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Design of new collection systems for

multi LED light engines

Hüseyin Murat05/04/2006

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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

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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

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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

µD µDproj. lens

µD

X-cubered LED + lens/reflector

blue LED + lens/reflector

green LED + lens/reflector

integratorred

integrator blue

integratorgreen

optical power [lm]

étendue [mm2sr]

luminance [lm/mm2sr]

electrical power [W]

radiation pattern

Luxeon III 80 7.07 11.32 3.9 lambertian

Luxeon V 160 28.27 5.66 4.8 lambertian

OSTAR 160 13.85 11.55 6.6 lambertian

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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

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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

output luminance [lm/mm2sr]

collection efficiency

[%]

étendue [mm2sr]

output dimensions

[mm2]

length [mm]

electrical power [W]

electrical efficiency

[lm/W]

Luxeon III 7.70 69.6 6.55 7.2*9.6 50 3.9 12.92

OSTAR 8.54 74 13.1 14.4*9.6 100 6.6 16.95

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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

# LED/GTLP

output luminance [lm/mm2sr]

captured flux [lm]

collection efficiency

[%]

volume [mm3]

electrical input power

[W]

electrical efficiency

[lm/W]

Luxeon III 4 7.7 201.5 69.6 15*20*50 15.6 12.92

OSTAR 2 8.54 223.7 74 15*20*100 13.2 16.95

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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

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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

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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

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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

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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/mm2sr]

collection efficiency[%]

electrical power [W]

electrical efficiency [lm/W]

volume[ mm3]

4 Luxeon III+PR 134.7 5.14 45.4 15.6 8.63 45*45 *75

4 Luxeon III +ER 162.7 6.21 54.9 15.6 10.43 120*120*75

2 OSTAR+ER 186.2 7.11 61.6 13.2 14.11 16*100*95

4 OSTAR+ER 232.8 8.89 77 26.4 8.82 85*90*75

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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

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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

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‘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