Correction Methods of Near-Zero Step Error in Phase Laser Ranging

Multi-ruler is an effective way to improve the measuring range and precision in phase laser range finder. But the fine-ruler´s phase will fold and blur sometimes, then near-zero step error (NZSE) may appear under the influence of noise. This paper has analyzed the relationship between NZSE, integer-ruler and residual-ruler, and proposed two phase correction methods which are based on integer-ruler and residual-ruler respectively to eliminate the NZSE. The presented methods have been simulated under different conditions in Matlab. The results show that the phase correction method based on integer-ruler can completely eliminate the step errors when distance changes slowly. The method based on residual-ruler not only has the same correction ability as the former method, but also can eliminate the step errors even when the distance changes with very large interval.