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.
© 2007 Optical Society of America
Fourier Optics and Optical Signal Processing
Original Manuscript: July 17, 2006
Revised Manuscript: October 12, 2006
Manuscript Accepted: October 20, 2006
Published: January 25, 2007
Ismael Núñez and José A. Ferrari, "Bright versus dark schlieren imaging: quantitative analysis of quasi-sinusoidal phase objects," Appl. Opt. 46, 725-729 (2007)