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GLOSSARY
Curved screens usually have larger gain than flat screens.
Help Screen A display of help information regarding the current task or presentation.
Horizontal Frequency The frequency at which scan lines are generated, which varies amongst sources.
Also called horizontal scan rate or line rate.
Horizontal Offset The difference between the center of the projected image and the center of the pro-
jector lens. For this projector, this value is expressed as the maximum percentage
of the image that can be projected to one side of the lens center without degrading
the image quality. Horizontal offset ranges can be affected by the type of lens in
use, and whether or not the image is offset vertically at the same time.
Hot Spot A circular area of a screen where the image appears brighter than elsewhere on the
screen. A hot spot appears along the line of sight and "moves" with the line of
sight. High gain screens and rear screens designed for slide or movie projection
usually have a hot spot.
Input A physical connection route for a source signal, described by a 2-digit number rep-
resenting 1) its switcher/projector location and 2) its slot in the switcher/projector.
Input Signal Signal sent from a source device to the projector.
Interface A device, such as the Serial Digital Input Module, that accepts an input signal for
display by the projector.
Interlace A method used by video tape players and some computers to double the vertical
resolution without increasing the horizontal line rate. If the resulting frame/field
rate is too low, the image may flicker depending on the image content.
Keypad A small push-button device for controlling most projector settings and operation.
For more information, refer to 3.3, Using the Keypad.
Keystone A distortion of the image which occurs when the top and bottom borders of the
image are unequal in length. Side borders both slant in or out, producing a key-
stone shaped image. It is caused when the screen and lens surface are not parallel.
Linearity The reproduction of the horizontal and vertical size of characters and/or shapes
over the entire screen.
Line of Best Viewing When light from a projector is incident on a screen, the light reflects from the
screen such that the angle of reflection equals the angle of incidence. The Line of
Best Viewing is along the line of reflection.
Loop through The method of feeding a series of high impedance inputs from a single video
source with a coaxial transmission line in such a manner that the line is terminat-
ed with its characteristic impedance at the last input on the line.
Lumen The unit of measure for the amount of visible light emitted by a light source.
Lux The amount of visible light per square meter incident on a surface.
1 lux = 1 lumen/square meter = 0.093 foot-candles
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