Zoom lens and projection display device which uses same

A zoom lens comprising, in order from an enlarging side along an optical axis:

• a first lens group having negative refractive power that is movable for focusing and that is stationary during zooming;
• a second lens group having positive refractive power that moves during zooming;
• a third lens group having negative refractive power that moves during zooming;
• a fourth lens group having negative refractive power that moves during zooming;
• and
• a fifth lens group having positive refractive power that is stationary during zooming;
• wherein
• the second lens group, said third lens group, and said fourth lens group move relative to one another along the optical axis of the zoom lens during zooming, and
• the following conditions are satisfied:
• −2.2<F1/F<−1.2
• 0.6<F2/F<1.1
• −15.0<F4/F<−1.5
• 0.7<F5/F<1.2
• where
• F1 is the focal length of the first lens group,
• F2 is the focal length of the second lens group,
• F4 is the focal length of the fourth lens group,
• F5 is the focal length of the fifth lens group, and
• F is the focal length of the zoom lens at the wide-angle end when the zoom lens is focused at infinity on the enlarging side.

A zoom lens formed of only five lens groups, arranged in order from an enlarging side along an optical axis:

• a first lens group having negative refractive power that is movable for focusing and that is stationary during zooming;
• a second lens group having positive refractive power that moves during zooming;
• a third lens group having negative refractive power that moves during zooming;
• a fourth lens group having negative refractive power that moves during zooming;
• and
• a fifth lens group having positive refractive power that is stationary during zooming;
• wherein:
• the second lens group, said third lens group and said fourth lens group move relative to one another along the optical axis of the zoom lens during zooming,
• the second lens group moves toward the enlarging side during zooming from the wide-angle end to the telephoto end, and
• the fourth lens group is positioned nearer the reducing side when at the telephoto end than when at the wide-angle end.

A zoom lens formed of only five lens groups, arranged in order from an enlarging side along an optical axis:

• a first lens group having negative refractive power that is movable for focusing and that is stationary during zooming;
• a second lens group having positive refractive power that moves during zooming;
• a third lens group having negative refractive power that moves during zooming;
• a fourth lens group having negative refractive power that moves during zooming;
• and
• a fifth lens group having positive refractive power that is stationary during zooming;
• wherein:
• the second lens group, said third lens group, and said fourth lens group move relative to one another along the optical axis of the zoom lens during zooming, and
• the following conditions are satisfied:
• −2.2<F1/F<−1.2
• 0.6<F2/F<1.1
• −15.0<F4/F<−1.5
• 0.7<F5/F<1.2
• where
• F1 is the focal length of the first lens group,
• F2 is the focal length of the second lens group,
• F4 is the focal length of the fourth lens group,
• F5 is the focal length of the fifth lens group, and
• F is the focal length of the zoom lens at the wide-angle end when the zoom lens is focused at infinity on the enlarging side.