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Cognex CDC Series Camera Description
Cognex MVS-8100D and CDC Cameras Hardware Manual
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CDC series cameras support these shutter modes as follows:
•
The CDC-50 camera can be set with software commands to use either global or
rolling shutter mode
•
The CDC-100 camera always uses rolling shutter mode
•
The CDC-200 camera always uses global shutter mode
An Introduction to CogLink
CogLink is Cognex’s proprietary high performance digital camera interface. CogLink
specifies both a communications protocol and a high-speed serial bus interface for
transmission of both camera image data and camera control commands.
Traditional analog and digital camera standards are faced with finding a way to
separately transmit camera image data and camera control commands. The usual
solution has been a two-cable system, with one cable carrying analog or digital data
from the camera’s sensors to the frame grabber’s memory, and another cable carrying
control commands through a slower serial or parallel connection, such as RS-232.
CogLink uses the Bus Low Voltage Differential Signaling (Bus LVDS) standard. Bus
LVDS is a variation of the LVDS technology specified in the EIA 644 standard. Bus LVDS
has about twice the current capability of standard LVDS, and is optimized for driving
double-terminated cables or backplanes that present a large capacitive load. Some of
the advantages of using Bus LVDS technology for CogLink are the following:
•
It creates a highly reliable, high performance, full duplex communications conduit
for connecting vision systems and cameras.
•
It maximizes the usable cable length before a signal repeater is necessary.
•
It uses readily available twisted-pair cable and connector technology to minimize
costs.
Performance Factors
Two factors influence the performance of any communications system:
•
Inter-signal interference, or jitter
•
Signal attenuation
The high current capability of Bus LVDS allows CogLink to minimize the impact of signal
attenuation as a contributor to the bit error rate (BER) of the signal transmission. Bus
LVDS supports the encoding of 10 bits of parallel data plus two bits of clock data into a
serial stream. This stream is sent over a single twisted pair of wires, which minimizes the
impact of jitter on the overall BER.
