Homogenizing properties of beam shaping diffusers illuminated with coherent laser light was studied with special regard on their use in vision applications. Two diffusers projecting circular pattern at different scattering angles (Thorlabs Engineered Diffuser™) were illuminated with different spatial intensity distribution (elliptical Gaussian, nearly flat-top and granular multimode fiber output, respectively) collimated beams. The intensity distribution measured at high angular resolution with a CMOS sensor revealed the granular (speckle) pattern of the projected light having contrast of nearly 1. The smallest speckle size (highest speckle density) could be obtained at the largest aperture size using nearly flat-top and multimode fiber illumination. As an important measure of the homogeneity for vision applications the apparent local contrast was calculated as the function of the spatial averaging. Although, the homogeneity requirements depend on the actual application, the usability of such diffusers in combination with coherent light sources is in general strongly limited in megapixel resolution imaging applications, unless time-varying speckle averaging methods can be applied.

中文翻译：

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用于视觉应用的相干光照明光束整形扩散器的均质化：空间分辨率受斑点图案的限制

研究了用相干激光照射的光束整形散射体的均质特性，并特别考虑了它们在视觉应用中的用途。用不同的空间强度分布（分别为椭圆高斯，近似平顶和粒状多模光纤输出）准直光束照射两个以不同散射角投射圆形图案的散射器（Thorlabs Engineered Diffuser™）。使用CMOS传感器在高角度分辨率下测得的强度分布显示出对比度近乎1的投射光的颗粒状（斑点）图案。使用近乎平坦的光斑，在最大孔径尺寸下可以获得最小斑点大小（最高斑点密度）。顶部和多模光纤照明。作为视觉应用同质性的重要衡量指标，视在局部对比度被计算为空间平均的函数。尽管均质性要求取决于实际应用，但是在百万像素分辨率的成像应用中，此类漫射器与相干光源结合使用的可用性通常受到严格限制，除非可以使用随时间变化的斑点平均方法。