2-dimensional image display device or illumination device for obtaining uniform illumination and suppressing speckle noise
A 2-dimensional beam scan unit reflects emission beams from a red laser light source, a green laser light source and a blue laser light source and scans in a 2-dimensional direction. Diffusion plates diffuse the respective light beams scanned in the 2-dimensional direction to introduce them to corresponding spatial light modulation elements. The respective spatial light modulation elements modulate the respective lights in accordance with video signals of the respective colors. A dichroic prism multiplexes the lights of the three colors after the modulation and introduces the multiplexed lights to a projection lens so that a color image is displayed on a screen. Since the 2-dimensional light emitted from the beam scan unit is diffused to illuminate the spatial light modulation element, it is possible to change the optical axis of the beam emerging from the light diffusion member for irradiating the spatial light modulation element moment by moment, thereby effectively suppressing speckle noise.
1. A 2-dimensional image display device, comprising:
at least one laser light source;
a beam scan unit for converting an emission beam from said laser light source into a 2-dimensional light while scanning the emission beam at least in a 1-dimensional direction;
a spatial light modulation element for spatially modulating the light scanned by said beam scan unit; and
a light diffusion member disposed between said beam scan unit and said spatial light modulation element for diffusing the 2-dimensional light emerging from said beam scan unit,
wherein:
said beam scan unit includes a 2-dimensional scanning portion for scanning the emission beam from said laser light source in a first direction and a second direction normal to the first direction; and
said 2-dimensional scanning portion cyclically scans the light beam incident on said light diffusion member at a frequency at which a ratio of a scan frequency in the first direction to a scan frequency in the second direction is a ratio of integers prime to each other.
2. A 2-dimensional image display device according to claim 1 , wherein said laser light source includes first, second and third laser light sources for generating red, green and blue colors, respectively.
3. A 2-dimensional image display device according to claim 2 , wherein said light diffusion member is one of a plurality of diffusion members and said spatial light modulation element is one of a plurality of spatial light modulation elements, said plurality of diffusion members and said plurality of spatial light modulation elements being in a one-to-one correspondence with said laser light sources.
4. A 2-dimensional image display device according to claim 3 , wherein emission beams from said first, second and third laser light sources are incident on said beam scan unit at mutually different angles.
5. A 2-dimensional image display device according to claim 1 , wherein said light diffusion member includes a pseudo random diffusion plate.
6. A 2-dimensional image display device according to claim 1 , wherein a light beam diameter S on the light diffusion member satisfies a relationship S>L·θ−d if θ, L and d denote the diffusion angle of said light diffusion member, a distance between said light diffusion member and said spatial light modulation element and the spacing between the adjacent light beams on said spatial light modulation element.
7. A 2-dimensional image display device according to claim 1 , wherein the emission beam from said laser light source is substantially condensed on said spatial light modulation element.
8. A 2-dimensional image display device according to claim 1 , further comprising a projection optical system for projecting the light modulated by said spatial light modulation element on a plane in a space.
9. An illumination light source, comprising:
at least one laser light source;
a beam scan unit for converting an emission beam from said laser light source into a 2-dimensional light, while scanning an emission beam from said laser light source at least in a 1-dimensional direction;
a spatial light modulation element for spatially modulating the light scanned by said beam scan unit; and
a light diffusion member disposed between said beam scan unit and said spatial light modulation element for diffusing the 2-dimensional light emerging from said beam scan unit,
wherein:
said beam scan unit includes a 2-dimensional scanning portion for scanning the emission beam from said laser light source in a first direction and a second direction normal to the first direction; and
said 2-dimensional scanning portion cyclically scans the light beam incident on said light diffusion member at a frequency at which a ratio of a scan frequency in the first direction to a scan frequency in the second direction is a ratio of integers prime to each other.
10. An illumination device, comprising an illumination light source according to claim 9 , wherein said laser light source includes an ultraviolet laser.