1. 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 : – Fax : –

2. 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

3. 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

4. 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

5. 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

6. => 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

7. 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.

8. 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

9. Deviations are lower than ±1.5% for each camera location
Measurement of tile arrangement 1 2 3 4 5 6 7 8
Luminance tables after perspective correction 1 2 3 4 5 6 7 8
SM :
Compensation de variation d’angle solide
Deviations are lower than ±1.5% for each camera location

10. 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

11. CIE 1931 system is not the best choice to quantify color differences
Quality criteria for LED Wall
CIE 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

12. 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

13. Quality criteria for LED Wall9 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

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

15. Tile correction on LED Wall9 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

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

17. Tile correction on LED Wall
Dispersion of the characteristics before calibration

18. 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

19. 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)

20. 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

21. 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

22. 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.

23. 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

24. 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

25. 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 : – Fax : –