Digital Light Processing
Television and projection digital lightprocessing (DLP) technology is based on a
semiconductor invented in 1987 by Texas Instruments. The basic technology in a
DLP monitor consists of millions of microscopic mirrors that direct light toward
or away from pixels. The pixels control the amount of light reflected off of a mir-
rored surface. DLP monitors have excellent color reproduction and contrast, and
are lightweight. The monitors are deeper or thicker than plasma and LCD monitors,
because DLP uses a lamp. DLP technology isused in many rear screen projectors.
Liquid Crystal Displays
LCDs use a fluorescent backlight to send light through liquid crystal molecules.
LCD monitors apply voltage to the pixels to adjust the darkness of the pixels,
thus preventing the backlight from showing through. Many LCDs double as
computer displays. An LCD can be as large as 55 inches. LCDs are very thin,
lightweight and have good color reproduction and sharpness.
Cathode Ray Tube
CRTs use a vacuum tube that produces images when a phosphorescent surface
is excited. The dot pitch (DPI or dots per inch) of a monitor (the distance
between the dots) is a measure of the quality of resolution. CRTs have a large
dot pitch, which means a lower resolution quality, but CRTs produce a brighter
picture. CRTs have excellent color and contrast but tend to be big and heavy.
Audio Visual Control Systems
A control system has to simultaneously manage all various components of the
audio visual system. A presenter or user may want to lower a ceiling-mounted
projector, start the DVD or perform other related tasks. Some elements of an audio
visual presentation system that may needto be controlled appear in the list on the
next page.
Local control of most audio visual systems may be a series of control but-
tons and switches located on a wall within the room, a wireless device
controlling a projector, display or other component, or a touchscreen on a
computer. Traditional system controls may include relays, remote controls,
and proprietary manufacturer controls. More often the control system for
audio visual systems consists of a personal computer, personal computer soft-
ware, and a data network utilizing Ethernet and IP protocols.
Although digital audio and video content can be transmitted over a data
network most of the evolution of audio visual systems to data networks has
been in the administration and control of the components. While some
Audio Visual Systems 175