Compact seven element zoom lens with optical compensation

Claim 2

A zoom lens the optical portion of which consists, in an axially aligned arrangement from the long conjugate side to the short conjugate side, of: a negative lens element having a convex surface toward said long conjugate; a positive second lens element having a strongly curved surface toward said long conjugate and a weaker surface toward said short conjugate; a negative third lens element with a weakly curved surface toward said long conjugate and a stronger surface toward said short conjugate; a positive fourth lens element with a weakly curved surface toward said long conjugate and a stronger surface toward said short conjugate; a positive fifth lens element having a strong curvature toward said long conjugate and a weaker surface toward said short conjugate; a negative sixth lens element; and a positive seventh lens element with a weakly curved surface toward said long conjugate and a stronger surface toward said short conjugate.

Claim 3

The zoom lens described in claim 1, the mechanical portion of which includes; means for permitting said second and fourth lens elements to move axially between said first and fifth lens elements without changing the separation between said second and fourth lens elements and without changing the separation between said first and third lens elements.

Claim 4

The zoom lens described in claim 1, wherein said first, second, third, and fourth lens elements function as a zoom group to change the focal length of said zoom lens and said fifth, sixth, and seventh lens elements function as an objective group, the lens powers of said zoom group selected so light emerging therefrom will be refracted to a focus at a finite distance behind said zoom group, and the powers and shapes of said objective group selected to balance the aberrations in said focused light entering said objective group.

Claim 5

The zoom lens described in claim 1, wherein the movable positive lens elements of the zoom group have Abbe dispersion numbers greater than 55.

Claim 6

The zoom lens described in claim 1, wherein the overall length of said zoom lens from the first refracting surface to the last refracting surface is less than four times its shortest focal length.

Claim 7

The zoom lens described in claim 1 wherein said positive second lens element and said positive fourth lens element are movable conjointly so as to substantially change the effective focal length of said zoom lens and said negative first lens element is movable independently of the other said lens elements to focus said zoom lens.

Claim 8

A zoom lens the optical portion of which consists, in an axially aligned arrangement from the long conjugate side to the short conjugate side, of: a meniscus negative first lens element having its convex side toward said long conjugate; a positive second lens element having a convex surface toward said long conjugate and a weaker surface toward said short conjugate; a negative third lens element with its weaker surface toward said long conjugate and a concave surface toward said short conjugate; a positive fourth lens element with its weaker surface toward said long conjugate and a convex surface toward said short conjugate; a positive fifth lens element having a strong surface toward said long conjugate and a weaker surface toward said short conjugate; a biconcave negative sixth lens element and a positive seventh lens element with its weaker surface toward said long conjugate and a convex surface toward said short conjugate, said optical portion having an overall length from its first refracting surface to its last refracting surface less than four times its shortest focal length.

Claim 9

A zoom lens the optical portion of which consists, in an axially aligned arrangement from the long conjugate side to the short conjugate side, of: a meniscus negative first lens element having its convex side toward said long conjugate; a positive second lens element having a convex surface toward said long conjugate and a weaker surface toward said short conjugate; a negative third lens element with its weaker surface toward said long conjugate and a concave surface toward said short conjugate; a positive fourth lens element with its weaker surface toward said long conjugate and a convex surface toward said short conjugate; a positive fifth lens element having a strong surface toward said long conjugate and a weaker surface toward said short conjugate; a biconcave negative sixth lens element and a positive seventh lens element with its weaker surface toward said long conjugate and a convex surface toward said short conjugate, said optical portion having an overall length from its first refracting surface to its last refracting surface less than four times its shortest focal length.

Claim 10

A zoom lens for refracting an image of a subject located in front of it to a focal plane at its rear, the optical portion of which consists of: a negative lens element, stationary with respect to said focal plane; two positive lens elements, one disposed on each side of said negative lens element along a common axis therewitH and both having their stronger surfaces facing in opposite directions, said two positive lens elements movable axially with respect to said negative lens element; a meniscus negative lens element disposed on said axis forward of said two positive lens elements; objective lens means consisting of three lens elements disposed on said axis rearward of said two positive lens elements, said two positive lens elements movable conjointly so as to substantially change the focal length of said zoom lens without shifting said image from said focal plane, said zoom lens having an overall length from its first refracting surface to its last refracting surface less than four times its shortest focal length.

Claim 11

A zoom lens for refracting an image of a subject located in front of it to a focal plane at its rear, the optical portion of which consists of: a negative lens element, stationary with respect to said focal plane; two positive lens elements, one disposed on each side of said negative lens element along a common axis therewitH and both having their stronger surfaces facing in opposite directions, said two positive lens elements movable axially with respect to said negative lens element; a meniscus negative lens element disposed on said axis forward of said two positive lens elements; objective lens means consisting of three lens elements disposed on said axis rearward of said two positive lens elements, said two positive lens elements movable conjointly so as to substantially change the focal length of said zoom lens without shifting said image from said focal plane, said zoom lens having an overall length from its first refracting surface to its last refracting surface less than four times its shortest focal length.

Claim 12

The zoom lens described in claim 8, wherein said negative lens elements and said two positive lens elements coact to form a real image at a finite conjugate to the rear of said zoom lens and said objective triplet refracts said real image to a focus at said focal plane.

Claim 13

The zoom lens described in claim 8, wherein said three lens elements of said objective lens means are: a positive lens element with a substantially stronger curvature on its forward refracting surface than on its rearward refracting surface; a biconcave negative lens element with a weaker curvature on its forward refracting surface than on its rearward refracting surface; and a last positive lens element with a weak curvature on its forward refracting surface, said lens elements of said objective lens means arranged in the foregoing order with said last positive lens element closest to said focal plane.

Claim 14

The zoom lens described in claim 8, wherein said two positive lens elements are: a positive lens element on the forward side of said negative lens element having a convexly curved refracting surface toward the front of said zoom lens and a weak refracting surface toward the rear of said zoom lens; and a positive lens element on the rearward side of said negative lens element having a convexly curved refracting surface toward the rear of said zoom lens and a weakly curved refracting surface toward the front of said zoom lens.

Claim 15

The zoom lens described in claim 8, the mechanical portion of which includes: means for retaining a predetermined spacing arrangement between said two positive lens elements and for moving them as a unit relative to the other lens elements to change the focal length of said zoom lens.

Claim 16

The zoom lens described in claim 8, wherein said movable plurality of positive lens elements have Abbe dispersion numbers greater than 55.

Claim 17

An optically compensated zoom objective lens having the design parameters for a unit focal length, F, represented in the following table:

Claim 18

An optically compensated zoom objective lens having the design parameters for a unit focal length, F, represented in the following table: