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Combining Machine Vision and Temperature Measurement
IR cameras that make for practical use in
machine vision applications are Gigabit
Ethernet (GigE) connectivity, GigE Vision™
compliance, a GenICam™ interface, and
a wide range of third party software
that supports these cameras. There are
other hardware features that are also
important.
Generally, ultra-high detector resolutions
are not needed in the targeted
applications, so a typical focal plane
array (FPA) would be 320x240 pixels.
Nevertheless, outputting a 16-bit image
stream of these 76,800 pixels at a 60Hz
frame rate amounts to about 74Mb/
sec. While this is much slower than a
1000baseT Ethernet system is capable of,
multiple cameras may be connected and
there may be a lot of other trac on the
network between image transmissions.
To speed up image transfers, data
analysis and decision-making must take
place outside the camera and is one of
the reasons why there is a good market
for third-party thermographic software.
The other reason is that most machine
vision systems are custom designed
for specic production processes. Of
course, IR camera manufacturers supply
various types of software to support their
products and facilitate application in
these systems.
The goal of the GigE Vision technical
standard is to provide a version of GigE
that meets the requirements of the
machine vision industry. One of the
industry objectives is the ability to mix
and match components from various
manufacturers that meet the standard.
Another is relatively inexpensive
accessories, such as cabling, switches,
and network interface cards (NICs) as well
as the ability to use relatively long cable
runs where required.
The GigE Vision standard, which is based
on UDP/IP, has four main elements:
A mechanism that allows the •
application to detect and enumerate
devices and denes how the devices
obtain a valid IP address.
GigE Vision Control Protocol (GVCP) •
that allows the conguration of
detected devices and guarantees
transmission reliability.
GigE Vision Streaming Protocol (GVSP) •
that allows applications to receive
information from devices.
Bootstrap registers that describe the •
device itself (current IP address, serial
number, manufacturer, etc.).
With GigE capabilities and appropriate
software, an IR machine vision system
does not require a separate frame
grabber, which was typically the case
with visible light cameras in the past.
In eect, the GigE port on the PC is the
frame grabber. Older visible light cameras
that have only analog video outputs
(NTSC and PAL) are limited to much
lower frame rates and video monitor
observations. By using GigE, an IR vision
system not only has higher frame rates,
but can be monitored remotely over
much greater distances compared to
local processing and transmitting data
over USB, Firewire, CameraLink, etc.
In addition, Ethernet components are
inexpensive compared to frame-grabber
cards and related hardware.
A GigE Vision camera typically uses
an NIC, and multiple cameras can be
connected on the network. However, the
drivers supplied by NIC manufacturers
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