Public Lab Research note

General spectrometer thoughts

by adam-griffith | | 2,445 views | 2 comments |

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On an airplane in Europe, I had a great conversation with Dr. G. Tempea, a laser physicist, regarding spectral resolution.

Design ideas: - could the resolution be increased by using a Blu-Ray DVD as the diffraction grating? - could the resolution be increased by using a camera with a larger sensor? Higher megapixels? - what are the CCD limitations? - could the resolution be increased by increasing the distance between the diffraction grating and the "screen?"

Application idea: - color calibration for computer monitors. Right now, the software to do color matching (for printing, among other things) is expensive and proprietary.


  • could the resolution be increased by using a camera with a larger sensor? Higher megapixels?

I don't think so. The limiting factor of the current design is lack of collimation optics. Because the angle of incidence at the grating isn't constant, the diffracted slit image is always slightly out of focus. The design works well because the camera aperture is so small, but optical resolution is probably the bottleneck.

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Actually i think we've pretty much hit our target for spectral resolution. I'd like a better way to measure it (dave haffner's been chipping away at a method using solar spectra) but it's probably in the 5 nm range, maybe better.

At this point we need to improve our signal to noise ratio, esp. for liquid samples. We can take a baseline and a sample but there's not a lot of dynamic range to tell the difference. This may just be a sample preparation issue -- for example, increasing the amount of sample and using a strong enough light source to shine through it... Check out some of JoshMC's work:

And this one showing a baseline compared to UV reflected/fluoresced off of some makeup:

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