Less is more
Matrox technology allows dramatic cost reduction for complex inspection systems
When increasingly stringent quality requirements are paired-up with rapid-fire inspection speeds, the PC's bus traffic can end up in gridlock. In this article, Basler AG's Websight System serves as a case study to demonstrate how off-the-shelf components can offer superior system performance and reduced costs - two vital factors for any inspection system.
Scratching the surface
Basler AG (Ahrensburg, Germany) is one of the leading manufacturers of industrial image processing systems. Since 2001, the company has been developing inspection systems for continuous-strip materials under the Websight name. Websight systems are sold throughout the world with an export share of over 70%. Basler's target customers are manufacturers of special technical foils, such as polarization films for TFT LCD monitors. These customers must inspect 100% of the foils' surfaces and maintain strict quality standards.
This high-pressure market often dictates a 24/7 production schedule; therefore a high-performance continuous inspection system is essential. The solution for this application must be highly reliable, since any failure in the inspection system would lead to an immediate stop in production. Furthermore, from the customer's point of view, a space-saving installation is important, since most systems are located in clean rooms.
The Basler Websight system must inspect the foils with a resolution of 50 µm, at a rate of 30 m/min. The foils can be as wide as to 160 cm across. Based on this specification, the first generation of Websight systems was equipped with 9 line-scan cameras, each with 4096 pixels and generating a data rate of 41 MHz (fig. 1).
The Basler AG Websight system
Websight occupies a multifaceted key position as an essential component of the end customer's production line. In addition to actual fault recognition, Basler's Websight development team places a high priority on documentation and reporting: comprehensive analysis and reporting features provide the customer not only with 100% documentation meeting their quality, but also with data required for determining measures for quality improvements.
Plan A
Basler AG initially met these requirements with the following system structure. Each line-scan camera has its own frame grabber (PCI), and each frame grabber its own PC, given the bandwidth of the PCI bus. The original system proposed consisted of:
- 9 line sensor cameras with 4096 pixels each
- 9 PCI bus frame grabbers
- 9 PCs in a network
- special lamps, developed by Basler, to provide an even, high illumination level with low temperatures
This provided a stable solution, but it was very costly. Soon after deplyoment, it became clear that the system operated quite close to its performance limits. The network consumed most of the processing power that was really needed for analysis. Furthermore, the number of clients reduced the real-time capabilities of the system.
To the drawing board
A migration to Windows XP would alleviate the problem somewhat, but would inevitably lead to a reconstruction of the system design. The objective was a drastic reduction in the number of PCs and frame grabbers, yet allow for increased performance for future generations of the system.
The Basler development team wanted to keep Camera Link as the camera interface. With this in mind, they realized that new bus systems with enormously increased bandwidths were available, namely PCI-X and PCIExpress (PCIe). On examining the market more closely, it was evident that PCIe x4 slots provide sufficient bandwidth to grab two cameras with data rates above 40 MHz, but the market currently offers PCIe motherboards with just one x4 slot. Theoretically, implementing PCIe would reduce the number of PCs by half (2 cameras per gabber, one grabber per PC). On the other hand, PCI-X already provides the required data rate per slot (up to 1 Gbyte/s with a PCI-X/133MHz slot) and allows a number of grabbers to be used in a single system. The disadvantages of a PCI-X solution are the limited availability of PCI-X computers, and their higher price. The ideal solution would be imaging hardware that allows a migration to PCIe as soon as appropriate motherboards become available.
The Solution
Against this backdrop, the Basler development team determined that the Matrox Solios XCL, a Matrox Imaging Camera Link frame grabber, was the ideal choice for imaging hardware. The Matrox Solios is a family of high-performance frame grabbers that support both PCI-X and PCIe (Matrox Solios eCL), and feature a programmable FPGA, an increasingly common feature on frame grabbers. With the FPGA programmed to perform pre-processing on the incoming image data, system resources would be more readily available for intensive processing.
Basler found that with the Matrox Solios XCL (for PCI-X) the Websight system could control six cameras attached to three frame grabbers in a single PC, a savings of seven PCs and four frame grabbers per system!
Currently, three systems have been delivered, saving Basler the cost of 21 PCs and 15 frame grabbers. Further savings also result from the significantly simpler system structure and, consequently, greater ease of installation and commissioning, delivery logistics and spare parts stocking. With the new technology the system can be re-configured to meet more demanding requirements when necessary, opening up new markets for Websight, a declared objective for any business.
Block diagram of the Solios XCL board from Matrox Imaging
Foresight for the future
By choosing the Matrox Solios frame grabber, Basler will be able to easily incorporate new line-scan cameras with 6 kpixel and 8 kpixel resolution.
Future requirements will call for about twice the resolution, down to 25 µm, which could double the speed and create the need for even more cameras with significantly higher data rates. By developing highly flexible systems, Basler can easily adapt the system to the widest range of customer requirements, both now and in the future. This includes incorporating additional cameras, and adapting to different machines from the various manufacturers of systems and machines for plastics processing.
Choosing hardware and software components for image processing in a system is never easy and must be carefully considered. In addition to the factual considerations set out above, and comparisons of specifications, many other important criteria are generally brought together under the heading of 'service'. This includes technical support with problems, reliability of delivery and long-term product availability, and the willingness and capability of the supplier to accommodate special requirements. The team at Basler felt that Matrox satisfied these criteria.
Summarising, it can be concluded that the new bus systems offer great advantages for image processing. As always, however, the individual components must be carefully adapted to one another. With the Matrox Solios frame grabber, Basler AG has succeeded in maximising performance and stability while drastically reducing system costs. At the same time, a platform has been created that is also capable of meeting new requirements. There is the potential to make further savings, by migrating to PCIe, for example.
Finally, customer benefits are of the greatest importance to a company like Basler AG. Here, too, there are great advantages. The simpler structure and speedier installation and commissioning are all, in addition to the saving in space that is always sought in clean rooms, significant advantages for the end customer.
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