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Adjusting the white balance on led displays.
The display debugging process, there is an adjustable white balance. So let's look at what is white balance.
 White balance is to describe the display of the red, green , blue color mixture white after generation as an indicator of the accuracy . White balance is a very important field of television camera concept , through which you can solve color reproduction and tonal range of issues handled .
White balance is not defective display, changing the color and brightness without affecting the white purity , that does not appear cast, but will not have other variegated doping which, as a large screen for a high-end dedicated display purposes , even if it is very small , " cast " will affect the picture color quality .
The led display is composed by a large number of LED lamps . White balance consistency problems are quite common , which is the industry often encounter difficult problems.
Display device manufacturers require suppliers to provide 5nm wavelength range and 1:1.3 brightness range of the LED device supplier by these indicators through color separation machine reaches the voltage grading consistency generally not required . Typically , full-color display is composed of numerous red, green and blue LED components makes up a pixel for each color LED brightness, wavelength determines the consistency of the display brightness uniformity , white consistency and color degree of consistency. Generally . LED brightness differences in the brightness range of 1:1.3 , blue, green and red wavelength difference is less than 5nm wavelength difference is less than 3nm this lamp composed display (led display other conditions perfect ) will be the opposite conditions were fairly good balance consistency the display may appear Huaping, consistent bad results.
Ie, when viewed at different angles , angled so the LED full color led lights display the same direction with an angle . Its brightness will be incremented or decremented in this way , the red , green and blue three -color LED angle different angles will seriously affect the consistency of the consistency of the white balance , a direct impact on the fidelity of the video color display . To do the red, green , and blue LED brightness changes when different angles matching consistency required in the package lens design , raw material selection on strict scientific design , depending on the skill level packaging suppliers . Even the normal direction of the white display, if the LED point of consistency is not good , the entire screen of different angles balance effect will be poor consistency characteristic angle LED devices LED angle tester can measure , for the medium and end display is particularly important. Red, green and blue LED light shaped curve consistency as possible, the consistency of the entire display will be better. As R / G / B different angles inconsistent brightness caused uneven color , white balance is difficult to achieve consistency of different angles ; discrete and monochromatic light distribution curve is severe, causing the display poor consistency .
Dark LED concentrated in another module , the actual production of the LED lights if there is a difference in the brightness of the LED light in a single module . This difference is very obvious, so be sure to mix light craft used in the production of the LED lights on the display to the normal distribution , so that the consistency of the entire screen display is better ; if the line lights on the device , the light does not smooth , LED lamp light consistency is poor, will directly affect the consistency of the display white balance effect, so must increase the " whole lamp technology " to ensure led display flatness.
Thus affecting the balance display consistency ; signal coding system and the difference signal transmission bandwidth may also affect the balance led display consistency. LED dot matrix module design, as shown in Fig constant current chip output current differences in accuracy and precision of adjustment resistor differences may affect the LED glow. Combination of pixel arrangement is reasonable or not , it may affect the LED lamp light effects and pixel optical overlay effect, thus affecting the display of consistency ; PCB layout and alignment is reasonable or not , resulting in differences in the distribution of power and temperature , which will affect the display 's white balance consistency.
LED main wavelength or λp will shift to longer wavelengths , LED optical parameters pn junction temperature and have a great relationship . If the ambient temperature is high . In particular lattice, a large screen on the LED temperature reliability, stability influence. LED devices emitting region material value of the band gap of the device directly determines the emission wavelength, or color . InGaA lP and InGaN LED chips and other information belonging to group III-V compound semiconductor , GaA similar nature , when the temperature rises , the data band gap will decrease , resulting in the luminescence wavelength becomes longer, the color red-shifted wavelength with junction temperature change is expressed as : λ (T2 = λ (T1 +? T * K nm / ℃) Average K = 0.1 When the junction temperature rise 10 degrees, to the long wavelength shift 1nm and luminous uniformity, consistency variation 2. ~ 5nm wavelength , the human eye can feel the human eye to perceive a different color sensitivity there is a big difference , blue , green zone , a small wavelength will cause change on the human eye , so that the temperature of the blue and green LED device l effect put forward higher requirements.
In order to solve the problem I suggest white consistency initiative summary .
For products using certain methods and means of detection is important, one for display products, led lights . But in view of the value of money and a lot of product defects is not resolved through corrective maintenance , testing and inspection can provide the basis for subsequent product improvement and direction , but can not change the fait accompli of a defective product , so the pre-control is particularly valuable. Able to effectively ensure stability of the LED package reasonable control of the entire process , including the materials sub-file control to ensure the brightness, wavelength consistency ; spectrophotocolorimeter strict management equipment , hand plane machines and station operations , to ensure each product term consistency of the parameters .
Be red, green and blue LED luminance variation when different angles matching consistency ; LED display module design , the two package lens design , the choice of raw materials strictly scientific design . Rational use of the drive circuit and signal disposal algorithms and optimized for PCB reasonably designed to ensure the accuracy and decreases the display module constant internal temperature ; LED display module production with a reasonable mix light process control.
Or electronic display at work for some time, three of the led display LED pixel difference . Each one LED will be different levels of luminance and chrominance down , seriously affecting the display. Brightness and color correction using control technology to achieve brightness <1% Chroma Cx / Cy <0.003 precision calibration , rapidly enhance the display effect , making the module after the update has worked for some time later modules adhere brightness and color degree of consensus. Point correction operation formula is:
Rout = Rin * A11 + Grnin * A12 + Bluin * A13
Gout = Rin * A21 + Grnin * A22 + Bluin * A23
Bout = Rin * A31 + Grnin * A32 + Bluin * A33
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