Video cameras are used in machine vision, quality monitoring, security, and
remote monitoring for industrial and commercial operations. Consumer video
cameras are not covered in this search form. Video cameras can operate in
monochrome or color. Monochrome is black and white, or grayscale; the image is
presented in black, white, and grayscale. The range of colors is generated with
varying combinations of different discrete colors. One common technique is
sensing the red, green, and blue components (RGB) and combining them to create a
wide spectrum of colors. Multiple chip color is a method of capturing color in
which multiple chips are each dedicated to capturing part of the color image,
such as one color, and the results are combined to generate the full color
image. They typically employ color separation devices such as beamsplitters
rather than having integral filters on the sensors. Choices for imaging
technologies for video cameras include CCD, CMOS, tube, and film. Charge Coupled
Devices (CCD)Â use a light-sensitive material on a silicon chip to detect
electrons excited by incoming light. CMOS image sensors operate at lower
voltages than CCDs, reducing power consumption for portable applications. In a
tube camera, the image is formed on a fluorescent screen. Image is exposed onto
photosensitive film, which is then developed to be played or
stored.Â
Important performance specifications to consider when searching
for video cameras include horizontal resolution, maximum frame rate, shutter
speed, sensitivity, and signal-to-noise ratio. Horizontal resolution is the
maximum number of individual picture elements that can be distinguished in a
single scanning line. It is most common to characterize horizontal video
resolution corrected for the image aspect ratio, or specify the resolution in
the largest circle than can fit in a rectangular image. Thus, for example a 640
x 480 image would be specified as 480 horizontal lines. Maximum frame rate is
the number of frames that can be captured per unit time, typically frames per
second. Shutter time is the time of exposure or light collection. Typically
may be set across a wide range. Sensitivity refers to minimum scene
illumination for good image quality. The standard unit for illuminance is lux,
or lumens per square meter (lm/m2). Signal-to-Noise ratio is defined
as the peak-to-peak camera signal output current to the RMS noise in the output
current. This ratio represents how prevalent the noise component of a signal,
and thus the image uncertainty, is in the total signal. Noise sources include
sensor "dark current," electromagnetic interference, and any other spurious
non-image signal elements. Higher SNR numbers represent less image degradation
from noise.
Analog video formats used by video cameras include NTSC, PAL,
SECAM, RS170, RS330, and CCIR. Digital output interfaces common to vision
sensors include RS232, RS422, RS485, parallel interfaces, Ethernet, DeviceNet,
ARCNET, PROFIBUS, CANbus, Foundation Fieldbus, IEEE 1394 (Firewire), Modem,
SCSI, TTL, USB, and radio or wireless. Choices for bits or pixels include 8
bits, 10 bits, 12 bits, 14 bits, or 16 bits. Color outputs are typically RGB, Y
PbPr, Y/C (S-video), or composite.
Other parameters
to consider when specifying video cameras include specialty applications,
performance features, physical features, lens mounting, shutter control, sensor
specifications, dimensions, and operating environment parameters.
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About Video Cameras
