The mean intensity distribution of the laser speckle formed by reflection on the rough aluminium surface is measured experimentally and the scattering angle dependent result is compare with the Sancer's modified Beckmann scattering theory. Two rough aluminium surfaces which are used in the present experiment are prepared by grinding the flat aluminium plate with SiC powders of mesh #120 and #320, respectively. For large incidence angles ($\theta_0$ = -40˚, -60˚), the measured mean intensity deviates from the value predicted by Beckmann scattering theory. The shadowing effect was quantitively investigated by M.I. Sanccer by modifying the Beckmann scattering theory and in this research his theory is used in the explanation of the experimentally obtained deviation. Computer simulations of the Sancer's theory is carried out and the result of the simulation shows that Sancer's theory explains adequately the experimental result at scattering angle larger than 60˚ where the effect of multiple scattering is small and the shadowing effect is predominant.
