Y-axis optical array
October 2017 VISION SYSTEMS DESIGN www.vision-systems.com 14
stage, the PLC triggers an In-Sight 5605
smart camera vision system from Cognex
(Natick, MA, USA; www.cognex.com) to
acquire an image.
The image is first analyzed by the camera’s
on-board processor for pre-inspection alignment to determine package orientation and provide X, Y and T coordinates so that a vacuum
chuck on the gantry can pick up the package in
the correct orientation for inspection.
Since between the eight pouches on each
package are four seal lanes in one direction
and five lanes in the other direction (Figure 2),
engineers specified no less than nine cameras
in the design of the two upward-facing optical
During operation, the material handling
system first moves the package over the y-axis
optical array which includes four camera/lens
stack and light assemblies. Then the material handling system moves the package over
the x-axis optical array which includes five
camera/lens stack and light assemblies.
For each camera/lens stack and light assembly,
engineers specified an Ace 2048 x 2048 monochrome camera from Basler (Ahrensburg,
Germany; www.baslerweb.com), which features a CMV4000 CMOS image sensor from
CMOSIS (Now ams Sensors Belgium; Antwerp, Belgium; www.cmosis.com).
To meet the resolution requirements of the
application, each camera’s 4 MPixel global
shutter sensor, which has a 5. 5 µm pixel size,
is paired with a 40mm lens from Schneider
Optics (Hauppauge, NY, USA; www.schneideroptics.com). This arrangement achieves a
25-mm field of view.
The four cameras of the y-axis optical array
connect to an industrial PC (iPC) from Advan-
tech (Milpitas, CA, USA; www.advantech.
com). Likewise, an identical iPC controls the
five-camera x-axis optical array. The iPCs are
arranged in a master-slave configuration with
the master running an OPC server to com-
municate with the PLC machine controller
During operation, image acquisition
and part handling are tightly synchronized.
Encoder feedback from the PLC to the iPCs
triggers each camera array to acquire images
every 7. 5 mm of travel, as the package passes
overhead and high- and low-angle lights are
This creates sequential, but overlapping
images, which are transferred via USB3 interface to the industrial PCs, where they are
stitched together, reconstructing two images of
the 12 x 12-inch package with different lighting.
The image analysis soft ware uses various algorithms to perform certain vision tasks. One
identifies channels across the seal and another
looks for wrinkles in the Tyvek. There is an
algorithm that measures the width of the seal
along the entire perimeter of each item and
ensures that it doesn’t fall below a specific
minimum to identify areas of the seal that
may be too narrow.
Other algorithms are applied to the images
to detect particulates captured inside the seal,
wrinkles in the Tyvek lidding, spoiled seals,
glazed seals, and to locate any holes or punc-
Figure 1: The DWFritz automated seal inspection system inspects all sides of the seal by drawing
in packages on an automated conveyor. A specially designed vacuum chuck, capable of picking
up even porous packages then moves the packages over several rows of upward-facing cameras.
Figure 2: Tyvek lidding sealed onto a 12 x 12 inch, eight-pouch array of flexible polyethylene
hermetically seals medical devices up to 2-inches high. Custom illumination was required to
properly illuminate the seal areas, shown in tan, to detect defects down to less than 50 microns.