Fraunhofer Institute of Optronics, System Technologies and Image Exploitation IOSB 
3D sensors in the production process
From laser scanners to stereo cameras, there is a steadily growing range of optronic distance-measuring sensors and sensor concepts with very different (physical) properties. They enable the non-contact detection and measurement of the three-dimensional shape, size, and position of objects. Such sensors can be integrated into production lines for a wide variety of tasks, such as process monitoring or the inspection of workpieces.
Laser line triangulation
Laser line triangulation enables relatively low system costs while providing millimeter- to submillimeter-accurate three-dimensional object measurement in a continuous process. However, when measuring large objects, the greatest challenge lies in ensuring the stability of the calibration of the sensor components relative to one another and in the registration of the scanning process.
A sensor system that meets these requirements can also measure large workpieces (e.g., vehicle bodies) in-process while they are already on a conveyor system due to production requirements.
The concept of self-calibration
The self-calibration concept developed at Fraunhofer IOSB—for which a patent has been filed—solves the aforementioned problems for a triangulation system. It rejects the idea of a mechanically rigid overall assembly requiring initial calibration. The triangulation modules are also broken down into their individual components: a line laser and a triangulation camera. Each of these components is equipped with an additional so-called pose camera. It is optimized to determine the position and orientation of the respective component within the coordinate system of the object being measured. This approach addresses mechanical instabilities of the component mounts and fastenings as well as the relative scanning motion between the object and the sensors. For each individual data acquisition, a 3D profile can be calculated based on the exact orientation of the laser plane and the triangulation camera in the object coordinate system at that precise moment.