Image Processing - August 1997

FPGA Technology Helps Protect the World
by Sheldon Liebman

Until recently, most image processing and machine vision systems used DSP-based image processing boards. These products provide the horsepower necessary to process large amounts of data in real-time. As a general-purpose processor, DSPs can be overkill for applications that only need a few specific image processing functions. However, with no other viable choices, they have continued to dominate the market.

Today, a new type of processor is available that finally offers an alternative to the DSP. Field Programmable Gate Arrays, or FPGAs, provide a programmable, high-speed solution that is both less expensive and more flexible than DSPs.

Since this is a relatively new technology, there are not many commercial products that have been developed using FPGAs. One of the first was introduced earlier this year by Univision Technologies, based in Burlington, MA. Their Falcon-XL is a combination SVGA display, image processor and frame grabber based on FPGAs from Xilinx in San Jose, CA.

Before introducing the Falcon-XL, Univision modified its existing Falcon-PCI product for a few key OEM customers. One of these customers is American Science and Engineering of Billerica, MA. By taking advantage of the way that FPGA technology can be customized to each application. AS&E has started improving their x-ray based vision systems.

AS&E, founded in 1958, is an industry leader in the use of x-ray technology for the detection of explosives and drugs. Their systems are used for the inspection of baggage, mail, cargo, people and vehicles. One key to AS&E’s success is their patented Z®Backscatter technology. This provides a separate profile that makes it easier to identify low-density materials such as drugs, explosives and plastics.

The company serves two principal markets - detection of contraband for Customs agencies and security for both high-risk government facilities and executive offices of Fortune 500 companies. The first product that AS&E adapted to use the Falcon and FPGA combination is their Model 66Z for MailSearch™ and LobbySearch™ applications.

The combination of the Falcon-PCI and FPGA technology improved the Model 66Z in a number of areas. First and foremost was the ability to implement custom algorithms designed specifically for this application.

AS&E submitted function definitions to Univision that were programmed into the Xilinx FPGA by Univision engineers. These functions included a new edge enhancement algorithm and zoom function. Other image enhancement features, such as pan, scroll and density expand, were already present in Univision’s Falcon Software Toolbox and were easily implemented into AS&E’s existing code.

The image enhancement filtering specified by AS&E uses a 7x7 convolution. This high-pass filter enhancement highlights areas of the image with high spatial frequency components, such as circuit boards, wire bundles, guns and knives and other inorganic materials. The density expand function of the system is used to identify organic materials such as plastic explosives and flammable liquids. With the new product, the ability to identify these materials is enhanced.

Another advantage to the new system is that it is much more compact. Prior to moving to FPGA technology, AS&E used seven boards in their Model 66Z. This included four boards controlling two framebuffers and (RS-170 video) displays, one edge enhancement board and two preamplifier boards. In the new system, a single Falcon board controls both (VGA) displays and contains a Xilinx FPGA for edge enhancement. A separate data acquisition board connects to the Falcon for a total of only two boards in the new system.

By reducing the number of boards from seven to two, AS&E realized across the board savings in time and money for their Model 66Z. The new systems, which were first installed a year ago, take less time to set up and test. The cabling is simplified and maintenance is easier. Power issues and bus traffic conflicts have been eliminated. The reduction in the number of boards allows a smaller passive backplane to be used as well as reducing inventory requirements.

The nature of FPGA technology has also created systems that can be upgraded in the field as algorithms are enhanced or refined. This has Jamie Tanch, a Senior Software Engineer at AS&E, very excited. "As we move forward," says Tanch, "we will be doing a lot more complicated filtering operations. It will be a great advantage not to redo the system for different types of convolution and image processing algorithms."

In addition to the cost and configuration savings, the quality of the product has also been improved with the shift to the Falcon. Instead of using 512x480 interlaced (RS-170) video images, the new system utilizes 640x480 non-interlaced VGA displays. This provides more resolution while also decreasing eyestrain for the system operator.

The new version of the Model 66Z has already proven itself in the field. According to Ralph Sheridan, President of AS&E, one of the new systems "has demonstrated its effectiveness by finding a mail bomb for one of our corporate clients." Although this might seem to be nothing special (after all, it’s what the system is designed to do), Sheridan emphasizes that this is very significant. "It is very rewarding to know that their investment in higher technology detection has paid off by protecting their office personnel from a terrorist bomb."

AS&E also feels that Univision has proven itself as a responsive, reliable vendor of this technology. "Univision was extremely supportive and helpful" throughout the development process, says Tanch. "There were a lot of issues that needed to be resolved (on both sides) during this project." Tanch is impressed that the entire project was able to move from concept to production in a little over six months.

As they adapt other products over the next few years, AS&E is looking forward to continued success with an FPGA approach.

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