A fast photographic or cinematographic lens with variable focal length

Abstract

880,659. Variable focal length objectives. SCHNEIDER, M. C. Jan. 22, 1960 [Feb. 17, 1959], No. 2362 / 60. Class 97(1). A photographic objective of variable focal length and a relative aperture of about 1:2.8 comprises a four element basic objective, and in front thereof a supplementary system made up of four members of which the front member is positive and consists of two components in broken contact and is fixed, the rear member is also positive and fixed and is in the form of a cemented doublet, and relatively movable between these positive members are two negative doublets. In this objective, the focal length of the rear positive member of the supplementary system is equal to or less than 75 % of that of the front positive member and the focal length of the movable negative doublet nearest the rear fixed positive member exceeds by at least 10% the focal length of the other negative doublet. Preferably the adjacent surfaces of the two negative doublets are concave towards one another and are the surfaces of highest curvature in each doublet. It is also preferred that the sum of the air gaps between and on each side of the negative doublets shall be less than the focal length of the rear positive member. Optical data are given for one example of the embodiment shown.

Description

The air spaces ds, ds and dn are variable and, with a total of 223.05 in the sense of the invention, are smaller than the focal length f4' of the image-side positive term IV which is +242.0. According to the claims, this is less than 75% of the focal length f / of the positive group on the object side is calculated to be + 424.0. The focal length f3' of the displaceable negative element III facing the rear element IV is -219.0 according to the invention at least 10% greater than the focal length fz' of the negative element II arranged in front of it, which is -191.0. the Focal length f5' of the four-element basic objective is −91.34 in the exemplary embodiment shown. The outer radii ra and rg of the two inner negative members II and III, which preferably determine the refractive power, are within the meaning of FIG Invention facing each other, in addition, the other surfaces of these two members have only small deflections. All requirements for the fulfillment of the given the demanding conditions of such a Vario-o lens. II III IV L1 L3 Numerical example T1 = + 342.55 r2 = -2255.00 r3 = + 287.20 r4 = -4232.50 r5 = + 470.75 L10 L-,, H1 = 20.00 d2 = 0.40 dz = 19.35 dt = 5.85 d5 =124.25 U = - 850.50 de = 10.25 r7 = - 231.95 L6 d7 = 3.10 r8 = + 93.15 '13 U = - 118.15 r10 = + 141.25 rn = + 366.15 r12 = + 307.65 r13 = - 104.15 rM = - 290.95 r15= + 64.95 rle= — 1050.00 r17= + 38.93 r18= + 49.55 r19= - 129.90 T20 = +33.20 r21 = + 93.40 r22 = - 53.15 d8 = 34.10 d9 = 2.95 sc = 7.30 dlt = 64.70 di2 = 6.85 ^i3 = 3.40 you= 45.00 ^15= 10.20 dles = 0.15 ^17= 10.10 d18 = 6.80 λλ1β = 2.85 d20 = 13.75 i21 = 10.85 V^ = 402.20 1.52542 64.55 air clearance 1.62041 60.29 1.76182 26.52 air gap (variable) 1.75520 27.53 1.50378 66.73 air gap (variable) 1.50378 66.73 1.75520 27.53 air gap (variable) 1.62041 60.29 1.62004 36.34 air clearance 1.62041 60.29 Air distance 1.62041 60.29 air clearance 1.69895 30.05 air clearance 1.65830 57.29

Claims

Patent claims:

1. High-aperture photographic or cinematographic lens with variable focal length, consisting of one of the film plane a four-part basic objective facing it and a preceding one, thus structured from five parts into four groups of effects A front-mounted system, two of which, facing the longer beam width, form the positive front group, which, like a basic objective, The opposing, single-standing positive element is fixedly arranged, while two elements located between them, preferably each consisting of two lenses, are Negative elements cemented together with opposing refractive power for the purpose of changing the focal length of the overall system in the direction of the optical axis are movable relative to each other, characterized by such a distribution of the refractive forces between the elements of the telescope system (I to IV), that the focal length (f4') of the fixed positive element (IV) facing the basic objective (V) is equal to or less than 75% of the focal length ( / Y) of the object-side, also fixed positive front group (I) and that, in addition, the focal length (f3') of the rear element (IV) facing, the movable negative element (III) is at least 10% larger than the focal length ( / V) of the also movable front group (I) opposite negative term (II).

2. Lens according to claim 1, characterized in that the surface curvatures in the two movable negative elements (II and III) are opposite, wherein the outer radius (r8) which preferably determines the refractive power is in the member (II) of the image side and the most strongly curved The outer radius (ra) in the subsequent negative term (III) faces the object side, while the other surfaces (re, r7) or r10, ru) exhibit only relatively small deflections.

3. Objective according to claims 1 and 2, characterized in that the sum of the movable system elements (II and III) limiting air gaps (ds, d& and ^11) are smaller than the focal length ( / Y) of the positive element (IV) facing the image side. This includes 1 sheet of drawings.