Advanced Imaging

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Advanced Imaging Magazine

Updated: July 8th, 2008 05:26 PM CDT

Choosing an Interface

How to Choose an Interface for Your Application
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By Kristin Lewotsky

No matter how sophisticated its technology, a company is only as good as its communication. Similarly, no matter how advanced the components of a digital imaging system, performance is only as good as the interface. How do you make the right choice, whether you’re a camera manufacturer, a system integrator or an end user? As with many things, it comes down to understanding your choices and applications.

Although analog cameras still represent the majority of imagers sold, the proportion of digital cameras sold is steadily rising. There are four major interface formats currently vying for position in the digital imaging market: USB, FireWire (IEEE 1394), Camera Link, and GigE Vision. Although USB offers the familiar plug-and-play performance we’re used to from consumer computer applications, it was never designed for imaging. It may be appealing for certain medical applications that require plug-and-play performance, but it lacks the speed and control options of the alternatives, so we won’t focus on it here.

FireWire is a cabling interface intended for a wide range of applications, not just machine vision. It offers power within the cable, but it’s not fast enough for high-resolution imaging, not compatible with networking, and it is not as broadly supported by computer manufacturers.

The Camera Link Connection

Prior to the development of these standards, the basic interface was parallel LVDS, which left far too much unspecified. “Every camera manufacturer used a different connector and pinout, every frame grabber also had a different pinout and connector as well,” said Steve Kinney, product manager at JAI-Pulnix (San Jose, Calif.) and Camera Link standards committee chair for the Automated Imaging Association (Ann Arbor, Mich.). The chaos motivated the effort to develop digital interface standards specifically for machine vision.

Camera Link was the first AIA standard released. Requiring a frame grabber, it offers speeds of nearly 700 MB/sec over cables as long as 10m, and real-time camera control from the frame grabber to the camera. The industry verdict so far? It works. “For a high-speed application where minimal or zero latency of the image delivery is required and we want a strong set of controls over camera hardware,” said David Dechow, president and owner of system integrator Aptura (Lansing, Mich.). “I think there’s nothing at this moment that can do more than Camera Link.”

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