Patent Publication Number: US-2005134525-A1

Title: Control system for a tiled large-screen emissive display

Description:
FIELD OF THE INVENTION  
      The present invention relates to a control system and method for a modular large-screen emissive display such as an organic light-emitting diode (OLED) display.  
     BACKGROUND OF THE INVENTION  
      OLED technology incorporates organic luminescent materials that, when sandwiched between electrodes and subjected to a DC electric current, produce intense light of a variety of colors. These OLED structures can be combined into the picture elements, or pixels, that comprise a display. OLEDs are also useful in a variety of applications as discrete light-emitting devices or as the active element of light-emitting arrays or displays, such as flat-panel displays in watches, telephones, laptop computers, pagers, cellular phones, calculators, and the like. To date, the use of light-emitting arrays or displays has been largely limited to small-screen applications such as those mentioned above.  
      The market is now, however, demanding larger displays with the flexibility to customize display sizes. For example, advertisers use standard sizes for marketing materials; however, those sizes differ based on location. Therefore, a standard display size for the United Kingdom differs from that of Canada or Australia. Additionally, advertisers at trade shows need bright, eye-catching, flexible systems that are easily portable and easy to assemble/disassemble. Still another rising market for customizable large display systems is the control room industry, in which maximum display quantity, quality, and viewing angles are critical. Demands for large-screen display applications possessing higher quality and higher light output has led the industry to turn to alternative display technologies that replace older LED and liquid crystal displays, i.e. LCDs. For example, LCDs fail to provide the bright, high light output, larger viewing angles, and high resolution and speed requirements that the large-screen display market demands. By contrast, OLED technology promises bright, vivid colors in high resolution and at wider viewing angles. However, the use of OLED technology in large-screen display applications, such as outdoor or indoor stadium displays, large marketing advertisement displays, and mass-public informational displays, is only beginning to emerge.  
      Modular or tiled emissive displays, such as e.g. tiled OLED displays, are made from smaller modules or displays that are then combined into larger tiles. These tiled emissive displays are manufactured as a complete unit that can be further combined with other tiles to create displays of any size and shape. However, in order to handle the control algorithms for large-screen emissive displays, very complex control software with high bandwidth and a high level of processing power is required. What is needed is a less complex software control system for control and calibration of a large-screen emissive display. Furthermore, what is further needed is software control system for automatically configuring a modular, scalable, tiled emissive display.  
      An example of a software control system for a display is described in U.S. Pat. No. 5,739,809. The system described includes a processor programmed to control and optionally also calibrate a display in response to user selection of displayed virtual controls. Preferred embodiments of the system include circuitry within the display device, which operates under control of software in response to user-entered commands for adjustment of parameters of the display device. In preferred embodiments, the processor is programmed with software that stores multiple types of data, including display parameters measured during calibration and user-specified adjustment data indicative of differences between first and second sets of display control parameters, in separate data files. The software also executes a locking operation that disables mechanical controls on the display device, periodically and automatically polls the status of the display, and automatically corrects any display parameter with a value that differs from a desired value.  
      Although the display calibration and control method described in U.S. Pat. No. 5,739,809 provides a suitable means for controlling a display apparatus, the software control system described is very complex for use in a large-screen emissive display application.  
     SUMMARY OF THE INVENTION  
      It is therefore an object of the invention to provide a system and method for controlling and calibrating a tiled large-screen emissive display with reduced software complexity as compared with conventional systems.  
      It is yet another object of this invention to provide a control system an method capable of associating and configuring multiple emissive display tiles automatically within a tiled large-screen emissive display application.  
      The above objectives are accomplished by a method and device according to the present invention.  
      The present invention relates to a method for controlling a tiled large-screen emissive display. The emissive display comprises at least a plurality of first subdivisions, each of said first subdivisions comprising a plurality of emissive devices. The method comprises 
          for each of the first subdivisions, setting the emissive devices so that each of said first subdivisions is optimized with respect to a first subdivision target value for that first subdivision and 
 
 after setting the emissive devices, 
    for the emissive display, setting the first subdivisions so that said emissive display is optimized with respect to an emissive display target value for said emissive display. In this embodiment of the method, the first subdivisions may be emissive display tiles.        

      The method of controlling a tiled large-screen emissive display can also comprise control on additional levels. The plurality of first subdivisions of the tiled large-screen emissive display may then be grouped into a plurality of second subdivisions, the number of first subdivisions being larger than the number of second subdivisions. Setting the first subdivisions in the method of controlling as described above may then be performed by 
          for each of the second subdivisions, setting the first subdivisions so that each of said second subdivisions is optimized with respect to a second subdivision target value for that second subdivision, and thereafter     for the emissive display, setting the second subdivisions so that the emissive display is optimized with respect to an emissive display target value for said emissive display.        

      In this embodiment of the method, the first subdivisions may e.g. refer to emissive display modules, while the second subdivisions may refer to emissive display tiles. The implementation of the first and second subdivisions may depend on the implementation of the display.  
      If a further level of control is introduced for a tiled large-screen emissive display wherein the plurality of second subdivisions are grouped into a plurality of further subdivisions, the number of further subdivisions being smaller than the number of second subdivisions; said setting the second subdivisions in the method of controlling may be performed by 
          for each further subdivision, setting the second subdivisions so that the further subdivision is optimized with respect to a further subdivision target value for said further subdivision, and thereafter     for the emissive display, setting the further subdivisions so that the emissive display is optimized with respect to an emissive display target value for said emissive display.        

      The further subdivisions may e.g. relate to supertiles, grouping a number of tiles e.g. each being an array of r by s tiles.  
      In a specific embodiment, a method is disclosed for controlling a tiled large-screen emissive display. The emissive display comprises a set of emissive display tiles, each of said emissive display tiles comprising a set of emissive display modules and each of said emissive display modules comprising a plurality of emissive display devices. The method comprises 
          for each emissive display module, setting the emissive display devices so that each emissive display module is optimized with respect to a module target value for that emissive display module,     for each emissive display tile, setting the emissive display modules taking into account the module target value for each emissive display module, so that each emissive display tile is optimized with respect to a tile target value for that emissive display tile, and     for the emissive display, setting the emissive display tiles taking into account the tile target values for each emissive display tile so that the emissive display is optimized with respect to a display target value for that emissive display.        

      The emissive display can be an OLED display or any other type of emissive display. Although in the detailed description an illustration is given for controlling the tiled large-screen emissive display on three levels, i.e. devices—also called pixels—, modules and tiles, the number of levels for controlling the tiled large-screen emissive display can be larger, e.g. by introducing super tiles grouping a number of tiles e.g. each an array of r by s tiles, or even by introducing super super tiles grouping a number of super tiles. On the other hand, the number of control levels also can be limited to two levels, i.e. controlling the devices or pixels and the tiles.  
      In the above described methods, setting the emissive devices may comprise setting the emissive devices so that they are within 10%, preferably within 5%, most preferably within 0.8% of the first subdivision target value of that first subdivision. Furthermore setting the first subdivisions may comprise setting the first subdivisions so that they are within 10%, preferably within 5%, most preferably within 0.8% of the emissive display target value of that emissive display or within 10%, preferably within 5%, most preferably within 0.8% of the second subdivision target value of that second subdivision, depending on the number of control levels that are used in the method of controlling, i.e. depending on the presence of a set of second subdivisions wherein the plurality of first subdivisions may be grouped.  
      In a similar way, depending on the number of control levels, setting the second subdivisions may comprise setting the second subdivisions so that they are within 10%, preferably within 5% and most preferably within 0.8% of the emissive display target value of the emissive display or within 10%, preferably within 5% and most preferably within 0.8% of the further subdivision target value of that further subdivision. The latter occurs if the second subdivisions are grouped in a set of further subdivisions, which are themselves grouped in the emissive display.  
      If further subdivisions are present, setting the further subdivisions may be so that they are within 10%, more preferably within 5% and most preferably within 0.8% of the emissive display target value of the emissive display.  
      In case of all the above limitations are target values, the actual target value that can be reached can depend on the parameter that is chosen as the target parameter, for example, 0.8% can be achieved for the parameter brightness. This would be a severe condition, for other parameters good target level values could be higher than 0.8%.  
      In determining any or more of the first subdivision target value, second subdivision target value, further subdivision target value and/or emissive display target value, an environmental parameter may be taken into account. The different target values correspond with the different control levels that are introduced. This environmental parameter may be obtained by measuring a temperature of at least one emissive device, first subdivision, second subdivision or further subdivision. This also may include measuring an ambient temperature and estimating the temperature of at least one emissive device, first subdivision, second subdivision or further subdivision from the measured ambient temperature. The environmental parameter also may be any or more of ambient illumination, ambient humidity.  
      Determining any or more of the first subdivision target value, second subdivision target value, further subdivision target value and/or emissive display target value, may include taking into account an operating parameter stored on the first subdivision or, if present, second subdivision or further subdivision. This operating parameter may comprise any or more of age (e.g. determined by the voltage change across the emissive elements) of the first subdivision or—if present—of the second subdivision or of the further subdivision, or total ON time of the first subdivision or—if present—of the second subdivision or of the further subdivision.  
      Setting the emissive devices also may comprise retrieving and adjusting a control parameter.  
      Setting the emissive devices, the first subdivisions, the second subdivisions and the further subdivisions may also comprise using an adaptive calibration algorithm for calibrating the emissive devices, the first subdivisions, the second subdivisions and the further subdivisions. This calibration may be performed periodically. It may comprise calibration of brightness and/or color.  
      The invention also relates to a computer program product for executing a method of controlling a tiled large-screen emissive display according to the present invention when executed on a computing device associated with a tiled large-screen emissive display, the methods of controlling being according to the methods described above. The invention further relates to a readable data storage device storing this computer program or to the transmission of this computer program over a local or wide area telecommunications network.  
      The invention furthermore relates to a control unit for use with a tiled large-screen emissive display, said emissive display comprising a set of first subdivisions, each of said first subdivisions comprising a plurality of emissive devices, the control unit being adapted for controlling setting of the tiled large-screen emissive display, the control unit comprising: 
          means for setting the emissive devices of each first subdivision so that each first subdivision is optimized to a first subdivision target value for that first subdivision,     means for setting the first subdivisions of the emissive display taking into account the first subdivision target value for each first subdivision, so that the emissive display is optimized to an emissive display target value for that emissive display.        

      If a larger number of control levels is used, e.g. if the first subdivisions are grouped in a set of second subdivisions, the means for setting the first subdivisions may comprise 
          means for setting the first subdivisions of each of the second subdivisions, taking into account the first subdivision target value for each first subdivision, so that the second subdivisions are optimized to a second subdivision target value for that second subdivision and     means for setting the second subdivisions of the emissive display taking into account the second subdivision target values for each second subdivision, so that the emissive display is optimized to an emissive display target value for that emissive display.        

      The devices, first subdivisions, second subdivisions and further subdivisions may relate to emissive display pixels, emissive display modules, emissive display tiles and emissive display supertiles respectively. The number of control levels used for controlling the tiled large-screen display can be even larger, depending on the need and the size of the large-screen display. Extrapolation of the above to more control levels lies within the skills of a person skilled in the art.  
      These and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a functional block diagram of a large-screen OLED display system having a modular architecture and being suitable for use with the control system of the present invention.  
       FIG. 2A  schematically illustrates the application of a multi-line method of signal and power distribution for an OLED display.  
       FIG. 2B  schematically illustrates the application of a daisy-chain method of signal and power distribution for an OLED display.  
       FIG. 3  illustrates a functional block diagram of an OLED display control system in accordance with an embodiment of the present invention.  
       FIG. 4  illustrates a flow diagram of a method of operating a tiled OLED display using the OLED display control system according to an embodiment of the present invention.  
       FIG. 5  illustrates a flow diagram of a method of monitoring a tiled OLED display using the OLED display control system according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENT  
      The present invention will be described with respect to particular embodiments and with reference to the drawings, but the invention is not limited thereto but only by the claims. The drawings are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes.  
      The present invention relates to a control system for use with a modular, tiled, large-screen emissive display application. The control system of the present invention performs operations to initialize and configure an emissive display system during the physical assembly of emissive tiles, addresses the emissive display tiles, and controls the emissive display tiles for uniform image and proper image size. Furthermore, the control system of the present invention handles additional features, such as hot swap capability to replace failed emissive display tiles and a mechanism to detect a new emissive display tile, and video features, such as gamma curve adjustments, color point adjustments, brightness adjustments, and high broadcast capability. Based upon a known data stream, the control system determines the video content and makes adjustments accordingly. Lastly, the control system of the present invention is able to convert display deficiencies into features, i.e. compensates for deficiencies to improve display image while hiding a particular deficiency.  
      By way of example, the method and system for controlling a tiled large-screen emissive display system will be described with respect to a tiled large-screen OLED display system. Nevertheless, the method and system for controlling the tiled large-screen emissive display are not limited to OLED tiles but any emissive display tiles suitable for tiled large-screen emissive displays can be used.  
       FIG. 1  is a functional block diagram of a large-screen OLED display system  100  having a modular architecture and being suitable for use with the control system according to embodiments of the present invention. OLED display system  100  includes a system controller  110 , a digitizer  112 , and a display wall  114  that further includes a collection of OLED sub-displays  116 , for example, OLED sub-displays  116   a,    116   b,    116   c,  and  116   d.  Also shown in  FIG. 1 , as an example, is an expanded view of OLED sub-display  116   c.  In this example, OLED sub-display  116 c further includes an n×m array, e.g. a 3×3 array, of OLED tiles  118 . More specifically, OLED sub-display  116   c  includes OLED tiles  118   a,    118   b,    118   c,    118   d,    118   e,    118   f,    118   g,    118   h,  and  118   j.  Furthermore, each of OLED tiles  118  includes a p×q array, e.g. a 3×3 array, of OLED modules  120 . More specifically, each OLED tile  118  comprises, in the example given, OLED modules  120   a,    120   b,    120   c,    120   d,    120   e,    120   f,    120   g,    120   h,  and  120   j.  Additionally, each OLED module  120  further includes an array of OLED devices (not shown in detail in the drawings), i.e. for example an array of red, green, blue (RGB) pixels. In general, the 3×3 arrangements shown in  FIG. 1  are simply illustrative in nature; OLED sub-displays  116   a,    116   b,    116   c,  and  116   d  each may include any number of OLED tiles  118  and, similarly, OLED tiles  118  each may include any number of OLED modules  120 . Lastly, OLED display system  100  includes one or more ambient environment controllers (AECs)  122 , for example, AECs  122   a,    122   b,    122   c,  and  122   d.    
      System controller  110  is representative of any standard processing device, such as a personal computer (PC), laptop, or host computer, capable of running system control software for operating OLED display system  100 . System controller  110  functions as the system-level controller of OLED display system  100 . System controller  110  may be electrically connected to digitizer  112  via a standard connector such as RS232, through which a communications link is established.  
      Digitizer  112  is a well-known device that converts any video signal to a digital format that can be displayed by OLED display system  100 . Digitizer  112  serves as an “input manager” for display wall  114 . Various video sources, such as those from system controller  110 , that provide signals to be displayed upon display wall  114  may be connected to digitizer  112 . Digitizer  112  converts these input signals to a digital signal that is compatible with display wall  114 .  
      Control data signals, such as serial control data signals, from system controller  110  and video data signals, such as serial RGB video data signals, from any source are supplied to display wall  114  via digitizer  112 . The video data signals contain the current video frame information to be displayed on OLED sub-displays  116   a,    116   b,    116   c,    116   d.  The control data signals provide control information to OLED sub-displays  116   a,    116   b,    116   c,    116   d,  such as color temperature, gamma, and imaging information for each OLED tile  118  within each OLED sub-display  116 . Several methods of signal and power distribution can be used within the display wall  114 , e.g. a multi-line method, a star distribution method, or a daisy-chain method. A multi-line method of signal distribution is implemented within display wall  114 , and is illustrated in  FIG. 2A .  
      A data input signal DATA IN  140  from a central processing unit (not shown) is supplied to an input of data reclocker  142   a.  Data input signal  140  is representative of e.g. serial video and control data. Data reclocker  142   a  subsequently re-transmits this serial video and control data to one OLED tile  118  as well as to a next data reclocker  142 , i.e. in the example given, to an input of data reclocker  142   b  and to a data input connector of OLED tile  118   g.  Similarly, data reclocker  142   b  transmits the received serial video and control data signal to an input of data reclocker  142   c  and to data input connector of OLED tile  118   h.  Finally, data reclocker  142   c  transmits the received serial video and control data to a data input connector of OLED tile  118   j.  This way, the DATA IN signal  140  is distributed to all OLED tiles  118  of one row of the OLED sub-display  116 . It is to be noted that the data links in the OLED display are bi-directional, so it is also possible to place data reclockers  142   a,    142   b,  and  142   c  on top of OLED sub-display  116 , instead of placing them at the bottom, thus feeding the DATA IN signal  140  to data input connectors of OLED tiles  118   a,    118   b,    118   c.  These bi-directional links also make it possible to pass the data input signal DATA IN  140  from the end of one column to the beginning of the neighbouring column. It is likewise to be noted that the terms “row” and “column” are interchangeable, meaning that the data reclockers may distribute the DATA IN signal  140  to all OLED tiles  118  of one column of the OLED sub-display  116 .  
      A data input connector of an OLED tile  118  provides an electrical connection for receiving video data signals containing the current video frame information to be displayed on OLED tile  118  and for receiving control data signals from data reclocker  142 . Subsequently, the video and control data is transferred from one OLED tile  118  to the next OLED tile  118  along a same column if the DATA IN signal  140  was fed to all OLED tiles  118  of a row, or to the next OLED tile  118  along a same row if the DATA IN signal  140  was fed to all OLED tile assemblies of a column. Hereinafter, the situation of  FIG. 2A  is further described, i.e. the case in which the DATA IN signal  140  was fed to all OLED tiles  118  along a same row. For example with reference to  FIG. 2 , the video and control data is transferred from OLED tile  118   g  to OLED tile  118   d  via an electrical connection between data output connector  132  of OLED tile  118   g  and data input connector  130  of OLED tile  118   d,  then from OLED tile  118   d  to OLED tile  118   a  via an electrical connection between data output connector  132  of OLED tile  118   d  and data input connector  130  of OLED tile  118   a.  Likewise, the video and control data is transferred from OLED tile  118   h  to OLED tile  118   e  via an electrical connection between data output connector  132  of OLED tile  118   h  and data input connector  130  of OLED tile  118   e,  then from OLED tile  118   e  to OLED tile  118   b  via an electrical connection between data output connector  132  of OLED tile  118   e  and data input connector  130  of OLED tile  118   b.  Lastly, the video and control data is transferred from OLED tile  118   j  to OLED tile  118   f  via an electrical connection between data output connector  132  of OLED tile  118   j  and data input connector  130  of OLED tile  118   f,  then from OLED tile  118   f  to OLED tile  118   c  via an electrical connection between data output connector  132  of OLED tile  118   f  and data input connector  130  of OLED tile  118   c.  In each case, the video and control data is re-transmitted by the control board of each OLED tile  118 .  
      The multi-line method of power distribution is accomplished by AC power connections from one OLED tile  118  to the next OLED tile  118  along the same column or row as follows. A POWER INPUT signal  144   a  from a mains power supply (not shown) is supplied to OLED tile  118   g  via an electrical connection to power input connector  134  of OLED tile  118   g.  AC power is then transferred from OLED tile  118   g  to OLED tile  118   d  via an electrical connection between power output connector  136  of OLED tile  118   g  and power input connector  134  of OLED tile  118   d.  AC power is then subsequently also transferred from OLED tile  118   d  to OLED tile  118   a  via an electrical connection between power output connector  136  of OLED tile  118   d  and power input connector  134  of OLED tile  118   a.  Likewise, a POWER INPUT signal  144   b  from the mains power supply (not shown) is supplied to OLED tile  118   h  via an electrical connection to power input connector  134  of OLED tile  118 h. AC power is then transferred from OLED tile  118   h  to OLED tile  118   e  via an electrical connection between power output connector  136  of OLED tile  118   h  and power input connector  134  of OLED tile  118   e.  AC power is then transferred from OLED tile  118   e  to OLED tile  118   b  via an electrical connection between power output connector  136  of OLED tile  118   e  and power input connector  134  of OLED tile  118   b.  Lastly, a POWER INPUT signal  144   c  from the mains power supply (not shown) is supplied to OLED tile  118   j  via an electrical connection to power input connector  134  of OLED tile  118   j.  AC power is then transferred from OLED tile  118   j  to OLED tile  118   f  via an electrical connection between power output connector  136  of OLED tile  118   j  and power input connector  134  of OLED tile  118 f. AC power is then transferred from OLED tile  118   f  to OLED tile  118   c  via an electrical connection between power output connector  136  of OLED tile  118   f  and power input connector  134  of OLED tile  118   c.  The AC input voltage from a power input connector  134  is simply bussed directly to power output connector  136  of the OLED tile  118 . Equally to the distribution of the DATA IN signal  140  over the OLED tiles  118 , the power distribution may be performed either column-wise or row-wise. Power input connector  134  and power output connector  136  are conventional power connectors e.g. capable of handling up to 265 AC volts and 10 amps.  
      An alternative distribution method for signal and power distribution is a star distribution (not represented in the drawings). The wording star distribution refers to the fact that the distribution of data signals or power occurs from the centre to the edge of the tiled OLED display  116  or vice versa. In this distribution method, the signals are transferred by a data reclocker  142  to several central OLED tile assemblies  118 , each of them further transferring the data signals to tiles at further distance of the centre or the edge respectively of the tiled OLED display  116 . In this way, distribution of serial video data and control data is obtained between the OLED tile assemblies from the centre assemblies  118  of the OLED tile display  116  to the edge assemblies  118  or vice versa, so that all OLED tile assemblies  118  obtain their part of the serial video data and control data. If preferred, it is also possible to obtain serial video data and control data transfer from edge assemblies to centre assemblies, i.e. starting at some of the edge assemblies and transferring to neighbouring assemblies ending in or around the centre of the display, so that all OLED tile assemblies  118  obtain their part of the serial video data and control data. In similar way, it is possible to obtain this method of distribution, i.e. star distribution, for the power distribution.  
      A third distribution method of both serial video and control data and power is illustrated in  FIG. 2B . It shows a daisy-chain method of distribution for a tiled OLED display  116 . The tiled OLED display  116  is representative of an m by n array of OLED tile assemblies  118 . In this example, a 3×3 array is pictured. More specifically,  FIG. 2B  illustrates that tiled OLED display  116  includes, for example, OLED tile assemblies  118   a,    118   b,    118   c,    118   d,    118   e,    118   f,    118   g,    118   h,  and  118   j.  It is further illustrated that each OLED tile assembly  118  includes its associated data input connector  130 , data output connector  132 , power input connector  134 , and power output connector  136 .  
      The daisy-chain distribution method of signal distribution is described as follows. A DATA IN signal  140 , representative of serial video and control data, from a central processing unit (not shown) is supplied to an input of one OLED tile assembly  118 , i.e. in the example given to data input connector  130  of OLED tile assembly  118   g.  Subsequently, the serial video and control data is transferred from one OLED tile assembly  118  to a next, neighbouring OLED tile assembly  118 . For example and with reference to  FIG. 2B , the serial video and control data is transferred from OLED tile assembly  118   g  to OLED tile assembly  118   d  via an electrical connection between data output connector  132  of OLED tile assembly  118   g  and data input connector  130  of OLED tile assembly  118   d,  then from OLED tile assembly  118   d  to OLED tile assembly  118   a  via an electrical connection between data output connector  132  of OLED tile assembly  118   d  and data input connector  130  of OLED tile assembly  118   a.  The serial video and control data is then further transferred from OLED tile assembly  118   a  to OLED tile assembly  118   b,  via an electrical connection between data output connector  132  of OLED tile assembly  118   a  and data input connector  130  of OLED tile assembly  118   b.  In similar way, the serial video data and control data are subsequently transferred from OLED tile assembly  118   b  to OLED tile assembly  118   e,  from OLED tile assembly  118   e  to OLED tile assembly  118   h,  from OLED tile assembly  118   h  to OLED tile assembly  118   j,  from OLED tile assembly  118   j  to OLED tile assembly  118   f  and from OLED tile assembly  118   f  to OLED tile assembly  118   c.  In similar way, the daisy-chain method of power distribution is accomplished by AC power connections from one OLED tile assembly  118  to the next OLED tile assembly  118 .  
      Although the latter method does not allow parallel distribution of the serial video and control data, i.e. distributing of serial video and control data occurs subsequently to a neighbouring tile, it can allow parallel, i.e. simultaneous, processing by the different to OLED tile assemblies.  
      In  FIGS. 2A and 2B , the same distribution method is used to distribute the power and the data. There is however no need to use the same method for data and power distribution.  
      The communications link between digitizer  112  and OLED sub-displays  116  of display wall  114  may be via, for example, a fibre link, which is a digital fibre optic transmission system. The fibre link may cover very long distances and has a very high bandwidth. The fibre link may transmit not only the video signals but also communication signals to display wall  114 .  
      Using digitizer  112 , different video input signals can be combined or overlaid. Since several sources can be connected to digitizer  112  at the same time, it is also possible to display images from several sources at display wall  114  at the same time. These images can be displayed next to each other, or they can be overlaid. The way in which the images are displayed may be edited or changed by moving and scaling “windows” in any known way. A window represents an image from a source, e.g. a video signal, that is connected to digitizer  112 . It is possible to change the position of the area upon display wall  114  in which the image is displayed, which is known as “window moving”. It is also possible to change the size of the area in which the image will be displayed, which is known as “window scaling”. Display wall  114  is representative of any user-configurable, modular OLED display formed of a collection of sub-displays  116 . Display wall  114  is customizable to any size and dimension by adding or removing OLED sub-displays  116  to achieve the desired display structure.  FIG. 1  is illustrative of a sample configuration of display wall  114  that includes OLED sub-displays  116 . Furthermore, each OLED sub-display  116  may be configured differently from one another using various configurations of OLED tiles  118  and OLED modules  120  that are uniquely user-defined for any given application.  
      Additionally, display wall  114  is also maintainable and repairable due to its modularity. For example, an OLED module  120  that does not function properly or contains failed pixels may be replaced with another OLED module  120  by removing the non-functional OLED module  120  and inserting a new OLED module  120  into the backplane of the corresponding OLED tile  118 . Analogously, due to the modularity any OLED tile  118 , e.g. OLED tile  118   a,    118   b,    118   c,    118   d,    118   e,    118   f,    118   g,    118   h,  or  118   j  that does not function properly or contains failed OLED modules  120  or failed pixels may be replaced with another OLED tile  118  by removing the non-functional OLED tile  118  and inserting a new OLED tile  118  in the respective OLED sub-display  116 . By contrast, large contiguous display systems as known from the prior art must be replaced in their entirety when portions of the display malfunction or when pixels go dark. Therefore, a modular display such as display wall  114  provides a longer display life and has lower replacement costs than conventional large single-unit displays.  
      Each AEC  122  is a device comprising sensors to measure the ambient environment, such as a temperature sensor, a light sensor, and a humidity sensor for example. One or more AECs  122  are placed in close proximity to display wall  114  to measure environmental parameters during the operation of display wall  114 .  
      Display wall  114  of OLED display system  100  includes various levels of hardware. The highest hardware level comprises display wall  114  itself, which is formed of a plurality of sub-displays  116 ; the next lower level comprises OLED sub-displays  116 , which are formed of a plurality of OLED tiles  118 ; the next lower level comprises OLED tiles  118 , which are formed of a collection of OLED modules  120 ; and the lowest level comprises OLED modules  120 , which are formed of a collection of individual OLED devices or pixels. The overall control according to the present invention is designed to handle the operation and calibration of the various levels of hardware of display wall  114  using similar algorithms regardless of level. Local processing is available at the fairly low level of each OLED tile  118 ; thus, the overall control of OLED display system  100  according to the present invention is able to use a distributed processing method. The physical hardware implementation of OLED tiles  118  and the architecture of display wall  114  provide distributed processing that has as a result a less complex display hardware and software system, thereby avoiding the need for high-bandwidth calculations by a central processor, i.e. by system controller  110 . The overall control software is described with reference to  FIG. 3, 4  and  5 .  
      In an alternative embodiment, a plurality of OLED display systems  100  are networked via e.g. a conventional local area network (LAN), a wide area network (WAN), or Internet to a central processor upon which is loaded the system control software for handling all OLED display systems  100 . In this case, the function of system controller  110  of each OLED display system  100  is simply to provide a network connection to each respective digitizer  112  of the OLED display systems  100 .  
       FIG. 3  illustrates a functional block diagram of an OLED display software system  200  in accordance with the present invention. OLED display software system  200  includes a system software component  210 , a tile software component  212 , and a module software component  214 .  
      OLED display software system  200  provides the overall software control for a modular large-screen OLED display system such as OLED display system  100 . System software component  210  is representative of the top level of software control, tile software component  212  is representative of an intermediate level of software control, and module software component  214  is representative of a low level of software control. In operation, information is passed among all levels and specific operations are distributed accordingly under the control of system software component  210 . More specifically, and with reference to  FIG. 3 :  
      As the top-level controller, system software component  210  performs such tasks as: 
          1) determining the configuration of OLED display system  100  upon initialization,     2) detecting replacement of OLED tiles  118 ,     3) running adaptive calibration algorithms for OLED tiles  118 ,     4) managing the temperature control of OLED tiles  118 ,     5) running system diagnostics, and     6) running adaptive feature algorithms for OLED tiles  118 .        

      As the mid-level controller, tile software component  212  performs such tasks as: 
          1) running adaptive calibration algorithms for OLED modules  120 ,     2) managing the temperature control of OLED modules  120 ,     3) setting and storing factory settings, such as serial number and production date of OLED tiles  118 , and     4) running pre-charge control algorithms for OLED modules  120 .        

      As the low-level controller, module software component  214  performs such tasks as: 
          1) running adaptive calibration algorithms for individual OLED devices,     2) storing run-time, which is a function of ON time+temperature,     3) maintaining pre-charge control of individual OLED devices,     4) storing light and color values for individual OLED devices, and     5) setting and storing factory settings, such as serial number and production date, of OLED modules  120 .        

      In general, algorithms and functionality are basically the same at all levels of OLED display software system  200 . These algorithms and functions are executed by tile software component  212  and/or module software component  214 , but decisions or information gathering are typically performed at the top level of system software component  210  by passing values from one level to the next. Thus, a cluster of OLED devices, a cluster of OLED modules  120 , and a cluster of OLED tiles  118  are controlled in the same way via OLED display software system  200 .  
      For example, a uniform output across all OLED devices within a given OLED module  120  is ensured via the adaptive calibration, but that does not mean that a uniform output across all OLED modules  120  within a given OLED tile  118  is ensured. Subsequently, once OLED modules  120  are uniform within themselves, all OLED modules  120  outputs must further be made uniform with their neighbors within each OLED tile  118 . Likewise, once OLED tiles  118  are uniform within themselves, all OLED tiles  118  outputs must further be made uniform with their neighbors within each OLED sub-display  116  of display wall  114 . Using, for example, an adaptive calibration algorithm, the same algorithm may be run at all levels from the lowest to the highest as follows: 
          1) The adaptive calibration algorithm of module software component  214  reads and calibrates the OLED devices for each OLED module  120 . The x,y,Y light outputs and color coordinates are read for every OLED device. Each OLED module  120  is subsequently calibrated to optimal target OLED device x,y,Y coordinates. Values are then passed on to the next higher level, i.e., to tile software component  212 .     2) The adaptive calibration algorithm of tile software component  212  reads and calibrates every OLED module  120  for each OLED tile  118 . Each OLED tile  118  is subsequently calibrated to the optimal target OLED module  120  x,y,Y coordinates. Values are then passed on to the next higher level, i.e., to system software component  210 .     3) The adaptive calibration algorithm of system software component  210  reads and calibrates every OLED tile  118  for each OLED sub-display  116  of display wall  114 . Each OLED sub-display  116  is subsequently calibrated to optimal target OLED sub-display  116  x,y,Y coordinates of display wall  114 . In this way, a uniform image is ensured throughout the entire display wall  114 .        

      In the above described methods, setting the emissive devices may comprise setting the emissive devices so that they are within 10%, preferably within 5% more preferably within 0.8% of the first level target value. Furthermore setting the first level modules may comprise setting the first level modules so that they are within 10%, preferably within 5% more preferably within 0.8% of the emissive display target value of that emissive display or within 10%, preferably within 5% more preferably within 0.8% of a second level target value, depending on the number of control levels that are used in the method of controlling.  
      In a similar way, depending on the number of control levels, setting the second level tiles may comprise setting the second level tiles so that they are within 10%, preferably within 5% and most preferably within 0.8% of the emissive display target value of the emissive display or within 10%, preferably within 5% and most preferably within 0.8% of a third level target value.  
      If further levels are present, setting the further levels may be so that they are within 10%, more preferably within 5% and most preferably within 0.8% of the emissive display target value of the emissive display.  
      In case of all the above limitations are target values, the actual target value that can be reached can depend on the parameter that is chosen as the target parameter, for example, 0.8% can be achieved for the parameter brightness. This would be a severe condition, for other parameters good target level values could be higher than 0.8%.  
      An aspect of OLED display software system  200  is that it takes the environment into account. For example, by using a light sensor and a temperature sensor, OLED display software system  200  can ascertain the specific purpose, i.e. the application, e.g. inside or outside projection, of a particular display wall  114 . Based upon this knowledge, the display content of the image, i.e. gamma, contrast, brightness, and lifetime, may be adapted.  
      More specifically, display deficiencies may be dealt with as a feature of OLED display software system  200 . For example, if the lifetime of a particular OLED technology is known to be limited to 10,000 hours, and a full white display image, such as a spreadsheet, is desired, the light output is less important than contrast. Thus, light output may be reduced to only 20% brightness while the contrast is increased by adapting the gamma curves, thereby providing a suitable image for this application. In this case, the OLED lifetime is approximately five times the lifetime of an OLED with no brightness adjustments at all. In adjusting brightness, lifetime optimization is achieved.  
      The nature of the video application, e.g. spreadsheet, movie, etc., can be detected for each OLED tile  118  because each OLED tile  118  receives the full video data stream. Each OLED tile  118  uses just its portion of the video data stream to calculate and keep track of its ON time. For example, for a full white display application, such as a spreadsheet, the average display content is typically greater than 40%, while for video, the average display content is typically less than 40%. Each OLED tile  118  tracks the data it is showing; thus, system software component  210  can request information from each OLED tile  118  concerning the percentage of content displayed, can calculate, based on the information for all OLED tiles  118 , whether the content is data or video, and can then issue commands to each OLED tile  118  to adapt its settings accordingly.  
      As a further example, in the case of a home theatre application used in a very dark environment, the human eye has a different sense of color impression. Thus, the saturation color points may be moved. Similarly, in the case of a movie application used in daylight, the eye is not very sensitive to low light. Thus, the lowlights need not necessarily be color accurate, allowing grayscale accuracy using e.g. only three colors, to be used in the lowlight region instead of exact color.  
      Each AEC  122  can be assigned a certain percentage of weight, dependent on its relevance, e.g. an AEC  122  positioned next to a light spot and extremely influenced by variances of light is weighted accordingly. A percentage of weight may also be assigned to each separate sensor of a particular AEC  122 , e.g. a sensor for temperature, light, humidity. In operation, a weighted average is calculated out of all the measurements and the software responds according to a certain reaction slope. The reaction slope determines the time of response to filter out peaks in light transmission.  
      From the top level, to the intermediate level, to the low level, i.e. system software component  210 , tile software component  212 , and module software component  214 , respectively, OLED display software system  200  is further described as follows.  
      System software component  210  is generally responsible for determining the configuration of display wall  114  upon initialization; detecting replacement of OLED tiles  118 ; performing adaptive calibration, diagnostics, and temperature control of OLED tiles  118 ; and running an adaptive feature algorithm. A more detailed discussion of these functional capabilities follows:  
      Configuration of display wall  114 , explained for the case where a daisy chain signal and power distribution is used Under the control of system software component  210 , a query of display wall  114  is performed by a simple electronic switch system. Upon system initialization, all switches are open. The first OLED tile  118  is detected and is addressed as OLED tile  118  # 1 . Once OLED tile  118  # 1  is addressed, its switch closes automatically to close the link in the daisy chain to the next OLED tile  118 . Now the second OLED tile  118  is detected and addressed as OLED tile  118  # 2 , its switch closes to complete the daisy chain to the next OLED tile  118 , and so on until all OLED tiles  118  are detected and addressed. Any information that is needed at run time is extracted during the detection process, for example, the system configuration, diagnostic information, and hardware version. Other parameters queried are, for example, resolution, run time, ID or serial number, diagnostics such as temperature and power supply voltages, software version of each OLED tile  118 , factory measurement system used, and production date. OLED display software system  200  according to an embodiment of the present invention allows the flexibility of hardware of different generations to operate together. A software upgrade or downgrade on OLED tiles  118  may be necessary to ensure that each OLED tile  118  has the same software ID. For example, for compatibility, a generation (x+1) OLED tile  118  might have to operate as an older generation (x) OLED tile  118 .  
      Replacement of OLED tiles  118 : Each OLED tile  118  has an associated serial number. By reading the serial number of each OLED tile  118 , system software component  210  uniquely detects and identifies each OLED tile  118 . According to one embodiment, system software component  210  performs continuous polling, i.e., every few seconds, to detect a replacement OLED tile  118 . Alternatively, an interrupt may be generated by the action of replacing an OLED tile  118 . System software component  210  may also detect which OLED tiles  118  are operational or which may be in the process of being replaced during operation, i.e. those being hot-swapped. System software component  210  detects which OLED tile  118  is swapped. System software component  210  is able to read and store the resolution, the content, the light output, and the compensation level of the OLED tile  118  being replaced. As a result, the replacement OLED tile  118  is updated within seconds by means of the layering of the software.  
      Adaptive calibration algorithm of OLED tiles  118 : A distinction between the “initial calibration” that is performed before display wall  114  leaves the factory, and the “periodic calibration” that is performed every time period T is as follows: 
          Initial calibration: The brightness Y and color coordinates x, y of each OLED pixel are measured. Taking into account the target brightness and color coordinates the optimal result opt(x,y,Y), i.e. closest to the target, that can be realized with all or substantially all pixels in a module is determined. The same procedure is repeated for each OLED module  120 , within each OLED tile  118 , within each OLED sub-display  116  of display wall  114 .     This initial calibration is necessary since each OLED pixel will differ with respect to color coordinates and luminance, due to fluctuations in the production process, driver properties, power supply and/or temperature issues, etc. Without this initial calibration, there would be a non-uniform image when displaying one of the primary colors over OLED sub-display  116  or when displaying any color derived from the primary colors.     Periodic calibration: After every time period T, a periodic calibration is performed. This periodic calibration is based on the calculated ON time and current and temperature during that ON time, or based on the ON time and voltage changes across the OLEDs during that ON time and the temperature, the aging of each OLED pixel is determined. Digital/analog corrections are performed to compensate for the differential aging of the different OLED pixels within an OLED module  120 .     This periodic calibration is necessary to compensate for the aging that will be different for the different pixels, since the ON time and current during ON time will be different for each pixel. Without the periodic calibration, color and brightness non-uniformity&#39;s would arise during the lifetime of an initially calibrated OLED module  120 .        

      Temperature control of OLED tiles  118 : The temperature of each OLED tile  118  is monitored via an internal temperature sensor in each OLED tile  118 . Additionally, the environment temperature of the overall display wall  114  is known via the combined AECs  122 . For example, it is desirable to determine whether one specific area of display wall  114  is running hotter than the rest of display wall  114 , which is a possibility due to natural convection or, for example, because of the sun shining on that area. In such a case, some action may be needed, such as adjusting the light output of that area of display wall  114 .  
      Diagnostics: Various system health conditions are monitored at regular time intervals via system software component  210 . For example, system software component  210  monitors the availability of each OLED voltage within each OLED tile  118 , the internal heat of each OLED tile  118  to determine whether cooling fans are failing or operational, the operation of a local processor or local memory within each OLED tile  118 , and the operation of any device that is controlled via an RS232 connector or other communication protocol connector. Diagnostic information is available at all times, as OLED tiles  118  are constantly running diagnostics under the control of tile software component  212 , updating the diagnostic parameters and storing them locally. The parameters can then be read at any time by system software component  210  to determine whether any action is required. System software component  210  attempts to keep every OLED tile  118  of display wall  114  operating even if an error condition exists; display wall  114  is shut down only when necessary, thereby achieving a certain level of “fault” tolerance. For example, a failed local processor with a given OLED tile  118  does not mean that the display image is lost, it only means that the failed OLED tile  118  will not respond to further commands from system software component  210  or that certain algorithms will not run anymore. It is entirely possible for the failed OLED tile  118  to continue to run in its current state.  
      Adaptive feature algorithm of OLED tiles  118 :  
      Based on the environmental conditions measured by the AECs  122 , system software component  210  determines the intended application and adjusts the display brightness and/or gamma curves to obtain a better contrast and/or adjusts the fan speed, etc. System software component  210  also determines the content of the data stream. Based on the type of content the brightness or contrast can be adapted to gain video/data performance and to increase the lifetime of OLED tile  118 .  
      As previously stated, tile software component  212  is generally responsible for adaptive calibration algorithms and temperature control for OLED modules  120  as described above in regard to system software component  210 , setting and storing factory settings such as serial number and production date of OLED tiles  118 , or setting and storing of the window a given OLED tile  118  has to display. Furthermore, because the pre-charge operation depends on the normal working voltage across the OLED device and the capacitance of the OLED device, it is necessary to adapt the pre-charge time during the lifetime of the OLED tiles. The pre-charging is done in the current-source driver and can be adjusted by writing a value in the pre-charge time register of the current-source chip. Loading this register is done by tile software component  212 .  
      As previously stated, module software component  214  is generally responsible for running adaptive calibration algorithms for individual OLED devices as described above in regard to system software component  210 , storing run-time, i.e. a function of ON time plus temperature, maintaining pre-charge control of individual OLED devices, storing light and color values for individual OLED devices, and setting and storing factory settings such as serial number and production date for OLED modules  120 .  
      In summary, OLED display software system  200  of the present invention performs operations to initialize and configure OLED display system  100 , which includes addressing OLED tiles  118 , configuring OLED tiles  118  and controlling OLED tiles  118  for uniform image and proper image size. Furthermore, OLED display software system  200  of the present invention handles additional features, including: hot swap capability to replace failed OLED tiles  118  without having to shut down or to reset and recalibrate the entire display wall  114 ; a mechanism to detect a new OLED tile  118  and to automatically address the new OLED tile  118  so that it is automatically reconfigured to produce the same image rapidly; video features such as gamma curve, the color points, and brightness adjustments; high broadcast capability; and the ability to determine the video content based upon a known data stream, then to reduce or increase the light output based upon that video content in order to gain video/data performance and to maximize lifetime of the OLEDs. Lastly, OLED display software system  200  of the present invention is able to convert display deficiencies into features, i.e. to compensate for deficiencies to improve display image while hiding a particular deficiency. An example of such compensation includes predicting and optimizing lifetime; measuring light output and temperature to set up display wall  114  to perform adequately in that environment; and adjusting gamma curve, color points, and brightness as a function of the environment.  
      Additionally, display software system  200  controls digitizer  112 , thereby achieving a user-defined mixing/overlaying/switching of several video/RGB input sources.  
       FIG. 4  illustrates a flow diagram of a method  300  of operating a tiled OLED display using OLED display software system  200  in accordance with an embodiment of the invention. Method  300  uses OLED display system  100  of  FIG. 1  as an example display system. Furthermore, throughout the steps of method  300 , a graphical user interface (GUI) is referenced as the input/output device that facilitates the user interface; however, those skilled in the art will appreciate that other well-known interface methods, such as a command line interface, a touch screen interface, a voice-activated interface, or a menu-driven interface, may be used. Method  300  according to an embodiment of the present invention includes steps as detailed hereunder. It is to be noted that not all of those steps are required for the invention, but that some of them are optional.  
      Step  310 : Logging into System  
      In this step, using system controller  110 , a user logs into OLED display software system  200  of OLED display system  100  by entering a user ID and password via a GUI. Subsequently, OLED display software system  200  validates the entry, thereby granting a valid user access. Method  300  proceeds to step  312 .  
      Step  312 . Is Configuration Detected? 
      In this decision step, OLED display software system  200  interrogates a Configuration Manager of display wall  114  to determine whether a configuration associated with display wall  114  exists. If yes, method  300  proceeds to step  332 . If no, method  300  proceeds to step  314 .  
      Step  314 . Opening Auto-Detect User Interface  
      If a configuration associated with display wall  114  does not exist, in this step, OLED display software system  200  initiates an auto-detect process by presenting an “auto-detect” GUI to the user. Method  300  proceeds to step  316 .  
      Step  316 . Setting Up Communications  
      In this step, using the “auto-detect” GUI, the user initiates a communications setup operation. Furthermore, the user initiates a process to adjust the parameter values of the communication link between system controller  110  and digitizer  112 . For example, communication port setup operation involves the selection of a serial port number, baudrate, and online/offline status, which indicates whether the software commands have effect on the system being talked to by OLED display software system  200 . When ON-LINE all commands are sent and acted on, when OFF-LINE all commands are not sent to the system devices. Method  300  proceeds to step  318 .  
      Step  318 : Logging Updates  
      In this step, OLED display software system  200  logs and stores any changes made during step  316  within system controller  110 . Method  300  proceeds to step  320 .  
      Step  320 : Initiating Auto-Selection Operation  
      In this step, using the “auto-detect” GUI, the user initiates a “start auto-selection” operation. Method  300  proceeds to step  322 .  
      Step  322 : Detecting and Addressing Devices  
      In this step, OLED display software system  200  interrogates OLED display system  100  for the presence of all attached devices, i.e. digitizer  112 , display wall  114 , OLED sub-displays  116 , OLED tiles  118 , and AECs  122 . Subsequently, all devices are addressed in the order in which they are detected in the datalink. More specifically, system controller  110  e.g. detects the presence of the various devices by systematically opening and closing switches to detect the presence and location of each device within OLED display system  100 . System controller  110  subsequently assigns each device a unique address for use in steering content and communications data to each. Method  300  proceeds to step  324 .  
      Step  324 : Downloading and Displaying Tile Parameters  
      In this step, all parameters, such as type of connected devices, runtime, software-versions, and serial numbers, etc., of detected devices are downloaded to system controller  110 . Status information, such as, for example, type of devices, software-versions, and serial numbers, etc., is displayed to the user via a GUI during the downloading process. Icons of detected devices are made visible to the user via a GUI displaying an overview of OLED display system  100 . Method  300  proceeds to step  326 .  
      Step  326 : Is Detection Complete? 
      In this decision step, OLED display software system  200  determines whether the device detection process has been successfully completed by determining whether the number of detected devices corresponds with the expected number of devices, i.e. user gets information of detected devices on the GUI; user knows if none are missing, and whether the software is not able to download all parameters of all connected devices. Otherwise the detection cannot be completed successfully. If yes, method  300  proceeds to step  334 . If no, method  300  returns to step  320 .  
      Step  332 : Is Configuration Complete? 
      In this decision step, OLED display software system  200  determines whether the configuration of display wall  114  is complete. When the configuration is known and the wall positioning is already entered, the configuration is considered as complete. Thus, OLED display software system  200  simply checks whether the wall positioning is already known or not. If yes, method  300  proceeds to step  374 . If no, method  300  proceeds to step  334 .  
      Step  334 : Initiating Wall Positioning Operation  
      This step is also carried out when previously a configuration associated with display wall  114  did not exist, and has been detected in the mean time. In this step, using a GUI displayed upon system controller  110 , the user initiates a “wall positioning” process for positioning display wall  114  in the total video output field. Subsequently, OLED display software system  200  initiates the wall positioning process for display wall  114  by presenting a “wall positioning” GUI to the user. Method  300  proceeds to step  336 .  
      Step  336 : Entering Wall Positioning Parameters  
      In this step, using the “wall positioning” GUI, the user enters pixel coordinates of the upper left corner of display wall  114 , resolution of OLED tiles  118 , linkage direction, etc. Subsequently, OLED display software system  200  logs and stores the window parameters, i.e. horizontal and vertical start- and stop-pixel coordinate, of each OLED tile  118  within the system controller  110 . Method  300  proceeds to step  338 .  
      Step  338 : Initiate System Configuration? 
      In this decision step, the user decides whether he/she wishes to initiate a system configuration process. If yes, method  300  proceeds to step  340 . If no, method  300  proceeds to step  362 .  
      Step  340 : Initiating System Configuration  
      In this step, using a GUI displayed upon system controller  110 , the user initiates a system configuration process for configuring all OLED sub-displays  116  and OLED tiles  118  of display wall  114 . Subsequently, OLED display software system  200  initiates the system configuration process for display wall  114  by presenting a “system configuration” GUI to the user. Method  300  proceeds to step  342 .  
      Step  342 : Displaying Connected Sources  
      In this step, OLED display software system  200  initiates the windowing process in digitizer  112  by presenting a “windowing” GUI to the user, through which all video sources connected via digitizer  112  are visibly displayed to the user with relation to display wall  114 . Method  300  proceeds to step  344 .  
      Step  344 : Configure System as a Whole? 
      In this decision step, the user decides whether he or she wishes to configure OLED display system  100  in its entirety. If yes, method  300  proceeds to step  350 . If no, method  300  proceeds to step  346 .  
      Step  346 : Selecting Device to be Configured  
      In this step, using a GUI displayed upon system controller  110 , the user selects digitizer  112 , display wall  114 , the connection between the display wall  114  and the digitizer  112 , e.g. a Fiberlink, i.e. a fiber-interface to connect display wall  114  to digitizer  112  at a long distance, or an AEC  122  to be configured. If digitizer  112  is selected, the user initiates actions relating to digitizer  112 , such as adjusting digitizer settings, adjusting timings of the sync generator, selecting input slots, etc. If display wall  114  is selected, the user initiates actions relating to display wall  114 , such as adjusting type, adjusting measurement system, adjusting contrast, adjusting flicker, adjusting mode, adjusting resolution mode, adjusting gamma, adjusting wall positioning, adjusting OLED tiles  118 , etc. If the connection, e.g. Fiberlink, is selected, the user initiates actions relating to the connection, such as adjusting status, type, motion of the transmitter and the receiver, adjusting the settings of a reconstruction filter, etc. If an AEC  122  is selected, the user initiates actions relating to the given AEC  122 , such as adjusting its settings, e.g. weight, calibration value and status of sensors. After the selected device has been configured, method  300  returns to step  340 .  
      Step  350 : Create New Configuration? 
      In this decision step, the user decides whether he/she wishes to create a new configuration for OLED display system  100 . If yes, method  300  proceeds to step  352 . If no, method  300  proceeds to step  372 .  
      Step  352 : Changing Windows  
      In this step, using the “windowing” GUI, the user makes any desired changes relating to the connected video sources with regard to the locations where their images are displayed, i.e. windows. For example, the user may choose one or more of the following operations: move windows, scale windows, adjust Z-order or layering scheme of the windows in relation to one another, adjust aspect ratio, select input, select special source-specific actions, e.g. visible, color key, alpha blending, etc., or change a selection of the image ViewPort. ViewPort refers to a positional point on the input image with X and Y coordinates and its associated horizontal distance W and vertical distance H, so it defines a ViewPort or cutout image specific to that input. The ViewPort can be changed by changing the values of X, Y, W, H. Method  300  proceeds to step  354 .  
      Step  354 : Adjusting Workspace Resolution  
      In this step, using a GUI displayed upon system controller  110 , the user adjusts the size of the resolution of the work area. The user may adjust the size of the workspace resolution by either zooming in or out of the window and display boxes. The width and height aspect ratio change simultaneously according the adjustments, e.g., an 800×600 resolution can be converted to 520×390 in the workspace area. Method  300  proceeds to step  356 .  
      Step  356 : Adjusting Wall Positioning  
      In this decision step, using the “wall positioning” GUI displayed upon system controller  110 , the user adjusts the wall positioning of display wall  114 . It is possible to adjust the horizontal and vertical start positions of the display in the work area. It is also possible to adjust the horizontal and vertical resolution of every display tile. Changes can be made from the tile&#39;s maximum displayable resolution to values below that maximum. This is quite useful when trying to fill extremely large walls with small source images, as reducing the resolution per tile expands the image. Method  300  proceeds to step  358 .  
      Step  358 : Adjusting Wall Settings  
      In this step, using the “wall settings” GUI displayed upon system controller  110 , the user adjusts the settings of display wall  114 , such as contrast, flicker, and gamma. Method  300  proceeds to step  360 .  
      Step  360 : Adjusting and Saving Configuration  
      In this step, using a GUI displayed upon system controller  110 , the user initiates a configuration management operation for display wall  114 . The user may save the setup of display wall  114  in configuration files, which contain all the settings of OLED display system  100 . The user may save or recall as many configurations as requested. By downloading a configuration to display wall  114 , all the settings, such as positioning, flicker, and contrast, are updated immediately. Method  300  returns to step  350 .  
      Step  362 . Maintenance Operation? 
      In this decision step, the user decides whether he or she wishes to initiate a maintenance operation upon OLED display system  100 . If yes, method  300  proceeds to step  364 . If no, method  300  proceeds to step  374 .  
      Step  364 : Selecting Maintenance Operation  
      In this step, using a GUI displayed upon system controller  110 , the user initiates the maintenance operation, such as for example a software/firmware update for all connected devices or a color calibration adjustment, for OLED display system  100 . Subsequently, OLED display software system  200  initiates the maintenance operation for OLED display system  100  by presenting a “maintenance” GUI to the user. Method  300  proceeds to step  366 .  
      Step  366 : Perform Calibration? 
      In this decision step, the user decides whether he or she wishes to initiate a calibration operation upon OLED display system  100 . If yes, method  300  proceeds to step  368 . If no, method  300  proceeds to step  370 .  
      Step  368 : Performing Color Calibration  
      In this step, using the “maintenance” GUI displayed upon system controller  110 , the user defines the color temperature and selects the range of OLED tiles  118  to be calibrated. It is possible to calibrate the entire display wall  114  or to calibrate only a range of OLED tiles  118 . For example, calibrating only OLED tiles  118  with addresses ranging from 4 to 7. Subsequently, the user initiates a color calibration operation upon display wall  114  and OLED display software system  200  performs the color calibration operation upon the selected OLED tiles  118  of display wall  114 . The color calibration reads all color measurements, i.e. measurements done at the factory and stored in each OLED tile  118 , and aging factors of all OLED tiles  118 , and uses these to calculate correction values, which then are sent to OLED tiles  118 , resulting in a uniform image. Method  300  ends.  
      Step  370 : Performing Device Software Update  
      In this step, using a GUI displayed upon system controller  110 , the user initiates a device software update operation for OLED display system  100  and further selects the specific device to be updated. Subsequently, OLED display software system  200  initiates the device software update operation for OLED display system  100  by presenting an “update software” GUI to the user. The user then selects the update files and OLED display software system  200  performs the device software update operation. In this step it is possible to update the software/firmware of all the connected devices. Using a GUI displayed upon system controller  110 , the user selects the device icon for which the software has to be updated and places the update files in the appropriate directory. Method  300  ends.  
      Step  372 : Deleting or Loading Configurations  
      In this step, using the “configuration manager” GUI displayed upon system controller  110 , the user either deletes or loads configurations relating to OLED display system  100 . In step  360 , the defined configuration was saved. In the same way it is possible that configurations have been saved during previous display configurations. These older configurations may now be loaded or they can be deleted. Method  300  proceeds to step  374 .  
      Step  374 : Proceeding to Monitoring Operation  
      In this step, using a GUI displayed upon system controller  110 , the user initiates a system monitoring operation for OLED display system  100 . Subsequently, OLED display software system  200  initiates the system monitoring operation for OLED display system  100  by presenting a “monitoring” GUI to the user. Full details of the system monitoring operation are found in reference to a method  400  of  FIG. 5 ; however, a summary of the system monitoring operation is provided as follows.  
      Using the “monitoring” GUI displayed upon system controller  110 , the user views the settings for AECs  122 . The user may perform the following tasks: 
          adjust various settings, e.g., the minimum/maximum contrast, the ambient temperature range, the ambient illumination range, the reaction slope, and the interval;     adjust settings for AECs  122 , e.g., the weight and status of each AEC  122 ;     adjust the application for OLED display system  100 , e.g., home theatre, control rooms, and events; or     start or stop the system monitoring operation.        

      OLED display software system  200  of OLED display system  100  periodically, i.e. the period is determined by a specified interval, reads the temperature, content, ambient illumination, aging, and relative humidity relating to display wall  114 . OLED display software system  200  performs adjustment depending on the parameter values. Method  300  ends.  
       FIG. 5  illustrate a flow diagram of a method  400  of monitoring a tiled OLED display using OLED display software system  200  in accordance with an embodiment of the invention. Method  400  uses OLED display system  100  of  FIG. 1  as an example display system. Generally, the software control system of OLED display system  100  periodically reads the temperature, content, ambient illumination, aging, and relative humidity relating to display wall  114 , and then performs adjustments depending on the parameter values according to method  400 .  
      Furthermore, throughout the steps of method  400 , a GUI is referenced as the input/output device that facilitates the user interface; however, those skilled in the art will appreciate that other well-known interface methods, such as a command line interface, a touch screen interface, a voice-activated interface, or a menu-driven interface, may be used. Method  400  includes the following steps:  
      Step  410 : Initiating Monitoring Operation  
      In this step, using a GUI displayed upon system controller  110 , the user initiates a system monitoring operation for OLED display system  100 . Subsequently, OLED display software system  200  initiates the system monitoring operation by presenting a “monitoring” GUI to the user, who defines a time period T for monitoring OLED display system  100 . Method  400  proceeds to step  412 .  
      Step  412 : Is Time=n*T? 
      In this decision step, OLED display software system  200  determines whether a predetermined time interval n*T has elapsed since the last system monitoring operation was performed; where n is an integer number: n=1, 2, 3, and where T is a predefined period of time. The monitoring actions will be performed every time that a time period T has elapsed. If yes, method  400  proceeds to step  416 . If no, method  400  proceeds to step  414 .  
      Step  414 : Indexing Time Period  
      In this step, OLED display software system  200  indexes the time period by, for example, five minutes. Method  400  returns to step  412 .  
      Step  416 : Reading Aging-Related Parameters  
      In this step, OLED display software system  200  reads aging-related parameters, such as ON time, current during ON time, voltage across the OLED, temperature, color measurements, from a local storage of each OLED tile  118 . Method  400  proceeds to step  418 .  
      Step  418 : Calculating Aging of Each Sub-Pixel  
      In this step, OLED display software system  200  calculates the aging of each red, green, and blue sub-pixel within each pixel of each OLED module  120  of each OLED tile  118  of each OLED sub-display  116  of display wall  114 . The comparison of the initial voltage across the OLED device and measured voltage across the OLED device is an indication for the aging of the OLED device. The ON time and current during the ON time allows calculating the total charge that passed through the OLED device. This total charge is also a measure for the aging of the OLED devices. Also the temperature, measured on regular basis, has an influence on the aging. Method  400  proceeds to step  420 .  
      Step  420 : Is Aging&gt;Predefined Percentage? 
      In this decision step, OLED display software system  200  determines whether the aging calculated in step  418  is greater than a predefined percentage for any given sub-pixel. If yes, method  400  proceeds to step  422 . If no, method  400  proceeds to step  424 .  
      Step  422 : Running Calibration Software  
      In this step, OLED display software system  200  performs a calibration operation upon the target sub-pixel(s). More specifically, after every time period T, a periodic calibration is performed. The calibration is based on the aging of each OLED. This aging of each OLED is determined based on the calculated ON time and current and temperature during that ON time or based on the ON time and voltage changes across the OLEDs and the temperature during that ON time. Digital/analog corrections are performed to compensate for the differential aging of the different OLED pixels within an OLED module  120 . This periodic calibration is necessary to compensate for the aging that will be different for the different pixels, since the ON time and current during ON time will be different for each pixel. Without the periodic calibration color and brightness non-uniformities would arise during the lifetime of an initially calibrated OLED module  120 . Method  400  proceeds to step  424 .  
      Step  424 : Reading Ambient Illumination(s) from AEC(s)  
      In this step, OLED display software system  200  reads the ambient illumination(s) from AECs  122  mounted within display wall  114 . The measured ambient illumination level is used in steps  432  and  440  to allow making appropriate gamma/brightness changes in order to optimize the display performance. Method  400  proceeds to step  426 .  
      Step  426 : Calculating Weighted Average  
      In this step, OLED display software system  200  calculates the weighted average of the ambient illumination levels measured by the various light sensors of the various AECs  122  by taking into account the weight of each AEC  122  and the weight of each light sensor within each AEC  122 . For example, assume that two AECs  122  are placed next to display wall  114 , assume that the first AEC  122  has a weight of X% and the second AEC  122  has a weight of Y%, e.g. it is possible that X is much smaller than Y if the first AEC  122  is positioned next to a light spot, and assume that each AEC  122  has four light sensors, with the following measured values and weights:  
                                                   Value (lux)   Weight (%)                                                            First AEC 122   Sensor 1a   a1   Wa1               Sensor 1b   b1   Wb1               Sensor 1c   c1   Wc1               Sensor 1d   d1   Wd1           Second AEC 122   Sensor 2a   a2   Wa2               Sensor 2b   b2   Wb2               Sensor 2c   c2   Wc2               Sensor 2d   d2   Wd2                      
 
      The weighted average can than be calculated as:  
       WeightedAverage   =               X   ⁢           ⁢     %   ·         a1   ·   Wa1     +     b1   ·   Wb1     +     c1   ·   Wc1     +     d1   ·   Wd1       4         +               Y   ⁢           ⁢     %   ·         a2   ·   Wa2     +     b2   ·   Wb2     +     c2   ·   Wc2     +     d2   ·   Wd2       4               2         
 
      Method  400  proceeds to step  428 .  
      Step  428 : Reading Content  
      In this step, OLED display software system  200  reads the content type of the displayed video from the input data stream for determining the nature of the application. Method  400  proceeds to step  430 .  
      Step  430 : Is Content Almost “Spreadsheet”? 
      In this decision step, by analyzing the content read in step  428 , OLED display software system  200  determines whether the content is almost “spreadsheet”, i.e. is nearly a full white image. If full white operations are represented by a “power factor =1” and video operation can be represented by a “power factor=⅛=0.125”, nearly a full white image refers to an image having a power factor equal to or larger than 0.56. If yes, method  400  proceeds to step  432 . If no, method  400  proceeds to step  440 .  
      Step  432 : Is Ambient Illumination&lt;Predefined Value? 
      In this decision step, by analyzing the ambient illumination(s) read in step  424 , OLED display software system  200  determines whether the ambient illumination is less than a  20  predefined value of, for example,  200  lux. If yes, method  400  proceeds to step  436 . If no, method  400  proceeds to step  434 .  
      Step  434 : Adapting Gamma to Obtain Appropriate Contrast  
      In this step, OLED display software system  200  runs algorithms to adapt the gamma curve of each OLED module  120  to obtain appropriate contrast by selecting another gamma preset curve or by changing one or more of ten points that define the current gamma curve. The gamma value is a curve defined by ten points, i.e. one starting slope point, one ending slope point and four x, y coordinate points in between and is used to convert the 8-bit digitized RGB data into a 16-bit value. In this way 256 different input values can be transformed to 65536 output values; a linear input can be converted to any non-linear output which corresponds better with the human eye sensitivity. This output is used by CCD controller to control the ON time of the current sources. An appropriate choice of the gamma curves allows to improve the display performance, e.g. to improve the contrast in the high-lights. There are several gamma preset curves to choose from. It is also possible to construct another gamma by moving one or more of the four pairs that define the gamma curve. Method  400  proceeds to step  452 .  
      Step  436 : Reducing Overall Brightness  
      In this step, if the ambient illumination is less than a predetermined value, OLED display software system  200  reduces the overall brightness of display wall  114  by reducing the brightness of each primary emitter by the same percentage. The purpose of this operation is to increase the lifetime of display wall  114 , and to prevent display wall  114  from emitting too much light in a dark environment. For example, at night, watching a very bright display wall  114  is not comfortable to the eye for viewing. Each color in display wall  114  can be described by its tristimulus values X, Y, Z in the CIE color space. The Y value represents contributions to the brightness perception of the human eye and it is called the brightness or luminance. A color can also be described by Y and the color functions x, y, z; where  
         x   =     X     X   +   Y   +   Z         ,     y   =     Y     X   +   Y   +   Z         ,     z   =     Z     X   +   Y   +   Z         ,       
 
 and x+y+z=1. 
 
 In this step the brightness of each primary color Y R , Y B , and Y G  is decreased by a percentage factor, for example 10%. The overall brightness of display wall  114  will therefore decrease by the same percentage factor. Method  400  proceeds to step  438 . 
 
      Step  438 : Adapting Gamma for Contrast Increase  
      In this step, OLED display software system  200  runs algorithms to adapt the gamma curve of each OLED module  120  to obtain appropriate contrast by selecting another gamma preset curve or by changing one or more of a plurality of points, e.g. ten points, that define the current gamma curve. In this case a gamma curve is selected that gives rise to an increased contrast in a dark environment. Method  400  proceeds to step  452 .  
      Step  440 . Is Ambient Illumination&lt;Predefined Value? 
      In this decision step, carried out when the content read in step  428  is not nearly a full white image i.e. if the image has a power factor lower than 0.56, by analyzing the ambient illumination(s) read in step  424 , OLED display software system  200  determines whether the ambient illumination is less than a predefined value of, for example, 200 lux. If yes, method  400  proceeds to step  442 . If no, method  400  proceeds to step  446 .  
      Step  442 : Adapting Gamma for Lowlights  
      In this step, OLED display software system  200  runs algorithms to adapt the gamma curve of each OLED module  120  for improved display performance at lowlights by selecting another gamma curve. See step  434  for more details. Method  400  proceeds to step  444 .  
      Step  444 : Adapting Color Point for Night Vision  
      In this step, OLED display software system  200  runs algorithms to adapt the color point of each OLED module  120  for night vision. In a dark environment, the color impression is different. Therefore, the saturation color point needs to be moved to improve the color reproduction on display wall  114 . Method  400  proceeds to step  452 .  
      Step  446 : Increasing Brightness  
      In this step, carried out when the ambient illumination is not smaller than a predetermined value, OLED display software system  200  runs algorithms to increase the brightness of display wall  114  by increasing the brightness of each primary emitter by the same percentage. In this step the brightness of each primary color Y R , Y B , and Y G  is increased by a percentage factor, for example 10%. The overall display brightness will therefore increase by the same percentage factor. As a result of this action, the performance of display wall  114  will increase, but the lifetime of display wall  114  will decrease. Method  400  proceeds to step  448 .  
      Step  448 : Adapting Gamma  
      In this step, OLED display software system  200  runs algorithms to adapt the gamma curve of each OLED module  120  to increase the contrast by selecting another gamma curve. See step  434  for more details. Method  400  proceeds to step  450 . Step  450 : Generating Grayscales  
      In this step, OLED display software system  200  runs algorithms to generate grayscales of each pixel within each OLED module  120  within each OLED tile  118  within each OLED sub-display  116  of display wall  114  using e.g. the three primary colors of the pixels. The purpose of this operation is to increase the lifetime of display wall  114 . In a bright environment, display wall  114  does not have to be color accurate, but display wall  114  has to be grayscale accurate. As a consequence, the three colors can be used to generate the gray scales. Method  400  proceeds to step  452 .  
      Step  452 : Reading Temperature(s) from Tile(s)  
      In this step, OLED display software system  200  reads the temperature(s) from OLED tiles  118 . The temperature has a serious influence on the lifetime of OLED tiles  118 . It is a rule of thumb that the display lifetime decreases by a factor of two for every temperature raise of  10  ° C. The knowledge of the temperature allows appropriate actions to be taken to limit the aging of the OLED devices within OLED tiles  118 , as shown in steps  464 ,  466  and  468 . Method  400  proceeds to step  454 .  
      Step  454 : Calculating Weighted Average  
      In this step, OLED display software system  200  calculates the weighted average of the temperature measured in OLED tiles  118 . Method  400  proceeds to step  456 .  
      Step  456 : Is Temperature&gt;Predefined Max. Value? 
      In this decision step, by analyzing the weighted average temperature calculated in step  454 , OLED display software system  200  determines whether the temperature is larger than a predefined maximum value of, for example, 35° C. If yes, method  400  proceeds to step  464 . If no, method  400  proceeds to step  458 .  
      Step  458 : Is Temperature&lt;Predefined Min. Value? 
      In this decision step, by analyzing the weighted average temperature calculated in step  454 , OLED display software system  200  determines whether the temperature is less than a predefined minimum value of, for example, 25° C. If yes, method  400  proceeds to step  460 . If no, method  400  proceeds to step  470 .  
      Step  460 : Is Overall Brightness Level&lt;Predefined Min. Value? 
      In this decision step, by analyzing the brightness of display wall  114 , OLED display software system  200  determines whether the overall brightness level of display wall  114  is less than a predefined minimum value of, for example, 100 nit. If yes, method  400  proceeds to step  462 . If no, method  400  proceeds to step  470 .  
      Step  462 : Checking Application and Making Adjustment  
      In this step, OLED display software system  200  verifies the application in which display wall  114  is being used and makes adjustments. For example, in a home theatre application in a bright environment the brightness of display wall  114  may be increased in order to increase the performance. Example applications include home theatre, control rooms, events, etc. Method  400  proceeds to step  470 .  
      Step  464 : Is Fan Speed Maximum? 
      In this decision step, OLED display software system  200  determines whether cooling fans within each OLED tile  118  are operating at its maximum speed by checking the voltage used to drive the cooling fans. If yes, method  400  proceeds to step  468 . If no, method  400  proceeds to step  466 .  
      Step  466 : Increasing Fan Speed  
      In this step, OLED display software system  200  issues commands to increase the operating speed of cooling fans within one or more targeted OLED tiles  118 . It is to be noted that adjusting of the fan-speed is normally done independently within each OLED tile  118  without control of system controller  110 . Method  400  proceeds to step  470 .  
      Step  468 : Reducing Overall Brightness  
      In this step, OLED display software system  200  reduces the overall brightness of display wall  114  by reducing the brightness of each primary emitter by the same percentage. The purpose of this operation is to increase the lifetime of display wall  114 . In this step the brightness of each primary color Y R , Y B , and Y G  is decreased by, for example, 10%. The overall brightness of display wall  114  will therefore decrease by the same percentage. Method  400  proceeds to step  470 .  
      Step  470 : Reading Relative Humidity from AEC(s)  
      In this step, OLED display software system  200  reads the relative humidity from AECs  122  mounted within display wall  114 . In an environment with a high relative humidity the lifetime of the OLED devices will be shorter than the lifetime of OLED devices in an environment with a very low relative humidity. The knowledge of the relative humidity allows the appropriate actions to be taken in order to increase the lifetime of display wall  114 , such as in case of very high relative humidity; and to improve the performance of display wall  114  in the case of a very low relative humidity. Method  400  proceeds to step  472 .  
      Step  472 : Calculating Weighted Average  
      In this step, OLED display software system  200  calculates the weighted average of the relative humidity measured by the different humidity sensors of the different AECs  122  by taking into account the weight of each AEC  122  and the weight of each humidity sensor within each AEC  122 . The calculation is analogous to the calculation described in step  426 , apart from the fact that the a 1 , b 1 , c 1 , d 1 , a 2 , b 2 , c 2  and d 2  are now the relative humidity values in %. Method  400  proceeds to step  474 .  
      Step  474 : Is Relative Humidity&gt;Predefined Max. Value? 
      In this decision step, by analyzing the weighted average relative humidity calculated in step  472 , OLED display software system  200  determines whether the relative humidity is greater than a predefined maximum value of, for example, 80%. If yes, method  400  proceeds to step  478 . If no, method  400  proceeds to step  476 .  
      Step  476 : Is Relative Humidity&lt;Predefined Minimum Value? 
      In this decision step, by analyzing the weighted average relative humidity calculated in step  472 , OLED display software system  200  determines whether the relative humidity is less than a predefined minimum value of, for example, 20%. If yes, method  400  proceeds to step  478 . If no, method  400  returns to step  412 .  
      Step  478 : Checking Application and Making Adjustment  
      In this step, OLED display software system  200  verifies the application in which display wall  114  is being used and makes adjustments, such as increasing the brightness if relative humidity is very low and if this is useful for the application. If the relative humidity is very high, actions will be taken to reduce the aging of the OLED devices, e.g. by decreasing the overall brightness. If the relative humidity is very low, actions will be taken to increase the performance of display wall  114 , e.g. increase brightness or do nothing but just benefit from the reduced aging due to the low humidity. Example applications include home theatre, control rooms, events, etc. Method  400  returns to step  412 .