Automatic Gain Control (AGC)
Most cameras come with an AGC circuit. This circuit examines the brightness level
of the video signal to keep it at a consistent level. For example, if the video signal is
dark, it will attempt to increase the gain to bring the brightness up to a normal level.
Aperture
The aperture is the diameter of the lens
that controls the amount of light reaching the image sensor. It is shown by an f-number.
Larger aperture lenses have smaller f-numbers. For instance, a lens with an f-number of
1.2 will allow more light to reach the sensor than a lens with an f-number of 2.0 thus
producing a brighter image.
Auto Iris Lens
An automatic iris lens is a lens with a motorized iris that automatically adjusts to only
allow a specific amount of light to reach the image sensor. When there is little light,
the iris will open to let more light in. When there is too much light, the iris will close
to reduce the amount of light let in. Auto iris lenses are primarily used in applications
where light levels vary and it would be impracticable to manually adjust the lens.
Automatic iris lenses are generally more efficient than the electronic shutter since they
actually control the amount of light reaching the sensor as opposed to simply adjusting
shutter speed.
B
Back Light Correction
(BLC)
Many Cameras include a BLC circuit. This circuit is used to help correct an image with
more light behind the subject being viewed. Without backlight compensation, the subject
appears dark with little detail. Using the backlight compensation will reduce the
brightness of the light to allow the subject to appear brighter and bring out the details.
C
Camera Format
Refers to the size of the imaging sensor. Common formats are 1/4”, 1/2”,
1/3”, 2/3”, and 1”. The size of the sensor directly affects the field of
view obtained. When using the same size lens on different format sensors, different
viewing areas are obtained. For example, using a 6mm lens on a 1/3” sensor will give
you a 37º field of view. Using the same lens on a 1/2” sensor will increase the
field of view to 56º and 74º on a 2/3” sensor. It is important to make sure you
have a lens that was designed for your camera’s format. The lens must be designed for
at least the size of your sensor. For instance, you can use a 1” format lens on a
1/3” camera, but you cannot use a 1/3” lens on a 1” camera. If you use a
lens designed for a smaller format camera, the image will be vignetted. Also, by using a
lens designed for a larger format sensor, the field of view you get will be greater than
what is specified.
CCD (Charge Coupled Device)
Most of our cameras are CCD in type semiconductor device that is used especially as an
optical sensor and that stores charge and transfers it sequentially to an amplifier and
detector
C Mount Lens
An industry standard for lens mounting. The C-Mount has a thread with a 1 inch diameter
and 32 threads per inch. The distance from the lens mounting surface to the sensor surface
is 0.69 inches (17.526 mm). It is possible to mount a C mount lens onto a CS mount camera
with the use of a CS adapter ring.
CS Mount Lens
An industry standard for lens mounting. The CS-Mount has a thread with a 1 inch diameter
and 32 threads per inch. The distance from the lens mounting surface to the sensor surface
is 0.492 inches (12.5 mm). It is not possible to use a CS mount lens on a C mount camera.
Composite
A single video signal that contains luminance, color, and synchronization information. The
American standard NTSC (525 lines, 30 frames per second) and European standard PAL (625
lines, 25 frames per second) are examples of composite video.
D
Depth of Field
For a lens, the area along the line of sight in which objects are in reasonable focus. 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. Depth of field increases with smaller
lens aperture (higher f-numbers), shorter focal lengths, and greater distances from the
lens.
Digital Recording
The newest form of video archiving and reviewing. Digital recorders are quickly replacing
time lapse recorders as the number one storage media. Digital recording takes advantage of
the speed and reliability of PC hard drives and other computer storage devices such as
high speed DAT media, CD-ROM and even compact flash media. Storage using these devices
virtually eliminates video degradation and tape wear. Digital recording also opens up
almost limitless remote viewing possibilities using standard transmission modes such as
LAN, WAN, ISDN, and the Internet. File security also eliminates image manipulation so you
can be certain the video you see is authentic and unaltered.
F
Focal Length
The distance from the lens to the surface of the imaging sensor when the subject is
focused. Expressed in millimeters. Shorter focal lengths give wider field of view. Longer
focal lengths give narrower (telephoto) views.
Federal Communications Commission (FCC)
An independent US government agency established in 1934 and charged with regulating
interstate and international communications by radio, television, wire, satellite, and
cable. Any wireless equipment must be approved by the FCC in order to be used without
licensing. To receive licensing information, contact the FCC by phone at 888-225-5322 or
on the internet at http://www.fcc.gov/services/amateur/about
Field of View
The width, height, or diameter of a displayed image. It is determined by the lens focal
length, imaging sensor size, and the distance to the subject being monitored. Usually
expressed in degrees horizontal or vertical.
Field
One of the two equal parts into which a television frame is divided in an interlaced
system of scanning. There are 60 fields per second in the NTSC system. The NTSC field
contains 262 1/2 horizontal lines. Adjacent lines in a TV picture (525 Lines total) are
located in alternate fields.
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Hole-Accumulation Diode (HAD)
EXview HAD CCD is a trademark of Sony Corporation. The HAD CCD dramatically improves light
efficiency by including near infrared light as a basic structure of the sensor.
Conventional CCD sensors are sensitive to infrared light but are unable to efficiently
gather the charge. Because of this greater efficiency, HAD CCD sensors achieve
sensitivities approximately 4 times that of a conventional CCD.
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I
Infrared Lighting (IR)
(Infrared) The area below the visible spectrum. B&W cameras are very sensitive to
infrared light and allow the use of infrared illuminators to enhance poorly lit locations
without alerting subjects during surveillance. Color cameras are also sensitive to
infrared light, but require an infrared filter to filter out the red light to keep the
image colors looking natural.
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L
Lux
A unit measuring the intensity of light. Full moon light is about 0.1 lux whereas full
daylight is about 10,000 lux. Most color cameras can produce decent images during deep
twilight. Most black and white cameras need about as much light as produced by a full
moon. With our new HAD and Super HAD CCD cameras, the only light you need is starlight on
a dark night. (about 0.0003 lux)
LCD (Liquid Crystal Display)
Some of our tiny monitors use LCD displays which are a constantly operating display (as of
the time in a digital watch) that consists of segments of a liquid crystal whose
reflectivity varies according to the voltage applied to them.
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M
Microwave
The portion of the electromagnetic spectrum that falls within the range of 300 MHz to 3
GHz. A very efficient transmission band for sending video signals wirelessly. Typical
microwave video links use the following frequencies: 434 MHz, 900 MHz, 1.2 GHz, and 2.4
GHz.
Monochrome
Black and white and all shades of grey. In a monochrome video signal, this is what
controls the brightness of each pixel. Since there is no color, the brightness determines
what shade of gray the pixel needs to be. In a color signal, this also has control over
the brightness of the pixel, whether color or not.
Multiplexer with Multirecord
Capability
Using a multiplexer (as opposed to a quad processor), it is possible to record multiple
cameras full screen with one VCR. Since every video signal is comprised of 30 frames per
second, you can divide these frames among each camera. A multiplexer will send a
camera’s video signal to the VCR at a consistent rate. In the example below we have 8
cameras connected to a multiplexer. Each camera is recorded evenly between 30 frames. In
other words, each camera is recorded for a single frame every 8 frames or every 0.266
seconds. So when the video is played back, each camera appears as though it was recorded
on it’s own time lapse recorder at 3.75 frames per second. The main advantage to
multirecording is the use of a single VCR for multiple cameras.
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Q
Quad Processor
At one time, the only way to view and record multiple cameras on one source, you would
need to use a camera switcher to automatically change between camera views. The main
disadvantage of this setup was you were only capable of recording one camera view at a
time. While you were viewing one camera, the others were “lost.” Now, with newer
digital technology, you are able to record and view more than one camera simultaneously on
one screen. The most basic of these multi-camera processors is the quad. It displays 4
cameras at a time on one screen. There are units that are capable of handling 8 or even 16
cameras, but only 4 can be displayed at a time on a single “page.”
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R
Resolution
The amount of resolvable detail in a picture, or the maximum number of pixels that can be
distinguished either horizontally or vertically. Horizontal resolution is expressed as the
number of distinct vertical lines that can be seen at a distance equal to the picture
height. Vertical resolution is expressed as the number of horizontal lines that can be
seen in the picture.
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S
Super HAD
The Super HAD CCD is a version of Sony’s high performance HAD with improved
sensitivity from the use of more efficient on-chip microlenses. The Super HAD optimizes
the shape of the on-chip lenses in order to minimize the ineffective area between the
lenses on each pixel thereby minimizing lost light and improving the overall sensitivity
per pixel.
Super Dynamic II
This technology lets you capture richly detailed video in scenes with extremely bright and
dark areas. This is accomplished with the double speed CCD that actually captures two
images at different exposures. It then combines the two into one video signal that shows
detail in both bright and dark areas. Compared to a regular CCD, a Super Dynamic II chip
gives you 64 times the dynamic range.
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W
White Balance
Color cameras only. Different lighting sources provide different color temperatures. The
white balance helps correct these differences by adjusting the color processing to bring
the color temperature to a fixed level. Without this balancing feature, due to the
CCD’s poor adaptability, some colors would appear different (green instead of white
in sunlight).
Wavelength
The length of an electromagnetic energy wave as measured from one point on the wave to the
next corresponding point on the wave. Usually measured from peak to peak. The wavelength
determines the characteristics of the wave and determines the color of light if it is
within the visible spectrum. The most common units for measuring wavelengths is the
nanometer (one billionth of a micron), micron, millimeter, and Angstrom
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Z
Zoom/Varifocal Lens
A lens with an adjustable focal length. Varifocal lenses require focusing adjustments
whenever the focal length is changed. Zoom lenses are described by magnification power
according to the difference between the longest and shortest focal lengths. A 5mm to 50mm
zoom lens has a magnification power of 10X. Also, a 10mm to 100mm zoom lens has a
magnification power of 10X. Many different varieties of zoom/varifocal lenses are
available including both manual and motorized versions.
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