optimizing white light spectral power distributions to any ... · optimizing white light spectral...
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Optimizing White Light Spectral Power Distributions to Any Action Spectrum
Po-Chieh HungKonica Minolta, Inc.
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Outline
• Background / objective
• Ideas for optimized SPDs / advantage
• Examples
• Possible disadvantage
• Summary & future
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Background / Objective
• Background
– Any Spectral Power Distribution (SPD) for white light
might be realized in the future
How to use the freedom?
• Objective
– Optimize SPDs for any applications
– Identify possible disadvantages3
https://en.wikipedia.org/wiki/Quantum_dot
Telelumen Light Replicator (LEDs)
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Freedom in Spectrum
• Evaluation of light– Correlated Color Temperature– Duv
– CRI (Ra)
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• Requirement from application side– Lower energy consumption– Better color– Better biological response– Lower damage to objects…
How to optimize -> Use of action spectrum
An example: Two spectra having the sameCCT (=4225K), Duv (=0.0018) and Ra (=64)
0
5
10
15
20
25
350 400 450 500 550 600 650 700 750 800
Rela
tive
inte
nsity
Wavelength (nm)
F2LED
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Name Applications Function Advantage Action spectrum
Maximum LER General lighting Minimize energyconsumption Save energy Luminosity function
Maximum Color Gamut Retail, theater Boost color saturation Better sales at retailers (color gamut)
Maximum Impact on ipRGC
Office, assisted living, airplane Stimulate, wake-up Prevent sleepiness,
increase productivity Melanopic function,or ipRGC (intrinsically photosensitive retinal
ganglion cells) sensitivityMinimum Impact on
ipRGC
Assisted living,Sleep light,
cockpits
Keep pupil open, Not to suppress
Melatonin, not-to-awake
Safe in dark environment,Not-to-awake
Museum Light Museum, galleries
Minimize damage to fine arts
Preservation of art objects from fading Damage function
No-Blue LightClean room (semiconductor manufacturing)
Reasonable CRI without 500nm or under
Comfortable work environment Photoresist sensitivity
Ideas for Optimizing White SPDs for Specific Applications
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Optimization: Wanted & Unwanted Action Spectra • Wanted spectrum
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Maximum LER Maximum Color Gamut Maximum Impact on ipRGC
Minimum Impact on ipRGC Museum Light No-Blue Light
• Unwanted spectrum
Luminosity function Melanopic functiona.k.a. ipRGC (intrinsically
photosensitive retinal ganglion cell)
sensitivity
Photoresist sensitivityHarmful for paintings
Color gamut
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Optimization- General Approach
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Maximize / MinimizeEvaluation Function
Lower CRI
Any CCT
Optimize
~Zero Duv
?Without constraint &With constraint of LED
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Maximum LER
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• To maximize energy efficiency
( ) ( )( )
⋅
⋅
∫∫
λλ
λλλ
dL
dVLmax
Condition: CCT: 2856KDuv: 0CRI: 90
Type LER (lm/W)
Optimal 410
LED 379
Blackbody* 154
Tgldenver, flickr.com
* Calculated in 380-780 nm
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0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
u'
v'
Maximum Color Gamut
• To show the object colors appear saturated
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Condition: CCT: 5000KDuv: 0CRI: (do-not-care)
( )
∑=
8
1max
iiArea
Area(i)
Tim Murtaugh, flickr.com
Type Gamut size
Optimal 179%
LED 156%
Blackbody 100% (ref.)
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Maximum Impact on ipRGC
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Condition: CCT: 6500KDuv: 0CRI: 80
( ) ( )( ) ( )
⋅
⋅
∫∫
λλλ
λλλ
dVL
dipRGCLmax
• To “wake-up”
Doug, flickr.com
Type Impact(D65 ref.)
Optimal 140%
LED 120%
Blackbody 100% (ref.)
With LER concerned
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Minimum Impact on ipRGC
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( ) ( )( ) ( )
⋅
⋅
∫∫
λλλ
λλλ
dVL
dipRGCLmin
• Not to disturb circadian rhythm / to keep pupils openCondition:
CCT: 2856KDuv: 0CRI: 80
http://www.defense.gov/dodcmsshare/newsphoto/1999-08/990831-N-1056R-001.jpg
Type Impact Impact (D65 ref.)
Optimal 71% 30%
LED 84% 35%
Blackbody 100% (ref.) 42%
With LER concerned
CIE TN 003:2015 Report on the First International Workshop on Circadian and Neurophysiological Photometry
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Museum Light
• To prevent fading of artifacts
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Condition:CCT: 4000KDuv: 0CRI: 95
( ) ( )( ) ( )
⋅
⋅
∫∫
λλλ
λλλ
dVL
ddamageLmin
dee_dee_creamer, flickr.com
Type Impact
Optimal 57%
LED 64%
Blackbody 100% (ref.)
CIE publication 157 Damage function
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No-blue Light
• No power below 500nm to avoid exposure to photoresist
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Condition: CCT: 2000KDuv: 0.005CRI: 45
Megan,Laver, flickr.com
Type CCT DuvCRI-Ra
CRI-R9
Optimal 2000 0.005 45 20
LED + Y filter 2000 0.005 45 75
F2 + Y filter 3235 0.034 33 -127
( ) ( )( ) ( )
⋅
⋅
∫∫
λλλ
λλλ
dVL
dregionblueL _min
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Color Appearances Under 6 SPDs• Note: Camera spectral sensitivity does not match color matching functions of human eye
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Maximum LER Maximum Color Gamut Maximum Impact on ipRGC
Minimum Impact on ipRGC Museum Light No-Blue Light
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Result of Optimization
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End up with spiky spectrum while color rendering is kept.
Why?
Optimization creates “extreme” spectrum Usual reflective materials have a commonality in spectrum domain
• 5-6 principle components can produce almost any spectral reflectance
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Possible Disadvantages of Spiky Spectra
Chromatic aberration
Bad color reproduction by camera
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Possible Disadvantage: Chromatic Aberration
Single lens→ Chromatic Aberration
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Possible disadvantage: Bad Color Reproduction by Camera
Simulation• Color Matching Function (CMF) by Stiles and Burch (=10 sets)• RGB filter and CMY filter camera (=4 sets)
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Eye variation
Camera variation (RGB/CMY)
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Possible disadvantage: Bad Color Reproduction by Camera
• Camera may give larger color reproduction errors by spiky light sources
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Human variation
Camera variation
(Avg. of F2, F7, F11 and 3 LEDs)
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Summary / Future
Optimization is possible for any application:• Better result while keeping a moderate color reproduction• Action spectrum or color gamut can be used• Spectrum will be spiky
Possible disadvantages caused by spiky spectrum: • May emphasize chromatic aberration for eyes• May cause bad color reproductions by cameras
More & New Values by Tuning Spectrum
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However…
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Dr. Jeffery Tsao Sandia National Laboratories
Prof. Konstantinos Papamichael and his staffsCalifornia Lighting Technology Center, University of California, Davis
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Acknowledgements
[Copyright notice] Some figures used in this presentation are cited with minor modifications from the following presentations:• Po-Chieh Hung and Konstantinos Papamichael, Application-Specific Spectral Power Distributions of White Light, SID International
Symposium Digest of Technical Papers, Vol. 48 (2015).• Po-Chieh Hung, Extreme Spectral Power Distribution of Light Source and its Impact to Vision and Cameras Sensitivity, IS&T 21st Color and
Imaging Conference (2013).