History
The opaque projector is a predecessor to the overhead projector. The light source in early opaque projectors was often limelight. Incandescent light bulbs and halogen lamps are most commonly used today. In the early and middle parts of the 20th century, low-cost opaque projectors were produced and marketed as toys for children.
In educational settings, the specific role of the opaque projector has been superseded by the document camera, a lighted table with a fixed video camera above it. The image from the camera is displayed using a separate projector. The document camera is also called a desktop presenter unit or opaque projector.
Read more about this topic: Opaque Projector
Famous quotes containing the word history:
“The history of every country begins in the heart of a man or a woman.”
—Willa Cather (1876–1947)
“It is the true office of history to represent the events themselves, together with the counsels, and to leave the observations and conclusions thereupon to the liberty and faculty of every man’s judgement.”
—Francis Bacon (1561–1626)
“America is the only nation in history which miraculously has gone directly from barbarism to degeneration without the usual interval of civilization.”
—Georges Clemenceau (1841–1929)