Color separating optical system, image display optical system, and projection image display apparatus

• US 20030067586A1
• Filed: 09/04/2002
• Published: 04/10/2003
• Est. Priority Date: 09/04/2001
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Atsushi Okuyama, Masayuki Abe, Tatsuo Chigira
• Inventors: Abe, Masayuki, Okuyama, Atsushi, Chigira, Tatsuo
• Granted Patent: US 7,156,520 B2
• Time in Patent Office: Days
• US Class Current: 353/20
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3117 by using a sequential colour filter producing two or more colours simultaneously, e.g. by creating scrolling colour bands
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

There is provided a color separating-combining optical system having:

a separating optical system which separates illumination light into a first color spectrum, and second and third color spectrums;

a first polarization separating optical system with a first polarization separating surface, which guides the first color spectrum from the separating optical system to a first image display element and which analyzes light from the first image display element;

a second polarization separating optical system with a second polarization separating surface, which separates the second and third color spectrums from the separating optical system from each other, which guides the second color spectrum to a second image display element, which guides the third color spectrum to a third image display element, and which analyzes light from the second image display element and light from the third image display element; and

a combining optical system which combines light from the first polarization separating optical system with light from the second polarization separating optical system;

wherein a polarization separation characteristic of the first polarization separating surface of the first polarization separating optical system is different from a polarization separation characteristic of the second polarization separating surface of the second polarization separating optical system.

Claims

1. A color separating-combining optical system comprising:

a separating optical system which separates illumination light into a first color spectrum, and second and third color spectrums;

a first polarization separating optical system with a first polarization separating surface, which guides the first color spectrum from said separating optical system to a first image display element and which analyzes light from said first image display element;

a second polarization separating optical system with a second polarization separating surface, which separates the second and third color spectrums from said separating optical system from each other, which guides the second color spectrum to a second image display element, which guides the third color spectrum to a third image display element, and which analyzes light from said second image display element and light from said third image display element; and

a combining optical system which combines light from said first polarization separating optical system with light from said second polarization separating optical system;

wherein a polarization separation characteristic of said first polarization separating surface of said first polarization separating optical system is different from a polarization separation characteristic of said second polarization separating surface of said second polarization separating optical system.

2. An optical system according to claim 1, wherein, when a degree of linear polarization is defined as a rate of a component in a principal polarized direction included in each of the first, second, and third color spectrums,

the polarization separation characteristic of said first polarization separating surface of said first polarization separating optical system is made different from the polarization separation characteristic of said second polarization separating surface of said second polarization separating optical system so that a degree of linear polarization of the first color spectrum incident from said first polarization separating surface to said first image display element is higher than degrees of linear polarization of the second and third color spectrums incident from said second polarization separating surface to said second and third image display elements.

3. An optical system according to claim 1, wherein, when a degree of linear polarization is defined as a rate of a component in a principal polarized direction included in each of the first, second, and third color spectrums,

said second polarization separating surface has such a polarization separation characteristic that degrees of linear polarization of the second and third color spectrums reflected by the second polarization separating surface are substantially equal to degrees of linear polarization of the second and third color spectrums transmitted by said second polarization separating surface.

4. An optical system according to claim 1, wherein, when a degree of linear polarization is defined as a rate of a component in a principal polarized direction included in each of the first, second, and third color spectrums,

said first polarization separating surface has such a polarization separation characteristic that a degree of linear polarization of the first color spectrum incident from the first polarization separating surface to said first image display element is higher than a degree of linear polarization of the first color spectrum traveling from said first image display element via said first polarization separating surface toward said combining optical system.

5. An optical system according to claim 1, further comprising:

a polarizing plate placed between said first polarization separating surface and said combining optical system.

6. An optical system according to claim 1, wherein said image display elements are reflective image display elements.

7. An optical system according to claim 1, wherein said combining optical system is a third polarization separating optical system with a third polarization separating surface, which combines the first color spectrum from said first polarization separating surface with the second and third color spectrums from said second polarization separating surface by polarization separating action.

8. An optical system according to claim 7, further comprising:

an antireflection surface formed on a surface except for an entrance surface and an exit surface in at least one optical system out of said first polarization separating optical system, said second polarization separating optical system, and said third polarization separating optical system.

9. An optical system according to claim 1, wherein said first color spectrum is green light.

10. An image display optical system comprising:

the color separating-combining optical system as set forth in claim 1;

an illumination system which makes illumination light enter said color separating-combining optical system while being aligned in a polarized direction; and

a projection optical system which projects combined light exiting said color separating-combining optical system.

11. A projection image display apparatus comprising:

first, second, and third image display elements; and

the image display optical system as set forth in claim 10.

12. A projection image display apparatus according to claim 11, wherein said first, second, and third image display elements are reflective image display elements.

13. A color separating-combining optical system comprising:

a separating optical system which separates illumination light into a first color spectrum, and second and third color spectrums;

a first polarization separating optical system with a first polarization separating surface, which guides the first color spectrum from said separating optical system to a first image display element and which analyzes light from said first image display element;

a second polarization separating optical system with a second polarization separating surface, which separates the second and third color spectrums from said separating optical system from each other, which guides the second color spectrum to a second image display element, which guides the third color spectrum to a third image display element, and which analyzes light from said second image display element and light from said third image display element; and

a combining optical system which combines the first color spectrum from said first polarization separating surface with the second and third color spectrums from said second polarization separating surface;

wherein at least one surface except for an entrance surface and an exit surface in said first polarization separating optical system, is comprised of a light-absorbing surface.

14. An optical system according to claim 13, wherein said combining optical system is a third polarization separating optical system with a third polarization separating surface, which combines the first color spectrum from said first polarization separating surface with the second and third color spectrums from said second polarization separating surface by polarization separating action.

15. An optical system according to claim 14, wherein at least one surface except for an entrance surface and an exit surface in said third polarization separating optical system, is comprised of a light-absorbing surface.

16. An optical system according to claim 13, wherein a surface located in a direction of extension of an optical axis of incidence to said first polarization separating surface, out of surfaces except for an entrance surface and an exit surface in said first polarization separating optical system, is comprised of a light-absorbing surface.

17. An optical system according to claim 13, wherein a surface located in parallel with an optical axis, out of surfaces except for entrance surfaces and exit surfaces in said first and second polarization separating optical systems, is comprised of a light-absorbing surface.

18. An optical system according to claim 15, wherein a surface located in a direction of extension of an optical axis of incidence to said third polarization separating surface, out of surfaces except for an entrance surface and an exit surface in said third polarization separating optical system, is comprised of a light-absorbing surface.

19. An optical system according to claim 15, wherein a surface located in parallel with an optical axis, out of surfaces except for an entrance surface and an exit surface in said third polarization separating optical system, is comprised of a light-absorbing surface.

20. An optical system according to claim 13, wherein said light-absorbing surface is a surface obtained in such a way that a surface except for an entrance surface and an exit surface is changed into a rough surface with predetermined surface roughness and the rough surface is coated with a black light-absorbing paint.

21. An optical system according to claim 13, further comprising:

a heat radiating member thermally coupled to said light-absorbing surface.

22. An image display optical system comprising:

the color separating-combining optical system as set forth in claim 13;

an illumination system which makes illumination light enter said color separating-combining optical system while being aligned in a polarized direction; and

a projection optical system which projects combined light exiting said color separating-combining optical system.

23. A projection image display apparatus comprising:

first, second, and third image display elements; and

the image display optical system as set forth in claim 22.

24. A projection image display apparatus according to claim 23, wherein said first, second, and third image display elements are reflective image display elements.