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Machine Vision – Scanning Technologies
High-performance scanners and reading technologies play a key role in ensuring that letters and packages reach their destinations quickly. In addition to capturing address data on up to 60,000 pieces of mail per hour, these machines read Arabic and Chinese. In addition, the automobile and aviation industries are investing in reliable reading systems and counterfeit-proof markings in order to protect their products.
They look like a combination of a stretched out filing cabinet and photocopier. But the blue-gray behemoths that are 40 m in length and produce a soothing clickity-clack sound each time a postcard or letter arrives—in other words, some 60,000 times per hour—are actually giant letter sorters. They drone along in a large hall the size of a shopping center at Siemens Postal Automation (PA, Industrial Solutions and Services Group) in Konstanz, Germany, where they are built and tested. Envelopes whiz along the machines’ conveyer systems at four meters per second—so fast that you can only make out an endless white ribbon instead of individual letters.
Each system’s scanner can read and capture not only the address, but also the images of 17 envelopes per second. That’s a world record. Addresses read, the machines spit the letters into bins according to street and house numbers. People are needed only to feed the machines with more letters. The rest is handled by the gigantic machines, regardless of whether a stamp has been pasted incorrectly or an address is illegible or written in Arabic.
Udo Miletzki is one of the people who worked hard to ensure that such machines can function intelligently. In fact, he’s been refining increasingly intelligent recognition methods for over 30 years. "Before new systems can be delivered around the world, they are tested here," says Miletzki, who grew up with the postal sorting business from its beginnings. "Then, after being thoroughly evaluated, the machines are set up on the customer’s premises in exactly the same way." That’s how it was in 1973, when the company got its first big order from the German Postal Service for the construction of an automatic address reader. The first system of its kind in the world went online in 1978 and was able—even then—to process 36,000 handwritten ZIP codes per hour.
Today, letters in Germany are brought to so- called incoming-mail post offices and read by machines like the one in Konstanz. The address is registered and printed on each letter as an arrangement of lines—a barcode—in pink. Then the trip to the letter’s destination begins. Thanks to the code, the address doesn’t have to be read in again. The barcode contains all the address information needed and guides the letter reliably through the final sorting machine. Even the route the mailman will use is taken into account during this process.
The newest postal recognition technology, which is known as ARTRead, breaks new ground. In contrast to previous methods, many different types of mail can be read with it: letters, parcels or glossy magazines. ARTRead utilizes special high-performance Siemens scanners that have a resolution unprecedented for this velocity class—up to 300 dpi. The software can even recognize printed text that is hard to read. In addition, the system has command of many languages and address formats. Particularly in countries in which different alphabets are mixed—for example, Latin or Cyrillic alphabets—ARTRead is helpful. In fact, there is no written language that can’t be read using this technology, which was developed in Konstanz.
Digital Fingerprints. To make sure that newspapers, parcels and letters reach their recipients dependably and quickly, Miletzki and his colleagues have developed a "fingerprint" method that will start as a pilot project for a large European mail service in 2007. The system will help facilitate delivery of large pieces of mail, such as oversized envelopes, heat-sealed magazines or padded envelopes. "For example, it’s very difficult to stick barcode labels onto slippery plastic foils or to print barcodes on them," says Miletzki. Furthermore, special instruments and huge amounts of ink make barcodes expensive.
But that’s all ancient history thanks to the fingerprint. This system captures the front of the envelope as a digital image that is as unique as a fingerprint. Unmistakable characteristics are extracted from each envelope and assigned to the delivery as a binary number code. This image is stored in a central database along with address information. Each letter is scanned again at its destination and its fingerprint is transmitted to the center. Within fractions of a second the center returns the previously read, related address information.
Each letter’s characteristics are captured by high-resolution scanners and analyzed by software like ARTRead, which has been trained using thousands of address samples, letters and types of handwriting, so that everything functions successfully. Statistical methods then help the software to determine which symbol a sign or handwritten word is most similar to.
Saving Hundreds of Millions of Dollars. Siemens Postal Automation leads the market worldwide with a 66 % market share (for installed systems) in the field of letter sorting systems. The most significant new developments in this area are based on an intelligent linking of recognition technology with information systems. This includes PARS—the Postal Automated Redirection System, which has been used in the United States for the last few years (see Pictures of the Future, Fall 2003, Postal Automation). "17 % of the U.S. population moves every year," says Rudolf Klink, a marketing manager in Konstanz. Because of unregistered changes of address, billions of pieces of mail end up as ‘dead letters’—representing an enormous cost in time and effort for the US Postal Service."
PARS prevents letters with obsolete addresses from being sent to a prior place of residence. If a person relocates, his or her mail is diverted to the new address. The system works this way: A database stores old and new addresses. If a letter with an old address is recorded, PARS will transmit it to the new destination in spite of the wrong address.
This system has clearly speeded up delivery, substantially reduced the amount of misdirected mail, and made it possible for the US Postal Service to save several hundred millions of dollars annually. Meanwhile, a similar, slightly modified forwarding system is now also being utilized in Germany, Denmark and Switzerland. The PARS order from USPS—with a value of 460 million euros—was the biggest that Siemens Postal Automation ever landed in its fifty-plus-year history.
The objective for ever more sophisticated sorting systems is clear. Distribution must become even faster and more economical. That’s also the goal of Switzerland’s postal service, which is planning to centralize distribution in three big mail centers. Today, letters with illegible addresses are video coded. The images are sent to computer workstations, where employees read the data and type the entire correct address into the system. Video coding is well-established, but it is time-consuming.
The new video codec system does not require the full address to be typed in. Employees need only fill out the portion of the address that the machine is unable to read. Furthermore, video coding can take place far from distribution centers.
Letter-sorting installations can simply send envelope images to workstations for processing. The address is usually completed and returned while the letter is still in the machine. When the letter leaves the machine, it’s marked with the right destination.
But thanks to the fingerprint method and the ARTRead system, video coding can probably be dispensed with altogether in the foreseeable future, according to Miletzki. For experts at Siemens PA this is not only a question of speed, but also one of quality and reliability—and the prevention of fraud. To that end they have come up with a system that checks whether letters are correctly postmarked or not. PA’s "Revenue Protection System," for instance, can recognize if the postage mark is legitimate or from a stolen machine—once again, thanks to a connection to a database.
Workers in Konstanz have been fine tuning mailing systems for over five decades. But they still haven’t run out of ideas. In conjunction with a number of companies and the German Research Center for Artificial Intelligence in Kaiserslautern, they’re working on a project involving a reader that will understand semantic information. In other words, this device will be able to understand word meanings in their context. For example, a word like "Konstanz" could crop up in various places in an address—in the town, street or company name—and that can confuse even the most sophisticated sorting system.
Automatic semantic evaluation of text, on the other hand, could make sorting machines even smarter than they already are and also make it possible for new web services to handle daily mail communications more effectively.
Coding Ships’ Engines. Another well-established postal automation technology is "data matrix code" (DMC) or "2D code"—the use of a square that is filled with a dot pattern. In contrast to barcodes, DMC can be scanned from every angle and requires up to 100 times less space for the same information content. Furthermore, it can still be read even if small areas are scratched. Post authorities allocate the codes—similar to the numbers in Internet banking—from a central database that protects DMCs from falsification.
Data Matrix Code processing requires high-performance reading instruments, such as the scanners produced by Siemens Automation and Drives (A&D) in Nuremberg. There, specialists regard the reading and verification of individual and counterfeit-proof markings as nothing more than part of day-to-day business.
To them, the issue involves not only letters, but also printed circuit boards, airplane components and ships’ engines. That’s because many industrial businesses—especially automobile manufacturers and aviation-related companies—have recognized the advantages of DMC and are already marking many of their products with it.
The special thing about data matrix codes is that their dots can be imprinted directly on a given part more easily than the stripes of a barcode. Depending on the material, the dot pattern is burned in by a laser, etched into metal with needles or applied with special inks. Experts refer to this as Direct Part Marking (DPM).
Thomas Beck, a Product Manager at A&D, says that "we are currently at the beginning of a growth curve with regard to 2D code." Today, 1,800 reading operations per minute are already possible.
Reading and interpreting a code with instruments from the Simatic HawkEye series, which have very good optics and excellent software, takes less than 100 milliseconds. Furthermore, dot patterns can be read even if there are disrupting reflections on the surfaces of parts, problems with low contrast, and changing lighting conditions. "The quality demands on these systems are primarily the same ones that have been placed on the performance of postal systems," says Beck. "These have taken a great leap forward."
A&D’s position in this area has been strengthened recently thanks to the purchase of Acuity CiMatrix, a U.S. company that was the world leader in matrix code reading instruments and image processing systems in 2005.
Worldwide Authentication. Another challenge lies in integrating DPM and DMC into an extremely wide range of production lines. To accomplish this, Siemens maintains a Solution Partner Program for Machine Vision with ISW of Hamburg, Germany, a leader in the development of customized data matrix systems for a wide variety of industries.
"For one thing, we test which DPM method is best for marking the customer’s products or components," says ISW’s Ulrich van Groningen. "For another, we analyze how the instruments can be integrated into production." That means that ISW employees test the customer’s parts directly in their laboratories to determine which type of marking is the most suitable for the materials involved and which reading system is best for the application.
The company recently developed a data matrix system to mark Lufthansa’s turbine blades. Here, jet engines are completely dismantled for maintenance and individual blades are reworked or replaced whenever they are damaged.
Blades are individually marked with the 2D code to ensure that each of them is mounted back into the same position later. "The code also serves as protection against counterfeit or old parts that are brought to the market with false declarations," says Beck. And that doesn’t only apply to aircraft parts. Here too, the 2D code is just beginning to become established. After all, reliable communication networks are a prerequisite of a monitoring system like this one. They ensure that DPM data stored centrally with a manufacturer can be sent anywhere in the world within seconds.
Aircraft manufacturers that mark their parts using counterfeit-proof DPM technology are one example. If a customer replaces a component at some point, the component’s code is read in and authenticated by the manufacturer via Internet.
Beck is certain that with the establishment of reliable central data memory and linked DPM reading systems, 2D code will become a high flyer in plenty of industries in addition to aeronautics.
Source: Siemens I&S PA, Udo Miletzki