Projecting an image using a moving illumination beam

Abstract

According to one embodiment, an image projector has a spatial light modulator (SLM) adapted to modulate illumination from a laser with a spatial pattern such that the modulated illumination projects an image on a viewing screen. The image projector further has an optical diffuser located on an optical path between the laser and the SLM. The laser is adapted to illuminate the SLM through the optical diffuser to create an illuminated area at the SLM. The optical diffuser is adapted to introduce an angular spread into the light transmitted therethrough. The image projector is adapted to move the illuminated area with respect to the SLM to mitigate speckle in the projected image.

1 - 15 . (canceled) 
     
     
         16 . A method of projecting an image on a viewing screen, the method comprising:
 with a laser, illuminating a portion of a surface of a spatial light modulator (SLM) by passing a light beam through an optical diffuser, wherein the optical diffuser is adapted to angularly spread the light beam incident thereon so that, at each pixel of a plurality of pixels of the SLM, an illumination light beam received at said portion of the surface has light rays corresponding to a range of incident angles;   modulating said illumination light beam with a spatial pattern displayed by the plurality of pixels of the SLM to form said image; and   moving the illumination light beam across the SLM in a manner that causes a change, at each pixel of the plurality, of relative optical phases of the light rays having different incident angles.   
     
     
         17 . The method of  claim 16 , wherein the step of moving comprises moving a lens located along an optical path between the laser and the SLM to move the illumination light beam across the SLM. 
     
     
         18 . The method of  claim 16 , wherein the step of moving comprises moving a mirror located along an optical path between the laser and the SLM to move the illumination light beam. 
     
     
         19 . The method of  claim 18 , wherein the step of moving further comprises rotating the mirror about a rotation axis that is not parallel to a normal to a reflecting surface of the mirror. 
     
     
         20 . The method of  claim 16 , further comprising:
 with a second laser, illuminating a portion of the surface of the SLM by passing a corresponding second light beam through the optical diffuser, wherein the two lasers are emitting light of respective different colors;   modulating said second illuminating light beam with a corresponding spatial pattern displayed by the plurality of pixels of the SLM; and   time-division multiplexing transmission of the light from the two lasers to the SLM.   
     
     
         21 . The method of  claim 20 , further comprising spatially overlapping the light beams emitted by the two lasers using a color combiner. 
     
     
         22 . The method of  claim 17 , further comprising configuring the lens to image an output aperture of the laser onto the surface of the SLM. 
     
     
         23 . The method of  claim 17 , wherein:
 the lens and the optical diffuser are implemented as a monolithic optical element; and   the step of moving the mirror comprises moving the optical diffuser.   
     
     
         24 . The method of  claim 19 , wherein:
 the mirror is one surface of a wedge; and   the step of rotating comprises rotating the wedge.   
     
     
         25 . The method of  claim 16 , wherein the step of modulating comprises transmitting a portion of the illumination light beam through the SLM. 
     
     
         26 . The method of  claim 16 , wherein:
 the step of illuminating comprises directing the light beam passed through the optical diffuser toward the surface of the SLM by passing said light beam through a polarization beam splitter (PBS) and a quarter-wave plate located along an optical path between the PBS and the SLM; and   the step of modulating comprises directing a spatially modulated beam back to the PBS through the quarter-wave plate.   
     
     
         27 . The method of  claim 16 , further comprising configuring said laser to emit light having different angular spreads along different axes orthogonal to an emission axis of the laser. 
     
     
         28 . The method of  claim 16 , wherein the step of passing comprises introducing into light transmitted through the optical diffuser different amounts of angular spread along different directions. 
     
     
         29 . The method of  claim 16 , wherein the step of passing comprises changing a cross section of the light beam that is being passed through the optical diffuser from substantially circular or oval to substantially rectangular.