Projection optical system, projection-type image display device, and imaging device

A projection optical system comprising:

• a first optical system;
• and
• a second optical system, wherein
• the first optical system and the second optical system are disposed in order from a demagnification side toward a magnification side,
• an intermediate image is formed between a demagnification-side imaging surface and a magnification-side imaging surface,
• the second optical system is an optical element having a first transmission surface, a reflecting surface, and a second transmission surface in order from the demagnification side toward the magnification side,
• the first transmission surface and the reflecting surface are located at one side with respect to an optical axis,
• the second transmission surface is located at the other side with respect to the optical axis,
• the reflecting surface has a concavely curved surface shape,
• the second transmission surface has a convexly curved surface shape protruding toward the magnification side,
• the optical element has a first member and a second member different in refractive index from the first member, and
• a bonding surface between the first member and the second member has a curved surface shape.