A Projection panel (also called ''overhead display'' or ''LCD panel''
) is a device that, although no longer in production, was used as a
data projector is today.
It works with an
overhead projector
An overhead projector (often abbreviated to OHP), like a Movie projector, film or slide projector, uses light to Projector, project an enlarged image on a Projection screen, screen, allowing the view of a small document or picture to be shared ...
. The panel consists of a translucent
LCD
A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liquid crystals do not em ...
, and a fan to keep it cool. The projection panel sits on the bed of the overhead projector, and acts like a piece of
transparency. The panels have a
VGA
Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the IBM PS/2 line of computers in 1987, which became ubiquitous in the IBM PC compatible industry within three years. T ...
input, and sometimes
Composite (RCA) and
S-Video
S-Video (also known as separate video, Y/C, and erroneously Super-Video) is an analog video signal format that carries standard-definition video, typically at 525 lines or 625 lines. It encodes video luma and chrominance on two separate chann ...
input. Later models have remotes, with functions such as 'freeze' which lets you freeze the image, useful for when you want to leave something on the screen whilst you do other things. Earlier models only had 640x480 resolution, while newer ones had up to
SVGA
Super VGA (SVGA) or Extended VGA is a broad term that covers a wide range of computer display standards that extended IBM's Video Graphics Array, VGA specification.
When used as shorthand for a resolution, as VGA and XGA often are, SVGA refers to ...
resolution. Proxima, one maker of the panels, included a
magic wand and sensor, which worked with the sensor detecting where you put the wand, to create and interactive effect, the equivalent of today's
smart boards.
Although they are not produced anymore, used panels can be purchased for a fraction of the price of a data projector. The panels are quite dim, as they do not let a great deal of light through, so brightness can be a problem, even with a powerful overhead projector.
References
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Display technology