Projection system and projector

1. A projection system comprising:

a first optical system;

a second optical system including a first optical element and a second optical element and disposed on an enlargement side of the first optical system; and

a placement mechanism configured to selectively place one of the first and second optical elements on a first optical axis of the first optical system,

wherein the first optical element has a first light incident surface, a first reflection surface disposed on the enlargement side of the first light incident surface, and a first light exiting surface disposed on the enlargement side of the first reflection surface, and

the second optical element has a second light incident surface, a second reflection surface disposed on the enlargement side of the second light incident surface, and a second light exiting surface disposed on the enlargement side of the second reflection surface.

2. The projection system according to claim 1 ,

wherein a first projection angle in a first arrangement in which the first optical element is placed to the second optical system differs a second projection angle in a second arrangement in which the second optical element is placed to the second optical system.

3. The projection system according to claim 1 ,

wherein the second optical element has a third reflection surface on an optical path of the second optical element between the second reflection surface and the second light exiting surface.

4. The projection system according to claim 3 ,

wherein a first projection direction of a light flux projected via the first light exiting surface in a first arrangement in which the first optical element is placed to the second optical system differs from a second projection direction of a light flux projected via the second light exiting surface in a second arrangement in which the second optical element is placed to the second optical system.

5. The projection system according to claim 4 ,

wherein the second projection direction is opposite the first projection direction in a direction along the first optical axis of the first optical system.

6. The projection system according to claim 1 ,

wherein the first optical system is commonly used both in a first arrangement in which the first optical element is placed to the second optical system and a second arrangement in which the second optical element is placed to the second optical system.

7. The projection system according to claim 1 ,

wherein the placement mechanism sets an axial inter-surface distance between the first optical system and the first optical element to be a first distance in a first arrangement in which the first optical element is placed to the second optical system, and an axial inter-surface distance between the first optical system and the second optical element to be a second distance different from the first distance in a second arrangement in which the second optical element is placed to the second optical system.

8. The projection system according to claim 1 ,

wherein the first and second reflection surfaces have different shapes,

the first and second light exiting surfaces have different shapes, and

the first and second light incident surfaces have different shapes.

9. The projection system according to claim 1 ,

wherein the first optical system includes a first lens disposed in a position closest to the enlargement side in the first optical system and a second lens disposed on a reduction side of the first les, and

a distance between the first lens and the second lens in a first arrangement in which the first optical element is placed to the second optical system differs from the distance in a second arrangement in which the second optical element is placed to the second optical system.

10. The projection system according to claim 1 ,

Wherein at least one of the first and second reflection surfaces has a concave shape.

11. The projection system according to claim 1 ,

Wherein at least one of the first and second light exiting surfaces has a convex shape protruding toward the enlargement side.

12. The projection system according to claim 1 ,

wherein the first and second light incident surfaces has a convex shape protruding toward a reduction side.

13. The projection system according to claim 1 ,

wherein the first light incident surface and the first reflection surface are located on one side of an optical axis of the first reflection surface, and

the first light exiting surface is located on other side of the optical axis of the first reflection surface.

14. The projection system according to claim 1 ,

wherein the second light incident surface and the second reflection surface are located on one side of an optical axis of the second reflection surface, and

the second light exiting surface is located on other side of the optical axis of the second reflection surface.

15. The projection system according to claim 1 ,

Wherein at least one of the first reflection surface, the second reflection surface, the first light exiting surface, the second light exiting surface, the first light incident surface, and the second light incident surface is an aspheric surface.

16. The projection system according to claim 1 ,

wherein the first light incident surface, the first reflection surface, and the first light exiting surface each have a shape rotationally symmetric around an optical axis of the first reflection surface.

17. The projection system according to claim 1 ,

wherein the second light incident surface, the second reflection surface, and the second light exiting surface each have a shape rotationally symmetric around an optical axis of the second reflection surface.

18. The projection system according to claim 1 ,

wherein a direction along an axis perpendicular to an optical axis of the first reflection surface is a first axial direction,

a first pupil that connects an upper intersection to a lower intersection inclines with respect to an imaginary vertical line perpendicular to the optical axis of the first reflection surface in a plane containing the first optical axis of the first optical system and the optical axis of the first reflection surface,

the upper intersection is an intersection where an upper peripheral light ray of an upper end light flux passing through an upper end of an effective light ray range of the first light exiting surface that is an upper end in the first axial direction and an upper peripheral light ray of a lower end light flux passing through a lower end of the effective light ray range that is a lower end in the first axial direction intersect each other in the plane, and

the lower intersection is an intersection where a lower peripheral light ray of the upper end light flux and a lower peripheral light ray of the lower end light flux intersect each other in the plane.

19. The projection system according to claim 1 ,

wherein a direction along an axis perpendicular to an optical axis of the second reflection surface is a first axial direction,

a second pupil that connects an upper intersection to a lower intersection inclines with respect to an imaginary vertical line perpendicular to the optical axis of the second reflection surface in a plane containing the first optical axis of the first optical system and the optical axis of the second reflection surface,

the upper intersection is an intersection where an upper peripheral light ray of an upper end light flux passing through an upper end of an effective light ray range of the second light exiting surface that is an upper end in the first axial direction and an upper peripheral light ray of a lower end light flux passing through a lower end of the effective light ray range that is a lower end in the first axial direction intersect each other in the plane, and

the lower intersection is an intersection where a lower peripheral light ray of the upper end light flux and a lower peripheral light ray of the lower end light flux intersect each other in the plane.

20. The projection system according to claim 1 ,

wherein an intermediate image is formed on a reduction side of the first reflection surface in a first arrangement in which the first optical element is placed to the second optical system, and

an intermediate image is formed on the reduction side of the second reflection surface in a second arrangement in which the second optical element is placed to the second optical system.

21. A projector comprising:

the projection system according to claim 1 ; and

an image formation section that forms a projection image in a reduction-side image formation plane of the projection system.