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Chapter 4
use the Windows or Linux IP stack, which
may lead to unpredictable behavior,
such as data transmission delays. By
using more ecient dedicated drivers
compatible with the GigE Vision
standard, the IP stack can be bypassed
and data streamed directly to memory at
the kernel level of the PC system. In other
words, Direct Memory Access (DMA)
transfers are negotiated, which also
eliminates most CPU intervention. Thus a
near-real-time IR vision system is created
in which almost all of the CPU time is
dedicated to processing images.
To make sure a camera is GigE Vision
compliant, look for the ocial stamp
(shown in Figure 3) that can only be
applied if the camera conforms to the
standard.
Figure 3. Ocial trademark for GigE compliant
products
GenICam compliance should also
be considered for an IR camera.
GenICam compliance makes it easier
for developers to integrate cameras
into their IR vision system. The goal of
the GenICam standard is to provide
a generic programming interface for
all kinds of cameras. No matter what
interface technology (GigE Vision,
Camera Link, 1394, etc.) is used, or what
camera features are being implemented,
the application programming interface
(API) should be the same. The GenICam
standard consists of multiple modules
and the main tasks each performs are:
GenApi: conguring the camera•
Standard Feature Names: •
recommended names and types for
common features
GenTL: transport layer interface, •
grabbing images
The GenApi and Standard Feature
Names modules are currently part of the
standard module only. GenTL should be
nished soon.
Common tasks associated with IR
cameras in machine vision systems
include conguration settings, command
and control, processing the image, and
appending temperature measurement
results to the image data stream. In
addition, the camera’s digital I/O can
be used to control other hardware, and
there are triggering and synchronization
functions associated with real-time data
acquisition. GigE Vision makes hardware
independence possible, while GenICam
creates software independence. For
example, in a system with IR cameras
compliant in both and connected to a
GigE network, virtually any application
program can command a camera to
send a 60Hz stream of images that can
be easily captured without dropping
frames and losing important data. This
information can be processed for alarm
functions, trend analysis and statistical
process control.
Third Party Software Expands
Applications
By adhering to the standards described
above, IR camera manufacturers are
making it easier for developers to
integrate their cameras into vision
systems with a broad array of functions