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Overhead projectors were introduced into U.S. military training during World War II as early as 1940 and were quickly being taken up by tertiary educators, [14] and within the decade they were being used in corporations. [15] After the war they were used at schools like the U.S. Military Academy. [13] The journal Higher Education of April 1952 ...
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 .
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.
1974: The lithium-ion battery is invented by M. Stanley Whittingham, and further developed in the 1980s and 1990s by John B. Goodenough, Rachid Yazami and Akira Yoshino. It has impacted modern consumer electronics and electric vehicles. [508] 1974: The Rubik's cube is invented by Ernő Rubik which went on to be the best selling puzzle ever. [509]
These were adapted with a mechanism that spins the disc and a shutter system. Duboscq produced some in the 1850s and Thomas Ross patented a version called "Wheel of life" in 1869 and 1870. [82] The Choreutoscope was purportedly invented around 1866 by the Greenwich engineer John Beale, and demonstrated at the Royal Polytechnic. It projected six ...
The slide images were too small for unaided viewing, and required enlargement by a projector or enlarging viewer. Photographic film slides and projectors have been replaced by image files on digital storage media shown on a projection screen by using a video projector , or displayed on a large-screen video monitor .
When Eastman Kodak first conceived the 8 mm format, no provision was made for the addition of a sound track. Nevertheless, in the 1960s, projectors appeared on the market that were capable of recording and replaying sound from a magnetic stripe applied to the film after it had been processed.
Victor offered many models of 16mm projectors, most with only minor variations, but prior to military contracts won during World War II, all were made and sold in very small numbers, from 20 units to usually no more than a couple of thousand units. The company was a large producer of lantern slides using their "Featherweight" method- a one ...