Machine-vision systems use networking for expandability
At this month`s Vision Show in Santa Clara, CA, PPT Vision (Eden Prairie, MN) is demonstrating what the company claims is the world`s first digitally networked machine-vision system. Dubbed Passport DSL, the product line consists of digital cameras, input/output (I/O) hubs, and image processors that communicate with each other through a digital-serial-link (DSL) network. Each subsystem in Passport DSL uses a chip set that allows two-way serial transmission of digital images, data, and trigger signals to be transmitted across the network at 330 Mbit/s.
To digitize images and transmit them over the network, the company has designed a series of digital cameras that can be configured with software using a graphical set-up screen. The first camera to be introduced is the DSL 6000, a 640 ¥ 480 progressive scan camera capable of asynchronous image capture in either strobe or shuttered mode at a speed of 70 images per second.
"Unlike conventional systems, images from the camera are not digitized by a frame grabber. Rather, they are digitized at the camera source and transmitted digitally over the network to a hub. Because of this, cameras can be remotely located up to 600 feet from the hub," says Steve Tonkin, PPT Vision engineering manager.
Each hub can support a maximum of four cameras, which are, in turn, linked via the network to the PC-based Passport DSL machine-vision processor. In the processor, a DSL PCI-based card is interfaced to a C30-based image processor and an image-processing accelerator card. In operation, each hub on the network arbitrates when image data are sent to the image processor.
To perform image-processing operations, Vision Program Manager software is invoked from the Passport DSL host image processor. Image inspection is set up using icons that represent inspection functions, and the icons are connected by lines to establish process flow of the images.
"To set specific parameters, dialog boxes related to the icons allow system developers to tailor the inspection tools. These inspection tools can identify and analyze features, perform measurements, verify the presence of required features, and locate important shapes within images," says Arye Malek, PPT Vision vice president of marketing.
Because the system is network-configured, the hubs can be interconnected in a daisy chain or a tree arrangement or a combination of both. By digitally buffering all the cameras on the system simultaneously, up to 16 views of an object or objects can be acquired simultaneously and then processed.
To configure such networked systems, the company has developed a software tool called DSL Manager. Using a presentation similar to the Device Manager of Windows `95, DSL Manager provides a graphical way to set up and supervise the DSL network of multiple hubs, cameras, I/Os, and lighting equipment. Because all the DSL network components report their status to the DSL manager on request, the networked system is continuously updated.