| Abstract: | Two image processing techniques for automatic analysis of the Young's fringes diffraction patterns from a double-exposure speckle photograph are described. The techniques involve two-dimensional spectral analysis of the image using the Fast Fourier Transform (FFT) or the Fast Walsh Transform (FWT). The accuracy and reliability of the two techniques are compared as a function of the fringe visibility, and the number of pixels used to represent the image. Walsh analysis is found to offer the same accuracy as Fourier analysis, but in about one third the computation time. The Fourier method is more reliable with fringes of the lowest visibility, however. The ideas presented have relevance to the general problem of detecting and accurately determining the frequency components of a sinusoid in the presence of noise. |
