Zoom lens system

Claim 2

A zoom lens system of an inverted telephoto type comprising, from the object side to the image side; a first lens group of a negative refractive power consisting of, from the object side to the image side, a first negative component, and a second positive component of a positive meniscus lens convex to the object side, at least one of the refractive surfaces in the first lens group being aspheric; a second lens group of a positive refractive power with a variable air space formed between the first and second lens groups, consisting of from the object side to the image side, a third positive component, a fourth positive component, a fifth negative component, and a sixth positive component, the variable air space being varied during a zooming operation; wherein the shortest focal length of the zoom lens system is less than the length of the diagonal line of the image plane; and wherein the zoom lens system fulfills the following conditions: 2.3fs<l<2.75fs 0.55fs<γ.sub.3 <1.8fs wherein: l represents the axial distance from the object side surface of the first component to the image plane of the whole lens system in the longest focal length condition; γ 3 represents the radius of curvature of the object side surface of the second component; and fs represents the focal length of the whole lens system in the shortest focal length condition.

Claim 3

A zoom lens system as claimed in claim 1, wherein the object side surface of the first component is aspheric.

Claim 4

A zoom lens system as claimed in claim 1, wherein the image side surface of the second component is aspheric.

Claim 5

A zoom lens system as claimed in claim 1, wherein a component which has an aspheric surface includes a lens element having two spherical refractive surfaces and a thin transparent layer disposed on one of the refractive surfaces in the lens element, the thin transparent layer having an aspheric surface which faces to the air.

Claim 6

A zoom lens system as claimed in claim 4, wherein the lens element is different in dispersion from the thin transparent layer.

Claim 7

A zoom lens system as claimed in claim 1, wherein the zoom lens system further fulfills the following condition: 2.55fs<l<2.75fs 0.75fs<r.sub.3 <1.8fs.

Claim 8

A zoom lens system comprising the following design parameters: ______________________________________ f = 68.2˜50.0˜36.0 Fno. = 4.1 Radius of Axial Refractive Abbe Curvature Distance Index (Nd) Number (νd) ______________________________________ γ1 121.647 d.sub.1 2.000 N.sub.1 1.74400 ν.sub.1 44.93 γ2 24.152 I d.sub.2 7.000 γ3 28.562 d.sub.3 4.300 N.sub.2 1.75520 ν.sub.2 27.51 γ4 44.012 d.sub.4 0.800˜16.86˜40.27 γ5 34.035 d.sub.5 3.000 N.sub.3 1.67000 ν.sub.3 57.07 γ6 -291.280 d.sub.6 0.150 γ7 22.420 d.sub.7 2.800 N.sub.4 1.67000 ν.sub.4 57.07 γ8 82.592 II d.sub.8 3.899 γ9 -118.156 d.sub.9 3.680 N.sub.5 1.75000 ν.sub.5 25.14 γ10 18.081 d.sub.10 3.600 γ11 2547.965 d.sub.11 2.800 N.sub.6 1.70055 ν.sub.6 30.11 γ12 -33.806 B = 0.35960602 × 10.sup.-6 C = 0.41911782 × 10.sup.-9 D = 0.8261163 × 10.sup.-12 ______________________________________ wherein: γ 1 * is the aspheric surface expressed as follows: ##EQU2## wherein: X represents the coordinate along the optical axis measured from the top of the basic spherical surface; Y represents the coordinate perpendicular to the optical axis measured from the optical axis (height from the optical axis); γ i represents the radius of curvature of the basic spherical surface; and B, C, and D represent the aspheric surface coefficients, respectively.

Claim 9

A zoom lens system comprising the following design parameters: ______________________________________ f = 68.2˜50.0˜36.0 Fno. = 4.1 Radius of Axial Refractive Abbe Curvature Distance Index (Nd) Number (νd) ______________________________________ γ1 121.647 d.sub.1 2.000 N.sub.1 1.74400 ν.sub.1 44.93 γ2 24.152 I d.sub.2 7.000 γ3 28.562 d.sub.3 4.300 N.sub.2 1.75520 ν.sub.2 27.51 γ4 44.012 d.sub.4 0.800˜16.86˜40.27 γ5 34.035 d.sub.5 3.000 N.sub.3 1.67000 ν.sub.3 57.07 γ6 -291.280 d.sub.6 0.150 γ7 22.420 d.sub.7 2.800 N.sub.4 1.67000 ν.sub.4 57.07 γ8 82.592 II d.sub.8 3.899 γ9 -118.156 d.sub.9 3.680 N.sub.5 1.75000 ν.sub.5 25.14 γ10 18.081 d.sub.10 3.600 γ11 2547.965 d.sub.11 2.800 N.sub.6 1.70055 ν.sub.6 30.11 γ12 -33.806 B = 0.35960602 × 10.sup.-6 C = 0.41911782 × 10.sup.-9 D = 0.8261163 × 10.sup.-12 ______________________________________ wherein: γ 1 * is the aspheric surface expressed as follows: ##EQU2## wherein: X represents the coordinate along the optical axis measured from the top of the basic spherical surface; Y represents the coordinate perpendicular to the optical axis measured from the optical axis (height from the optical axis); γ i represents the radius of curvature of the basic spherical surface; and B, C, and D represent the aspheric surface coefficients, respectively.

Claim 10

A zoom lens system of an inverted telephoto type comprising, from the object side to the image side: a first lens group of a negative refractive power consisting of, from the object side to the image side, a first negative component, and a second positive component of a positive meniscus lens convex to the object side, at least one of the first and second components is a composite lens element of a high dispersion glass with a thin layer of a lower dispersion material to form an aspheric refractive surface; a second lens group of a positive refractive power with a variable air space formed between the first and second lens groups, consisting of from the object side to the image side, a third positive component, a fourth positive component, a fifth negative component, and a sixth positive component, the variable air space being varied in a zooming operation; wherein the shortest focal length of the zoom lens system is less than the length of the diagonal line of the image plane; and wherein the zoom lens system fulfills the following conditions: 2.3fs<l<2.75fs 0.55fs<γ.sub.3 <1.8fs wherein: l represents the axial distance from the object side surface of the first component to the image plane of the whole lens system in the longest focal length condition; γ 3 represents the radius of curvature of the object side surface of the second component; and fs represents the focal length of the whole lens system in the shortest focal length condition.

Claim 11

A zoom lens system of an inverted telephoto type comprising, from the object side to the image side: a first lens group of a negative refractive power consisting of, from the object side to the image side, a first negative component, and a second positive component of a positive meniscus lens convex to the object side, at least one of the first and second components is a composite lens element of a high dispersion glass with a thin layer of a lower dispersion material to form an aspheric refractive surface; a second lens group of a positive refractive power with a variable air space formed between the first and second lens groups, consisting of from the object side to the image side, a third positive component, a fourth positive component, a fifth negative component, and a sixth positive component, the variable air space being varied in a zooming operation; wherein the shortest focal length of the zoom lens system is less than the length of the diagonal line of the image plane; and wherein the zoom lens system fulfills the following conditions: 2.3fs<l<2.75fs 0.55fs<γ.sub.3 <1.8fs wherein: l represents the axial distance from the object side surface of the first component to the image plane of the whole lens system in the longest focal length condition; γ 3 represents the radius of curvature of the object side surface of the second component; and fs represents the focal length of the whole lens system in the shortest focal length condition.

Claim 12

A zoom lens system as claimed in claim 8, wherein the zoom lens system fulfills the following conditions: 2.55fs<l<2.75fs 0.75fs<r.sub.3 <1.8fs.