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In the early 1980s–1990s, overhead projectors were used as part of a classroom computer display/projection system. A liquid-crystal panel mounted in a plastic frame was placed on top of the overhead projector and connected to the video output of the computer, often splitting off the normal monitor output.
It works with an overhead projector. The panel consists of a translucent LCD, and a fan to keep it cool. The projection panel sits on the bed of the overhead projector, and acts like a piece of transparency. The panels have a VGA input, and sometimes Composite (RCA) and S-Video input. Later models have remotes, with functions such as 'freeze ...
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.
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.
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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 ).
I'm tempted to state: "Overhead projectors with transparencies were in wide use in business from the 50s and into the 90s when computer projections of Powerpoint presentations obsoleted the use of transparencies with overhead projectors". However, I have no source other than my own experience.
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 .