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ScanMultipleRidges

Basic

Module: MetrologyBasic

Locates multiple dark or bright pixel peaks along a given path (without a scan map).

Applications

Very fast detection of multiple thin structures like wires or scale marks - usually for counting or distance 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
 inRidgeScanParams RidgeScanParams Parameters controlling the ridge extraction process
Input value
 inMinDistance Real 0.0 - Minimal distance between consecutive ridges
Input value
 inMaxDistance Real* 0.0 - Maximal distance between consecutive ridges
Input value
 inLocalBlindness LocalBlindness* Defines conditions in which weaker ridges can be detected in the vicinity of stronger ridges
Output value
 outRidges Ridge1DArray Found ridges
Output value
 outGaps Gap1DArray Gaps between consecutive ridges
Output value
 outAlignedScanPath Path Transformed input path
Output value
 outBrightnessProfile Profile Extracted image profile
Output value
 outResponseProfile Profile Profile of the ridge 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 ridges. Depending on the inRidgeScanParams.ridgePolarity parameter, dark, bright or both ridges will be taken into account.

When the number of ridges to be measured is known, one can use the ScanExactlyNRidges 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 ridges you want to detect. It should be long enough to anticipate all possible ridge locations.
  • Define inRidgeScanParams.RidgePolarity to detect a particular ridge 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 inRidgeScanParams.SmoothingStdDev.
  • If too few ridges are found, try decreasing inRidgeScanParams.MinMagnitude. Verify this with the values on the outResponseProfile output.
  • If consecutive ridges are very close to each other, change inRidgeScanParams.ProfileInterpolation to Quadratic3.
  • Adjust inMinDistance (in pixels) to filter out false ridges that appear in proximity to other ridges.

Examples

ScanMultipleRidges locates the ridges across inScanPath.

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 ScanRidges filter group.

See Also

  • ScanSingleRidge – Locates the strongest dark or bright pixel peak along a given path (without a scan map).
  • ScanExactlyNRidges – Locates a specified number of the strongest dark or bright pixel peak along a given path (without a scan map).
  • ScanMultipleRidges – Locates multiple dark or bright pixel peaks along a given path (without a scan map).