Those who were involved in manufacturing in the 1980s will no doubt remember the enthusiasm for vision systems, particularly in the automotive sector. For a few short years, this relatively new technology, called machine vision back then, was all the rage; hopes were high for vision-based inspection systems, and so were the price tags. When too many of the systems, however, proved to be difficult to operate and maintain, customer enthusiasm for the technology waned. Jeff Schmitz, corporate business manager, vision products, for Banner Engineering Corp., Minneapolis, sums it up this way, “In the late ’80s, vision technology was over-promised and underdeveloped.”
Fortunately for vision providers and their customers, things have changed. “Just about every aspect of the underlying technology has vastly improved over the years,” says Nello Zeuch, a vision consultant and president of Vision Systems International, Yardley, Pa. “Starting with cameras. We now have cost-effective solid-state cameras. Back in the late ’80s and early ’90s, solid-state cameras were so expensive, they were rarely used. Instead, people used vacuum tube cameras, which had difficulties in the industrial environment. The new cameras provide higher resolution so you can have more sensitivity in what you can detect.”
Zuech adds that the greater connectivity capabilities of digital cameras can readily turn a personal computer (PC) into a machine vision system. If needed, intelligent frame grabbers can plug into the PC to ensure that it can handle most, if not all, of the image processing tasks that it is called upon to do.
Lighting, the bugaboo of many early vision applications, has also been simplified. Formerly, “staging” an application—that is, physically setting up the lighting, camera and part to be inspected, and divining the correct parameters for all three—was generally a difficult and time-consuming job. And once the system was in operation, changes in ambient lighting or atmospheric conditions within the plant often threw the carefully calibrated lighting for a loop.
The situation is quite different today. Increases in computing power have allowed vision system providers to employ software algorithms that are better able to handle variations in lighting. Today's lighting components exhibit greater stability and can be customized to the application. Information on lighting for vision applications is readily available on the Web and elsewhere. All in all, says Banner's Schmitz, lighting has been “demystified.”
Enhanced capabilities, yes; still, levels of application vary widely between industries, so why has packaging become such a hotbed of vision activity? Steve Geraghty, director of ipd, a group of Dalsa Digital Imaging, Billerica, Mass., cites “the demand on the packaging industry to produce smaller and more complex packages at higher volume,” coupled with the changes in vision technology that make it “less expensive, easier to deploy and more aligned with today's packaging needs.”
Those needs have been heightened by the Food and Drug Administration’s 2001 allergens regulations (Sec. 555.250 Statement of Policy for Labeling and Preventing Cross-contact of Common Food Allergens) and the Bioterrorism Act of 2002. The FDA allergens regulations require that food that comes into contact with any of eight common allergens, which together cause approximately 90 percent of allergic reactions in the United States each year, be clearly labeled. The Bioterrorism Act stipulates what’s been called “one step back, one step forward,” that is, each part of the food chain must be able to trace its source back one step, and trace the destination of the food one step forward.
“The keyword is traceability,” says Blake DeFrance, product marketing specialist for In-sight vision sensors for vision vendor Cognex Corp., Natick, Mass. “And this is where vision systems are proving to be invaluable,” DeFrance continues. “They can track and trace, either through an image that can be captured and archived, or through a bar code. In addition to reading bar code, though, a vision system can perform quality and product safety operations. It can tell you if a safety ring is on, or on correctly. It can prove that the correct label is put on the correct container. It can check for foreign matter in liquids by verifying fill level, because foreign matter will raise the level. It can perform sorting and grading operations that can help improve production. These are all things that a laser bar code reader can never tell you.”
Even in terms of bar code reading, DeFrance claims an advantage for vision systems: 2D bar codes can be read easily by a vision system, while it can be expensive to configure a laser bar code reader to perform the same task.
Central to the growing use of vision in packaging, says DeFrance, has been the emergence of a continuum of vision products, such as the low-cost and easy-to-deploy vision sensor. Consultant Zeuch agrees. “Vision sensors are the baseline in terms of vision products. They can successfully verify presence/absence and perform a variety of other tasks. Today’s vision sensors have performance equal to or superior to the full-blown vision systems of 15 to 20 years ago. So the capabilities that were promised 20 years ago are now available off the shelf.”
In packaging, vision sensors are increasingly being used to replace photoelectric sensors. For decades, photoelectric sensors have successfully performed a variety of functions on packaging lines. The problem is, their use is limited by their single beam and lack of computing power. Vision sensors, with their ability to capture and analyze multipixel images, are well suited to handle a wider array of inspection operations, bringing the potential for higher levels of quality and traceability. And the cost of these mini-vision systems? Many units are priced at around $1,000, and they possess a ruggedness not typical of the vision products of the past.
Of course, these low cost devices can’t do everything a full-blown vision system can do. The main limitation is line speed. A vision sensor’s exposure time may not be fast enough to correctly capture the needed details if the objects to be inspected are on a very fast-moving line. Also, more complex inspections, in which more than one inspection operation is performed, require more processing time, which also slows the sensor.
There are ways, however, to extend the application reach of these powerful little devices. Increasing the light decreases exposure time, which can allow vision sensors to handle line speeds beyond their normal reach. And complex inspections can be broken down into their constituent parts and handled by two or more vision sensors. For example, one vision sensor might handle a required fill inspection, while a second simultaneously performs label inspection. And unlike the often delicate and skittish vision equipment of the bad old days referred to at the top of this article, vision sensors are tough.
“Our vision sensors have an IP67 rating, which means they can stand submersion,” says Jim Anderson, sales engineer for the packaging industry for Minneapolis-based Sick Inc. “That’s an obvious plus in packaging, since the packaging lines are frequently washed down.”
Other vision sensor providers also point to their IP ratings—a clear indication that the need for plant floor toughness is a lesson the industry has learned. Anderson adds that his company’s “smart cameras” carry ratings up to IP65, meaning that while not submersible, they can take direct water during cleaning operations, making them an attractive option for packaging-line inspection operations.
Cameras with smarts
The smart camera is the next step up in the continuum of vision products. “All the processing and lighting is done in one unit,” says Anderson, “and programming these systems is getting increasingly easy and more user-friendly.” These compact smart cameras, available from several vendors, have more on-board intelligence than vision sensors. In fact, some of them can handle today’s most compute-intensive applications.
Though they are getting more user-friendly, programming digital signal processing (DSP)- or field programmable gate array (FPGA)-based smart cameras can be time consuming for programmers who aren’t familiar with these technologies. In addition, smart cameras that use a general purpose processor like Pentium Mobile can generate enough heat to affect image precision. Still, the combination of advanced capabilities and relatively low cost is gaining a growing market for these devices and ensuring continued technical development.
Cameras, whether the standalone smart variety or part of conventional vision systems, promise to play an even bigger role in the evolution of vision-based inspection. Of particular significance for the packaging industry is the trend toward 3D cameras. One of the knocks against 3D cameras is that because they are more complex than 2D cameras, they are more difficult to program. That’s changing, thanks to advances in software programming, and the trend is toward more user-friendly—and cheaper—3D cameras in the future.
Why should packagers care? 3D cameras provide users with height data, which can be valuable in many applications. For instance, if you are packaging turkey breasts, meat, baked goods or any of a number of other food products, the volume of the product is of interest.
What else is in store for vision system cameras? No one can say for sure, but to get an inkling of what may lie ahead, take a walk through the mall. At the camera store, or even the drugstore, you will find small, cheap digital cameras with good resolution and an increasing array of features. Down at the phone store—or at the food court, where the teenagers hang out—you will find this year's picture phones, all of them with more sizzle than last year's models. Wander into the computer store, and you can learn how to use your PC to send live video (or still photos excerpted from that video) anywhere in the world.
The point is, digital imaging technology spawned by the frenetic pace of product development in the consumer realm will impact vision systems. Look for smaller cameras with excellent resolution and a smaller price tag to result.
Matthew Slaughter, vision product marketing engineer, National Instruments, Austin, Texas, adds that we should also be looking at software and communication if we want to know where vision is going. “Vision applications are growing in packaging because vision is a much more efficient way of checking products, and because vision systems are getting easier to use. This ease of use comes primarily from the software that's available now. In the past, you almost had to be a hardcore hacker to configure some tasks.” Today, says Slaughter, function libraries and graphical programming environments have drastically simplified many programming tasks.
“Sure, this is a high tech product,” says Cognex’s DeFrance, by way of summing up. “But everybody is aiming to make vision systems easier to use. And we're succeeding.”
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