Machine vision: high-speed, long-distance communications

CoaXPress (CXP) is a high-speed point-to-point serial communication standard for the transmission of video data, scalable over single or multiple coaxial cables. It has a high-speed downlink of up to 6.25Gb/S per cable for video, images, and data, plus a lower speed, 20Mb/S uplink for communications and control.

06/04/2012


BitFlow, a manufacturer of high-speed frame grabbers since 1993, recently introduced its latest CoaXPress frame grabber, the Karbon-CXP4.Broken down to its simplest terms, machine vision is the ability to use a camera, computer, and an illumination source to make a decision. Each component—camera, computer, and illuminator—has witnessed rapid changes over the past decade, transforming the imaging landscape and making machine vision more powerful, scalable, and affordable.

While we are all well aware of the seemingly daily developments in PC architecture and the migration from analog to digital cameras, there is a less frequently mentioned component to machine vision: the interface technologies between the camera and the computer. 

Cameras need to transmit data to the computer so that it arrives intact in a relatively short time frame. When analog cameras were in fashion, and some of them still are, this interface was a BNC coaxial connection between the camera and a data acquisition board known as a frame grabber. The frame grabber was usually a PCI interface that fit into the motherboard that allowed data to transfer seamlessly between camera and computer memory.

Just as cameras, computers, and illumination technology have developed, so has the frame grabber—now most common in a PCIe slot on the motherboard. Modern frame grabbers are capable of carrying interfaces such as LVDS, RS422, and Camera Link. Frame grabbers are also being developed to handle the newest of machine vision interfaces, CoaXPress.

The CoaXPress interface was recently adopted by the combined agencies of the Automates Imaging Association (AIA), European Machine Vision Association (EMVA), and the Japanese Industrial Imaging Association (JIIA), collectively known as G3. Merging the simplicity of coaxial cable with serial data technology, CoaXPress permits high-speed image data to be transferred over long distances in area-scan and linescan applications, even when captured by the largest, fastest, and most bandwidth-hungry of today’s CMOS sensors. This kind of application goes far beyond the capabilities of established interfaces.

CoaXPress details

CoaXPress (CXP) is a high-speed point-to-point serial communication standard for the transmission of video data, scalable over single or multiple coaxial cables. It has a high-speed downlink of up to 6.25Gb/S per cable for video, images, and data, plus a lower speed, 20Mb/S uplink for communications and control. Power is also available over the cable ("Power-over-Coax") and cable lengths of greater than 130 m may be achieved, much farther than twisted pair.

Industry analysts widely expect CoaXPress will be the fastest growing interface in machine vision over the next 3-4 years. This owes to a range of advantages including: low cost of standard 75 Ohm coaxial cables, ultrafast data transmission rates, and achievable longer distances. For even higher data rates, multiple CXP channels can be used. CoaXPress can be expanded to four ports, resulting in 25Gb/s of data throughput. Despite the long distances, CoaXPress permits trigger events to be sent from host to camera and vice versa with minimal latency and jitter.

Because it uses standard coaxial cable yet delivers impressive bandwidth, CoaXPress is drawing interest not only from the machine vision community but also from integrators in the medical, military, and security fields where legacy coaxial cable is often deployed. By “repurposing” already installed coaxial cables, CoaXPress eases the migration from analog to digital video.

To better appreciate these advantages let's look at an application example: license plate readers. In Europe, the standard license plate is large enough that it is easy to read, 18- to 20-in.-long plates, 4-in. tall, and large bold, unhindered fonts. The U.S. license plate is 12-in. x 6-in., and apart from up to seven alphanumeric characters, there is also a state name and sometimes an image on the plate. This leads to a lot of confusion at low resolutions, for example deciphering whether the plate of a car that drove through a toll booth without paying was ABC123 or A8CIZ3. The processing center would have to verify the car make and interaction with the registry, which in turn dramatically reduces efficiency. If the resolution and data delivery were sufficiently quick, it would be a simple read. However, while a higher resolution camera would offer the solution, an interface is needed to bring the data back to the processing center extremely quickly—a distance typically further than twisted pair cable can handle even with repeaters.

The CoaXPress interface will be of major benefit here. Several analog traffic cameras are on U.S. highways. This data is coming back at 11Mb/S over a coax cable from the camera to the computers. Consider the volume of data coming back at even one CXP link (650Mb/S). This would enable images of traffic on routes to be crystal clear and also allow for better information dissemination about traffic backlogs, accidents, or breakdowns. These images would be clear enough to be seen on a smartphone app. And because CXP offers Power-over-Coax, there would be no need for additional cabling work.

Additional CXP applications

CoaXPress will play a vital role in many aspects of machine vision in the coming years. As designers sit down with this new interface at their disposal, more ideas will be formed and CoaXPress will enable machine vision to perform more efficiently.

- Donal Waide is director of sales for BitFlow, Woburn, Mass. Edited by Mark T. Hoske, content manager CFE Media, Control Engineering, Plant Engineering, and Consulting-Specifying Engineer, mhoske@cfemedia.com.http://%0Dwww.bitflow.com

www.bitflow.com

www.coaxpress.com



No comments
The Top Plant program honors outstanding manufacturing facilities in North America. View the 2015 Top Plant.
The Product of the Year program recognizes products newly released in the manufacturing industries.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
2016 Product of the Year; Diagnose bearing failures; Asset performance management; Testing dust collector performance measures
Safety for 18 years, warehouse maintenance tips, Ethernet and the IIoT, GAMS 2016 recap
2016 Engineering Leaders Under 40; Future vision: Where is manufacturing headed?; Electrical distribution, redefined
SCADA at the junction, Managing risk through maintenance, Moving at the speed of data
Safety at every angle, Big Data's impact on operations, bridging the skills gap
The digital oilfield: Utilizing Big Data can yield big savings; Virtualization a real solution; Tracking SIS performance
Applying network redundancy; Overcoming loop tuning challenges; PID control and networks
Driving motor efficiency; Preventing arc flash in mission critical facilities; Integrating alternative power and existing electrical systems
Package boilers; Natural gas infrared heating; Thermal treasure; Standby generation; Natural gas supports green efforts

Annual Salary Survey

Before the calendar turned, 2016 already had the makings of a pivotal year for manufacturing, and for the world.

There were the big events for the year, including the United States as Partner Country at Hannover Messe in April and the 2016 International Manufacturing Technology Show in Chicago in September. There's also the matter of the U.S. presidential elections in November, which promise to shape policy in manufacturing for years to come.

But the year started with global economic turmoil, as a slowdown in Chinese manufacturing triggered a worldwide stock hiccup that sent values plummeting. The continued plunge in world oil prices has resulted in a slowdown in exploration and, by extension, the manufacture of exploration equipment.

Read more: 2015 Salary Survey

Maintenance and reliability tips and best practices from the maintenance and reliability coaches at Allied Reliability Group.
The One Voice for Manufacturing blog reports on federal public policy issues impacting the manufacturing sector. One Voice is a joint effort by the National Tooling and Machining...
The Society for Maintenance and Reliability Professionals an organization devoted...
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
Maintenance is not optional in manufacturing. It’s a profit center, driving productivity and uptime while reducing overall repair costs.
The Lachance on CMMS blog is about current maintenance topics. Blogger Paul Lachance is president and chief technology officer for Smartware Group.
This article collection contains several articles on the vital role of plant safety and offers advice on best practices.
This article collection contains several articles on the Industrial Internet of Things (IIoT) and how it is transforming manufacturing.
This article collection contains several articles on strategic maintenance and understanding all the parts of your plant.
click me