Non-Contact Speed Measurement—a Comparison of Optical Systems

Abstract

Four different optical methods of speed measurement for moving surfaces are considered, two using incoherent light and two using coherent laser light. These systems are described as spatial filters acting on the Wiener spectrum of the moving surface. For this purpose, the Wiener spectrum of the speckling image of a coherently illuminated, moving surface is derived in the near field Fresnel region. Based on the theoretical analysis, the four systems are compared considering systematic errors and the bandwidth of output signals.