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An overhead projector works on the same principle as a slide projector, in which a focusing lens projects light from an illuminated slide onto a projection screen where a real image is formed. However some differences are necessitated by the much larger size of the transparencies used (generally the size of a printed page), and the requirement ...
Overhead projector in operation, with a transparency being flashed. A transparency, also known variously as a viewfoil or foil (from the French word "feuille" or sheet), or viewgraph, is a thin sheet of transparent flexible material, typically polyester (historically cellulose acetate), onto which figures can be drawn.
A projector or image projector is an optical device that projects an image (or moving images) onto a surface, commonly a projection screen. Most projectors create an image by shining a light through a small transparent lens, but some newer types of projectors can project the image directly, by using lasers .
The Polylux was an overhead projector produced in the German Democratic Republic (GDR). It also functioned as a generic name for overhead projectors in the GDR. The Polylux was produced in the VEB (Volkseigener Betrieb: people’s enterprise) Phylatex-Physikgeräte DDR, in Frankenberg near Chemnitz (then known as Karl-Marx-Stadt). It was ...
Overhead projector and slide projector: Video projector: Primarily for continued use of older materials. Some teachers find the overhead projector more convenient for lectures depending on their teaching style. Phonograph and phonograph record: Audio cassette, 8 track tape, CD, digital audio: Used to play older or archived recordings.
In the GDR, it was mainly known for producing overhead projectors, called Polylux. The company was founded in 1870 as Reißzeugrichter and manufactured drawing table tools. In 1874 the founder Emil Oskar Richter invented the bow compass. After switching its focus to overhead projectors in the late 1960s, it was renamed to VEB Polytechnik.
Shows could be as simple as a single operator and two or three modified slideprojectors or overhead projectors and a couple of color wheels or as complex as shows with ten or more operators, 70 plus projectors (including liquid slide, liquid overhead, movie and still image models plus a vast array of highly advanced (for the time) special ...
As copying technology advanced, Thermofax machines were subsequently marketed as a method of producing transparencies (viewgraphs) for overhead projector presentations. A sheet of heat-sensitive clear stock was placed on top of the original, and passed through a ThermoFax, producing a black image on the clear stock.