Comparison of molded plastics Fresnel lenses with molded plastics nonimaging "cones" for LED collimation

We have investigated the light collection and collimation properties of both Fresnel lenses and the nonimaging (TIR) “cones” typically used with LEDs. We have measured the integrated light output and its spatial distribution, and we have also measured the sensitivity of these two parameters to misalignment between the optic and the LED. We find that for a given distance from the LED to the front of the optic, a Fresnel lens can produce a narrower (better collimated) beam than can a nonimaging “cone.” Various design and manufacturability factors must be weighed when determining which solution to choose for a given illumination problem, and some of these are discussed.