Overhead projector

<p>An overhead projector (often abbreviated to OHP), like a <a href="/facts/Movie_projector/SXzyFeDQ">film</a> or <a href="/facts/Slide_projector/b2N84a91">slide projector</a>, uses light to <a href="/facts/Projector/ucQKkpAS">project</a> an enlarged image on a <a href="/facts/Projection_screen/EfJYBwt2">screen</a>, allowing the view of a small document or picture to be shared with a large audience.
</p><p>In the overhead projector, the source of the image is a page-sized sheet of <a href="/facts/Transparency_and_translucency/PRryNNW6">transparent</a> plastic film (also known as "viewfoils", "foils" or "<a href="/facts/Transparencies/297xt6wU">transparencies</a>") with the image to be projected either printed or hand-written/drawn. These transparent sheets are placed on the glass <a href="/facts/Platen/U9TN08Qa">platen</a> of the projector, which has a light source below it and a projecting <a href="/facts/Mirror/wMu4u6BB">mirror</a> and <a href="/facts/Lens/ejlH6n5c">lens</a> assembly above it (hence, "overhead"). They were widely used in education and business before the advent of <a href="/facts/Video_projector/5fIVG2sq">video projectors</a>.
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Overhead projector open-in-new

Overhead projector