Five component zoom lens

Claim 1

In an objective optical system of the type in which a first group constituting a portion of the objective system, facing an object to be photographed and having a converging performance is moved for focusing, the first group comprising a negative component movable toward the object when focusing from the infinity to a finite distance and a positive component behind the negative component and movable toward the object a smaller amount than the negative component when focusing from the infinity to a finite distance; a zoom system comprising a second negative group behind said first group and stationary when focusing but movable mainly for zooming performance, and a third positive group behind the second negative group and stationary when focusing but movable for maintaining an image point at a definite position; a relay system comprising a fourtH negative group behind the zoom system providing a definite position relative to the image point and a fifth positive group behind the fourth group providing a definite position relative to the image point; the system further including a light dividing member behind the zoom system and in the vicinity of the relay system, the light dividing member providing a definite position relative to the image point and leading the light rays incident into the objective to a finder; and wherein the negative component of the first group consists of a doublet member cementing a positive meniscus element concave toward an object point with a negative biconcave element; the positive component of the first group consists of a first doublet member cementing a positive biconvex element with a negative meniscus element concave toward the object point, a second intermediate doublet member cementing a negative meniscus element convex toward the object point with a positive biconvex element and a third single member of a positive meniscus element convex toward the object point; the front member of the second group is a single member of a negative meniscus element convex toward the object point, the rear member of the second group is a doublet member cementing a negative biconcave element with a positive meniscus element convex toward the object point; the front member of the third group is a single member of a positive biconvex element, the rear member of the third group is a doublet member cementing a positive biconvex element with a negative meniscus element concave toward the object point; the fourth group comprises a front member of a single negative biconcave element and the rear light dividing member of parallel plane surfaces; the fifth group comprises the front member of a single positive biconvex element and the rear member of a doublet cementing a positive biconvex element with a negative biconcave element; and the objective optical system has the following data: aperture ratio f1.8 focal length f 9.5 about 50mm. R1 -79.1 d1 3.9 n1 1.74077 v1 27.7 R2 -56.0 d2 0.8 n2 1.62041 v2 60.3 R3 110.61 d3 6.3 R4 131.135 d4 11.2 n3 1.5168 v3 64.2 R5 -40.0 d5 1.6 n4 1.69895 v4 30.0 R6 -59.05 d6 0.2 R7 85.4 d7 1.4 n5 1.76182 v5 26.5 R8 39.5 d8 9.1 n6 1.6516 v6 58.5 R9 -260.753 d9 0.1 R10 52.824 d10 3.0 n7 1.6516 v7 58.5 R11 90.946 d11 1.8144 about 27.8144 R12 345.3 d12 1.0 n8 1.717 v8 48.2 R13 16.261 d13 5.4 R14 -30.253 d14 0.7 n9 1.5168 v9 64.2 R15 18.2 d15 3.7 n10 1.72825v10 28.3 R16 130.440 d16 39.4096 about 2.0358 R17 60.0 d17 2.7 n11 1.6583 v11 57.3 R18 -51.315 d18 0.1 R19 33.64 d19 6.3 n12 1.6583 v12 57.3 R20 16.78 d20 0.8 n13 1.72342 v13 38.0 R21 -95.933 d21 1.8788 about 13.2526 R22 -28.8 d22 0.8 n14 1.51454 v14 54.6 R23 21.047 d23 1.2 R24 infinity d24 9.0 n15 1.57515 v15 41.3 R25 infinity d25 9.8 R26 148.995 d26 6.9 n16 1.62230 v16 53.1 R27 19.704 d27 0.4 R28 18.9 d28 4.9 n 1.66755 v17 41.9 R29 14.29 d29 1.2 n18 1.80518 v18 25.5 R30 34.322 Wherein R denotes radius of curvature, d-center thickness of the lens and lens spacing, v-Abbe number of the glass used, and n-refractive index of the glass used.