Symmetrical circles pattern

A symmetrical circle pattern is composed of circles that are arranged evenly in rows and columns.

Other supported patterns with circles are asymmetric circle pattern and individual circle pattern.

Requirements for the pattern

• The pattern should be applied to a surface that is as flat as possible (planar), e.g. a glass pane.
• The circles should be as equal in size as possible.
• A sample must consist of at least 9 points.
• The circle centers must be applied at the same distance horizontally and vertically. The distance must be large enough to ensure that the circles do not touch each other and are recognized as separate objects.
• The background color around the pattern must form a 'quiet zone'.

Requirements for the image acquisition

• Exposure
• Homogeneous illumination of the pattern.
• Good contrast between circles and background.
• Figure
• Perspective distortions should be kept to a minimum.
• The standard specifications of the Advanced Calibration Options must be adhered to or adapted. By default, a circle must be represented by an area of at least 25 pixels and a maximum of 15000 pixels. The area should not be too small, otherwise interference from the background will be picked up.

Configuration in the Camera Calibration Assistant

• Width
  Corresponds to the number of circles per row.
• Height
  Corresponds to the number of circles per column.
• Distance x
  Corresponds to the distance between two circle centers in horizontal direction.
• Distance y
  Corresponds to the distance between two circle centers in vertical direction.



• Color inverted
  By default, dark circles on a light background are assumed. If the pattern instead consists of light circles on a dark background, the colors can be inverted with Color inverted option.