光学层析技术中,包含在投影信息中的噪声会严重影响重建精度。针对偏折层析的关键环节,提出分两阶段对噪声进行抑制的方法。其一是在数据提取阶段使用小波分析技术对偏移量进行降噪,其二是重建时使用偏折角平均修正算法抑制噪声对迭代计算的影响。模拟实验中使用莫尔层析重建技术对三峰温度场进行了重建,结果显示降噪处理能够明显改善噪声对重建造成的不良影响,对误差曲线的分析表明,该处理使得100次迭代后误差的降幅高达45%。结合8邻域求导算法和降噪处理技术,对小型防风喷焰进行实际测量,证实了莫尔偏折层析技术在流场测量领域的实用价值。

Projection data obtained through optical techniques for tomographic measurement are often with noise. The reconstruction accuracy is deteriorated by the Gauss- or Poisson-distributed noise. Corresponding to the major steps of tomographic technique, a two-stage denoise technique has been developed. The deflectometric data are denoised by wavelet-based procedure after projection data reduction. Deflection-angle averaging revision algorithm is applied to suppress the noise in iteration. The Moire tomographic reconstruction technique with eight-neighbor derivative algorithm and denoise method is tested using numerically generated data from a known temperature distribution and noise source. The results show that the denoise processing is able to improve the reconstruction accuracy significantly, which reduces the reconstruction errors of 45%. The temperature field of butane flame is then measured by the Moire tomographic technique and the experimental reconstruction is compared with the thermocouple temperature measurement.