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28 3M Multimedia Projector MP8620 3M 1997
Glossary
Glossary of Terms
Amorphous Silicon
See Thin-Film Transistor.
Composite video
A video signal that combines all color and timing components of the picture in a single input line. The
U.S. standard is NTSC. European standards are PAL and SECAM.
Hz, KHz, MHz (Hertz, Kilohertz, Megahertz)
Hertz is a unit of measurement used to express the frequency, in cycles per second, of an electrical signal
or event. (Kilohertz = 1000, Megahertz = 1 million cycles per second).
Keystone correction
Keystoning (distorted image) is caused when the path of the projector light beam is not perpendicular to
the screen. Projectors normally project the image with an angle (e.g. 16
°
) on the screen. The optical
system can be designed for distortion free projection at this angle (keystone correction).
Lumens
A measure of light output 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.
Metal halide lamp
A metal halide lamp is a modified mercury arc lamp that is extremely bright. It is filled with a gas with
elements known as “halogens”. The properties of this fill gas allows the lamp to burn longer and
brighter than ordinary incandescent lamps.
NTSC (National Television Systems Committee)
Standard for television signals and other video equipment signals. Uses interlaced scans and 525
horizontal lines per frame at a rate of 30 frames per second.
PAL (Phase Alternate Line)
The format for color television signals used in England, Germany, the Netherlands, and several other
countries. PAL is an interlaced format with 25 frames per second and 625 lines per screen.
Pixel
Short for “picture element.” Unique position on a display that consists of a single dot or group of three
dots (red, green & blue). Total pixels are usually expressed in horizontal x vertical dimensions (e.g. 640
x 480).
Power ON/OFF switch
The power ON/OFF switch is used to turn the machine on and off. The power switch is located on the
back of the projector in the lower left-hand corner.
Refresh rate
The number of times the screen image is “painted” or refreshed per second, expressed in Hz.