In situ monitoring of object beam expander noise in speckle correlation interferometry

Abstract

Expanded beams used for object illumination in industrial speckle correlation interferometry are susceptible to noise arising from dirt particles and defects found in the beam expanders. This results in a degeneration of the fringe information. To ensure the integrity of this information, an objective means of monitoring in situ the extent of expander noise is required. In this paper, a practical and cost-effective method based on digital spectral analysis is proposed and demonstrated.