This application claims priority to U.S. Provisional Patent Application No. 61/169,714 filed 15 Apr. 2009, hereby incorporated by reference in its entirety.
This invention relates generally to displays. Some non-limiting examples of displays are televisions, home cinema displays, computer displays, commercial displays, stadium displays, electronic billboards and the like. The invention relates to displays of the type that have spatially variable backlights and to backlights suitable for such displays.
Some displays have a spatial light modulator, such as a LCD panel, illuminated by a backlight. Light from the backlight interacts with the spatial light modulator which spatially modulates the light so as to present images to a viewer. The images may be still images or video images for example. In some such displays, the backlight has different areas that are separately controllable so that the intensity of light emitted by the backlight can be made to vary in a desired way over the spatial light modulator. This can provide improved images. Examples of displays that have spatially variable backlights are described in the following patent publications:
PCT Patent Application Publication Nos. WO02/069030, WO03/077013, WO2006/010244 and WO2008/092276.
There is consumer demand for displays that are thin front-to-back. Such displays can be more easily accommodated in some locations than thicker displays and are also less bulky in appearance than thicker displays.
This invention has a range of aspects. Some different aspects provide:
In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions.
The accompanying drawings illustrate non-limiting example embodiments of the invention.
Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive, sense.
Backlight 12 comprises a plurality of individually controllable backlight emitters 16. Each light emitter 16, when on, emits light into a solid angle 17 and therefore illuminates an area of spatial light modulator 14. Light from different individually controlled light emitters 16 overlaps on spatial light modulator 14.
It is generally desirable that the illumination of spatial light modulator 14 vary smoothly from place to place to avoid visible artifacts. In the display shown in
A controller 18 controls the intensity of light emitted by light emitting elements 16 and also the transmissivity of pixels 15 of spatial light modulator 14 in response to image data received at an input 19.
A disadvantage of display 10 is that the distance D required for an optimal distribution of light on spatial light modulator 14 from light emitters 16 may be sufficiently large that the display is thicker than might otherwise be desired.
An image processor 40 receives image data from input 37 and generates signals 41 that control light source driver circuits 42 to cause light source layer 32 to generate light having a desired spatial variation in intensity. Driving signals 41 are also supplied to a light field estimator 44 which produces an estimate 47 of the light field that would be produced by light source layer 32 in response to the driving signals 41. Light field estimator 44 produces light field estimate 47 based in part on light source response characteristics 45. Light source response characteristics 45 may, for example, comprise functions or parameters that are in a data store accessible to light field estimator 44. Light field estimate 47 may comprise a two-dimensional map indicating light intensity as a function of position on light source layer 32 for a given set of signals 41.
In some embodiments, image processor 40 derives signals 41 by a process that generates a lower-resolution version of the image data. This may be done, for example, by a process that involves one or more of low-pass filtering; downsampling; and/or taking local weighted averages of pixel values specified in the image data. The lower resolution version of the image data may be passed through a scaling function to generate signals 41. Advantageously, the application of signals 41 to light source layer 32 results in the emission of light that, at every pixel of spatial light modulator 14, is somewhat more intense than is required for that pixel by the image data. The pixels of spatial light modulator 14 can then be operated to attenuate the light to have an intensity at each pixel as specified by the image data.
In some embodiments, light field estimation comprises, based on control inputs estimated to correspond to control signals 41, estimating electrical potentials corresponding to positions on light source layer 32 and, based on a function relating light output for each area of light source layer 32 to applied electrical potential (or electrical field) estimating light outputs for the positions on light source layer 32. These steps may be performed at a resolution lower than that of modulator 14. If there is an optical path between light source layer 32 and modulator 14 that affects the light emitted by light source layer 32 then light field estimation may comprise applying a point spread function or other model of the effect of the optical path on the light outputs determined above.
A computation unit 48 receives image data and the estimated light field 47 and generates driving values 49 which control the transmission of light by pixels 15 by way of modulator driver circuits 50. In some embodiments, computation unit 48 performs a calculation which comprises dividing an intensity value represented by the image data for a particular location by a value of the estimated light field corresponding to that location. Corrections may be applied to take into account a response of modulator driver circuits and/or spatial light modulator 14 to driving signals 49.
Advantageously light source layer 32 may have significantly fewer control inputs than spatial light modulator 14. In spatial light modulator 14, each pixel 15 can be individually addressable. Light source layer 32 is controllable in a coarser resolution. However, light source layer 32 is constructed such that its light output varies with a desired smoothness.
In some embodiments, this smoothness is expressed by the equation:
where l is the light intensity; La and Lb are the light intensities at two adjacent control points on light source layer 32; xa and xb are the locations of the control points. The difference |xa−xb| is equal to a resolution by which light source layer 32 is controlled. ξ is a parameter having a value in the range of 1.0 to 1.5.
It is not mandatory that control points 65 be point-like. In some embodiments, control points 65 comprise electrically-conductive pads. The pads are relatively large compared to pixels of a spatial light modulator in some embodiments. The pads may be but are not necessarily round. The pads may have rounded corners.
Light source layer 60 may comprise, for example, organic light emitting diode (OLED) layers, substrates coated with or incorporating phosphors, white Field Emissive Display (FED) layers, phosphor-coated plates, electrofluorescent materials, and the like. In general, any electro-luminescent technology may be applied in light source layer 60. These technologies operate on the common principle of converting electrical energy into photon (light) emission. Typically electrical potential across a thin layer or a suitable material results in light emission. The magnitude of the light emission can be approximately proportional to the strength of the electrical field applied across the thin layer material (and the corresponding current flow).
A layer of a potential-distributing material 67 is in contact with and extends between control points 65. The potential-distributing material may comprise a material that is electrically conducting but has electrical resistance such that the electrical potential varies smoothly as one moves between the control points along a path in the potential-distributing material. In some embodiments potential-distributing material 67 may comprise a weak electrical conductor, for example a suitable conducting polymer or other resistive film.
The degree of electrical conductivity of the layer of potential-distributing material 67 may be chosen depending upon the amount of electrical current needed (if any) to actuate light source layer 60. Where light source layer 60 draws only a low or very low current then potential-distributing material 67 may comprise a nearly-insulating dielectric material, for example (although a material having greater electrical conductivity could also be used). Where light source layer 60 is of a type that draws greater amounts of electrical current (for example a strongly emissive layer such as a layer of OLEDs) then potential-distributing material 67 advantageously has a somewhat greater electrical conductivity. In some embodiments the potential-distributing material may have a sheet resistance of 1012 Ω/square or less. In some embodiments the potential-distributing material has a sheet resistance of 107 Ω/square or less. In some embodiments the potential-distributing material has a sheet resistance in the range of 102 or 103 to 107 Ω/square.
If all of control points 65 are maintained at the same electrical potential by the control circuits then the electric field across all portions of light generating layer 62 is fairly uniform with the result that the light emitted by light source layer 60 is fairly spatially uniform.
On the other hand, if different ones of control points 65 are maintained at different electrical potentials then the electrical potential will vary from place to place on electrode structure 64. This variation of electrical potential will, in general, be smooth because of the presence of potential-distributing material 67. The intensity of light emitted by light emitting layer 60 will therefore vary from location to location in a smooth manner with the overall variation in light intensity determined by the combination of electrical potentials that are applied to control points 65.
Control points 65 may, for example, be arranged in a regular array, such as a grid, a hexagonal or triangular array, a rectangular array or the like. It is not mandatory that the control points have a uniform spatial density or that all neighboring control points be equidistant from one another.
Preferably potential-distributing layer 67 has a reasonably high electrical resistivity so that when different control points 65 are maintained at different electrical potentials, the electrical current flowing between different ones of control points 65 through potential-distributing layer 67 is fairly small and does not dissipate significant amounts of energy so as to cause potential-distributing layer 67 or light generating layer 62 to overheat.
In displays according to some embodiments, there are in the range of 50 to 5000 control points. In some embodiments, a ratio of control points to pixels is in the range of 1:200 to 1:40,000. In some embodiments the display comprises 1 million or more pixels whereas the number of control points is a few thousand or less.
In some embodiments, a light emitting layer incorporates active electronics. For example,
In some embodiments, an optically absorbing layer is applied to the front surface of light emitting layer 32 to reduce the intensity of light emitted at brighter regions (e.g. regions corresponding to control points) so as to permit the light output of the light emitting layer to be set to be completely uniform.
In some embodiments, the light emitted by light source layer 62 is monochrome. In other embodiments, the emitted light spans a broader color gamut. For example, the emitted light may comprise broadband light or a mixture of light having different spectra. In some specific example embodiments light source layer 62 emits light that is white or can be filtered to yield white light. White light may, for example, be generated by:
In some embodiments light from two or more light source layers 62 is combined to provide illumination of a spatial light modulator 14. In some embodiments, the different light source layers 62 are constructed to provide light having spectral characteristics. For example, a color display may comprise separate red-, green- and blue-emitting light source layers 62.
In the embodiment illustrated in
In display 100, each light emitter 104 may be separately controlled. In the illustrated embodiment, a three-channel controller 112 receives image data 115 defining color images. Controller 112 generates sets of control signals 106A, 106B and 106C which control driving circuits for light emitters 104A, 104B and 104C respectively. Controller 112 estimates the resulting amount of light of each color at pixels of spatial light modulator 102. This estimation is based on properties 107A, 107B and 107C of the light emitters 104A, 104B and 104C respectively. Controller 112 generates control signals 114 for the pixels of spatial light modulator 102. The control signals are generated from the estimated amounts of light and the image data. In an alternative embodiment, the display of different colors is time multiplexed. In such embodiments, spatial light modulator 102 may be a monochrome spatial light modulator.
Controller 220 also generates control signals 227 for a spatial light modulator 229. Control signals 227 control pixels of spatial light modulator 229 by way of a suitable driving circuit 230. Controller 230 may, for example, have a construction like that of controller 34 which is described above.
In embodiments having a potential-distributing layer, it is not mandatory that the potential-distributing layer be uniform in resistivity. In some embodiments the potential-distributing layer is variably doped, has a variable thickness or is otherwise spatially varied to produce desirable electrical field characteristics.
An alternative way to smoothly control light output based on a relatively small number of control inputs is to provide a light absorber, such as a LCD, controlled as described above. In such embodiments, the light transmission at different spatial locations of the LCD is a function of the electrical potential at those locations.
While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/US2010/029941 | 4/5/2010 | WO | 00 | 9/20/2011 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2010/120582 | 10/21/2010 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5634835 | Wu | Jun 1997 | A |
5756147 | Wu | May 1998 | A |
5978142 | Blackham et al. | Nov 1999 | A |
6791260 | Komatsu | Sep 2004 | B2 |
7271427 | Tsubokura | Sep 2007 | B2 |
7505018 | Feng et al. | Mar 2009 | B2 |
7532192 | Feng et al. | May 2009 | B2 |
7573457 | Daly | Aug 2009 | B2 |
8199401 | Ninan et al. | Jun 2012 | B2 |
8446351 | Whitehead et al. | May 2013 | B2 |
20050105284 | Ishizuka | May 2005 | A1 |
20070097321 | Whitehead et al. | May 2007 | A1 |
20070146257 | Whitehead et al. | Jun 2007 | A1 |
20070268211 | Whitehead et al. | Nov 2007 | A1 |
20070268224 | Whitehead et al. | Nov 2007 | A1 |
20100007577 | Ninan et al. | Jan 2010 | A1 |
20100007599 | Kerofsky | Jan 2010 | A1 |
20100020003 | Feng | Jan 2010 | A1 |
20100079364 | Feng | Apr 2010 | A1 |
20100277515 | Ward et al. | Nov 2010 | A1 |
Number | Date | Country |
---|---|---|
1201092 | Aug 1970 | GB |
1299870 | Dec 1972 | GB |
S61-14743 | Jan 1986 | JP |
2002156633 | May 2002 | JP |
2005-071634 | Mar 2005 | JP |
2006-201079 | Aug 2006 | JP |
2007-234599 | Sep 2007 | JP |
2008-218377 | Sep 2008 | JP |
2007-0080441 | Aug 2004 | KR |
2004-0096186 | Nov 2004 | KR |
2008-0032440 | Apr 2008 | KR |
10-0866542 | Nov 2008 | KR |
02069030 | Sep 2002 | WO |
03077013 | Sep 2003 | WO |
2005015960 | Feb 2005 | WO |
2006010244 | Feb 2006 | WO |
2007017795 | Feb 2007 | WO |
2008068925 | Jun 2008 | WO |
2008092276 | Aug 2008 | WO |
Entry |
---|
Chae “Translation of KP 10-2004-0096186” Nov. 16, 2004. |
Number | Date | Country | |
---|---|---|---|
20120032999 A1 | Feb 2012 | US |
Number | Date | Country | |
---|---|---|---|
61169714 | Apr 2009 | US |