Young’s interference fringes with finite-sized sampling apertures

The theory of Young’s interference fringes is developed with particular attention to the finite size of the sampling apertures. A spatial Fourier transform of the product of the intensity distribution of the finite-sized source and the shifted intensity impulse response of the sampling aperture allows us to define a function Ĝ whose absolute value and phase dictate the visibility and the shift of the fringes, respectively. Alternatively, the function Ĝ may be expressed as a spatial Fourier transform of the spatial-coherence function across the sampling plane times the shifted transfer function of the sampling aperture. The effect of the finiteness of the sampling aperture becomes predominant in the neighborhood of the zeros of the coherence function or in regions where the coherence function is changing fast.