How to Concentrate LED Light

Light emitting diodes (LEDs) are semiconductor chips that put out light far more efficiently than incandescent or fluorescent bulbs. Add in the potential that LED light sources can last 10 years or more, and you have the nearly perfect light source. But LEDs are inherently non-directional -- they shine light in all directions. Manufacturers make this a little handier for designers by putting light extraction mechanisms within the chip itself. Still, to concentrate the light in a bright cone of illumination, additional optics are required. A particularly useful design is called a non-imaging concentrator, in particular, a type called a compound parabolic concentrator, or CPC.

1
Select Energy Saving Lamp. This can be a single "superbright" white LED, an array of white LEDs, or several colored LEDs all assembled on a single flat carrier.

2
Obtain the specification sheet for the selected LED Strip Light and determine the area of the light emitting region.

3
Determine the desired angular spread of the beam. A smaller angle will be brighter, but cover less area, while a larger angle means a larger area is lit, but less brightly.

4
Calculate the diameter of the output aperture, using the formula that the diameter of the output aperture is equal to the diameter of the active area of the LED determined in Step 2, divided by the sine of the angle determined in Step 3.

For example, if the LED Light area is contained within a diameter of 12 mm and the desired output angle is 15 degrees, the output aperture is 12 mm / sin(15°) = 46 mm.

5
Select a CPC with the input aperture determined in Step 2 and an output aperture as calculated in Step 4.

For the example, the input aperture is 12 mm and the output aperture is 46 mm. Any CPC with those apertures will concentrate more than 95 percent of the light into the output cone. If the desired CPC is not available off-the-shelf, follow the "string method" in the references to define the needed optic.