减模式下数字散斑干涉光强不均匀性对检测的影响和校正方法

Impact of Inhomogeneous Light Intensity on Test and Its Correction Method for Digital Speckle Interferometry with Substraction

在数字散斑干涉测量中,照明光的不均匀或被测试物反射光的不均匀,会导致条纹图像不均匀,严重时甚至会引起条纹的丢失。在分析剪切型散斑干涉原理的基础上,基于散斑相位差的主值在(—π,π]均匀分布的假设,提出了减模式下光强不均匀的校正方法,即通过构建一个新的强度分布函数,分区域消除背景光强,从而消去光强调制项。使干涉条纹图的显示强度变得均匀。将该方法应用于受到强烈冲撞的航空复合材料的剪切散板干涉测量中,将原来隐藏在光强较弱区域的条纹清晰地显示了出来。表明本文的方法能有效地降低光强不均匀性对散斑干涉条纹图的影响。

In digital speckle interferometry, inhomogeneous illumination on or reflection from a tested obiect will lead to inhomogeneous fringe pattern, and even make the fringe missing. On the basis of analyzing the principle of shearing speckle interferometry and assuming that principal value of speckle phase difference obeys the uniform distribution between -π and π, a method for correcting the substracted fringe pattern modulated by uneven light intensity is proposed. This method is to construct a new function, which can eliminate background light intensity in small areas and remove the term modulated by light intensity. Thus, the fringe pattern becomes homogeneous. It is applied to shearing speckle interferometry to test a piece of aviation composite materials suffering strong impact, and the fringes which hide in dark areas are displayed. It shows the validity of this method to reduce the influence of uneven light intensity on speckle fringe pattern.