Light from the lantern is polarised by reflection from a stack of glass plates, although a single plate would give polarised light a significant amount would be refracted. A stack of plates gives polarised reflection from the top surface of each plate.

An analyser (Nicol prism) should fit at the end of the projection lens, a Nicol prism is with this example but is combined with a microscope objective. The projection microscope attaches to the end of the projection lens. Also known as an elbow polariscope.