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:
 an array of light modulators arranged across the flat panel display; and   a backlight comprising a plurality of lasing elements distributed across a surface positioned behind the array of light modulators, such that the backlight illuminates the array of light modulators from behind and the array of light modulators modulates light emitted by the backlight,   wherein:   the lasing elements comprise a plurality of lasing elements of at least one primary color,   the plurality of lasing elements of 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. 
   
     
     
       17. The flat panel display of claim 16, wherein the lasing elements are arranged in an array behind the array of light modulators. 
     
     
       18. The flat panel display of claim 17, wherein the plurality of lasing elements are grouped in laser assemblies that 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. 
     
     
       19. The flat panel display of claim 18, 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. 
     
     
       20. The flat panel display of claim 16, the flat panel display having an illuminated area, wherein each of the plurality of lasing elements is operable to provide light for a region of the flat panel display that is smaller than the entire illuminated area of the flat panel display. 
     
     
       21. The flat panel display of claim 16, wherein the light modulators comprise a liquid crystal display (LCD) panel. 
     
     
       22. 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.   
     
     
       23. The flat panel display of claim 16, wherein the surface across which the plurality of lasing elements is distributed comprises a highly reflective rear reflector. 
     
     
       24. 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. 
     
     
       25. The flat panel display of claim 21, where the LCD panel comprises a color filter film, including an array of red, green, and blue color filters corresponding to respective liquid crystal cells of the LCD panel. 
     
     
       26. The flat panel display of claim 16 wherein different ones of the lasing elements illuminate corresponding different regions of the display and the display comprises an area-dimming control configured to control the lasing elements corresponding to one of the display regions to adjust the brightness in the corresponding region of the display. 
     
     
       27. A flat panel display, comprising:
 a backlight including a plurality of semiconductor diode lasing elements of at least one primary color, wherein:
 the backlight comprises a light guide for substantially distributing light output by the plurality of lasing elements across the flat panel display, 
 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.   
     
     
       28. The flat panel display of claim 27, wherein the plurality of lasing elements are positioned about an exterior edge of the light guide. 
     
     
       29. The flat panel display of claim 27, wherein the plurality of lasing elements are positioned about each exterior edge of the light guide. 
     
     
       30. The flat panel display of claim 27, wherein the plurality of lasing elements are positioned at corners of the light guide. 
     
     
       31. The flat panel display of claim 27, wherein the plurality of lasing elements are arranged about the light guide in a plurality of rows. 
     
     
       32. The flat panel display of claim 31, wherein each row of lasing elements is configured for independent control with respect to lasing elements in at least one other row. 
     
     
       33. The flat panel display of claim 27, comprising a plurality of additional light guides, wherein each light guide corresponds to a row of lasing elements. 
     
     
       34. The flat panel display of claim 33, comprising reflective separators positioned between the plurality of light guides. 
     
     
       35. The flat panel display of claim 27, comprising:
 a polarizing film positioned behind the array of light modulators; and   a diffuser positioned between the backlight and the polarizing film.   
     
     
       36. The flat panel display of claim 27, 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. 
     
     
       37. The flat panel display of claim 27, wherein the light modulators comprise a liquid crystal display (LCD) panel. 
     
     
       38. The flat panel display of claim 37, where the LCD panel comprises a color filter film, including an array of red, green, and blue color filters corresponding to respective liquid crystal cells of the LCD panel. 
     
     
       39. A method for displaying images on a flat panel display, the method comprising:
 illuminating an array of light modulators arranged across the flat panel display with light of a plurality of primary colors and operating the light modulators to modulate the light, wherein, for at least one of the primary colors, the light is provided by a plurality of lasing elements selected such that each of the plurality of lasing elements 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 plurality of 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.   
     
     
       40. The method according to claim 39 comprising mixing light of the plurality of primary colors in a light guide to achieve a generally white light source. 
     
     
       41. The method according to claim 39 comprising controlling one or more of the lasing elements to adjust a brightness in a particular region of the display. 
     
     
       42. An image forming device, comprising:
 a light emitting device comprising laser light sources each comprising a plurality of same color laser modules;   at least one of the laser light sources comprising a plurality of same color laser modules of varying center wavelengths that together form a laser light ensemble;   wherein the light emitting device is configured to emit the laser light ensemble and light from the other laser light sources in a dimming pattern of varying brightnesses;   an array of light modulators of the image forming device, the array of the light modulators arranged across a flat-panel display, and positioned to receive light from the light emitting device and produce an image from the varying brightness dimming pattern.   
     
     
       43. The image forming device according to claim 42, wherein light emitted by the plurality of same color laser modules of varying center wavelengths is mixed together with light emitted by spectrally neighboring same color laser modules. 
     
     
       44. The image forming device according to claim 42, wherein the light emitting device comprises at least three laser light sources each comprising ensembles of different color lights and emitted from the light emitting device as part of an independently controlled dimming pattern. 
     
     
       45. The image forming device according to claim 44, wherein each of the laser light sources emit light increasing contrast of the image. 
     
     
       46. The image forming device according to claim 44, wherein each ensemble comprises a smoothly varying pattern of light. 
     
     
       47. The image forming device according to claim 42, wherein the ensemble provides a lightband having a variation in intensity with wavelength between a low wavelength end of the ensemble and a high wavelength end of the ensemble. 
     
     
       48. The image forming device according to claim 42, wherein the plurality of same color laser modules comprise a low wavelength end module and a high wavelength end module wherein spectra of light emitted by the low wavelength end module and the high wavelength end module have overlapping tails. 
     
     
       49. The image forming device according to claim 42, wherein spectra of light from the plurality of same color laser modules of varying center wavelengths overlap with spectra of spectrally neighboring same color laser modules and the overlap includes wavelengths for which the intensity is above a predetermined percentage of a maximum intensity of the overlapping spectra. 
     
     
       50. An image forming device, comprising:
 a light emitting device comprising laser light sources configured to emit a laser light ensemble;   at least one of the laser light sources comprising a plurality of same color laser modules of varying center wavelengths that together form the laser light ensemble, each laser module offset in wavelength from neighboring laser modules such that each ensemble comprises a smoothly varying intensity of light in a region between a low wavelength light and a high wavelength light of the ensemble;   an array of light modulators of the image forming device, the array of light modulators arranged across a flat panel display, and positioned to receive light from the light emitting device and produce an image from the laser light ensemble,   wherein the light emitting device is configured to control the laser light ensemble to produce independently-controlled dimming patterns for each of three different colors, and the array of light modulators is configured to independently modulate each of three different dimming patterns corresponding to the three different colors, respectively, to produce an image.   
     
     
       51. The image forming device according to claim 50, wherein light from the plurality of same color laser modules of varying center wavelengths is mixed together with spectrally neighboring same color laser modules above a FWHM of a light output of each laser module. 
     
     
       52. The image forming device according to claim 50, wherein spectra of light from the plurality of same color laser modules of varying center wavelengths overlap with spectra of spectrally neighboring same color laser modules and the overlap includes wavelengths for which the intensity is above a predetermined percentage of a maximum intensity of the overlapping spectra. 
     
     
       53. The image forming device according to claim 50, wherein the plurality of same color laser modules comprise a low wavelength end module and a high wavelength end module wherein spectra of light emitted by the low wavelength end module and the high wavelength end module have overlapping tails and the overlapping tails have less than a predetermined percentage of a max brightness of the low wavelength and high wavelength end modules. 
     
     
       54. The image forming device according to claim 50, wherein the ensemble provides a lightband having a variation in intensity with wavelength that is smooth between a low wavelength end of the ensemble and a high wavelength end of the ensemble. 
     
     
       55. A method comprising the steps of:
 illuminating an array of light modulators of an image forming device, the array of the light modulators arranged across a flat-panel display, with a light from laser light ensembles, each ensemble comprising a plurality of same color lights each offset in wavelength from neighboring lights such that each ensemble comprises a smoothly varying intensity of light in a region between a low wavelength light and a high wavelength light of the ensemble;   controlling the ensembles to produce independently-controlled dimming patterns on the modulator for each of 3 different colors; and   independently modulating each of 3 different dimming patterns for each of the 3 different colors so as to produce an image.