
Chapter 21 Vision Control (Option)
21-61
<Level> Designates the level to detect the edge (0 to 512).
<Mode> Designates the method for detecting the edge. If this is ignored, 0
will be the default setting.
0: Absolute value of average brightness
1: Difference value of the average brightness
2: Absolute value of the area
3: Difference value of the area
Brightness average value
Edge scanning direction
(White to black)
(Black to white)
Brightness
X Coordinate
Width 1 pixel
pixel
In this example, the edge is detected from left to right in
a rectangle window. The graph shows how the
brightness changes with the brightness average.
The window used is divided into units of 1 pixel, in the
edge scanning direction. Brightness average value:
n average value of one pixel obtained by dividing the
brightness value measured in each divided pixel windo
by the number of pixels (n pixels) in each window.
Specify the level value with the brightness average value
(0~255).
Coordinate X
X Coordinate
Brightness
Brightness
Edge scanning direction
Level
Level
Level
Black to white White to black
Black to white
White to black
Relation between Level and Edge
The graphs show the change in brightness in a window.
The detected edge position is points a and b where the
brightness passes a designated level in graph (1).
In graph (2), c is the point where the brightness reaebes the
designated level.
If the brightness does not reach the designated level, the edge
of black to white is detected.
If the brightness reaches a level higher than the designated
level, the edge of white to black is detected.
If the brightness changes from the same level as the
designated level to a lower level value, like point d shown in
graph (2), it is not detected as an edge.
Edge scanning direction
<Binary lower limit> Designates the lower level for binarization (0 to 254
lower limit < upper limit). The default is 0.
<Binary upper limit> Designates the upper level for binarization (1 to 255
lower limit < upper limit) The default is 255.
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