Aliasing: Interference phenomenon which occurs when a sampled signal
contains frequencies that are higher than half the sampling frequency. A
CCD samples the picture spatially. An optical low-pass filter is used to
avoid aliasing, especially in color applications.
Aperture correction: Camera signal processing function which adjusts
the enhancement of edges of objects in a picture.
Aspect Ratio: The ratio of width over height of an image, 4:3 for a
standard TV image, 16:9 for wide screen.
Asynchronous transmission mode: IEEE 1394 data transmission mode
without a guaranteed data delivery time. Used in IEEE 1394 cameras for
control functions and reports.
Auto Exposure (AE): Combined use of Automatic Gain Control and iris motor control
allows shooting in a broad range of lighting conditions. Automatic Gain Control amplifies
the video signal in low light conditions, iris reduces it in high light
conditions. Motor iris control can be replaced by the CCD IRIS control.
Autofocus (AF): Available in cameras equipped with motorized focus, this
feature provides automatic adjustment of the focus. AF operates by
varying the focus to maximize the high frequency content of the central
area of the picture by reference to high luminance and strong contrast
Automatic Gain Control (AGC): Circuitry that automatically adjusts the
electronic amplification of the video signal to compensate for varying
levels of scene illumination.
Auto Tracking White balance (ATW): In ATW mode, white balance is
continuously being adjusted according to the color temperature of the
Backlight compensation: Special compensation option in AE (Auto
Exposure) mode. When the background is too bright and/or when the
subject is too dark, backlight compensation modifies the action of Auto
Exposure to make the subject appear clearer.
Bayonet mount: Type of camera mount in which there is 38 mm or 48 mm
clearance between the lens rear mounting surface and the camera’s CCD.
Black stretch / Black Compress Control: A function of Digital Signal
Processing technology that enables the contrast of the black area of an
image to be variable adjusted. The black stretch function emphasizes
contrast in the dark areas while black compress enhances or deepens
Camera Control Unit (CCU): The CCU provides a means of controlling
a remote camera. So that the remote camera can be as small and light as
possible, the CCU also includes all electronic circuits that do not have to
be fitted inside the remote head, these are typically signal processing
circuitry, input/output interfaces and power supply.
Camera Head Unit (CHU): In a remote head camera system, the CHU is
a small unit that only includes the sensor, its optical interface, the cable
coupling to a CCU and the minimum amount of electronic circuitry.
CCD (Charge Coupled Device): Semiconductor device made of a
matrix (or lines) of individual photosensitive elements, called pixels. The
optics focus the scene onto the matrix and each pixel accumulates an
electric charge proportional to the local intensity of received light and to
the integration time. At read out time, all charges are transferred at the
same time to an output matrix protected from light, where a sequential
reading may take place while a new picture starts integrating. The output
matrix size is half that of the sensitive matrix size for interlaced mode
CCDs, and the same size for progressive scan CCDs.
CCD IRIS: Special operating mode of the electronic shutter of a CCD
camera. The shutter timing is automatically adjusted to maintain the same
video output level, irrespective of the scene illumination. Can only reduce
the camera sensitivity. Allows the use of a fixed iris lens under variable
lighting conditions. Often combined with AGC.
CCIR: B/W video standard with 625 lines / frame, 2 interlaced fields /
frame, 25 frames / second. Monochrome version of PAL.
Chrominance: Color part of the composite video signal. Also called C.
Separately transmitted in Y/C (S-video). It is the combination of the two
color difference signals (U or R-Y) and (V or B-Y) modulated on to a
subcarrier. See also YUV.
C-Mount: Type of camera mount in which there is 17.526 mm clearance
between the lens rear mounting surface and the camera’s CCD.
Composite sync: Combination of the HD and VD in one signal.
Commonly used as a synchronizing or genlock signal in B/W systems.
Depth of field: Distance between the nearest and farthest points in a
scene that are in focus as viewed by a particular lens. Affected by choice
of lens focal length and iris aperture. Increases with both decreasing lens
focal length and decreasing iris aperture.
Digital Signal Processing (DSP): Inside a camera, sensor signals must
be processed in several steps before they can be displayed / transmitted.
Typical processing steps are amplification, gamma correction, black level
correction, highlight compression/clipping, edge enhancement, color
processing, color balance, color correction, output signal encoding.
Picture quality is highly dependent on the accuracy and the stability of
these processes. In DSP technology, the sensor signal is converted to
digital form after initial amplification, and all processing is achieved
digitally, ensuring high quality and no drift. Output signals remain in
digital form or are converted back to analog depending on the camera
Electronic shutter: CCD camera operating mode where the integration
time can be shortened without any mechanical device. Used for blur
reduction when capturing fast moving objects, and for camera sensitivity
reduction in high levels of scene illumination.
Electronics Industries Association (EIA): B/W video standard with 525
lines / frame, 2 interlaced fields / frame, 30 frames / second.
Monochrome version of NTSC video signal. Also referred to as RS-170.
Exwave HAD technology: Technology with a nearly gapless OCL
(On-chip-lens) located over each pixel of the CCD resulting in more than
twice the sensitivity and 1/50 the smear compared to Hyper HAD
F Stop, F Number: Calibrated measure of lens iris aperture. Common F
stops are F1.4, F2, F2.8, F4, F5.6, F8, F11, F16, F22. The higher the number,
the smaller the iris aperture and the less light falling on the imager.
Field: Half of a TV picture consisting of only the odd or only the even lines.
NTSC/EIA features 60 fields of 262.5 lines / second. PAL/CCIR features
50 fields of 312.5 lines / second. Odd / even field pairs recombine on
screen as frames due to picture tube and human eye memory.
Field / frame integration: Two different pixel readout techniques in
CCDs designed for interlaced output. Refers to the total integration time,
field duration (16.6 ms NTSC/EIA or 20 ms PAL/CCIR) or frame duration
(33.3 ms NTSC/EIA or 40 ms PAL/CCIR). Both modes give the same
In field integration, pixels of two adjacent lines are read out together as
one. The full CCD is read every field, achieving higher picture refresh rate
but lower vertical resolution. Mostly used in current applications to
achieve optimum capture of movement. Adjacent lines are combined
differently for odd (1+2, 3+4, . . .) and even field (2+3, 4+5, . . .) outputs.
In frame integration, pixels are read out separately. The complete CCD is
read after two fields. Full vertical resolution is achieved. Progressive scan
CCDs operate only in frame integration.
Focal length: Distance between the optical center of a lens and the
image focal point. Fixes the magnification and the angle of view of a lens.
Vari-focal and zoom lenses have a variable focal length.
Frame: One complete TV picture consisting of two sequential interlaced
scanned fields. NTSC/EIA has 30 frames of 525 lines per second.
PAL/CCIR has 25 frames of 625 lines per second.
Gain: The electronic amplification factor of a signal.
Gamma: Correction law introduced in the camera output signal to
compensate for the non-linearity of the CRT (Cathode Ray Tube) in video
monitors. A typical gamma value is 0.45, which results in the brightness
component of the CRT picture appearing to be linear.
Genlock: Circuitry that synchronizes one video signal to another video
signal. There are three types of genlock: V-lock, HV-lock and full color.
• V-lock is useful when simply switching from one B/W color source to
• HV-lock is used for full synchronization of B/W cameras, and requires a
HD + VD input, composite sync input or composite VS video signal
input. In the case of color cameras, this type of synchronization can be
used when cutting between pictures, but not for mixing between them.
• Full color genlock is used when pictures have to be mixed without color
degradation. It needs VBS composite video input.
HAC: Host Adapter Card.
HAD (Hole Accumulated Diode): CCD technology with improved
performance in spectral response, vertical smear and sensitivity. The HAD
sensor also introduced a higher pixel count and electronic shuttering
HD (Horizontal Drive): Signal used to synchronize the line scan rate of
the camera to an external source. Mostly used in B/W applications
together with VD.
High rate scanning: Capability of a camera to output less than its
maximum number of horizontal lines, but at a higher rate. Unlike partial
scanning, the lines output in high rate scanning are symmetrical about the
optical sensor center. This means that there is normally no need to re-aim
the camera when changing from normal to high rate scanning.
Horizontal Resolution: Number of equally spaced vertical black-to-white
or white-to-black transitions that the camera is able to reproduce, divided
by the aspect ratio (usually 4:3) to make a comparison between
horizontal and vertical resolution easier. Usually expressed as TV lines per
picture height. Indicates the amount of horizontal details that can be
perceived. Horizontal resolution is limited by the number of pixels in one
line and by the type of color filter used, if any.
Hyper HAD: A derivative of the HAD sensor that incorporates microscopic
lenses mounted over each sensing pixel. Hyper HAD sensors have no
perceptible smear and are nearly twice as sensitive as HAD sensors.
ICR (IR Cut Removable): This function is useful in low light
environments. With the IR cut filter removed, the sensitivity of the camera
to IR illumination is increased.
IEEE 1394: A digital networked serial interface for high-speed data
transmission. Available speeds are 200 and 400 Mb/s. IEEE 1394 is an ideal interface
between a computer and audio/video products because of its ability to
transfer a real-time data stream at low cost, with high reliability and ease
Interlaced scanning: Scanning method in which half of the lines are
scanned in one field (odd-numbered lines), and the other half are
scanned in the next field (even-numbered lines). Thus adjacent lines of a
complete picture (one frame) belong to successive fields. Interlaced
scanning doubles the screen refresh rate as seen by the viewer and
reduces flicker. At screen refresh rates significantly higher than the 25/30
frames/second used in TV systems, interlaced scanning may not be
Interline Transfer (IT): In IT CCD technology, the charges on exposed
pixels are transferred to light-shielded vertical readout zones embedded
in the sensitive area. IT devices are simpler to manufacture and are
therefore less costly than FT or FIT devices. Mostly used in industrial and
Interval Auto Focus: AF (Auto Focus) mode is periodically switched ON, then
OFF (fixed focus). The duration of the on and off intervals is separately
Iris: An adjustable sized aperture in a camera lens that controls the
amount of light reaching the imager. Compensates for changing lighting
conditions. Iris control may be either manual or automatic, depending on
the application and the type of camera. When iris is fixed, a variable
electronic shutter can be used instead (CCD Iris).
Isochronous transmission mode: IEEE 1394 data transmission mode
featuring guaranteed transmission timing and bandwidth. Appropriate for
just-in-time transmission of video and audio and computer data.
Long-term integration: Special camera mode similar to the ‘B’ setting of
a photographic camera shutter. The CCD integrates over a long (userdefined)
period, providing very high sensitivity. Object must be stationary,
external camera control and a frame memory are needed.
Luminance: The part of a composite video signal that expresses
brightness. Also called Y. Separately transmitted in Y/C (S-video).
Lux (lux): The SI measurement of light intensity taken at the surface
which the light source is illuminating. The measure of the total lumens
falling upon a unit of area. 1 lumen per square meter. One Foot-candle
equals 10.76 lux.
Minimum illumination: Minimum light level needed to achieve a 50% or
100% video output level when the camera is at maximum gain and the
lens iris fully open. Can be computed from the nominal sensitivity, lens
characteristics and maximum gain.
Minimum Object Distance (MOD): A lens parameter that defines the
minimum distance from a camera lens to the point where an object can
still be in focus.
Modulation Transfer Function (MTF): Defines the resolution capability
of a lens. Most lenses exhibit their best MTF when operated in the middle
of their iris aperture range.
Motion Detector (MD): Camera feature where a reference field is
compared with current fields. If a difference is detected, the camera
outputs a pulse. An ideal feature for security application.
Neutral Density Filter (ND Filter): A grey filter added in front of a lens to
reduce the amount of incoming light into the camera lens. It has no
influence on color.
NF Mount: Type of camera mount in which there is 12 mm clearance
between the lens rear mounting surface and the camera’s CCD.
NTSC (National Television System Committee): Color video standard,
used mainly in the United States and Japan. NTSC uses 525 scanning
lines per picture, 30 pictures (frames) per second, each frame is made up
of two sequential fields containing respectively the even and the odd
One-push AF (One-push Auto Focus): Focus hold mode that can be
automatically readjusted as required by the user (One-push AF Trigger)
assuming that the required subject is within the focusing limits of the
One-push WB (One-push White Balance): Fixed white balance mode
that can be automatically readjusted as required by the user (One-push
WB Trigger), assuming that a white object, in suitable lighting conditions
and occupying more than half of the image area, is seen by the camera.
PAL (Phase Alternation, Line): Color video standard pioneered in
Europe but also used in many other parts of the world. PAL uses 625
scanning lines per picture, 25 pictures (frames) per second, each frame is
made up of two sequential fields containing respectively the odd and the
even lines (interlace).
Partial Enhance: An advanced function of the Digital Signal Processing
(DSP) technology that allows a particular color to be selected and its
hue, saturation and detail altered. This function gives the subject a
pleasing complexion with a softer image while maintaining the sharpness
of other areas, and vice versa. The designated active area of partial
enhance can be set with the digital circuits by simply adjusting the Area
Pixel: Picture element.
PowerHAD: PowerHAD is further improvement of the Hyper HAD CCD
technology, where the microscopic lenses focus more light onto the light
sensors thus increased sensitivity and reduced smear.
Progressive Scan: CCD design that allows the acquisition of both odd
and even fields at the same time. Progressive scan makes full vertical
resolution possible in Donpisha mode.
RGB (Red, Green, Blue): The primary colors of light that produce a
color video image. In video, RGB refers to a system in which these three
primary colors are kept isolated and delivered from the source to the
display device over separate wires. This system results in high-quality
pictures. RGB signals are used in some broadcast video equipment and
RS-232C: Serial data transmission standard for computers which can
also be used to control camera functions.
Screen Mode: Partial see-through mode on HMD allowing the user to
view the surrounding environment by adjusting the transparency of the
screen in the area only around the picture.
Sensitivity: Lens iris aperture required to provide a video output signal of
standard level at a specified light input.
S/N (Signal to Noise Ratio): The ratio, usually expressed in dB
(decibels), between the normal signal output and the noise level within an
Smear: Undesirable artifact of CCDs that appears in the picture as a
vertical streak above and below a very bright object in the scene. Smear
is caused by parasitic light getting into the vertical transfer registers. It is
greatly reduced by the microlens-type of CCD used in Hyper HAD and
Power HAD sensors. Almost suppressed in FIT CCDs.
Square pixel: Used to qualify a CCD sensor where the centers of the
pixels are equally spaced horizontally and vertically. Pictures captured
from this type of non-square pixel sensor need to be software corrected
in order to achieve the correct picture geometry.
Sync (Synchronization): When synchronized, the horizontal and vertical
timing of a camera output are locked to an external signal coming, for
example, from another camera. Picture outputs from both sources are
then precisely synchronized and can be mixed. When mixing color signals,
the subcarriers of the two signals also have to be in synchronism.
Subcarrier: The 4.43 MHz (PAL) or 3.59 MHz (NTSC) signal that is used
as a carrier for the color information. This subcarrier is modulated in
amplitude by the color saturation and in phase by the color hue. A
sample of the unmodulated subcarrier is placed before the start of each
horizontal line, and is called the Color Burst.
U and V: The names given to the two video color difference signals
(R-Y and B-Y) in their coded form in the PAL or NTSC color systems.
See also Y/R-Y/B-Y.
Ultra mount: Type of camera mount in which there is 6.7 mm clearance
between the lens rear mounting surface and the camera’s CCD.
VBS (Video + Burst + Sync): The composite video signal, including color
VD (Vertical Drive): Signal used to synchronize the field rate of a camera
to an external source. Mostly used in B/W together with HD (Horizontal
Vertical Resolution: Number of equally spaced horizontal black-to-white
or white-to-black transitions that a camera is able to reproduce. Indicates
the amount of vertical details that can be perceived. Vertical resolution is
limited by the number of scanning lines that are fixed by the TV standard.
VISCA (Video System Control Architecture): RS-232C serial control
protocol intended to interface up to seven items of video equipment on
one computer link.
V-Lock Sync: see Genlock.
VS (Video + Sync): The composite monochrome video signal commonly
used as the genlock signal in B/W systems.
White Balance (WB): In a color camera, white balance is the process of
adjusting the values of its color differences signals so that a white object
in a scene illuminated by a particular source of illumination is displayed as
a white or grey (i.e. no chrominance).
Y/C (also called S-Video): Separate signals for the Luminance and
Chrominance parts of the video signal. Allows higher picture resolution
and suppresses cross color effects. Connector is the 4-pin mini-DIN.
Y/R-Y/B-Y: Three signals, luminance (Y) and two color difference signals
R-Y (red minus luminance) and B-Y (blue minus luminance) which together
carry the brightness and color information of color images . Color
difference signals have no light intensity information, and cannot be
displayed separately from Y. Compared to RGB signals, they can travel
over longer cables lengths without significant resolution loss, and allows
different spatial resolutions for luminance and color. Typically used for
high-end visual applications. Also known as component signals.
See also U and V signals.