All Over But the Funding: Open Hardware Spectrometer Kit

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All Over But the Funding: Open Hardware Spectrometer Kit

Posted by timothy on Friday September 21, 2012 @04:39PM from the what-is-the-exact-color-of-your-van? dept.

New submitter mybluevan writes "The Public Laboratory for Open Technology and Science is putting together an open hardware spectrometer kit on Kickstarter. The kits are built using an HD webcam, discarded DVD, and a couple other odd bits. They've also put together a kit for your smart phone and open-source software for desktop, Android, and iOS. Need to analyze the contents of your coffee, the output of your new grow lights, or a distant star on a budget? Just build your own spectrometer, or pick up the limited edition steampunk version." Besides making cool hardware, they'd like to "build a Wikipedia-style library of open source spectra, and to refine and improve sample collection and analysis techniques. We imagine a kind of 'SHAZAM for materials' which can help to investigate chemical spills, diagnose crop diseases, identify contaminants in household products, and even analyze olive oil, coffee, and homebrew beer."

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Finally! by ColdWetDog · 2012-09-21 16:46 · Score: 4, Funny

A use for all those Windows ME disks!
(You need a DVD as a diffraction grating.)

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Pretty cool ... by RockDoctor · 2012-09-21 16:55 · Score: 5, Interesting

That's an interesting combination of technologies and materials. The basic idea should be workable, but how workable they'd be for material identification given the prevalences of IR filters on (consumer grade) CCD sensors and their relatively low sensitivity ....Identifying spectral lines on a 10-bit sensor is difficult enough. Trying to do it on the 7-8 bits that you get from a (consumer grade) sensor ... is going to be more difficult.
But ... that's an interesting idea. I think that's worth a six-pack worth of funding.
Did I get a first post? Are the trolls and the GNAA spammers asleep? Or, preferably, dieing slowly?

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1. Re:Pretty cool ... by dns_server · 2012-09-21 17:31 · Score: 4, Informative
  
  One of the steps of building the kit is removing the IR filter from the webcam.
2. Re:Pretty cool ... by thegarbz · 2012-09-21 20:19 · Score: 4, Informative
  
  I have converted consumer junk to remove IR sensors on many devices from simple webcams to high end DSLRs. It is simple.
  The hardest part about the process on cameras is working with tiny ribbon cables and sourcing replacement optics if you wish the resulting camera to operate again (since removing the filter completely will result in your camera becoming nearsighted.
  Neither of these are a problem with webcams, and the only issue you're likely to have is that some webcams have their filter glued onto the CCD rather than just placed on and retained with a small amount of pressure from the case.
3. Re:Pretty cool ... by drooling-dog · 2012-09-22 02:45 · Score: 3, Insightful
  
  Trying to do it on the 7-8 bits that you get from a (consumer grade) sensor ... is going to be more difficult.
  True, but if you're imaging the spectrum in two dimensions and summing/averaging vertically (over columns), you'll improve your Signal/Noise ratio considerably (by the square root of the number of vertical pixels, ideally). It wouldn't surprise me if the results were quite decent.
Spectrometers can get you tail! by Anonymous Coward · 2012-09-21 16:57 · Score: 5, Funny

Back when I was in University in 2001 (U Waterloo - Independent Studies) one of the guys found a spectrometer for sale at the weekly physical plant surplus sale for fifty bucks so he just set it up in the IS lounge (which was in the middle of the Psych building) so people could come in and analyze whatever they wanted. It was great for inviting hippies in to charge up crystals with very specific wavelengths to increase harmonic resonance.
I freeken love this. by Anonymous Coward · 2012-09-21 18:11 · Score: 4, Informative

I did my PhD on a topic that involved building some gear related to spectroscopy. A good deal of my work involved cludging together optical parts from seemingly unrelated sources. As such I just love this sort of thing. Unfortunately I have to agree with the above commenter that the precision is just not going to be good enough from a webcam for real chemometric measurement. However with a little more investment the precision could be improved. The real difficulty will come from the need to calibrate the thing. You need to know exactly where each wavelength of interest is centred ** exactly** on the sensor at the time of measurement and this is not a trivial task. Unfortunately proper calibration is so often just not achieved... and that's not even beginning to consider the issues of background/ stay light, Johnson noise etc. I suppose this design could be used for crude detection like the article says rofl.
1. Re:I freeken love this. by Anonymous Coward · 2012-09-21 19:08 · Score: 3, Interesting
  
  What is interesting about talking to researchers about spectrometers, is there is quite a diverse spread of priorities and needs depending on what they are doing. The work I did required a significant amount of time calibrating several aspects of the spectrometer (intensity and response calibration being typically much more annoying than just the position of lines). I would discuss calibration methods with other researchers at conferences, and be thinking, "How primitive, you would barely be able pass an undergrad lab with calibration like that ... oh, that is what is being used for... yeah, there isn't much point in putting more effort into." Yet at the same conference I would pump into people on the other end, who likewise were thinking along the lines of "Oh, you only spend a few hours calibrating a day and didn't take into account all these shifts and broadenings... oh, those are are a tiny fraction of a pixel on your detector."
  There should be room for fun at all levels of capability (ok... more advanced spectrometers may be more tedium than fun...). If this project isn't enough, adding another zero on the price starts to get into various commercial USB spectrometers available. Those are pretty compact and self-contained, although software almost universally sucks. The only negative potentially being a slightly larger influx of crackpots whos discoveries are actually bad calibrations... I've had more than one cold contact along those lines where their spectra were clearly components of air with a slight offset due to bad calibration.
2. Re:I freeken love this. by Anonymous Coward · 2012-09-21 20:25 · Score: 3, Informative
  
  This is the same AC that you replied to. Yeah, every time one little part got changed on our $100,000 units the whole thing had to be re-calibrated for response factors. Then they would break down all the doggam time. Fibres would break or a microchip might come unseated and I wasn't allowed to touch the insides. Not to mention the cost of the reference reflectance tiles being a little bit more than the average bathroom ceramic.
  As for the crackpots and bad calibrations, I thought my head would fall off from shaking it in disbelief at some of the results people touted as 'significant'. Just because data can pass a t-test doesn't mean that R^2=.4 is useful(!) Especially when there's no future proofing the the method. And don't get me started on some classification results. Poor linearity is just not a good excuse to revert to just setting threshold.
3. Re:I freeken love this. by photonic · 2012-09-22 00:02 · Score: 4, Interesting
  
  Optics guy here too. I don't know a lot about spectroscopy, but I had to assemble a spectrometer for my thesis project. It was a pretty fancy imaging spectrometer (main element was a concave mirror and grating combined in one) and used a LN-cooled CCD as the sensor. This was not cheap stuff (~5000eu for the spectrometer and probably > 20000eu for the camera), but the operating principle is exactly the same as the DVD + webcam. The resolution was limited to around 1 nm due to the input slit, not sure if they could improve things by using a slit in this home-built device. I had to calibrate it from scratch, which was actually pretty easy: I borrowed some spectral lamps from the 1st year lab course and also used a HeNe-laser we had laying around. Choose a few of the big lines (which should all be known to better than 1 nm) and for each write down the pixel position of the line on the CCD. Perform low order (e.g. quadratic) polynomial fit and you are done calibrating. I don't know if there are some cheap spectral lamps that you could use at home, there is at least the yellow lines from the Sodium (?) street lightning. I agree with others that the resolution of these home built devices is probably too low to identify materials, but it is for sure a fun project.
  
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Lots of work has been done here by Anonymous Coward · 2012-09-21 18:55 · Score: 5, Informative
Lots of people have been working in this field. The most impressive results are achieved by the astronomy community. link It is possible to produce a home made spectrometer that gets useful results. Some of these are capable of resolution sufficient to identify chemicals. These are sophisticated and often use a peltier cell to cool the CCD in order to reduce noise. link
I did a project whose aim was to produce a cheap spectrometer to match paint colors. link The problems I found were:
1. Cheap webcams are quite noisy
2. Cheap webcams are not at all linear
3. For dark colors, sensitivity is a big problem
4. The spectrum of the light source varies depending on which angle you view it from.
5. Organizing the data is perhaps the biggest problem of all
My own engineering trade-off was sensitivity vs. resolution. To get spectra for dark colored paints, I widened the slit which reduced resolution. That, as far as I could tell, was reasonable because I wasn't trying to identify chemicals and the spectra from paints weren't particularly sharp.
The folks in TFA have a site where people can upload spectra. That's fine but a huge database of spectra is not too useful. The spectra have to be organized somehow. Here's an example. In fact the problem can be quite daunting
First picture on their page failed the idiot test by thegarbz · 2012-09-21 20:23 · Score: 3, Interesting

Really the very first picture they showed of the spectra and the resulting plot on the very top of their kickstarter page has the graph backwards compared to the visible spectra.
With such an epic facepalm I'm surprised they know what a spectrometer is.
Cringe-worthy by threeplustwo · 2012-09-21 23:23 · Score: 3, Informative

I don't want to sound all negative here, but... I don't have a choice, do I? A visible light spectrophotometer will not "detect toxins", no matter how much you try to make it open-source or crowd-sourced. The very concept of identifying compounds by visible light absorbance is very much flawed. Thing is, *most* molecules will not absorb visible or near UV light in a way that is specific enough. Real Chemists (TM) traditionally use the so-called IR fingerprint region for this purpose. This region is from approx. 700 to 1500 cm-1 (about 6 to 20 uM - that is 6000 to 20000 nanometers). A special detector is needed for these wavelengths. The one we have in our lab is cooled with LN2 and costs south of $15K. We also have a UV-Vis spectrophotometer, which has its own purpose. That purpose is not "identifying toxins", or analyzing any unknowns. Now, on to my next point. Identifying molecules is challenging, because they are very, very, very mindbogglingly small. Chemists have been grappling with this challenge for a long time. There are many spectrometric methods out there, including IR and UV-Vis (briefly discussed above), near-IR (900 to ~1800 nm, useful for *some* fingerprinting), and NMR (60-1000 MHz, very informative, bit needs a BIG magnet). Spectral data for many molecules of interest has been compiled into readily accessible databases, and is easily accessible. Some of the databases are proprietary/pay-per-view: https://ftirsearch.com/features/libraries/sea407.htm Some are semi-public: http://riodb01.ibase.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi And some are government/public: http://webbook.nist.gov/chemistry/ The people who started this project do not seem to grasp of the very basic concepts of chemistry, nor did they do any research on the subject. Reading a Wikipedia article on UV-Vis would have been a good start. What is even more disconcerting is that the fundraising effort behind this cardboard spectroscope has been a success. One just has to hope that nobody buys this to screen their food for "toxins", or to teach their kids chemistry.
1. Re:Cringe-worthy by jywarren · 2012-09-22 02:28 · Score: 3, Informative
  
  Hey threeplustwo -- actually there is pretty good literature on laser fluorescence spectroscopy of polyaromatic hydrocarbons in the near-UV to visible range, you should check out some of the Public Lab research notes on the subject: http://publiclaboratory.org/notes/warren/7-18-2012/fluorescence-oil-spill-residue-diverse-spectrometer-use with longer exposures we are able to get a clean read on the fluorescing spectrum. And even in the shorter term (before these harder uses are better developed and more rigorous) there are plenty of applications that are already feasible and useful. Check out the use cases highlighted in the KS Updates -- one guy used it to detect brighteners in laundry detergent, others are using it to empirically test grow lamps in aquaponics, etc etc.
Re:Funding? They're way over! by mybluevan · 2012-09-22 02:44 · Score: 3, Interesting

They've got an interesting stretch goal though: "if we get to $100,000 -- a 'stretch goal'. In the spirit of enabling open collaboration we'd like to make it possible for people to make their own Spectral Workbench-based apps". I'm thinking a Spectral App Platform API would be pretty sweet. "Imagine a "Spectral App Store" where wine enthusiasts can develop their own testing suite for wines, gardeners for grow lamps, and coffee connoisseurs for coffee -- each looking for specific wavelengths or patterns *specific to that application*." They're not that far away from it either.
Re:Blood sugar test? by threeplustwo · 2012-09-22 03:09 · Score: 3, Informative

Non-invasive glucose measurement is one of the holy grails of portable spectrometer design. As it happens, it is most practical using NIR and IR. There are products that will be on the market soon. The kit from TFA won't do it, of course. Spectral resolution is too low, and it looks at all the wrong wavelengths.
Speaking of crude detection by dbIII · 2012-09-22 04:21 · Score: 3, Interesting

As late as the 1990s I used a portable optical spectroscope with a battery to strike an arc and a book full of photos showing where the lines should be for specific elements for alloy identification. I only used it a couple of times and didn't get the hang of it, but apparently some people got useful results from it to the point of estimating percentages of elements instead of just seeing if they were present.