Abstract Calibration of the Mie Scattering Imaging (MSI) technique for microbubble size and concentration measurement in hydrodynamic test facilities is investigated. Monodisperse bubbles are generated by a microfluidic ‘T’ junction, and individual bubbles simultaneously imaged with shadowgraphy and MSI. Nominal bubble diameters between 30 and $$150\,\upmu{\hbox {m}}$$ 150 μ m were tested. The influence of fringe uniformity and intensity for each polarisation on measurement precision was investigated. Parallel polarisation was chosen over perpendicular for its more uniform spacing despite the lower intensity. The linear relation between fringe wavelength and bubble diameter was demonstrated at a measurement angle of $$90^\circ$$ 90 ∘ . The calibration was derived from constants for light scattering, and for the imaging optics. The wavelength of the scattered fringe pattern is predicted using the Lorentz–Mie theory. A practical method for the calibration of interference patterns is presented. Using this approach, the measured bubble diameters from the shadowgraphy and MSI compare to within $$1\,\upmu{\hbox {m}}$$ 1 μ m . A method for determining the size-dependent measurement volume for axisymmetric and arbitrary beam profiles is also presented. Graphic abstract

中文翻译：

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用于流体动力学测试设施中微气泡测量的 Mie 散射成像校准

摘要 研究了米氏散射成像 (MSI) 技术在流体动力学测试设施中用于微气泡尺寸和浓度测量的校准。单分散气泡由微流体“T”接头产生，单个气泡同时使用阴影成像和 MSI 成像。测试了 30 到 $$150\,\upmu{\hbox {m}}$$150 μ m 之间的标称气泡直径。研究了每种偏振的条纹均匀度和强度对测量精度的影响。尽管强度较低，但选择平行极化而不是垂直极化，因为其间距更均匀。在 $$90^\circ$$90 ∘ 的测量角度下证明了条纹波长与气泡直径之间的线性关系。校准源自光散射常数和成像光学常数。使用洛伦兹-米理论预测散射条纹图案的波长。提出了一种校准干涉图的实用方法。使用这种方法，来自阴影成像和 MSI 的测量气泡直径比较在 $$1\,\upmu{\hbox {m}}$$1 μ m 以内。还介绍了一种用于确定轴对称和任意光束轮廓的尺寸相关测量体积的方法。图形摘要