First attempt at DIY Raman Spectrometry
For the past couple weeks I have been working on my (super-budget) Raman Spectrometer. Last night I finally (maybe) got a spectral image. First let me
talk about my set up. My goal is to make a handheld Raman spectrometer so I can analyze samples while I am out in the field. Eventually I wish to
build something similar to this: http://bwtek.com/products/nanoram/
This is the fist time I have built something like this and I do not know much about the process of actually processing digital data, but it will be a
learning experience I guess.
In my spectrometer I am using a 532 nm green laser pointer with 5mW of output power. The light travels to a 50/50 beam splitter. My beam then travels
up to a microscope objective and focused on a sample. In my first test this was Polystyrene foam. The Raman signal travels back through the objective
lens through the beam splitter again and into a 550 nm longpass filter form Throbs. The raman signal then travels though a small gemology diffraction
grating spectrometer which I picked up on eBay for about $30. Underneath the spectrometer I placed my phone (Samsung galaxy S3).
With the lights turned off I then took several spectra photos. Each of the photos were taken with ISO 1600 focused at inf and a 60 second exposure.
The first one with light shining down from above the longpass filter. I think some light leaked by the filter because I was not holding the led
flashlight directly above the spectroscope.
As you can see though there is a a sharp intensity drop at at about 550 nm beaning that the filter was working. I do not know why there is a second
image to the right of the spectrum but I expect it was because I was not holding the flashlight directly vertical to the spectrometer.
The next image I took with the flashlight directly above the objective. I got an overexposed image because the light coming back was far too intense,
but again there is a nice sharp cut off if it wasn't for the glair.
It was then time to take the image of the polystyrene. With the same camera settings and conditions I turned on the laser. At first I thought that I
wasn't getting any image, but after a minute I found this on my camera.
It is incredibly weak and there are no well defined peaks but there is something there. I am going to put my images through photoshop and see if I can
figure out what frequencies the image is displaying and see if it resembles anything close to polystyrene.
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