In many postal-sorting, web-inspection, and semiconductor-manufacturing applications, barcodes and barcode readers are used to identify and track parts and products. Because barcode systems must often operate in rugged environments, systems integrators must pay careful attention to the selection of illumination methods, cameras, and image-processing software. To aid integrators, OEM lighting, camera, frame-grabber, and software vendors are building products to address these needs.
At recent trade shows, several lighting vendors introduced light-emitting-diode (LED) lighting products specifically for machine-vision applications (see Vision Systems Design, May 2000, p. 55). These lamp-based products provide a uniform, flicker-free light source, feature lifetimes to 100,000 hours, and use less power than incandescent or fluorescent lamps. Despite these benefits, however, they still do not supply enough illumination for many high-speed machine-vision applications.
To overcome this problem, Dalsa (Waterloo, Ontario, Canada) has developed the Eclipse linescan camera that the company claims has 100 times greater sensitivity than its previous Spyder linescan camera. "Greater responsivity allows for less-expensive lighting, such as LED or fluorescent, and an increased depth of field by enabling the use of a larger f-stop in the optics. Built-in processing for fixed pattern noise and pixel-response nonuniformity correction can further compensate for nonuniform lighting and optics degradation, allowing cost-reduced lighting and optics," says Mark Butler, Dalsa product manager.
Available in 512, 1024, and 2048 resolutions, the bidirectional Eclipse uses a 512 x 96, 1024 x 96, or 2048 x 96 time-delay-and-integration sensor, respectively. However, because the device output appears as an 8-bit RS-644 low-voltage differential-signaling-data output, the device performs as a single linescan CCD sensor. In this way, Dalsa's engineers have dramatically increased the sensitivity of the camera.
At the recent AIA Vision Show East, Dalsa debuted its Eclipse camera interfaced to the PCI-based RoadRunner frame grabber from BitFlow (Woburn, MA). In the BitFlow booth, the camera was shown digitizing and reading barcode symbols at a rate of greater than 80 barcode symbols per second under poor lighting conditions using the SwiftDecoder PC-based software for 2-D image readers from Omniplanar (Princeton, NJ). Capable of reading both stacked and matrix codes such as Code 39 and MaxiCode, PDF-417, and DataMatrix, the software can also recognize the company's Minicode barcode symbol.
Minicode exploits the fact that most barcoding applications repeatedly scan a small amount of data stored on labels. It superimposes a long message or data file onto a short message or license plate. Because the license plate encodes frequently needed data and the data file carries less frequently needed data, in many instances, Minicode readers need only read license-plate information.