Public Lab Research note

This is an attempt to replicate an activity.

Built the entry level paperkit

by Swede2 | January 07, 2018 16:22 07 Jan 16:22 | #15472 | #15472

I built the entry level, paper-foldable spectrophotometer just before New Years. The experience I had and the lessons I learned are below.

1.) First, I tried it out of paper. That is super easy because you just have to print out the form, cut and then fold, but the paper is not thick enough to block out extraneous light. I was able to improve it by wrapping the front of the small box with black electrician's tape. It worked . . . sort of.
2.) Getting the aperature right is a big deal and not that easy to do. I ended up 3d printing an appoximate aperature and then using electrician's tape to make the aperature closer to the 0.4mm that is suggested. Unfortunately, my 3d printer is not accurate enough to just print a small slot like that.
3.) I'm getting spectral images from the CFL lights but the resolution is no where near the 1 nm that is mentioned as possible.

Therefore, I'm ready to buy the desktop reference design with the web cam and the aperature kit. I think that will be easier to use (it is hard to hold the box onto your smartphone camera while snapping a picture) and hope that it will be more precise.


I'm adding one more discovery.

I had been using a CD-R for the window because I have plenty of scrap versions of them. I decided to sacrifice a DVD-R after discovering that the pitch is finer (740nm for a DVD-R versus 1.6um for a CD-R).

Sure enough, the resolution was better. Compare "CFLCal6DVD" another calibration with the CD-R as the window such as "CFLCal5" or "CFLCal4". More definition, better resolution with the DVD-R.

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Your image is way over exposed. You should be aware that this is an entry level project. The desk top is also used to stimulate discussion. Please check one of my previous notes which describes a way to minimise light leaked into the sensor.

Best Regards. Stef

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There may also be some mis-auto-focusing by the smartphone camera. Over-exposure too, but also try getting the focus to lock on the more detailed lines of the spectrum and your crispness may improve a bit.

Looks like a good build, though! Glad to hear it was pretty easy and thanks for the feedback and troubleshooting!

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By the way, thanks for mentioning the use of electrical tape. Applying that suggestion took my attempt to build one from nearly worthless to vaguely useful. I also suffer from focus and overexposure problems, but I was pretty happy with the result given that it's made from random things I just keep around the house. Just wish I could find cameras that extend into the ~1100nm realm.

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Ooh, good question on the camera! Post a question at #spectrometry and i know people have tried a lot of cameras!

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Oh, that's great. I'm glad the comment was useful. If you are satisfied with your hand built version, I'd recommend ordering the desktop version. I bought it along with an aperature kit. Since you can monitor the exposure real-time, in Spectral Workbench, you can solve the over-exposure problem that is difficult to solve if you are snapping pictures with a smart phone. Last weekend, I got spectra of a 650nm laser pointer, the sunny winter sky, and tap water with different colored drops in it. I haven't figured out what to do with them . . . just trying to figure out the sensitivity and how to read the output. What are you looking to do in the infrared (1100nm)?

Is this a question? Click here to post it to the Questions page.

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I never really knew much about spectrometers (and still don't) but I happened on an article about green laser pointers which mentioned that a number of green laser pointers emit dangerous amounts of infrared radiation at double the frequency of the laser -- in my case, presumably at 1064 nm.

I was curious if my laser pointer fell into that category, and am still trying to figure out a cost effective way to see if the laser is emitting in the near IR spectrum. I have no real reason for this project, other than to satisfy my curiosity.

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