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FEATURE OPTICAL MODELLING Tracing the rays


The use of optical modelling software for freeform design has increased in recent years, mainly due to the rise of LEDs. Jessica Rowbury looks at what’s involved in designing an LED lighting system through the use of software


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EDS are replacing traditional light sources because they are cheaper and more energy-efficient, but also because they can be very stylish. The


combination of growing numbers of LEDs and increasing demand for better aesthetics has led to a rise in the use of optical modelling software, so that LEDs can be ‘tailor-made’ for specific applications. But, as the hardware evolves, the software needs to catch up and improve its ease- of-use, processing speed, and standardisation. The LED market has been driven in part by


government requirements for more energy- efficient lighting in homes, offices, and city streets. ‘In the USA, they have outlawed 60 and 100W incandescent light bulbs, and the government is really pushing people to buy LED lamps,’ explained Rich Pfisterer, CEO of Photon Engineering. And, a desire for sleek, attractive lighting has heightened the demand. ‘Aesthetics is becoming more and more of a differentiator in the market,’ added Pfisterer. ‘The drive to make chic lighting for housing is driving the price of LEDs down − so there is more opportunity to use them in cars, architecturally, and for room lighting.’


The optical properties of LEDs mean that, unlike other light sources, the surfaces that the light interacts with can be designed in such a way that the beam pattern can be controlled. ‘One of the great strengths of the LED is that it


18 ELECTRO OPTICS l APRIL 2014 Ray tracing simulation for an LED light source produced within Photon Engineering’s FRED software


is a very small source compared to other light sources − and, because of that, it can be shaped very efficiently,’ according to Dr Jake Jacobsen, technical marketing manager of the Optical Solutions Group at Synopsys. ‘You can really shape the light in a way that you just couldn’t with other types of sources.’ As the hardware has evolved, the LED market has driven the use of optical modelling software for freeform design. ‘Many software vendors have added the capability to design 3D freeform optics specifically for LED emission,’ said Michael Gauvin, vice president


of applications, including street lighting, room lighting, and headlamps for cars.’


The surfaces that the light interacts with can be designed so that the beam pattern can be controlled


of sales and marketing at Lambda Research. This freeform design capability is being exploited for many lighting applications. ‘One of the big trends in the industry right now is to work on freeform surfaces,’ added Dr Bill Cassarly, senior scientist of illumination engineering at the optical solutions group at Synopsys. ‘It’s used in lots


The first stage in designing an optical system is to assemble the requirements, which can be fairly general, or in some cases, very specific. ‘With streetlamps you don’t want − or it’s not allowed − for you to put light into certain areas,’ explained Gauvin. ‘For instance, you do not want light going into an oncoming driver’s field of view which creates glare problems, or behind street lamps situated on roadways that create unwanted light into residences and buildings. There are specific street lamp standards that say


where you can and cannot put light.’ Once the requirements and regulations are known, it is important to decipher whether the proposed lighting system is feasible, according to Synopsys’ Jacobsen. In some cases, it is not: ‘A lot of times, customers come in and say: “I want a small optic that collimates the light from a rather


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Photon Engineering


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