Light Control and Efficacy using Light Guides and Diffusers

Transcription

1 Light Control and Efficacy using Light Guides and Diffusers LEDs 2012 Michael Georgalis, LC Marketing Manager, Fusion Optix October 11, 2012

2 Agenda Introduction What Is Light Control? Improves Application Efficacy Increases Energy Efficiency Impacts the spaces in which we live and work Optical Design at the System Level Light Guides What Is a Light Guide? Light Guide Efficiency Using Light Guides New Design Possibilities Diffusers What is a Diffuser? Diffuser Efficiency at the System Level Using Diffusers Conclusion

3 Introduction Proper light control can help increase the efficacy of a lighting system Reduce unwanted effects such as: Glare Veiling luminance and reflection Light Pollution and trespass Color separation Excessive shadowing Highly efficient and well designed optical components are key to enabling high performance lighting systems Light Guides Diffusers

4 What Is Light Control? Application Efficacy Put the light where you need it- not where you don t Maintain good contrast ratios, reduce glare and provide adequate illumination Illuminate merchandise and provide way finding Provide lighting for tasks such as reading and writing Poorly controlled light has no purpose It is wasted energy Increases cost of ownership of the system both initially and throughout the life of the system Proper light control impacts the spaces in which we live and work Provides atmosphere to a public space Provides safety at work Illuminates our roadways and sidewalks Can impact health and lifestyle

5 Light Guides What is a Light Guide? Uses a combination of Total Internal Reflection (TIR) plus some method of light extraction to create a flat, evenly emitting surface In Critical Angle Transmission, imperfections introduced at the surface increase the number of chances a ray has of hitting a critical angle In TIR, only rays that strike the surface above the critical angle transmit In Frustrated Internal Reflection, a ray will transmit to a medium that has an index different from both air and initial light guide, and can be extracted from that surface in various ways In Critical Angle Transmission, imperfections increase the chances of a ray exiting via the critical angle Many methods to manufacture light guides Laser Etching (Critical angle) Injection Molding (Critical angle) Optical Bonding (Frustrated) Screen Printing (Frustrated) Extraction though frustrated internal reflection relies upon wave transmittance through index mismatch and scattering

6 Light Guide Efficiency Key Factors in Designing an Efficient LED Light Guide for General Lighting 1. Good edge coupling maximizes the amount of light injected into the light guide LED Incident to Light Guide LED must be placed as close as possible to edge of light guide 2. Efficient light extraction requires a well designed scattering pattern Good Edge Coupling Poor Edge Coupling There are many different types, but the principal is the same Pattern varies in density as light propagates to extract more light Incident Light High Intensity Light Low Scattering Density Low Intensity Light High Scattering Density 3. Back surface reflectance plays an important role in uniformity and efficiency Diffuse reflectance with high reflectivity is ideal Diffuse Reflectance (up to 97%) helps backscattered light re-enter the system for extraction

7 Using Light Guides Light Exitance Characteristics Double edge lit light guides will tend to yield a Batwing Style distribution Single Edge Lit light guides will be more Asymmetric Brightness Enhancement Films are typically used to collect and direct light downward to reduce glare and high angle luminance Will also help increase light at the task surface as well Light from both edges will tend to Batwing as it exits Mixing distance and uniformity along the incident edge is a common concern with light guides Light from both edges will be more asymmetric Depends heavily on LED spacing and LED optics Dark spots between LEDs inside the mixing distance Example Brightness Enhancement Films Left: Prism Film Right: Microlens Film

8 New Design Possibilities Attractive and slim luminaires Different Form factors Slim, efficient modules for rapid design cycles and speed to market Wall sconces and fixtures of low profile and unique form factor. Direct/Indirect beam control with infinite design possibilities. 2 x 2 Slim Troffers Slim Linear Pendants

9 Diffusers hide the light source Eliminate hot spots from LED sources Spread out the light from fluorescent tubes and other lamps Help provide more even surface luminance Reduce reflected and high angle glare Holographic Diffuser There are 3 basic types of diffusers Holographic Uses surface patterns to diffuse light through diffraction Volumetric Uses reflective particles suspended inside a material to bounce and guide light out in a controlled fashion Volumetric Diffuser Dies/Bulk Additive Uses a colored inks, additives or dies to absorb light, and relies on a combination of refraction, reflection and diffraction Diffusion with Dies

10 Diffuser Efficiency at the System Level Diffuser Components Interact with the System in Complex Ways Simple Equation for System Efficiency: 100% = Transmission% + Reflection% + Absorption% Diffuser technology and usage must minimize Absorption and Reflection, while still creating the desired lighting effect

11 Using Diffusers Light Characterization FWHM is a measure of diffusion angle Full Width Half Maximum A laser is used to characterize the beam angle Incoherent light is spread to a certain degree, but also diffused proportionate to the angle In general, higher diffusion angle yields higher LED obscuration FWHM Plot for a 6060 Diffuser Half Max Intensity A diffuser is not a lens Diffusion angle does not necessarily translate to beam angle Beam angle is still heavily dependent on the optics and beam angle of the light source behind the diffuser Full Width of distribution at -30⁰ and 30⁰ Polar distribution of a 6060 Diffuser

12 Using Diffusers Reduce unwanted effects such as Glare Color Separation Excessive Shadowing LED Hot Spots LED obscuration depends on Beam angle of the LED LED to LED Spacing LED Distance to the face Generally it is a 1:1.25 ratio of LED spacing to distance to diffuser Reduction of shadows and light blending Not all diffusers are created equal LED obscuration and glare reduction

13 Summary Diffusers and Light Guides are very useful tools to LED lighting adoption There are many different types and applications for both light control devices Abundance of choices can open up a variety of design possibilities When used correctly, and with efficient optical design in mind, LED lighting system designers can: Reduce system energy usage and requirements Lower system initial cost and cost of ownership Provide better lighting for the visual environment Reduce glare, shadowing, color separation and other unwanted effects Even reduce time to market and costs on luminaire design Use of modules and pre-designed components

14 Thank You for more information contact:

15 Photos