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Glossary 63
dB — decibel — A unit used to express relative difference in power or intensity,
usually between two acoustic or electric signals, equal to ten times the common
logarithm of the ratio of the two levels.
Diagonal Screen — A method of measuring the size of a screen or a projected
image. It measures from one corner to the opposite corner. A 9 FT high, 12 FT
wide, screen has a diagonal of 15 FT. This document assumes that the diagonal
dimensions are for the traditional 4:3 ratio of a computer image as per the example
above.
DLP
®
— Digital Light Processing™ — Reflective display technology developed by
Texas Instruments, using small manipulated mirrors. Light passing through a color
filter is sent to the DLP mirrors which arrange the RGB colors into a picture
projected onto screen, also known as DMD.
DMD — Digital Micro-Mirror Device — Each DMD consists of thousands of
tilting, microscopic aluminum alloy mirrors mounted on a hidden yoke.
Focal Length — The distance from the surface of a lens to its focal point.
Frequency — It is the rate of repetition in cycles per seconds of electrical signals.
Measured in Hz (Hertz).
HDCP — High-Bandwidth Digital-Content Protection — A specification
developed by Intel™ Corporation to protect digital entertainment across digital
interface, such as DVI, HDMI.
HDMI — High-Definition Multimedia Interface — HDMI carries both
uncompressed high definition video along with digital audio and device control
data in a single connector.
Hz (Hertz) — Unit of frequency.
Keystone Correction — Device that will correct an image of the distortion
(usually a wide-top narrow-bottom effect) of a projected image caused by
improper projector to screen angle.
Maximum Distance — The distance from a screen the projector can be to cast an
image that is usable (bright enough) in a fully darkened room.
Maximum Image Size — The largest image a projector can throw in a darkened
room. This is usually limited by focal range of the optics.
Minimum Distance — The closest position that a projector can focus an image
onto a screen.
NTSC — National Television Standards Committee. North American standard for
video and broadcasting, with a video format of 525 lines at 30 frames per second.
PAL — Phase Alternating Line. A European broadcast standard for video and
broadcasting, with a video format of 625 lines at 25 frames per second.