Change in Number of the Ghost Points with the Distance between the two Parallel Surfaces

Abstract

The beam size of the laser scanner is one of the factors to be considered in measurement planning. However, the catalog specifications usually provide only the spot diameter at a specific distance. Therefore, it is necessary to be able to estimate the spot diameter at arbitrary measurement distances. To provide the spot diameter at arbitrary distances, we have measured the spot size using a target with a circular hole. This target consists of two flat surfaces with a circular hole in the front surface. By scanning this target, the spot diameter is estimated based on the number of ghosts which appear at the hole edge. In this study, we investigated how the number of ghosts change according to the distance between these two surfaces. As a result, we found that the number of ghosts was maximum and most stable at the gap of 41mm. This indicates that there exists an optimal surface gap for each scanner.