为了实现大视场周期性微结构缺陷检测, 提出了一种基于光学傅里叶变换(FT)的大视场周期性微结构缺陷检测方法, 并搭建相关实验系统进行实验验证。首先, 对周期性微结构的像进行二维快速傅里叶变换, 获取周期性微结构的空间频谱; 然后, 选取一级衍射斑点中的一个斑点做快速傅里叶逆变换, 得到周期性微结构的幅值分布图; 最后, 根据幅值分布图中的幅值突变位置确定缺陷的位置以及根据幅值突变的剧烈程度来定性地判断缺陷处的点偏离原来位置的位移。实验结果表明: 该套系统的测量视场能达到1.5 mm×1.5 mm, 测量分辨率能达到0.5 μm以上, 在保证分辨率达到要求的前提下, 大大地提高了检测视场, 能够快速、高效、便捷地在大视场下对周期性微结构进行缺陷检测。

In order to achieve defect detection of periodic microstructure in a large field of view, a defect detection method based on optical Fourier transform was proposed and relevant experimental system was established. Firstly, the periodic microstructure imaging was subject to two-dimensional fast Fourier transform for deriving spatial frequency spectrum of periodic microstructure. Then, a spot among first-order diffraction spots was chosen to be processed by fast Fourier transform for obtaining the amplitude histogram. According to the mutation location in the amplitude histogram, defect positions were determined. The deviation of defects was proportional to the intensity of the amplitude mutations. The experimental result shows that the system can provide a measurement field of view of 1.5 mm×1.5 mm and the measurement resolution over 0.5 μm, improving the detection field greatly on the premise of an adequate resolution. The proposed method enables fast, efficient and convenient defect detection of periodic microstructure in a large field of view.