Patent ID: 7423812

Claim:
A zoom lens comprising an optical system made up of a plurality of lens elements or a plurality of lens groups, wherein the following conditional expression (1) is satisfied with respect to a maximum effective aperture and a size of an image circle, and the following conditional expressions (2), (3) are satisfied with respect to an angle of view and brightness, respectively: 1.00 <φL/φI< 1.60 (1) 55<BW<70 (2) 1.8<FN<2.9 (3) where, φL: maximum effective aperture of a lens system; φI: diameter of a minimum-sized circle which encapsulates a whole image display unit on a reducing side image plane about an optical axis; BW: total angle of view relative to an image point with φI, when focused to an object distance of 1700 mm from an enlarging side first surface when a focusing operation is available, and at a wide-angle end in the case of a zoom lens; FN: full-aperture F value of a whole lens system, when focused to the object distance of 1700 mm from the enlarging side first surface when the focusing operation is available, at a minimum value in the case of the zoom lens.