I’m working on a project that will include using LEDs as light sensors, and one of the first tasks is to learn a bit more about the wavelengths of light that are emitted by an array of LEDs. Since I’ve recently created a Mathematica interface to an Ocean Optics spectrometer (on a Raspberry Pi, naturally), the first task was pretty straightforward.
Looking at the three spectra from the RGB LED, I noticed that not all of the irradiation looks like a “normal” Gaussian shape. I tried fitting each of the spectra to a skewed normal distribution to get the maximum wavelength, the bandwidth and the skewness, which is a measure of how close to a normal distribution the spectrum is.
Note how the blue LED is more symmetric than the red or green ones. It has a profile that most closely represents a normal distribution, which is indicated by a skewness of zero in the table below. Why is this information useful? No idea. I just wanted to do it and was having fun playing with my Raspberry pi-controlled spectrometer.
Here’s the data for the remaining LEDS (with the exception of the white one, which wouldn’t fit nicely to a normal distribution. Note that the intensity in the plot below doesn’t mean anything, since I adjusted the spectrometers integration time for each of the LEDs in order to get the highest intensity possible. You’ll note that the IR LED does not have a very strong feature even though I was close to the maximum integration time on my spectrometer.
…and here’s the metrics for these LEDs. The values in parentheses are the Adafruit product numbers for the LEDs.