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Machine Vision Searches for Interface Standard

Machine Vision Searches for Interface Standard

There has been an explosion of new camera interface standards for machine vision. In 2011, the industry got three. Two of them, finalized in March, apply only to machine vision and are found nowhere else: Camera Link HS and CoaXPress. The third, USB3 Vision, was announced for the first time in October by the Automated Imaging Association (AIA).

Unlike interface standards based on bus protocols designed specifically for vision, manufacturing engineers and quality control engineers also build vision systems based on general-purpose protocols such as USB 3.0, known as "SuperSpeed" USB. For only the second time -- GigE Vision was the first -- the industry is taking this one step further and codifying a vision-specific standard based on a bus already widely available in off-the-shelf hardware. The AIA expects to release the final version toward the end of 2012.

"All of these standards have different advantages and serve different needs," says Eric Gross, chairman of the AIA's USB3 Vision Committee, and senior software engineer for National Instruments' vision group. "In the case of USB3 Vision, that need is high speed, up to 3.2Gbit/s per cable, which is faster than all of the current standards except Camera Link HS and CoaXPress. Unlike them, a USB3 Vision camera can plug into any USB 3.0 port. These are about to become available on most PCs." Power and data can be run over the same cable up to five meters without amplification, compared to 45 meters for CoaXPress and 100 meters for GigE Vision.

USB has been the most successful interface in the history of the PC, in terms of volume. Ports are available on nearly all PCs, and increasingly on embedded hardware as well, says Gross. Many PCs also have Ethernet ports, but that interface is not as ubiquitous as it had been.

Many in machine vision adopted USB 2.0. But without a camera interface standard, anyone building a vision system had to use an SDK provided by the camera vendor. "This limits your application to the OS and devices that the camera vendor supports, which can be a problem if you're using cameras from multiple vendors. If you want to run the camera on an RTOS, you're out of luck unless the camera maker happens to have drivers for the specific RTOS you're using."

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