Zoom lens, and electronic imaging system using the same

A zoom lens, comprising in order from an object side thereof,

• a first lens group that has negative refracting power, includes a reflecting optical element for bending an optical path, and remains fixed during zooming,
• a second lens group that has positive refracting power and moves only toward the object side of the zoom lens upon zooming from a wide-angle end to a telephoto end of the zoom lens,
• a third lens group that moves in a locus different from that of the second lens group upon the zooming, and
• a fourth lens group having an aspheric surface, wherein:
• two lens groups defined by the second lens group and the third lens group comprise a total of up to three lens components including at least one double component, and
• the following condition (41) is satisfied:
• 1.0<−βRt<2.6 (41)
• where βRt is a composite magnification of the second lens group and subsequent lens group or groups at the telephoto end upon focused on an infinite object point.

A zoom lens, comprising in order from an object side thereof,

• a first lens group that has negative refracting power, includes a reflecting optical element for bending an optical path, and remains fixed during zooming,
• a second lens group that has positive refracting power and moves only toward the object side of the zoom lens upon zooming from a wide-angle end to a telephoto end of the zoom lens,
• a third lens group that moves in a locus different from that of the second lens group upon the zooming, and
• a fourth lens group having an aspheric surface, wherein:
• the first lens group comprises, in order from an object side thereof, a front subgroup comprising a negative lens element,
• the reflecting optical element for bending an optical path, and a rear subgroup having negative refracting power, and
• the following conditions (47) and (48) are satisfied:
• 0.5<(R11F+R11R)/(R11F−R11R)<5.0 (47) 0<f11/f12<1.2 (48)
• where R11F is an axial radius of curvature of an object side-surface of the negative lens element in the front subgroup in the first lens group, R11R is an axial radius of curvature of an image side-surface of the negative lens element in the front subgroup in the first lens group, f11 is a focal length of the front subgroup in the first lens group, and f12 is a focal length of the rear subgroup in the first lens group.