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Micro-optical beam-shaper for tailoring light emission from OLEDs

: Flämmich, M.; Michaelis, D.; Danz, N.; Wächter, C.; Dannberg, P.; Bräuer, A.


Thienpont, H. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Micro-Optics 2010 : 12.-16.4.2010, Brussels, Belgium
Bellingham, WA: SPIE, 2010 (Proceedings of SPIE 7716)
ISBN: 978-0-8194-8189-4
Paper 771616
Conferecne "Micro-Optics" <2010, Brussels>
Conference Paper
Fraunhofer IOF ()
organic light emitting diode; area light source; beam-shaping; light extraction; ray tracing; micro-optical element; micro-lens array

In this contribution, we show that micro-optical elements are well suited to exploit the potential of organic lightemitting diode (OLED) based light sources. They may not only increase the OLED efficiency significantly but also enable for tailoring the common Lambertian-like emission pattern of OLEDs in order to reach desired light distributions corresponding to application demands.
An OLED beam-shaping scheme is demonstrated utilizing thin micro-optical arrays where each channel consists of a halfball lens and an adapted reflective/absorptive aperture. The combination of (a) light recycling, (b) distorted and arrayed imaging of the apertures, and (c) potential substrate-mode-outcoupling allows for efficient tailoring the light emission pattern of large area OLEDs. By means of such a beam-shaping concept, several different illumination patterns (e.g. circular, triangular beams or even more complex light distributions like letters) with various divergence angles below ± 40° are demonstrated. Furthermore, a reduction of the divergence angle down to about ± 10° accompanied by a stray light level minimization to <1 % at larger angles is presented. In either case, intensity enhancements by a factor of >2 can be realized while the thickness of the optics remains below 2 mm.