Research and benchmarking have provided a target light level of around 100 Lux (light intensity on the surface) for an approximate range of one square meter. Unfortunately these units mean next to nothing without actually perceiving their impacts on vision. A Cree LED light was tested alongside a candle and a kerosene lantern to compare the performance of LED's with the common lighting methods of the intentioned users. From the graph below, it is apparent that LED's provide can provide significant improvements to the lighting systems currently in place in developing nations.
It was previously determined that for the light system to be successful some degree of light diffusion would be necessary to achieve a comfortable, readable light for the end user. Samples of differently designed lenses were tested for their quality and intensity of light produced. The graph below shows the Lux measured on a flat plane at varying distances away from the lights center.
It is obvious that the Clear Lens provides the most intense light, however it is more intense than is necessary and has a very narrow range. It also creates "hot rings" of light as opposed to a uniform luminance. It was agreed that the Prismatic Lens creates the most appealing light, with a soft homogenous dispersion and a wider range of radiance. As a more visual comparison of the different light conditioning methods we offer the following pictures. From these images one can see the observable differences that the lens, or lack of lens makes on the light distribution.
|LED without lens||LED with concentrating lens||LED with prismatic diffuser||LED with frosted diffuser||LED with ridged diffuser|