page_title: Projector
section_title: Opaque projectors
hierarchical_section_title: Projector / History / 1700 to 1900 / Opaque projectors
caption_attribution_description: English: A.E. Dolbear's illustration of
context_page_description: A projector or image projector is an optical device that projects an image 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. A virtual retinal display, or retinal projector, is a projector that projects an image directly on the retina instead of using an external projection screen.
  The most common type of projector used today is called a video projector. Video projectors are digital replacements for earlier types of projectors such as slide projectors and overhead projectors. These earlier types of projectors were mostly replaced with digital video projectors throughout the 1990s and early 2000s, but old analog projectors are still used at some places. The newest types of projectors are handheld projectors that use lasers or LEDs to project images. Their projections are hard to see if there is too much ambient light.
  Movie theaters used a type of projector called a movie projector, nowadays mostly replaced with digital cinema video projectors.
context_section_description: Swiss mathematician, physicist, astronomer, logician and engineer Leonhard Euler demonstrated an opaque projector, now commonly known as an episcope, around 1756. It could project a clear image of opaque images and (small) objects.
  French scientist Jacques Charles is thought to have invented the similar "megascope" in 1780. He used it for his lectures. Around 1872 Henry Morton used an opaque projector in demonstrations for huge audiences, for example in the Philadelphia Opera House which could seat 3500 people. His machine did not use a condenser or reflector, but used an oxyhydrogen lamp close to the object in order to project huge clear images.
caption: Henry Morton's projection as illustrated in François Moigno's L'art des projections (1872)
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