Three-component varifocal objective

Claim 2

A varifocal objective consisting of: an axially shiftable positively refracting front component; an axially shiftable negative refracting intermediate component; and an axially fixed positively refracting rear component constituted by five closely air-spaced lens members, namely a positive first lens member, a positive second lens member, a negative third lens member, a positive fourth lens member and a positive fifth lens member, the spacing of said intermediate component from said rear component in a position of maximum overall focal length substantially exceeding any air space between said lens members while being substantially smaller than in a position of minimum overall focal length, said front component consisting of a forwardly convex negative meniscus L 1 followed by a biconvex lens L 2 and a substantially planoconvex lens L 3 with forwardly facing convexity, said second component consisting of a substantially planoconcave lens L 4 rearwardly facing concavity followed by a biconcave lens L 5 cemented onto a positive meniscus L 6 , said first lens member of said rear component being a biconvex lens L 7 , said second lens member consisting of a biconvex lens L 8 cemented to a biconcave lens L 9 , said third lens member being a biconcave lens L 10 , said fourth lens member being a biconvex lens L 11 , and said fifth member being a substantially planoconvex lens L 12 with forwardly facing convexity.

Claim 3

A varifocal objective as defined in claim 1, further comprising diaphragm means in the space between said intermediate and rear components.

Claim 4

A varifocal objective as defined in claim 1 wherein the separation between said front and rear components is substantially the same in said position of maximum overall focal length and in said position of minimum overall focal length.

Claim 5

A varifocal objective as defined in claim 3 wherein the ratio of said maximum and minimum overall focal lengths is close to 3:1.

Claim 6

A varifocal objective as defined in claim 1 wherein said lenses L 7 , L 8 , L 11 and L 12 have refractive indices less than 1.72.

Claim 7

A varifocal objective as defined in claim 1 wherein said first component has a focal length of +3.20 and said second component has a focal length of -1.06.

Claim 8

A varifocal objective as defined in claim 6 wherein the separation of said front component from said rear component is substantially the same in said positions of maximum overall focal length f max and of minimum overall focal length f min and is larger in a position of intermediate overall focal length f med .

Claim 9

A varifocal objective as defined in claim 7 wherein the numerical values of the radii of curvature r 1 - r 11 , the axial thicknesses d 1 - d 6 and the axial separations s 1 - s 4 of said lenses L 1 - L 6 , based upon said value of unity for said intermediate overall focal length f med , their refractive indices n d and their Abbe numbers ν d are substantially as given in the following table: Thicknesses Lenses Radii and Separations η.sub.d ν.sub.d ______________________________________ r.sub.1 = +8.706 L.sub.1 d.sub.1 = 0.15 1.805 25.4 r.sub.2 = +2.628 s.sub.1 = 0.21 r.sub.3 = +3.408 L.sub.2 d.sub.2 = 0.43 1.603 60.6 r.sub.4 = -18.304 s.sub.2 = 0.01 r.sub.5 = +2.278 L.sub.3 d.sub.3 = 0.52 1.658 50.9 r.sub.6 = -130.310 {0.05 {f.sub.min } s.sub.3 = {0.78 {f.sub.med } {1.21 {f.sub.max } r.sub.7 = +40.501 L.sub.4 d.sub.4 = 0.08 1.713 53.8 r.sub.8 = +0.999 s.sub. 4 = 0.24 r.sub.9 = -3.780 L.sub.5 d.sub.5 = 0.08 1.641 60.1 r.sub.10 = +1.170 L.sub.6 d.sub.6 = 0.21 1.847 23.8 r.sub.11 = +4.173. ______________________________________

Claim 10

A varifocal objective as defined in claim 8 wherein the numerical values of the axial separation s 5 of said intermediate and rear components, the radii r 12 - r 22 of said lenses L 7 - L 12 , the axial thicknesses d 7 - d 12 and axial separations s 6 - s 9 thereof, their refractive indices n d and their Abbe numbers ν d are substantially as given in the following table: Thicknesses Lenses Radii and Separations η.sub.d ν.sub.d ______________________________________ {2.06 {f.sub.min } s.sub.5 = {1.63 {f.sub.med } {0.90 {f.sub.max } r.sub.12 = +2.794 L.sub.7 d.sub.7 = 0.21 1.717 48.0 r.sub.13 = -3.655 s.sub.6 = 0.01 r.sub.14 = +0.955 L.sub.8 d.sub.8 = 0.42 1.637 36.7 r.sub.15 = -1.513 L.sub.9 d.sub.9 = 0.17 1.805 25.4 r.sub.16 = +2.006 s.sub.7 = 0.08 r.sub.17 = -2.166 L.sub.10 d.sub.10 = 0.19 1.847 23.8 r.sub.18 = +1.030 s.sub.8 = 0.15 r.sub.19 = +5.136 L.sub.11 d.sub.11 = 0.23 1.713 53.8 r.sub.20 = -1.036 s.sub.9 = 0.01 r.sub.21 = +0.946 L.sub.12 d.sub.12 = 0.23 1.641 60.1 r.sub.22 = -380.540. ______________________________________

Claim 11

A varifocal objective as defined in claim 2 wherein said first, second, third, fourth and fifth lens members have individual focal lengths substantially equal to +2.24, +3.25, -0.80, +1.23 and 1.47, respectively.

Claim 12

A varifocal objective as defined in claim 10 wherein the numerical values of the radii of curvature r 12 - r 22 , the axial thicknesses d 7 - d 12 and the axial separations s 6 - s 9 of said lenses L 7 - L 12 , based upon said value of unity for said intermediate overall focal length f med , their refractive indices n d and their Abbe numbers ν d are substantially as given in the following table: Thicknesses Lenses Radii and Separations η.sub.d ν.sub.d ______________________________________ r.sub.12 = +2.794 L.sub.7 d.sub.7 = 0.21 1.717 48.0 r.sub.13 = -3.655 s.sub.6 = 0.01 r.sub.14 = +0.955 L.sub.8 d.sub.8 = 0.42 1.657 36.7 r.sub.15 = -1.513 L.sub.9 d.sub.9 = 0.17 1.805 25.4 r.sub.16 = +2.066 s.sub.7 = 0.08 r.sub.17 = -2.166 L.sub.10 d.sub.10 = 0.19 1.847 23.8 r.sub.18 = +1.030 s.sub.8 = 0.15 r.sub.19 = +5.136 L.sub.11 d.sub.11 = 0.23 1.713 53.8 r.sub.20 = -1.036 s.sub.9 = 0.01 r.sub.21 = +0.946 L.sub.12 d.sub.12 = 0.23 1.641 60.1 r.sub.22 = -380.504. ______________________________________

Claim 13

A varifocal objective as defined in claim 1 wherein said first, second, third, fourth and fifth lens members have individual focal lengths substantially equal to +2.24, +2.30, -0.80, +1.23 and +1.85, respectively.

Claim 14

A varifocal objective as defined in claim 12 wherein the numerical values of the radii of curvature r 12 - r 22 , the axial thicknesses d 7 - d 12 and the axial separations s 6 - s 9 of said lenses L 7 - L 12 , based upon said value of unity for said intermediate overall focal length f med , their refractive indices n d and their Abbe numbers ν d are substantially as given in the following table: Thicknesses Lenses Radii and Separations η.sub.d ν.sub.d ______________________________________ r.sub.12 = +2.794 L.sub.7 d.sub.7 = 0.21 1.717 48.0 r.sub.13 = -3.655 s.sub.6 = 0.01 r.sub.14 = +0.955 L.sub.8 d.sub.8 = 0.42 1.657 36.7 r.sub.15 = -1.513 L.sub.9 d.sub.9 = 0.04 1.805 25.4 r.sub.16 = +3.800 s.sub.7 = 0.08 r.sub.17 = -2.166 L.sub.10 d.sub.10 = 0.19 1,847 23.8 r.sub.18 = +1.030 s.sub.8 = 0.15 r.sub.19 = +5.136 L.sub.11 d.sub.11 = 0.23 1.713 53.8 r.sub.20 = -1.036 s.sub.9 = 0.01 r.sub.21 = +1.153 L.sub.12 d.sub. 12 = 0.23 1.641 60.1 r.sub.22 = +42.916. ______________________________________

Claim 15

A varifocal objective as defined in claim 1 wherein said first, second, third, fourth and fifth lens members have individual focal lengths substantially equal to +2.75, +3.25, -0.76, +1.23 and +1.32, respectively.

Claim 16

A varifocal objective as defined in claim 14 wherein the numerical values of the radii of curvature r 12 - r 22 , the axial thicknesses d 7 - d 12 and the axial separations s 6 - s 9 of said lenses L 7 - L 12 , based upon said value of unity for said intermediate overall focal length f med , their refractive indices n d and their Abbe numbers ν d are substantially as given in the following table: Thicknesses Lenses Radii and Separations η.sub.d ν.sub.d ______________________________________ r.sub.12 = +4.180 L.sub.7 d.sub.7 = 0.21 1.717 48.0 r.sub.13 = -3.655 s.sub.6 = 0.01 r.sub.14 = +0.955 L.sub.8 d.sub.8 = 0.42 1.657 36.7 r.sub.15 = -1.513 L.sub.9 d.sub.9 = 0.17 1.805 25.4 r.sub.16 = +2.066 s.sub.7 = 0.08 r.sub.17 = -2.166 L.sub.10 d.sub.10 = 0.76 1.847 23.8 r.sub.18 = +1.064 s.sub.8 = 0.15 r.sub.19 = +5.136 L.sub.11 d.sub.11 = 0.23 1.713 53.8 r.sub.20 = -1.036 s.sub.9 = 0.01 r.sub.21 = +0.922 L.sub.12 d.sub.12 = 0.23 1.658 57.3 r.sub.22 = -12.833. ______________________________________

Claim 17

A varifocal objective as defined in claim 1 wherein the individual focal lengths f 7 , f 8 ,9, f 10 , f 11 and f 12 of said first, second, third, fourth and fifth members bear the relationship f 8 ,9 > f 7 > f 12 > f 11 > |f 10 |.