Spectral analysis at home

Friends are approaching Friday evening, this is a beautiful intimate time, when you can get your spectrometer under the cover of the inviting dusk all night, measure the spectrum of the incandescent lamp before the first rays of the rising sun, and when the sun rises to measure its spectrum.
How do you still not have your own spectrometer? Do not worry, go under the cut and correct this misunderstanding.
Attention! This article does not claim to be a full-fledged tutorial, but perhaps within 20 minutes after reading it, you decompose your first radiation spectrum.




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Man and spectroscope

I will tell you in the order in which all the stages went by myself, one can say from worst to best. If someone is aiming at once for a more or less serious result, then half of the article can be safely skipped. But for people with crooked hands (like mine) and just curious, it will be interesting to read about my ordeals from the very beginning.
The Internet is walking a sufficient amount of materials on how to assemble a spectrometer / spectroscope with your own hands from the materials at hand.
In order to acquire a spectroscope at home, in the simplest case it will take quite a bit of a CD / DVD disc and box.
This material has pushed me into my first experiments in the study of the spectrum - Spectroscopy

Actually, thanks to the author's work, I assembled my first spectroscope from a translucent diffraction grating of a DVD disc and a cardboard tea box, and before that I had a thick piece of cardboard with a slit and translucent grating from a DVD disc.
I can not say that the results were stunning, but the first spectra were completely successful, miraculously saved photos of the process under the spoiler



Alternatively, you can do it differently , use a reflective layer or use a matchbox and blades.

From spectroscope to spectrometer

Well, suppose you have already looked at the spectra of everything that shines in your house.
There is a logical development of the situation. How now to explore what they got?
Here again, several options will come to our aid. The first thing I found on the subject of spectral analysis was the development of a foreign scientist - Cell Phone Spectrophotometer, which suggests using a collected spectroscope, a mobile phone camera and free software written by the author as a spectrometer, but due to the lack of components at hand, the system itself I did not collect, and used only the software and pre-captured spectra.
Oddly enough, but using the software (CellPhoneSpec.exe) caused some difficulties for me and my colleague, for the most part I learned empirically how it works, I still hope that I understood correctly, in any case, even if not, then at the end of the article I will give an option that works iron. In the meantime, a little about CellPhoneSpec.

My instructions are more like dancing with a tambourine, but still.
To work with the program, we need a sample of the full spectrum and a photo of the captured experimental spectrum, and then, in order:
0) It is desirable for convenience to put all the photos in one folder to the .exe file of the program
1) Open the program, select the picture with the full spectrum sample in the reference field, select the sample photo in the sample field
2) Click on the extreme blue part of the reference dialog pops up - select “blue end”, click on the red end of the spectrum and select “red end”, respectively, and do the same for the sample tab.
3) It would seem that everything is going to build graphics, but some error constantly pops up,
I treat her like that. In the spectrum parameters fields, I delete the values ​​after the point and the inclusive point. Well, let's say I make 720.0 just 720 and press enter and so on for all values, then in the sample field I select the same picture once again that I put on the Make Plot button.
4) Click Make Plot to get the graphics of the three channels (RGB) and the total. The resulting data can be saved in CSV



I can not say how reliable this method is, but the resulting graphs can be correlated with my expectations and with the graphs obtained with SpectralWorkbench. , but I still will not argue that the method described by me is 100% correct (I did not particularly delve into the author’s instructions).

The juice

Due to the lack of confidence in the quality and lack of convenience of obtaining spectral analysis results obtained earlier, I turned to my talented friend and colleague DrZugrik for help .
And this golden man with straight arms collected me a wonderful spectroscope.
He took as a basis the development of the project PublicLab.org (assembly instructions), which was previously mentioned in the open spaces of Habr

The only thing for my convenience, he modified this design with a USB video camera, it turned out like this:



I’ll say right away that this modification saved me from having to use a mobile phone camera, but there was one drawback that the camera could not be calibrated for the settings of the Spectral Worckbench service (which will be discussed below). Therefore, I couldn’t manage to capture the spectrum in real time, but it was possible to recognize the already collected photos.

So let's say you bought or assembled a spectroscope according to the instructions above.
After that, create an account in the PublicLab.org project and go to the SpectralWorkbench.org service page. Next, I will describe to you the spectrum recognition technique that I used myself.
To begin with, we will need to calibrate our spectrometer. To do this, you will need to get a snapshot of the spectrum of a fluorescent lamp, preferably a large ceiling, but an energy-saving lamp will do.
1) Press the button Capture spectra
2) Upload Image
3) Fill in the fields, select the file, select new calibration, select the device (you can choose a mini spectroscope or just custom), choose which spectrum you have is vertical or horizontal, so that the spectra in the screenshot of the previous program are clear - horizontal
4) A window will open with charts.
5) Check how your spectrum is turned. On the left there should be a blue range, on the right - red. If this is not the case, choose the more tools button - flip horizontally, after which we see that the image has turned and the graph does not, so click more tools - re-extract from foto, all the peaks again correspond to the real peaks.

6) Press the Calibrate button, click begin, select the blue peak directly on the graph (see screenshot), click LMB and the pop-up window opens again, now we need to click finish and select the extreme green peak, after which the page will be updated and we will get calibrated by wavelengths image.
Now it is possible to fill in the other spectra under study; when requesting calibration, we need to indicate the graph already calibrated by us earlier.



Attention! Calibration assumes that you will continue to take pictures on the same apparatus that calibrated the change in the resolution resolution apparatus; a strong shift of the spectrum in the photo relative to the position on the calibrated example may distort the measurement results.
Honestly, I take my pictures slightly rules in the editor. If there was illumination where it was, it darkened the surroundings, sometimes turned the spectrum slightly to get a rectangular image, but once again I repeat the file size and location relative to the center of the image of the spectrum itself is better not to change.
With the rest of the functions like macros, auto or manual adjustment of brightness, I suggest you understand yourself, in my opinion they are not so critical.
The resulting graphs are then conveniently transferred to CSV, with the first number being a fractional (probably fractional) long wave, and a comma-separated average of the radiation intensity. The obtained values ​​look nice in the form of graphs, built for example in Scilab.



SpectralWorkbench.org has apps for smartphones. I did not use them. so I can not evaluate.

Colorful day to you in all colors of the rainbow friends.

UPD: At the request of DrZugrik , I will additionally write that the SpectralWorckbench version of the equipment is one of the most cost -effective , some additional spectrometer modules for the Arduino can cost 500 eternally conventional units.