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

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.

What is claimed is: 
     
       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. 
     
     
       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. 
     
     
       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. 
     
     
       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.   
     
     
       24. An image projection apparatus, comprising:
 a liquid crystal panel or a digital micromirror device (DMD);   a plurality of lenses; and   a concave mirror;   wherein a picture formed in the liquid crystal panel or the DMD exits from the plurality of lenses to be incident on and reflected from the concave mirror to be magnified and projected,   an intermediate image is formed between the liquid crystal panel or the DMD and the concave mirror,   the intermediate image is tilted and curved with respect to a principal ray of a light beam emitted from a center of the liquid crystal panel or the DMD,   the liquid crystal panel or the DMD is disposed shifted in a plane perpendicular to an optical axis of the plurality of lenses,   an optical path length between the concave mirror and a projected image of the picture increases as an angle between the light beam incident on the concave mirror and the light beam reflected from the concave mirror increases,   the light beam from concave mirror converges, and   the light beam reflected from the concave mirror crosses the optical axis of the plurality of lenses.   
     
     
       25. The image projection apparatus according to claim 24, wherein the plurality of lenses and the concave mirror are shifted in a same direction relative to the liquid crystal panel or the DMD. 
     
     
       26. The image projection apparatus according to claim 25, wherein a perpendicular of a surface of the liquid crystal panel or the DMD is parallel to the optical axis of the plurality of lenses.