Public Lab Research note


Quantifying reflector brightness assistance

by warren | October 17, 2014 18:03 | 58 views | 1 comments | #11272 | 58 views | 1 comments | #11272 17 Oct 18:03

Read more: publiclab.org/n/11272


What I want to do

At the New Orleans oil testing meetup, started using reflective foil mylar (like the inside of a potato chip bag, as @stevie is holding in the photo below) to increase brightness of fluorescence spectra, since we've had some trouble getting them to be bright enough for some webcams. If we increase brightness, we might also have a larger area of fluorescence and not need to worry as much about alignment.

IMG_20140731_210411.jpg

My attempt and results

Started this in the comments of this research note, where I wanted to try out foil reflectors.

The lead image (also at https://spectralworkbench.org/analyze/spectrum/35937) shows just a photo of a cuvette, where I placed a strip of adhesive-backed foil on the back of a cuvette, but one thin enough to only affect the middle of the beam path. We should (and do, whoopee!) see a distinct sawtooth "notch" of higher brightness in the middle. I want to know how much this helps.

The red channel shows a ~25% increase in brightness; the green, more like 15-20%, but the blue is clipping in this image. I can try again, but we're talking about double-digit increases, which is super, and much more than I expected.

Questions and next steps

I think this is enough to say that we should essentially always use foil reflectors. @mathew was also seeing clipping in a lot of spectra, which is the opposite problem. But we can always filter out some of the light; that's not a hard limit. I'm just glad we have a way to increase brightness now too.

Why I'm interested

Well, basically the more control we have over brightness, the better we can get a good signal-to-noise ratio and good dynamic range for our tests. A tiny square of foil is an easy addition!

IMG_20140911_160739.jpg


1 Comments

Snap. We should have a brainstorming session on cheap forms of reflective stuff!

My list so far has been: -Alufoil. (Too easy to crease - which lowers light intensity) -Takeaway containers. (Sometimes can be embossed, which means the same issue as above occurs) -Old tins. (Sometimes have internal lining - plus difficult to bend and shape) -Empty coffee bean packets. (Perfect, depends on the packet though. Some are lined with plastic, others use shiny stuff like you show above)

Great! Now I have an excuse to get my partner to buy me a packet of crisps!!! ;)

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