Patent ID: 6542311
Filing Date: 2003-04-01
Classification: G02B

Abstract:
A zoom lens comprising successively from an enlargement side:a first lens group, fixed upon changing power, having a negative refracting power for focusing; a second lens group having a positive refracting power, a third lens group having a positive refracting power, and a fourth lens group having a negative refracting power which are movable with a mutual relationship for continuously changing power and correcting an image surface movement generated by said continuous change in power; and a fifth lens group, fixed upon changing power, having a positive refracting power; said zoom lens satisfying the following conditions (1) to (4): âˆ’1.51/F0.7â€ƒâ€ƒ(1) 0.52/F<1.5â€ƒâ€ƒ(2) 5.03/F<15.0â€ƒâ€ƒ(3) 0.85/F<1.5â€ƒâ€ƒ(4) whereF is the focal length of the whole lens system at a wide-angle end; F1 is the focal length of the first lens group; F2 is the focal length of the second lens group; F3 is the focal length of the third lens group; and F5 is the focal length of the fifth lens group.