Optical system, projector, and imaging apparatus

An optical system that forms an intermediate image between a reduction-side conjugate plane and an enlargement-side conjugate plane, the optical system comprising:

• a first optical system;
• and
• a second optical system including a lens and disposed on an enlargement side of the first optical system, wherein:
• the lens has a first transmission surface, a reflection surface disposed on the enlargement side of the first transmission surface, and a second transmission surface disposed on the enlargement side of the reflection surface,
• the intermediate image is formed inside the lens,
• at least one of the reflection surface and the second transmission surface is a free-form surface,
• the lens has a first surface facing a reduction side and a second surface having a convex shape and facing an opposite side to the first surface,
• the second surface is provided with a reflective coating layer that is the reflection surface, and
• the reflective coating layer has a concave shape to which a surface shape of the second surface is transferred.