Dielectric multilayer angular filters for coupling LEDs to thin light guides

Cong Mu; Hugo J. Cornelissen; Florian Bociort; Thomas Liebig

doi:10.1117/12.898156

21 September 2011 Dielectric multilayer angular filters for coupling LEDs to thin light guides

Cong Mu, Hugo J. Cornelissen, Florian Bociort, Thomas Liebig

Proceedings Volume 8170, Illumination Optics II; 81700I (2011) https://doi.org/10.1117/12.898156
Event: SPIE Optical Systems Design, 2011, Marseille, France

Abstract

A new approach is described to couple light from high-power blue LEDs (1x1mm²) into a thin large area light guide using a dielectric interference multilayer as an angular filter. The goal is to achieve large area luminaires such as backlight systems. The method overcomes the drawback of structuring holes or recessions in light guides when using a system with side-emitting LEDs. Several new LED-masking filters have been designed to improve the polarization dependency and coupling efficiency from a previous design that used a stack of inorganic bi-layers. Firstly, a polymeric multilayer manages to increase the coupling efficiency from 52% to 69%. Secondly, a birefringent multilayer filter enables to fully suppress the Brewster's angle effect and to realize identical behaviour for both s- and p- polarized light at large angles. Thirdly, by adding layers of a third inorganic material to the original bi-layer stack with refractive index in between the other two, the transmittance equality is improved and the coupling efficiency can reach up to 63%. A novel angular filter is proposed for a large area planar collimating luminaire. A planar collimator of 2x18o cone angle with scalable and simplified structure is demonstrated. It has a thickness of only 5mm. Compact collimators and planar collimators have been analyzed with the ray tracing software LightTools. Measurements on this collimator filter and optical designs match well with the predicted performance. A new approach to thin film filter design, the so called saddle-point method of global optimization was explored and showed promising initial results. A 40-layer collimator filter with a 30% lower merit function was obtained and is discussed.

Citation Download Citation

Cong Mu, Hugo J. Cornelissen, Florian Bociort, and Thomas Liebig "Dielectric multilayer angular filters for coupling LEDs to thin light guides", Proc. SPIE 8170, Illumination Optics II, 81700I (21 September 2011); https://doi.org/10.1117/12.898156

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available