Calibration for Laser Scanners Based on the NIM 80m Indoor Ranging Facility

Laser scanners have become very popular means of point clouds acquisition and 3D reconstruction. However, the accuracy specifications given by laser scanner producers in their publications and pamphlets are not consistent. Experience shows that sometimes these should not be trusted. Therefore, how to reasonably evaluate and quantify main technical parameters of the instruments is particularly important. It is very necessary to investigate in calibration devices and methods that are suitable for laser scanners. The 80m indoor ranging facility of the National Institute of Metrology (NIM) at Beijing, China, is equipped with an interferometer comparator, precise air flotation rail systems and environmental parameter automatical compensation system. The facility is a closed loop feedback control system and can provide a high-precision reference distance value with different intervals. A expanded standard uncertainty (k=2) of U(Ls) is superior to 0.5μm+0.5×10-6L. This paper describes the calibration principle and procedure, including mounting white standard spheres with surfaces of diffuse reflection at the mobile platform as non-contact targets, scanning and measuring the white spheres , fitting the coordinates of the sphere centers and calculating the relative distance among sphere centers. As an example, this paper also presents analysis and evaluation on the measurement uncertainty of ranging accuracy.