Projection zoom lens and projection-type display apparatus

A projection zoom lens comprising, in order from a magnification side:

• a first lens group having negative refractive power adapted to perform focusing with being fixed during power-varying;
• a second lens group having positive refractive power adapted to move during power-varying;
• a third lens group having negative refractive power adapted to move during power-varying;
• a fourth lens group having positive refractive power adapted to move during power-varying;
• a fifth lens group having positive refractive power adapted to move during power-varying;
• and
• a sixth lens group having positive refractive power adapted to be fixed during power-varying and to include a first stop nearest to the magnification side,
• wherein a numerical aperture is set constant over the whole region of power-varying,
• each lens included in the first to sixth groups is a single lens,
• a reduction side is made telecentric, and
• the following conditional expression (1) is satisfied:
• 2.5<Bf/f (1)
• where Bf denotes an air-converted back focal length of the entire system, and
• f denotes a focal length at a wide-angle end of the entire system.