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New spectrometer build and CFL lines

by Suiris | August 03, 2013 06:56 | 91 views | 13 comments | #8961 | 91 views | 13 comments | #8961 03 Aug 06:56

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I decided to build my second spectrometer. I built a box, long and wide enough for me to put a Canon IXUS 120 camera and be able to adjust angles, slit:grating length, and for future projects play a little with collimating lenses. The slit is made of two razor blades.

I used Canon IXUS 120 with a removed IR filter, grating set at 30cm distance from the slit, angle about 50 degrees. ( I say "about" because I have so far not been able to measure the angle, need to invest in a protractor.) The grating is set to 0,5cm away from camera lens with the possibility of angle adjustment for finer focus. The slit in this CFL reading is set to about 0,08mm.

Question: Why do I see multiple blue and green spectral lines? If you look close at the 405nm line it has more lines right next to it? Same thing with the second blue and the bright green. Are the lines supposed to be there or is this some unknown to me effect caused by a too narrow slit? Light reflection from the fine edge of the razor blade? When I make the slit wider this phenomenon dissapears. Thanks and greetings from Sweden, Martin





Black fleecefilt on the inside.


Opening for a webcam USB port. .


Here I added a metal plate and more black filt on top.


The idea is that I can attach a small magnet to the camera and be able to change the distance or the angle by simply sliding the camera on the filt. The magnet is 3cm away from the camera body and just strong enough to keep the camera steady and firm.


The slit job was a fast work in progress, I wanted to test my new creation as fast as possible.


These are the CFL lines. The additional lines are to the right of 405nm and the 435nm lines, and the green 538nm has additional lines to left? There are also extra lines in the 465nm region, faint but they are there. Is it supposed to be like this? Try zooming in if they are hard to see.

Link to SpectralWorkbench graph


Hi Martin, That's a beautiful spectrum. You obviously got everything lined up perfectly. I don't know about the extra line near 405 nm because my camera is not very sensitive in that region. But the line near 538 nm always appears in my CFL spectra. See and I suspect the line near 405 is real too. Very nicely done.

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Thanks cfastie, I still think I can do a better job though, getting the focus and resolution even better. Glad to see the line near 538 nm line appears in your spectra too. Perhaps the other lines are real after all. Now that I got the hang of the basics I will try and imrove the image, will do some research on how professional equipment works. Thanks for commenting!

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Wow, that is a gorgeous spectrum! Have you uploaded it to Spectral Workbench yet? I'd love to see a graph.

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Hi Warren, Thanks for the kind comment. I havn´t uploaded it yet, when I upload my spectral images somehow they get strangely comressed and the lines look very short and wide. I am not sure what I am doing wrong. Will work on uploading one of these images one way or the other in the next few days to come. I am thinking if there is a way to have the computer recognize the Canon IXUS as a webcam?

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Ok, finally figure it out Warren, I uploaded the image to spectralWorkbench without any distortion.

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Cool -- can you post a link?

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Really great job. I especially like the cat with yellow and blue eyes!

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Thanks! Her name is Fia and she is six years old :)

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How did you measure the slit width so accurately? Nice work!

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Thanks! Good question. It is not an accurate measure, I used two razor blades and simply put them as close to each other as possible. Looking directly at the slit I could not even see there was one, but when I shone light at it I could see the light was coming through. the 0,08mm is just an estimate.

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Mathew and I are getting ready for the smartphone spectrometers to ship and are printing slits on photographic printing plates (mathew probably knows the nomenclature a bit better) like this:

This is nice because it means we can be super precise. I think we may start shipping several different slit widths in each kit so people can choose. This idea was based on Dave Stoft's idea to use inkjet printed transparency as attenuator material, in a related idea.

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That´s great! I found making a straight and even slit using razorblades difficult. When the blades got too close to eachother they touched the edge and made the edge uneven by snapping microscopic bits of metal. It was also difficult to keep the width at the top and the width at the bottom the same distance.

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