eration on one pixel and immediately move to the next on
that same pixel without waiting until the entire image has
been processed. Partitioning an image-processing problem correctly to take advantage of the different strengths
of the various processor options can thus boost performance.
Such chip improvements pay off when QC is done
online as part of a go/no-go decision that marks a part
as good or bad. However, processing advances also help
when inspections are made offline as part of a post-manufacturing evaluation. The automated optical comparators made by Keyence Corp. of America, based in
Elmwood, N.J., for instance, backlight a part and then
can take hundreds of dimensions in second.
“If you have a turned part, there’s probably lots of different diameters you would want to measure,” said Mo
Brodeur, technical marketing engineer in the company’s
Micro Analysis Group. A threaded part, for instance,
potentially could be screened for its diameters as well
as for pitch and thread angles. Likewise, a stamped part
also could undergo quality checks related to dimensional
According to Brodeur, better processing is part of what
makes it possible to do more measurements in a shorter
time than before.
Improving systems communication
Advances such as these have eliminated image processing as the bottleneck in inspection throughput,
National Instruments’ Treece said. Consequently, the
communication between the vision and motion control
systems can become the holdup. One way to get around
this is to use hardware that supports the IEEE 1588 precision time protocol standard. Synchronization between
systems can drop from milliseconds to less than a microsecond, Treece said. That makes it feasible to stack
steps instead of sequencing through them, saving time
and boosting throughput.
Another way to solve the communication bottleneck
and achieve desired results is a new architecture in which
a high-performance vision system hosts everything.
That was the option chosen by Master Machinery Corp.
of New Taipei City, Taiwan, for its pick-and-place
systems. These take a chip off a silicon wafer and put
it into a package, with a quality control check along
the way. Eliminating lag time and delays enabled the
company’s machines to go from an industry-standard
2000 parts per hour to more than 20,000 parts per hour,
Another example of an approach to improving QC that
makes use of various techniques comes from Radiant
Vision Systems in Redmond, Wash. The company makes
automated visual test and inspection systems for displays
and illuminated components.
Displays must be visually consistent and pixel-level
defects that impact the color or intensity are important.
For that reason, Radiant uses an imaging colorimeter
that is designed to reproduce the average response of the
human eye. Resolution of the systems can run as high as
29 megapixels, allowing small defects to be picked up
across a wide field of view.
Improvements in silicon
have resulted in faster chips
that benefit both image processing
and automated decision-making.
Polarization sensors can allow QC inspection of features that are not possible by traditional means,
such as the thickness of transparent films.
IP July 2017
Quality Control Feature
A turned part processed by a lathe can be inspected quickly and accurately using optical imaging.
A 3D vision system inspects heat-sealed bags.