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 Television Types - There are several types of television on the market today.Discover the various television types and features now available...
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Projection Television. Projection TV technology can create large screen sizes at a reasonable price. With
both back- and front-projection TV, the light sources are three separate
picture tubes with different phosphor screens built in, one each for R, G and
B.
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Projection Television
There are two approaches to
projection TV-- back- and front-projection. With both back- and
front-projection TV, the light sources are three separate picture
tubes with different phosphor screens built in, one each for R, G
and B.
The main requirement is high brightness, but this results in
high temperatures. To withstand the great heat, the phosphor screens
are made of sapphire or, a more affordable alternative, a forced-air
cooling system is used.
Samsung HLN617W 61 in. Projection Television
To gather as much light as possible and to
project it on the screen, conventional lenses or a special Schmidt
optical system is used. The lens or optical system gathers the
scattered light rays from the tube and concentrates them into a
parallel beam. This beam passes through a corrector lens on its way
to the screen.
Zenith Projecton Television R50V26
As the tubes are situated alongside one other, the
light beams strike the viewing screen from a slightly different
angle, which causes the three colour images to be out of alignment.
In order to correct this, a convergence system is incorporated in
the deflection system.
With back-projection TV a coloured image
formed by the three picture tubes is projected onto a large screen
via a lens. Here the picture is built up on the rear of a
ground-glass screen. Much depends on the required screen size and
viewing area. To make a set smaller, a light path is often folded by
an intermediate mirror and the image is formed on an integral
screen.
Front-projection is where three separate RGB images are
projected onto a viewing screen, where the projector and viewers are
on the same side of the reflective screen.
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