Air Filter
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Background and Identification
Found in classrooms, board rooms, and multi-purpose rooms everywhere, projectors are universal to nearly all devices, as long as the appropriate cables and adapters are available. Projectors take in an input signal much like a screened display, transmitting it as an image to a surface. Most projectors do this using a small transparent lens to create the image, but newer technologies use lasers to project the image directly.
Projected images have been around since prehistoric times, with instances of shadow puppetry showing up in recorded history as early as 1000 BCE. The principle of camera obscura, showing up in Chinese texts around 400 BCE, is another early example of projected images, as it uses the light bouncing off of an actual object as the source to produce an inverted image when shined through a pinhole.
Early projectors, like the slide projector or overhead projector, were only capable of projecting a single image at a time, which would have to be manually changed or manipulated to change the projected image. These older methods consisted primarily of a light source and transparent slides to alter the light from the source as it travelled to the projected surface, producing the desired image.
Most projectors used nowadays are video projectors, which are the digital counterparts to their analog predecessors, and are capable of producing images from an electrical signal, rather than shining light through an image medium. Digital projectors have now reached mass adoption, with most movie theaters even replacing their film projectors for digital cinema video projectors.
