Gig E Vision The main features of GigE Vision have been covered previously, but as a quick recap some of the points of note are:
Long cable lengths – upto 90m between links with the capability to use fibre - optics to go much further between links , all this with standard consumer components.
Network topologies – one camera to one PC , many came ras to one PC and one camera to many PCs – ethernet - based transmissio ns has opened possiblities that were not feasible with framegrabber - based systems and gone much further than was possible with USB and Firewire - based systems.
Self- describing cameras – Genicam means that a device must describe itself to a connecting PC by means of an xml file. This replaces the need for conf iguration or camera files, for example for describing the format that data streams fr o m a camera. Power over Ethernet PoE (Power over Ethernet) is a standard consumer technology that allows upto 15.4W of DC power without sacrificing the cable - length capabilities of GigE . PoE - enabled G igE camera include IDS uEye CP cameras and optionally Stemmer Imaging ’ s CVC GE cameras and the AVT Mant a and GT ranges . The advantage is that with a PoE - enabled NIC it is only ne cessary to run a single cable to the camera.
Since the advent of Gigabit ethernet cameras, the general advice is to use Intel Pro cards as these offer the most performance options. However, Intel - branded cards do not have PoE capabilities , but Intel chipsets are available in third - p arty cards whic h do impleme ent PoE, such as ADLINK ’ s GIE62+ and GIE 64+ cards (two and four channel, re s pe c tively) .
Processing Images from GigE S ources The possibilities offered by GigE for large numbers of cameras per PC c an quickly make processing power the bottleneck . For colour (Bayer) cameras that are close to th e GigE bandwidth limit , su ch as DALSA ’ s high - speed Genie HC range , even Bayer processing can lead to significant processing overheads. In light of this Silicon Software has a range of GigE Vision framegrabbers to reduce the burden. At the lower end of the scale are the A - series boards, these are delivered with va rious on - board capabilites such as Bayer conversion, look - up tables to improve contrast, white balancing, digital I/ O and filtering – all with minimal CP U interaction. These boards have 4 chan nels and are available with PoE and can transfer upto 760MB/s (remember that Bayer conversion multiplies the amount of data from a camera ) .
For higher proce ssing requirements, Silicon Software has it ’ s V - series boards. These have a user - programmable FPGA (su p porting Silicon Software ’ s Smart Applets and Visual Applets programming interfaces) as well as twice as much on - board memory as the A - series boards . These are designed to massively offload the CPU from vision proc essing tasks, for example the creation of 3D data from laser sheet - of - light syste ms or processing that must be c arried out in a deterministic time such as particularly high - speed or high - throughput systems. If the standard board ’ s FPGA is not sufficient it isi also possible to add modules to extend the hardware resources of the board. Once again digital I/O is built into the board, allowing it to work directly with the FPGA design if requ ired.
At the time of writing, th e r elease of G igE Vision 2.0 is imminent. This brings further feature - support to GigE Vision, including
Firewall traversal , where a small amount of data is returned to the camera to show that the connection to the camera is a two - way connection, rather than a malicious attack.
IEEE 1588 Precision Time Protocol , where each device uses a synchronise d clock (synchronised in terms of both time and frequency).
Compressed image streaming su pport, including J PEG, JPEG2000 and H264 for mats.
Multi- zone images, for example for CMOS sensors t h a t can output data from multiple ROIs.