IMAQ Find Circular Edge VI

LabView NI Vision

IMAQ Find Circular Edge VI

Owning Palette: Locate EdgesInstalled With: NI Vision Development Module

Locates a circular edge in a search area. This VI locates the intersection points between a set of search lines defined by a spoke and the edge of an object. The intersection points are determined based on their contrast and slope.

Details Examples

IMAQ Find Circular Edge

Settings is a cluster defining the parameters of the edge detection algorithm and the information that is overlaid on the result image. The first three parameters specify the filter used to detect the edges.

	Contrast specifies the threshold for the contrast of the edge. Only edges with a contrast greater than this value are used in the detection process. Contrast is defined as the difference between the average pixel intensity before the edge and the average pixel intensity after the edge.
	Filter width specifies the number of pixels that the VI averages to find the contrast at either side of the edge.
	Steepness specifies the slope of the edge. This value represents the number of pixels that correspond to the transition area of the edge.
	Subsampling Ratio specifies the number of degrees that separates two consecutive search lines of the spoke.
	Scan Direction specifies the direction in which the search lines are scanned for edges. The default value is Outside to Inside, from outside of the annulus to inside the annulus.
	Show Search Area determines whether the search area is overlaid on the image.
	Show Search Lines determines whether the search lines used to locate the edges are overlaid on the image.
	Show Edges Found determines whether the locations of the edges found are overlaid on the result image.
	Show Result determines whether the edges used in the best-fit line calculation are overlaid on the result image.

Image is a reference to the source image.

Circle or Annulus specifies a circular search area.

	Center X specifies the x-coordinate of the center of the circle or annulus.
	Center Y specifies the y-coordinate of the center of the circle or annulus.
	Inner Radius is the radius (in pixels) of the inner circle defining one edge of the circular strip.
	Outer Radius is the radius (in pixels) of the outer circle defining the second edge of the circular strip.
	Start Angle is the first angle of the circular strip. The angle is measured counterclockwise from the x-axis of a coordinate system centered on the center of the circle or annulus.
	End Angle is the second angle of the circular strip. The angle is measured counterclockwise from the x-axis of a coordinate system centered on the center of the circle or annulus.

Coordinate System specifies the coordinate system to which the Annulus is linked. If the Coordinate System input is used (connected), the annular search area is shifted and rotated by the difference between the reference position of the coordinate system and its new location.

error in (no error) describes the error status before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.

	status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE.
	code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.
	source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.

Edge Coordinates is an array of point clusters consisting of the spatial coordinates of the detected edges.

Image Out is a reference to the destination image. The search area and/or the result of the measurement may be overlaid on the image according to the settings.

Best Circle returns in a cluster the center point of the best-fit circle as well as its radius.

Coordinate System (duplicate) is a reference to the coordinate system.

error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out indicator on the front panel and select Explain Error from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.
	code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.
	source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.

Roundness returns the roundness of the circular edge detected. This calculation is based on the location of the edges detected.

Details

A best-fit circle is calculated through the points found. The VI returns the coordinates of the circle found as well as its roundness. IMAQ Find Circular Edge can overlay results on the image returned: the position of the search area, the search lines, the edges found, and the result circle.

Examples

Refer to the following for an example that uses this VI.

LabVIEW\examples\Vision\3. Applications\Battery Clamp Inspection Example.vi

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