I ordered a DIY spectroscopy kit from public-lab, however don't have access to a halogen lamp to calibrate the wavelengths.

I'm wondering if it would somehow be possible to calibrate the wavelength using the iPhone camera light?


2 Answers 2


According to the site, wavelength calibration is meant to be done with a compact fluorescent lamp (for the mercury lines), but at the bottom there's a tool for calibrating using any two known wavelengths. If the LED on the phone has two distinct lines that you can calibrate against, it may work, but something like a pair of monochromatic LEDs or laser pointers (say one blue and one red) or something will probably work better.

  • $\begingroup$ Just out of curiosity, if I have a band of red/blue/green, would these wavelengths be fixed for the standard wavelengths of red/blue/green, regardless of the incoming light source? Could I then calibrate with two of these colours? $\endgroup$
    – user4779
    Feb 13, 2015 at 3:48
  • $\begingroup$ Only if you know exactly what the wavelength is. The nice thing about LEDs is that you can look at the datasheet and it'll tell you the maximum and the tolerance. $\endgroup$ Feb 14, 2015 at 5:10

I don't know about the exact calibration setup of the spectroscopy kit, which sounds interesting, but i doubt that the cell phone lamp will be useful here.

Both lamps seem to emit while light, but both the ways how light is generated, as well as the emission spectra of cell phone camera light and a halogen lamp are rather different.

Cell phone camera lights are typically blue light emitting diodes partly covered with one one more phosphors (not, it isn't phosphorous) which absorb the blue light and emit yellow (or orange) light. The emission spectrum of the devices consists of some distict bands.

Halogen lamps are tuned heavily incandescent lamps with a tungsten filament. Here, the spectrum is more similar to a black body radiator.

Consequently, I suggest to get a halogen lamp. A cheap 12V lamp with a socket (often GU4) and a power supply will probably work fine.

"Naked lamps" do emit in the UV too; Lamps with a reflector to provide a collimated beam have an additional glas cover that shield the UV part. Check the manual of the spectrometer kit for some directions.

  • $\begingroup$ My dad told me about building a fluorescent detector with a halogen headlamp bulb from a car when he was in grad school 30 years ago. I assume a headlight bulb would be an ok source? I know you can get a replacement socket with wires you can strip and solder, and a 9V battery with 2 AA batteries in series would provide 12V to light it up, but I don't know how long it would run. $\endgroup$
    – user137
    Feb 12, 2015 at 16:01
  • $\begingroup$ I'm not a spectroscopist but I wonder if wavelength calibration is all that is required (not intensity calibration), isn't the fact that cell phone camera lights emit in "some distinct" bands a good thing? If you can figure out precisely what wavelength those bands are, doesn't that permit calibration? $\endgroup$
    – Curt F.
    Feb 12, 2015 at 16:44
  • $\begingroup$ @CurtF. Intensity calibration would probably be included in the process of blanking the spectrophotometer and creating a calibration curve for your current compound of interest. $\endgroup$
    – user137
    Feb 12, 2015 at 18:18
  • $\begingroup$ Interesting. If I bought a "naked lamp" for the UV, would a small cheap usb webcam be able to pick this up, or would I need a special one? $\endgroup$
    – user4779
    Feb 13, 2015 at 3:46

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