Application Briefs

Introduced in 2010, CoaXPress (CXP) has become a leading standard for high-end machine vision, as well as life sciences, security, and defense applications. The CXP standard enables sending high-speed asymmetric serial data over long distances using standard 75-ohm coaxial cable. It currently supports speeds up to 6.25 Gb/S per link. However, the use of multiple links allows scaling up of bandwidth to meet the needs of a specific application. In addition, CXP enables control of the camera and supply of 24V at up to 13W of power per cable — all over the same coaxial cable.

Figure 1. The Aon-CXP single-link CoaXPress frame grabber designed for use with low-cost, compact CXP single-link cameras.

One of the driving forces behind rapid adoption of the CXP standard within the machine vision ecosystem is that it allows for the repurposing of coaxial cable in existing analog systems, and provides a cost-effective migration to faster, higher resolution, digital processing. A user need only replace the analog camera and frame grabber to gain CXP transmission rates. Because of the numerous CXP-compliant cameras, cables, frame grabbers, converters, and repeaters currently on the market, machine makers and system integrators are also designing CoaXPress into new solutions. CXP's additional bandwidth gives virtually any vision application the firepower to handle faster production runs and perform finer inspections.

The current version of CXP is 1.1.1, which was adopted in late 2015. The next iteration, CXP 2.0, promises to be a significant upgrade. The final draft of CoaXPress 2.0 is anticipated to be ready towards the end of 2017, with the first certified products expected in 2018. Central to this updated standard is boosting speed to double the data rates — CoaXPress 2.0 will extend machine vision data transfer rates up to 12.5 Gb/S (CXP-12) per link.

Greater speed translates to enhanced flexibility in system design, and the reduction of total system costs. Camera Link (80-bit) can offer a data rate of 850 MB/s, but by comparison, a single CXP-12 link can offer 1500 MB/s. In addition, the real estate requirements on a motherboard are significantly lower for multiple camera solutions.

Figure 2. The Mikrotron EoSens CXP+ Series captures 80 frames per second at 25 megapixel resolution. (Photo courtesy of Mikroton).

Because of the globallly increasing adoption of 3D vision techniques, CXP 2.0 includes extensions for 3D imaging. This addition to the standard is especially timely given that the global 3D vision market is expected to be valued at $2.13 billion by 2022. Growth is attributed to the increasing applications of 3D machine vision in the automotive and electronics industries as well as the broadening of applications that can employ machine vision solutions.

While the jury is still out on what else will be coming in CXP2.0, it is important to note that a variety of new features are being considered. The advantage of being one of the newest standards in machine vision is that we can learn from other standards about what works and what needs improvement.

As price pressures increase due to global competitiveness, productivity remains the key focus for successful manufacturers, with 100% quality assurance being the Holy Grail. Machine vision, with its ability to pinpoint the most minute defect, has long been considered a means for improving quality and therefore, productivity. CXP has improved the machine vision capability for larger manufacturers across a spectrum of industries in high-end inspection applications. The new generation of CXP frame grabbers and single-link cameras is reducing bandwidth requirements and enabling the technology to even be used by smaller manufacturers, who are more cost-constrained.

Figure 3. Adimec TMX CoaXPress cameras (photo courtesy of Adimec)

At the same time as CXP components are improving in performance, their size and cost are decreasing. CXP single-link cameras, new to the market, are replacing traditional, power hungry, large, and expensive CL cameras. Some CXP cameras can have footprints as small as of 29 x 29 mm. These cameras can achieve the current maximum data rates of 6.25 Gb/s despite their size. At this speed, the system can deliver 2MP images at 300 FPS, almost twice the real-world data rate of USB3 Vision cameras, and six times faster than GigE Vision solutions.

Low cost single-link CoaXPress frame grabbers have been launched to take advantage of these new cameras’ performance, while still providing all the convenience of a GigE Vision or USB3 Vision camera system. A single-link CXP camera and frame grabber can compete on price while removing USB3 Vision's restriction on cable length. In addition, this combination can provide a host of machine vision features missing from GigE Vision or USB3 Vision camera systems, for example, triggers, encoders, strobe, waveform generators, and quadrature encoder support.

Rather than having to deal with NIC and USB interface troubleshooting, a CXP frame grabber company can write every line of software and firmware designed for their own hardware. In the event of a problem, the company can support their customer to resolve the issue.

Conclusion

CXP is one of the youngest standards in machine vision but has proven itself as a worthy successor to the existing architectures. The CXP interface can evolve to meet the growing demands for larger and faster sensors. For the lower end market, it offers a solution improving upon both USB3 Vision and GigE Vision data rates and real time compatibility. It is anticipated that in time it will come to be accepted as a popular and widely used machine vision standard.

This article was written by Donal Waide, Director of Sales, BitFlow Corp., Boston, MA. For more information, contact Mr. Waide at This email address is being protected from spambots. You need JavaScript enabled to view it., or visit here.

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