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A combination between a whiteboard and a cork bulletin board Original early 1960s ad for "Plasti-slate", the first whiteboard/dry erase board invented by Martin Heit. It has been widely reported that Korean War veteran and photographer Martin Heit and Albert Stallion, an employee at Alliance, a leading flat rolled steel sheet supplier should be credited with the invention of the whiteboard in ...
This technology allows whiteboards to be made of any material; with this system no dry-erase marker or stylus is needed. Laser light curtain – An infrared laser is located in each upper corner of the whiteboard. The laser beam sweeps across the whiteboard surface—much like a lighthouse sweeps light across the ocean—by using a rotating ...
An overhead projector works on the same principle as a slide projector, in which a focusing lens projects light from an illuminated slide onto a projection screen where a real image is formed. However some differences are necessitated by the much larger size of the transparencies used (generally the size of a printed page), and the requirement ...
A darker (grey) screen reflects less light, of course—both light from the projector and ambient light. This decreases the luminance (brightness) of both the projected image and ambient light, so while the light areas of the projected image are dimmer, the dark areas are darker; white is less bright, but intended black is closer to actual black.
The opaque projector, or episcope is a device which displays opaque materials by shining a bright lamp onto the object from above. The episcope must be distinguished from the diascope , which is a projector used for projecting images of transparent objects (such as films), and from the epidiascope , which is capable of projecting images of both ...
The projector is normally set at 90°, although 71° 31' may be used, in relation to the terrain. The projector consists of a 430-watt incandescent bulb set in a weatherproof housing. Inside the housing are two mirrors; the first, above the bulb, reflects the light downwards to the second mirror, that then reflects the light upwards to the ...