An Investigation Into LED Multiplexing and Homogenisation Presenter : Kevin Rogers Authors: Kevin Rogers, Nigel Copner, Paul Driscoll, Ron Yandle, Peter Excell, Kang Li A Guiding Light In Innovation

Contents Introduce multiplexing methodology Introduce Cymtec’s Neolight LED Multiplexer Building an optical model of the Neolight LED multiplexer Analysis of the model Optimisation of the model Analysis of optimised model

A Guiding Light In Innovation Why Multiplex? LEDs are a very efficient light source with long lifetimes Narrow emission spectrum of LEDs only allows discrete colours General lighting and illumination requires white light Combining multiple wavelengths can produce white light which allows LEDs to penetrate several markets

A Guiding Light In Innovation Producing White Light with LEDs

A Guiding Light In Innovation Neolight LED Multiplexor Integrates collimation, colour mixing and homogenisation into a single compact package High Luminous flux High efficiency Preserves etendue Dynamic colour variation

A Guiding Light In Innovation Neolight LED Multiplexor Tapered Collimators Short Pass Dichroic Filters Long Pass Dichroic Filters Light Pipe Homogeniser

Neolight LED Multiplexor – Building an Optical Model - Sources A Guiding Light In Innovation LEDs used are Luminus PT-120 Top-down modelling approach using Zemax source radial component Source dimensions, normalised far field angular distribution, total luminous flux, and normalised spectral data inputted into non- sequential component editor from datasheet

Neolight LED Multiplexor – Building an Optical Model – Mechanical Design A Guiding Light In Innovation Imported CAD model Glass defined from Zemax glass catalogue Relatively simple shapes so little discrepancy between imported CAD and Zemax generated objects

Neolight LED Multiplexor – Building an Optical Model – Optical Coatings A Guiding Light In Innovation Several optical coatings utilised including high-reflection, anti- reflection, long pass filters, short pass filters Zemax has several methods of defining coatings including ideal coatings, actual coating recipe, and coefficients of reflection and transmission

Neolight LED Multiplexor – Running an Optical Model A Guiding Light In Innovation Total Luminous flux (lm) Illuminance Average (lm/cm^2) Max illuminance (lm/cm^2) Min illuminance (lm/cm^2) Illuminance uniformity (%) X chromaticity coordinate Y chromaticity coordinate

A Guiding Light In Innovation Neolight LED Multiplexor – Optimisation ColourX coordinateY coordinate Red Green Blue Using LED XY chromaticity coordinates an illustration of achievable colour gamut is possible By varying the drive currents of the LEDs and therefore the Luminous flux, nearly all CCTs and a range of colours available

A Guiding Light In Innovation Neolight LED Multiplexor – Optimisation Using Zemax optimisation algorithms it is possible to target specific XY chromaticity coordinates and hence specific CCTs A commonly used CCT is 6504K of the CIE D65 standard illuminant which is X = and Y = These can be set as targets in the merit function editor, the luminous flux for each LED set as variables and optimisation carried out

A Guiding Light In Innovation Neolight LED Multiplexor – Optimisation Red (lm)Green (lm)Blue (lm) LED Luminous flux required from each LED to reach 6504K, produced from optimisation: Gives rise to following ratio: Red : Green : Blue Within confines of LED operation: Red (lm)Green (lm)Blue (lm)

A Guiding Light In Innovation Neolight LED Multiplexor – Evaluation Total Luminous flux (lm) Illuminance Average (lm/cm^2) Max Illuminance (lm/cm^2) Min Illuminance (lm/cm^2) Illuminance uniformity (%) Average X chromaticity coordinate Average Y chromaticity coordinate Min X chromaticity coordinate Max X chromaticity coordinate Min Y chromaticity coordinate Max Y chromaticity coordinate Av CCT (K) CCT Variation (K)

A Guiding Light In Innovation Closing Remarks and References Demonstrated using an optical model a method of producing a colour changeable small area source with an excess of 2000lm This unlocks many new applications with etendue restrictive systems, and pushes the boundaries of systems already utilising LED technologies Experimental results to be published at Photonics West 2011