AGC
Automatic Gain Control. A circuit for automatically controlling
amplifier gain in order to maintain a constant output voltage with a
varying input voltage within a predetermined range of input-to-output
variation. |
Aperture
In television optics, it is the effective diameter of the lens that
controls the amount of light reaching the photoconductive or
photoemitting image pickup sensor. |
Aperture Correction
Compensation for the loss in sharpness of detail because of the finite
dimensions of the image elements or the dot-pitch of the monitor. |
Aspect Ratio
The ratio of width to height for the frame of the televised picture.
4:3 for standard systems, 5:4 for 1K x 1K, and 16:9 for HDTV. |
Auto Balance
A system for detecting errors in color balance in white and black areas
of the picture and automatically adjusting the white and black levels
of both the red and blue signals as needed for correction.
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Automatic Brightness Control
In display devices, the self-acting mechanism which controls brightness
of the device as a function of ambient light.
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Automatic Gain Control
A process by which gain is automatically adjusted as a function of input or other specified parameter. |
Automatic Iris Lens
A lens that automatically adjusts the amount of light reaching the imager. |
Automatic Light Control
The process by which the illumination incident upon the face of a
pickup device is automatically adjusted as a function of scene
brightness. |
Bandwidth
The number of cycles per second (Hertz) expressing the difference
between the lower and upper limiting frequencies of a frequency band;
also, the width of a band of frequencies. |
Blooming
The defocusing of regions of the picture where the brightness is at an
excessive level, due to enlargement of spot size and halation of the
fluorescent screen of the cathode-ray picture tube. In a camera, sensor
element saturation and excess which causes widening of the spatial
representation of a spot light source. |
Bounce
Sudden variations in picture presentation (brightness, size, etc.,) independent of scene illumination. |
Brightness
The attribute of visual perception in accordance with which an area
appear to emit more of less light. (Luminance is the recommended name
for the photo-electric quantity which has also been called brightness.) |
Broadband
In television system use, a device having a bandpass greater than the band of a single VHF television channel. |
Burned-In-Image
Also called burn. An image which persists in a fixed position in the
output signal of a camera tube after the camera has been turned to a
different scene or, on a monitor screen. |
CCD
Charge
Coupled Device. Often the device is integrated with a sensor, such as a
photoelectric device to produce the charge that is being read, thus
making the CCD a major technology where the conversion of images into a
digital signal is required. |
C Mount
A television camera lens mount of the 16 mm format, 1 inch in diameter with 32 threads per inch. |
CCTV
Common abbreviation for Closed-Circuit Television. |
Chroma
That quality of color which embraces both hue and saturation. White, black, and grays have no chroma. |
Coaxial Cable
A particular type of cable capable of passing a wide range of
frequencies with very low signal loss. Such a cable in its simplest
form, consists of a hollow metallic shield with a single wire
accurately placed along the center of the shield and isolated from the
shield. |
Color Saturation
The degree to which a color is free of white light. |
Composite Video Signal
The combined picture signal, including vertical and horizontal blanking and synchronizing signals. |
Compression
The reduction in gain at one level of a picture signal with respect to the gain at another level of the same signal. |
Contrast
The range of light to dark values in a picture or the ratio between the maximum and minimum brightness values. |
Crosstalk
An undesired signal from a different channel interfering with the desired signal. |
dB
Basically, a measure of the power ratio of two signals. In system use,
a measure of the voltage ratio of two signals, provided they are
measured across a common impedance. |
Decoder
The circuitry in a color TV receiver which transforms the detected
color signals into a form suitable to operate the color tube. |
Depth of Field
The in-focus range of a lens or optical system. It is measured from the
distance behind an object to the distance in front of the object when
the viewing lens shows the object to be in focus. |
Digital Signal Processing
An algorithm within the camera that digitizes data (the image).
Examples include automatic compensate for backlight interference, color
balance variations and corrections related to aging of electrical
components or lighting. Functions such as electronic pan and zoom,
image annotation, compression of the video for network transmission,
feature extraction and motion compensation can be easily and
inexpensively added to the camera feature set. |
Distortion
The deviation of the received signal waveform from that of the original transmitted waveform. |
Distribution Amplifier
A device that provides several isolated outputs from one looping or
bridging input, and has a sufficiently high input impedance and
input-to-output isolation to prevent loading of the input source. |
Field of View
The maximum angle of view that can be seen through a lens or optical instrument. |
Focal Length
Of a lens, the distance from the focal point to the principal point of the lens. |
Frame
The total area, occupied by the television picture, which is scanned while the picture signal is not blanked. |
Gain
An increase in voltage or power, usually expressed in dB. |
Gray Scale
Variations in value from white, through shades of gray, to black on a
television screen. The gradations approximate the tonal values of the
original image picked up by the TV camera. |
Hue
Corresponds to colors such as red, blue, etcetera. |
Interference
Extraneous energy which tends to interfere with the reception of the desired signals. |
Iris
An adjustable aperture built into a camera lens to permit control of the amount of light passing through the lens. |
Jitter
Small, rapid variations in a waveform due to mechanical disturbances or
to changes in the characteristic of components. Supply voltages,
imperfect synchronizing signals, circuits, etc. |
Lens
A transparent optical component consisting of one or more pieces of
optical glass with surfaces so curved (usually Spherical), that they
serve to converge or diverge the transmitted rays of an object, thus
forming a real or virtual image of that object. |
Lens Speed
Refers to the ability of a lens to transmit light, represented as the
ratio of the focal length to the diameter of the lens. A fast lens
would be rated f/8. The larger the f number, the slower the lens. |
Loop Through
Also called looping. The method of feeding a series of high impedance
circuits (such as multiple monitor/displays in parallel) from a pulse
or video source with a coax transmission line in such a manner that the
line is bridged (with minimum length stubs) and that the last unit
properly terminates the line in its characteristic impedance. This
minimizes discontinuities or reflections on the transmission line. |
Lux
International System (Sl) unit of illumination in which the meter is
the unit of length. One lux equals one lumen per square meter. |
Monochrome Signal
In monochrome television, a signal wave for controlling the brightness
values in the picture. In color television, that part of the signal
wave which has major control of the brightness values of the picture,
whether displayed in color or in monochrome. |
Noise
The word "noise" originated in audio practice and refers to random
spurts of electrical energy or interference. In some cases, it will
produce a "salt-and-pepper" pattern over the televised picture. Heavy
noise is sometimes referred to as "snow". |
Non-Composite Video
A video signal containing all information except sync. |
NTSC
Abbreviation for National Television Systems Committee. A committee
that worked with the FCC in formulating standards for the present day
United States color television system. |
Pan and Tilt
A device upon which a camera can be mounted that allows movement in
both the azimuth (pan) and in the vertical plane (tilt). |
Pixel
Short for Picture Element. A pixel is the smallest area of a television
picture capable of being delineated by an electrical signal passed
through the system of part thereof. The number of picture elements
(pixels) in a complete picture, and their geometric characteristics of
vertical height and horzontal width, provide information on the total
amount of detail which the raster can display and on the sharpness of
the detail, respectively. |
Resolution (horizontal)
The amount of resolvable detail in the horizontal direction in a
picture. It is usually expressed as the number of distinct vertical
lines, alternately black and white, which can be seen in a distance
equal to picture height. |
Resolution (vertical)
The amount of resolvable detail in the vertical direction in a picture.
It is usually expressed as the number of distinct horizontal lines,
alternately black and white, which can theoretically be seen in a
picture. |
RF (Radio Frequency)
A frequency at which coherent electromagnetic radiation of energy is
useful for communication purposes. Also, the entire range of such
frequencies. |
Saturation
In color, the degree to which a color is diluted with white light or is
pure. The vividness of a color, described by such terms as bright,
deep, pastel, pale, etc. Saturation is directly related to the
amplitude of the chrominance signal. |
Sensitivity
In television, a factor expressing the incident illumination upon a
specified scene required to produce a specified picture signal at the
output terminals of a television camera. |
Signal-to-Noise Ratio
The ratio between useful television signal and disturbing noise or snow. |
Tearing
A term used to describe a picture condition in which groups of
horizontal lines are displaced in an irregular manner. |
Vertical Resolution
The number of horizontal lines that can be seen in the reproduced image of a television pattern. |
Video Amplifier
A wideband amplifier used for passing picture signals. |
Zoom
To enlarge or reduce, on a continuously variable basis, the size of a
televised image primarily by varying lens focal length. |
