Vision systems need processing power

As PCB feature and component sizes continue to get smaller, vision systems require cameras with higher pixel counts to properly resolve tiny visual characteristics. Thus, high-performance machine-vision systems must process larger and larger quantities of data. Simultaneously, PCB manufacturers demand faster inspection times. As a result, incoming data may rapidly overwhelm a vision system. Traditional frame grabbers may have a difficult time keeping up with the flow of video data because the main bus in host PCs often causes a data-flow bottleneck. Some frame-grabber manufacturers resort to using a separate card-to-card bus that establishes an independent path between frame grabbers and memory or processor boards. But getting the data to memory is only half the battle. Once saved, the host CPU must process image data so software can locate targets and identify defects. To help speed processing tasks, some manufacturers have placed processors—often digital signal processors (DSPs)—on their frame grabbers or offered them on separate boards.

Older vision systems that need more CPU power can take advantage of PCI and ISA slots on a Pentium-4 motherboard from CyberResearch.

The need to unburden a host CPU may diminish, though, when PC builders adopt the new PCI Express bus. The PCI Special Interest Group (www.pcisig.com) expects the new bus to run with a 16-Gbits/s bandwidth using a 32-lane configuration. According to Jason Mulliner at National Instruments, vision-system designers should find this bus satisfies their needs to quickly transport data from a frame grabber to a host PC's memory. And as CPU clock frequencies increase, a host PC will process image data as rapidly as the most demanding applications require.

The PCI Express bus won't help everyone. Engineers with legacy computers will hit bus-speed limits as they seek to increase the processing power of their systems. Help is at hand, though. CyberResearch (www.cyberresearch.com ) recently announced a 553-MHz Pentium-4 motherboard (MXIB) that includes the usual three PCI card slots as well as three ISA card slots. The motherboard ($595) can run a P-4 processor at over 3 GHz and will accept up to 2 Gbytes of RAM. Most engineers may have thought they'd seen the last of the ISA bus, but this venerable standard seems to defy obsolescence.