The latest improvements in GigE Vision

The next generation: GigE Vision v 1.2

Four years after its introduction, GigE Vision has not only achieved widespread acceptance as a standard interface, it has also increased the range of vision applications that digital cameras and other peripherals can serve, taking the standard on its way to becoming the major industry interface for cameras operating to 120 Mb/second.

Limitations to previous standards lead to GigE Vision development
The variations in output signals from early digital cameras made it difficult for developers to utilize a camera from one vendor with a frame grabber from another with the consequent slow acceptance of digital vision systems.

The Camera Link interface standard was created to solve the problem and this standard provided a high-bandwidth low voltage differential signal (LVDS) for connecting a digital camera to a vision system using a 26-wire connection between the camera and frame grabbed and handling 255 Mb per second. The downsides of using the 26-wire cable, however, is that this cable is both bulky and costly and the differential signal scheme also suffering from a best-case range limit of 10 meters. All of these factors placed significant restrictions on system installations.

Another limitation of the Camera Link interface, while providing a standardized physical interface and image data, was that it does not specify the protocol for sending control information to the camera. In order to overcome this, and other ambiguities, vendors developed differing formats for control signalling which added more complications when the need was to mix-and-match cameras and frame grabbers when designing systems.

The GigE Vision solution
GigE Vision addressed these limitations by adopting Gigabit Ethernet as the camera interconnect resulting providing enough bandwidth for data rates of about 120Mb second (enough for all but the highest-speed cameras) while requiring only a simple, Cat 6 unshielded twisted pair cable to carry the signals. Cable length is one of the strongest benefits of GigE Vision and cable can be up to 100 meters long with multiple cables being able to be grouped in a link aggregation configuration to increase the bandwidth. Furthermore, widespread industry use of Gigabit Ethernet in industry have resulted in economies of scale making interface electronics and driver software both inexpensive and widely available.

The advantages of GigE Vision
All personal computers have Ethernet interfaces built-in, allowing developers to create a completed machine vision system using only a camera and a standard PC. The use of networks can extend the connection between the camera and the vision system to virtually any distance, permitting multiple cameras to connect to the system simultaneously.

The interface also provides flexibility in the type of information it can carry. Camera Link was designed to provide image data at a high rate, and little else. Its relatively fixed data format made it difficult for the camera to send anything other than some type of image to the vision system. GigE Vision, however, provides data in software-defined packets that can contain virtually any type of information. This makes it easier for vendors to develop and customers to use cameras that offer built-in processing and provide the vision system with more than just an image. The GigE Vision interface is software-centric and offers an easy way for camera manufacturers to provide additional on-board processing that can be easily configured through the GenICam XML file a capacity that can be exploited by smart cameras.

Additionally, with the introduction of GigE Vision 1.2, it is now possible to use GigE Vision to control machine vision devices other than a camera. GigE Vision is the first machine vision camera interface to expand its capacity to configure and control peripherals that are not used for image acquisition. For instance, it is possible to use GigE Vision to configure an Ethernet-based strobe light or an LCD display using the same software API that is used to control and stream from a GigE Vision camera. This greatly simplifies software development as any GigE Vision device, not only cameras, can be controlled using the same software library. Coupled with the enormous number of Ethernet devices, this makes GigE Vision the interface of choice to support the various devices available in the machine vision world.

GigE Vision and the camera marketplace
S since the specification was released in May 2006, a large number of developers have embraced the interface in their designs. The interface has also created new opportunities for the application of digital cameras where, for example, the longer cable has allowed digital to replace analog in applications such as security and traffic surveillance. The flexible data structure has also allowed creation of intelligent cameras, such as an inspection system camera that automatically makes key measurements and sends the results but can also send an image to an operator if a part fails to meet specifications.

The future of GigE Vision
In the forthcoming Revision 2.0, GigE Vision will provide significant enhancements to transfer speed by formally introducing support for 10 gigabit Ethernet and link aggregation (IEEE 802.1AX). The latter provides a standardized scheme to support multiple cable connections to linearly increase the data transfer speed. This version will also focus on improving multiple camera capabilities by building on the IEEE precise time protocol (IEEE 1588) to synchronize accurately cameras down to a few microseconds. GigE Vision 2.0 will also provide a standard scheme to transfer compressed images and video streams based on the JPEG, JPEG2000 and H.264 compression standards.

Because GigE Vision is based on Ethernet, vendors also have the option to leverage innovations in the networking standard. One possibility is adaptation of the Power over Ethernet (PoE) standard, which eliminates a connection to the camera by allowing the GigE Vision cable to carry power directly, as well as data and there are currently several such PoE GigE Vision cameras available on the market.
Vendors can also employ 10 gigabit Ethernet for increased data bandwidth. To date, there is little network equipment available that can handle 10G Ethernet over copper, and what is available is power-hungry, limiting the option’s attractiveness.

Adept Electronic Solutions are "The Machine Vision and Imaging Specialists" and distributor of Machine Vision products in Australia and New Zealand. To find out more about any machine vision product please email us at: info@adeptturnkey.com.au or call us at Perth (08) 92425411 / Sydney (02) 99792599 / Melbourne (03) 95555621 or use our online contact us page.