Combined denoising filter for fringe pattern in electronic speckle shearing pattern interferometry
The basic spin filter for interferometric fringe patterns is improved and developed into several new versions for different applications. These spin filters can filter off random noise efficiently and have almost no blurring effect and phase distortion for the fringe patterns. First, they find the local fringe tangent direction, and then they apply a one-dimensional low-pass filter on this direction. In this way the spin filters can separate easily and clearly high-frequency noise from a real fringe signal with nearly zero frequency. The new spin filters are suitable not only for various fringe patterns but also for wrapped-phase, line-grating, and cross-grating patterns, which are impossible by common filters.