Abstract: A numerical method of calculating objective and subjective laser speckle

patterns are developed based on the principles of Fourier optics. Expressions for the drift

velocities of laser speckle and light spot in a sub- jective pattern are derived based on

geometrical optical principles. Devices of imaging experiments are set up to ob- serve the

objective and subjective laser speckle patterns and their respective drift phenomena. Methods

to quantify the drift velocities of speckles and spots are established based on image processing

techniques，which combine cor- relation function，the Fast Fourier Transform algorithm and

convolution theorem. Both experimental and numerical results match perfectly with our

theoretical expressions，which validates the numerical method and geometrical opti- cal model. This

work provides a systematic method to research and an intuitive way to understand the laser speckle

drift phenomenon.

Key words: laser speckle, Fourier optics, geometrical optics, image processing