Working with Polarized Light

If you learned microscopy with white light, working with polarized light may sometimes be a challenge. There are a few methods you can incorporate into your workflow both to help with the transition and to insure that you are not missing anything when you scan your slide.

If you are having trouble “seeing” microfossils (1) open the aperture in the condenser assembly (not the iris on the light source) to let in more light. The polarization will stay intact for microfossils with birefringent properties, but the background of the slide will be much lighter in color allowing for better viewing of phytoliths and other materials that do not polarize clearly, if at all. If more light is not helping, (2) engage the Lambda waveplate. The Lambda plate will shift grayscale to color, and will help some users to “ignore” debris. Using the Lambda plate you will be able to see everything on the slide, including damaged starches and phytoliths, and intact starch grains will still have a clearly-defined extinction cross. You will, however, need to get used to viewing your materials in a rather shocking shade of fuchsia.

If you trained in phytolith analysis before learning starches, odds are good that you can recognize and pick out microfossils from the field of view (3) without using polarized light. If this method, or any other, for that matter, is most comfortable for you, by all means, use it, and engage the polarizing filters when you need to check for birefringent properties. The most important issue is that all possible microfossils be recognized and identified, and that will not happen if the operator is not comfortable with the working conditions. Do what works best for you.

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