Zoom lenses

Claim 2

A compact, high performance low zoom ratio variable viewing angle lens system, comprising: a front lens group having a negative focal length f 1 and a final convex lens; a rear lens group having a positive focal length f 2 ; an aerial space of distance l between said front and rear lens groups in which the luminous flux is greatly divergent; the incidental covering angle being variable by varying the aerial space l, said lens system satisfying the following conditions: ##EQU12## where l max is the maximum value of the aerial space l, f min is the overall focal length at l=l max , said lens system further having a back focal length of 0.8 Lφ or more and a minimum value of the overall lens length including the back focal length of 2.3 Lφ or less, where Lφ is the length of the diagonal of the image frame, said lens system defined by the followings: ______________________________________ Lens f = 26.0-31.0 view angle 2ω = 81.2°-70.8° L.sub.i j,k r d n υ ______________________________________ 1 91.9 L.sub.1 2.54 1.51823 59.0 2 1069.190 0.10 3 42.130 L.sub.2 1.37 1.80400 46.6 4 13.703 6.45 5 465.000 L.sub.3 1.49 1.67790 50.7 6 28.750 5.19 7 23.270 L.sub.4 1.82 1.78470 26.2 8 34.700 5.02-1.669 9 56.700 L.sub.5 4.19 1.80610 40.9 10 -59.400 0.10 11 18.093 L.sub.6 2.31 1.80610 40.9 12 56.517 2.37 13 -64.907 L.sub.7 7.24 1.84666 23.9 14 16.331 1.12 15 43.469 L.sub.8 2.25 1.51823 59.0 16 -23.588 0.10 17 -89.373 L.sub.9 1.47 1.51633 64.1 18 -26.047 ______________________________________

Claim 3

A variable viewing angle lens system, wherein said front lens group comprises, in order from the object side, a positive lens having a convex surface directed to the object, two negative lens units and a positive meniscus lens having a convex surface directed to the object, wherein said rear lens group comprises, in order from the object side, a positive lens unit, a negative lens unit and a positive lens unit, both of said rear lens group positive lens units including at least two positive lenses, said lens system defined by the followings: ______________________________________ f = 26.0- 31.0 view angle 2ω = 80.6°- 70.6° ______________________________________ L.sub.i j, k r d n ν ______________________________________ 1 90.728 L.sub.1 3.40 1.56873 63.1 2 -2811.257 0.10 3 65.898 L.sub.2 1.50 1.80400 46.6 4 15.890 5.18 5 73.486 L.sub.3 1.40 1.80400 46.6 6 27.490 6.84 7 25.726 L.sub.4 2.40 1.80518 25.4 8 40.610 6.40- 1.5341 9 38.361 L.sub.5 8.55 1.72342 38.0 10 -77.574 2.00 11 22.047 L.sub.6 2.86 1.80400 46.6 12 109.428 1.53 13 -48.177 L.sub.7 5.53 1.84666 23.9 14 20.603 1.94 15 -193.273 L.sub.8 2.41 1.64000 60.1 16 -23.453 0.10 17 -5771.737 L.sub.9 2.10 1.51821 65.0 18 -33.615 ______________________________________

Claim 4

A variable viewing angle lens system, wherein said front lens group comprises, in order from the object side, a positive lens having a convex surface directed to the object, two negative lens units and a positive meniscus lens having a convex surface directed to the object, wherein said rear lens group comprises, in order from the object side, a positive lens unit, a negative lens unit and a positive lens unit, both of said rear lens group positive lens units including at least two positive lenses, said lens system defined by the followings: ______________________________________ f = 26.0- 31.0 view angle 2ω = 80.6°- 70.6° ______________________________________ L.sub.i j, k r d n ν ______________________________________ 1 90.728 L.sub.1 3.40 1.56873 63.1 2 -2811.257 0.10 3 65.898 L.sub.2 1.50 1.80400 46.6 4 15.890 5.18 5 73.486 L.sub.3 1.40 1.80400 46.6 6 27.490 6.84 7 25.726 L.sub.4 2.40 1.80518 25.4 8 40.610 6.40- 1.5341 9 38.361 L.sub.5 8.55 1.72342 38.0 10 -77.574 2.00 11 22.047 L.sub.6 2.86 1.80400 46.6 12 109.428 1.53 13 -48.177 L.sub.7 5.53 1.84666 23.9 14 20.603 1.94 15 -193.273 L.sub.8 2.41 1.64000 60.1 16 -23.453 0.10 17 -5771.737 L.sub.9 2.10 1.51821 65.0 18 -33.615 ______________________________________

Claim 5

A variable viewing angle lens system, wherein said front lens group comprises, in order from the object side, two negative lens and a positive lens, said positive lens having a strong convex surface directed to the object, wherein said rear lens group comprises, in order from the object side, a positive lens unit, a negative lens unit and a positive lens unit, both of said rear lens group positive lens units comprising two positive lenses, said lens system defined by the followings: ______________________________________ f = 33.181-39.1 view angle 2ω = 67.2° - 57.8° L.sub.i j, k r d n ν ______________________________________ 1 47.400 L.sub.1 1.50 1.80610 40.9 2 19.380 5.75 3 -423.000 L.sub.2 1.50 1.62041 60.3 4 91.640 2.40 5 28.500 L.sub.3 2.47 1.80518 25.4 6 49.138 14.80- 6.74 7 74.800 L.sub.4 3.10 1.77250 49.6 8 -51.555 0.10 9 20.000 L.sub.5 2.79 1.68600 49.2 10 61.864 2.95 11 -59.770 L.sub.6 5.67 1.80518 25.4 12 21.083 4.15 13 -49.477 L.sub. 7 2.00 1.65160 58.6 14 -24.406 0.69 15 -123.305 L.sub.8 2.55 1.58913 61.6 16 -28.909 ______________________________________

Claim 6

A variable viewing angle lens system, wherein said front lens group comprises, in order from the object side, two negative lens and a positive lens, said positive lens having a strong convex surface directed to the object, wherein said rear lens group comprises, in order from the object side, a positive lens unit, a negative lens unit and a positive lens unit, both of said rear lens group positive lens units comprising two positive lenses, said lens system defined by the followings: ______________________________________ f = 33.181-39.1 view angle 2ω = 67.2° - 57.8° L.sub.i j, k r d n ν ______________________________________ 1 47.400 L.sub.1 1.50 1.80610 40.9 2 19.380 5.75 3 -423.000 L.sub.2 1.50 1.62041 60.3 4 91.640 2.40 5 28.500 L.sub.3 2.47 1.80518 25.4 6 49.138 14.80- 6.74 7 74.800 L.sub.4 3.10 1.77250 49.6 8 -51.555 0.10 9 20.000 L.sub.5 2.79 1.68600 49.2 10 61.864 2.95 11 -59.770 L.sub.6 5.67 1.80518 25.4 12 21.083 4.15 13 -49.477 L.sub. 7 2.00 1.65160 58.6 14 -24.406 0.69 15 -123.305 L.sub.8 2.55 1.58913 61.6 16 -28.909 ______________________________________

Claim 7

A variable viewing angle lens system, wherein said final convex lens in said front lens group is a positive lens having a strong convex surface directed to the object, wherein said rear lens group comprises, in order from the object side, a positive lens unit having two positive lenses, a negative lens unit and a positive lens unit having one positive lens, said lens system defined by the followings: ______________________________________ f = 46.8- 57.0 view angle 2ω = 50.0° - 41.0° L.sub.i j, k r d n ν ______________________________________ 1 323.760 L.sub.1 1.98 1.78470 26.2 2 33.728 5.05 3 277.500 L.sub.2 1.40 1.48749 70.1 4 55.506 0.10 5 39.396 L.sub.3 5.62 1.80518 25.4 6 360.000 22.64- 1.269 7 50.752 L.sub.4 2.60 1.77250 49.6 8 -423.000 0.10 9 19.750 L.sub.5 3.91 1.81600 46.6 10 61.697. - 2.93 11 157.605 L.sub.6 2.62 1.80518 25.4 12 14.677 13.57 13 115.000 L.sub.7 3.18 1.46450 66.0 14 -35.349 ______________________________________

Claim 8

A variable viewing angle lens system, wherein said final convex lens in said front lens group is a positive lens having a strong convex surface directed to the object, wherein said rear lens group comprises, in order from the object side, a positive lens unit having two positive lenses, a negative lens unit and a positive lens unit having one positive lens, said lens system defined by the followings: ______________________________________ f = 46.8- 57.0 view angle 2ω = 50.0° - 41.0° L.sub.i j, k r d n ν ______________________________________ 1 323.760 L.sub.1 1.98 1.78470 26.2 2 33.728 5.05 3 277.500 L.sub.2 1.40 1.48749 70.1 4 55.506 0.10 5 39.396 L.sub.3 5.62 1.80518 25.4 6 360.000 22.64- 1.269 7 50.752 L.sub.4 2.60 1.77250 49.6 8 -423.000 0.10 9 19.750 L.sub.5 3.91 1.81600 46.6 10 61.697. - 2.93 11 157.605 L.sub.6 2.62 1.80518 25.4 12 14.677 13.57 13 115.000 L.sub.7 3.18 1.46450 66.0 14 -35.349 ______________________________________

Claim 9

A low zoom ratio variable viewing angle lens system adjustable between wide angle and narrow angle positions, comprising: a front lens group having a negative focal length f 1 and comprising, in order from the object side, a positive lens having a convex surface directed to the object, two negative lens units and a final positive meniscus lens having a convex surface directed to the object; a rear lens group having a positive focal length f 2 and comprising, in order from the object side, a positive, a negative and a positive lens unit in which both positive lens units are composed of at least two positive lenses; said lens system satisfying the following conditions: ##EQU13## where: f min is the overall focal length of the system at the wide angle position; and f max is the overall focal length of the system at the narrow angle position, so that a sufficient back focal length can be maintained in a compact lens system having a very small zoom variation, said lens system defined by the followings: ______________________________________ f = 26.0- 31.0 view angle 2ω = 81° - 70.4° L.sub.i j, k r d n ν ______________________________________ 1 58.394 L.sub.1 2.88 1.48749 70.1 2 207.958 0.10 3 34.288 L.sub.2 1.16 1.80400 46.6 4 12.987 6.28 5 -107.690 L.sub.3 1.20 1.67790 50.7 6 73.301 5.23 7 22.937 L.sub.4 2.77 1.80518 25.4 8 31.500 8.08- 3.67 9 76.441 L.sub.5 2.77 1.80610 40.9 10 -51.242 0.10 11 18.113 L.sub.6 2.13 1.80610 40.9 12 55.678 2.72 13 -46.641 L.sub.7 4.98 1.84666 23.9 14 19.433 1.15 15 -1382.853 L.sub.8 2.23 1.51823 59.0 16 -17.260 0.10 17 -196.186 L.sub.9 1.74 1.51633 64.1 18 -33.488 ______________________________________

Claim 10

A low zoom ratio variable viewing angle lens system adjustable between wide angle and narrow angle positions, comprising: a front lens group having a negative focal length f 1 and comprising, in order from the object side, a positive lens having a convex surface directed to the object, two negative lens units and a final positive meniscus lens having a convex surface directed to the object; a rear lens group having a positive focal length f 2 and comprising, in order from the object side, a positive, a negative and a positive lens unit in which both positive lens units are composed of at least two positive lenses; said lens system satisfying the following conditions: ##EQU13## where: f min is the overall focal length of the system at the wide angle position; and f max is the overall focal length of the system at the narrow angle position, so that a sufficient back focal length can be maintained in a compact lens system having a very small zoom variation, said lens system defined by the followings: ______________________________________ f = 26.0- 31.0 view angle 2ω = 81° - 70.4° L.sub.i j, k r d n ν ______________________________________ 1 58.394 L.sub.1 2.88 1.48749 70.1 2 207.958 0.10 3 34.288 L.sub.2 1.16 1.80400 46.6 4 12.987 6.28 5 -107.690 L.sub.3 1.20 1.67790 50.7 6 73.301 5.23 7 22.937 L.sub.4 2.77 1.80518 25.4 8 31.500 8.08- 3.67 9 76.441 L.sub.5 2.77 1.80610 40.9 10 -51.242 0.10 11 18.113 L.sub.6 2.13 1.80610 40.9 12 55.678 2.72 13 -46.641 L.sub.7 4.98 1.84666 23.9 14 19.433 1.15 15 -1382.853 L.sub.8 2.23 1.51823 59.0 16 -17.260 0.10 17 -196.186 L.sub.9 1.74 1.51633 64.1 18 -33.488 ______________________________________