[en] In order to perform automatically the thresholding of the amplitude image obtained by phase analysis, a filter based on the probability density of the amplitude is proposed. It generates the image of the significant amplitude by setting to zero the amplitude if its square is lower than 4α₀ log(1/α)/N where α₀ is the mean of the signal, α the risk of error and N the number of frames. The power of the test is discussed and the modification of the filter for pre-processed data is provided. (author)