Zoom lens

A zoom lens having an object side to face an object and an image side to face an image forming plane, comprising:

• three lens groups including a first lens group having a negative refracting power, a second lens group having a positive refracting power and a third lens group having a positive refracting power arranged serially in this order from the object side,
• wherein the second lens group comprises a positive lens, a cemented lens including a positive lens and a negative lens and one lens arranged serially in this order from the object side, and when changing a magnification from a wide-angle side to a telephoto side, the first, second and third lens groups are moved on an optical axis so that a distance between the first lens group and the second lens group is reduced and a distance between the second lens group and the third lens group is increased for the magnification change,
• wherein the following conditional expression is satisfied:
• 0.4<fw/f2<1.0
• where f2 represents a focal length of the second lens group and fw represents a focal length of the total optical system at a wide-angle end,
• wherein the first lens group comprises three lenses of two negative lenses and a single positive lens,
• wherein the zoom lens satisfies the following conditional formula:
• −0.7<fw/f1<−0.3
• where f1 is a focal length of the first lens group,
• wherein the first lens group comprises three lenses of a negative meniscus lens, a negative lens and a positive lens arranged serially from the object side, and the negative meniscus has a concave surface positioned to face the image side, and
• wherein the first lens group comprises a negative meniscus lens and a composite lens arranged serially from the object side, the negative meniscus lens has a concave surface positioned to face the image side, the composite lens comprises a negative lens and a positive meniscus lens which are cemented to each other, and the positive meniscus lens has a convex surface positioned to face the object side.

A zoom lens having an object side to face an object and an image side to face an image forming plane, comprising:

• three lens groups including a first lens group having a negative refracting power, a second lens group having a positive refracting power and a third lens group having a positive refracting power arranged serially in this order from the object side,
• wherein the second lens group comprises a positive lens, a cemented lens including a positive lens and a negative lens and one lens arranged serially in this order from the object side, and when changing a magnification from a wide-angle side to a telephoto side, the first, second and third lens groups are moved on an optical axis so that a distance between the first lens group and the second lens group is reduced and a distance between the second lens group and the third lens group is increased for the magnification change,
• wherein the following conditional expression is satisfied:
• 0.4<fw/f2<1.0
• where f2 represents a focal length of the second lens group and fw represents a focal length of the total optical system at a wide-angle end,
• wherein the second lens group comprises at least one aspherical surface, and
• wherein a positive lens which is positioned closest to the object side in the second lens group has at least one aspherical surface.

A zoom lens having an object side to face an object and an image side to face an image forming plane, comprising:

• three lens groups including a first lens group having a negative refracting power, a second lens group having a positive refracting power and a third lens group having a positive refracting power arranged serially in this order from the object side,
• wherein the second lens group comprises a positive lens, a cemented lens including a positive lens and a negative lens and one lens arranged serially in this order from the object side, and when changing a magnification from a wide-angle side to a telephoto side, the first, second and third lens groups are moved on an optical axis so that a distance between the first lens group and the second lens group is reduced and a distance between the second lens group and the third lens group is increased for the magnification change,
• wherein the following conditional expression is satisfied:
• 0.4<fw/f2<1.0
• where f2 represents a focal length of the second lens group and fw represents a focal length of the total optical system at a wide-angle end,
• wherein the second lens group comprises at least one aspherical surface, and
• wherein the zoom lens satisfies the following conditional formula:
• |fw/f2i|<0.5
• where f2i is a focal length of a lens positioned closest to the image side in the second group.

A zoom lens having an object side to face an object and an image side to face an image forming plane, comprising:

• three lens groups including a first lens group having a negative refracting power, a second lens group having a positive refracting power and a third lens group having a positive refracting power arranged serially in this order from the object side,
• wherein the second lens group comprises a positive lens, a cemented lens including a positive lens and a negative lens and one lens arranged serially in this order from the object side, and when changing a magnification from a wide-angle side to a telephoto side, the first, second and third lens groups are moved on an optical axis so that a distance between the first lens group and the second lens group is reduced and a distance between the second lens group and the third lens group is increased for the magnification change,
• wherein the following conditional expression is satisfied:
• 0.4<fw/f2<1.0
• where f2 represents a focal length of the second lens group and fw represents a focal length of the total optical system at a wide-angle end, and
• wherein the third lens group comprises a single lens having a positive refracting power.