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Design of new collection systems for multi LED light engines

Design of new collection systems for multi LED light engines. Hüseyin Murat 05/04/2006. LED’s in projectors. A dvantages 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

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Design of new collection systems for multi LED light engines

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  1. Design of new collection systems for multi LED light engines Hüseyin Murat 05/04/2006

  2. LED’s in projectors • 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 systemsexplosion danger • LED narrow spectrum, large color gamut •  increased quality • Large dimming ratio (increased contrast) • Rapidly switchable pulsing (1-panel, 3-panel)

  3. 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

  4. green LED + lens/reflector integrator green blue LED + lens/reflector µD integrator blue integrator red X-cube red LED + lens/reflector µD µD proj. lens LED’s in projectors • System description • 0.9” LV with 4:3 aspect ratio • f# 2.88 • 10% overfill • Esys= 26.19 mm2sr • LED: surface emitter, lambertian • LED’s • Luxeon III and Luxeon V (LumiLEDs); OSTAR (OSRAM) •  Luxeon III and OSTAR

  5. θ (α-2*θ) α light ray TLP 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

  6. GTLP based light engine • Single GTLP collector • 4 massive blocks, decreasing θtap • Simulated for Luxeon III and OSTAR (green) • Luxeon III: opt. coupled, 4:3 ratio, 9.6mm*7.2mm, 25% Esys • OSTAR: opt. not coupled, 2:3 ratio, 9.6mm*14.4mm, 50% Esys

  7. GTLP based light engine • GTLP based multi LED engine • Combine 4 LUXIII-GTLP •  Practically: problem of dome • Combine 2 OSTAR-GTLP • Perfect match to Esys : ALV, f# • 4:3 ratio • Homogenization: uniformly illuminated rectangle

  8. 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

  9. 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 Esys : ALV, 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 Esys : ALV, f# • 4:3 ratio • Uniformly illuminated rectangle

  10. 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 Esys : ALV, 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 Esys : ALV, f# • 4:3 ratio • Uniformly illuminated rectangle • Waste of flux (less efficient) but higher luminance

  11. Parabolic/Elliptical Reflector based light engine • 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%

  12. 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

  13. 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

  14. 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 Esys • Design multi LED collection engines: two approaches • GTLP approach most efficient: 8.54 lm/mm2sr (225 lm), but only for LED’s with flat surface • ER based approach for LED’s with encapsulating dome

  15. Acknowledgments • ‘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”

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