Patent ID: 6545817
Filing Date: 2003-04-08
Classification: G02B

Abstract:
A zoom lens system comprising, sequentially from the enlarging side to the reducing side:a first lens unit having negative optical power; a second lens unit having positive optical power, the second lens unit having a positive lens element positioned nearest the reducing side; a diaphragm; a third lens unit having positive optical power; the third lens unit comprising, sequentially from the enlarging side to reducing side, a cemented lens unit having a positive lens element and a negative lens element with a concave surface facing the reducing side, and a positive lens element having a concave surface facing the reducing side; a fourth lens unit having negative optical power; and a fifth lens unit having positive optical power; wherein the second lens unit, the third lens unit, and the fourth lens unit move from the enlarging side to the reducing side when zooming from the telephoto end to the wide angle end, and wherein the zoom lens system satisfies the condition below: âˆ’1.5fw/r2A)+(fw/r3A)where fw represents the focal length of the entire system at the wide angle end, r2A represents the radius of curvature of the surface on the enlarging side of the lens element positioned nearest the reducing side of the second lens unit, and r3A represents the radius of curvature of the surface nearest the enlarging side of the third lens unit.