Introduction
The geometric calibration of a camera (1.) consists in determining the existing mathematical relation between the coordinates of 3D points and the coordinates in 2D of their projection in the image (image point) (see Figure 1). This step of calibration is the initial point for several applications of Artificial Vision, such as the recognition and the location of objects, the control procedure for the dimensional measurement of cast parts, the reconstruction of the environment for a mobile robot navigation, etc.
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The calibration of a camera is particularly important when you want to obtain metric information, for the application of dimensional measurements, from acquired images.To obtain precise dimensional measurements, it is essential to take into account the geometric distortions induced by the optical system used.
The calibration of a camera involves choosing a model of camera a priori and then determining parameters of this model.
We will describe the main models of cameras used as well as the main methods developed in order to help determining the parameters of the model chosen.
To obtain tridimensional information, it is necessary to combine two cameras in order to constitute a sensor for stereoscopic vision. The calibration of such a sensor is a specific issue that is to be described too.