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INDUSTRIAL CAMERA SELECTION
See all INDUSTRIAL VIDEO CAMERAS
Following are several criteria that users or developers should consider when selecting the best camera for their industrial imaging application (from Quality Magazine March 2008):
Field of View (FOV) and Resolution Requirements
The field of view (FOV) and the detail size that need to
be resolved in the image will determine the sensor size
and amount of pixels required. A simple calculation of
the number of pixels necessary to resolve a defect of a
known size will provide minimum number of pixels per
mm which in turn multiplied by the longest dimension of
the FOV will provide the required resolution. The sensor
size depends on the FOV and the optics.
Image Quality
Against common perception, image quality goes far beyond
resolution. Vision users have to consider advantages of
CCD vs. CMOS based cameras and, especially in the case
of high-end quantitative applications, specifications such
as readout noise, dark noise, SNR and light sensitivity
should play an important role in the selection process.
Frame Rate
Frame rate in conjunction with resolution and the number
of bytes per pixel determine the amount of data that needs
to be transferred and processed. For example, a camera
with a 1280 x 1024 (SXGA) resolution at 30 frames per
second (fps) and 8bits (or 1 Byte) per pixel will require
a data bandwidth of approximately 50MBytes/sec. This
is below the PCI bus limit (~100MB/sec) and is within
the capabilities of 1394.b or Gigabit Ethernet interfaces.
Anything beyond 100MB/sec will require a frame grabberbased
system with Camera Link® interface and PC with PCI
Express® bus.
Interface Type
Beyond the frame rate and bandwidth requirements, data
transfer reliability is an important factor in choosing a
suitable camera interface type. Vision users that consider
deterministic data transfer as their first priority prefer
to use systems with analog or digital cameras connected
to capture boards with on-board memory buffers that
guarantee lossless image transfer. Among the non-frame
grabber interfaces, IEEE-1394 through the IIDC standard
offers excellent provisions for reliable isochronous image
transfer with minimal CPU usage.
Another important factor that comes into play when
choosing the interface is cost. Analog cameras on average
cost less than digital cameras and are built utilizing
a single, well-established interface. Typically, the more
cameras that are required to perform a single vision
task, a frame grabber-based solution becomes most cost
effective. On the other hand, with systems using digital
cameras, the advantages are features and performance:
high resolution options, high frame rate capability and
image quality. The cost of cabling cost is also becoming
an advantage with non-frame grabber digital interfaces.
Overall, the cost gap between these two technologies is
rapidly closing.
Support and Software Drivers
Vision users should always look for a vendor that provides
reliable drivers, a user friendly software developer
kit (SDK) and good technical support. The software
component of a vision system is increasingly becoming
the most important factor in determining the amount
of resources and time that will need to be invested.
Simplifying this effort is a clear trend in today’s machine
vision industry.
Form Factor and Reliability
Form factor is an obvious consideration. Regarding
product reliability, with so many choices available today,
vision users should seriously consider a manufacturer
with solid reputation. After all, cameras are the “eyes” of
their system and the last thing they need is to go “blind”
in the middle of a critical task!
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