One particular area where current LED technology has major problems to overcome is on the delivery of high power efficiency of LED light in conjunction with the quality of the colour produced. The lighting industry is measuring colour rendering capability by the general colour rendering index or Ra, which is an average of CR indices at 8 different wavelengths. It has proved difficult to achieve a value better than 80 for a reasonable cost of the LED-based systems. Another important measure of the quality of light for specialist applications is the specific R9 (colour rendering for strong red). Again it has proved to be very difficult to achieve a value better than 80 in some types of applications like medical lighting where high illuProminance levels are required (˜150klux).
Intrinsically, white HB-LEDs have very poor CR, and current approaches to correct this use multiple phosphors to generate a poor, typically "blue rich" approximation to natural light. These phosphors can seriously reduce the efficiency of the LED, so more LEDs are required to achieve the required light output. In a compact light source this has the effect of increasing the temperature of the LEDs' junctions. This has a very negative consequence on LED's power efficiency that is known to decrease rapidly with junction temperature, typically by 10-50%.
The HERCULES solution will overcome these serious limitations and considerably improve the key success factors needed for general adoption of the LED-based illumination systems: high power efficiency and colour quality.
In order to achieve this, 3 High Technology SMEs, 2 R&D companies and 1 Large Co have come together, each representing the necessary capability at a key point in the supply chain for LED-based lighting equipment. They are led by Brandon Medical Ltd of UK, a SME manufacturer specialising in medical and food LED lighting equipment. Brandon Medical Ltd conceived the HERCULES project, and has driven its creation and development. They are supported in this by GRD Signaletica S.R.L., a designer and supplier of complex optical systems in Italy, and by DTM Cumsa of Spain, specialist in PCB Design & Assembly and Integrator of systems for optical equipment. These 3 high technology European SMEs are existing commercial partners, and their relationship underscores the essential interdependence at the heart of the HERCULES project.
