Re:Inexpensive chip-based device may transform spectrometry
by danielvf on Friday October 26, 2018 @09:06AM
(#18308791)
Summing RGB sensors doesn't really work the way you would think because each sensor is actually sensitive to a very broad range of wavelengths, some of which affect it more, and some of which affect it less. Unless you know what your red sensor reads with X amount of illumination at 635nm vs 670nm, you are going to get very bumpy results on even a blackbody.
There's still some of variation in colored LEDs. (and unless you are paying big bucks, a ton of variation on white LEDs. What most home LED bulb companies do is buy a bunch of off color white LEDs and sort them per light so that the badness sort of evens out to something close to okay.)
Re:Inexpensive chip-based device may transform spectrometry
by analog31 on Friday October 26, 2018 @06:00PM
(#18313007)
Indeed, once the sensors are summed, the intensity scale of the spectrometer still needs to be calibrated using something like a blackbody source.
But even monochrome sensors have lumpy response.
I'm only suggesting to use colored LED's as crude wavelength references and a blackbody as an intensity versus wavelength reference, for something that's good enough for home experimentation within reason.
On the other hand, you could achieve pretty decent "monochrome" behavior by just summing the three color channels of a RGB camera, at least in the visible range of wavelengths. With that issue settled, you could figure out a way to produce a rainbow spectrum by hook or crook, such as a cheap prism from Surplus Shed (if they have one in stock -- they are a great source of bargain optics) and some lenses. For intensity calibration, a plain tungsten lamp would suffice for home experimentation. They operate very close to their rated color temperature. For wavelength calibration, one idea is to see if there are useful visible lines in the mercury emission spectrum (don't remember) which are emitted by a regular fluorescent lamp. Also, colored LED's at room temperature run pretty close to their rated peak wavelengths.