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.
the difference between Gig-E and 'GigE Vision'?
'GigE Vision' is a new interface standard, soon to be published by the
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.
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:
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.
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.
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.
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.
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.
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.
GigE Vision standard provides ease of use that even surpasses that of
IIDC-compliant firewire cameras (IEEE-1394).
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.
should I use IEEE-1394 (Firewire) instead of GigE
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
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.
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.