Software makes machine vision easier
Good vision software must work well with external devices and applications.
Jon Titus, Editorial Director -- Test & Measurement World, 10/15/2001
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A key part of any inspection system is the software you use to gather and process images. In fact, you may want to choose a software package first and then buy compatible hardware, rather than purchase a hardware system only to learn it can't run the software you need. Several software suppliers have developed machine-vision packages that find edges, make measurements, identify shapes, and locate imperfections(see, "What's new in software?" p. 18). The suppliers can tell you which frame grabbers and cameras work with their programs. They can also help you locate suppliers of accessories such as camera cables and lenses.
Of course, once you acquire the images, you need to know what to do with the information you gather. Your machine-vision project will fail if you are unable to properly use—or even gain access to—the results from an inspection.
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| Pattern-matching tools can tell the difference between different objects that conform to models set up by a user. Modern software tools easily handle hidden areas, rotated objects, and objects of different size. Courtesy of Matrox Imaging. |
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| Some vision tools can match colors to ranges preset by a user. Color capabilities expand the types of applications a machine-vision system can tackle. Courtesy of National Instruments. |
If all you need is a display of pass/fail information, any software package will meet your needs. But most people want to use inspection data in other ways. They may need to distribute the data, use it in another local application, or initiate an external action. Thus, the machine-vision software you plan to use should supply drivers that let it quickly communicate results to other programs.
Those other programs can route the data, say dimensional values, to a corporate database or to a statistical process-control program. And the machine-vision software should provide its information in a format that makes it readily accessible to commercial programs and your own custom programs. ActiveX controls and OLE provide standardized ways to exchange information.
If you plan to use the results from your machine-vision software to perform an action, you must ensure your vendor supplies drivers for I/O devices or boards. In an ideal situation, the machine-vision software could actuate an arm on a production line to shunt failed products into scrap or rework bins. In such a case, the host computer needs a digital I/O board and signal conditioners to detect the state of sensors. The host might also need a bank of solid-state relays to control actuators.
You must check the software's specifications to ensure the supplier offers either the drivers needed to control a digital I/O board or the necessary links that will let you connect the software to control products from third parties. Suppliers may list compatible I/O boards in the software's specs.
Of course, you must also ensure the software you choose will process the images you acquire in ways that make sense for your application. These days, most machine-vision software packages provide good tools that let you program complex machine-vision tasks. So, rather than comparing packages feature for feature, you might find out how long it takes from opening the software box to getting your first test application to run.
| Author Information |
| Jon Titus has written real-time software and designed embedded systems and computer/instrument interfaces. He worked in electronics for 10 years and spent nine years at EDN magazine prior to joining T&MW in 1993. He has a BS from WPI, an MS from RPI, and a PhD from VPI. E-mail: jontitus@tmworld.com. |
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