How do you think the new GigE standards will influence the machine vision industry?
Respond or ask your question now!
By Burke Henehan
1394 Trade Association
We have all seen them on the TV news, a crime committed on camera, but the analog camera resolution is so poor the police can’t identify the perpetrator and are hoping some member of the public can help. Analog cameras have their place, at least as intimidation, so the signs saying “Premises under Video Surveillance” are not inaccurate.
But as for audio and TV, digital is the path to better performance and more capability in security imaging. The analog to digital (A/D) conversion is done inside the camera close to the CCD/CMOS imaging sensor, retaining the most quality and least noise. The image then is transmitted digitally making it highly tolerant of noisy environments. Since the A/D conversion is done in the camera it does not suffer the distortion that tens of meters of cable or the electrically noisy computer can inject to distort the analog image. This all increases the capabilities of the security system.
So what are the improvements when a digital surveillance system is used? It depends on the transport system and protocols. Internet Protocol (IP) video-based cameras can interface directly into an existing network, but can easily saturate the available bandwidth if used at higher resolution than analog cameras. If the update rate is lowered to reduce the bandwidth requirements the video updates so slowly that important details easily can be missed. But a historically short-range technology, FireWire, is being used in a new way to solve many of these problems and reduce costs at the same time. Originally used for video peripherals, external mass storage and the like for PCs and Macs, the Institute of Electrical and Electronics Engineers standard number 1394-2008 (Apple’s FireWire) implementation now is being widely implemented in industrial applications. (Note: 1394-2008 is a one-document consolidation of 1394-1995, 1394a, 1394b and their errata.) The key enabling technology addition was transport across long haul cables, namely UTP5/6, coax, and fiber, up to 100m at up to 800Mbps. While this enhancement enabled large-scale security imaging, many of FireWire’s other features make it the eager choice of digital security systems. This is my Top 10 list:
1. IEEE 1394-2008 allows individual cable runs of up to 100m. This includes use of the nominal shielded twisted pair cables (STP), unshielded twisted pair cables (UTP), coaxial cables (co-ax), plastic optical fiber (POF), and glass optical fiber (GOF). STP has been the standard cable since the beginning of FireWire. It is very mechanically and electrically robust with excellent transmission characteristics and resistance to electromagnetic interference. UTP is the lowest cost and can be used out to 100m runs, and may already be in place to support a previous control path to an analog camera installation. But UTP also is more susceptible to electromagnetic interference in industrial or high EMI conditions (such as airport radar). Coax cables are a well-known and well-shielded medium and also may already be in place from a previous analog installation. The optical cables are the most immune from EMI/ESD issues. POF is cheaper, but has limitations on distance and data rate depending on the fiber optic transceivers selected. GOF is the premium medium; its speed allows the maximum FireWire throughput, longest range (2km), it is EMC/ESD/EMI immune, non-sparking, and non-corrosive. There is even work under way in the 1394 Trade Association to standardize an existing implementation that uses Gigabit Ethernet physical layer transceivers and cables to connect two 800 Mbps FireWire nodes.
2. FireWire is able to carry real-time video (1394 isochronous), control data (1394 asynchronous), and power over a single cable. Analog cameras can require a two- wire cable for power (hot and ground return), another cable for analog video data (coax), and another cable for digital control data (UTP). The fewer the cables the lower the material and installation costs and the shorter the schedule.