industrial production. In this paper， based on the optical path compensation method， the

Mach-Zehnder interferometric optical path is used

to measure the liquid diffusion coefficient. The object light and the reference light of a laser

holographic interference path passed through the diffusion groove and the compensation groove

respectively. When the liquid to be measured

diffused in the diffusion groove， the interference pattern would change. The diffusion

coefficient can be obtained by

image processing of two interference patterns at different times by fringe

discrimination method. Wavelet deposing

and frequency-domain filtering are required for image processing. After the interference

patterns at different times are superimposed after filtering， the phase changes are obtained

by phase discretization of the superimposed images using the least square phase unwrapping

algorithm of DCT transform. The liquid phase diffusion coefficient can be

obtained by reading the distance between the maximum concentration changes.