Rainbow refractometry has been used in the past to measure size and refractive index of spherical particles, typically droplets in a spray. In the present study, conventional optical configurations for point measurements or line measurements have been extended to allow also the particle position in a plane to be determined, and hence, the designation planar rainbow refractometry. However, this extension introduces challenges in accurately calibrating the 2D scattering angles with the image coordinates. This challenge has been met using a novel calibration method, employing a monodispersed droplet stream traversed through the measurement plane. Experiments confirm achievable horizontal and vertical position accuracies of 0.42 mm and 0.36 mm, respectively, and a refractive index uncertainty of $2 \times {10^{- 4}}$.

中文翻译：

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平面彩虹折射法

过去曾使用彩虹折光法来测量球形颗粒（通常是喷雾中的液滴）的尺寸和折射率。在本研究中，用于点测量或线测量的传统光学配置已经扩展，以允许确定平面中的粒子位置，因此指定平面彩虹折射法。但是，此扩展在使用图像坐标准确校准 2D 散射角方面带来了挑战。使用一种新颖的校准方法解决了这一挑战，该方法采用穿过测量平面的单分散液滴流。实验证实可实现的水平和垂直位置精度分别为 0.42 毫米和 0.36 毫米，折射率不确定性为$2 \times {10^{- 4}}$.