利用相干或部分相干光被粗糙表面散射产生的散斑现象进行表面粗糙度测量是一类有应用前景的在线测量技术。研究了窄带连续谱光束被随机粗糙表面散射形成的远场散射光场的散斑延长效应和将其应用于表面粗糙度测量的可行性。理论和模拟研究表明: 随着观测点逐渐远离散射光场中心, 散斑延长率越来越大; 在相同的观测位置, 表面的粗糙度越小, 散斑延长率越大。构建以超辐射发光二极管(Superluminescent Diode,SLD)为光源的实验系统, 以散斑延长率衍生的光学粗糙度指标来衡量表面粗糙度, 对电火花加工的表面粗糙度对比样块进行粗糙度测量实验, 结果表明光学粗糙度指标随着被测表面粗糙度的增加而单调递减。比起一组分立波长的光源, 采用窄带连续谱光源的表面粗糙度测量系统有更大的测量范围。

Surface roughness measurement using the phenomenon of speckle caused by scattering of coherent or partially coherent light by rough surface was a promising online measurement technique. The speckle elongation effect of the far-field scattered field formed by the scattering of the narrowband continuous spectral beam by random rough surface and the feasibility of applying the effect to the surface roughness measurement were studied in this paper. Theoretical and simulation studies show that the speckle elongation becomes larger as the observation point moves away from the center of the scattered field; moreover, the speckle elongation increases as the surface roughness becomes smaller at the same observation position. The experimental system with Superluminescent Diode(SLD) as the light source was constructed. The surface roughness was measured by the optical roughness index which was derived from the speckle elongation. The roughness measurement experiment was carried out on the EDM surface roughness specimen. The results show that the optical roughness index monotonically decreases as the surface roughness of the measured surface increases. Surface roughness measurement system with the narrowband continuous spectral light source has a larger measurement range than a group of light sources with discrete wavelengths.