Laser illuminated backlight for flat panel displays

Abstract

Laser lit flat panel displays are disclosed including edge-lit and direct lit backlights. In certain embodiments, laser assemblies are selected to obtain bandwidth distributions to reduce speckle.

What is claimed is: 
     
       1. A flat panel display, comprising:
 an array of light modulators arranged across the flat panel display; and   a backlight comprising a plurality of laser assemblies distributed across a surface positioned behind the array of light modulators, such that the plurality of laser assemblies directly illuminate the array of light modulators from behind and the array of light modulators modulates light emitted by the backlight, wherein:
 each laser assembly comprises a plurality of lasing elements of at least one primary color, 
 at least two of the plurality of laser assemblies include lasing elements of the same primary color, 
 the plurality of lasing elements of at least one of the three primary colors are selected such that each lasing element emits a laser beam with a center wavelength λ 0i  and a spectral bandwidth Δλ i , 
 the center wavelength of at least one of the lasing elements is wavelength-shifted with respect to the center wavelength of at least one other lasing element, and 
 said laser beams, when combined, have an ensemble spectrum Λ with an overlap parameter γ= Δλ i   / S i   , with  Δλ i    being a mean spectral bandwidth of the lasing elements and  S i    being a mean wavelength shift between the center wavelengths λ 0i  of the at least one and the at least one other lasing elements, with  Δλ i    and  S i    selected such that γ≧1. 
   
     
     
       2. The flat panel display of  claim 1 , wherein each laser assembly includes at least one lasing element of each primary color. 
     
     
       3. The flat panel display of  claim 1 , wherein the laser assemblies are arranged in an array behind the array of light modulators. 
     
     
       4. The flat panel display of  claim 3 , wherein each laser assembly comprises at least one lasing element of each of the at least one primary color. 
     
     
       5. The flat panel display of  claim 3 , comprising diffusion optics corresponding to the plurality of laser assemblies. 
     
     
       6. The flat panel display of  claim 5 , wherein the respective diffusion optics for each laser assembly are selected based on a desired size of a region for which the respective laser assembly provides light. 
     
     
       7. The flat panel display of  claim 3 , wherein the plurality of laser assemblies are arranged in rows and columns, and wherein each laser assembly is configured to be controlled independently of at least one laser assembly in the same row and at least one laser assembly in the same column as the laser assembly. 
     
     
       8. The flat panel display of  claim 7 , wherein at least one laser assembly is configured such that the brightness of one color of laser is controllable independently of lasers of other colors in the assembly. 
     
     
       9. The flat panel display of  claim 1 , the flat panel display having an illuminated area, wherein each of the plurality of laser assemblies provides light for a region of the flat panel display that is smaller than the entire illuminated area of the flat panel display. 
     
     
       10. The flat panel display of  claim 1 , wherein the light modulators comprise a liquid crystal display (LCD) panel. 
     
     
       11. A flat panel display, comprising:
 an array of light modulators arranged across the flat panel display;   a backlight comprising a plurality of laser assemblies distributed across a surface positioned behind the array of light modulators, such that the plurality of laser assemblies directly illuminate the array of light modulators from behind and the array of light modulators modulates light emitted by the backlight, wherein:
 each laser assembly comprises a plurality of lasing elements of at least one primary color, and 
 at least two of the plurality of laser assemblies include lasing elements of the same primary color; and 
   a plurality of optical elements for diffusing light from the laser assemblies across corresponding regions of the array of light modulators.   
     
     
       12. The flat panel display of  claim 11 , wherein each laser assembly comprises at least one lasing element of each of the at least one primary color. 
     
     
       13. The flat panel display of  claim 11 , wherein each laser assembly is configured to be controlled independently of at least one laser assembly in the same row and at least one laser assembly in the same column as the laser assembly. 
     
     
       14. The flat panel display of  claim 13 , wherein the laser assemblies are configured such that the brightness of at least one color within each laser assembly can be controlled independently of other colors in the laser assembly. 
     
     
       15. The flat panel display of  claim 11 , the flat panel display having an illuminated area, wherein each corresponding region is smaller than the entire illuminated area of the flat panel display. 
     
     
       16. A flat panel display, comprising:
 a backlight including a plurality of semiconductor diode lasing elements of at least one primary color arranged in a plurality of laser assemblies, wherein:   the backlight comprises a light guide for substantially distributing light output by the plurality of laser assemblies across the flat panel display,   the plurality of laser assemblies are positioned about an exterior edge of the light guide,   the plurality of lasing elements of the at least one primary color are selected such that each lasing element emits a laser beam with a center wavelength λ 0i  and a spectral bandwidth Δλ i ,   the center wavelength of at least one of the lasing elements is wavelength-shifted with respect to the center wavelength of at least one other lasing element, and   said laser beams, when combined, have an ensemble spectrum Λ with an overlap parameter γ= Δλ i   / S i    with  Δλ i    being a mean spectral bandwidth of the lasing elements and  S i    being a mean wavelength shift between the center wavelengths λ 0i  of the at least one and the at least one other lasing elements, with  Δλ i    and  S i    selected such that γ≧1; and   an array of light modulators arranged across the flat panel display for modulating light emitted by the backlight.    
     
     
       17. The flat panel display of claim 16, wherein each laser assembly includes at least one lasing element of each of three primary colors.  
     
     
       18. The flat panel display of claim 16, wherein at least one laser assembly includes a plurality of lasing elements of each of three primary colors.  
     
     
       19. The flat panel display of claim 16, wherein the light modulators comprise a liquid crystal display (LCD) panel.  
     
     
       20. The flat panel display of claim 16, comprising diffusion optics corresponding to the plurality of laser assemblies.  
     
     
       21. The flat panel display of claim 16, wherein the plurality of laser assemblies are positioned about each exterior edge of the light guide.  
     
     
       22. The flat panel display of claim 16, wherein the plurality of laser assemblies are positioned at comers of the light guide.  
     
     
       23. The flat panel display of claim 16, wherein the plurality of laser assemblies are arranged about the light guide in a plurality of rows.  
     
     
       24. The flat panel display of claim 23, wherein each row of laser assemblies is configured for independent control with respect to laser assemblies in at least one other row.  
     
     
       25. The flat panel display of claim 24, wherein the laser assemblies are configured such that the brightness of at least one color within at least one laser assembly can be controlled independently of other colors in the laser assembly.  
     
     
       26. The flat panel display of claim 23, comprising a plurality of additional light guides, wherein each light guide corresponds to a row of laser assemblies.  
     
     
       27. The flat panel display of claim 26, comprising reflective separators positioned between the plurality of light guides.  
     
     
       28. The flat panel display of claim 16, wherein the backlight comprises at least one light emitting diode to illuminate the light modulators.  
     
     
       29. The flat panel display of claim 16, comprising:
 a polarizing film positioned behind the array of light modulators; and   a diffuser positioned between the backlight and the polarizing film.    
     
     
       30. The flat panel display of claim 16, wherein the backlight includes lasing elements corresponding to at least first and second primary colors, and wherein the backlight includes more lasing elements of the first primary color than of the second primary color.