The roles and functions of educational technology in the 21st century education

2. A digital projection, also
called a digital projection
display system, is a
specialized computer display
that projects an enlarged
image on a movie screen.

4. 1) A digital projector, also called
a digital projection display
system, is a specialized computer
display that projects an enlarged
image on a movie screen. Such
devices are commonly used in
presentations.

5.  There are two main types of digital projection
display systems. The older, less expensive type
employs three transparent liquid-crystal-
display ( LCD ) panels, one for each of the
primary colors (red, green, and blue). The
light transmittivity of each pixel varies
depending on the image data received from
the computer. The light from a lamp is
directed through the LCD panels, collimated
using a lens, and projected onto a screen. The
overall construction of the device is similar to
that of a slide projector, where the "slide"
consists of the three LCD panels placed close
together near the focal point of the projection
lens. Advantages of LCD technology include
efficiency, ease of brightness and contrast
adjustment, and high image resolution .

6.  A newer, more expensive scheme is known as
Digital Light Processing (DLP), a proprietary
technology developed by Texas Instruments. In a
DLP display, tiny mirrors are used instead of
transparent panels. Each mirror represents one
pixel. The light, rather than passing through the
panel, is reflected from it. The mirrors move back
and forth, varying the amount of light that
reaches the projection lens from each pixel. Color
is obtained by passing the light from the lamp
through a rotating wheel with red, green, and blue
filters. This subjects the mirrors to light at each of
the primary colors in a rapid rotating sequence.
The result is a color-modulated image that the
human eye sees as natural color. Advantages of
DLP technology include light weight, high
contrast, and lack of pixelation.

7.  2) The term digital projector is sometimes
used for a program that facilitates the
viewing of three-dimensional (3D),
interactive, full-motion audio-visual files on
a personal computer. Versions are available
for both IBM-compatible and Macintosh
computers, and can be downloaded from the
Internet. They can be used as plug-ins for
popular browsers for viewing animated Web-
page content. For optimum performance on
the Internet, a broadband connection should
be used because of the high-speed,
interactive nature of the content, and
because the transmitted files are often
large.