Projection optical system, magnification projection optical system, magnification projection apparatus, and image projection apparatus

• US 7,922,341 B2
• Filed: 10/20/2009
• Issued: 04/12/2011
• Est. Priority Date: 02/06/2003
• Status: Expired

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Sakuma, Nobuo, Takaura, Atsushi, Fujita, Kazuhiro
• Primary Examiner(s): Dowling; William C
• Application Number:
  US12/582,363
• Publication Number:
  US 20100039625A1
• Time in Patent Office: 539 Days
• Field of Search: 353/99
• US Class Current: 353/99
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV
• CPC Class Codes: G02B 17/0816 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 17/0848 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
• CPC Class Codes: G03B 21/28 Reflectors in projection beam in illumination beam G03B21/2066

Abstract

In a projection optical system for use in an image projection apparatus illuminating an image display panel forming an image in accordance with a modulating signal with illumination light from a light source, the projection optical system includes first and second optical systems arranged along an optical path defining an upstream-downstream direction in the order described from upstream to downstream on the downstream side of the image display panel. The first optical system includes at least one dioptric system and has positive power. The second optical system includes at least one reflecting surface having power and has positive power. The image formed by the image display panel is formed as an intermediate image in the optical path, and the intermediate image is magnified and projected.

Claims

1. A projection optical system for use in an image projection apparatus projecting an image of an object and forming a final image on a plane, the projection optical system comprising:

first and second optical systems arranged so that the first optical system is closer to the object than is the second optical system;

wherein the first optical system includes at least one dioptric system and has positive power,

the second optical system includes at least one reflecting surface having positive power,

the image of the object is formed as an intermediate image in an optical path of the first and second optical systems, and the intermediate image is magnified and projected, and

the second optical system is configured so that an angle of incidence to a projection surface on the plane is greater at a position farthest from the object than at a position closest to the object on the final image.

2. The projection optical system as claimed in claim 1, wherein a difference between the angle of incidence at the position of the final image farthest from the object and the angle of incidence at the position of the final image closest to the object is 53 degrees or more.

3. The projection optical system as claimed in claim 1, wherein the first optical system is configured to distort the intermediate image so as to offset a possible trapezoidal distortion of the final image.

4. The projection optical system as claimed in claim 1, wherein the first optical system is configured to form the intermediate image with a distortion inverse to a possible trapezoidal distortion of the final image.

5. The projection optical system as claimed in claim 1, wherein the first optical system is configured to form the intermediate image distorted inversely relative to the final image narrowed downward and distorted.

6. The projection optical system as claimed in claim 2, wherein the first optical system is configured to distort the intermediate image so as to offset a possible trapezoidal distortion of the final image.

7. The projection optical system as claimed in claim 2, wherein the first optical system is configured to form the intermediate image with a distortion inverse to a possible trapezoidal distortion of the final image.

8. The projection optical system as claimed in claim 2, wherein the first optical system is configured to form the intermediate image distorted inversely relative to the final image narrowed downward and distorted.

9. The projection optical system as claimed in claim 1, wherein the first optical system is configured to tilt the intermediate image with respect to a principal ray of a light beam emitted from a center of a surface of the object surface.

10. A projection optical system for use in an image projection apparatus projecting an image of an object and forming a final image on a plane, the projection optical system comprising:

first and second optical systems arranged so that the first optical system is closer to the object than the second optical system;

wherein the first optical system includes at least one dioptric system and has positive power,

the second optical system includes at least one reflecting surface having positive power,

the image of the object is formed as an intermediate image in an optical path of the first and second optical systems, and the intermediate image is magnified and projected, and

the second optical system is configured so that an optical path from the reflecting surface having the positive power to the final image is longer at a position thereof farthest from the object than at a position thereof closest to the object.

11. The projection optical system as claimed in claim 10, wherein a difference between the optical path from the reflecting surface having the positive power to the position of the final image farthest from the object and the optical path from the reflecting surface having the positive power to the position of the final image closest to the object is 663 mm or more.

12. The projection optical system as claimed in claim 10, wherein the first optical system is configured to distort the intermediate image so as to offset a possible trapezoidal distortion of the final image.

14. The projection optical system as claimed in claim 10, wherein the first optical system is configured to form the intermediate image distorted inversely relative to the final image narrowed downward and distorted.

15. The projection optical system as claimed in claim 11, wherein the first optical system is configured to distort the intermediate image so as to offset a possible trapezoidal distortion of the final image.

16. The projection optical system as claimed in claim 11, wherein the first optical system is configured to form the intermediate image with a distortion inverse to a possible trapezoidal distortion of the final image.

17. The projection optical system as claimed in claim 11, wherein the first optical system is configured to form the intermediate image distorted inversely relative to the final image narrowed downward and distorted.

13. The projection optical system as claimed 10, wherein the first optical system is configured to form the intermediate image with a distortion inverse to a possible trapezoidal distortion of the final image.

18. A projection optical system for use in an image projection apparatus projecting an image of an object and forming a final image on a plane, the projection optical system comprising:

first and second optical systems arranged so that the first optical system is closer to the object than the second optical system;

wherein the first optical system includes at least one dioptric system and has positive power,

the second optical system includes at least one reflecting surface having positive power,

the image of the object is formed as an intermediate image in an optical path of the first and second optical systems, and the intermediate image is magnified and projected, and

the first optical system is configured to form the intermediate image with a distortion inverse to a possible trapezoidal distortion of the final image.

19. The projection optical system as claimed in claim 18, wherein the first optical system is configured to distort the intermediate image so as to offset the possible trapezoidal distortion of the final image.

20. The projection optical system as claimed in claim 18, wherein the first optical system is configured to form the intermediate image distorted inversely relative to the final image narrowed downward and distorted.

21. An image projection apparatus configured to project an image of an object and form a final image on a plane, the image projection apparatus comprising:

an image forming part configured to be illuminated with illumination light and to form the image of the object;

first and second optical systems arranged so that the first optical system is closer to the image forming part than is the second optical system;

wherein the first optical system includes at least one dioptric system and has positive power,

the second optical system includes at least one reflecting surface having positive power,

the image of the object is formed as an intermediate image in an optical path of the first and second optical systems, and the intermediate image is magnified and projected, and

the second optical system is configured so that an angle of incidence to a projection surface on the plane is greater at a position farthest from the object than at a position closest to the object on the final image.

22. An image projection apparatus configured to project an image of an object and form a final image on a plane, the image projection apparatus comprising:

an image forming part configured to be illuminated with illumination light and to form the image of the object;

first and second optical systems arranged so that the first optical system is closer to the image forming part than is the second optical system,

wherein the first optical system includes at least one dioptric system and has positive power,

the second optical system includes at least one reflecting surface having positive power,

the image of the object is formed as an intermediate image in an optical path of the first and second optical systems, and the intermediate image is magnified and projected, and

the second optical system is configured so that an optical path from the reflecting surface having the positive power to the final image is longer at a position thereof farthest from the object than at a position thereof closest to the object.

23. An image projection apparatus configured to project an image of an object and form a final image on a plane, the image projection apparatus comprising:

an image forming part configured to be illuminated with illumination light and to form the image of the object;

first and second optical systems arranged so that the first optical system is closer to the image forming part than is the second optical system,

wherein the first optical system includes at least one dioptric system and has positive power,

the second optical system includes at least one reflecting surface having positive power,

the image of the object is formed as an intermediate image in an optical path of the first and second optical systems, and the intermediate image is magnified and projected, and

the first optical system is configured to form the intermediate image with a distortion inverse to a possible trapezoidal distortion of the final image.