During measurement the touch trigger probe
contacts the object surface to be measured and the image of the
light sources on light pen is captured by the CCD camera. The
image is processed by the computer and 3D coordinates of the
contact point can be calculated with a predefined algorithm. In
this way, coordinates of all points are sampled in turn. The
geometrical features such as the dimensions, forms and
position errors of the objects are evaluated by the software
package based on the obtained 3D coordinates.