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In video projection terminology, throw is the distance between a video projector lens and the screen on which it shines. It is given as a ratio (called throw ratio), which describes the relationship between the distance to the screen and the width of the screen (assuming the image is to fill the screen fully).
The Cooke triplet is a photographic lens designed and patented in 1893 by Dennis Taylor who was employed as chief engineer by T. Cooke & Sons of York. It was the first lens system that allowed the elimination of most of the optical distortion or aberration at the outer edge of the image.
As the demand for projectors grew, Buhl Industries was founded in 1953, and became the leading US contributor for several optical refinements for the overhead projector and its projection lens. [citation needed] Overhead projectors began to be widely used in schools and businesses in the late 1950s and early 1960s, [21] beside the ...
For a thin lens in air, the focal length is the distance from the center of the lens to the principal foci (or focal points) of the lens.For a converging lens (for example a convex lens), the focal length is positive and is the distance at which a beam of collimated light will be focused to a single spot.
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 .
All enlargers consist of a light source, normally an incandescent light bulb shining though a condenser or translucent screen to provide even illumination, a holder for the negative or transparency, and a specialized lens for projection, though some, such as the Rapid Rectilinear or Aplanat [citation needed] could be used in both camera and enlarger.
Simulation of a spinning zoopraxiscope An early projector and seats from a movie theater. The main precursor to the movie projector was the magic lantern.In its most common setup it had a concave mirror behind a light source to help direct as much light as possible through a painted glass picture slide and a lens, out of the lantern onto a screen.
A Zenith 1200 CRT Projector based home theater. Visible extending from the ceiling are three lenses, one each for red, green and blue Black and white CRT projector. A CRT projector is a video projector that uses a small, high-brightness cathode-ray tube (CRT) as the image generating element. The image is then focused and enlarged onto a screen ...