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GigE Vision - Emerging Standard for Machine Vision Cameras

What is Gig-E?
GigE, or Gigabit Ethernet, is the newest generation of Ethernet . Every one is familiar with Ethernet since it is the ubiquitous means of connecting a computer to a network. Standard Ethernet has a maximum data rate of 10 megabits per second (Mbps) and Fast Ethernet has a maximum data rate of 100 Mbps, but Gigabit Ethernet is even faster at 1000 Mbps. Standard Ethernet and Fast Ethernet are too slow for streaming uncompressed image data, and way too slow for machine vision cameras. Gigabit Ethernet (GigE), however, with its maximum data rate of 1000 Mbps, or 1 gigabit per second (Gbps). is capable of handling streaming image data and of providing reliable transmission of image data from high performance machine vision cameras.
  

GigE Camera Index

What's the difference between Gig-E and 'GigE Vision'?
'GigE Vision' is a new interface standard, soon to be published by the AIA, for high-performance machine vision cameras. GigE (Gigabit Ethernet), on the other hand, is simply the network structure on which GiGE Vision is built. The GigE Vision standard includes both a hardware interface standard (Gigabit Ethernet), communications protocols, and standardized means of communicating with, and controlling, a camera. The GigE Vision camera control registers are based on a command structure called GenICam which is administered through the European Machine Vision Association (EMVA). GenICam seeks to establish a common camera control interface so that third party software can communicate with cameras from various manufacturers without customization. GenICam is incorporated as part of the GigE Vision standard. GigE Vision is analogous to Firewire's DCAM, or IIDC interface standard and has great value for reducing camera system integration costs and for improving ease of use.

 

What's so great about GigE?
GigE is quite exciting because it provides many features that have been unavailable in a single camera interface until now. The combined features of high data rates (required for uncompressed video or imaging applications), ubiquitous computer interface hardware, low cost cabling, and widespread popularity make Gigabit Ethernet an attractive interface option for machine vision cameras. With the advent of GigE Vision, a standardized camera communication protocol from the Advanced Imaging Association (AIA), GigE becomes more attractive still. Here are a few of the compelling benefits of GigE Vision-compliant cameras:
  • Gigabit Ethernet ports are becoming common on PCs and laptop computers, so there is no need for special interface cards or expensive/complicated frame grabbers in order to operate a GigE Vision camera.

  • GigE provides high enough bandwidth to transmit uncompressed image data from the camera to the host computer in real time at speeds that exceed the requirements of most industrial machine vision applications. This substantially negates the need for complex and expensive interfaces like Cameralink.

  • Gigabit Ethernet provides high performance camera interface to convey control and image data over long cable lengths (up to 100 meters long) using inexpensive CAT5e or CAT6 cabling. Such long cable lengths are not generally possible with Cameralink, firewire, or USB.

  • GigE Vision is compatible with standard Gigabit Ethernet hardware allowing networking of cameras. This is especially useful in situations requiring multiple views and opens up new machine vision applications in Intelligent Traffic Systems (ITS) and public security imaging.

  • GigE Vision cameras such as those from Prosilica Inc. are capable of multicasting the image data simultaneously to multiple computers for distributing the image processing load across separate computers.

  • CAT5e or CAT6 Ethernet cables can be easily manufactured on-site using low cost cabling and tools. This feature is especially useful for outdoor installations where cameras may be mounted on poles or buildings and where the cable must be routed as the site demands.

  • The new GigE Vision standard provides ease of use that even surpasses that of IIDC-compliant firewire cameras (IEEE-1394).

  • 10GigE will soon offer 10 gigabits per second (Gbps) camera data rates meaning that parallel interfaces like Camera Link will no longer be needed even for high-speed applications.

When should I use IEEE-1394 (Firewire) instead of GigE
(or vice-versa)?
IEEE-1394 has been a standardized interface for machine vision for several years now. There is a wide variety of third-party machine vision software packages and systems that support DCAM (IIDC 1.30) compliant firewire cameras. Since GigE Vision is new to the market, there will initially be a smaller choice of software that supports GigE Vision than there is for 1394. For many desktop applications, Firewire may be more suitable than GigE for a few reasons. For example, desktop users do not need the long cable length provided by GigE and may prefer to have power supplied to the camera from the host computer through the firewire cable (firewire cameras generally draw power from the host computer through the cable - not yet true of GigE cameras). Prosilica and Balser manufacture a wide range of IEEE-1394 cameras in addition to their line of GigE Vision cameras.

What about USB2?
USB2 is a widely used interface for consumer computer products and is especially suited to webcams. However, USB has no standardized camera interface that is comparable to DCAM or GigE Vision. USB also has a relatively low power rating so that it cannot generally support the electrical power requirements of high-speed CCD cameras. Also, the nature of USB creates a CPU burden that demands precious computer resources that might better be available for running machine vision software. There is no compelling reason to choose USB for any industrial application.

What is Camera Link?
Camera Link is a parallel interface standard that defines a hardware interface for high-speed cameras. The main benefit of Camera Link is that it is capable of very fast data throughput - much faster than most cameras can produce the data. However, Camera Link has no equivalent communication protocol to GigE Vision or DCAM (IIDC), and requires a frame grabber card in order to interface to a host computer. Add to this the expense of Camera Link cables, and a 10 meter cable-length limitation. Soon, 10-GigE will be available in GigE Vision cameras providing data rates currently only possible through Camera link. While Camera Link will still find a place among hyper-fast specialty cameras, Gigabit Ethernet and 10GigE will ultimately make Camera Link obsolete for general machine vision.

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