jan 1, 1950 - OHP PROJECTOR
Description:
Description: An overhead projector, like a film or slide projector, uses light to project an enlarged image on a screen.
History:Invented in 1950 by Roger Appledorn
Special Features:Overhead projectors have a mirror that reverses the mirror image produced by the face-up orientation of the transparencies. Overhead projectors also have an inbuilt blower that prevents the bulb from overheating.
Uses:The overhead projectors or OHPs are a variant of the slide projectors. They were introduced a few years after the slide projectors. The working of an overhead projector is similar to the slide projector. The light from a source like a high-powered halogen bulb is passed through a condensing lens onto the object for projecting images on the screen.
However, these projectors make use of transparencies instead of slides. Transparencies are transparent sheets with a size similar to the paper sheets. The image could be drawn or printed on these transparent sheets. They have to be placed face-up on the projector.
Interaction/Exposure:These projectors were popularly used in the US military training programs during the World War II as well as in educational institutions and offices. Slide and overhead projectors remained popular almost up to the late 2000s when the digital projectors superseded them.
Added to timeline:
MIL
Date:
