Light Source Device, and Two-Dimensional Image Display Device

Abstract

There is provided a light source device which can miniaturize a two-dimensional image display device as small as possible. The light source device is provided with three coherent light sources ( 11 a ), ( 11 b ), and ( 11 c ) corresponding to red, blue, and green; prisms ( 12 a ) and ( 12 c ) for reflecting lights emitted from the coherent light sources ( 11 a ) and ( 11 c ); and a diffraction part ( 20 ) comprising a single volume hologram on which plural gratings are multiply-formed, which gratings diffract the light emitted from the coherent light source ( 11 b ), and the lights that are emitted from the coherent light sources ( 11 a ) and ( 11 c ) and reflected by the prisms ( 12 a ) and ( 12 b ) so that these lights propagate in the same optical path.

1 . A light source device comprising:
 at least two coherent light sources; and   a diffraction part for diffracting light which is emitted from at least one of the coherent light sources so that the respective lights emitted from the at least two coherent light sources propagate through the same optical path.   
     
     
         2 . A light source device as defined in  claim 1  wherein the optical propagation paths of the respective lights emitted from the at least two coherent light sources overlap each other on the diffraction part. 
     
     
         3 . A light source device as defined in  claim 1  wherein the center axes of the optical propagation paths of the respective lights emitted from the at least two coherent light sources intersect at one point on the diffraction part. 
     
     
         4 . A light source device as defined in  claim 1  wherein the at least two coherent light sources are disposed on the same submount. 
     
     
         5 . A light source device as defined in  claim 1  wherein said coherent light sources are a coherent light source that emits red light, a coherent light source that emits blue light, and a coherent light source that emits green light. 
     
     
         6 . A light source device as defined in  claim 1  wherein the light emitted from at least one coherent light source among the coherent light sources passes through the diffraction part without being diffracted by the diffraction part. 
     
     
         7 . A light source device as defined in  claim 1  wherein
 said diffraction part comprises a single diffraction element, and   said diffraction element diffracts the light emitted from at least one coherent light source so that the respective lights emitted from the at least two coherent light sources propagate through the same optical path.   
     
     
         8 . A light source device as defined in  claim 7  wherein said diffraction element is further provided with a lens function. 
     
     
         9 . A light source device as defined in  claim 1  wherein said diffraction part comprises:
 a first diffraction element for receiving at least two lights, and diffracting at least one of the received lights so that the received at least two lights propagate through the same optical path; and   a second diffraction element for diffracting the light emitted from at least one coherent light source among the at least two coherent light sources so that the center axes of the optical propagation paths of the lights emitted from the respective coherent light sources intersect at one point on the first diffraction element.   
     
     
         10 . A light source device as defined in  claim 9  wherein
 said second diffraction element is further provided with a lens function, and   said second diffraction element condenses the respective lights emitted from the at least two coherent light sources so that the respective lights diffracted by the second diffraction element irradiate the same region of the first diffraction element.   
     
     
         11 . A light source device as defined in  claim 7  wherein
 said diffraction element is a volume hologram, and   plural gratings are multiplexed on the volume hologram, which gratings receive the respective lights emitted from the at least two coherent light sources, and change the propagation directions of the respective lights.   
     
     
         12 . A light source device as defined in  claim 7  wherein
 said diffraction element is regionally divided, and   the respective lights that are diffracted in the divided regions of the diffraction element irradiate the same planar region.   
     
     
         13 . A light source device as defined in  claim 9  wherein
 said first diffraction element is regionally divided, and   the respective lights that are diffracted in the divided regions of the first diffraction element irradiate the same planar region.   
     
     
         14 . A light source device as defined in  claim 12  wherein said diffraction element is regionally divided in a lattice pattern. 
     
     
         15 . A two-dimensional image display device comprising:
 at least two coherent light sources;   a diffraction part for diffracting light emitted from at least one coherent light source so that the respective lights emitted from the at least two coherent light sources propagate in the same optical path; and   a two-dimensional spatial light modulation element for receiving the respective lights that are diffracted by the diffraction part to be coaxial beams, said element being provided in a space above the diffraction part.   
     
     
         16 . A two-dimensional image display device as defined in  claim 15  further including:
 a control part for controlling the operations of the at least two coherent light sources; and   said at least two coherent light sources being a coherent light source that emits red light, a coherent light source that emits green light, and a coherent light source that emits blue light; and   said control part controlling the three coherent light sources so that the coherent light sources are time-shared to sequentially emit lights.   
     
     
         17 . A light source device as defined in  claim 9  wherein
 said diffraction element is a volume hologram, and   plural gratings are multiplexed on the volume hologram, which gratings receive the respective lights emitted from the at least two coherent light sources, and change the propagation directions of the respective lights.   
     
     
         18 . A light source device as defined in  claim 13  wherein
 said diffraction element is regionally divided in a lattice pattern.