Compact Holographic Illumination Device

Abstract

There is provided a colour sequential illumination device comprising in series: first and second light sources; a condenser lens; and a grating device. The grating device comprises at least one Bragg grating. The condenser lens directs light from the first and second sources into the grating device at first and second incidence angles respectively. The grating device diffracts light from the first and second sources into a common direction. Desirably, the Bragg gratings are Electrically Switchable Bragg Gratings. In one embodiment of the invention the light sources are Light Emitting Diodes. Alternatively lasers may be used.

1 . An illumination device comprising:
 at least one light source;   a collimating lens;   at least one Bragg grating; and   a diffractive optical element (DOE),   wherein said grating device comprises at least one Bragg grating; a light input port and a light output port,   wherein said DOE modifies the wavefront characteristics of said light to control the spatial distribution of the illumination provided by said light at an illumination surface.   
     
     
         2 . The apparatus of  claim 1 , wherein said at least one Bragg grating is an electrically switchable Bragg grating. 
     
     
         3 . The apparatus of  claim 1 , wherein said at least one Bragg grating multiplexes gratings for diffracting different colors. 
     
     
         4 . The apparatus of  claim 1 , wherein said DOE modifies said illumination to compensate for at least one selected from the group consisting of source illumination distribution, optical aberration and vignetting. 
     
     
         5 . The apparatus of  claim 1 , wherein said DOE is a computer-generated hologram. 
     
     
         6 . The apparatus of  claim 1 , wherein said at least one Bragg grating and said DOE each have diffusing properties for controlling the spatial distribution of the illumination at said illumination surface. 
     
     
         7 . The apparatus of  claim 1 , wherein said DOE modifies the beam shape of said light. 
     
     
         8 . The apparatus of  claim 1 , wherein said DOE diffracts two or more colors. 
     
     
         9 . The apparatus of  claim 1 , wherein said at least one light source comprises red, green and blue emitters. 
     
     
         10 . The apparatus of  claim 1 , wherein said at least one light source comprises at least two emitters of the same color. 
     
     
         11 . The apparatus of  claim 1 , wherein said at least one light source comprises first and second emitters of the same color pulsed on and off in anti-phase. 
     
     
         12 . The apparatus of  claim 1 , wherein said at least one light source comprise light emitting diodes. or lasers. 
     
     
         13 . The apparatus of  claim 1 , further wherein said at least one light source are disposed on a curved substrate. 
     
     
         14 . The apparatus of  claim 1 , further comprising a beam shaping optical element. 
     
     
         15 . The apparatus of  claim 1 , wherein at least one beam shaping optical element is disposed between said at least one light source and said condenser lens. 
     
     
         16 . The apparatus of  claim 1 , further comprising at least one light guiding element for controlling the light beam geometrical characteristics from said at least one light source. 
     
     
         17 . The apparatus of  claim 1 , further comprising a light control film for blocking stray light. 
     
     
         18 . The apparatus of  claim 1 , further comprising a dichroic beamsplitter. 
     
     
         19 . The apparatus of  claim 1 , wherein said at least one Bragg grating comprises: overlapping first and second Bragg gratings and overlapping third and fourth Bragg gratings, wherein said second and third Bragg gratings sandwich a half wave plate, wherein said first and third Bragg gratings have similar optical prescriptions and said second, and fourth Bragg grating have similar optical prescriptions. 
     
     
         20 . The apparatus of  claim 1 , used to illuminate a microdisplay disposed in proximity to said illumination surface.