Compact telephoto zoom lens system

Claim 2

A compact telephoto zoom lens system comprising a variator unit including a first lens group having a positive focal length and serving as a focusing member, a second lens group having a negative focal length and serving mainly as a variator having a variable power function, and a third lens group having a positive focal length and serving as a compensator for maintaining an image surface constant, and a relay lens unit following said variator unit, said first lens group being composed of a positive lens and a cemented lens assembly of a negative meniscus lens having a convex side direction toward the object and a positive lens, said second lens group being composed of a negative lens and a cemented lens assembly of a biconcave negative lens and a positive lens, said third lens group being composed of a cemented lens assembly of a biconvex positive lens and a negative meniscus lens, said relay lens unit being composed of a fourth lens group a having a positive lens with a large-curvature convex surface directed toward the object and a negative lens, and a fourth lens group b spaced from said fourth lens group a and having a positive meniscus lens, a biconcave negative lens, and a biconvex positive lens, said telephoto zoom lens satisfying the following conditions: ##EQU2## where f min is the focal length of the overall system at the minimum focal length, f I is the focal length of the first lens group, f I .II is the resultant focal length of the first and second lens groups at the minimum focal length, f I-III is the resultant focal length of the first through third lens groups at the minimum focal length, f I-IVa is the resultant focal length of the first group through fourth lens group a at the minimum focal length, f IVb is the focal length of the fourth lens group b, d 19 is the aerial space between the positive meniscus lens on the object side and the biconcave lens in the fourth lens group b, r 19 is the radius of curvature of the image side surface of the positive meniscus lens on the object side in the fourth lens group b, r 20 is the radius of curvature of the object side surface of the biconcave lens in the fourth lens group b, N 20 is the refractive index of the biconcave lens in the fourth lens group b at d-line, d 21 is the aerial space between the biconcave lens and final biconvex lens in the fourth lens group b, and N 22 is the refractive index of the final biconvex lens in the fourth lens group b at d-line.

Claim 5

The zoom lens system of claim 1 satisfying the following chart: ______________________________________ aperture ratio 1:4.1 f = 72.1-204.0 f.sub.B = 42.74 ω= 17.3° -9.5° No. r d N ν ______________________________________ 1 122.000 4.50 1.48749 70.1 2 946.000 0.15 3 63.385 2.70 1.80518 25.4 4 44.014 9.30 1.48749 70.1 5 -1800.000 1.83-41.04 (variable) 6 455.000 1.60 1.77250 49.7 7 37.630 4.80 8 -40.196 1.50 1.72916 54.7 9 40.196 4.50 1.80518 25.4 10 -173.534 32.97-1.32 (variable) 11 139.000 5.80 1.56873 63.2 12 -34.964 1.70 1.80518 25.4 13 -62.130 16.20-8.64 (variable) 14 32.540 4.70 1.56873 63.2 15 413.302 2.00 16 -175.741 2.30 1.80518 25.4 17 1889.365 36.82 18 45.225 3.40 1.75520 27.5 19 135.000 4.70 20 -24.470 1.70 1.83400 37.2 21 73.400 0.25 22 53.550 5.80 1.58921 41.1 23 -45.225 ______________________________________ ##STR10## ##STR11## ##STR12## ##STR13## ##STR14## ##STR15## ##STR16## ##STR17## N.sub.20 = 1.834 ##STR18## N.sub.20 -N.sub.22 = 0.245 ______________________________________ where f is the focal length of said zoom lens system, ω is the half view angle, r is the radius of curvature, d is the thickness of the lens element or the space between adjacent lens elements, N is the refractive index at d-line, and ν is the Abbe number.