Zoom lens
AssigneesOptical Logic Inc., Kantatsu Co., Ltd.
InventorYoji Kubota
Life of this patent
Estimating the term…
Abstract
A zoom lens includes a first lens group that has a lens having negative refractive power and a light path changing member; a second lens group that includes a lens having positive refractive power and a lens having negative refractive power, and has negative refractive power as a whole; a third lens group that includes a stop, a front group lens having positive refractive power, and a rear group lens having negative refractive power, and has positive refractive power as a whole; and a fourth lens group having positive or negative refractive power. Upon changing magnification from a wide-angle end to a telephoto end, the first lens group and the fourth lens group are fixed. The second lens group moves to the object side after the second lens group moves to an image side, and the third lens group linearly moves to the object side.
Claims8
A zoom lens comprising:
- a first lens group including a lens having negative refractive power and a light path changing member for changing a traveling direction of an incident light beam, said first lens group having negative refractive power as a whole;
- a second lens group including two lenses, i.e., a lens having positive refractive power and a lens having negative refractive power, and having negative refractive power, as a whole;
- a third lens group including a stop, a front group lens having positive refractive power, and a rear group lens having negative refractive power arranged in this order, and having positive refractive power as a whole;
- and
- a fourth lens group having positive or negative refractive power arranged in this order from an object side,
- wherein said first lens group and said fourth lens group are fixed,
- said second lens group moves to the object side after the second lens group moves to an image side,
- said third lens group linearly moves to the object side upon changing a magnification of the zoom lens from a wide-angle end to a telephoto end, and
- said second lens group has a focal length f2, the lens having positive refractive power in the second lens group has a focal length f2p so that the following conditional expression is satisfied:
- −1.0<f2/f2p<−0.1
- said front group lens having positive refractive power in the third lens group has a focal length f3 and said rear group lens having negative refractive power in the third lens group has a focal length f3n so that the following conditional expression is satisfied:
- |f3p/f3n|<0.7.
Dependencies are inferred from the claim text.