Application of Wavelet Digital Filter in the Radial Shearing Interferometry

For the problem of spectrum aliasing of radial shearing interference fringes, a new technique for removing the background components and high frequency components of interference fringes based on discrete wavelet transform (DWT) is established. This image pre-filtering stage not only enables the FFT method to demodulate interference fringes with larger bandwidths but also reduces speckle noise significantly. When the wavefront is complex, the reconstruction RMS error is better than λ/25 by FFT method, however, by using the new method suggested here it is better than λ/40. Comparison analysis showed that the new method has strong capabilities to anti-noise and anti-aliasing of spectrum, reduces the frequency domain filter design requirements and improves the accuracy and stability of the wavefront detection.