Laser radar spectrum of a rotating random rough surface

A theoretical model is presented for the mutual coherence function that describes the power spectrum of the intermediate frequency (IF) signal resulting from coherent laser radar detection of a fully illuminated rough rotating cylinder. Preliminary calculations for the correlation length and bandwidths of the coherently detected dynamic speckle fields show that Doppler effects on speckle dynamics are on the same order of magnitude as speckle translation effects, and that scatterer exchange effects are negligible. We show that for a fully diffuse object, the shape of the spectrum (and autocorrelation function) is Gaussian. The spectrum appears to be the sum of two Gaussian functions when the scattering object has a near-specular component, one due to the specularly reflected field and the other due to the diffusely reflected field. While the IF BW of the signal resulting from the diffusely scattered field depends upon the cylinder's radius, the IF BW of the specularly reflected field depends upon the width of a window function, which is wavelength dependent.