非相干衍射法在表面平度检验中的应用

Application of incoherence diffraction for spection of surface roughness

提出了一种对材料表面平度进行测量和评价的光学和数字相结合的新方法。建立了表面水平侧影在非相干光学成像系统中的数学模型，把侧影看成是放在空间不变线性系统中的阶跃函数，在非相干光学成像系统中其图像输出即是在空间频率意义下阶跃函数的傅立叶交换。设计了一套实现上述测量的光学数字系统。并用数字信号处理技术消除背景噪声，对表面的不平斑粒进行模式识别和统计分类。最后实测衍射强度的纹波，分析成像系统的冲激响应，计算该系统的光学传递函数，从而评价整个系统的成像质量和精度。

A new hybird processing technique, i.e. an optical-digital processing technique, to measure and evaluate the roughness of a material surface is presented. The mathematical model of the horizontal profile of the surface is obtained. It is regarded as a step function which is placed in a space-invariant linear imaging system. Its image output in the incoherent imaging system is the Fourier transform of the step function at the spatial-frequencies. An optical-digital system is designed to measure the image. The processing of digital signals is utilized to reject the noise on background of the image, recongnize and classify the rough defects. ally, the practical diffraction model was tested, the impulse response of the imaging system was analysized with the optical transfer function of the system evaluated. The accuracy and quality of the system was estimated as well.