Most of 3D profilometry devices are based on optical triangulation:
a light ray is projected onto a target, and its image is acquired by an imaging device. The angle between the imaging device and the light source is known, and therefore is possible to infer the object shape, as explained hereafter.

The functioning principle of a laser scanning system is illustrated in the figure on the right:
the light emitted by the laser falls over the object and generates a profile, which is acquired by a CCD camera.
Several parallel profiles are acquired by scanning the object, and in this way the necessary information to achieve the 3D model, is gathered.
The profile point spatial position is obtained by triangulation, knowing all the geometrical parameters (i.e. relative positions of laser source, CCD camera and investigated object).