Illumination optical system with reflecting light valve

• US 6,561,656 B1
• Filed: 02/07/2002
• Issued: 05/13/2003
• Est. Priority Date: 09/17/2001
• Status: Expired due to Term

• Current Assignee: Rakuten Group, Inc.
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Kojima, Kuniko, Okamori, Shinji
• Primary Examiner(s): DOWLING, WILLIAM C
• Application Number:
  US10/067,280
• Time in Patent Office: 460 Days
• Field of Search: 353/20, 353/38, 353/31, 353/34, 353/37, 353/102, 353/101, 353/98, 349/5, 349/8, 349/9, 348/742, 348/743, 348/771
• US Class Current: 353/98
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]
• CPC Class Codes: H04N 9/3114 by using a sequential colour filter producing one colour at a time
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

An illumination optical system comprises a light source lamp (1), a light mixing element (3) for mixing light emitted from the light source lamp (1), a DMD element (5) having a plurality of pixels, a transmission optical system (4) for bringing a light-exit surface (3a) of the light mixing element (3) into optical conjugation with a to-be-illuminated surface (5S) of the DMD element (5), and a field lens (6) located in front of the DMD element (5). The focal length of the field lens (6) can be changed so that an illuminance distribution that varies according to the application of the illumination optical system can be achieved on the to-be-illuminated surface (5S).

Claims

1. An illumination optical system comprising:

a light source;

a light mixing element mixing light emitted from said light source;

a reflecting light valve having a plurality of pixels;

a transmission optical system located between said light mixing element and said reflecting light valve and bringing a light exit surface of said light mixing element into optical conjugation with a to-be-illuminated surface of said reflecting light valve; and

a field lens located between said transmission optical system and said reflecting light valve,

wherein a focal length of said field lens is determined so that an illuminance distribution which varies according to the application of said illumination optical system can be achieved on said to-be-illuminated surface.

2. The illumination optical system according to claim 1, wherein

said focal length of said field lens is determined so that an illumination margin takes on a value in the neighborhood of 1.0, and

a diagonal dimension of a to-be-illuminated area on said to-be-illuminated surface is equivalent to the product of a diagonal dimension of said to-be-illuminated surface and said illumination margin.

3. The illumination optical system according to claim 1, wherein

said focal length of said field lens is determined by obtaining at least one of a radius of curvature of said field lens and the type of a glass material forming said field lens on the basis of said illuminance distribution which varies according to said application of said illumination optical system.

4. The illumination optical system according to claim 1, wherein

said light exit surface of said light mixing element and said to-be-illuminated surface of said reflecting light valve are generally similar in shape.

5. The illumination optical system according to claim 1, wherein

said plurality of pixels in said reflecting light valve each are configured of a micromirror having a variable angle of inclination.

6. The illumination optical system according to claim 1, wherein

said light mixing element is formed in the shape of a hollow rod, using its inner surface as a reflecting surface.

7. The illumination optical system according to claim 1, further comprising:

a rotary color filter located either in front of or behind said light mixing element to pass said light emitted from said light source.

8. The illumination optical system according to claim 1, wherein

said field lens is a planoconvex lens having a plane surface on the side of said to-be-illuminated surface of said reflecting light valve.

9. The illumination optical system according to claim 1, wherein

said field lens has at least one aspherical surface.

10. The illumination optical system according to claim 1, wherein

said field lens is a Fresnel lens.

11. A projection display comprising:

the illumination optical system of claim 1;

a screen; and

a projection lens system located between said reflecting light valve and said screen.