Method for operating and individually controlling the luminance of each pixel in an emissive active-matrix display device

Abstract

System and method for controlling luminance of pixel in display. Method includes storing transformation between digital image gray level value and display drive signal that generates luminance from pixel corresponding to digital gray level value; identifying target gray level value for particular pixel; generating display drive signal corresponding to identified target gray level based on stored transformation and driving particular pixel with drive signal during first display frame; measuring parameter representative of actual measured luminance of particular pixel at a second time after the first time; determining difference between identified target luminance and actual measured luminance; modifying stored transformation for particular pixel based on determined difference; and storing and using modified transformation for generating display drive signal for particular pixel during frame time following first frame time. Control system and circuits for controlling the luminance of a picture element or pixel in a display device.

1 . A method for controlling the luminance of a picture element (pixel) in a display device, the method comprising: 
 storing a transformation between a digital image gray level value and a display drive signal that generates a luminance from a pixel corresponding to the digital gray level value;    identifying a target gray level value for a particular pixel;    generating a display drive signal corresponding to the identified target gray level based on the stored transformation and driving the particular pixel with the drive signal during a first display frame;    measuring a parameter representative of an actual measured luminance of the particular pixel at a time after the first display time;    determining a difference between the identified target luminance and the actual measured luminance for the particular pixel;    modifying the stored transformation for the particular pixel based on the determined difference; and    storing and using the modified transformation for generating the display drive signal for the particular pixel during a frame time following the first frame time.    
     
     
         2 . A method as in  claim 1 , wherein the first display frame is any display frame designated by software programming or by the display user or by a combination of the programming and the user.  
     
     
         3 . A method as in  claim 1 , wherein the frame time following the first frame is any subsequent frame time.  
     
     
         4 . A method as in  claim 1 , wherein the first display frame is any display frame designated by software programming or by the display user or by a combination of the programming and the user.  
     
     
         5 . A method as in  claim 1 , wherein the first display time may be either a single continuous period of time or comprised of a plurality of discontinuous periods of time, and wherein either of the continuous period of time and the discontinuous periods of time may occur during a single frame time or over multiple frame times.  
     
     
         6 . A method as in  claim 1 , wherein storing and/or the using of the modified transformation for generating the display drive signal for the particular pixel is applied at any subsequent portion of a single frame or at different frames.  
     
     
         7 . A method as in  claim 1 , wherein storing and/or the using of the modified transformation for generating the display drive signal for the particular pixel may be either at single continuous period of time or comprised of a plurality of discontinuous periods of time, and wherein either of the continuous period of time and the discontinuous periods of time may occur during a single frame time or over multiple frame times.  
     
     
         8 . A method as in  claim 5 , wherein storing and/or the using of the modified transformation for generating the display drive signal for the particular pixel may be either at single continuous period of time or comprised of a plurality of discontinuous periods of time, and wherein either of the continuous period of time and the discontinuous periods of time may occur during a single frame time or over multiple frame times.  
     
     
         9 . A method as in  claim 1 , wherein the stored transformation comprises a transformation stored in a gray level logic functional block of a display system.  
     
     
         10 . A method as in  claim 1 , wherein the stored transformation comprises a transformation stored in a gamma table for a display device.  
     
     
         11 . A method as in  claim 1 , wherein the measured parameter representative of an actual measured luminance of the particular pixel at the end of the first display time comprises a voltage measurement corresponding to a number of electrons accumulated or released from a charge storage device.  
     
     
         12 . A method as in  claim 1 , wherein the measured parameter representative of an actual measured luminance of the particular pixel at the end of the first display time comprises a current measurement corresponding to a number of electrons accumulated or released from a charge storage device.  
     
     
         13 . A method as in  claim 1 , wherein the measured parameter representative of an actual measured luminance of the particular pixel at the end of the first display time comprises a charge measurement corresponding to a number of electrons accumulated or released from a charge storage device.  
     
     
         14 . A method as in  claim 11 , wherein the charge storage device comprises a capacitor.  
     
     
         15 . A method as in  claim 14 , wherein the electrons are accumulated or released in proportion to a resistivity or conductivity of a sensor element having a resistivity or conductivity that changes in response to a flux of photons incident on the sensor.  
     
     
         16 . A method as in  claim 15 , wherein the proportion is a direct proportion.  
     
     
         17 . A method as in  claim 1 , wherein the frame time following the first frame time is the next subsequent frame time.  
     
     
         18 . A method as in  claim 1 , wherein the frame time following the first frame time is any subsequent frame time.  
     
     
         19 . A method as in  claim 1 , wherein the frame time following the first frame time is a next display device power on time.  
     
     
         20 . A method as in  claim 1 , wherein the frame time following the first frame time is a frame time at a predetermined or dynamically determined time interval.  
     
     
         21 . A method as in  claim 1 , wherein a different transformation is stored for each pixel in the display device.  
     
     
         22 . A method as in  claim 1 , wherein a different transformation is stored for each different gray level that may be displayed for each separately addressable pixel in the display device.  
     
     
         23 . A method as in  claim 1 , wherein the first display time is the duration of time a pixel is turned on in the display.  
     
     
         24 . A method as in  claim 1 , wherein the display time is substantially any time between 8 milliseconds and 36 milliseconds.  
     
     
         25 . A method as in  claim 1 , wherein the display time is substantially any time between 10 milliseconds and 20 milliseconds.  
     
     
         26 . A method as in  claim 1 , wherein the portion of the frame time comprises substantially the row address time.  
     
     
         27 . A method as in  claim 1 , wherein the portion of the frame time comprises a time between the row address time and the frame time.  
     
     
         28 . A method as in  claim 1 , wherein the measuring of a parameter representative of an actual measured luminance of the particular pixel at the end of the first display time comprises measuring a voltage stored on a capacitor that has either been charged toward or discharged from a known voltage and the amount of charging or discharging is proportional to a photon flux emitted from the emitter within the particular pixel onto a sensor within the same particular pixel.  
     
     
         29 . A method as in  claim 1 , wherein the steps of identifying, generating, measuring, determining, modifying, and using are repeated for every pixel in the display.  
     
     
         30 . A method as in  claim 1 , wherein the determining of a difference between the identified target luminance and the actual measured luminance for the particular pixel is based on a reference integrated photon flux on the particular pixel sensor determined during a display calibration procedure performed during manufacture or when initially used.  
     
     
         31 . A method as in  claim 1 , further comprising a display calibration procedure that determines and stores an initial transformation for every pixel and every gray level the display may be commanded to display.  
     
     
         32 . A control system for controlling the luminance of a picture element (pixel) in a display device, the system comprising: 
 a stored pixel gray level to display pixel drive signal transformation for each pixel and each gray level the pixel may be commanded to display, the stored transformation based on performance characteristics of the display pixels during a prior display frame time period;    a display drive signal generator responsive to a control that receives a command to display a particular gray level for a particular pixel location and generates a drive signal to the particular pixel using the stored transformation during a first frame time;    a luminance measurement circuit for each separate pixel in the display for measuring parameters representative of an actual measured luminances of each of the plurality of particular pixels at the end of the first display time;    a comparator circuit for determining a difference between the identified target luminance and the actual measured luminance for the particular pixel;    transformation update logic for modifying the stored transformation for each particular pixel based on the determined difference during the first frame time; and    using the modified transformation for generating the display drive signal for the particular pixel during a frame time following the first frame time.    
     
     
         33 . A system as in  claim 32 , wherein the stored transformation comprises a transformation stored in a gray level logic functional block of a display system.  
     
     
         34 . A system as in  claim 32 , wherein the stored transformation comprises a transformation stored in a gamma table for a display device.  
     
     
         35 . A system as in  claim 32 , wherein the luminance measurement circuit measures a parameter representative of an actual measured luminance of the particular pixel at the end of the first display time and comprises a voltage measurement corresponding to a number of electrons accumulated or released from a charge storage device separately for each pixel of the display.  
     
     
         36 . A system as in  claim 35 , wherein the charge storage device comprises a capacitor.  
     
     
         37 . A system as in  claim 36 , wherein the electrons are accumulated or released in proportion to a resistivity or conductivity of a sensor element having a resistivity or conductivity that changes in response to a flux of photons incident on the sensor.  
     
     
         38 . A system as in  claim 37 , wherein the proportion is a direct proportion.  
     
     
         39 . A system as in  claim 32 , wherein the frame time following the first frame time is the next subsequent frame time.  
     
     
         40 . A system as in  claim 32 , wherein the frame time following the first frame time is any subsequent frame time.  
     
     
         41 . A system as in  claim 32 , wherein the frame time following the first frame time is a next display device power on time.  
     
     
         42 . A system as in  claim 32 , wherein the frame time following the first frame time is a frame time at a predetermined or dynamically determined time interval.  
     
     
         43 . A system as in  claim 32 , wherein different transformation is stored for each pixel in the display device.  
     
     
         44 . A system as in  claim 32 , wherein a different transformation is stored for each different gray level that may be displayed for each separately addressable pixel in the display device.  
     
     
         45 . A system as in  claim 32 , wherein the first display time is the duration of time a pixel is turned on in the display.  
     
     
         46 . A system as in  claim 32 , wherein the display time is substantially any time between 8 milliseconds and 36 milliseconds.  
     
     
         47 . A system as in  claim 32 , wherein the display time is substantially any time between 10 milliseconds and 20 milliseconds.  
     
     
         48 . A system as in  claim 32 , wherein the portion of the frame time comprises substantially the row address time.  
     
     
         48 . A system as in  claim 32 , wherein the portion of the frame time comprises a time between the row address time and the frame time.  
     
     
         50 . A system as in  claim 32 , wherein the measuring of a parameter representative of an actual measured luminance of the particular pixel at the end of the first display time comprises measuring a voltage stored on a capacitor that has either been charged toward or discharged from a known voltage and the amount of charging or discharging is proportional to a photon flux emitted from the emitter within the particular pixel onto a sensor within the same particular pixel.  
     
     
         51 . A system as in  claim 32 , wherein the steps of identifying, generating, measuring, determining, modifying, and using are repeated for every pixel in the display.  
     
     
         52 . A system as in  claim 32 , wherein the determining of a difference between the identified target luminance and the actual measured luminance for the particular pixel is based on a reference integrated photon flux on the particular pixel sensor determined during a display calibration procedure performed during manufacture or when initially used.  
     
     
         53 . A system as in  claim 32 , further comprising a display calibration procedure that determines and stores an initial transformation for every pixel and every gray level the display may be commanded to display.  
     
     
         54 . A system as in  claim 32 , wherein the measured parameter representative of an actual measured luminance of the particular pixel at the end of the first display time comprises a current measurement corresponding to a number of electrons accumulated or released from a charge storage device.  
     
     
         55 . A system as in  claim 32 , wherein the measured parameter representative of an actual measured luminance of the particular pixel at the end of the first display time comprises a charge measurement corresponding to a number of electrons accumulated or released from a charge storage device.  
     
     
         56 . A system as in  claim 32 , wherein the first display frame is any display frame designated by software programming or by the display user or by a combination of the programming and the user.  
     
     
         57 . A system as in  claim 32 , wherein the frame time following the first frame is any subsequent frame time.  
     
     
         58 . A system as in  claim 32 , wherein the first display frame is any display frame designated by software programming or by the display user or by a combination of the programming and the user.  
     
     
         59 . A system as in  claim 32 , wherein the first display time may be either a single continuous period of time or comprised of a plurality of discontinuous periods of time, and wherein either of the continuous period of time and the discontinuous periods of time may occur during a single frame time or over multiple frame times.  
     
     
         60 . A system as in  claim 32 , wherein storing and/or the using of the modified transformation for generating the display drive signal for the particular pixel is applied at any subsequent portion of a single frame or at different frames.  
     
     
         61 . A system as in  claim 32 , wherein storing and/or the using of the modified transformation for generating the display drive signal for the particular pixel may be either at single continuous period of time or comprised of a plurality of discontinuous periods of time, and wherein either of the continuous period of time and the discontinuous periods of time may occur during a single frame time or over multiple frame times.  
     
     
         62 . A system as in  claim 59 , wherein storing and/or the using of the modified transformation for generating the display drive signal for the particular pixel may be either at single continuous period of time or comprised of a plurality of discontinuous periods of time, and wherein either of the continuous period of time and the discontinuous periods of time may occur during a single frame time or over multiple frame times.