Simultaneous Magnitude and Direction Measurements of a Diffuse Object's Velocity Using the Rotating Directional Detecting Aperture in a Laser Speckle Zero-crossing Method

The zero-crossing number of speckle intensity fluctuations produced in the diffraction field by a diffuse object moving in a plane and integrated spatially by a finite-size aperture having the directional forms of, for example, the ellipse and the rectangle is studied theoretically and experimentally. The theoretical and experimental results indicate that the magnitude and direction of the moving object's velocity can be simultaneously measured by counting the zero-crossings of the spatially integrated speckle intensity fluctuations.