Hardware manual

Line Find Impact Reference Guide
Datalogic Automation Inc. 3-78
Above is an example of an image after the tool has run (some features have been removed in each example
for clarity). The magenta dots are the edge points, the yellow dots are the outlier edge points, and the green
line is an output that lies on the fitted line and extends from the first fitted point to the last fitted point, as
they are projected to the fitted line. The output origin is centered on the fitted line and at the same angle.
When the tool runs it performs the following operations:
1. Runs an Edge Point Find tool algorithm on each row of the wide line ROI and then does a linear
regression on the points that are found.
2. For Dark Line type it finds the First Falling edge. For Bright Line type it finds the First Rising edge.
For Center of Dark Line type it finds the strongest Falling/Rising pair. For Center of Bright Line type
it finds the strongest Rising/Falling pair.
3. The regression algorithm fits all the found edge points to a line and then iteratively reduces the
weights of points outside the Outlier Distance Threshold. For Center type finds, it fits the rising points
to one line and the falling points to another and then averages the two lines to create the output Line
Segment.
4. The output Line Segment and Gaps are found by projecting the non-outlier points to the fitted line and
sorting along the line. The output line segment extends from the first to the last points on the fitted
line. The gaps are the distance between adjacent points on the fitted line.
5. The output Origin is centered on the output Line Segment. The Origin is displayed only when the Dis-
play Output Origin check box in the Setup Pass/Fail panel is checked.
6. The Straightness Error is the average error of all the non-outlier points.
Edge Detection Method
Gradient Edges: Grey Levels in an image range from 0 to 100 percent (0 to 255 grey levels). A gradient
indicates a rate of change. When you choose this setting, the tool compares the value of each pixel along the
edge to its neighbor. A greater value indicates a positive gradient (dark to bright). A lesser value indicates a
negative gradient (bright to dark). The difference between the two values indicates the steepness of the gra-
dient (no difference indicates no gradient). The Fixed Gradient Threshold Percentage or Edge Detection
Sensitivity input property determines the minimum steepness of the edge the tool should find. A larger
threshold number or higher sensitivity means the tool only finds edges with a steeper gradient. In some cases
Gradient Edge detection can find extra edges in the flat parts of a noisy image where Grey Level detection
offers better control. However, if there is extra noise in the edge you are trying to find, this method probably
provides more consistent results.
Grey Level Edges: Grey Levels in an image range from 0 to 100 percent (0 to 255 grey levels). When you
choose this setting, the tool measures the grey level of each pixel along the edge. The Fixed Grey Level
Threshold Percentage or Edge Detection Sensitivity input property determines the grey level value at which
edges are found. For example, if one pixel’s grey level is less than the threshold and the next pixel’s grey
level is greater than the threshold, then a rising edge is detected. The threshold value is related to the differ-
ence in brightness or darkness of the object rather than the steepness of the edge. This setting works some-
Gradient
Thresholds
Rising Gradient
Edge Found
Falling Edge
Not Found
Image edges