Euan Morrison, Senior Consultant, Sagentia

In 2006 Brandon Medical, a medical lighting company based in Leeds in the UK approached Sagentia with a specific task: develop a breakthrough LED lighting system for use in operating theatres.

Our first task was a feasibility study. Medical lighting has a few specific, highly demanding requirements. LED manufacturers have made significant advances improving the performance of high brightness, white LEDs, specifically efficacy and absolute lumens output. However, the quality of the color of light emitted by these products, called color rendition, has proved to be a problem. For this reason, tungsten halogen lamps, with their superior color rendering across the full visible spectrum, have tended to be the light source of choice in the medical sector where lumen output and color rendering are critical requirements.

It was clear to us during this initial phase that commercially available LED technology would not meet the demanding requirements laid down by Brandon. Having discounted older approaches, we decided to pursue development of a high quality light source using the highest lumens/watt, high-brightness devices available. To do this, we assembled a small team of scientists with, collectively, 50 years' experience in optical product design. This was an important first step in the innovation process in that we were able to significantly reduce the “desk” research phase and hit the ground running.

Our ability to innovate was also driven, in part, by our ability to take a step sideways. That is, while the process of innovation is important, it is also important we build flexibility into the project so that unplanned scientific discovery and serendipity can contribute.

At the beginning of any project of this nature, there is obviously a need for groundwork. Our past track record in the field certainly helped here but I would also point out that too much theorizing and poring over product datasheets can sometimes be counterproductive because what you see on paper is often not what you see in the laboratory. Had we taken an overly focused “desk based” approach, we would never have achieved the results we did.

We were given some challenging targets by Brandon and had to work hard to hit them. The relationship was open and we held regular meetings. We got to understand their business inside out, and there was weekly, and sometimes more frequent, contact between Sagentia and Brandon's managing director. The deliverables were clear. But even so, the flexible plan suited us. Sticking doggedly to a detailed spreadsheet project plan would have sunk the project, not to mention add significant unnecessary overhead.

While we obviously remained focused on the budgetary constraints and were driven by product specification and project aims, we also maintained a strong sense of scientific curiosity. This, along with a practical “can do” attitude, let us create a breakthrough product in a short time and, in the process, discover an industry first — electronic focusing.

Incorporating commercially available, high brightness, cool-white LEDs, our final solution has color rendering that is as good, if not better, than tungsten halogen. At this moment we are unable to disclose too much design detail because there is a patent application pending on the technology. I would, however, stress that our solution was driven by a fundamental understanding of high brightness, white-LED spectral characteristics and a thorough understanding of color performance, spectral manipulation, and phosphors.

We were mindful of the traps and pitfalls that can arise from an overly theoretical approach. We never lost sight of the fact that it was important to consider how humans in an operating theatre perceive light, rather than constantly strive to emulate a black body. After the event it seems easy to say this, but at the time adopting this approach included a degree of risk. But it paid off. Had we gone down the conventional road, we would never have achieved what we did in the time we did it.

Our work for Brandon Medical resulted in the creation of HD LED. The technology uses state of the art high brightness LEDs and achieves almost perfect color performance. At the same time we have also developed the capabilities to produce complete light engines including:

• Efficient and novel optical designs to ensure beam uniformity
• Programmable electronic drive and control circuitry
• Thermal management and modeling
• Mechanical design
• PCB design