Athermalized zoom lens system

Claim 2

An athermalized zoom lens system comprising a plurality of lens groups, including movable lens groups capable of changing their relative position to vary the focal length; at least one of said plurality of lens groups having at least one lens formed of inorganic glass, most of the lenses of said system being formed of organic glass; said inorganic glass lens being such that when an organic glass lens is substituted therefor, the substituting organic glass lens creates, by zooming, an amount of focus variation substantially equal to a variation in focus created in the entire system by zooming, between predetermined temperatures, whereby the variation in focus position created in the entire system by zooming and resulting from a variation in temperature is corrected.

Claim 3

A zoom lens system according to claim 1, wherein said at least one inorganic glass lens is at least one positive lens.

Claim 4

A zoom lens system according to claim 1, wherein of said plurality of lens groups, the lens group forming a magnification changing system has said at least one inorganic glass lens.

Claim 5

A zoom lens system according to claim 3, wherein said magnification changing system comprises k lens elements and when said inorganic glass lens is the xth lens element from the object side, the temperature aberration coefficient ΔV S created in the entire magnification changing system by zooming where an organic glass lens is substituted for said inorganic glass lens and the amount of variation ΔV x in temperature aberration coefficient created in said substituting organic glass lens by zooming are substantially equal to each other and wherein ##EQU7## where h i W is the height of a paraxial ray passing through each lens in the shortest focal length condition of the entire system, h i T is the height of a paraxial ray passing through each lens in the longest focal length condition of the entire system, f i is the focal length of each lens, ω i is the thermal dispersion number of the organic glass forming each lens, and the subscript i represents that it is the value of the ith lens element from the object side, and when f i is the focal length of the ith lens at a predetermined standard temperature t and h i is the height of incidence on the ith lens of a paraxial ray incident from the object side at a height f and n i (t) is the refractive index of the ith lens at said standard temperature t, the thermal dispersion number ω i is defined as ##EQU8## for a predetermined temperature t 1 lower than said standard temperature t and a predetermined temperature t 2 higher than said standard temperature t.

Claim 6

A zoom lens system according to claim 4, wherein said magnification changing system has, in succession from the object side, a positive first group G 1 as a focusing group, a negative second group G 2 as a variator, and a positive third group G 3 as a compensator.

Claim 7

A zoom lens system according to claim 5, wherein said first group G 1 has a negative lens L 1 formed of polystyrene (PS), a positive lens L 2 of acryl (PMMA) cemented to said negative lens L 1 , and a positive lens L 3 formed of acryl, said second group G 2 has a negative lens L 4 formed of acryl, a negative lens L 5 formed of acryl, and a positive lens L 6 formed of inorganic glass, and said third group G 3 has a positive lens L 7 formed of acryl.

Claim 8

A zoom lens system according to claim 6, further having a fourth group G 4 as a master system and wherein said fourth group G 4 has a positive lens L 8 formed of inorganic glass, a negative lens L 9 formed of polystyrene, and two positive lenses L 10 and L 11 formed of acryl.

Claim 9

A zoom lens system according to claim 7, wherein numerical data are as follows: __________________________________________________________________________ Focal length f = 15˜45, Zoom ratio 3, F-number 1.8 Image height y = 5.5 __________________________________________________________________________ Center Thermal Radius of thickness and Refractive Abbe dispersion curvature air space index number number ω.sub.1 __________________________________________________________________________ r.sub.1 143.352 d.sub.1 1.0 n.sub.1 1.5914 ν.sub.1 31.0 ω.sub.1 77.3 L.sub.1 r.sub.2 29.984 d.sub.2 11.0 n.sub.2 1.4911 ν.sub.2 56.6 ω.sub.2 69.1 L.sub.2 r.sub.3 -102.250 d.sub.3 0.1 G.sub.1 r.sub.4 30.133 d.sub.4 6.0 n.sub.3 1.4911 ν.sub.3 56.6 ω.sub.3 69.1 L.sub.3 r.sub.5 220.269 d.sub.5 variable r.sub.6 474.308 d.sub.6 1.0 n.sub.4 1.4911 ν.sub.4 56.6 ω.sub.4 69.1 L.sub.4 r.sub.7 13.889 d.sub.7 4.0 r.sub.8 -28.403 d.sub.8 1.0 n.sub.5 1.4911 ν.sub.5 56.6 ω.sub.5 69.1 L.sub.5 G.sub.2 r.sub.9 12.398 d.sub.9 0.5 r.sub.10 13.414 d.sub.10 3.0 n.sub.6 1.7552 ν.sub.6 27.6 ω.sub.6 0.0 L.sub.6 r.sub.11 28.697 d.sub.11 variable r.sub.12 75.831 d.sub.12 2.2 n.sub.7 1.4911 ν.sub.7 56.6 ω.sub.7 69.1 L.sub.7 -G.sub.3 r.sub.13 -35.035 d.sub.13 variable r.sub.14 ∞ d.sub.14 7.5 n.sub.8 1.5750 ν.sub.8 41.5 ω.sub.8 0.0 Prism P r.sub.15 ∞ d.sub.15 5.9 r.sub.16 11.209 d.sub.16 5.2 n.sub.9 1.5186 ν.sub.9 70.1 ω.sub.9 0.0 L.sub.8 r.sub.17 -55.549 d.sub.17 2.13 r.sub.18 -19.228 d.sub.18 4.8 n.sub.10 1.5914 ν.sub.10 31.0 ω.sub.10 77.3 L.sub.9 r.sub.19 9.657 d.sub.19 2.45 G.sub.4 r.sub.20 36.745 d.sub.20 4.3 n.sub.11 1.4911 ν.sub.11 56.6 ω.sub.11 69.1 L.sub.10 r.sub.21 -29.730 d.sub.21 0.2 r.sub.22 14.651 d.sub. 22 6.0 n.sub.12 1.4911 ν.sub.12 56.6 ω.sub.12 69.1 L.sub.11 r.sub.23 -34.011 B.sub.f 12.235 __________________________________________________________________________ f.sub.W = 15 f.sub.M = 26 f.sub.T = 45 __________________________________________________________________________ d.sub.5 2.121 12.687 18.896 d.sub.11 19.309 12.856 1.874 d.sub.13 5.094 0.981 5.754 __________________________________________________________________________ where r represents the radius of curvature of each lens surface, d represents the center thickness and spacing of each lens, n and ν represent the refractive index and the Abbe number, respectively, of each lens for d-line (λ=587.6 nm), the respective subscript numbers represent the order from the object side, f W , f M and f T represent the shortest, the intermediate and the longest focal length, respectively, of the entire system, and B f represents the back focal length.

Claim 10

A zoom lens system according to claim 4, wherein said first group G 1 has a negative lens L 1 formed of polystyrene, a positive lens L 2 formed of CR-39 (registered trademark) and cemented to said negative lens L 1 , and a positive lens L 3 formed of acryl, said second group G 2 has two negative lenses L 4 and L 5 formed of CR-39, and a positive lens L 6 formed of inorganic glass, and said third group has a positive lens L 7 formed of acryl.

Claim 11

A zoom lens system according to claim 9, further having a fourth group G 4 as a master system and wherein said fourth group G 4 has a positive lens L 8 formed of inorganic glass, a negative lens L 9 formed of polystyrene, and two positive lenses L 10 and L 11 formed of CR-39.

Claim 12

A zoom lens system according to claim 10, wherein numerical data are as follows: __________________________________________________________________________ Focal length f = 15˜45, Zoom ratio 3, F-number 1.8 Image height y = 5.5 __________________________________________________________________________ Center Thermal Radius of thickness and Refractive Abbe dispersion curvature air space index number number ω.sub.i __________________________________________________________________________ r.sub.1 154.994 d.sub.1 1.0 n.sub.1 1.5914 ν.sub.1 31.0 ω.sub.1 77.3 L.sub.1 r.sub.2 30.139 d.sub.2 11.0 n.sub.2 1.4988 ν.sub.2 61.5 ω.sub.2 48.4 L.sub.2 r.sub.3 -102.250 d.sub.3 0.1 G.sub.1 r.sub.4 29.529 d.sub.4 6.0 n.sub.3 1.4911 ν.sub.3 56.6 ω.sub.3 69.1 L.sub.3 r.sub.5 185.427 d.sub.5 variable r.sub.6 107.699 d.sub.6 1.0 n.sub.4 1.4988 ν.sub.4 61.5 ω.sub.4 48.4 L.sub.4 r.sub.7 13.985 d.sub.7 4.0 r.sub.8 -25.888 d.sub.8 1.0 n.sub.5 1.4988 ν.sub.5 61.5 ω.sub.5 48.4 L.sub.5 G.sub.2 r.sub.9 12.398 d.sub.9 0.5 r.sub.10 13.384 d.sub.10 3.0 n.sub.6 1.7552 ν.sub.6 27.6 ω.sub.6 0.0 L.sub.6 r.sub.11 27.822 d.sub.11 variable r.sub.12 75.831 d.sub.12 2.2 n.sub.7 1.4911 ν.sub.7 56.6 ω.sub.7 69.1 L.sub.7 -G.sub.3 r.sub.13 -35.034 d.sub.13 variable r.sub.14 ∞ d.sub.14 7.5 n.sub.8 1.5750 ν.sub.8 41.5 ω.sub.8 0.0 Prism P r.sub.15 ∞ d.sub.15 5.9 r.sub.16 10.882 d.sub.16 5.2 n.sub.9 1.5186 ν.sub.9 70.1 ω.sub.9 0.0 L.sub.8 r.sub.17 -66.021 d.sub.17 2.13 r.sub.18 -19.171 d.sub.18 4.8 n.sub.10 1.5914 ν.sub.10 31.0 ω.sub.10 77.3 L.sub.9 r.sub.19 9.355 d.sub.19 2.45 G.sub.4 r.sub.20 38.769 d.sub.20 4.3 n.sub.11 1.4988 ν.sub.11 61.5 ω.sub.11 48.4 L.sub.10 r.sub.21 -29.730 d.sub.21 0.2 r.sub.22 14.651 d.sub.22 6.0 n.sub.12 1.4988 ν.sub.12 61.5 ω.sub.12 48.4 L.sub.11 r.sub.23 -32.052 B.sub.f 12.29 __________________________________________________________________________ f.sub.W = 15 f.sub.M = 26 f.sub.T = 45 __________________________________________________________________________ d.sub.5 1.780 12.346 18.555 d.sub.11 19.596 13.143 2.161 d.sub.13 4.690 0.577 5.350 __________________________________________________________________________ where r represents the radius of curvature of each lens surface, d represents the center thickness and spacing of each lens, n and ν represent the refractive index and the Abbe number, respectively, of each lens for the d-line (λ=587.6 nm), the respective subscript numbers represent the order from the object side, f W , f M and f T represent the shortest, the intermediate and the longest focal length, respectively, of the entire system, and B f represents the back focal length.

Claim 13

A zoom lens system according to claim 5, wherein said first group G 1 has a negative lens L 1 formed of polystyrene (PS), a positive lens L 2 formed of acryl (PMMA) and cemented to said negative lens L 1 , and a positive lens L 3 formed of acryl, said second group G 2 has a negative lens L 4 formed of acryl, a negative lens L 5 of acryl and a positive lens L 6 of polystyrene cemented to said negative lens L 5 , and said third group G 3 has a positive lens L 7 of acryl, a positive lens L 8 formed of inorganic glass, and a negative lens L 9 of polystyrene cemented to said positive lens L 8 .

Claim 14

A zoom lens system accoridng to claim 12, further having a fourth group G 4 as a master system and wherein said fourth group G 4 has a negative lens L 10 of acryl, a positive lens L 11 of acryl, a positive lens L 12 of acryl and a negative lens L 13 of polystyrene cemented to said positive lens L 12 .

Claim 15

A zoom lens system according to claim 13, wherein numerical data are as follows: __________________________________________________________________________ Focal length f = 12.5˜75, Zoom ratio 6, F-number 1.6 Image height y = 5.5 __________________________________________________________________________ Center Thermal Radius of thickness and Refractive Abbe dispersion curvature air space index number number ω.sub.i __________________________________________________________________________ r.sub.1 171.794 d.sub.1 1.4 n.sub.1 1.5914 ν.sub.1 31.0 ω.sub.1 77.3 L.sub.1 r.sub.2 44.763 d.sub.2 10.5 n.sub.2 1.4911 ν.sub.2 56.6 ω.sub.2 69.1 L.sub.2 r.sub.3 -166.580 d.sub.3 0.2 G.sub.1 r.sub.4 51.712 d.sub.4 5.0 n.sub.3 1.4911 ν.sub.3 56.6 ω.sub.3 69.1 L.sub.3 r.sub.5 524.796 d.sub.5 variable r.sub.6 64.079 d.sub.6 1.0 n.sub.4 1.4911 ν.sub.4 56.6 ω.sub.4 69.1 L.sub.4 r.sub.7 18.833 d.sub.7 6.8 r.sub.8 -31.706 d.sub.8 1.0 n.sub.5 1.4911 ν.sub.5 56.6 ω.sub.5 69.1 L.sub.5 G.sub.2 r.sub.9 14.579 d.sub. 9 3.5 n.sub.6 1.5914 ν.sub.6 31.0 ω.sub.6 77.3 L.sub.6 r.sub.10 31.257 d.sub.10 variable r.sub.11 34.936 d.sub.11 5.0 n.sub.7 1.4911 ν.sub.7 56.6 ω.sub.7 69.1 L.sub.7 r.sub.12 -35.182 d.sub.12 0.1 r.sub.13 19.512 d.sub.13 9.0 n.sub.8 1.5014 ν.sub.8 56.6 ω.sub.8 0.0 L.sub.8 G.sub.3 r.sub.14 -17.161 d.sub.14 1.0 n.sub.9 1.5914 ν.sub.9 31.0 ω.sub.9 77.3 L.sub.9 r.sub.15 57.128 d.sub.15 variable r.sub.16 -19.280 d.sub.16 1.0 n.sub.10 1.4911 ν.sub.10 56.6 ω.sub.10 69.1 L.sub.10 r.sub.17 11.647 d.sub.17 11.6 r.sub.18 108.097 d.sub.18 5.0 n.sub.11 1.4911 ν.sub.11 56.6 ω.sub.11 69.1 L.sub.11 r.sub.19 -14.194 d.sub.19 0.1 G.sub.4 r.sub.20 25.312 d.sub.20 7.0 n.sub.12 1.4911 ν.sub.12 56.6 ω.sub.12 69.1 L.sub.12 r.sub.21 -11.895 d.sub.21 1.0 n.sub.13 1.5914 ν.sub.13 31.0 ω.sub.13 77.3 L.sub.13 r.sub.22 -88.022 B.sub.f 20.22 __________________________________________________________________________ f.sub.W = 12.5 f.sub.M = 30.6 f.sub.T = 75 __________________________________________________________________________ d.sub.5 1.765 19.495 30.648 d.sub.10 44.910 21.485 1.625 d.sub.15 2.136 7.831 16.538 __________________________________________________________________________ where r represents the radius of curvature of each lens surface, d represents the center thickness and spacing of each lens, n and ν represent the refractive index and the Abbe number, respectively, of each lens for the d-line (λ=587.6 nm), the respective subscript numbers represent the order from the object side, f W , f M and f T represent the shortest, the intermediate and the longest focal length, respectively, of the entire system, and B f represents the back focal length.

Claim 16

A zoom lens system according to claim 4, wherein said magnification changing system has, in succession from the object side, a positive first group G 1 as a focusing group, a negative second group G 2 as a variator, and a negative third group G 3 as a compensator, and said zoom lens system further has a fourth group G 4 as a master system.

Claim 17

A zoom lens system according to claim 15, wherein said first group G 1 has a negative lens L 1 of polystyrene (PS), a positive lens L 2 of acryl (PMMA) cemented to said negative lens L 1 , and a positive lens L 3 of inorganic glass, said second group G 2 has a negative lens L 4 of acryl, a negative lens L 5 of acryl and a positive lens L 6 of polystyrene cemented to said negative lens L 5 , and said third group G 3 has a negative lens L 7 of acryl.

Claim 18

A zoom lens system according to claim 16, wherein said fourth group G 4 has a positive lens L 8 of acryl, a positive lens L 9 of inorganic glass, a negative lens L 10 of polystyrene cemented to said positive lens L 9 , a positive lens L 11 of acryl, a negative lens L 12 of polystyrene separated from said positive lens L 11 with a great air space therebetween, a positive lens L 13 of acryl cemented to said negative lens L 12 , and a positive lens L 14 of acryl.

Claim 19

A zoom lens system according to claim 17, wherein numerical data are as follows: __________________________________________________________________________ Focal length f = 11.5˜69, Zoom ratio 6, F-number 1.6 Image height y = 5.5 __________________________________________________________________________ Center Thermal Radius of thickness and Refractive Abbe dispersion curvature air space index number number ω.sub.i __________________________________________________________________________ r.sub.1 145.120 d.sub.1 1.0 n.sub.1 1.5914 ν.sub.1 31.0 ω.sub.1 77.3 L.sub.1 r.sub.2 38.616 d.sub.2 14.0 n.sub.2 1.4911 ν.sub.2 56.6 ω.sub.2 69.1 L.sub.2 r.sub.3 -95.884 d.sub.3 0.1 G.sub.1 r.sub.4 37.672 d.sub.4 4.5 n.sub.3 1.5186 ν.sub.3 70.1 ω.sub.3 0.0 L.sub.3 r.sub.5 94.187 d.sub.5 variable r.sub.6 -86.661 d.sub.6 1.0 n.sub.4 1.4911 ν.sub.4 56.6 ω.sub.4 69.1 L.sub.4 r.sub.7 14.605 d.sub.7 4.5 r.sub.8 -33.050 d.sub.8 1.2 n.sub.5 1.4911 ν.sub.5 56.6 ω.sub.5 69.1 L.sub.5 G.sub.2 r.sub.9 12.471 d.sub.9 2.8 n.sub.6 1.5914 ν.sub.6 31.0 ω.sub.6 77.3 L.sub.6 r.sub.10 61.485 d.sub.10 variable r.sub.11 -15.790 d.sub.11 1.0 n.sub.7 1.4911 ν.sub.7 56.6 ω.sub.7 69.1 L.sub.7 -G.sub.3 r.sub.12 -55.764 d.sub.12 variable r.sub.13 -61.301 d.sub.13 2.84 n.sub.8 1.4911 ν.sub.8 56.6 ω.sub.8 69.1 L.sub.8 r.sub.14 -23.745 d.sub.14 0.1 r.sub.15 229.535 d.sub.15 7.77 n.sub.9 1.5014 ν.sub.9 56.6 ω.sub.9 0.0 L.sub.9 r.sub.16 -14.609 d.sub.16 1.0 n.sub.10 1.5914 ν.sub.10 31.0 ω.sub.10 77.3 L.sub.10 r.sub.17 -35.567 d.sub.17 0.09 r.sub.18 31.960 d.sub.18 4.74 n.sub.11 1.4911 ν.sub.11 56.6 ω.sub.11 69.1 L.sub.11 G.sub.4 r.sub.19 -151.061 d.sub.19 27.274 r.sub.20 38.343 d.sub.20 1.0 n.sub.12 1.5914 ν.sub.12 31.0 ω.sub.12 77.3 L.sub.12 r.sub.21 10.013 d.sub.21 6.06 n.sub.13 1.4911 ν.sub.13 56.6 ω.sub.13 69.1 L.sub.13 r.sub.22 -124.764 d.sub.22 0.09 r.sub.23 11.817 d.sub.23 2.0 n.sub.14 1.4911 ν.sub.14 56.6 ω.sub.14 69.1 L.sub.14 r.sub.24 15.829 B.sub.f 5.39 __________________________________________________________________________ f.sub.W = 11.5 f.sub.M = 28 f.sub.T = 69 __________________________________________________________________________ d.sub.5 2.785 23.156 35.787 d.sub.10 36.733 13.171 3.733 d.sub.12 3.419 6.610 3.418 __________________________________________________________________________ where r represents the radius of curvature of each lens surface, d represents the center thickness and spacing of each lens, n and ν represent the refractive index and the Abbe number, respectively, of each lens for the d-line (λ=587.6 nm), the respective subscript numbers represent the order from the object side, f W , f M and f T represent the shortest, the intermediate and the longest focal length, respectively, of this entire system, and B f represents the back focal length.

Claim 20

A zoom lens system according to claim 3, wherein said magnification changing system comprises k lens elements and when it is assumed that a plurality of said inorganic glass lenses are included in said magnification changing system, where organic glass lenses are substituted for said plurality of inorganic glass lenses, the amount of variation ΔV S in temperature aberration coefficient created in the entire magnification changing system by zooming and the sum of the amounts of variation ΔV x in temperature aberration coefficient created in said substituting organic glass lenses by zooming are substantially equal to each other and wherein ##EQU9## where h i W is the height of a paraxial ray passing through each lens in the shortest focal length condition of the entire system, h i T is the height of a paraxial ray passing through each lens in the longest focal length condition of the entire system, f i is the focal length of each lens, ω i is the thermal dispersion number of the organic glass forming each lens, and the subscript i represents that it is the value of the ith lens element from the object side, and when f i is the focal length of the ith lens at a predetermined standard temperature t and h i is the height of incidence on the ith lens of a paraxial ray incident from the object side at a height f and n i (t) is the refractive index of the ith lens at said predetermined temperature t, the thermal dispersion number ω i is defined as ##EQU10## for a predetermined temperature t 1 lower than said standard temperature t and a predetermined temperature t 2 higher than said standard temperature t.

Claim 21

A zoom lens system according to claim 19, wherein said magnification changing system has, in succession from the object side, a divergent first lens group G 1 and a convergent second lens group G 2 movable relative to each other on the optical axis for zooming.

Claim 22

A zoom lens system according to claim 20, wherein said first group G 1 has a positive lens L 1 of acryl (PMMA), two negative lenses L 2 and L 3 of acryl, and a positive meniscus lens L 4 of polystyrene (PS), and said second group G 2 has a positive lens L 5 of inorganic glass, a negative lens L 6 of polystyrene cemented to said positive lens L 5 , a positive lens L 7 of acryl, a positive meniscus lens L 8 of inorganic glass, a negative lens L 9 of inorganic glass and a positive lens L 10 of acryl.

Claim 23

A zoom lens system according to claim 21, wherein numerical data are as follows: __________________________________________________________________________ Focal length f = 35˜70, Zoom ratio 2, F-number 3.5 Image height y = 21.6 __________________________________________________________________________ Center Thermal Radius of thickness and Refractive Abbe dispersion curvature air space index number number ω.sub.i __________________________________________________________________________ r.sub.1 67.533 d.sub.1 8.2 n.sub.1 1.4911 ν.sub.1 57.6 ω.sub.1 69.1 L.sub.1 r.sub.2 293.759 d.sub.2 0.7 r.sub.3 140.240 d.sub.3 1.5 n.sub.2 1.4911 ν.sub.2 57.6 ω.sub.2 69.1 L.sub.2 r.sub.4 22.775 d.sub.4 7.0 G.sub.1 r.sub.5 -175.452 d.sub.5 1.5 n.sub.3 1.4911 ν.sub.3 57.6 ω.sub.3 69.1 L.sub.3 r.sub.6 32.226 d.sub.6 5.7 r.sub.7 33.139 d.sub.7 3.9 n.sub.4 1.5914 ν.sub.4 31.0 ω.sub.4 77.3 L.sub.4 r.sub.8 89.304 d.sub.8 variable r.sub.9 49.613 d.sub.9 6.5 n.sub.5 1.5014 ν.sub.5 56.5 ω.sub.5 0.0 L.sub.5 r.sub.10 -28.258 d.sub.10 1.0 n.sub. 6 1.5914 ν.sub.6 31.0 ω.sub.6 77.3 L.sub.6 r.sub.11 -123.425 d.sub.11 0.1 r.sub.12 30.907 d.sub.12 3.5 n.sub.7 1.4911 ν.sub.7 57.6 ω.sub.7 69.1 L.sub.7 r.sub.13 188.671 d.sub.13 0.1 r.sub.14 22.455 d.sub.14 2.5 n.sub.8 1.6583 ν.sub.8 57.3 ω.sub.8 0.0 L.sub.8 G.sub.2 r.sub.15 39.238 d.sub.15 4.0 r.sub.16 209.734 d.sub.16 1.0 n.sub.9 1.7234 ν.sub.9 38.0 ω.sub.9 0.0 L.sub.9 r.sub.17 18.146 d.sub.17 5.2 r.sub.18 106.970 d.sub.18 3.8 n.sub.10 1.4911 ν.sub.10 57.6 ω.sub.10 69.1 L.sub.10 r.sub.19 -35.294 B.sub.f variable __________________________________________________________________________ f.sub.W = 35 f.sub.M = 51 f.sub.T = 70 __________________________________________________________________________ d.sub.8 34.338 15.595 1.538 B.sub.f 38.465 57.208 71.265 __________________________________________________________________________ where r represents the radius of curvature of each lens surface, d represents the center thickness and spacing of each lens, n and ν represent the refractive index and the Abbe number, respectively, of each lens for the d-line (λ=587.6 nm), the respective subscript numbers represent the order from the object side, f W , f M and f T represent the shortest, the intermediate and the longest focal length, respectively, of the entire system, and B f represents the back focal length.

Claim 24

A zoom lens system according to claim 20, wherein said first lens group has, in succession from the object side, a positive lens L 1 , a negative meniscus lens L 2 , a negative lens L 3 and a positive lens L 4 , said positive lens L 4 which is most adjacent to the image side is formed of inorganic glass, said second lens group has, in succession from the object side, three positive, negative and positive lenses, and the lens which is most adjacent to the image side is formed of inorganic glass.

Claim 25

A zoom lens system according to claim 20, wherein said second lens group has, in succession from the object side, three continuous positive, negative and positive lenses, and the two positive lenses of said three continuous positive lenses are formed of inorganic glass.

Claim 26

A zoom lens system according to claim 1, wherein said plurality of lens groups comprise a magnification changing system lens group and a master system lens group which is stationary during magnification change, at least one positive lens in said master system lens group being said at least one inorganic glass lens, and said at least one inorganic glass lens being such that when an organic glass lens is substituted therefor, said substituting organic glass lens has an amount of focus variation corresponding to the direct current component of the focus variation created in said magnification changing system by zooming, between said predetermined temperatures.

Claim 27

A zoom lens system according to claim 25, wherein if it is assumed that said master system comprises u lenses, that the focal lengths of the respective lenses forming said master system are f 1 , f 2 , . . . , f i , . . . , f u , that the refractive indices of said respective lenses are n 1 , n 2 , . . . , n i , . . . , n u , that the thermal dispersion numbers of said respective lenses are ω 1 , ω 2 , . . . , ω i , . . . , ω u and that the heights of paraxial rays in said respective lenses are h 1 , h 2 , . . . , h i , . . . , h u , then the temperature aberration coefficient Tm of said master system is defined as ##EQU11## and the temperature aberration coefficient Tm of the master system, the temperature aberration coefficient Ttot(W) of the entire system in the shortest focal length condition and the temperature aberration coefficient Ttot(T) of the entire system in the longest focal length condition are respectively defined as ##EQU12## and satisfy the following conditions:

Claim 28

-0. 02≦Tm≦0.01 |Ttot(W)|23 0.01 0.005≦Ttot(T)≦0.03 where h i W is the height of a paraxial ray passing through each lens in the shortest focal length condition of the entire system, h i T is the height of a paraxial ray passing through each lens in the longest focal length condition of the entire system, f i is the focal length of each lens, ω i is the thermal dispersion number of the organic glass forming each lens, and the subscript i represents that it is the value of the ith lens element from the object side, and when f i is the focal length of the ith lens at a predetermined standard temperature t and h i is the height of incidence on the ith lens of a paraxial ray incident from the object side at a height f and n i (t) is the refractive index of the ith lens at said standard temperature t, the thermal dispersion number ω i is defined as ##EQU13## for a predetermined temperature t 1 lower than said standard temperature t and a predetermined temperature t 2 higher than said standard temperature t.

Claim 29

-0. 02≦Tm≦0.01 |Ttot(W)|23 0.01 0.005≦Ttot(T)≦0.03 where h i W is the height of a paraxial ray passing through each lens in the shortest focal length condition of the entire system, h i T is the height of a paraxial ray passing through each lens in the longest focal length condition of the entire system, f i is the focal length of each lens, ω i is the thermal dispersion number of the organic glass forming each lens, and the subscript i represents that it is the value of the ith lens element from the object side, and when f i is the focal length of the ith lens at a predetermined standard temperature t and h i is the height of incidence on the ith lens of a paraxial ray incident from the object side at a height f and n i (t) is the refractive index of the ith lens at said standard temperature t, the thermal dispersion number ω i is defined as ##EQU13## for a predetermined temperature t 1 lower than said standard temperature t and a predetermined temperature t 2 higher than said standard temperature t.

Claim 30

A zoom lens system according to claim 26, wherein said magnification changing system has, in succession from the object side, a positive first group G 1 as a focusing group, a negative second group G 2 as a variator, and a positive third group G 3 as a compensator, and said master system comprises a positive fourth group G 4 .

Claim 31

A zoom lens system according to claim 27, wherein said first group G 1 has a negative lens L 1 formed of polystyrene (PS), a positive lens L 2 of acryl (PMMA) cemented to said negative lens L 1 , and a positive lens L 3 formed of acryl, said second group G 2 has a negative lens L 4 formed of acryl, a negative lens L 5 formed of acryl, and a positive lens L 6 of polystyrene cemented to said negative lens L 5 , said third group G 3 has a positive lens L 7 formed of acryl, and said fourth group G 4 which is the master system has a positive lens L 8 formed of inorganic glass, a negative lens L 9 formed of polystyrene, and two positive lenses L 10 and L 11 formed of acryl.

Claim 32

A zoom lens system according to claim 28, wherein numerical data are as follows: __________________________________________________________________________ Focal length f = 15˜45, Zoom ratio 3, F-number 1.8 Image height y = 5.5 __________________________________________________________________________ Center Thermal Radius of thickness and Refractive Abbe dispersion curvature air space index number factor ω.sub.i __________________________________________________________________________ r.sub.1 126.5 d.sub.1 1.0 n.sub.1 1.5914 ν.sub.1 31.0 ω.sub.1 77.3 L.sub.1 r.sub.2 28.37 d.sub.2 10.5 n.sub.2 1.4911 ν.sub.2 56.6 ω.sub.2 69.1 L.sub.2 r.sub.3 -121.659 d.sub.3 0.1 G.sub.1 r.sub.4 30.654 d.sub.4 6.3 n.sub.3 1.4911 ν.sub.3 56.6 ω.sub.3 69.1 L.sub.3 r.sub.5 473.205 d.sub.5 variable r.sub.6 -627.475 d.sub.6 1.0 n.sub.4 1.4911 ν.sub.4 56.6 ω.sub.4 69.1 L.sub.4 r.sub.7 11.685 d.sub.7 4.0 r.sub.8 -24.512 d.sub.8 1.0 n.sub.5 1.4911 ν.sub.5 56.6 ω.sub.5 69.1 L.sub.5 G.sub.2 r.sub.9 11.559 d.sub.9 3.5 n.sub.6 1.5914 ν.sub.6 31.0 ω.sub.6 77.3 L.sub.6 r.sub.10 85.329 d.sub.10 variable r.sub.11 51.959 d.sub.11 2.2 n.sub.7 1.4911 ν.sub.7 56.6 ω.sub.7 69.1 L.sub.7 -G.sub.3 r.sub.12 -44.546 d.sub.12 variable r.sub.13 10.854 d.sub.13 11.3 n.sub.8 1.4978 ν.sub.8 82.3 ω.sub.8 0.0 L.sub.8 r.sub.14 -139.132 d.sub.14 2.13 r.sub.15 -21.792 d.sub.15 4.8 n.sub.9 1.5914 ν.sub.9 31.0 ω.sub.9 77.3 L.sub.9 r.sub.16 9.605 d.sub.16 2.45 G.sub.4 r.sub.17 34.579 d.sub.17 4.3 n.sub.10 1.4911 ν.sub.10 56.6 ω.sub.10 69.1 L.sub.10 r.sub.18 -29.492 d.sub.18 0.2 r.sub.19 14.981 d.sub.19 6.0 n.sub.11 1.4911 ν.sub.11 56.6 ω.sub.11 69.1 L.sub.11 r.sub.20 -32.857 __________________________________________________________________________ f.sub.W = 15.06 f.sub.M = 25.64 f.sub.T = 43.63 __________________________________________________________________________ d.sub.5 1.8375 12.4237 18.6442 d.sub.10 18.6068 12.1419 1.1399 d.sub.12 8.8983 4.7770 9.5584 B.sub.f = 13.64 __________________________________________________________________________ where r represents the radius of curvature of each lens surface, d represents the center thickness and spacing of each lens, n and ν represent the refractive index and the Abbe number, respectively, of each lens for the d-line (λ=587.6 nm), the respective subscript numbers represent the order from the object side, f W , f M and f T represent the shortest, the intermediate and the longest focal length, respectively, of the entire system, and B f represents the back focal length.

Claim 33

A zoom lens system according to claim 29, wherein said first group G 1 has a negative lens L 1 formed of polystyrene (PS), a positive lens L 2 of acryl (PMMA) cemented to said negative lens L 1 , and a positive lens L 3 formed of acryl, said second group G 2 has a negative lens L 4 formed of acryl, a negative lens L 5 formed of acryl, and a positive lens L 6 of polystyrene cemented to said negative lens L 5 , said third group G 3 has a positive lens L 7 formed of acryl, and said fourth group G 4 has a positive lens L 8 formed of inorganic glass, a negative lens L 9 formed of polystyrene, a positive lens L 10 formed of acryl, and a positive lens L 11 formed of inorganic glass.

Claim 34

A zoom lens system according to claim 30, wherein numerical data are as follows: __________________________________________________________________________ Focal length F = 15˜45, Zoom ratio 3, F-number 1.8 Image height y = 5.5 __________________________________________________________________________ Center Thermal Radius of thickness and Refractive Abbe dispersion curvature air space index number factor ω.sub.i __________________________________________________________________________ r.sub.1 126.5 d.sub.1 1.0 n.sub.1 1.5914 ν.sub.1 31.0 ω.sub.1 77.3 L.sub.1 r.sub.2 28.37 d.sub.2 10.5 n.sub.2 1.4911 ν.sub.2 56.6 ω.sub.2 69.1 L.sub.2 r.sub.3 -121.659 d.sub.3 0.1 G.sub.1 r.sub.4 30.654 d.sub.4 6.3 n.sub.3 1.4911 ν.sub.3 56.6 ω.sub.3 69.1 L.sub.3 r.sub.5 473.206 d.sub.5 variable r.sub.6 -627.475 d.sub.6 1.0 n.sub.4 1.4911 ν.sub.4 56.6 ω.sub.4 69.1 L.sub.4 r.sub.7 11.685 d.sub.7 4.0 r.sub.8 -24.512 d.sub.8 1.0 n.sub.5 1.4911 ν.sub.5 56.6 ω.sub.5 69.1 L.sub.5 G.sub.2 r.sub.9 11.56 d.sub.9 3.5 n.sub.6 1.5914 ν.sub.6 31.0 ω.sub.6 77.3 L.sub.6 r.sub.10 85.329 d.sub.10 variable r.sub.11 51.959 d.sub.11 2.2 n.sub.7 1.4911 ν.sub.7 56.6 ω.sub.7 69.1 L.sub.7 -G.sub.3 r.sub.12 -44.546 d.sub.12 variable r.sub.13 10.854 d.sub.13 5.2 n.sub.8 1.4978 ν.sub.8 82.3 ω.sub.8 0.0 L.sub.8 r.sub.14 -139.132 d.sub.14 2.13 r.sub.15 -21.792 d.sub.15 4.8 n.sub.9 1.5914 ν.sub.9 31.0 ω.sub.9 77.3 L.sub.9 r.sub.16 9.605 d.sub.16 2.45 G.sub.4 r.sub.17 34.579 d.sub.17 4.3 n.sub.10 1.4911 ν.sub.10 56.6 ω.sub.10 69.1 L.sub.10 r.sub.18 -29.492 d.sub.18 0.2 r.sub.19 14.981 d.sub.19 6.0 n.sub.11 1.5014 ν.sub.11 56.6 ω.sub.11 0.0 L.sub.11 r.sub.20 -32.857 __________________________________________________________________________ f.sub.W = 15.06 f.sub.M = 25.64 f.sub.T = 43.63 __________________________________________________________________________ d.sub.5 1.8375 12.4237 18.6442 d.sub.10 18.6068 12.1419 1.1399 d.sub.12 8.8983 4.7770 9.5584 B.sub.f = 13.64 __________________________________________________________________________ where r represents the radius of curvature of each lens surface, d represents the center thickness and spacing of each lens, n and ν represent the refractive index and the Abbe number, respectively, of each lens for the d-line (λ=587.6 nm), the respective subscript numbers represent the order from the object side, f W , f M and f T represent the shortest, the intermediate and the longest focal length, respectively, of the entire system, and B f represents the back focal length.