Projection system and projector with first optical system and second optical system

A projection system comprising:

• a first optical system having positive power;
• and
• a second optical system disposed on a reduction side of the first optical system,
• wherein an intermediate image conjugate with an enlargement-side conjugate plane and a reduction-side conjugate plane of the projection system is formed between the first optical system and the second optical system,
• the second optical system includes
• a first lens group disposed on the enlargement side of a first intersection position where a chief ray of an off-axis beam having a maximum angle of view intersects with an optical axis of the projection system in the second optical system,
• a second lens group disposed on the reduction side of the first intersection position and having negative power, and
• a third lens group disposed on the reduction side of the second lens group and having positive power,
• the second lens group includes a first lens having positive power, a second lens disposed on the reduction side of the first lens and having positive power, and a third lens disposed on the reduction side of the second lens and having negative power,
• the third lens group includes two lenses each having positive power, and
• a conditional expression (2) below is satisfied,
• |fs1/f0|>10 (2)
• where fs1 is a focal length of the first lens, and f0 is a focal length of the entire projection system.

A projection system comprising:

• a first optical system having positive power;
• and
• a second optical system disposed on a reduction side of the first optical system,
• wherein an intermediate image conjugate with an enlargement-side conjugate plane and a reduction-side conjugate plane of the projection system is formed between the first optical system and the second optical system,
• the second optical system includes
• a first lens group disposed on the enlargement side of a first intersection position where a chief ray of an off-axis beam having a maximum angle of view intersects with an optical axis of the projection system in the second optical system,
• a second lens group disposed on the reduction side of the first intersection position and having negative power, and
• a third lens group disposed on the reduction side of the second lens group and having positive power,
• the second lens group includes a first lens having positive power, a second lens disposed on the reduction side of the first lens and having positive power, and a third lens disposed on the reduction side of the second lens and having negative power,
• the third lens group includes two lenses each having positive power,
• the first optical system includes a sixth lens disposed on the enlargement side of a second intersection position where the chief ray of the off-axis beam having the maximum angle of view intersects with the optical axis in the first optical system, the sixth lens being adjacent to the second intersection position, and
• a conditional expression (3) below is satisfied,
• |Ra2/Ra1|>9 (3)
• where Ra1 is an enlargement-side radius of curvature of the sixth lens, and Ra2 is a reduction-side radius of curvature of the sixth lens.