Projection Optical System and Projector

A projection optical system capable of performing magnification projection of an image displayed on an image display surface, with a 40° half angle of view, or more, the projection optical system comprising, in an order from a magnification side:

• a first optical system;
• and
• a second optical system,
• wherein the second optical system forms an intermediate image of the image,
• the first optical system performs magnification projection of the intermediate image, and
• the following conditional expressions (1) and (2) are satisfied:
• 1<Ff/|Fw|<2 (1)
• 0.4<Lf/Lw<0.6 (2),
• where,
• Ff:
• a focal length of the first optical system,
• Fw:
• a focal length of an entire system (focal length of the entire system at a maximum angle of view in a case where the projection optical system is a zoom lens),
• Lf:
• a distance on optical axis, from a most-magnification-side surface vertex to the intermediate image, in the first optical system,
• Lw:
• an entire length of a lens (entire length of the lens, at the maximum angle of view in a case where the projection optical system is a zoom lens).