The Microscopic Imager is a combination of microscope and camera, and is used to look at rocks at the crystal level. It uses two types of lights sources visible light and polarised light.
The shapes and sizes of crystals, or fossilised material can be seen quite easily through a visible light microscope, but it is often difficult to identify the type of mineral or crystal. Cross polarising microscopes illuminate a sample with polarised light, which interacts with some minerals creating characteristic colour combinations or patterns.
Basalt Thin Section: The left hand side is under visible light: the crystal shapes are visible but it is not easy to determine what each mineral is. The right hand side is under cross polarised light: the different minerals have distinctly different colours and patterns that are diagnostic of the particular mineral.