Panasonic PV500 User Manual page 177

How to read a graph when setting a threshold
Pointing the cursor to "Edge Threshold" displays the graph of differentials of edges.
Decide the appropriate threshold referring to the detection result and differential of each cell in "Cell Result"
and this graph.
Vertical axis: It indicates differential. When Edge Condition is "Both", it is -255 to 255. When
"Light->Dark", 0 to -255. When "Dark->Light", 0 to 255.
Red line:
It indicates threshold.
When "Edge Condition" is set to "Dark->Light", the edges with the differentials over the red
line that is drawn above Differential 0 are detected.
When "Edge Condition" is set to "Light->Dark", the edges with the differentials below the
red line that is drawn under Differential 0 are detected.
When "Edge Condition" is set to "Both", the two lines are displayed.
Light blue line: It indicates the average of differential.
When Edge Condition is "Both", the both averages of the detected edges for
"Light->Dark" and edges for "Dark->Light" are displayed.
Refer to "About Graph" (p.170) for the details of marks and items other than those above.
Setting Virtual Circle Detect Condition
Set the method for detecting a virtual circle. Set
"Detection Method", "Edge ratio used" and
"Execution Mode".
1.
Select "Virtual Circle Detect Condition" ".
> "Detection Method".
"Detection Method" is a parameter to decide
whether or not to use all the edge coordinates
detected by each cell for calculating a virtual
circle.
General Mode:
Detects a virtual circle using all edge coordinates. However, as the figure on the right, if the edge
coordinates of projections are also used for detecting a virtual circle, the center of the virtual circle may
shift.
Details Mode (Default):
When an object has projections or concave surface, using this mode enables those edge coordinates not
to use for calculating a virtual circle.
First, detects a virtual circle using all the edge coordinates, and then detects the final virtual circle only
using the edge coordinates in "Edge ratio used" from those with a smaller error for the first virtual circle.
Select "Details Mode" to set "Edge ratio used".
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