US 6,982,835 B2 | ||
Four-group zoom lens | ||
Ukyo Tomioka, Saitama (Japan) | ||
Assigned to Fujinon Corporation, Saitama (Japan) | ||
Filed on Jan. 30, 2004, as Appl. No. 10/766,809. | ||
Claims priority of application No. 2003-028495 (JP), filed on Feb. 05, 2003. | ||
Prior Publication US 2004/0184159 A1, Sep. 23, 2004 | ||
Int. Cl. G02B 15/14 (2006.01) |
U.S. Cl. 359—687 | 12 Claims |
1. A zoom lens formed of only four lens groups arranged along an optical axis, in order from the object side, as follows:
a first lens group having positive refractive power;
a second lens group having negative refractive power;
a third lens group having positive refractive power; and
a fourth lens group having positive refractive power; wherein
the first lens group and the third lens group do not move during zooming;
the second and fourth lens groups are moved along the optical axis during zooming;
the first lens group includes, in order from the object side, a first lens element having negative refractive power, a second
lens element having positive refractive power and a convex lens surface on the object side that is cemented to the first lens
element, a third lens element, and a fourth lens element having positive refractive power and a convex lens surface on the
object side;
the fourth lens group includes, in order from the object side, a first lens element having positive refractive power and a
convex lens surface on the object side, a second lens element having a biconcave shape, a third lens element having positive
refractive power, and a fourth lens element having positive refractive power; and
the following conditions are satisfied:
νd1<45
Nd2<1.52
νd2>63
where
νd1 is the Abbe number of the first lens element of the first lens group at the d-line,
Nd2 is the refractive index of the second lens element of the first lens group at the d-line, and
νd2 is the Abbe number of the second lens element of the first lens group at the d-line.
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