Extra calibration sheets
Description of dot-grid calibration sheets and the calibration process.
For the TAGARNO measurement software MICRO we use an advanced calibration. This is a well proven technique from an international recognized Machine Vision Software and based on advanced algorithms in order to ensure an extremely high accuracy. The advanced, automatic calibration of the MICRO software compensates for lens curve distortion and nonlinearity, after which the software behind will carry out calculations with a precision of sub-pixels.
The MICRO calibration uses some predefined dot-grid calibration sheets printed with very high accuracy by a professional offset printing machine (more than 250lpi).
The technique of using dot-grid sheets for calibration is very effective and only need one image to make the calibration. This is assumed to be analogous to use the centroid of a circular dot. The dot center will move very little with camera blooming and defocusing or even bad printing quality is less significant.
It is important to mention that calibration with more than a +10 lens is not possible.
Compared to other well known calibration methods like checkerboard calibration is the dot-grid very reliable. The checkerboard calibration will often fail if one of the edges is not recognized, and because this method need to find the corners this is more sensitive to camera blooming or defocusing.
