DMC’s system utilized NI hardware to integrate with the existing Delta Tau Motion Controller. The NI cRIO was used to determine pill presence, track pill results from the EVS, and output results to the Delta Tau Motion Controller in order to reject bad tablets. The NI EVS triggers the cameras and lights, acquires images, runs inspection algorithms, and outputs a result to the cRIO. Each camera views two tablets, so pass-fail results are determined for 16 tablets nearly simultaneously. The first step of the inspection algorithm is to separate the pills from the background, then each individual pill is analyzed using three algorithms:
- Check for bright spots within the interior of the tablet (the outside of the tablet is darker than the powdery inside of a broken tablet).
- Compare the perimeter of the tablet to the ideal perimeter of a known, good tablet. The perimeter comparison allows for rotated and flipped tablets. This check will reject broken tablets that don’t have any white powder visible to the camera.
- Check the gradient of pixel brightness a few pixels inside the perimeter of the tablet. This check finds hairline cracks that are not large enough to be detected as a contiguous blob of brightness.
The results are tracked in the cRIO until the pills reach the rejection point on the machine, at which point the results are sent to the Delta Tau controller and the bad pills are blown into a reject container.