Improving from LED selection to display optimisation LED Wall Measurement & correction Improving from LED selection to display optimisation Color-Space (Beijing) Science and technology Co., Ltd. Room 345, east 6 building, No.1 shangdi 10th street, haidian, Beijing – China Phone : +86 13701011831 – Fax : +86 10 6283 9945 – www.color-space.co

Fighting with non uniformity on LED screen Bad LED scree comes from Bad LED color and brightness matching New exchanged module much brighter Different LED aging effect Uniformity Problems in Led Screens Colorimetry Modern manufacturing processes for LEDs produce LEDs that vary in both brightness and color Due to the LED itself the brightness may vary as much as 50% and colorimetry as much as 15-20nm This non-uniformity result is very noticeable by spectator

LED selection and matching Improving from LED selection to display optimization At Display level 1 2 3 4 5 6 At LED level At Tile level 7 8 9 R G B R G B Tile adjustment Mounting on Tile Mounting on Display 1 2 3 4 5 6 LED selection and matching 7 8 9 LED adjustment Tile Reorganization

One solution for every need Tile Display Display R G B 1 2 3 1 2 3 4 5 6 4 5 6 7 8 9 7 8 9 R G B Tile Reorganization solution LED adjustment solution Tile adjustment solution What method do you use to improve luminance and color uniformity ? Do nothing : cheaper solution but low quality product Ask the manufacturer to provide the LEDs with high accuracy and you sort it again for each module : very expansive, time consuming and module to module non-uniformity noticeable Do module or tile adjustment Do LED adjustment : the best quality

What is Color-Space solution? One solution for every need What is Color-Space solution? Application Target Sensor Optic Software Field calibration solution On-sit calibration CS-2 F80 to f400 LED Wall calibration Package Tile adjustment Tile Level faberation CS-20 f80 to f400 Tile adjustment Package LED adjustment Modual or Tile level faberation CS-200 f80 Automatic adjustment package

=> We correct from perspective the different measurements Measurement of tile arrangement Measurement of large size display can be difficult to realize exactly on axis (especially for on sit measurements) Initial acquisition Corrected acquisition => We correct from perspective the different measurements

Check of the perspective correction Measurement of tile arrangement Check of the perspective correction Wall Retro 2.30m 1 2 3 4 5 Position 1 : Altitude 1.20m, Distance 3.00m Position 2 : Altitude 1.20m, Distance 2.75m Position 3 : Altitude 1.20m, Distance 4.00m Position 4 : Altitude 1.20m, Distance 2.50m Position 5 : Altitude 0.70m, Distance 2.25m Camera was horizontal on positions 1, 2, 3 & 5 Camera was tilted on position 4.

Measurement of tile arrangement Test procedure: A inhomogeneous white area is displayed on the LED Screen (8x6 regions with variable luminance). Colour measurements are made with CS-20 colorimeter at different locations in front of the LED Screen (5 positions). We compare the integrated values on each area after perspective correction

Deviations are lower than ±1.5% for each camera location Measurement of tile arrangement 1 2 3 4 5 6 7 8 50.5629 54.28089 53.40262 54.31853 53.14751 52.6331 49.62609 48.51362 52.26925 53.97559 55.04623 52.98859 53.22279 52.94676 50.96021 46.76128 51.19024 52.45744 54.32271 53.95467 53.85849 52.35707 50.05686 45.56098 51.23624 51.9974 51.17769 52.26088 51.73811 50.07777 46.63163 43.14367 49.33334 49.75992 48.94857 48.58472 48.27105 46.67345 43.88392 41.04838 46.69018 45.68227 45.93738 44.24359 42.88855 40.88527 39.91918 37.34713 Luminance tables after perspective correction 1 2 3 4 5 6 7 8 49.19473 53.4231 52.75883 53.68498 52.83548 49.60991 48.26219 51.45583 54.5792 52.66941 53.05264 52.88657 50.64464 46.25659 50.44025 52.08178 53.97879 53.64027 53.67859 52.07539 49.64184 44.96636 50.42747 51.5708 50.82349 51.85822 51.32169 49.56519 46.04581 42.4881 48.64543 49.23944 48.46658 48.03864 47.73843 46.07136 43.29929 40.39308 45.95639 45.01107 45.25379 43.47813 42.22622 40.2845 39.33279 36.86731 SM : Compensation de variation d’angle solide Deviations are lower than ±1.5% for each camera location

Suggested or simulated optimization Tile reorganization on LED Wall 9 8 7 6 5 4 3 2 1 12 11 10 Measurement Quality criteria Q Suggested or simulated optimization Selecting organization by operator 1 3 7 6 12 11 10 5 9 8 4 2

CIE 1931 system is not the best choice to quantify color differences Quality criteria for LED Wall CIE 1931 system is not the best choice to quantify color differences MacAdam Ellipses plotted on the CIE 1931 xy chromaticity diagram. The ellipses are 10 times their actual size

CIE 1976 u’,v’ system is a better choice to quantify color differences Quality criteria for LED Wall CIE 1976 u’,v’ system is a better choice to quantify color differences MacAdam Ellipses plotted on the CIE 1976 u’v’ chromaticity diagram. The ellipses are 10 times their actual size

Quality criteria for LED Wall 9 8 7 6 5 4 3 2 1 12 11 10 Color difference Between neighbors Criteria depends on the color system selected: CIE 1931 xy CIE 1976 u’v’ Lab Color variation on Lab is more realistic than u’v’ for same human eye variation. Best choice

Tile reorganization on LED Wall White color before tile color reorganization White color after tile color reorganization

Tile correction on LED Wall 9 8 7 6 5 4 3 2 1 12 11 10 Measurement Correction Tile RGB correction Panel control R G B 9 8 7 6 5 4 3 2 1 12 11 10 Analysis - Tile RGB optimization - Tile RGB target

Measurements on primary colors and white Tile correction on LED Wall Measurements on primary colors and white

Tile correction on LED Wall Dispersion of the characteristics before calibration

Tile correction on LED Wall Each LED has is own color domain in the chromatic plane A common domain is available for the arrangement of tiles x y Available color domain. SM : Add Tile 1, Tile 2, Tile 3 This slide explains the theory => Need to find optimum target color triangle

The software find automatically the best reference colors Tile correction on LED Wall The software find automatically the best reference colors SM : True measurement White is calculated as barycenter of RGB These values are calculated by the software Customer can also selected his own targets (next Slide)

Tile correction on LED Wall Manual adjustement of reference colors is possible: If not applicable values are in red SM : If the target entered by customer is out of theoritical values, it appears in Red

Tile correction on LED Wall After extraction of the color & luminance characteristics of each tile The software computes automatically the different correction matrix by solving each set of linear equations and provides a 3x3 matrix of calibration coefficients The software can also provide the 3x3 matrix of calibration coefficients in the RGB space

Tile correction on LED Wall R G B correction factors are saved to csv file and ready to be stored into the controller and the tiles.

Primary colors and white after tile color correction Tile correction on LED Wall 9 8 7 6 5 4 3 2 1 12 11 10 9 8 7 6 5 4 3 2 1 12 11 10 9 8 7 6 5 4 3 2 1 12 11 10 9 8 7 6 5 4 3 2 1 12 11 10 Primary colors and white after tile color correction

Tile correction on LED Wall Color dispersion before and after calibration SM : Add White point in the center RGB : method more easier to get the coefficient, White is calculated as barycentre from RGB White could be add by customer as target

Phone : +86 13701011831 – Fax : +86 10 6283 9945 – www.color-space.co Thanks for your attention Color-space (Beijing) Science and technology Co., Ltd. Room 345, east 6 building, No.1 shangdi 10th street, haidian, Beijing – China Phone : +86 13701011831 – Fax : +86 10 6283 9945 – www.color-space.co