Automotive matrix systems with improved efficiency Dr. B. Spinger

18.01.30, DOE SSL R&D Workshop

©2017 Lumileds Holding B.V. | 2 February 5, 2018

• Application Requirements: Matrix Headlamp • Direct projection of Light source • Pre-collimation for higher system efficiency • Direct integration to LED surface

Overview

©2017 Lumileds Holding B.V. | 3 February 5, 2018

i 0 0S 0 L t[ 20 675] 0 d/ 2̂

-6.8

60

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Angl

e in

°

• AFS (Adaptive Front lighting System): beam adaption according driving situation (ECE R123) + swiveling Low Beam

Adaptive Driving Beam / Matrix: Application Overview

Basic Idea: switch an LED Matrix

• ADB (Adaptive Driving Beam): Glare free High Beam – selectively block light in direction of oncoming cars

• Marking Light: high light selective areas if there is a potential risk

• Automatic Levelling: adjustment of beam according to load and acceleration of car and slope of road

©2017 Lumileds Holding B.V. | 5 February 5, 2018

Direct Projection of LED • Use a simple (aspherical) lens or a reflector • Cost efficient system optic

But:

• Close placement of LED is required • Compromise between Lens aberrations

and collection efficacy – typically only 20-30% collected

• Contrast in beam is generated by contrast in light source

Alternative:

• Combination of two or more systems: the overlap can fill the area between pixel

• Structure on lens surface to smear out the images

1.8 mm gap between die

0.1 mm gap between die

A8

©2017 Lumileds Holding B.V. | 6 February 5, 2018

• 4x24 LEDs • 90 µm gap between the LEDs • White side coating is filling the gap:

contrast pixel to pixel need to be 200:1

• Each LED can be addressed individually • Dimming via plus width modulation • High LED luminance is required –

up to 100 MNIT

• >10000 installed Lumen, but only 25% will be used at the same time

• System efficiency: 20% - 40% of the generated light will reach the road

Example System

©2017 Lumileds Holding B.V. | 7 February 5, 2018

Indirect Projection - Imaging the exit plane of a pre-collimator • Collimator needs to be designed to generate desired

illuminance distribution at exit : - Uniformity: e.g. CPC or simple cone - Gradient: asymmetric

• Additional elements can be used or integrated to improve collection efficiency or correct for lens aberrations

• Alignment – especially in z-direction is very critical

©2017 Lumileds Holding B.V. | 8 February 5, 2018

Design rules for pre-collimator: optimize system flux

LED with TIR optic attached with air gap

• Simulation of optical system flux • based on TIR optic attached to the LED,

but with air gap

Projection system

Maximum system flux by optimized entry size and distance chip to entry

35 mm

50 mm

spillage at lens

absorption at lens

absorption on chip

spillage at light guide

1.4x1.4 mm²

x mm² z mm²

*TIR = Total Internal Reflection

©2017 Lumileds Holding B.V. | 9 February 5, 2018

200%

180%

160%

140%

120%

100%

0 0.04 0.08 0.12 0.16 0.2 0.24 0.28

entr

y siz

e re

l to

chip

size

air gap [mm]

Relative flux through system

20%-30% 30%-40% 40%-50% 50%-60%60%-70% 70%-80% 80%-90% 90%-100%

• If entry is bigger than chip, light is lost at lens • For maximum flux through system air gap should be minimal

25%

50%

75%

100%

0 0.1 0.2 0.3re

lativ

e Fl

ux

thro

ugh

syst

em

air gap [mm]

Cross section at 100% chip size to entry size ratio

20%

40%

60%

80%

80% 120% 160% 200%

rela

tive

Flux

th

roug

h sy

stem

entry size rel to chip size

Cross section at 0.2 mm air gap

Design rules for pre-collimator: optimize system flux

©2017 Lumileds Holding B.V. | 10 February 5, 2018

Gluing collimator directly to the LED surface

• Index match of collimator and converter • Light extraction can be increased • Up to 15% more power can be extracted • But the collimator exit is significantly

increased in lateral direction and so the pixel • Luminance is lower – final optic needs to be

bigger

m=5.66e+009; L max at[-0.1,-0.22]=1.46e+007 cd/m 2̂06981 006 13 007 162 007193 007225 007257

-0.6

0.6

-0.6 0.6m3.8e+009; L max at[-0.02,-0.02]=3.18e+007 cd/m 2̂

006981 00613 007162 007193 007225 007257 00

-0.6

0.6

-0.6 0.6

[cd/m 2̂]min=300000 max=3.2e+007Sum=5.66e+009; L max at[-0.1,-0.22]=1.46e+007 cd/m 2̂

3.47e+006 6.64e+006 9.81e+006 1.3e+007 1.62e+007 1.93e+007 2.25e+007 2.57e+007 2.88e+007

300 kcd/m² 1.300 kcd/m² 3.200 kcd/m²

0.6 mm -0.6 mm 0.6 mm -0.6 mm

0.6 mm

-0.6 mm

©2017 Lumileds Holding B.V. | 11 February 5, 2018

Conclusion and outlook • Automotive headlamps optic will become smaller • The luminance of light source needs to increase

• The same concepts can also be transferred to other pixel shapes e.g. to form a complete low beam

Direct imaging direct attached attached with air gap Systems cost Flux extraction Flux on the road

©2017 Lumileds Holding B.V. | 12 February 5, 2018

Thank you for your attention!

... please be invited for further discussions

[cd]min=0 max=27100flux=171 lm; I max at[1.7,0.1]=27100 cd

2710 5420 8130 10800 13600 16300 19000 21700 24400

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[cd]min=0 max=27000flux=260 lm; I max at[3.1,0.1]=27000 cd

2700 5400 8100 10800 13500 16200 18900 21600 24300

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[cd]min=0 max=29600flux=165 lm; I max at[0.7,-0.1]=29600 cd

40 63 100 160 250 400 630 1000 1600 2500 4000 6300100001600025000

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Automotive matrix systems with improved efficiencyOverviewAdaptive Driving Beam / Matrix: Application OverviewDirect Projection of LEDExample SystemIndirect Projection - Imaging the exit plane of a pre-collimatorDesign rules for pre-collimator: optimize system fluxDesign rules for pre-collimator: optimize system fluxGluing collimator directly to the LED surfaceConclusion and outlook