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Greetings with the New Year 2015!
I decided to compose a new blog post this week instead of adding material to the previous post. Because older blog posts people might not check over again.
My collegue Ilja Fescenko came up with an idea to bounce light between two parallel mirrors allowing to recycle laser power and monitor scattered light by dust in relatively large area.
Green laser pointer 5 mW is OK, with a 30 mW laser visibility is better.
Front coated alu mirrors from an old scanner are used. One mirror is fixed. Second mirror and laser direction can be fine adjusted.
If both mirrors are parallel then the spots make equidistant straight pattern. One can make a parabolic pattern or a spiraling one just by tilting laser beam and one mirror.
A sheet of laser light shows that we are swimming is a see of dust. Dust very nicely visualizes air turbulences.
We are testing now different filters. HEPA13 from a vacuum cleaner, car air filters, cotton wool, electrostatic plastic spiral filter.
This method of observation from a 50 cm distance is sensitive to large dust particles. In order to see the fine dust one needs to use a macro lens (microscope) and then the observation gets smaller.
