IMAQ Caliper Tool VI

LabView NI Vision

IMAQ Caliper Tool VI

Owning Palette: CaliperInstalled With: NI Vision Development Module

Finds edge pairs along a specified path in the image. This VI performs an edge extraction and finds edge pairs based on specified criteria such as the distance between the leading and trailing edges and edge polarity.

IMAQ Caliper Tool

Edge Parameters is a cluster defining the characteristics of the filter used to detect the edges. This cluster consists of the following parameters:

	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.

Image is a reference to the source image.

Pixel Coordinates is an array containing the coordinates of the pixels to inspect. You can obtain the pixel coordinates from an ROI descriptor using the IMAQ ROIProfile VI.

SubPixel Information is a cluster containing the following parameters for subpixel analysis:

SubPixel Accuracy specifies the number of samples to obtain from a pixel. For example, a subpixel accuracy of One Fourth specifies that each pixel is split into four subpixels.

Interpolation Type specifies the method used to perform the interpolation. The following values are valid:

Quadratic (1)	Uses the quadratic formula to compute the pixel location
Cubic Spline (2)	Uses cubic splines to compute the pixel 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.

Caliper Parameters specifies the following parameters for finding edge pairs:

Polarity specifies the polarity of the leading and trailing edge in the search process. The following values are possible:

None (0)	Polarity of the edges is ignored.
Dark-Light (1)	The leading edge has a dark-to-light polarity, and the trailing edge has a light-to-dark polarity.
Light-Dark (2)	The leading edge has a light-to-dark polarity, and the trailing edge has a dark-to-light polarity.
Dark-Dark (3)	The leading edge has a dark-to-light polarity, and the trailing edge has a dark-to-light polarity.
Light-Light (4)	The leading edge has a light-to-dark polarity, and the trailing edge has a light-to-dark polarity.

Separation Separation specifies the desired distance between the leading and trailing edges of an edge pair. Edge pairs with separation distance outside the range [Separation – Separation Dev., Separation + Separation Dev.] are ignored. If you set this parameter to 0, this VI finds all edge pairs.

Separation Dev. specifies a tolerance value for the separation between the edges. This value influences the score of the detected edge pairs.

Caliper Report is an array of clusters that contain the following information about the detected edge pairs:

	Edge1 Position is the location of the leading edge.
	Edge1 Contrast is the contrast of the leading edge.
	Edge2 Position is the location of the trailing edge.
	Edge2 Contrast is the contrast of the trailing edge.
	Separation is the computed distance in pixels between the edges in the edge pair.
	Score is unused.

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

Number of Edge Pairs returns the number of detected edge pairs.

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.

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