|Technical Terms Glossary
Projection System | Overhead Projector
Projection System Terms
IBM high-resolution video standard of 1024 x 768 (interlaced).
pixel is actively controlled by a diode or a transistor. Advantage: allows
each pixel to be independently controlled.
lumens is a scale to measure the overall brightness value for projectors.
The measurement represents the average value of 9 points on the projected
between the width and height of the output (whether it is a monitor, LCD
projection panel, overhead or slide).
National Standards Institute.
Graphics Adapter. This is the card added to an IBM® PC & XT that
gives the computer the ability to handle graphics and color. Resolution
of this card is 640 x 200 pixels.
signal that combines all the color and timing components of the image into
a single input line.
of displaying images in a reduced size format. A compressed image usually
has part of the image information discarded. The result is a projected
image that has light and dark lines and text characters with thick and
thin line widths.
of the brightest and darkest images a display can reproduce.
of the red, green, and blue video image signal on a projected display system.
size is the diagonal length of the LCD plate. Typical sizes are 8.4" to
Super Twist Nematic. Where two separate LCD plates are combined to form
a single panel.
that amplifies and transmits a video signal over a distance using shielded
Graphics Array. This card is the second generation of the CGA card in that
it gives IBM PCs, XTs and ATs greater resolution (640 x 350 in all models).
or (Kilohertz or Megahertz). Cycles per second. (Kilo = 1,000, Mega = 1
million). These terms are used to express the frequency of an electrical
signal or event.
higher resolution images into 640 x 480.
other line is scanned during each total vertical (full) screen refresh.
of wireless transmission using infrared light waves.
line is scanned during each total vertical (full) screen refresh.
Television Standards Committee. The standard for broadcast color television
and other video equipment signal in North America, established in 1953.
525 lines/60 Hz.
Alternate Line. The phase of the color carrier alternates from line to
line. PAL is used extensively in Western Europe. 625 lines/50Hz.
of colors available for use in creating an image. The use of a standardized
palette in a presentation allows the user to create a consistent look.
as liquid crystal display (LCD).
of simple driver electronics in an LCD projection panel where the pixels
are turned on and off using a row-and-column format. The amount of control
on each pixel is limited, which results in lower contrast ratios and a
slower response time than active-matrix LCD projection panels.
position on a display that consists of a single dot or group of three dots
(red, green and blue). Total pixels are usually expressed in horizontal
x vertical dimensions (e.g., 640 x 480).
TFT is a type of LCD technology that allows more light at high temperatures
through the LCD.
of times the screen image is "painted" or refreshed per second, expressed
is the ability of an imaging system to faithfully reproduce fine detail
information and transitions between dark and light parts of an image. The
more pixels the display systems can address (e.g., 800 x 600 ) the higher-quality
image with more detail.
it takes for a pixel to turn on and off. Typically measured in milliseconds,
an active-matrix LCD projection panel's response time is fast enough to
display full-motion video and rapid mouse cursor movements.
Green, Blue. The basic signal components of the color video system.
Couleur Avec Memorie. The color television standard developed in France.
SECAM is used mostly in France and Eastern European countries. 625 lines/50Hz.
I/O port on the computer enabling other devices or computers to link with
the computer. Also referred to as RS-232C or COM port.
of 800 x 600. This standard has versions with different vertical frequencies.
signal that separates luminance (Y) and chrominance (C) signals.
Film Transistor. This is a developing technology that attempts to place
the controller of the panel directly on the surface of the glass.
of the light that is transmitted off the stage of the overhead projector
that reaches the screen at a given distance. Typically, LCD projection
panels are able to use less than 10% of the total light available.
Super Twist Nematic. Where three separate LCD plates are combined to form
a single panel.
Electronics Standards Association. A non-profit group of companies organized
to define and improve computer graphics standards. VESA standards usually
achieve a higher display quality by increasing the resolution (e.g., 1024
x 768) while maintaining a high vertical refresh rate (e.g., 72 Hz) to
of display specifications agreed upon by the VESA organization, usually
referred to by resolution and vertical refresh rate.
Graphics Array. This is the standard interface for the IBM PS/2®. It
is the only analog graphics card IBM has used (other cards handle digital
information) 720 x 400 in the text mode, graphics mode 640 x 480 resolution.
to project images from a VCR, laser disc, or PC with CD-ROM drive.
lightweight remote control offers all of the functionality of a computer-compatible
Graphics Adapter. IBM's graphics standard that includes VGA and extended
resolution up to 1024 x 768.
many computers, there is only one monitor output. Subsequently, a cable
is necessary that will split the monitor signal so it will work simultaneously
with both a monitor and an LCD projection panel.
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AC power outlets for connecting accessory items such as notebook computers.
of the stage that is available for projecting an image. Usually comes in
the following sizes: 10" X 10", 10.5" X 10.5" and 11.25" X 11.25" (A4).
projector head, where the mirror will move one-half the distance when the
image is tilted up on the screen.
coating on a reflective optical stage (Fresnel lens) that resists scratching,
so that the projected visuals stay sharp and clear.
the edge-to-edge uniformity of the projected light to eliminate yellow
or blue corners. This gives an optimized image, no matter what the projector-to-screen
distance, within the prescribed area.
head where the mirror and lens is enclosed.
of the projector lamp by the upward flow of heated air, without the use
of a fan. Usually used in reflective-type projectors that have the lamp
installed into the head assembly.
lens that has two elements contained in a single assembly.
that the projected image can be tilted to, and still project a full image
onto the screen.
enlargement lens used to enlarge LCD projection panel images.
given to a lens, stated in inches or millimeters. The smaller the focal
length, the wider the angle of the image. Focal length is the distance
between the lens and its focal point.
that is used when it is necessary to project an image onto a vertical surface
(such as a wall) with a high tilt angle of the head, making it possible
to obtain uniform focus from top to bottom of the image. This feature does
not eliminate keystoning.
lens that is composed of a series of closely spaced grooves that control
the refraction of light. It is usually part of the stage.
switch that decreases (LOW) the lamp output by 10% and doubles the lamp
life. The HIGH setting should be used with LCD projection panels.
of light projected onto a screen or other surface. Stated in lumens.
is caused when the projected image is not perpendicular to the screen.
Correct keystoning by tilting the screen until it is perpendicular to the
light beam axis.
mechanism that allows easy exchange of replacement lamps by rotating a
replacement lamp into operation position after the primary lamp has failed.
Crystal Display (LCD)
panel that sits on top of the projector stage, which creates an image that
is generated by a computer.
of illumination on a screen or other surface. One lumen is the light of
one candle power on each square foot of a surface of a sphere at a radius
of one foot from the light source.
head where the mirror and lens is not enclosed. The image is raised on
the screen by tilting the mirror up.
the lamp off if the projector reaches an unsafe temperature.
that allows the projector fan to continue to run after the lamp has been
turned off, which reduces the temperature of the unit.
projector where the light source is located in the head assembly and shines
down onto the stage. The light is then reflected from the Fresnel lens,
back through the head and onto the screen. Usually used in lightweight,
lens that has only one element.
area of the projector where the transparency film or LCD projection panel
projector where the light source is under the stage and light is transmitted
through the transparency film to the head and onto the screen.
lens that has three elements contained in a single assembly.
lens containing movable elements to permit focusing of the image by varying
the focal length. (Not a zoom.)
that will project a larger image on a screen at a closer distance than
a standard lens will project. Usually has a focal length of 11.5" (293
mm) or smaller.
PS/2 are registered trademarks of IBM Corporation.
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