Photographic objective of continuously variable focal length

Claim 2

Photographic objectives of continuously variable focal length, consisting of four lens-groups the first of which (A) is of converging, the second (B) of diverging, the third (C) of diverging, and the fourth (D) of converging refractive power, the change in the focal length of the objective being effected in the manner that the two diverging lens groups (B,C) are displaced along the optical axis relative to each other and relative to the two converging lens groups (A,D), the two diverging lens groups (B,C) consisting together of at least four members at least one of which members has a chromatically acting cemented surface, characterized by the fact that the refractive powers of the movable lens groups (B,C) are so distributed that the variable air space (d 14 ) present between the lens groups (C) and (D) is larger in the wide-angle position than in any other focal-length postion and is smaller in amount by a factor of 0.3 than the shortest focal length (f 1 ) of the objective, and that the fourth multilens lens group (D) contains in the front part, consisting of the lenses IX to XII at least one laminated member whose cemented surface is of negative refractive power, and that this laminated member is followed, at a distinct distance from it, by a diverging meniscus (lens XIII) whose concave surface is curved towards the image plane and whose focal length is larger in amount by at least a factor of 3 and at most a factor of 5 than the longest focal length (f 3 ) of the objective.

Claim 3

Photographic objectives in accordance with claim 1, characterized by the fact that the first converging lens group (A) consists of two members only the first of which contains a chromatically acting cemented surface, and that the fourth converging lens group (D) is of multilens constructions and has at least one laminated member whose cemented surface is of negative refractive power.

Claim 4

A photographic objective according to claim 1, characterized by the data contained in the following table: __________________________________________________________________________ Data Table Refractive Abbe No. for the index d-line Lens Radii Vertex distance n.sub.d ν.sub.d __________________________________________________________________________ I r.sub.1 = +89.123 d.sub.1 = 3.8 1.80517 25.43 II r.sub.2 = +53.858 d.sub.2 = 7.8 1.51680 64.17 r.sub.3 = +199.522 A d.sub.3 = 0.1 III r.sub.4 = +81.163 d.sub.4 = 7.0 1.52341 51.49 r.sub.5 = -956.760 (1.200) d.sub.5 = 31.370 (48.326) IV r.sub.6 = -446.700 d.sub.6 = 1.6 1.69100 54.71 r.sub.7 = +31.851 d.sub.7 = 5.5 V r.sub.8 = -125.885 d.sub.8 = 2.5 1.69100 54.71 B r.sub.9 = +112.204 d.sub.9 = 1.4 r.sub.10 = +50.844 VI d.sub.10 = 4.8 1.67270 32.21 r.sub.11 = -260.600 (35.672) d.sub.11 = 9.145 (2.400) VII r.sub.12 = -66.834 d.sub.12 = 1.8 1.69100 54.71 VIII r.sub.13 = +51.958 C d.sub.13 = 4.5 1.68893 31.18 r.sub.14 = +3073.000 (17.054) d.sub.14 = 13.411 (3.200) IX r.sub.15 = +118.844 d.sub.15 = 5.2 1.61272 58.63 r.sub.16 = -93.056 d.sub.16 = 0.1 O X r.sub.17 = +78.861 d.sub.17 = 4.8 1.55232 63.46 r.sub.18 = -370.550 d.sub.18 = 0.1 XI r.sub.19 = +52.703 d.sub.19 = 6.8 1.48749 70.41 XII r.sub.20 = -98.572 d.sub.20 = 2.7 1.80518 25.43 r.sub.21 = +118.844 d.sub.21 = 28.0 XIII r.sub.22 = +39.809 d.sub.22 = 2.6 1.54814 45.75 r.sub.23 = +35.737 D d.sub.23 = 23.4 XIV r.sub.24 = +84.744 d.sub.24 = 4.0 1.54814 45.75 r.sub.25 = -147.480 d.sub.25 = 3.7 XV r.sub.26 = -35.479 d.sub.26 = 2.5 1.61765 55.14 r.sub.27 = -125.885 __________________________________________________________________________ Back focus s' = 49.18