Researchers of the University of Twente, Eindhoven University of Technology and Signify have come up with an analytical model that predicts the color point of the white LED for any combination of design parameters. Until now, this important LED characteristic had to be determined by a combination of measurements and simulations. The model reduces the time to design a white LED.
A white LED is essentially a blue LED with a layer of phosphors on it, which convert some of the blue light to red, yellow and green. The color point of white light reflects which color(s) come(s) through most. The bluer the ‘colder’ the light, for example, whereas more red tones are experienced as ‘warmer’. Different applications ask for different color points.
The color point is determined by the nature of the blue light (which is partially transmitted), the thickness of the phosphor layer, the concentration of phosphor particles and several optical parameters like the type of lens mounted on the LED. Until recently, the lighting industry didn’t have a way to calculate the color point from these parameters.
But now it does. “Using our analytic approach, we’re able to find the color point based on the relevant parameters. And in reverse as well: with a color point as a starting point, we can find the relevant parameters,” says UT researcher Willem Vos. “A model based on the physical parameters is a true step forward. We can easily produce a lookup table based on the conditions,” adds Wilbert IJzerman of the TUE and Signify.