Bright versus dark schlieren imaging: quantitative analysis of quasi-sinusoidal phase objects

摘要

We discuss the schlieren imaging of quasi-sinusoidal phase objects. We demonstrate that, when the zero-order (Fourier) spatial component of the input image is not blocked by the schlieren-knife at the Fourier plane, the intensity distribution on the reconstructed image is a linear function of the phase amplitude. In contrast, if the zero order is completely blocked (i.e., dark Schlieren processing), the intensity distribution on the output image becomes essentially a quadratic function of the phase, and thus a direct phase retrieval is not possible. We discuss the possibility of contrast enhancement and present validation experiments.