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Kleuraspecten van LED toestellen - KAHO / Laboratorium voor Lichttechnologie
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Kleuraspecten van LED toestellen - KAHO / Laboratorium voor Lichttechnologie

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ECL 2012

ECL 2012

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  • 1. Kleuraspecten van LED toestellenRichard VanraesPeter HanselaerLaboratorium voor Lichttechnologie, GentKAHO Sint-LievenKU Leuven
  • 2. Outline• Light&Lighting Laboratory• Colorimetry in a nutshell• Colorimetry of LEDs• RGB or phosphor white?• Impact of junction temperature?• Impact of viewing angle?• Impact of operating time?• What about colour rendering ? 2
  • 3. Light&Lighting Laboratory: the team 3
  • 4. Light&Lighting Laboratory: topics Lighting Optical design Measurement FacilitiesAppearance New Light Sources 4
  • 5. Light&Lighting Laboratory: activitiesPhD research items Industrial consultancy• LEDs and general lighting • 3 consortia• OLED • >70 companies• remote phosphor LEDs • Bilateral projects• lighting in the operating room • Projects with non-profit• colour rendering organisations• gloss perception • Measurements• colour appearance • Courses• ray tracing • Lectures• scattering and fluorescence• spectral response solar cells 5
  • 6. Combination of research and consultancy PhD Research Education Society Industrial Consultancy
  • 7. Light&Lighting Laboratory: measurement facilitiesSpectrometers/ CCD detectors 7
  • 8. Light&Lighting Laboratory: measurement facilitiesNear field goniometers 8
  • 9. Colorimetry in a nutshell: colour classificationMunsellHue 5Y 5Y 8/12 9
  • 10. Colorimetry in a nutshell: colour matching Three primary sourcesTest colour K K  AA  BB  CCwith luminance LK LK  A.LA  B.LB  C.LC 10
  • 11. Colorimetry in a nutshell: trichromatic values PrimariesTrichromatic values x 0.706 x 0.863 x 0.863Kleurcomponenten X,Y,Z    11
  • 12. Colorimetry in a nutshell: colour coordinatesIgnoring brightness, only two numbers are needed: colour coordinates (x,y) (Kleurcoördinaten) X x X Y  Z Y y X Y  Z 12
  • 13. Characteristics Colorimetry in a nutshell: chromaticity diagram • Spectrum locus • Additive mixing • Purity, saturation • Colour gamut • Primary colours 13
  • 14. Colorimetry in a nutshell: correlated colour temperatureThe correlated colour temperature is thetemperature of a Planckian radiator havingthe chromaticity nearest the chromaticityassociated with the given spectral distributionon a diagram where the (CIE1931 standardobserver based) u, v coordinates of thePlanckian locus and the test stimulus aredepicted. 14
  • 15. Colorimetry in a nutshell:correlated colour temperature Black Body Locus EN 12464 • CCT<3300 K : “warm white” • 3300 K< CCT< 5300 K: “neutral white” • CCT>5300K: “cool daylight” 15
  • 16. Colorimetry in a nutshell: colour renderingThe colour rendering index CRI of a light source is a measure of the shift in chromaticity of a set of objects when they are lighted by the source as compared to be lighted by a reference source of comparable colour temperature. 16
  • 17. Colorimetry in a nutshell: colour renderingTestsamples (8 of 14) Testlamp Colour coordinates <colour differences> Standardlamp Colour coordinates 17
  • 18. Colorimetry in a nutshell: chromatic adaptation• The visual system is able to partially or completely disaccount for the colour of the illuminant such that the white of the illuminant is always perceived as “white” (complete adaptation)• This is accomplished by changing the sensitivities of the red, green and blue visual channel. 18
  • 19. Colorimetry in a nutshell: chromatic adaptation* 19
  • 20. Colorimetry in a nutshell: colour matching* * 20
  • 21. Colorimetry of LEDs: spectrumE Spectrale stralingsintensiteit 1500 1240 1200 LED1  (nm)  (mW/sr.nm) Band gap Eg 900 Eg (eV ) 600 300 0 350 400 450 500 550 600 650 700 750 Golflengte (nm)1. Peak wavelength is determined by bandgap Eg c 1240 E  Eg (eV )  h.f  h.    (nm)2. Number of photons: drive current and recombination probability 21
  • 22. Colorimetry of LEDs: chromaticityHigh purity coloursWide colour gamutpossibleNo direct generationof white lightCIE chromaticity 22
  • 23. Colorimetry of LEDs:RGB additive mixing 23
  • 24. Colorimetry of LEDs:Phosphor White LEDs 24
  • 25. Colorimetry of LEDs:Phosphor White LEDs 25
  • 26. RGB or Phosphor White? ExperimentLEDs from 3 manufacturers• 1 phosphor-white package (350 mA)• 1 red-green-blue packageComparison of consumed power for same• luminous flux• colour coordinates• heat sinkwith PW as reference 26
  • 27. RGB or Phosphor White? Results P (W) eff. (lm/W) P (W) eff. (lm/W)MFR flux (lm) CIE (x,y) PW PW RGB RGBM1 84.1 (0.31, 0.33) 1.16 72.5 2.44 34.5M2 45.9 (0.32, 0.33) 1.06 43.3 2.50 18.4M3 77.6 (0.30, 0.32) 1.11 69.9 2.61 29.7 1,8 1,6 1,4 PW 1,2 RP (W) 1 0,8 G 0,6 B 0,4 0,2 0 M1 Cree M2 Lumileds M3 SSC 27
  • 28. Impact of junction temperature? Spectrum E 1240 Band gap Eg  (nm)  Eg (eV )Decrease of the bandgap: increase of wavelengthDecrease of recombination rate: decrease of flux 28
  • 29. Impact of junction temperature? Chromaticity piek I U x y (nm/°C) (cd/°C) (V/°C) (1/°C) (1/°C) Red 0.19 - 0.058 - 0.0012 90 E-6 - 90 E-6Green 0.11 - 0.016 - 0.0040 42 E-5 - 23 E-5Yellow 0.14 - 0.052 - 0.0019 55 E-5 - 55 E-5 29
  • 30. Impact of junction temperature? Active cooling 30
  • 31. Impact of junction temperature? LuxeonIII U(junction T) for series 1 (used) Forward voltage 2.45 2.40 2.35 2.30 2.25 1: 10 µA 2.20 y = -0.0026x + 2.4443 1: 100 µAU (V) R2 = 0.999 2: 10 µA 2.15 2: 100 µA 2.10 2.05 2.00 1.95 1.90 20 30 40 50 60 70 80 90 100 110 temperature (°C)  nk  U f T    ln  I m   a  T  b e  31
  • 32. Impact of junction temperature? Determination 32
  • 33. Impact of junction temperature Self heating With and without heat sink Different ambient temperatureLuminous flux is dependent onheat sink, position of heat sink, . . . 33
  • 34. Impact of viewing angle? Chromaticity I (85°) fluxI(0°) 34
  • 35. Impact of viewing angle? SpectrumNegligible impact when usingremote phosphor LEDs 35
  • 36. Impact of operating time? Chromaticity Degradation ofExperiments the phosphor 36
  • 37. Impact of operating time? CCT and CRI CRI Verschil in % CCT [K] Verschil in % September Januari April Januari tov April tov September Januari April Januari tov April tov 2010 2011 2011 september september 2010 2011 2011 september september Lamp 1 90 89 89 -1% -1%Lamp 1 4186 4066 4075 -3% -3% 6876 6637 6818 -3% -1% Lamp 2 72 73 73 1% 1%Lamp 2Lamp 3 3709 3653 3701 -2% 0% Lamp 3 76 78 80 3% 5% 4016 3874 3834 -4% -5% Lamp 4 69 70 69 1% 0%Lamp 4Lamp 5 4207 4077 4128 -3% -2% Lamp 5 76 78 79 3% 4%Lamp 6 3194 3167 3194 -1% 0% Lamp 6 65 66 65 1% 1%Lamp 7 3307 3153 3175 -5% -4% Lamp 7 71 71 71 0% 0%Lamp 8 3853 3717 3743 -4% -3% Lamp 8 77 77 77 0% 0%Lamp 9 3365 3307 3326 -2% -1% Lamp 9 88 88 88 0% 0%Lamp 10 3678 3470 3670 -6% 0% Lamp 10 78 77 80 -1% 3%Lamp 11 4733 4586 4625 -3% -2% Lamp 11 65 65 65 0% 0%Lamp 12 5329 5037 5104 -5% -4% Lamp 12 73 72 73 -1% 0% gemiddelde 75 76 76 0% 1% mediaan 76 77 77 1% 1% IEC PAS 62717: CRI after 6000 h: maximum -5 CCT after 6000 h: within 1 class (100 K) 37
  • 38. What about colour rendering? ProblemReference Illuminant Ra=83 Ra=70 Ra=60 Ra=100 Ra=85 Ra=50Large colour differences towards reference  low quality ! Kevin.Smet@kahosl.be 38 38
  • 39. What about colour rendering? Memory coloursThe more similar a light source renders the familiar object colours to their memory colours, the better the colour quality. 39
  • 40. What about colour rendering? Determination of Memory colours Colour appearance rating of real familiar objectsThe closer the test illuminant reaches the memorycolour of 10 objects, the higher the MCRI 40 Kevin.Smet@kahosl.be 40
  • 41. What about colour rendering? Experimental validation• Aspects of colour quality investigated – Preference/attractiveness (appreciation) – Naturalness• Thirteen colour quality metrics (CIE TC 1-69)• Combining results of 9 psychophysical studies Correlation between 13 metric predictions and all the visual data is calculated. 41 Kevin.Smet@kahosl.be 41
  • 42. What about colour rendering? Experimental validationMemory metric for preference/attractiveness: ravg = 0.88GAI_Ra for naturalness: ravg = 0.85 42 Kevin.Smet@kahosl.be 42
  • 43. What about colour rendering? Optimizing LED clustersXb  Xg  Xr  Xw  X Yb  Yg  Yr  Yw  Y Zb  Zg  Zr  Zw  Z xi Xi  .Yi yi zi Zi  .Yi yiOptimum MCRIánd efficacy 43 Kevin.Smet@kahosl.be 43
  • 44. What about colour rendering? Visual performance Visual experiment with 2700K setting:MEAN/MEDIAN Attractiveness Preference Naturalness Vividness MemorySa optimized LED 7.8 / 8.0 7.9 / 8.0 7.2 /8.0 7.4 /8.0 7.9 /8.0 RGB LED cluster 6.0 / 6.0 5.6 / 6.0 4.2 / 4.5 6.3 / 7.0 4.8 / 5.0Incandescent lamp 5.8 / 6.0 6.0 / 6.0 6.9 / 7.0 6.2 / 6.5 6.5 / 6.0• Sa optimized LED lamp scored significantly better (p<0.05) than the incandescent source for attractiveness, preference and memory.• No significant differences for naturalness and vividness ! 44 Kevin.Smet@kahosl.be 44
  • 45. www.lichttechnologie.be: daar brandt de lamp . . .