Structured Light Algorithm for Low 3D Measurement Error at Long Distances

The 3D acquisition of an indoor scene with colorimetric information is currently achieved by vision systems using structured light. The existing solutions are specific to small scenes at short distances. In the case of larger scenes where the vision system is far from the analysed objects, i.e. more than 4 m from the acquisition system, the solutions do not enable scene acquisition with a measurement error of the order of a millimetre. From existing algorithms in the literature, the method, Bi-Frequency and Gray Code Phase Shifting (B-GCPS) combining two structured light algorithms is proposed. The main idea consists in using several reference planes to minimize the measurement error. Our method uses the Gray Code + Phase Shifting (GC+PS) algorithm to assist in the acquisition of reference planes and the selection of the most relevant ones. Then, the Bi-frequency algorithm estimates the 3D coordinates of the scene with a very low measurement error, thanks to different reference planes acquired previously. With the proposed method, the acquisition of long distances scenes higher than 2 m in width and length is possible, with a very low measurement error. This method reduces the measurement error on the 3 axes (X, Y, Z) by at least 400, in the order of a millimetre.