US Patent 11774731 Optical system, projector, and imaging apparatus

An optical system forms an intermediate image between a reduction-side conjugate plane and a enlargement-side conjugate plane. The optical system includes a first optical system and a second optical system including a lens and disposed on the enlargement side of the first optical system. 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. At least one of the reflection surface and the second transmission surface is a free-form surface.