Setup

These controls let you manipulate the calibrator images:

• Get current as new - extract the current Scorpion image to a new tab
• Get current - extract the current Scorpion image, replacing any showing
• Save - save current image to file
• Load as new - load an image from file to a new tab
• Load - load an image from file, replacing any showing
• New - add new, empty tab
• Delete - delete current tab

Each tab has an icon attached - these icons convey the status of the image:

• - Image is active and enough corners have been located
• - Image is active and enough corners have been located. Image is the reference pose image
• - Image is active, but has failed location of enough corners
• - Image is inactive

These controls let you tune the calibration process:

• Image is active - when unchecked, the currently shown image is not part of the calibration process.
• Image is reference - one of the images must define the reference pose of the object
• Set origin - for the reference image, you can Ctrl-click in the vicinity of a corner and press this button. This will set the object reference system origin.
• Pick points - when exactly four points are Ctrl-clicked in the image, use this button to define the rectangle surrounding the squares to be used for calibration. This action also initiates a Compute.
• Unpick points - reverse the pick points process, returning the four corners as editable markers in the image
• Compute - apply a set of linefinders to count the number of squares within the picked rectangle, and then locate as many corners as possible
• Compute all - repeat the compute process for all active images
• Show counting details - display edge points and lines resulting from the square counting process
• Show corner details - display edge points and lines resulting from the corner detection process
• Show tracelines - also show tracelines from either of the above two options

These controls describe the object and algorithm:

• Grid size odd - size of squares 1, 3, 5 etc. in the grid *
• Grid size even - size of squares 2, 4 etc. in the grid *
• Unit - object size unit. Usually mm or in
• Focal model - the camera model (intrinsic parameters):
  • F32 - Full focal model: rectangular pixels, skew
  • F22 - Rectangular pixel model, no skew
  • F12 - Square pixel model, no skew
• Distort model - the lens distortion model:
  • D32 - 3 radial and 2 tangential distortion parameters
  • D22 - 2 radial and 2 tangential distortion parameters
  • D30 - 3 radial distortion parameters
  • D20 - 2 radial distortion parameters
  • D1 - Fast distortion model, single radial parameter

These controls are for information only:

• Show residuals - after calibration, each corner has a residual error. This is displayed as an arrow
• Gain - size (gain) of these arrows (Press Calibrate to redisplay.)
• Rows - number of grid rows found
• Cols - number of grid columns found
• Found xx/xx - number of corners found/number of corners present in grid
• Status - OK or Fail. Each image has its own status

These controls are for the calibration itself:

• Calibrate - do the full calibration based on the images and settings
• Calibrated/Not calibrated - the current status for the calibrator

When calibration is successful, the word Calibrated and a green tickmark appears below all controls.

A number of messages will appear to the left of the Calibrated/Not calibrated message. These messages indicate e.g. calibration success/failure, and other messages appear when needed.

Lens correction

This tab displays an informational view of the distortion corrections. the set of arrows displays the inverse distortion, i.e. the correction applied at each point to remove the lens distortion. The gain field sets the length of the displayed arrows. (Press Calibrate to recalculate.)

Advanced

These are purely informational parameters that are stored with the calibrator model.

• Focal distance - camera setting
• Iris - camera setting
• CCD pixel (um) - CCD pixel (vertical) size. This is also used to calculate the lens' focal length

3D axis size

• Axis visualization length - size of the displayed arrows for the reference system.

Tracelines

These settings are used for the linefinders that count the squares in the image, and those that find the corners within the image, respectively:

Counting rectangles

This works by creating tracelines between your four marked corner points. The lines thus found are used to count the number of transitions between the corners, and to more accurately position the corners themselves.

• Trace comb start/end - width of the trace comb, in pixels, on the outside/inside of the corner points
• Trace line count - number of trace lines
• Trace line elongation - extra length of the tracelines outside each corner point
• Line width - width in pixels of each trace line
• Sample step - interval in pixels between each sample
• Smooth base - smooth filter length
• Smooth counter - smooth filter count
• Percent threshold - if checked, calculate threshold dynamically
• Min threshold - minimum dynamic threshold, or manual threshold
• Fit tolerance - max distance from edgepoint, in pixels, for line fit
• Minimum number of points - minimum count to define a line

Finding cormers

This is done by applying a linear model (perspective) based on the four corners found above, and looking for edges near where the linear model postulates they should be.

• Trace comb width/length - width and length of each trace comb, respectively
• Trace line distance - distance in pixels between each traceline
• Line width - width in pixels of each trace line
• Sample step - interval in pixels between each sample
• Smooth base - smooth filter length
• Smooth counter - smooth filter count
• Percent threshold - if checked, calculate threshold dynamically
• Min threshold - minimum dynamic threshold, or manual threshold
• Fit tolerance - max distance from edgepoint, in pixels, for line fit
• Minimum number of points - minimum count to define a line