Imaging optical system, projection display device, and imaging apparatus

An imaging optical system consisting of, in order from a magnification side:

• a first imaging optical system that forms an intermediate image on a position conjugate to a magnification side imaging surface;
• and
• a second imaging optical system that re-forms the intermediate image on a reduction side imaging surface,
• wherein in a case where a group from which an adjacent group is separated by a distance variable in a direction of an optical axis during zooming is set as one lens group, the second imaging optical system consists of a plurality of lens groups including at least two movable lens groups which move during zooming,
• wherein assuming that
• a focal length of the first imaging optical system at a wide-angle end is f1w,
• a focal length of the whole system at the wide-angle end is fw,
• a focal length of the first imaging optical system at a telephoto end is f1t,
• a focal length of the whole system at the telephoto end is ft, and
• an effective image circle radius on a reduction side is Ymax,
• Conditional Expression (1) is satisfied.
• 1.15<(f1w/|fw|−f1t/|ft|)×Ymax/|fw|<5 (1)