OVERHEAD PROJECTOR.

Two types of overhead projector are discussed. One has its lamp in the projector head and light is sent downwards to the mirrored work surface, reflected back to the projection head, and then imaged via a lens on the screen. This projector folds up into an executive brief-case, looks elegant and is convenient for the travelling salesman. The other type has an enclosure below the working surface with a lamp in the bottom which together with reflector floods the transparent top with light. The top or working surface takes the form of a Fresnel lens to direct light evenly through the transparent art work to be picked up by a mirror in the projector head and then transmitted via the lens to the projection screen. This type of projector can present a much wider range of materials. Auxiliary equipment and some useful techniques are described.