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In support of the Department of Energy ( DOE) "SuperTruck" program, a group of low energy, high output light emitting diode (LED) lamps were developed for forward lighting. Reduction of the energy needs of the truck by saving fuel and reducing CO₂ emissions are two of the goals of this program. In support of the energy reduction, a retrofit LED headlamp was designed, built and tested. The retrofit headlamp was switched from a halogen bulb to an LED-based system. The LED headlamp requires a new approach in heat management. The use of the LED, which is a 2π source, requires a different strategy in the optics from those used with a 4π source, like a traditional incandescent, halogen, or High Intensity Discharge (HID) light source. A thermal management system is necessary to facilitate the long life of the LED source. A unique method for removing the heat of the LED and maintaining an acceptable temperature was tested and reported.

The study described below investigates several factors in the perception of brightness for LED and incandescent lamps. One of those factors is the difference in voltage drop due to the much lower currents needed to energize LED lamps. We found that these voltage drop differences could significantly affect the actual intensity emitted by the lamps. Another factor studied was the effect of the luminance distribution of the lens on the human perception of brightness. A study was done in which volunteers were asked to make a visual comparison of different lamps against a standard. We found that lamps with multiple bright and dark areas, such as LED lamps, were generally perceived to be brighter than a standard incandescent lamp with a more evenly illuminated lens. The effect of the color difference between LED lamps and incandescent lamps was also investigated. We found no statistically significant effect of color with our limited data, but further investigation is needed.