Zoom lens and image projection apparatus including the same

A zoom lens, comprising:

• a plurality of lens groups including a first lens group arranged on the foremost side, having negative optical power,
• wherein zooming is performed by moving at least one of the plurality of lens groups along a direction parallel to an optical axis of the zoom lens,
• wherein a rearmost lens group of the plurality of lens groups is fixed during the zooming,
• wherein a first lens arranged on the foremost side, of the first lens group has negative refractive power, and
• wherein, when an Abbe constant and a partial dispersion of a material configuring the first lens are respectively represented by νdn and θg,Fn;
• a focal distance of the first lens group is represented by f1;
• and an air-equivalent back focus upon focusing on an infinity object is represented by bf, the following conditions are satisfied:
• νdn<32,
• 0.008<θg,Fn−(0.644−0.00168×νdn)<0.040, and
• |f1/bf|<0.9.

A zoom lens, comprising:

• five or six lens groups including a first lens group arranged on the foremost side and having negative refractive power,
• wherein, upon zooming, the first lens group and a rearmost lens group are fixed and a plurality of the lens groups is movable,
• wherein negative and positive lenses Ln and Lp are respectively arranged on the foremost side and closest to an image, and
• wherein, when an Abbe constant and a partial dispersion of a material configuring the negative lens Ln are respectively represented by νdn and θg,Fn and an Abbe constant and a partial dispersion of a material configuring the positive lens Lp are respectively represented by νdp and θg,Fp, and when a focal distance of the first lens group is defined f1 and an air-equivalent back focus is represented by bf, the following conditions are satisfied:
• νdn<32,
• 0.008<θg,Fn−(0.644−0.00168×νdn)<0.040,
• |f1/bf|<0.9,
• νdp>63, and
• −0.005<θg,Fp−(0.644−0.00168×νdp)<0.045.