Projection optical system

• US 7,239,452 B2
• Filed: 04/07/2005
• Issued: 07/03/2007
• Est. Priority Date: 04/14/2004
• Status: Active Grant

• Current Assignee: Konica Minolta OPTO Incorporated (Konica Minolta Inc.)
• Original Assignee: Konica Minolta OPTO Incorporated (Konica Minolta Inc.)
• Inventors: Kuwa, Tomiei
• Primary Examiner(s): Mack; Ricky
• Assistant Examiner(s): CHOI, WILLIAM C
• Application Number:
  US11/101,344
• Publication Number:
  US 20060176579A1
• Time in Patent Office: 817 Days
• Field of Search: 359649-651, 359726-731, 353/78, 353/99
• US Class Current: 359/649
• CPC Class Codes: G02B 13/08 Anamorphotic objectives
• CPC Class Codes: G02B 17/0832 off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements
• CPC Class Codes: G02B 17/0852 having a field corrector only

Abstract

A projection optical system for performing enlargement projection from a primary image surface on the reduction side to a secondary image surface on the enlargement side has, from the primary image surface side, a lens optical system including two or more lens elements sharing a common rotation-symmetry axis and each having an optical power, a first reflective optical element having an optical power, and a second reflective optical element having a negative optical power. The projection optical system is non-telecentric toward the reduction side, and a prescribed condition is.

Claims

1. A projection optical system for performing enlargement projection from a primary image surface on a reduction side to a secondary image surface on a enlargement side, the projection optical system comprising, from a primary image surface side:

a lens optical system including two or more lens elements sharing a common rotation-symmetry axis and each having an optical power;

a first reflective optical element having an optical power; and

a second reflective optical element having a negative optical power,

wherein the projection optical system is non-telecentric toward the reduction side, and the following condition is fulfilled;

30°

≦

θ

≦

70°

where

θ

represents an angle of incidence at which a central principal ray is incident on the secondary image surface.

2. The projection optical system of claim 1, wherein the first reflective optical element has a positive optical power.

3. The projection optical system of claim 2, wherein the first reflective optical element has a reflective surface having a rotation-symmetric shape.

4. The projection optical system of claim 3, wherein the reflective surface of the first reflective optical element is a rotation-symmetric aspherical surface.

5. The projection optical system of claim 3, wherein the first reflective optical element has an optical power eccentric with respect to a normal to the primary image surface.

6. The projection optical system of claim 5, wherein a rotation symmetry axis of the reflective surface of the first reflective optical element is located outside an area over which a projected light beam strikes the first reflective optical element.

7. The projection optical system of claim 1, wherein the second reflective optical element has a reflective surface having a rotation-symmetric shape.

8. The projection optical system of claim 7, wherein the reflective surface of the second reflective optical element is a rotation-symmetric aspherical surface.

9. The projection optical system of claim 7, wherein the second reflective optical element has an optical power eccentric with respect to a normal to the primary image surface.

10. The projection optical system of claim 9, wherein a rotation symmetry axis of the reflective surface of the second reflective optical element is located outside an area over which a projected light beam strikes the second reflective optical element.

11. The projection optical system of claim 1, wherein the lens optical system includes a non-rotation-symmetric lens element, the non-rotation-symmetric lens element having a non-rotation-symmetric surface that has at most one plane of symmetry.

12. The projection optical system of claim 1, wherein an optical axis of the lens optical system is inclined relative to a normal to the primary image surface.

13. The projection optical system of claim 1,

wherein a most primary-image-surface-side lens element along an optical path of the lens optical system has as an optical surface a rotation-symmetric aspherical surface, and

wherein, let a vertex of the aspherical surface be Ao, let a vector from the vertex Ao to a point at which a rotation-symmetry axis of the aspherical surface intersects another surface of the most primary-image-surface-side lens element be Avx, and let a vector perpendicular to the vector Avx be Avy, and moreover, in a two-dimensional coordinate system formed by the vectors Avx and Avy with an origin at the vertex Ao, let a value in a direction of the vector Avx be represented by Ax, let a value in a direction of the vector Avy be represented by Ay, and let a shape of the aspherical surface be defined as Ax=f(Ay), then a second derivative function f(Ay)″

of f(Ay) has at least either a maximum or a minimum within a range fulfilling the following condition;

0<

Ay<

Rmax

where

Rmax represents an effective optical path radius of the aspherical surface.

14. The projection optical system of claim 1, wherein the following condition is fulfilled:

0<

(RV/V1)×

(T/V2)<

5

where

RV represents a dimension of an effective optical path on the second reflective optical element as measured in a direction of shorter sides of the secondary image surface;

V1 represents a dimension of the primary image surface in a direction of shorter sides thereof;

T represents, in a case where the projection optical system is used in a rear-projection image display apparatus, a thickness of the apparatus in a direction of a normal to the secondary image surface; and

V2 represents a dimension of the secondary image surface in the direction of the shorter sides thereof.

15. The projection optical system of claim 1, further comprising:

an aperture stop,

wherein the lens optical system includes a positive lens element and a negative lens element, and

wherein the positive and negative lens elements are disposed near the aperture stop.

16. The projection optical system of claim 15, wherein the positive and negative lens elements are cemented together.

17. The projection optical system of claim 1, wherein a pupil of the projection optical system is located between the primary image surface and a most secondary-image-surface-side lens element of the lens optical system.

18. The projection optical system of claim 1, further comprising an aperture stop,

wherein the aperture stop is disposed near a most primary-image-surface-side lens element of the lens optical system.

19. The projection optical system of claim 1, wherein, with respect to an angle θ

1 between a normal to the primary image surface and an optical axis of the lens optical system, the following condition is fulfilled;

0.5°

≦

|θ

1|≦

10°

.

20. The projection optical system of claim 1, wherein, with respect to an angle θ

2 between a normal to the primary image surface and a normal to the secondary image surface, the following condition is fulfilled;

15°

≦

|θ

2|≦

60°

.

21. The projection optical system of claim 1, wherein all light rays from the primary image surface are obliquely incident on the secondary image surface.

22. A projection optical system for performing enlargement projection from a primary image surface on a reduction side to a secondary image surface on a enlargement side, the projection optical system comprising, from a primary image surface side:

a lens optical system including two or more lens elements sharing a common rotation-symmetry axis and each having an optical power;

a first reflective optical element having an optical power;

a second reflective optical element having a negative optical power, and

a flat reflection mirror disposed parallel to the secondary image surface so as to bend an optical path,

wherein the projection optical system is non-telecentric toward the reduction side, and the following condition is fulfilled;

30°

≦

θ

≦

70°

where

θ

represents an angle of incidence at which a central principal ray is incident on the secondary image surface.