10 ms·

Inexpensive chip-based device may transform spectrometry

83 points by charlysl 8y ago

rfinney 8y ago
Open access Nature Communications paper : https://www.nature.com/articles/s41467-018-06773-2 https://www.nature.com/articles/s41467-018-06773-2 High-performance and scalable on-chip digital Fourier transform spectroscopy Here we demonstrate a transformative on-chip digital Fourier transform spectrometer that acquires high-resolution spectra via time-domain modulation of a reconfigurable Mach-Zehnder interferometer. The device, fabricated and packaged using industry-standard silicon photonics technology, claims the multiplex advantage to dramatically boost the signal-to-noise ratio and unprecedented scalability capable of addressing exponentially increasing numbers of spectral channels.
starshadowx2 8y ago
FTIR devices seem to cost around 50000 right now, would this be something that would lower that cost? FTIRs are definitely in demand with harm reduction groups both in cities and for drug testing at music festivals. If we could get these at lower costs it would honestly save lives.
- mediaman 8y ago
  How is FTIR used for drug testing? Is it used to test for contamination based on the spectrum profile?
  - nikmobi 8y ago
    Not an expert, but if you can test for contamination why wouldn't you be able to test for the drugs themselves? Raman spectroscopy[1] is one that I know of that is frequently used to determine chemical composition. Spectroscopy in general still amazes me. [1] https://en.wikipedia.org/wiki/Raman_spectroscopy#Applications https://en.wikipedia.org/wiki/Raman_spectroscopy#Application...
  - dejv 8y ago
    Peaks of each chemical is unique so you can scan database of known chemicals and compare. You can even measure the amounts of various chemicals in solution, but that would require complex calibration. In this case you are basically writing ML system that is trying to fit various peak heights/areas to amount of compound.
  - starshadowx2 8y ago
    This doesn't really explain how but it does talk about the uses of an FTIR in a drug checking, harm reduction situation. https://globalnews.ca/news/4540315/new-drug-checking-machines-vancouver/?fbclid=IwAR24ezHkDlU7Ft7GD3fFrk2npDk-cgtHvrJkl78NvjwenHY-k0z8-Tg_v1o https://globalnews.ca/news/4540315/new-drug-checking-machine...
- somebodynew 8y ago
  A very simple refractive IR spectrometer is possible for under $1000 if you can live with 2-10μm range. I don't have a full write up yet but the basic design is an MLX90614 thermopile scanning infrared light generated by nichrome wire, focused with a zinc selenide CO2 laser lens (the ones without an AR coating are better but harder to find), and separated by a silicon prism which is essentially just a chunk of a broken silicon boule. It's very difficult to find transparent materials in this wavelength range, especially when you're limited to cheap goods mass-produced for some other application. Signal noise and speed will be much worse than a modern FTIR but it's usable when calibrated.
  - dejv 8y ago
    It might work for qualitative measurement (what is the solution you are measuring), but this kind of instrument will not be performant enough to do qualitative analysis. Once you want to measure amounts the FTIR is probably the only way to go, especially with more complex solutions.
- dejv 8y ago
  There is Neospectra [1] company that produces FTIR-on-chip modules. Performance is not that great compared to research grade FTIR, but the price is a lot less. [1] https://www.neospectra.com/ https://www.neospectra.com/
analog31 8y ago
I help design spectrometers. Every once in a while, a new idea for a mini spectrometer floats across my desk. Many of the ideas are based on silicon IC fabrication technologies or micromachining. The drawback is the same in every case: The sheer amount of light that can pass through the optics of a spectrometer depends on its size. This in turn affects what signal-to-noise ratio can be realized. These devices are certainly interesting, and performance is relative to requirements, so a novel application could make use of whatever sensitivity is made available by a particular device. But a tiny spectrometer isn't likely to be a drop-in replacement for a big one unless the big one is overkill for its application. Still, I read these articles with interest, because my "size matters" rule is somewhat ad hoc, and there might be a factor that I'm overlooking.
- DenisM 8y ago
  Maybe you can help me with this... I want to measure the quality of light in my home and office. CRI seems to be the right metric, and it seems that the cheapest option is a $2000 (Sekonic) hand-held device. Are there cheaper options? I don't need much precision, just enough info to understand that these lightbulbs over here are much better than those other lightbulbs over there. I am puzzled as to why it has to be so expensive. I would think one can put a prism, project the light over the surface of a black-and-white CCD sensor and measure the light intensity along the length, giving a reasonably good idea of how much energy is deposited into each wavelength range. I feel like one of these can be made for $20 in parts?
  - milleramp 8y ago
    This spectrometer is inexpensive: https://publiclab.org/wiki/desktop-spectrometry-kit-3-0 https://publiclab.org/wiki/desktop-spectrometry-kit-3-0 The problem is calibration, you would need to calibrate with sources like lasers or fluorescent light with known spectral peaks. Then you could use the spectrum to calculate CRI. You are just calculating cri (which has its own issues), so even with a crude device some spectral error is ok.
  - danielvf 8y ago
    You can get a plastic DSLR camera body cap for less than 50 cents each (ebay from China). This cap goes where the lens would attach the camera when you don't have a lens on. Sometimes I cut a hole in the center of a cap and make really hacky camera "lenses" for fun. You could put a prism on the outside of a cap. You would then need to calibrate your new spectra-cam on something with a known radiation (usually just find a good blackbody radiator.) You can't just convert to black and white without calibration because the RGB sensors on the camera are going to have their own sensitivity to different wavelengths. This would be an awesome project! -- I write firmware for high end professional LED lights, and have a $3K spectrometer on my desk. Here are things I've learned: 1. CRI is simply a bad formula to judge light quality overall and gives almost meaningless results at lower color temperature levels. 2. There are lots of fantastic python modules for working with spectrograph and light data. 3. One awful thing cheap LED lights do is blink slowly to control their voltage. This is at least as bad a poor CRI for aggravating your eyes. (Sometimes you can see this just by using slow motion video on your phone)
softgrow 8y ago
If you are wanting an inexpensive spectrometer, then Public Labs has instructions on how to build one using an old DVD as a diffraction grating https://publiclab.org/wiki/spectrometry https://publiclab.org/wiki/spectrometry I got a kit as a present and really enjoyed it.
- dejv 8y ago
  It depends on what you want this spectrometer to do. Public Lab spectrometer is interesting and cheap, but the performance is very very limited. If you need something better you can search eBay for used (scanning) monochromators. Next step is to check Ocean Optics or Hamamatsu catalogs: they have good line of products, but those are in 1000 USD+ range.
keithnz 8y ago
This is cool, a while back when I used to do fruit sorting machines, we used a spectrometer for working out the sugar content of fruit. Nothing quite like setting up the machine to siphon off the biggest sweetest peach you can find at one of the largest peach farms in the world. best. peach. ever. :)

83 points by charlysl 8y ago

Open access Nature Communications paper : https://www.nature.com/articles/s41467-018-06773-2 https://www.nature.com/articles/s41467-018-06773-2 High-performance and scalable on-chip digital Fourier transform spectroscopy Here we demonstrate a transformative on-chip digital Fourier transform spectrometer that acquires high-resolution spectra via time-domain modulation of a reconfigurable Mach-Zehnder interferometer. The device, fabricated and packaged using industry-standard silicon photonics technology, claims the multiplex advantage to dramatically boost the signal-to-noise ratio and unprecedented scalability capable of addressing exponentially increasing numbers of spectral channels.

starshadowx2 8y ago

FTIR devices seem to cost around 50000 right now, would this be something that would lower that cost? FTIRs are definitely in demand with harm reduction groups both in cities and for drug testing at music festivals. If we could get these at lower costs it would honestly save lives.

mediaman 8y ago
How is FTIR used for drug testing? Is it used to test for contamination based on the spectrum profile?
- nikmobi 8y ago
  Not an expert, but if you can test for contamination why wouldn't you be able to test for the drugs themselves? Raman spectroscopy[1] is one that I know of that is frequently used to determine chemical composition. Spectroscopy in general still amazes me. [1] https://en.wikipedia.org/wiki/Raman_spectroscopy#Applications https://en.wikipedia.org/wiki/Raman_spectroscopy#Application...
- dejv 8y ago
  Peaks of each chemical is unique so you can scan database of known chemicals and compare. You can even measure the amounts of various chemicals in solution, but that would require complex calibration. In this case you are basically writing ML system that is trying to fit various peak heights/areas to amount of compound.
- starshadowx2 8y ago
  This doesn't really explain how but it does talk about the uses of an FTIR in a drug checking, harm reduction situation. https://globalnews.ca/news/4540315/new-drug-checking-machines-vancouver/?fbclid=IwAR24ezHkDlU7Ft7GD3fFrk2npDk-cgtHvrJkl78NvjwenHY-k0z8-Tg_v1o https://globalnews.ca/news/4540315/new-drug-checking-machine...
somebodynew 8y ago
A very simple refractive IR spectrometer is possible for under $1000 if you can live with 2-10μm range. I don't have a full write up yet but the basic design is an MLX90614 thermopile scanning infrared light generated by nichrome wire, focused with a zinc selenide CO2 laser lens (the ones without an AR coating are better but harder to find), and separated by a silicon prism which is essentially just a chunk of a broken silicon boule. It's very difficult to find transparent materials in this wavelength range, especially when you're limited to cheap goods mass-produced for some other application. Signal noise and speed will be much worse than a modern FTIR but it's usable when calibrated.
- dejv 8y ago
  It might work for qualitative measurement (what is the solution you are measuring), but this kind of instrument will not be performant enough to do qualitative analysis. Once you want to measure amounts the FTIR is probably the only way to go, especially with more complex solutions.
dejv 8y ago
There is Neospectra [1] company that produces FTIR-on-chip modules. Performance is not that great compared to research grade FTIR, but the price is a lot less. [1] https://www.neospectra.com/ https://www.neospectra.com/

analog31 8y ago

I help design spectrometers. Every once in a while, a new idea for a mini spectrometer floats across my desk. Many of the ideas are based on silicon IC fabrication technologies or micromachining. The drawback is the same in every case: The sheer amount of light that can pass through the optics of a spectrometer depends on its size. This in turn affects what signal-to-noise ratio can be realized. These devices are certainly interesting, and performance is relative to requirements, so a novel application could make use of whatever sensitivity is made available by a particular device. But a tiny spectrometer isn't likely to be a drop-in replacement for a big one unless the big one is overkill for its application. Still, I read these articles with interest, because my "size matters" rule is somewhat ad hoc, and there might be a factor that I'm overlooking.

DenisM 8y ago
Maybe you can help me with this... I want to measure the quality of light in my home and office. CRI seems to be the right metric, and it seems that the cheapest option is a $2000 (Sekonic) hand-held device. Are there cheaper options? I don't need much precision, just enough info to understand that these lightbulbs over here are much better than those other lightbulbs over there. I am puzzled as to why it has to be so expensive. I would think one can put a prism, project the light over the surface of a black-and-white CCD sensor and measure the light intensity along the length, giving a reasonably good idea of how much energy is deposited into each wavelength range. I feel like one of these can be made for $20 in parts?
- milleramp 8y ago
  This spectrometer is inexpensive: https://publiclab.org/wiki/desktop-spectrometry-kit-3-0 https://publiclab.org/wiki/desktop-spectrometry-kit-3-0 The problem is calibration, you would need to calibrate with sources like lasers or fluorescent light with known spectral peaks. Then you could use the spectrum to calculate CRI. You are just calculating cri (which has its own issues), so even with a crude device some spectral error is ok.
- danielvf 8y ago
  You can get a plastic DSLR camera body cap for less than 50 cents each (ebay from China). This cap goes where the lens would attach the camera when you don't have a lens on. Sometimes I cut a hole in the center of a cap and make really hacky camera "lenses" for fun. You could put a prism on the outside of a cap. You would then need to calibrate your new spectra-cam on something with a known radiation (usually just find a good blackbody radiator.) You can't just convert to black and white without calibration because the RGB sensors on the camera are going to have their own sensitivity to different wavelengths. This would be an awesome project! -- I write firmware for high end professional LED lights, and have a $3K spectrometer on my desk. Here are things I've learned: 1. CRI is simply a bad formula to judge light quality overall and gives almost meaningless results at lower color temperature levels. 2. There are lots of fantastic python modules for working with spectrograph and light data. 3. One awful thing cheap LED lights do is blink slowly to control their voltage. This is at least as bad a poor CRI for aggravating your eyes. (Sometimes you can see this just by using slow motion video on your phone)

softgrow 8y ago

If you are wanting an inexpensive spectrometer, then Public Labs has instructions on how to build one using an old DVD as a diffraction grating https://publiclab.org/wiki/spectrometry https://publiclab.org/wiki/spectrometry I got a kit as a present and really enjoyed it.

dejv 8y ago
It depends on what you want this spectrometer to do. Public Lab spectrometer is interesting and cheap, but the performance is very very limited. If you need something better you can search eBay for used (scanning) monochromators. Next step is to check Ocean Optics or Hamamatsu catalogs: they have good line of products, but those are in 1000 USD+ range.

keithnz 8y ago

This is cool, a while back when I used to do fruit sorting machines, we used a spectrometer for working out the sugar content of fruit. Nothing quite like setting up the machine to siphon off the biggest sweetest peach you can find at one of the largest peach farms in the world. best. peach. ever. :)