I finally got back to doing some proper experiments with spectroscopy, or at least, as far as beginning to build some simple spectroscopes. After a bit of experimentation I discovered that glass and acrylic prisms really don’t give such a good spectra. Maybe the ones I got were too small or maybe I was using inappropriate light sources, but I could only get a very narrow spread.
So following the advice of Marc, and several instructables, I decided to play around with CDs and DVDs. It works great! I also discovered that the good old fashioned torch with a good old fashioned incandescent bulb works a lot better than all the fancy LED torches I’d been getting.
You can either use the surface of the CD or DVD itself to see the spectra, or you can peel off the film on the opposite side to the lettering. If you project light through this you get not one, but two spectra about 90º apart.
Here a small square of the material has been taped to a ‘screen’. You can see most of one of the spectra behind it.
This was looking promising so I wanted to build a sturdier version that could be portable, durable, have a way of fitting some kind of bio-electronic experiment in the light path, and that could house sensors to measure any change in the light bands. This is the mark 1 prototype – serviceable for now but definitely not the finished article.
The light shines in through the small hole – which has a piece of DVD material on the other side – and the spectra is projected at 45º on the back wall. I made this wall a removeable screen so that I would have easier access to the sensors for the purpose of making various kinds of adjustments, or even having interchangeable screen and sensor units for different experiments. The platform on the front can support the light source and the bio experiment. Having thought some more about it though, I’ll probably use a combination of glass microscope slides and PDMS to make something that fits over the hole. should work better than shining the light horizontally through a few centimeters of PDMS, electronics and organisms.
I haven’t had time to plug the sensor block into an Arduino and measure the spectra yet. That will probably be the next post.
