High zoom-ratio finite-distance zoom lens

Claim 2

A high zoom-ratio finite-distance zoom lens having a fixed object-to-image distance which comprises, in order from one side thereof, a first lens unit having a positive focal length, a second lens unit having a negative focal length, a third lens unit having a positive focal length, and a fourth lens unit having a positive focal length, said lens being capable of zooming from a first degree of magnification to a second degree of magnification by means of displacing the first, third and fourth lens units towards said one side, and satisfying the following five conditions: 0.3<m.sub.s /m.sub.1s <0.6 (1) 1.8<m.sub.2L /m.sub.2s <2.6 (2) 1.7<m.sub.4L /m.sub.4s <2.5 (3) 0.1<X.sub.3 /X.sub.4 <0.9 (4) 0.9<ENP.sub.L /f.sub.L <1.8 (5) where m s : a magnification of the overall system at the first magnification degree end; m 1s : a magnification of the first lens unit at the first magnification degree end; m 2s : a magnification of the second lens unit at the first magnification degree end; m 4s : a magnification of the fourth lens unit at the first magnification degree end; m 2L : a magnification of the second lens unit at the second magnification degree end; m 4L : a magnification of the fourth lens unit at the second magnification degree end; X 3 : an amount of displacement of the third lens unit; X 4 : an amount of displacement of the fourth lens unit; ENP L : a position of an entrance pupil (distance from the first lens surface) at the high magnification end; and f L : a focal length of the overall system at the second magnification degree end.

Claim 3

A high zoom-ratio finite-distance zoom lens according to claim 1 wherein the first lens unit comprises: in order from said one side, a first lens element with a negative meniscus, a second positive lens element, a third lens element with a negative meniscus, a fourth positive lens element, and a fifth positive lens element, each of the five lens elements having a convex surface on the side facing said one side.

Claim 4

A high zoom-ratio finite-distance zoom lens according to claim 2 wherein the three positive lens elements (the second, fourth and fifth lens elements) in said first lens unit satisfy the following condition: ν.sub.1p >63 (6) where ν 1p is the mean Abbe number of said three positive lens elements in said first lens unit.

Claim 5

A high zoom-ratio finite-distance zoom lens according to claim 1 wherein the second lens unit comprises: in order said one side, at least two and less than four negative lens elements and a positive lens element having a convex surface on the side facing said one side.

Claim 6

A high zoom-ratio finite-distance zoom lens according to claim 1 wherein the third lens unit comprises a single positive lens element.

Claim 7

A high zoom-ratio finite-distance zoom lens according to claim 1 wherein the fourth lens unit comprises: in order from said one side, a positive lens element having a convex surface on the side facing said one side, a negative-meniscus lens element having a concave surface on the side facing said one side, a cemented lens composed of a negative lens element and a biconvex positive lens element, a negative-meniscus lens element having a concave surface on the side facing said one side, and a positive lens element having a convex surface on the side facing said one side.

Claim 8

A high zoom-ratio finite-distance zoom lens according to claim 1 wherein the first and fourth lens units are displaced together.

Claim 9

A high zoom-ratio finite-distance zoom lens according to claim 1 wherein the second lens unit is fixed with respect to the plane of the side opposite said one side.

Claim 10

A high zoom-ratio finite distance zoom lens according to claim 1 wherein said one side is an object side and wherein said first magnification degree is less than said second magnification degree.

Claim 11

A high zoom-ratio finite-distance zoom lens according to claim 1 wherein said first magnification degree is 1/12.4, said second magnification degree is 1/3.1 and said lens elements satisfy a following table wherein r i is a radius of curvature of an i-th lens element surface, d i is a thickness of a lens element or an aerial distance between two adjacent lens element, N i is a refractive index and v i is an Abbe index of the lens element having the i-th lens element surface facing said one side and wherein said table is: ______________________________________ i r.sub.i d.sub.i N.sub.i ν.sub.i ______________________________________ 1 159.718 3.500 1.60342 38.0 2 63.584 1.956 3 67.000 11.300 1.61800 63.4 4 -722.505 0.250 5 77.216 2.850 1.80518 25.4 6 48.651 8.200 1.48749 70.1 7 143.202 0.200 8 45.470 7.900 1.61800 63.4 9 194.955 2.300-28.42 10 -1608.176 1.500 1.77250 49.6 11 15.000 1.333 12 31.514 1.450 1.69680 55.5 13 20.769 2.223 14 -42.300 1.400 1.69680 55.5 15 73.875 0.100 16 26.650 2.700 1.80518 25.4 17 -725.128 20.505-2.5 18 45.821 1.700 1.69680 55.5 19 125.182 11.618-3.5 20 19.823 2.400 1.69680 55.5 21 47.326 2.834 22 -25.362 1.400 1.53172 48.9 23 -45.096 3.776 24 106.198 1.500 1.83400 37.2 25 17.350 8.500 1.48749 70.1 26 -17.350 4.162 27 -15.600 1.500 1.80610 40.9 28 -26.112 0.100 29 46.238 3.200 1.54814 45.8 30 -184.648 ______________________________________

Claim 12

A high zoom-ratio finite-distance zoom lens according to claim 1 wherein said first magnification degree is 1/12.4, said second magnification degree is 1/3.1 and said lens elements satisfy a following table wherein r i is a radius of curvature of an i-th lens element surface, d i is a thickness of a lens element or an aerial distance between two adjacent lens elements, N i is a refractive index and v i is an Abbe index of the lens element having the i-th lens element surface on said one side and wherein said table is: ______________________________________ i r.sub.i d.sub.i N.sub.i ν.sub.i ______________________________________ 1 168.138 3.500 1.60342 38.0 2 58.686 3.989 3 63.616 12.000 1.61800 63.4 4 -465.854 0.100 5 90.013 2.850 1.80518 25.4 6 54.096 8.000 1.48749 70.1 7 169.871 0.200 8 45.588 7.900 1.61800 63.4 9 198.737 2.300-28.63 10 2818.623 1.500 1.77250 49.6 11 13.866 3.373 12 -43.348 1.400 1.77250 49.6 13 43.348 0.411 14 25.982 2.700 1.80518 25.4 15 -220.685 21.349-2.5 16 44.514 1.700 1.69680 55.5 17 101.824 10.976-3.5 18 16.552 2.400 1.69680 55.5 19 28.403 3.220 20 -22.100 1.400 1.53172 48.9 21 -43.520 2.528 22 48.045 1.500 1.83400 37.2 23 16.043 8.500 1.48749 70.1 24 -16.043 3.603 25 -13.443 1.500 1.80610 40.9 26 -22.439 0.100 27 39.713 3.200 1.54814 45.8 28 309.057 ______________________________________

Claim 13

A high zoom-ratio finite-distance zoom lens according to claim 1 wherein said first magnification degree is 1/14, said second magnification degree is 1/3.5 and said lens elements satisfy a following table wherein r i is a radius of curvature of an i-th lens element surface, d i is a thickness of a lens element or an aerial distance between two adjacent lens element, N i is a refractive index and v i is an Abbe index of the lens element having the i-th lens element surface on said one side and wherein said table is: ______________________________________ i r.sub.i d.sub.i N.sub.i ν.sub.i ______________________________________ 1 1320.564 3.400 1.59551 39.2 2 68.727 3.292 3 74.591 12.243 1.61800 63.4 4 -192.688 0.250 5 74.502 2.850 1.80518 25.4 6 49.504 8.024 1.48749 70.1 7 158.671 0.128 8 42.831 7.943 1.61800 63.4 9 140.480 2.300-27.75 10 -684.017 1.500 1.77250 49.6 11 16.280 1.107 12 34.531 1.400 1.77250 49.6 13 18.492 2.291 14 -35.897 1.300 1.69680 55.5 15 119.666 0.100 16 29.082 2.500 1.80518 25.4 17 -150.836 17.749-2.0 18 39.987 1.700 1.69680 55.5 19 95.778 13.031-3.45 20 15.953 2.400 1.69680 55.5 21 36.985 2.074 22 -35.833 1.300 1.53172 48.9 23 192.527 3.339 24 37.018 1.500 1.83400 37.2 25 14.096 8.900 1.48749 70.1 26 -14.096 1.958 27 -12.279 1.500 1.83481 42.7 28 -21.801 0.100 29 35.301 3.000 1.54072 47.2 30 161.685 ______________________________________