Patent ID: 7944621
Filing Date: 2011-05-17
Classification: G02B

Abstract:
1. A zoom lens system comprising, arranged sequentially from the enlarging side to the reducing side, a first lens group having a negative refractive power as a whole and including, arranged sequentially from the enlarging side to the reducing side, a lens having a negative refractive power and of meniscus convex toward the enlarging side, a lens having a negative refractive power and a lens having a positive refractive power; a second lens group having a positive refractive power as a whole and including, arranged sequentially from the enlarging side to the reducing side, a lens having a positive refractive power, a second lens having a positive refractive power, a lens having a negative refractive power, a biconvex lens having a positive refractive power and a lens having a negative refractive power and of meniscus convex toward the enlarging side; and a third lens group having a positive refractive power as a whole and including a single lens having a positive refractive power; and wherein: the first lens group is adapted to move along an optical axis from the enlarging side to the reducing side during zooming from the wide angle end to the intermediate area, and also move along the optical axis from the reducing side to the enlarging side during zooming from the intermediate area to the telephoto end; and the second lens group is adapted to move along the optical axis from the reducing side to the enlarging side during zooming from the wide angle end to the telephoto end with the third lens group fixed during the zooming operation; and wherein: the distance on the optical axis between a focused position and the enlarging side face of the lens of the first lens group disposed on the most enlarging side at the wide angle end satisfies a conditional expression (1) below; a positional relationship between the second and third lens groups at the wide angle end satisfies a conditional expression (2) below; the magnification of the second lens group at the wide angle end satisfies a conditional expression (3) below; the refractive power of the first lens group satisfies a conditional expression (4); and the magnification of the second lens group at the telephoto end satisfies a conditional expression (5) below: where TL is the distance on the optical axis between the focused position and the enlarging side face of the lens disposed on the most enlarging side of the first lens group at the wide angle end (in a focused state where the distance between the most enlarging side face of the first lens group and a subject which the most enlarging side face of the first lens group faces is 1700 mm); f d f m m