Creating White Light using LEDs
By Mike Georgalis, LC


Different methods to create white light include chip-level conversion, color mixing, and remote conversion utilizing Fusion Optix ColorTune™ Technology

When it comes to creating white light using LEDs, there are many different methods, all of which have their advantages and disadvantages.  First, the most common and traditional is chip level conversion, where the converting material is integrated directly onto the blue LED die or fills up the LED package volumetrically.  Another method is color mixing using red and white (or mint colored) LEDs, where the LEDs are dimmed and mixed to create the desired color temperature.  A third method is converting the blue light of a diode far away from the chip, which utilizes a mixing chamber and remote optic integrating a converting Phosphor, Fluorescent Dye, Quantum Dot, or Fusion Optix’ proprietary ColorTune™ technology.

This series of Fusion Optix Blog postings will focus on the characteristics of each of these methods to help engineers and designers choose the right conversion method for their system.

Creating White Light Using LEDs Part 1:

Using Remote Wavelength Conversion Optics

How Remote Phosphors, Dyes, Quantum Dots, and Fusion Optix ColorTune™ Technology Impacts Lighting System Performance.

ColorTune™ Technology provides new color control and customization options for the LED lighting system designer

without ColorTune™	with ColorTune™
Example of use of ColorTune™ Technology in 60 deg diffusion lens for use in royal blue LED (450nm) pumped 6" LED downlight application

In a remote wavelength conversion optic, discrete blue LEDs are mounted in an array, and directly illuminate the inside surface of a lens which contains the conversion material.  There are many different types of conversion methods available on the market today including Phosphors, Fluorescent Dyes, Quantum Dots, and Fusion Optix’ proprietary ColorTune™ technology.  Typically, the lens is mounted as part of a mixing chamber several centimeters away and from the LEDs to provide uniform light at the surface.  This method results in a number of optical and thermal effects of which designers should be aware.

1)      Thermally, there will be heat generated on the lens from the wavelength conversion.  Designers should be sure to select materials with high conversion efficacies to minimize this heat which can cause rapid deterioration of the lens substrate or the conversion material itself.  This results in the need for creative heat sinking of the lens- which is often a challenge since lenses are not often made form highly thermal conductive material, and they do not frequently have a very large or tight thermal interface with heat sinking materials.

2)      Remote conversion optics often result in large, diffuse emitting areas, which can pose challenges in down lighting and spot lighting for tight beam control.  Just as there will be losses from the conversion, a designer should be aware of high losses from using a large diffuse source where a point source should be i.e. in a parabolic lens.

3)      Remote conversion methods can offer advantages in binning and color uniformity- which can reduce the overall cost of a system.  Especially when used to control white light exiting from chip level LEDs, using wavelength conversion to more finely tune output during production can allow OEMs to purchase larger, and therefore cheaper, bins of white LEDs 

4)      Aesthetically, many remote conversion technologies have a yellow, green, or red tint when the light engine is off (as opposed to the normal white diffuser or just fully visible CFL or incandescent light source), an unfamiliar effect that some lighting designers have found hard to swallow.  This is a matter of taste, but I am not sold on this is a sole reason to move away from remote conversion technology.

Fusion Optix has developed industry leading wavelength conversion technologies in our ColorTune™ family of optical components.  To take advantage of our optical expertise and highly efficient systems using ColorTune™ optic, visit http://www.fusionoptix.com/solutions/lighting/components/colortune.htm or email us at sales@fusiopnoptix.com.