Inverted telephoto type wide angle lens system

Claim 2

An inverted telephoto type wide angle lens system comprising: an aperture stop; a first lens group located at the object side of the aperture stop; and a second lens group located at the image side of the aperture stop, the second lens group including at least two movable focusing lens units with at least one variable air space being located between the two movable focusing lens units, the focusing being practiced by only the movement of the focusing lens units to cause a change in the variable air space, said system including other lens units which remain stationary.

Claim 3

The invention of claim 1, wherein the lens system fulfills the following condition: 0.05<|R|<1.5 wherein R represents the ratio of the amount of movement of the object side one of the focusing lens units to that of the image side one of the focusing lens units.

Claim 4

The invention of claim 2, wherein the lens system further fulfills the following condition: 0.03<(f.sub.M1 /f.sub.M2)·R<1.5 wherein: f M1 represents the focal length of the object side one of the focusing lens units; and f M2 represents the focal length of the image side one of the focusing lens units.

Claim 5

The invention of claim 3, wherein the lens system further fulfills the following condition: -0.7/f<1/fa<0.2/f 0.7f<f.sub.M2 <5.3f wherein: f represents the focal length of the whole lens system; and fa represents the focal length of a lens group defined between the front surface of the lens system and an object side surface forming an air space which is reduced by the movement of the object side one of the focusing lens units upon close focusing.

Claim 6

The invention of claim 1, wherein the lens system fulfills the following conditions: -0.7/f<1/fa<0.2/f 0.7f<f.sub.M2 <5.3f 0.05<|R|<1.5 wherein: f represents the focal length of the whole lens system; fa represents the focal length of a lens group defined between the front surface of the lens system and an object side surface forming an air space which is reduced by the movement of the object side one of the focusing lens units upon close focusing; f M2 represents the focal length of the image side one of the focusing lens units; and R represents the ratio of the amount of movement of the object side of one of the focusing lens units to that of the image side one of the focusing lens units.

Claim 7

The invention of claim 1, wherein all of the focusing lens units are of a positive refractive power and are moved toward the object side upon close focusing.

Claim 8

The invention of claim 6, wherein a stationary lens group is located in between the focusing lens units, and the focusing lens units are moved in a body.

Claim 9

The invention of claim 1, wherein the object side one of the focusing lens units is of a negative refractive power and moved toward the image side upon close focusing, while the image side one of the focusing lens units is of a positive refractive power and moved toward the object side upon close focusing.

Claim 10

The invention of claim 1, wherein the lens system fulfills the following conditions: 0.05<|R|<1.5 0.7f<f.sub.M2 <5.3f wherein: R represents the ratio of the amount of movement of the object side one of the focusing lens units to that of the image side one of the focusing lens units; f represents the focal length of the whole lens system; and f M2 represents the image side one of the focusing lens units.

Claim 11

An inverted telephoto type wide angle lens system according to the following table: __________________________________________________________________________ f = 100 F.sub.NO = 2.0 2ω = 84° Radius of Axial Refractive Abbe Curvature Distance Index Number __________________________________________________________________________ r.sub.1 217.54 L1 d.sub.1 16.00 Nd.sub.1 1.5168 νd.sub.1 64.1 r.sub.2 871.54 d.sub.2 0.41 r.sub.3 122.00 L2 d.sub.3 9.83 Nd.sub.2 1.6204 νd.sub.2 60.3 r.sub.4 54.40 d.sub.4 24.00 r.sub.5 125.98 L3 d.sub.5 8.57 Nd.sub.3 1.6204 νd.sub.3 60.3 r.sub.6 55.51 d.sub.6 16.88 r.sub.7 327.89 L4 d.sub.7 49.12 Nd.sub.4 1.7618 νd.sub.4 26.6 r.sub.8 -355.46 d.sub.8 10.00 (Aperture stop) r.sub. 9 597.62 L5 d.sub.9 9.22 Nd.sub.5 1.8052 νd.sub.5 25.4 r.sub.10 1232.92 d.sub.10* 8.00-3.754 r.sub.11 274.02 L6 d.sub.11 20.15 Nd.sub.6 1.8050 νd.sub.6 41.0 r.sub.12 -113.99 d.sub.12* 1.02-5.266 r.sub.13 -190.47 L7 d.sub.13 7.72 Nd.sub.7 1.8052 νd.sub.7 25.4 r.sub.14 130.20 d.sub.14 12.00 r.sub.15 -173.74 L8 d.sub.15 8.60 Nd.sub.8 1.6968 νd.sub.8 55.5 r.sub.16 -106.87 d.sub.16 0.41 r.sub.17 -190.96 d.sub.17 5.00 Nd.sub.9 1.8052 νd.sub.9 25.4 L9 r.sub.18 -2780.97 d.sub.18 14.50 Nd.sub.10 1.7425 νd.sub.10 52.5 r.sub.19 -126.31 d.sub.19* 12.00-4.279 r.sub.20 487.45 L10 d.sub.20 17.50 Nd.sub.11 1.6968 νd.sub.11 55.5 r.sub.21 -234.07 __________________________________________________________________________ wherein, * represents a variable air space.

Claim 12

An inverted telephoto type wide angle lens system according to the following table: __________________________________________________________________________ f = 100 F.sub.NO = 2.0 2ω = 84° Radius of Axial Refractive Abbe Curvature Distance Index Number __________________________________________________________________________ r.sub.1 217.54 L1 d.sub.1 16.00 Nd.sub.1 1.5168 νd.sub.1 64.1 r.sub.2 871.54 d.sub.2 0.41 r.sub.3 122.00 L2 d.sub.3 9.83 Nd.sub.2 1.6204 νd.sub.2 60.3 r.sub.4 54.40 d.sub.4 24.00 r.sub.5 125.98 L3 d.sub.5 8.57 Nd.sub.3 1.6204 νd.sub.3 60.3 r.sub.6 55.51 d.sub.6 16.88 r.sub.7 327.89 L4 d.sub.7 49.12 Nd.sub.4 1.7618 νd.sub.4 26.6 r.sub.8 -355.46 d.sub.8 10.00 (Aperture stop) r.sub. 9 597.62 L5 d.sub.9 9.22 Nd.sub.5 1.8052 νd.sub.5 25.4 r.sub.10 1232.92 d.sub.10* 8.00-3.754 r.sub.11 274.02 L6 d.sub.11 20.15 Nd.sub.6 1.8050 νd.sub.6 41.0 r.sub.12 -113.99 d.sub.12* 1.02-5.266 r.sub.13 -190.47 L7 d.sub.13 7.72 Nd.sub.7 1.8052 νd.sub.7 25.4 r.sub.14 130.20 d.sub.14 12.00 r.sub.15 -173.74 L8 d.sub.15 8.60 Nd.sub.8 1.6968 νd.sub.8 55.5 r.sub.16 -106.87 d.sub.16 0.41 r.sub.17 -190.96 d.sub.17 5.00 Nd.sub.9 1.8052 νd.sub.9 25.4 L9 r.sub.18 -2780.97 d.sub.18 14.50 Nd.sub.10 1.7425 νd.sub.10 52.5 r.sub.19 -126.31 d.sub.19* 12.00-4.279 r.sub.20 487.45 L10 d.sub.20 17.50 Nd.sub.11 1.6968 νd.sub.11 55.5 r.sub.21 -234.07 __________________________________________________________________________ wherein, * represents a variable air space.

Claim 13

An inverted telephoto type wide angle lens system comprising: an aperture stop; a first lens group located at the object side of the aperture stop, and a second lens group located at the image side of the aperture stop, the second lens group including at least two movable focusing lens components with at least one variable air space being located between the two movable focusing lens components, the focusing being practiced by only the movement of the focusing lens components to cause a change in the variable air space, said system including other lens components which remain stationary.

Claim 14

An inverted telephoto type wide angle lens system comprising: an aperture stop; a first lens group located at the object side of the aperture stop, and a second lens group located at the image side of the aperture stop, the second lens group including at least two movable focusing lens components with at least one variable air space being located between the two movable focusing lens components, the focusing being practiced by only the movement of the focusing lens components to cause a change in the variable air space, said system including other lens components which remain stationary.

Claim 15

The invention of claim 11, wherein the lens system fulfills the following condition: 0.05<|R|<1.5 wherein R represents the ratio of the amount of movement of the object side one of the focusing lens components to that of the image side one of the focusing lens components.

Claim 16

The invention of claim 12, wherein the lens system further fulfills the following condition: 0.03<(f.sub.M1 /f.sub.M2)·R<1.5 wherein: f M1 represents the focal length of the object side one of the focusing lens components; and f M2 represents the focal length of the image side one of the focusing lens components.

Claim 17

The invention of claim 13, wherein the lens system further fulfills the following conditions: -0.7/f<1/fa<0.2/f 0.7f/<f.sub.M2 <5.3f wherein: f represents the focal length of the whole lens system; and fa represents the focal length of a lens group defined between the front surface of the lens system and an object side surface forming an air space which is reduced by the movement of the object side one of the focusing lens components upon close focusing.

Claim 18

The invention of claim 11, wherein the lens system fulfills the following conditions: -0.7/f<1/fa<0.2/f 0.7f<f.sub.M2 <5.3f 0.05<|R|<1.5 wherein: f represents the focal length of the whole lens system; fa represents the focal length of a lens group defined between the the front surface of the lens system and an object side surface forming an air space which is reduced by the movement of the object side one of the focusing lens components upon close focusing; f M2 represents the focal length of the image side one of the focusing lens components, and R represents the ratio of the amount of movement of the object side one of the focusing lens components to that of the image side one of the focusing lens components.

Claim 19

The invention of claim 11, wherein all of the focusing lens components are of a positive refractive power and are moved toward the object side upon close focusing.

Claim 20

The invention of claim 16, wherein a stationary lens unit is located in between the focusing lens components, and the focusing lens components are moved in a body.

Claim 21

The invention of claim 11, wherein the object side one of the focusing lens component is of a negative refractive power and moved toward the image side upon close focusing, while the image side one of the focusing lens components is of a positive refractive power and moved toward the object side upon close focusing.

Claim 22

The invention of claim 11, wherein the lens system fulfills the following conditions: 0.05<|R|<1.5 0.5f<f.sub.M2 <5.3f wherein: R represents the ratio of the amount of movement of the object side one of the focusing lens components to that of the image side one of the focusing lens components; f represents the focal length of the whole lens system; and f M2 represents the image side one of the focusing lens components.