Organized by:
Making Sense with LEDs As Presented By: Ron Steen Steen, Xicato LEDucation 5 – March 16th, 2011 Media Sponsor:
WWW.LEDUCATION.ORG
1
2
Color Consistency What to Look For
3
Color and Energy
4
Color Temperature
Black Body Curve CCT 5
MacAdam Ellipses 1 Ellipse is defined as the ability bilit to t see the th change h in i color
David MacAdam The u’v’ measure is similar to X,Y in an updated format 6
White is White - Right?
• Color variation issues with LEDs – Variation in LED wave length – Variation in Phosphor – Variation in Thermal Properties
• Color shift over time • Color shift over temperature • Color shift over drive current.
7
Sources of Color Variation
8
ANSI C78.377 Chromaticity Requirement
9
What is the right metric and target values?
CCT & Duv lines in CIE 1931 diagram ANSI NEMA C78.377-2008 Specifications for the chromaticity of solid state lighting products
10
Industry Best Color Consistency Industry Standard Color Bins
Line
Y
CCT
7 step
54
19
p 4 step
22
39
1x2 step
8
102
IIndustry d t best b t Specification 1x2 Ellipse p LED Manufacturer A
11
Color consistency targets are tight...
12
Spectral Power Distribution
13
Spectral Power Distribution
14
CRI Calculation
Source NIST
15
CRI and CCT Dependence? Wh th Why the Diff Difference? ? CRI is derived against a reference at a specific CCT
Daylight D li ht ~ 6000 CCT CRI Value of 93
Halogen ~ 4100 CCT CRI Value of 98 16
Source Full Spectrum Solutions
80 Vs V 95 CRI + R9 ~80 80 CRI R9 = 16
~95 95 CRI R9 = 96
17
80 Vs 95 CRI - 3000K (R9 comparison) CRI = 97 (Typ) ( yp) (95 Min)
Spectra Artist,, (T=70째C) p ( )
80 CRI
90+ CRI
18
19
Reliability Testing Methodology 85o Celsius, 85% Relative Humidity Combined Environment Power Cycle Testing • •
Automotive A i S Standard d d test Combined environment accelerates potential failures Test in heat and Humidity
•
– Humidity affects materials around LED and phosphors
LM 80 Testing - IESNA lifetime standard • • •
High temp testing 6000 hours Enabling Energy Star 20
Color Maintenance •Color Maintenance after 3Khours •LM-80 test 85o C
3000K
•Color Stability dependant on Phosphor •Better Thermal = Better Color Stability
1x2 Step Specification
The Red Cliff 4 MacAdam Ellipse
•Each set of points represents a different module under test. •Multiple data points represent different HTOL test time intervals
•Red phosphor degradation w/ heat •80o C ((176o F)) Tipping Point 21
Color Matching Functions
22
Color Space Evolution Used to Calculate CCT
Whatt we Wh use and refer to
1976
1960/4
1931
Used to Calculate Color Shift
23
24
Good on Paper not on the Wall!
80 CRI 95 CRI
25
1976 1960/4 1 Wh at we use and ref er to
Us ed to Cal cul ate CC T
Used to Calc ulate Color Shift
1931
26
Definitions: Photometric Units •
Luminous Flux: light power of a source, as perceived by the human eye (Photometric units) – Optical p power p with the power p at each wavelength g weighted g byy the eye y sensitivity function
Characterization of a light source should account for how it is perceived by y the human eye y (Photometric ( units)) 27
The Tristimulus Values
‌Thus,, in principle, p p , three parameters p describe a color sensation. The tristimulus values of a color are the amounts of three primary colors in a three-component additive color model needed to match that test color. The tristimulus values are most often given in the CIE 1931 color space, in which they are denoted X, Y, and Z.[5] Source Wikipedia
28
Color Matching Functions CMF Calculation • x = X/(X+Y+Z), y = Y/(X+Y+Z) and z = Z/(X+Y+Z) • • •
X = ∫X( )S( )d( ), Y = ∫Y( )S( )d( ), Z = ∫X( )S( )d( )),
•
Where S( ) is the spectral power density of source
•
The CMFs are derived based on the sensitivity y of human eye to primary colors
29
Spectral Power Distribution How important was blue in 1931?
How important is blue now?
30
New color matching functions Proposal E Errors i bl in blue region i h have significant i ifi t effect ff t
Represents Errors
31
New CMF – Good on paper + on wall
80 CRI
95 CRI 32
Color Space Evolution Used to Calculate CCT
Whatt we Wh use and refer to
1976
1960/4
1931
Used to Calculate Color Shift
33
Specifying p y g colors with LEDs - Checklist Item
Yes
No
Is the LED color specification centered at the Black Body Curve? Can the LED Supplier show boundary samples at ends of quoted color specification? Will the supplier leave boundary samples behind as comparison at time of installation? Can the selected color bin be supported in production volumes? Does the D h supplier li have h color l maintenance i Data? D ? – Color C l shift hif over time and temperature
34
35
1
Color Consistency What to Look For
2
Color and Energy
3
Color Temperature
Black Body Curve CCT 4
MacAdam Ellipses 1 Ellipse is defined as the ability bilit to t see the th change h in i color
David MacAdam The u’v’ measure is similar to X,Y in an updated format 5
White is White - Right?
• Color variation issues with LEDs – Variation in LED wave length – Variation in Phosphor – Variation in Thermal Properties
• Color shift over time • Color shift over temperature • Color shift over drive current.
6
Sources of Color Variation
7
ANSI C78.377 Chromaticity Requirement
8
What is the right metric and target values?
CCT & Duv lines in CIE 1931 diagram ANSI NEMA C78.377-2008 Specifications for the chromaticity of solid state lighting products
9
Industry Best Color Consistency Industry Standard Color Bins
Line
Y
CCT
7 step
54
19
p 4 step
22
39
1x2 step
8
102
IIndustry d t best b t Specification 1x2 Ellipse p LED Manufacturer A
10
Color consistency targets are tight...
11
Spectral Power Distribution
12
Spectral Power Distribution
13
CRI Calculation
Source NIST
14
CRI and CCT Dependence? Wh th Why the Diff Difference? ? CRI is derived against a reference at a specific CCT
Daylight D li ht ~ 6000 CCT CRI Value of 93
Halogen ~ 4100 CCT CRI Value of 98 15
Source Full Spectrum Solutions
80 Vs V 95 CRI + R9 ~80 80 CRI R9 = 16
~95 95 CRI R9 = 96
16
80 Vs 95 CRI - 3000K (R9 comparison) CRI = 97 (Typ) ( yp) (95 Min)
Spectra Artist,, (T=70째C) p ( )
80 CRI
90+ CRI
17
18
Reliability Testing Methodology 85o Celsius, 85% Relative Humidity Combined Environment Power Cycle Testing • •
Automotive A i S Standard d d test Combined environment accelerates potential failures Test in heat and Humidity
•
– Humidity affects materials around LED and phosphors
LM 80 Testing - IESNA lifetime standard • • •
High temp testing 6000 hours Enabling Energy Star 19
Color Maintenance •Color Maintenance after 3Khours •LM-80 test 85o C
3000K
•Color Stability dependant on Phosphor •Better Thermal = Better Color Stability
1x2 Step Specification
The Red Cliff 4 MacAdam Ellipse
•Each set of points represents a different module under test. •Multiple data points represent different HTOL test time intervals
•Red phosphor degradation w/ heat •80o C ((176o F)) Tipping Point 20
Color Matching Functions
21
Color Space Evolution Used to Calculate CCT
Whatt we Wh use and refer to
1976
1960/4
1931
Used to Calculate Color Shift
22
23
Good on Paper not on the Wall!
80 CRI 95 CRI
24
1976 1960/4 1 Wh at we use and ref er to
Us ed to Cal cul ate CC T
Used to Calc ulate Color Shift
1931
25
Definitions: Photometric Units •
Luminous Flux: light power of a source, as perceived by the human eye (Photometric units) – Optical p power p with the power p at each wavelength g weighted g byy the eye y sensitivity function
Characterization of a light source should account for how it is perceived by y the human eye y (Photometric ( units)) 26
The Tristimulus Values
‌Thus,, in principle, p p , three parameters p describe a color sensation. The tristimulus values of a color are the amounts of three primary colors in a three-component additive color model needed to match that test color. The tristimulus values are most often given in the CIE 1931 color space, in which they are denoted X, Y, and Z.[5] Source Wikipedia
27
Color Matching Functions CMF Calculation • x = X/(X+Y+Z), y = Y/(X+Y+Z) and z = Z/(X+Y+Z) • • •
X = ∫X( )S( )d( ), Y = ∫Y( )S( )d( ), Z = ∫X( )S( )d( )),
•
Where S( ) is the spectral power density of source
•
The CMFs are derived based on the sensitivity y of human eye to primary colors
28
Spectral Power Distribution How important was blue in 1931?
How important is blue now?
29
New color matching functions Proposal E Errors i bl in blue region i h have significant i ifi t effect ff t
Represents Errors
30
New CMF – Good on paper + on wall
80 CRI
95 CRI 31
Color Space Evolution Used to Calculate CCT
Whatt we Wh use and refer to
1976
1960/4
1931
Used to Calculate Color Shift
32
Specifying p y g colors with LEDs - Checklist Item
Yes
No
Is the LED color specification centered at the Black Body Curve? Can the LED Supplier show boundary samples at ends of quoted color specification? Will the supplier leave boundary samples behind as comparison at time of installation? Can the selected color bin be supported in production volumes? Does the D h supplier li have h color l maintenance i Data? D ? – Color C l shift hif over time and temperature
33
34