InspectEdge

The InspectEdge function is used to perform advanced edge analysis. Within the function's referenced Region of Interest (ROI), an array of indexed, edge detecting sub-regions (called Calipers) develop detailed information about the precise location of features, by locating edges or edge pairs in an image. This information is used to determine the location of edges or features, the location and spacing of pairs of edges, and measure the width of objects in images.

InspectEdge Overview

After inserting the InspectEdge function, the ROI is established, either using the function's own internal region or as a reference to an external ROI, such as an EditMaskedRegion or EditPolylinePath, to determine where in the image the tool should detect the edge or edge pairs. For more information, see EditMaskedRegion or EditPolylinePath. The referenced ROI is segmented into individual Calipers, where each Caliper projects the pixels within it into a single convolution for edge analysis.

Once the ROI has been configured, the following steps are necessary to properly apply the function:

Specify Caliper, Minimum Contrast and Edge Width parameter values that isolate the edges of interest
Define an edge model that describe the edge or edge pair of interest using the InspectEdgeForDefect, InspectEdgePosition, and/or InspectEdgeWidth functions. For more information, see InspectEdgeForDefect, InspectEdgePosition, or InspectEdgeWidth.

With the InspectEdge function in place, multiple inspections can be performed using a single InspectEdge function as an input. For example, within one InspectEdge ROI, an InspectEdgeForDefect function could reference the function to determine positional defects, while an InspectEdgeWidth function performs a separate width measurement, and an InspectEdgePosition function determines a best-fit line for another edge.

Note: InspectEdge requires the longest execution time of the InspectEdge Vision Tools. Increasing the number of Calipers within the ROI will increase the function's computational time.

InspectEdge Inputs

Syntax: InspectEdge(Image,Fixture.Row,Fixture.Column,Fixture.Theta,Region.X,Region.Y,Region.High,Region.Wide,Region.Angle,Region.Curve,External Region or Path,Caliper.Height,Caliper.Repeat Offset,Caliper.Initial Offset,Minimum Contrast,Edge Width,Fit All Calipers,Caliper Graph Index,Polyline Width,Show)

Note: The Fixture and Region parameters must be defined within the bounds of the image; otherwise, the function will return #ERR.

Parameter

Description

Image

Specifies a reference to a spreadsheet cell that contains an Image data structure; by default, this parameter references A0, the cell containing the AcquireImage Image data structure. This parameter can also reference other Image data structures, such as those returned by the Vision Tool Image functions or Coordinate Transforms Functions.

Fixture

Defines the Region of Interest (ROI) relative to a Fixture input or the output of a Vision Tool function's image coordinate system. Setting the ROI relative to a Fixture ensures that if the Fixture is rotated or translated, the ROI will be rotated or translated in relation to the Fixture. For more information, see Fixture and Vision Tools Functions.

Note: The default setting is (0,0,0), the top leftmost corner of the image.

Row (default = 0)	The row offset, in image coordinates.
Column (default = 0)	The column offset, in image coordinates.
Theta (default = 0)	The angle of orientation, in the image coordinate system.

Region

Also known as the Region of Interest (ROI), specifies the region of the image that undergoes edge analysis; creates a rectangular image region that can be transformed and rotated. With this parameter selected, by pressing the Maximize Region button on the property sheet's toolbar, the region will automatically be stretched to cover the entire image. The dashed yellow line indicates the direction in which the edge will be found.

X	The x-offset of the origin, in fixture coordinates.
Y	The y-offset of the origin, in fixture coordinates.
High	The dimension along the region's x-axis.
Wide	The dimension along the region's y-axis.
Angle	The orientation, in fixture coordinates.
Curve	The angular deviation between the region's x-axis and the opposing boundary line.

External Region or Path

Specifies a reference to a spreadsheet cell that contains an Annulus, a Region, an EditAnnulus, an EditMaskedRegion, an EditPolylinePath or an EditRegion function. When this parameter is used, the function ignores the Region and Fixture settings and inspects the image area specified by the referenced region.

Note:

If this parameter has been set as a reference to an external region, to use the function's internal Region, this parameter must be manually set to zero by entering the value 0 in place of the cell reference. Otherwise, the function will continue to reference the external region.
If this parameter references an EditPolylinePath, the function cannot be used as a reference to the InspectEdgeForDefect or InspectEdgePosition functions, which will return #ERR.

Caliper

Specifies the Caliper array within the ROI that will be used to define the size of the detectable defects and/or gaps. The size of the detectable defect or gap is determined by the number of edges that can be detected, which is determined by the number of Calipers placed along the edge. The Calipers are displayed within the ROI as red rectangles, and edges detected within the Caliper are displayed in green, when the InspectEdge cell is highlighted or the Show parameter is set to show all.

Note: Depending on the type of defect being examined, Calipers may be positioned to overlap. However, the more Calipers that are applied within the ROI will increase the function's execution time.

Height	Specifies the number of pixels, per Caliper, that are to be analyzed along the direction of the inspection. The valid range is 1 to the In-Sight vision system's image width; default value is 5.
Repeat Offset	Specifies the number of pixels between the start of each Caliper. The valid range is 0 to the In-Sight vision system's image width; default value is 5. The last Caliper may overlap the end of the Region, unless Fit All Calipers is enabled.
Initial Offset	Specifies an offset for the first Caliper in the Region. The valid range is 0 to the In-Sight vision system's image width; default value is 0.

Minimum Contrast

Specifies the minimum greyscale contrast transition (0 to 255; default = 5) to be considered an edge. For each indexed Caliper, a contrast graph, drawn in blue, is displayed on the image. The values in the chart are automatically scaled to a 0-100 value. Utilize this chart when applying this parameter to properly adjust the value.

Edge Width

Specifies the pixel distance (1 to the Region width value; default = 3) over which an edge transition takes place. This setting is the approximate size of the pixel operator used to filter the greyscale projections before edges are extracted; use this setting to filter noise from the image.

Fit All Calipers

Specifies whether or not all of the Calipers are placed within the ROI.

0 = OFF (default)	Specifies that the function strictly adheres to the Caliper Repeat Offset and Initial Offset parameters, and Calipers may overhang the ROI.
1 = ON	Specifies that the function will automatically re-calculate the Caliper Repeat Offset and Initial Offset parameters to ensure that all of the Calipers are placed within the ROI.

Caliper Graph Index

Specifies the Caliper to be displayed on the image (the Caliper will be outlined in green); default Caliper displayed is 0.

Polyline Width

Specifies the height (1 to Region height value; default = 20) of an EditPolylinePath.

Show

Specifies the display mode for InspectEdge graphical overlays on top of the image.

0 = hide all (default)	All graphics will be hidden, except when the cell containing the InspectEdge function is highlighted in the spreadsheet.
1 = result graphics only	The Caliper graph and specified Caliper will be displayed at all times.
2 = input and result graphics	The input image region, the Caliper graph and specified Caliper will be displayed at all times.
3 = show all: input, result, and calipers	The input image region, the Caliper graph and all of the Calipers within the ROI will be displayed at all times.

InspectEdge Outputs

Returns	An Inspect data structure containing the detected edges in the image and the number of Calipers, or #ERR if any of the input parameters are invalid.
Results	The number of Calipers in the ROI.