Projection type display device and back projection type display device using the same

• US 20050012870A1
• Filed: 05/10/2004
• Published: 01/20/2005
• Est. Priority Date: 07/18/2003
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yatsu, Masahiko, Hirata, Koji
• Granted Patent: US 7,499,111 B2
• Time in Patent Office: Days
• US Class Current: 349/8
• 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

Abstract

The system provides a projection-type video display device with high image quality and high reliability. The system improves color purity by cutting the yellow component from red and green, enhances the optical energy balance of the three colors by providing a reflection-type attenuation filter for reflecting light in the green optical path. The system also improves contrast characteristics by providing an optical phase difference compensator in the green optical path and increases durability of a video display element by arranging two optical parts having ultraviolet reflection coating in the blue optical path. Also an ultraviolet absorption filter for the incidence side of a blue liquid crystal panel is described.

Claims

1. A projection type display device comprising:

a white light source and a spectral unit for making spectral diffraction of a visible light flux radiated from the white light source into three primary colors of red, green and blue modulate light strength of the spectrally diffracted light flux per picture element according to an input image signal;

a light synthesizing unit for synthesizing the modulated light fluxes of respective colors from the red, green and blue display elements;

a projection lens for expanding and projecting the light synthesized by the light synthesizing unit on a screen;

a first reflector, arranged between at least either of the red display element or the green display element and the white light source, for selectively reflecting a light flux component of a predetermined wavelength region by combining with the spectral unit;

a second reflecting means, arranged between the green display element and the white light source, for reflecting a predetermined amount of green light component; and

an optical phase difference compensator arranged between the green display element and the second reflecting means.

2. The projection type display device according to claim 1, wherein the predetermined wavelength region includes a yellow light region of wavelength of 275-285 nm.

3. The projection type display device according to claim 1, wherein the white light source provides less optical energy of a red light region than of green and blue light regions.

4. The projection type display device according to claim 1, wherein the white light source is any one of an extra-high pressure mercury lamp, a xenon lamp or a metal halide lamp.

5. The projection type display device according to claim 1, wherein the second reflecting means has reflectance of 35% or more near a wavelength of 545 nm.

6. The projection type display device according to claim 1, wherein a plurality of reflection type UV-cut filters with half-value wavelength of approximately 430 nm are provided to a plurality of places of an optical part arranged between the white light source and the spectral means, and an absorption type UV-cut filter with half-value wavelength of approximately 430 nm is provided between the blue display element and the spectral means.

7. A back projection type display device comprising:

a white light source;

a spectral unit for making spectral diffraction of a visible light flux radiated from the white light source into three primary colors of red, green and blue;

a red display element, a green display element and a blue display element constituted so as to modulate light strength of the spectrally diffracted light flux per picture element according to an input image signal;

a light synthesizing unit for synthesizing the modulated light fluxes of respective colors from the red, green and blue display elements;

a screen;

an optical path turning-back mirror;

a projection lens for expanding and projecting the light synthesized by the light synthesizing unit on a screen via the optical path turning-back mirror;

a first reflecting means which is arranged between at least any one of the red display element and the green display element and the white light source, for selectively reflecting a light flux component of a predetermined wavelength region by combining with the spectral means;

a second reflecting means which is arranged between the green display element and the white light source, for reflecting a predetermined amount of green light component; and

an optical phase difference compensator arranged between the green display element and the second reflecting means.

8. The projection type display device according to claim 7, wherein the predetermined wavelength region includes a yellow light region of wavelength of 275-285 nm.

9. The projection type display device according to claim 7, wherein the white light source provides less optical energy of a red light region than of green and blue light regions.

10. The projection type display device according to claim 7, wherein the white light source is any one of an extra-high pressure mercury lamp, a xenon lamp or a metal halide lamp.

11. The projection type display device according to claim 7, wherein the second reflecting means has reflectance of 35% or more near a wavelength of 545 nm.

12. The projection type display device according to claim 7, wherein a plurality of reflection type UV-cut filters with half-value wavelength of approximately 430 nm are provided to a plurality of places of an optical part arranged between the white light source and the spectral means, and an absorption type UV-cut filter with half-value wavelength of approximately 430 nm is provided between the blue display element and the spectral means.