Ultra compact zoom lens system

Claim 2

An ultra compact zoom lens system, comprising from object side to image side: a first lens unit of a positive refractive power; a second lens unit of a negative refractive power with a first variable air space formed between the first and second lens units; a third lens unit of a positive refractive power; and a fourth lens unit of a negative refractive power with a second variable air space formed between the third and fourth lens units; wherein the first lens unit is shiftable from the image side to the object side while increasing the first variable air space in the zooming operation from the shortest focal length to the longest focal length; and wherein the fourth lens unit is shiftable from the image side to the object side while decreasing the second variable air space in the zooming operation from the shortest focal length to the longest focal length.

Claim 3

An ultra compact zoom lens system as claimed in claim 1, wherein the lens system fulfills the following condition: -0.5<α+γ<2.0 provided that ##EQU16## wherein,

Claim 4

φ 1 . φ 2 , φ 3 , and φ 4 represent the refractive powers of the first to fourth lens units, respectively, when the shortest focal length of the whole lens system is normalized to 1, f 1 represents the focal length of the first lens unit when the shortest focal length of the whole lens system is normalized to 1, Z represents the zoom ratio of the whole lens system, b represents the back focal length of the whole lens system for the shortest focal length when the shortest focal length of the whole lens system is normalized to 1.

Claim 5

φ 1 . φ 2 , φ 3 , and φ 4 represent the refractive powers of the first to fourth lens units, respectively, when the shortest focal length of the whole lens system is normalized to 1, f 1 represents the focal length of the first lens unit when the shortest focal length of the whole lens system is normalized to 1, Z represents the zoom ratio of the whole lens system, b represents the back focal length of the whole lens system for the shortest focal length when the shortest focal length of the whole lens system is normalized to 1.

Claim 6

An ultra compact zoom lens system as claimed in claim 1, wherein the zoom lens system fulfills the following condition: ##EQU17##

Claim 7

wherein, φ 1 . φ 2 , φ 3 , and φ 4 represent the refractive powers of the first to fourth lens units, respectively, when the shortest focal length of the whole lens system is normalized to 1, f 1 represents the focal length of the first lens unit when the shortest focal length of the whole lens system is normalized to 1, Z represents the zoom ratio of the whole lens system, b represents the back focal length of the whole lens system for the shortest focal length when the shortest focal length of the whole lens system is normalized.

Claim 8

wherein, φ 1 . φ 2 , φ 3 , and φ 4 represent the refractive powers of the first to fourth lens units, respectively, when the shortest focal length of the whole lens system is normalized to 1, f 1 represents the focal length of the first lens unit when the shortest focal length of the whole lens system is normalized to 1, Z represents the zoom ratio of the whole lens system, b represents the back focal length of the whole lens system for the shortest focal length when the shortest focal length of the whole lens system is normalized.

Claim 9

An ultra compact zoom lens system as claimed in claim 3, wherein the lens system further fulfills the following conditions: -0.5<α21 1.5 -1.5<γ<0.5 wherein, α represents -(1+φ 2 /φ 1 ), and γ represents -(φ 3 φ 4 )/φ 1 .

Claim 10

An ultra compact zoom lens system as claimed in claim 3, wherein the lens system further fulfills the following conditions: 1<α<3 -3<γ<1 wherein, α represents -(1+φ 2 /φ 1 ), and γ represents -φ 3 +φ 4 /φ 4 .

Claim 11

An ultra compact zoom lens system as claimed in claim 3, wherein the lens system further fulfills the following conditions: ##EQU18## wherein, α represents -(1+φ 2 /φ 1 ), and γ represents -(100 3 +φ 4 )/φ 1 .

Claim 12

An ultra compact zoom lens system as claimed in claim 6, wherein the lens system further fulfills the following conditions: 0<1/β.sub.2.sbsb.L <1 0<β.sub.3.sbsb.L <1 0<1/β.sub.4.sbsb.L <L wherein, β 2 .sbsb.L, β 3 .sbsb.L and β 4 .sbsb.L represent lateral magnification of the second, third and fourth lens units respectively for the longest focal length.

Claim 13

An ultra compact zoom lens system as claimed in claim 7, wherein the lens system further fulfills the following condition: 0.2<f.sub.S.sbsb.123 /|f.sub.4 |<2.0 wherein, f S .sbsb.123 represents the compound focal length of the first to third lens units for the shortest focal length, and f 4 represents the focal length of the fourth lens unit.

Claim 14

An ultra compact zoom lens system as claimed in claim 8, wherein the lens system further fulfills the following conditions: 1.15<β.sub.4.sbsb.L /β.sub.4.sbsb.S <2.0 0.1<Δd.sub.34 /f.sub.S <1.0 wherein, B 4 .sbsb.S represents the lateral magnification of the fourth lens unit for the shortest focal length, Δd 34 represents the decreasing axial amount of the second variable air space in the zooming operation from the shortest focal length to the longest focal length, and f S represents the focal length of the whole lens system.

Claim 15

An ultra compact zoom lens system as claimed in claim 9, wherein the third lens unit is fixed along the optical axis in the zooming operation.

Claim 16

An ultra compact zoom lens system as claimed in claim 9, wherein the second lens unit is fixed along the optical axis in the zooming operation.

Claim 17

An ultra compact zoom lens system as claimed in claim 9, wherein the fourth lens unit is shifted integrally with the first lens unit in the zooming operation.

Claim 18

An ultra compact zoom lens system comprising the following design parameters; ______________________________________ f = 102.5˜140.0˜195.0 F.sub.NO. = 4.5 Abbe radius of axial refractive number curvature distance index (Nd) (νd) ______________________________________ r1 62.096 d1 2.200 N1 1.80518 ν1 25.43 r2 44.325 d2 1.300 r3 46.360 d3 6.100 N2 1.62041 ν2 60.29 r4 798.824 d4 3.500˜ 32.040˜ 65.701 r5 -85.141 d5 1.500 N3 1.71300 ν3 53.93 r6 88.239 d6 2.000 N4 1.80518 ν4 25.43 r7 617.791 d7 38.069˜ 21.304˜ 5.000 r8 55.510 d8 1.600 N5 1.84666 ν5 23.83 r9 28.939 d9 1.100 r10 32.136 d10 4.500 N6 1.72000 ν6 52.14 r11 -82.898 d11 31.132˜ 19.357˜ 2.000 r12 220.759 d12 4.000 N7 1.67339 ν7 29.25 r13 -30.975 d13 1.500 N8 1.74400 ν8 44.93 r14 41.862 ______________________________________

Claim 19

An ultra compact zoom lens system comprising the following design parameters; ______________________________________ f = 102.5˜140.0˜195.0 F.sub.NO. = 4.5 Abbe radius of axial refractive number curvature distance index (Nd) (νd) ______________________________________ r1 62.096 d1 2.200 N1 1.80518 ν1 25.43 r2 44.325 d2 1.300 r3 46.360 d3 6.100 N2 1.62041 ν2 60.29 r4 798.824 d4 3.500˜ 32.040˜ 65.701 r5 -85.141 d5 1.500 N3 1.71300 ν3 53.93 r6 88.239 d6 2.000 N4 1.80518 ν4 25.43 r7 617.791 d7 38.069˜ 21.304˜ 5.000 r8 55.510 d8 1.600 N5 1.84666 ν5 23.83 r9 28.939 d9 1.100 r10 32.136 d10 4.500 N6 1.72000 ν6 52.14 r11 -82.898 d11 31.132˜ 19.357˜ 2.000 r12 220.759 d12 4.000 N7 1.67339 ν7 29.25 r13 -30.975 d13 1.500 N8 1.74400 ν8 44.93 r14 41.862 ______________________________________