create_bead_inspection_model — Create a model to inspect beads or adhesive in images.
create_bead_inspection_model creates a model to inspect beads or adhesive in images.
The basic principle of bead inspection
The bead inspection operators enable the user to define a reference contour that indicates the position and shape of a bead or adhesive on a certain product. Images of such products can then be inspected to verify that a bead or adhesive exists at the positions defined by the contour and that it is of acceptable thickness. The images must already be aligned with the given contour.
The operator create_bead_inspection_model returns a handle to the bead inspection model in BeadInspectionModel, which can later be used to perform other operations related to bead inspection. These operations include the modification of the bead inspection model parameters and performing the inspection on input images as defined by the model.
Providing the model contour
In order to inspect beads, a contour serving as the model for the bead must be provided in BeadContour. Such a contour can be generated, e.g., by using the operators gen_contour_polygon_xld or gen_contour_nurbs_xld. The contour must be defined to be aligned to the beads in the input images. To achieve this, the user can draw the XLD directly on a reference image in the graphics window (with draw_polygon or draw_nurbs). To inspect beads consisting of multiple parts, multiple models must be created.
In order to inspect beads, the following parameters must be set:
- TargetThickness: defines the optimal bead thickness in pixels.
- ThicknessTolerance: defines the tolerance to the bead's thickness in pixels. The bead is accepted if its thickness is within the range:
- PositionTolerance: defines the tolerance to the bead's position in pixels. The 'bead position' is the center of the detected bead. The bead is accepted if the distance between its center and the contour's position is less than the PositionTolerance.
- Polarity: defines the polarity of the bead in the images to inspect. 'light' if the bead is lighter than its background, 'dark' otherwise.
Edge extraction parameters
Bead inspection relies on edge extraction to identify the edges of beads. Accordingly, correct initialization of the measure_pos parameters helps improve bead inspection results. In particular, the following 2 parameters are included as generic parameters in the bead inspection model:
As defined in measure_pos, 'sigma' is the standard deviation of the Gaussian smoothing kernel. The value of 'sigma' depends on the quality of the images to be inspected, namely on the amount of noise. 'sigma' is set to 2.0 by default.
As defined in measure_pos, 'threshold' sets the minimum edge amplitude to be extracted. Setting a higher value for 'threshold' helps to avoid the extraction of noise edges and select salient edges. 'threshold' cannot be less than 1 and is set to 30 by default.
The Measure Assistant can be used to find suitable values for these two parameters.
Free the bead inspection model
Since memory is allocated for the model during the call of the operator create_bead_inspection_model and during the following operations, the model should be freed explicitly by the operator clear_bead_inspection_model as soon as it is no longer used.
This operator returns a handle. Note that the state of an instance of this handle type may be changed by specific operators even though the handle is used as an input parameter by those operators.
This operator modifies the state of the following input parameter:
XLD contour specifying the expected bead's shape and position.
Optimal bead thickness.
Default value: 50
Typical range of values: 5 ≤ TargetThickness
Tolerance of bead's thickness with respect to TargetThickness.
Default value: 15
Typical range of values: 0 ≤ ThicknessTolerance
Tolerance of the bead's center position.
Default value: 15
Typical range of values: 0 ≤ PositionTolerance
The bead's polarity.
Default value: 'light'
List of values: 'dark', 'light'
Names of the generic parameters that can be adjusted for the bead inspection model.
Default value: 
List of values: 'sigma', 'threshold'
Values of the generic parameters that can be adjusted for the bead inspection model.
Default value: 
Suggested values: 0.6, 1.0, 4.0, 5.0, 10.0, 50.0
Handle for using and accessing the bead inspection model.
* Read the image of the bead to be inspected. read_image (Image, 'bead/adhesive_bead_01') * Define the reference path of the adhesive beads. gen_contour_nurbs_xld (ContourRef, \ [610.974,533.443,461.763,393.009,330.106,287.683, \ 270.129,265.74,265.74,300.849,331.569,376.917, \ 438.357,489.557,539.294], \ [418.581,424.27,439.441,473.574,526.67,574.078, \ 644.241,708.715,765.604,818.7,866.107,915.411, \ 966.611,998.848,993.159], \ 'auto', \ [15,15,15,15,15,15,15,15,15,15,15,15,15,15,15], \ 3, 1, 5) * * Create the bead inspection model, identifying the bead's parameters create_bead_inspection_model (ContourRef, 14, 7, 30, 'dark', , , \ BeadInspectionModel) * * Apply the bead inspection model to the image apply_bead_inspection_model (Image, LeftContour, RightContour, \ ErrorSegment, BeadInspectionModel, \ ErrorType)
The operator create_bead_inspection_model returns the value 2 (H_MSG_TRUE) if the given parameters are valid and within acceptable range. Otherwise, an exception will be raised.