Projection optical system and projection type display device

A projection optical system that forms an intermediate image at a position conjugate to an image displayed by an image display element provided on a reduction side conjugate plane, and projects the intermediate image onto a magnification side conjugate plane as a magnified image, the projection optical system comprising:

• a first optical system constituted by a first plurality of lenses that forms the image displayed by the image display elements as an intermediate image;
• a second optical system constituted by a second plurality of lenses that focuses the intermediate image on the magnification side conjugate plane;
• and
• two reflective surfaces positioned to bend an optical path by 90 degrees;
• wherein:
• at least a first lens of the first plurality of lenses is arranged at a position of a reduction side from the two reflective surfaces, and at least a second lens of the second plurality of lenses is arranged at a position of a magnification side from the two reflective surfaces;
• in which Conditional Formulae (1) and (3) below being satisfied:
• 10.0<TL1/|f|<50.0 (1)
• 8.0<D12/|f|<30.0 (3)
• wherein TL1 is the distance along the optical axis from the surface most toward the reduction side to the surface most toward the magnification side within the first optical system, D12 is the distance along the optical axis between the first optical system and the second optical system, and f is the focal length of the entire projection optical system.