基于傅里叶变换相位的散斑面内位移量算法

Algorithm of in-plane displacement measured by speckle photography based on phase of Fourier transform

散斑照相计算面内位移时,传统算法直接使用散斑图傅里叶变换的功率谱信息,最小可检测位移量会受到散斑尺寸的限制。为了解决这一问题,采用基于傅里叶变换相位信息的新算法进行了理论分析,证明了新方法中最小和最大可检测位移量取决于所用光电转换器件(如CCD或CMOS)的像元间距和光敏面大小,与散斑尺寸无关。结果表明,该方法的测量范围最小可达2pixel间距,最大可达光电转换器件光敏面宽度的一半。实验测量与理论值吻合。

Traditional algorithm of in-plane displacement measurement by speckle photography is based on the power spectrum of Fourier transform directly. However,the measured minimum displacement is limited by speckle size. In order to solve this problem,a novel algorithm based on the phase angle of Fourier transform was proposed. Theoretical analysis showed that the minimum and maximum displacement measured by this new algorithm was determined by the photoelectric converter,such as charge-coupled device or complementary metal oxide semiconductor. The size of speckle patterns had no effect on displacement. The result shows that the minimum and maximum displacement measured by new method can achieve 2pixel spacings and the half of photo-sensitive area width of photoelectric conversion device respectively. The actual measurement is in agreement with the theoretical analysis.