Basler L301kc - BFi OPTiLAS

8
IEEE 1394 or Camera Link –
Which One Do I Want?
If you've been to a machine vision trade show lately
or if you've looked through any industry related
publication, you know that two new interfaces for
industrial digital cameras were recently introduced.
The new interfaces, Camera Link TM and IEEE 1394
(also known as FireWire ® ) appeared amid much
fanfare and with long lists of supposed advantages
to camera users. But even if you have extensive
experience with digital cameras, the competing claims
and highly technical explanations for each interface
may easily have left you confused about whether
either interface is worth considering in your current
or your future applications.
In this article, we will clear up some of the confusion
by looking at a real world decision-making process
that revolved around the Camera Link and the IEEE
1394 interfaces. Stan Shmia, an applications engineer
for Basler Vision Technologies, recently worked with
International Cybernetics and helped them work
through their questions about the two interfaces
and to decide what was appropriate for their
application. Stan's experience with Cybernetics
provides some insights that you might find useful.
Before we go further, you may want to look over
Table 1. It outlines some of the basic characteristics
of the IEEE 1394 and Camera Link interfaces. If you
would like to become even more familiar with the
technical details of the Camera Link or IEEE 1394
interfaces, a key word web search will yield a wealth
of information.
The Cybernetics application
International Cybernetics
develops and manufactures
a variety of equipment
used to examine and
profile highways. Currently,
they are working on a new
piece of equipment that
will employ two truck
mounted camera systems
to examine the condition
of highway striping and
overhead signs (see Fig. 1).
As the truck moves along
a highway, camera system
one uses a high speed line
scan camera to capture
images of the highway striping. Camera system two
uses two medium resolution area scan cameras to
capture images of overhead signs. Proprietary
software is used to evaluate the condition of the
striping and the signs and a positioning system is
used to track the location of the truck on the
highway. Condition and location information are
logged in a database (see Fig. 2). Potential customers
for this equipment include state and local highway
departments who will use the information from the
database to schedule highway maintenance.
For camera system one, an extremely high speed
line scan camera is required. Stan noted that trying
to meet this requirement reveals some of the
limitations of the IEEE 1394 interface and highlights
some of Camera Link's strengths. Currently, the
specifications that govern IEEE 1394 cameras do not
define a line scan camera, so no IEEE 1394 line scan
cameras are available. Also, the IEEE 1394 bus has
a relatively low data rate; it can handle approximately
32 MBytes of image data per second. On the other
hand, Camera Link line scan cameras are readily
available. And with a potential image data rate of up
to approximately 650 MBytes per second, Camera
Link can easily handle the fastest line scan cameras
currently available.
Another interesting consideration is that the standard
electrical interface on Camera Link cameras and
frame grabbers would allow the Cybernetics
engineers to test cameras from several different
manufacturers with a minimum of effort. In the past,
each manufacturer used different connectors, different
cables, and different pin layouts on their products.
This resulted in major headaches for engineers who
wanted to test products from different manufacturers
head to head. The standard connectors and cabling
associated with Camera Link make it much easier
to try different cameras during a development effort.
Keep in mind, however, that you will still need to
obtain a different frame grabber configuration file
for each different camera that you test.
For camera system one, Stan pointed to the Camera
Link cables as a major advantage over the cables used
with older products. Camera Link cables are thinner,
are much more flexible, and are more robust. In the
Cybernetics application where harsh conditions,
vibration, and cable routings with tight curves are all
present, the Camera Link cables are an obvious plus.