This page presents some examples of
convergent light figures (conoscopic images) obtained with the petrographic
microscope. The pictures were photographed with a phase contrast telescope
inserted between the photo tube of the microscope and a bellow accessory
attached to a digital camera. The phase contrast telescope has the same function
as a Bertrand lens but it is generally much less expensive.
In the first two group of pages, a non mathematical explanation of the
features that can be observed in the conoscopic figures is developed with
the help of diagrams and pictures.