© imec 2006 Photonics Europe Design of new collection systems for multi LED light engines Hüseyin Murat 05/04/2006

© imec 2006 Photonics Europe Advantages LED’s in comparison with UHP Directly R,G,B No dichroic mirrors  price, volume and losses No UV and IR filters Robust and very long life time Low operating voltage Small size  compact, portable, inexpensive Absence of mercury and projection systems explosion danger LED narrow spectrum, large color gamut  increased quality Large dimming ratio (increased contrast) Rapidly switchable  pulsing (1-panel, 3-panel) LED’s in projectors

© imec 2006 Photonics Europe LED’s in projectors Bottleneck Small optical output (luminance) Étendue limitation of projector (f#, LV)  low projected flux LED interesting for low power applications Using high luminance LED’s Optimally collecting available flux Combining multiple LED’s Design of new collection systems ‘Gradually Tapered Light Pipes’ based ‘Elliptical and Parabolic Reflector’ based

© imec 2006 Photonics Europe LED’s in projectors System description 0.9” LV with 4:3 aspect ratio f# % overfill  E sys = mm 2 sr LED: surface emitter, lambertian LED’s Luxeon III and Luxeon V (LumiLEDs); OSTAR (OSRAM)  Luxeon III and OSTAR µD proj. lens µD X- cube red LED + lens/reflector blue LED + lens/reflector green LED + lens/reflector integrator red integrator blue integrator green optical power [lm] étendue [mm 2 sr] luminance [lm/mm 2 sr] electrical power [W] radiation pattern Luxeon III lambertian Luxeon V lambertian OSTAR lambertian

© imec 2006 Photonics Europe Types of collectors Gradually Tapered Light Pipes Principle Collection within the f# Homogenization to uniform illumination Reshaping to 4:3 aspect ratio Propagation by TIR Reflector with light pipe Collection within f#  reflector Homogenization and reshaping: light pipe Propagation by mirroring sides θ α ( α -2* θ ) TLP light ray

© imec 2006 Photonics Europe GTLP based light engine Single GTLP collector 4 massive blocks, decreasing θ tap Simulated for Luxeon III and OSTAR (green) Luxeon III: opt. coupled, 4:3 ratio, 9.6mm*7.2mm, 25% E sys OSTAR: opt. not coupled, 2:3 ratio, 9.6mm*14.4mm, 50% E sys output luminance [lm/mm 2 sr] collection efficiency [%] étendue [mm 2 sr] output dimensions [mm 2 ] length [mm] electrical power [W] electrical efficiency [lm/W] Luxeon III * OSTAR *

© imec 2006 Photonics Europe GTLP based light engine GTLP based multi LED engine Combine 4 LUXIII-GTLP  Practically: problem of dome Combine 2 OSTAR-GTLP Perfect match to E sys : A LV, f# 4:3 ratio Homogenization: uniformly illuminated rectangle # LED/GTLP output luminance [lm/mm 2 sr] captured flux [lm] collection efficiency [%] volume [mm 3 ] electrical input power [W] electrical efficiency [lm/W] Luxeon III *20* OSTAR *20*

© imec 2006 Photonics Europe GTLP based light engine Uniformity (ANSI): 4xLUXIII system - Brightest location: 5.2% greater than average - Dimmest location: 8.8% less than average 2xOSTAR system - Brightest location: 1.6% greater than average - Dimmest location: 8.3% less than average

© imec 2006 Photonics Europe Parabolic/Elliptical Reflector based light engine Parabolic Reflector and Luxeon III 4 LUX III – PR: collection within f# Combining by reflecting pipe (60mm) Perfect match to E sys : A LV, f# 4:3 ratio Uniformly illuminated rectangle Elliptical Reflector and Luxeon III 4 LUX III- ER: collection witihin f# Combining by reflecting pipe (60mm) Perfect match to E sys : A LV, f# 4:3 ratio Uniformly illuminated rectangle

© imec 2006 Photonics Europe Parabolic/Elliptical Reflector based light engine Elliptical Reflector and 2 OSTAR 2 OSTAR - ER: collection within f# Combining by reflecting pipe (80mm) Perfect match to E sys : A LV, f# 4:3 ratio Uniformly illuminated rectangle Elliptical Reflector and 4 OSTAR 4 OSTAR - ER: collection witihin f# Combining by reflecting pipe (60mm) Perfect match to E sys : A LV, f# 4:3 ratio Uniformly illuminated rectangle Waste of flux (less efficient) but higher luminance

© imec 2006 Photonics Europe 4x PR and LUXIII:+3.1%/-9.5% 4x ER and LUXIII:+4.1%/-5.9% 2x ER and OSTAR:+5.1%/-2.7% 4x ER and OSTAR:+3.2%/-2.1% Parabolic/Elliptical Reflector based light engine

© imec 2006 Photonics Europe Parabolic/Elliptical Reflector based light engine Results: Luxeon III: ER better PR (21%), but less compact OSTAR based engines more performant than Luxeon based engines 4 OSTAR boost in projected flux, but low power efficiency and more volimunous Uniformity Luxeon:ER more uniform than PR OSTAR engines better than Luxeon engines 4 OSTAR best uniformity output flux [lm] luminance [lm/mm 2 sr] collection efficiency[%] electrical power [W] electrical efficiency [lm/W] volume [ mm 3 ] 4 Luxeon III+PR *45 *75 4 Luxeon III +ER *120*75 2 OSTAR+ER *100*95 4 OSTAR+ER *90*75

© imec 2006 Photonics Europe GTLP vs Reflector based multi LED engine GTLP most compact and efficient (collection,power) Only useable for LED’s with flat surface (no dome) + OSTAR, - Luxeon ER/PR lower optical efficiencies, larger volume Suited for LED’s with dome e.g. Luxeon, but also for OSTAR type LED’s Higher uniformity ER approach better than PR approach, but larger GTLP approach for OSTAR and Reflector approach for Luxeon type LED’s

© imec 2006 Photonics Europe Conclusion LED’s very interesting: superior properties but low optical power  low power applications Optimally collect available flux and combine multiple LED’s witihin the E sys Design multi LED collection engines: two approaches GTLP approach most efficient: 8.54 lm/mm 2 sr (225 lm), but only for LED’s with flat surface ER based approach for LED’s with encapsulating dome

© imec 2006 Photonics Europe ‘Fonds voor Wetenschappelijk Onderzoek – Vlaanderen’ (FWO) “Novel optical architectures for LCOS projectors” ‘Instituut voor de aanmoediging van innovatie door Wetenschap en Technologie in Vlaanderen’ (IWT) and ‘Barco N.V.’ “ Compact high-quality LED projection systems” Acknowledgments