空间平均的角度散斑相关粗糙度测量模拟研究

Numerical Simulation of Surface-Roughness Measurement Based on Angular Speckle-Correlation Method Using Spatial Average

角度散斑相关是一种不受表面粗糙度轮廓的间距特性影响的粗糙度幅度参量测量方法,它的数学模型通常建立在集平均的基础上。通过模拟计算随机粗糙表面的远场散斑场,以散斑图面上的空间平均代替常规的集平均来计算角度散斑相关系数,并应用集平均的数学模型反演粗糙度参量。结果证实了这种空间平均角度散斑相关粗糙度测量方法的有效性,在同一表面只需对少数个区域进行测量并对测得的粗糙度参量取平均,即可获得足够的测量精度。对于Rq大于2.0μm的表面,测量相对误差小于15%。根据最佳测量条件,该方法适用于大粗糙度表面。

Angular speckle correlation is a method of surface-roughness measurement about amplitude parameter independent on spacing characteristic of the surface roughness profile. The mathematic model of this method is usually based on ensemble average. Through simulating the speckle intensity distribution in the far field of a random rough surface, we compute the degree of angular speckle correlation by substituting spatial average in speckle pattern for conventional ensemble average, and determinate the surface roughness by the mathematic model of ensemble average. The study proves the applicability of this angular speckle-correlation method using spatial average to roughness measurement. Enough measuring precision can be got, as long as a few parts of area on the same surface are measured and the results are averaged. For surfaces with a mean root square error Rq larger than 2 vm, the relative measuring error is less than 15%. According to the best measuring criterion, this method fits the surface with large roughness.