In the sheet of light (triangulation) method, a laser beam is directed via a line lens onto the surface of the object to be measured. With the help of a C3 camera, a picture of the laser line is acquired from the triangulation angle alpha. As a result of the triangulation arrangement of the laser and the camera, any change in the surface make-up below the laser line will lead to the laser line in the camera image being displaced in a defined manner. The task of a C3 camera is to use maximum speed and precision to determine the position of the laser line.
Below, you will see a number of typical laser-scanning arrangements. For the approximation of the height resolution data that has been given, the following symbols have been used:
dX= resolution along the laser line, dY= resolution perpendicular to the laser line (in the direction in which the object or the camera moves), dZ= resolution in the direction of height.
Arrangement 1
The laser is perpendicular to the surface and the camera is rotated around the triangulation angle a. Height resolution can be approximated at:
dZ = dX / sin(alpha)
Arrangement 2
The laser is perpendicular to the surface and the laser is rotated around the triangulation angle a. Height resolution can be approximated at:
dZ = dX / tan(alpha).
Arrangement 3
The camera is rotated around angle a to the surface normal line and the laser rotated around angle ß opposite to the surface normal line.
Height resolution can be approximated at: dZ = dX * cos(beta) / sin(alpha + beta), if alpha=beta (specular reflex) then the approximation is simplified at: dZ = dX / 2*sin(alpha)
