The oriented bilateral filtering method for removal of speckle noise in electronic speckle pattern interferometry fringes

In optical interferometry methods, a challenging problem is how to preserve the edges of all fringes perfectly whilst reducing speckle noise effectively. Directivity is an important characteristic of optical interferometry fringes, and it plays an extremely important role in directing the filtering process. Bilateral filtering is a well-known filtering method for edge-preserving in image processing. In this paper, we propose an oriented bilateral filtering method with special application for optical interferometry fringes by incorporating a directional mask to original bilateral filtering method. We test our oriented bilateral filtering method by applying it to four computer-simulated and one experimentally obtained ESPI fringe patterns, respectively, and compare it with the original bilateral filtering method and the tangent least-squares fitting filtering method. The experimental results demonstrate that the proposed method performs impressively in speckle reduction and fringe edge preservation.