Zoom lens and image pickup apparatus

An image pickup apparatus comprising:

• a zoom lens;
• and
• an imaging device for converting an optical image formed by the zoom lens into an electrical signal,
• wherein the zoom lens is constructed by, in order from an object side, a first lens group having a negative power, a second lens group having a positive power, and a third lens group having a positive power, and
• wherein at least the first lens group and the second lens group are movable during a change from a wide-angle end state in which a focal length becomes shortest to a telephoto end state in which the focal length becomes longest;
• the first lens group is constructed of a glass lens having a negative power and a plastic lens having a positive power;
• the second lens group includes a single plastic lens having a negative power;
• the third lens group includes at least one plastic lens having a positive power;
• and
• the following conditional expressions (1), (2), (3), (4), (5), and (6) are satisfied:
• α>2.5;
• (1)
• lw/(α·Y)<4.5;
• (2)
• |φP1/φ1|≦0.55;
• (3)
• |φP2/φ2|≦0.3;
• (4)
• |φP1/φt|<0.7;
• and (5)
• |φP2/φt|<0.4, (6)
• where
• α is a zoom ratio (=focal length of a total system at a telephoto end/focal length of the total system at a wide-angle end);
• φ1 is a power of the first lens group;
• φP1 is a power of the plastic lens having a positive power in the first lens group;
• φ2 is a power of the second lens group;
• φP2 is a power of the plastic lens having a negative power in the second lens group;
• φt is power at the telephoto end of the total system;
• lw is a total optical length at the wide-angle end;
• and
• Y is a maximum image height.