Projection system and projector

A projection system for enlarging a projection image formed by an image formation device disposed in a reduction-side conjugate plane and projecting the enlarged image in an enlargement-side conjugate plane, the projection system comprising:

• a first optical system and a second optical system sequentially arranged from the reduction side toward the enlargement side,
• wherein the first optical system includes a diaphragm,
• the second optical system includes an optical element having a concave reflection surface and a first lens having negative power, the optical element and the first lens sequentially arranged from the reduction side toward the enlargement side,
• an intermediate image conjugate with the reduction-side conjugate plane and the enlargement-side conjugate plane is formed between the first optical system and the second optical system,
• a portion at the reduction side of the first optical system forms a telecentric portion, and
• the projection system satisfies all Conditional Expressions (1) and (2) below,
• TR≤0.3 (1)
• 35≤(OAL/imy)×(LL/imy)×TR×(1/NA)≤60 (2)
• where OAL represents an axial inter-surface spacing from the image formation device to the reflection surface, imy represents a first distance from an optical axis to a largest image height at the image formation device, LL represents a largest radius of the first lens, TR represents a throw ratio that is a quotient of division of a projection distance by a second distance from the optical axis to a largest image height of the enlarged image, and NA represents a numerical aperture of the image formation device.