The characteristics of laser scattering of rough surfaces composed of periodical and random components generated by mechanical machining were researched. Based on the Helmholtz-Kirchhoff integration theorem and some statistic theories, the formula for calculating the scattering field distribution in the space of rough surfaces was derived. According to the derived formula, the scattering coefficients of rough surfaces with different amplitudes of the periodic component and different roughnesses of the random component were obtained. Meanwhile, the spatial distribution characteristics of the scattering field and its formation were analyzed. The experiments show when the roughness of random component is far less than the laser wavelength, the number of the diffraction fringes augment with the increase of the amplitude of the periodic component. While the roughness of random component is comparable with the magni-rntude of the laser wavelength, the amplitude of the periodic component has a little effect on the scattering field distribution within the range of laser wavelength and the diffraction fringes are disappear. In this circumstance, the scattering field distribution in the space is considered to be modulated by changing the amplitude of the periodic component.%研究了机械加工时由周期分量和随机分量叠加形成的粗糙表面的激光散射特性.基于Helmholtz-Kirchhoff积分定理并结合统计学相关理论,推导得到了上述粗糙表面的散射场强空间分布理论计算公式.根据推导得到的计算公式,计算了不同周期振幅和不同随机粗糙度情况下的散射场强空间分布,并分析了散射场空间分布的特征和形成原因.理论计算结果表明:在随机性粗糙度远小于激光波长时,周期振幅越大,散射场空间分布的“衍射条纹”现象越明显;而在随机性粗糙度和激光波长可比拟时,周期振幅在波长范围内的变化对散射场空间分布特征影响较小,不再有“衍射条纹”出现.在这种情况下,周期振幅的变化所产生的效果相当于是对散射场空间分布进行了调制.
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