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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 ...
A simple example is an overhead projector transparency. Usually when the term SLM is used, it means that the transparency can be controlled by a computer. SLMs are primarily marketed for image projection, displays devices, [1] and maskless lithography. [citation needed] SLMs are also used in optical computing and holographic optical tweezers.
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 .
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.
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 ...
A document camera can enlarge the small print in books and project a printed page as if it were a traditional transparency by using a zoom feature. Document cameras do not require the lights to be dimmed in the room they are used in, contrary to what overhead projectors need to be visible. [3]
The opaque projector, or episcope is a device which displays opaque materials by shining a bright lamp onto the object from above. The episcope must be distinguished from the diascope , which is a projector used for projecting images of transparent objects (such as films), and from the epidiascope , which is capable of projecting images of both ...
These include slide projectors, overhead projectors, and computer projectors. Slide projectors are the oldest form of projector, and are no longer used. Overhead projectors are still used but are somewhat inconvenient to use. In order to use an overhead projector, a transparency must be made of whatever is being projected onto the screen.