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ScanMultipleStripes

Basic

Module: MetrologyBasic

Locates multiple pairs of edges across a given path (without a scan map).

Applications

Very fast detection of multiple pairs of opposite edges - usually for counting or width measurements.
Name Type Range Description
Input value inImage Image Input image
Input value inScanPath Path Path along which the scan is performed
Input value inScanPathAlignment CoordinateSystem2D* Adjusts the scan path to the position of the inspected object
Input value inScanWidth Integer 1 - Width of the scan field in pixels
Input value inSamplingParams SamplingParams Parameters controlling the sampling process
Input value inStripeScanParams StripeScanParams Parameters controlling the stripe extraction process
Input value inMinGapWidth Real 0.0 - Minimal distance between consecutive stripes
Input value inMaxGapWidth Real* 0.0 - Maximal distance between consecutive stripes
Input value inLocalBlindness LocalBlindness* Defines conditions in which weaker edges can be detected in the vicinity of stronger edges
Output value outStripes Stripe1DArray Found stripes
Output value outGaps Gap1DArray Distances between consecutive stripes
Output value outAlignedScanPath Path Transformed input path
Output value outBrightnessProfile Profile Extracted image profile
Output value outResponseProfile Profile Profile of the edge (derivative) operator response
Diagnostic input diagSamplingPoints PathArray Array of paths each one containing the sampling points that contributes to a single value of the extracted profile
Diagnostic input diagSamplingStep Real Used distance between consecutive sampling points on the scan path

Description

The operation scans the image along inScanPath and detects consecutive stripes (i.e. pairs of opposite-polarity edges running across the path). Depending on the inStripeScanParams.stripePolarity parameter, dark or bright stripes will be taken into account.

When the number of edge pairs to be measured is known, one can use the ScanExactlyNStripes filter.

The optional parameter inScanPathAlignment defines a transform to be performed on the inScanPath so that the actual scan path (outAlignedScanPath) is adjusted to the position of the object, typically detected by one of Template Matching filters.

Note that in case of a scan path which is closed, the parameters controlling the distances between consecutive found objects do not control the distance between the first and the last of the found objects (counting from the beginning of the scan path).

Hints

  • Connect an input image to the inImage input.
  • Create inScanPath which is more or less perpendicular to the stripes you want to detect. It should be long enough to anticipate all possible stripe locations.
  • Define inStripeScanParams.StripePolarity to detect a particular edge type, and only that type.
  • Use a local coordinate system connected to inScanPathAlignment to automatically adjust the measurement to variable object position (optional).
  • If the noise level is high, try increasing inScanWidth and/or inStripeScanParams.SmoothingStdDev.
  • If too few stripes are found, try decreasing inStripeScanParams.MinMagnitude. Verify this with the values on the outResponseProfile output.
  • If consecutive edges are closer than 6 pixels apart, change inStripeScanParams.ProfileInterpolation to Quadratic3.
  • Adjust inMinGapWidth (in pixels) to filter out false stripes that appear in proximity to other edges.
  • Adjust inStripeScanParams.inMinStripeWidth and inStripeScanParams.inMaxStripeWidth (in pixels) to increase reliability.

Examples

Description of usage of this filter can be found in examples and tutorial: Bars, Parallel Enumeration, Bottle Inspector Part 1: Counting Bottles, Bottle Inspector Part 2: Measuring Liquid Level, Bottle Inspector Part 3: Foam Detection, Counting Saw Teeth.

ScanMultipleStripes locates the edge pairs across inScanPath (inStripeScanParams.stripePolarity = Dark, inStripeScanParams.minStripeWidth = 45).

Remarks

Read more about Local Coordinate Systems in Machine Vision Guide: Local Coordinate Systems.

This filter is a part of the 1D Edge Detection toolset. For a comprehensive introduction to this technique please refer to 1D Edge Detection and 1D Edge Detection - Subpixel Precision chapters of our Machine Vision Guide.

Complexity Level

This filter is available on Basic Complexity Level.

Filter Group

This filter is member of ScanStripes filter group.

See Also

  • ScanSingleStripe – Locates the strongest pair of edges across a given path (without a scan map).
  • ScanExactlyNStripes – Locates a specified number of multiple pairs of opposite edges across a given path (without a scan map).
  • ScanMultipleStripes – Locates multiple pairs of edges across a given path (without a scan map).