An oblique-incidence statistical model for laser speckle

The evaluation of laser speckle statistics at different illumination angles is highly significant in industry, e.g., non-destructive surface inspection or motion analysis and measurement. Current speckle theories overlook the shadowing effect and the shape of laser spot, leading to inaccurate speckle statistics at large incident angles. This paper presents an oblique-incidence statistical model (OISM) for calculating subjective speckle statistics under oblique illumination. The model introduces an autocorrelation function of the scattered wave with shadowing effects and considers laser spot deformation by oblique illumination. With these additions, OISM allows for incident angles ranging from 0 degrees degrees to 80 degrees degrees and any lateral correlation length of the surface-height fluctuations. Extensive experiments demonstrate the accuracy of the proposed model, especially when the lateral correlation length is small or the illumination angle is close to 80 degrees. degrees .