Tomassini P, Giulietti A, Gizzi L A, Galimberti M, Giulietti D, Borghesi M, Willi O
Appl Opt. 2001 Dec 10;40(35):6561-8. doi: 10.1364/ao.40.006561.
Laser plasma interferograms are currently analyzed by extraction of the phase-shift map with fast Fourier transform (FFT) techniques [Appl. Opt. 18, 3101 (1985)]. This methodology works well when interferograms are only marginally affected by noise and reduction of fringe visibility, but it can fail to produce accurate phase-shift maps when low-quality images are dealt with. We present a novel procedure for a phase-shift map computation that makes extensive use of the ridge extraction in the continuous wavelet transform (CWT) framework. The CWT tool is flexible because of the wide adaptability of the analyzing basis, and it can be accurate because of the intrinsic noise reduction in the ridge extraction. A comparative analysis of the accuracy performances of the new tool and the FFT-based one shows that the CWT-based tool produces phase maps considerably less noisy and that it can better resolve local inhomogeneties.
目前，激光等离子体干涉图是通过使用快速傅里叶变换（FFT）技术提取相移图来进行分析的[《应用光学》18, 3101 (1985)]。当干涉图仅受到噪声和条纹可见度降低的轻微影响时，这种方法效果良好，但在处理低质量图像时，它可能无法生成准确的相移图。我们提出了一种用于相移图计算的新方法，该方法在连续小波变换（CWT）框架中大量使用了脊线提取。由于分析基的广泛适应性，CWT工具具有灵活性，并且由于脊线提取中固有的降噪功能，它可以做到准确。对新工具和基于FFT的工具的精度性能进行的比较分析表明，基于CWT的工具生成的相位图噪声要小得多，并且能够更好地分辨局部不均匀性。
