Applied Science - 2013-05-27
I've been working on a Raman spectroscopy setup in my shop for a while, and was finally able to collect some real, verifiable data this evening. Raman Spectroscopy is a technique where light is directed toward a target, and the reflected light is color-shifted by the size and type of the molecular bonds in the target. This is a non-destructive way to determine an object's molecular structure. The problem is that the color-shifted light is many, many times weaker than the non-color-shifted light. A Raman spectroscopy setup compensates for this, and allows meaningful data to be collected.
he's "pretty Stoked" about his Raman Spectrometer. well played Sir :)
This is really cool. I had seen in the peer-reviewed literature some proposed designs, but had never seen a video of someone actually doing it. Given the cost of Raman spectrometers, I really congratulate you for helping the community of keen curious mind have easier access to scientific exploration by making their own normally prohibitive devices!
there's a few more videos out there take a look around people have been making moves on this one
looking forward to having one on my phone level
This is amazing. Also seeing how you built this device helped me understand how Raman spectroscopy worked. Thanks!
A very nice video and kudos for making your own Raman spectrometer! A couple things to say since I do Raman spectroscopy on an almost daily basis. I always try to go with the shortest wavelength possible as a shorter wavelength will give me the greatest signal because the Raman scattering intensity goes like the excitation wavelength^(-4). If fluorescence is problem, then I'll switch to my redder wavelength. It all depends on the sample. There are other ways of getting around fluorescence such as the technique of photobleaching for example. In any case, I'm not sure if this was brought up in any comments previously, but even without your IR filter on your DSLR detector, your detector might have a very crappy detection efficiency out in the near IR. Hence, you might have to leave the shutter open for quite a while in order to get signal out towards the near-IR. If you happen to have a shorter wavelength laser around your shop, I'd put that into your system and try it out. Even a 532 laser pointer might work if the bandwidth of the laser isn't too broad.
Wow, DIY Raman Spectroscopy. I can't even do DIY Ramen Noodles. Your videos never cease to amaze me. Keep up the great work. You are an inspiration.
I love how even your 7 year old videos are of great quality.
Very nice results. I understand the time you put in here. One reason why you're experiencing so much noise is that (from your info) you haven't normalized your camera. The pigments used in a Bayer array will have gaps in the spectrum. Also, sensors (silicone) are far more sensitive to IR than shorter wavelengths, so to create a realistic image, the blue channel and possibly green have gain applied to level them somewhat with the red channel. This calibration can be done at a certain colour temp, and it may be different to your tungsten. You have also confounded your problem by removing the IR filter, since the debayer algorithms which help present a realistic (correct spectrum) image, take into account this filter. Once you remove it, more spectra reaches the sensor and the manufacturer algorithm cannot deal with it. If you can normalize your DSLR to some extent (including lens) you should theoretically get a cleaner result. Hope this helps.
Hey, great video and nice simple setup. The reason you can't see the stokes/infrared lines is because of the Bayer filter on your camera. You can remove the IR filter, but the RGB Bayer filter is in theory just 3 bandpass filters passing red, green and blue. there is some vague transparency in their IR part (hence the need for a secondary IR filter), but very low compared to the transmission in the visible spectrum.
Hope this helps.
Hot glass filter
I use Raman spectroscopy every day, Renishaw Invia at 514 nm and 786 nm , I had no idea about the working of spectrometer until now, thanks, you are very intelligent sir, I wish to be like you :)
Props for using the open source Octave software. It helps to see people supporting open source mathematics packages, even for leisure.
Nice explanation that why we use wavenumber instead of wavelength in Raman spectroscopy.
Dude you really do a good Job. Great channel. You should get some sort of Presidents award. Not only are you delivering very practical scientific educational material but your topics are really cutting edge creating future inovations. True Competence and a very good person!
Man, this is simply brilliant! hats off. You must be a scientist.
By the way Raman spectroscopy is named after the Indian scientist Sir CV Raman, who discovered Raman scattering in the 1920s.
Wow... Worked with these devices in the past... It's nice to see the details of how they work....
I read about Mr. Raman and how he discovered the shift, but until watching your video I couldn't see how lasers could measure the shift or what it was used for. Thank you much, I just bought a nice used S2000 Ocean Optics NIR spectrometer off of ebay which goes from about 1090 nm to 1400, should be able to do something with it, I'm adding more UV-VIS spectrometer cards to it as slave cards which will allow the ability to measure a total spectrum of 350 through 1400 nm with better than 1 nm resolution. I bought the spectrometer cards to measure laser diode wavelengths, just to characterize their wavelength, but being able to use it with a Raman setup might happen someday.
I know this video is old but I just found this and I wanna say you are BRILLIANT!
We will never bore of any of your experiments Ben!
Excellent video. Explained all concept in 10 minutes, including experiment. I can't wait for follow ups.
Absolutely fantastic! I started researching Raman Scattering when I got my multi-line Argon Ion laser, and was very tempted to try making a basic setup like yours, but I was deterred by the high cost of optics needed for even a simplified version of yours. The diffraction mirror alone would run close to $200.
Props for the TI-80, my favorite TI calculator. I don’t know why, it’s just a charming little underpowered calculator.
With 30000+ subscribers, you'd think wrong by orders of magnitude. We love this stuff and we love you!
You are always a great motivator like i look at what you do and then get motivated to do something.
Ben, your projects never cease to amaze me!
Wow, .... you are a genius, I am glad I found you.
The hazmat guys where i work have a Raman device which I am told cost about 30 grand. This is a pretty neat way of bringing the cost of entry way down. Props!
Yes, if you only want one half of the Raman signal (either Stokes or anti-Stokes), you can use a longpass or shortpass filter that blocks the laser line, but allows everything higher or lower.
I liked it when he said that the Raman effect has nothing to do with the noodles, which was my next question. It was like he knew I wanted to know about that. Nice touch.
Very impressive. Thanks for this video. I wish we did such experiments back in school. I have to add yet another project on my never ending list.
This is so ridiculously awesome! Well DONE! Great results! :). I look forward to your updated version!
Yes, I've been thinking about DIY MRI for a while -- especially since I used to work with commercial MRI machines for my previous job. My friend, Alan Yates is also thinking about it, and we may end up collaborating. It's a really good project, but most of the difficult part is the phase-encoding and math involved with 2D imaging -- not my specialty.
if you need any filters, please contact us GF Technology info@gf-technology.com
bruh how on earth do you even get the parts for a homebrew MRI?
Wow, truly phenomenal. It never ceases to amaze me how much you can do with so little. Well done!
I agree. This is a good plan to get more signal out of the system.
One very important aspect: did you filter out the bore light of the HeNe laser? There is a bluish glow coming out of every HeNe laser which contains all the He and Ne spectral lines. These will probably give WAY more signal than the raman signal. Compare your spectrum against the lines of Ne and see if you're catching those instead of a raman signal.
Agreed: there is I believe a green line in the Ne spectrum.
My first thought was why not charactize the waste beam of the beam splitter with another equivalent calibrated to profile and correct for detector "camera" I guess so to perform a spectral subtraction process... I guess easiest would be digital... though I am wondering about comparing processes losses to be able to perform optically potentially with an optical train inverse signal subtraction method.
@@jafinch78 You'd kind of have to guess how much of the laser spectra is in the signal, in order to determine a multiplicative factor for the waste beam to use as background. Then there's also background noise (such as dark counts) that may or may not be the same in the detector viewing the waste light and that viewing the scattered light that ends up getting multiplied. And then there's other processes like Rayleigh scattering and Mie scattering that exists in the scattered light that you want to get rid of but won't appear in the waste light. I think filtering the input laser with a bandpass to purify it and then using a notch filter to get rid of it is easier to do. I'm not familiar with optical train inverse signal subtraction, however.
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Yeah! That's exactly how astrophysicists work out the chemical composition of other planets, often they use what's called 'rotational raman' spectroscopy which uses radio waves (Since that's what a cold body like a planet emits naturally) to detect the chemicals present on the surface. Nice one!
I'm completely blown away. I don't understand all of this, but I'm subscribing because you're doing excellent work!!!
Really like this, got some good information. I have an old Raman system at work and you help explain some of the details very well. The one we have uses a 1040 nm laser. It's used for student labs.
Many raman systems use a 90 degree setup like the one you described. The backscatter configuration is neat, though, because (1) it enhances the spatial resolution; (2) it's easier for measuring spectra of liquids (I've never heard of any professional 90 degree raman setup having difficulty measuring liquid spectra, but I couldn't get this to work in my DIY setup); and (3) you're half-way there to building a raman microscope. Granted, beamsplitters lessen signal strength and introduce noise.
When I was in school I did work in spectroscopy and I used a double spectrometer that was designed for raman spectrometry. There were two spectrometers stacked on top of each other and connected in series. This was needed to get the signal to noise to see the lines that are close to the powerful source.
Eeyyyyy "Optics" is nice play list to listen in my autistic sleep. Thank you Ben for feeding my autism.
Thanks a lot for the explanation and the search term :) I only knew of absorption and emission spectra in astronomy. Very interesting to hear that there are even more ways to figure out what stuff is made of that's incredibly far away.
Warning - there is no turning back once you have been bitten by the spectroscopy bug. The tremendous depth of information that can be retrieved from spectra is POWERFULLY seductive.
It's a good question. If everything were perfect, we could use only the diffraction grating to separate the original laser line from the Raman signal. However, in the real world, the stray light and scatter from the laser line is so much more intense than the signal, it will overpower everything inside the spectrometer. Professional equipment uses better filters to avoid losing to 30nm.
Did you verify that the other lines weren't spurious lines from the laser ? You can get green and yellow HeNe tubes, and it is sometimes just possible to get some lasing at these lines by adding additional optics to a red hene tubes.
Amazing work! A sugestion: if you want to see the red shifted spectra really close to the excitation beam, you can do it with your 30nm notch filter. Just tilt the filter a bit and the rejection band will shift to the blue according to lambda_cut_new ~ lambda_cut_old * cos(incident_angle). Maybe you can see some close lines!
This is a terrific DIY science project and very well explained. Thanks.
Thats really amazing, Ben! It is so nice to see how you apply many different concepts of physics in your projects and how the results are really close to academic-grade data! With regards to the noise caused by external light reflections, interference etc, you could actually make a short movie and use a program to stack the frames and enhance the quality of data...
good idea - a photomultiplier will give you a lot more sensitivity than a DSLR, and will have a specified wavelength vs. output calibration curve
Hello, I know it's late (8+years :D) , and you probably found the answer by now... But you don't see the IR in the spectrum because your camera's CCD are Silicium photodiode. Bandgap 1.1eV = 1 100nm. So you can't see bellow 1 100nm (even without a "hot glass" filter or a Bayer filter).
Cheers!
awesome experiment. you've got a knack for finding a good balance to quickly introduce a complex topic without boring in details and the demos are always great. thanks, always look forward to your posts :D. i think your optics are probably blocking most of the IR much beyond visible, and not sure the camera sensor will detect it either. i know IR cameras have expensive germanium optics for this reason, and the specs on the filter list 845nm as the lower limit, very close to visible.
@matthiaswandel - 2013-05-27
Love learning about science this way. An explanation, and a homemade apparatus to demonstrate it!