Rockwell Automation 48MS MultiSight Vision Sensor - Manual (Page 35)

MultiSight™ User Manual
Start-up
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Detector Types—Detailed Description
The following detector types are available: Pattern Matching, Brightness, and Contrast.
The EtherNet/IP model also has a Contour Matching detector type.
Pattern Matching
With this method, the detector looks for a pattern in a defined Region of Interest (ROI). By defining this ROI as larger than the
pattern there is some tolerance in positioning of the inspected part. The ROI is the yellow frame on the image and the pattern is
defined by the red frame. In run mode, the sensor evaluates the ROI on the current image to see if the pattern is present. The
evaluated pattern must match the taught pattern to a degree of conformity greater than the minimum threshold value (and less
than the maximum threshold value).
Example: The sensor is taught the following pattern:
In the next row of three patterns, each pattern is recognized with 100% conformity
because the evaluated pattern is exactly the same as the taught pattern even
though it is in a different position in the Region of Interest (ROI). It differs only in
direction X and Y and is not rotated.
In the next row of three patterns, each pattern is recognized but with less than
100% conformity. Pass or Fail result is dependant on the threshold settings (degree
of conformity).
Pattern detection is also tolerant of up to ± 5° of rotation. The next two images
would be recognized. Due to the slightly rotated orientation of the pattern, the
conformity would be less than 100% even though there is 100% pixel conformity.
(Patterns with more than 5° of rotation are not recognized.)
Brightness
The MultiSight uses an 8 bit grey-scale CCD chip to capture images. The chip assigns each pixel a value of 0 (black) to 255 (white).
The Brightness Detector Type evaluates all pixels that are darker than grey-scale value 128 as black. The detector examines the
Region of Interest (ROI) and determines the “Brightness” level (White = 100%, Black = 0%). If this level is between the configured
threshold minimum and maximum, the detector passes the evaluation.
The shutter speed has a significant effect on the number of pixels which are evaluated as black and thus which images pass or fail
this inspection.
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