Reverse telephoto lens
AssigneeEastman Kodak Company
InventorJohn D. Griffith
Life of this patent
Estimating the term…
Abstract
A reverse telephoto lens includes a front negative group of lens components having a front component with greater than normal separation from a rear positive group of lens elements. Preferably, the front negative group also includes a rear positive component that is meniscus concave to the front.
Claims21
A reverse telephoto lens comprising, in order from a front, object side of the lens to a rear, image side of the lens:
- a front negative group of lens components including a front negative component and a rear positive component, separated by a first airspace A1;
- a rear positive group of lens elements separated from the front negative group by a second airspace A2;
- said rear positive group of lens elements including at least two positive lens elements and a negative lens element located therebetween and
- a stop located in the second airspace,
- wherein the distance between the front negative component and the rear positive group is at least 2.5 times the focal length of the lens, and wherein A1.ltoreq.A2.
A reverse telephoto lens comprising, in order from the object side, a negative meniscus element with a convex side toward the object, a positive meniscus element with a concave side toward the object, the aperture stop, a positive biconvex element, a negative biconcave element, and a positive biconvex element, said lens system satisfying the following conditions:
- ##EQU7## where V.sub.i is the Abbe number of element i,
- efi.sub.i is the focal length of element i,
- efl is the focal length of the lens,
- X.sub.i is the bending of element i,
- d.sub.2 is the air space between the first and second element,
- d.sub.4 is the air space between the second element and the aperture stop,
- d.sub.5 is the air space between the aperture stop and the third element, and distances are in millimeters.
A reverse telephoto lens comprising, in order from the object side, a negative meniscus element with convex side toward the object, a positive meniscus element with concave side toward the object, the aperture stop, a cemented doublet comprising a positive biconvex element and a negative biconcave element, and a positive biconvex element, said lens system satisfying the following conditions:
- 45.ltoreq.V.sub.1 .ltoreq.55 (1)
- 30.ltoreq.V.sub.2 .ltoreq.55 (2)
- 4.ltoreq. V.sub.3 .ltoreq.55 (3)
- 28.ltoreq.V.sub.4 .ltoreq.33 (4)
- 39.ltoreq.V.sub.5 .ltoreq.65 (5)
- where V.sub.i is the Abbe number of element i.
A reverse telephoto lens comprising, in order from the object side, a negative element, a positive meniscus element with concave side toward the object, an aperture stop, a positive biconvex element having an aspheric rear surface with a sag ##EQU8## a negative biconcave element, and a positive element, where Y is the radius of the aspheric surface, k is the conic constant, and C is the curvature, and said lens system satisfying the following conditions:
- ##EQU9## where V.sub.i is the Abbe number of element i,
- efl.sub.i is the focal length of element i,
- efl is the focal length of the lens,
- X.sub.i is the bending of element i,
- d.sub.2 is the air space between the first and second element,
- d.sub.4 is the air space between the second element and the aperture stop,
- d.sub.5 is the air space between the aperture stop and the third element,
- k is the conic constant of the rear surface of the third element and all distances are in millimeters.
A reverse telephoto lens comprising, in order from the object side, a negative meniscus element with convex side towards the object, a positive meniscus element with concave side toward the stop, the aperture stop, a positive biconvex element having an aspheric rear surface with a sag ##EQU10## a negative biconcave element, and a positive biconvex element, where Y is the radius, k is the conic constant, and C is the curvature of the aspheric surface, and the lens having the following numerical values:
- ______________________________________ efl = 5.40 F number = 2.84 Full field = 58.8.degree. Back focal length = 6.29 object distance = 2400 mm ______________________________________ R1 = 18.73 D1 = 1.50 N1 = 1.51680 V1 = 64.2 R2 = 5.29 D2 = 3.72 R3 = -8.77 D3 = 4.00 N3 = 1.69680 V3 = 55.5 R4 = -8.50 D4 = 11.85 R5 = 0.00 D5 = 1.55 R6 = 6.25 D6 = 3.00 N6 = 1.72800 V6 = 50.6 c7 = -0.107813 D7 = 1.00 k7 = -5.385944 R8 = -5.94 D8 = 1.76 N8 = 1.80518 V8 = 25.4 R9 = 5.94 D9 = 0.85 R10 = 19.70 D10 = 1.93 N10 = 1.77250 V10 = 49.6 R11 = -6.20 D11 = 1.61 R12 = 0.00 D12 = 3.02 N12 = 1.54430 V12 = 70.2 R13 = 0.00 D13 = 1.50 R14 = 0.00 D14 = 0.76 N14 = 1.53338 V14 = 61.3 R15 = 0.00 D15 = 0.74 ______________________________________
- said lens being followed by a birefringent blur filter and array photodetector cover glass, as indicated by R.sub.12 -R.sub.15 in the table, and being focusable by adjusting D5 and D11 such that their sum is constant.
A reverse telephoto lens comprising, in order from the object side, a negative meniscus element with convex side towards the object, a positive meniscus element with concave side toward the stop, the aperture stop, a positive biconvex element, a negative biconcave element, and a positive biconvex element, the lens having the following numerical values:
- ______________________________________ efl = 5.40 F number = 2.84 Full field = 60.degree. Back focal length = 6.28 object distance = 2400 mm ______________________________________ R1 = 91.28 D1 = 1.50 N1 = 1.56384 V1 = 60.8 R2 = 4.70 D2 = 4.20 R3 = -22.94 D3 = 4.00 N3 = 1.69680 V3 = 55.5 R4 = -7.68 D4 = 6.77 R5 = 0.00 D5 = 2.72 R6 = 6.62 D6 = 2.05 N6 = 1.69680 V6 = 55.5 R7 = -35.09 D7 = 0.75 R8 =-20.53 D8 = 1.50 N8 = 1.80518 V8 = 25.4 R9 = 4.41 D9 = 0.74 R10 = 7.92 D10 = 2.00 N10 = 1.77250 V10 = 49.6 R11 = -7.92 D11 = 1.56 R12 = 0.00 D12 = 3.02 N12 = 1.54430 V12 = 70.2 R13 = 0.00 D13 = 1.50 R14 = 0.00 D14 = 0.76 N14 = 1.53338 V14 = 61.3 R15 = 0.00 D15 = 0.78 ______________________________________
- said lens being followed by a birefringent blur filter and array photodetector cover glass, as indicated by R.sub.12 -R.sub.15 in the table, and being focusable by adjusting D5 and D11 such that their sum is constant.
Dependencies are inferred from the claim text.