GigE Vision and GenICam standards have been in place for well over a year. Their introduction heralded the opportunity to seamlessly integrate vision systems into a network environment using industry-standard Ethernet components such as cable and switches. For example, traffic monitoring and control is a vision application area that can benefit from these standards.
Now that the standards have been in place for a reasonable amount of time, it has become apparent that not all Ethernet network systems are created equal, and careful consideration needs to be given to the quality of the components used in the network to ensure compatibility with vision. GigE Vision cameras transmit data in "jumbo" packets containing up to 9014 bytes, significantly larger than the standard 1500-byte packet. By using larger packets, the computer CPU is interrupted less frequently, thus improving performance.
By using network switches, the cable length for data transmission can, in theory, be unlimited. Unfortunately, switches limit the packet size and this limits efficiency. Worse, some switches simply cannot handle jumbo packets. They may work perfectly adequately for "normal" network activities using standard packets but not for vision.
Connecting one or multiple GigE vision cameras into such a system can result in the camera not receiving the correct return signals and therefore not appearing to work properly. In reality, it is the network components causing the problem.
In addition, cable may also not be what it seems. It is possible that cable labeled "Cat 6" (recommended for industrial applications) cannot support data transmission up to 1 Gbit/s.
Addressing the problem
Given these potential difficulties, there are two approaches to solving the problem. For existing networks, the network itself should be tested to ensure that it can support GigE Vision, and for new networks, only components that have been tested and proven to be compatible with GigE Vision should be used.
In view of the importance of GigE Vision for vision applications, the Stemmer Imaging Group (Puchheim, Germany; www.stemmer-imaging-group.com) has introduced a GigE Vision evaluation service. Using industry-standard Ethernet test equipment, an entire network or sections of a network can be evaluated for suitability for vision applications. This includes evaluating transmission capabilities for both copper and fiber cable, as well as identifying any breaks in the cable.
Switch capability can also be tested. In addition to testing networks in the field, all products in the product portfolio are evaluated to ensure that Cat 6 cable really does conform to Cat 6 specification and other network components are truly vision-compliant.
GigE Vision has already made a significant impact in the world of vision. Working with partners who fully understand the associated technology, especially with 10GigE on the horizon, should guarantee the original objective of GigE Vision: seamless integration into network systems.
GigE Vision in traffic applications
GigE Vision is of significant interest to the traffic market because it is based on standard network technologies and can support long cable lengths along with high data rates. Until now a traffic camera system needed to have its intelligence within a short-distance high-speed link of the camera, which meant either industrial computers were mounted on the roadside or bespoke custom cameras were used for specific applications.
With GigE Vision that intelligence can be distanced, providing more system flexibility and enabling standard technologies to be utilized.
