Slashdot Mirror
Tricorder Project Releases Prototype Open Source 3D Printable Spectrometer
upontheturtlesback writes "As part of developing the next open source science tricorder model, Dr. Peter Jansen of the Tricorder project has released the source to an inexpensive 3D printable visible spectrometer prototype intended for the next science tricorder, but also suitable for Arduino or other embedded electronics projects for science education. With access to a Makerbot-class 3D printer, the spectrometer can be build for about $20 in materials. The source files including hardware schematics, board layouts, Arduino/Processing sketches and example data are available on Thingiverse, and potential contributors are encouraged to help improve the spectrometer design."
Gene Roddenberry saw this coming, and made sure the name was usable without a trademark issue. http://en.memory-alpha.org/wiki/Tricorder "...due to a clause in Gene Roddenberry's contracts with Desilu/Paramount dating back to the time of The Original Series. The clause specified that if any company could find a way to make one of the fictional devices actually work, then they would have the right to use the name."
There've been open source spectrometers for smartphones and webcams on Thingiverse and PublicLab.org for a few years: http://thingiverse.com/thing:49934, http://thingiverse.com/thing:125428
http://publiclab.org/wiki/spectrometer
And a papercraft spectrometer for $10: http://publiclab.org/wiki/foldable-spec
The new project looks great -- I just hope the new project intends compatibility with the growing open/crowdsourced spectral library at http://spectralworkbench.org/ -- because the more data in there, the easier matching becomes.
Welcome to the open spectrometry movement!
I realize that not everyone is familiar with spectroscopy, so I'll try and help outline the contributions that this project makes -- which are centrally in terms of size and cost.
Useful chemical classification can occur with an instrument containing as few as one spectral channel (ie. a narrow band filter). Colorimeters use three spectral channels, like a conventional camera, for determining the concentration of analytes. The similarity in the spectral features between the compounds you're analyzing for a given application determines the spectral resolution one needs to meet that performance. In some cases you may need 10, 100, or 1000 spectral channels, and in other applications, many more.
The architecture used for many contemporary slit spectrometers was invented by Fraunhofer in the early 19th century using a diffraction grating, a slit, and some relay optics. There are different architectures that allow you to improve upon this design (like coded aperture spectroscopy, to increase the SNR), or access different spectral regions (such as interferometer based designs for different wavelengths, like FTIR for infrared spectroscopy), but unless you're getting really fancy for visible spectroscopy, the Fraunhofer architecture is the familiar 200-year old architecture that many folks build in a highschool science class, and these work rather well for a variety of applications. This spectrometer also uses (more or less) this architecture.
Spectrometers are generally big, and many are bench-sized instruments. Currently, an inexpensive visible range (350-1000nm) usb lab spectrometer with around 500 spectral channels is around $2k, and about the size of a bunch of iPhone's stacked ontop of each other -- so it's not at all suitable for being embedded in a tiny handheld device (like an open source science tricorder). Of the commercial mini-spectrometers I'm aware of, this open mini spectrometer has a similar number of detector pixels, a similar spectral range, and a similar size. The current spectrograph on the open mini spectrometer appears to have a FWHM that's about two times worse than these systems, and it's SNR is certainly lower, but it also costs an order of magnitude less. It's also completely open, and you're free to improve the spectrograph design to increase the performance, or potentially use signal processing techniques to increase it's effective resolution.
It's not easy to compare this to something like an iPhone with a spectrometer attachment, because it's intended to be an inexpensive but complete spectrometer module rather than a complete spectrometer with a display, so the audience is different and it aims to enable makers and young scientists to build instruments and incorporate these devices in places they otherwise wouldn't be able to. But if you want to do the comparison, I'm not sure what the FWHM and effective spectral resolution would be for an iPhone with a spectrograph attachment (it depends on the spectrograph you're using, of course), but just the phone without a huge spectrograph hanging off of it is about 10 times larger than this, and for the same price you could probably put 50 of these together.