ness or mean Abbe Element face curvature separation RI V. value ______________________________________ S.sub.1 4.56 a d.sub.1 = .577 1.5176 64.2 S.sub.2, S.sub.3 6.10 b d.sub.2 = .413 1.6922 54.7 S.sub.4 10.94 d.sub.3 = .306 Air S.sub.5 9.74 c d.sub.4 = .322 1.6922 54.7 S.sub.6, S.sub.7 22.31 d d.sub.5 = .250 1.5488 45.6 S.sub.8 2.88 d.sub.6 = .157 Air S.sub.9 3.30 e d.sub.7 = .324 1.5900 61.3 S.sub.10 4.91 ______________________________________ kp=0.0826 kn=-0.0620

Claim 6

An image focusing system comprising two lens assemblies defining an optical axis and a reflecting element for folding said optical axis and being disposed along said optical axis between the two lens assemblies, each lens assembly comprising the elements a, b, c, d and e substantially in accordance with the following: ______________________________________ Axial thick- Sur- Radii of ness or mean Abbe Element face curvature separation RI V. value ______________________________________ S.sub.1 4.56 a d.sub.1 = .577 1.5176 64.2 S.sub.2, S.sub.3 6.10 b d.sub.2 = .413 1.6922 54.7 S.sub.4 10.94 d.sub.3 = .306 Air S.sub.5 9.74 c d.sub.4 = .322 1.6922 54.7 S.sub.6, S.sub.7 22.31 d d.sub.5 = .250 1.5488 45.6 S.sub.8 2.88 d.sub.6 = .157 Air S.sub.9 3.30 e d.sub.7 = .324 1.5900 61.3 S.sub.10 4.91 ______________________________________ kp=0.0826 kn=-0.0620

Claim 7

An image focusing system comprising two lens assemblies defining an optical axis and a reflecting element for folding said optical axis and being disposed along the optical axis between the two lens assemblies, each lens assembly comprising the elements a, b, c and d substantially in accordance with the following: ______________________________________ axial thick- Sur- Radii of ness or mean Abbe Element face curvature separation RI V. value ______________________________________ S.sub.1 4.18 a d.sub.1 = .614 1.6610 57.0 S.sub.2 10.82 d.sub.2 = .683 Air S.sub.3 9.56 b d.sub.3 = .297 1.5910 61.0 S.sub.4, S.sub.5 35.39 c d.sub.4 = .140 1.5505 45.3 S.sub.6 3.06 d.sub.5 = .218 Air S.sub.7 4.96 d d.sub.6 = .202 1.5116 64.2 S.sub.8 7.09 ______________________________________ kp=0.1006 kn=0.0850

Claim 8

An image focusing system comprising two lens assemblies defining an optical axis and a reflecting element for folding said optical axis and being disposed along the optical axis between the two lens assemblies, each lens assembly comprising the elements a, b, c and d substantially in accordance with the following: ______________________________________ axial thick- Sur- Radii of ness or mean Abbe Element face curvature separation RI V. value ______________________________________ S.sub.1 4.18 a d.sub.1 = .614 1.6610 57.0 S.sub.2 10.82 d.sub.2 = .683 Air S.sub.3 9.56 b d.sub.3 = .297 1.5910 61.0 S.sub.4, S.sub.5 35.39 c d.sub.4 = .140 1.5505 45.3 S.sub.6 3.06 d.sub.5 = .218 Air S.sub.7 4.96 d d.sub.6 = .202 1.5116 64.2 S.sub.8 7.09 ______________________________________ kp=0.1006 kn=0.0850

Claim 9

In an image focusing system for a reprographic camera, the image focusing system being capable of operating at a relative aperture of f/11 and at a field angle of at least 40°, the improvement wherein said image focusing system comprises two lens assemblies for defining an optical axis and a reflecting element for folding said optical axis, said reflecting element being arranged between said lens assemblies along said optical axis, each lens assembly comprising a plurality of lens elements of which the optical surfaces consist of a first and a second group, the power of the first group being negative and the power of the second group being positive and the ratio between the powers of said second and first groups being in the range -1:1 and -3:1.

Claim 10

In an image focusing system for a reprographic camera, the image focusing system being capable of operating at a relative aperture of f/11 and at a field angle of at least 40°, the improvement wherein said image focusing system comprises two lens assemblies for defining an optical axis and a reflecting element for folding said optical axis, said reflecting element being arranged between said lens assemblies along said optical axis, each lens assembly comprising a plurality of lens elements of which the optical surfaces consist of a first and a second group, the power of the first group being negative and the power of the second group being positive and the ratio between the powers of said second and first groups being in the range -1:1 and -3:1.

Claim 11

An image focusing system according to claim 6 in which said lens elements provide a plurality of air-to-glass surfaces, all of which are concave to the said reflecting element.