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First used in the 1950s, slide projectors allowed the teacher to display in formation one slide at a time with a focusing lens and condensing lens. For years, this was the most advanced way for educators to display visual information to their students

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The Episcope, one of the earliest opaque projectors was sold by a German toy manufacturer in 1900 and used to project postcards, pages of books, photos or 3D objects like insects, leaves and coins onto the wall. This technology works by transferring presentation material onto 35mm slides, therefore projecting anything that can be put onto film.

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The first projector and one of the leading predecessor of the movies -- was invented in the 1650s, probably by a prominent Dutch scientist, Christiaan Huygens. It soon became a showman's instrument.

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Similar to a slide projector, overhead projectors use a focusing lens to project light from an illuminated slide onto a projection screen. Teachers could now display transparencies, which could be either printed on or written on by hand. Educators were still limited in what and how they could display information to their class, but the overhead projector represented an enormous advancement in classroom technology.

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The digital projection panel consisted of a large LCD, electronics, cooling fan, and a plastic or metal enclosure with a glass plate on both sides of the LCD. A digital projection panel was essentially an electronic sheet of paper in a box about the size of a large book that when plugged into a computer could display the image using the light and optics of the overhead projector.

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the fully integrated digital data projector came into existence in the early 1990's and served primarily as a computer display projector for business, education and training.It essentially combined the overhead projector and the digital projection panel into one device making it considerably smaller and more easily transported.

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The digital video projector also came into being in the early 1990's and like the early computer projectors, they were large, heavy and expensive.Video projectors also serve nicely as TV projectors that can project your satellite receiver programming or local broadcasts. With today’s TV projector you can also attach a DVD player or any of the high definition DVD players and enjoy a movie of your choosing.

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When coupled with a special projection screen, projectors now allow teachers to manipulate their computer or other devices with their hands. SMART Boards, for instance, came around in 2003 and revolutionized the way teachers developed interactive curricula. Math teachers could graph in real time; science teachers could easily log data during a class experiment; and football coaches could draw out plays for his team. The possibilities are endless, and every day teachers are exploring new and exciting ways to use this technology.