MoviMED was profiled by Vision Systems Design Magazine for the way they overcame significant challenges when designing and building a high-speed inspection system for gauging metal cylinders.

MoviMED developed a customized server, high-resolution cameras, and data/image acquisition hardware communicating via optical fiber to support high-speed inspection:

Among the factors that needed to be addressed were measurement of a 9-mm-diameter cylinder that is 2–3 in. long with micron precision despite mechanical fixtures; triggering from an optical encoder; and cameras with minimum spatial resolutions in the 3–7-µm range. Designers could also expect the ambient conditions to affect cylinder placement: The system would operate in a plant where temperatures vary from 50º to 110ºF and part temperatures vary from 50º to 150 ºF.

MoviMED assessed the impact of curved surfaces on sub-pixel interpolation and went through an iterative software development cycle to optimize parallel image processing on multicore microprocessors. MoviMED was compelled to design a system that uses specialized high-resolution, global-shutter cameras; Camera Link-over-optical-fiber connectivity; data acquisition and frame grabber boards; and a server running a real-time OS and image-processing algorithms on twin quad-core Xeon microprocessors.

MoviMED designed a system that uses high-resolution, global-shutter cameras; Camera Link-over-optical-fiber connectivity; data acquisition and frame grabber boards; and a server running a real-time OS and image-processing algorithms on quad-core microprocessors.

 

One way MoviMED was able to achieve micron-level measurements across a large field of view was by using two high-resolution DALSA cameras and a prism for each camera. The prisms allow the two FOVs to be stitched together for image processing while minimizing correction and calibration requirements.

 

Sub-pixel interpolation

The cylinder inspection system uses two 4-Mpixel DALSA cameras with global shutter along with sub-pixel interpolation to achieve micron-level measurement precision of the cylinders’ dimensions.

Timed for success

Because the cameras are located 30 ft from the processing unit and pass up to 320 Mbytes/s, MoviMED incorporated EDT’s RCX optical fiber Camera Link extenders to communicate between camera and processing unit.

Maximizing multicores

MoviMED’s programmers developed the image-processing and communication routines to run balanced on two quad cores: one for image processing and the other for communications and diagnostics. “What we learned is that, while you still want your code to work in parallel as much as possible, there are still sequential operations that need to happen in a specific order and time. So we had to write the code to be in part parallel and also in part sequential,” concludes Tarin. “It all comes down to the specific components and which algorithms you use. When you’re trying to balance code like this, every system is unique, every system design custom. The good news is that with LabVIEW we were able to move code around and quickly change things. If we had to do this in C, we still wouldn’t be done.”

MoviMED’s system has been fully tested and is ready for installation. A final addition was a cooled hermetic enclosure for the lights and cameras so that large swings in ambient temperature will not impact the system’s measurement accuracy due to the thermal expansion of components and fixtures.

Read the full article in Vision Systems Design Magazine On-line