Uncertainty principle for partially coherent light

Two intensity functions are introduced for partially coherent light: one in a space domain and a second one in a spatial-frequency domain. Moreover, a quantity is defined that can be considered a measure of the overall degree of coherence of the partially coherent light. It is then shown that the following uncertainty principle can be formulated: the product of the effective widths of the two intensity functions has a lower bound, and this lower bound is inversely proportional to the overall degree of coherence.