Overhead projector

摘要

The aim in an overhead projector consisting of a writing plate, a Fresnel lens plate arranged therebelow, a light source and a lens supported by a support arm is to achieve the object of eliminating the disadvantages of the prior art and of providing a possibility of making accessible to a large circle of viewers and listeners information called up by a lecturer from an electronic information source such as, for example, a computer or an electronic game. The invention achieves this object by arranging between the Fresnel lens plate and the writing plate a layer of light-rotating liquid crystals aligned in the electric field and, to both sides thereof, transparent electrodes, two of the plates or layers penetrated by the beam path having light-polarising properties.