The particle/droplet image analysis (PDIA) technique is often used for droplet sizing in sprays. Successful use of PDIA for drop size measurement in sprays mandates careful calibration, and determination of the depth of field (DOF) for particles of different size classes. This is typically done with a calibration target that has circles etched on it. In the present study, a calibration experiment was performed with a calibration target as well as droplets, to evaluate the uncertainties in the measured sizes and also to compare the measured depth of field (DOF) values. A continuous-jet droplet generator was used to produce mono-disperse droplets of sizes ranging from 54-393 µm, and the calibration glass plate used contained circles of sizes ranging from 20-400 µm. Images of these were captured using a CCD camera equipped with a long-distance microscope and were processed using a code written in MATLAB. Differences in the measured sizes of droplets and circles, and their depth of field values are reported. It was observed that the use of the calibration target led to an underestimation of the error in droplet size measurements, and an overestimation of the depth of field. For the droplets, the measurement error was observed to be less than 5%, with the parameters chosen.

中文翻译：

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PDIA 实验中测量误差和景深的估计：使用水滴和校准目标的比较研究

粒子/液滴图像分析 (PDIA) 技术通常用于喷雾中的液滴尺寸分析。成功使用 PDIA 测量喷雾中的液滴尺寸需要仔细校准，并确定不同尺寸级别颗粒的景深 (DOF)。这通常是通过一个刻有圆圈的校准目标来完成的。在本研究中，使用校准目标和液滴进行校准实验，以评估测量尺寸的不确定性，并比较测量的景深 (DOF) 值。连续喷射液滴发生器用于产生尺寸范围为 54-393 µm 的单分散液滴，所使用的校准玻璃板包含尺寸范围为 20-400 µm 的圆。这些图像是使用配备长距离显微镜的 CCD 相机拍摄的，并使用 MATLAB 编写的代码进行处理。报告了液滴和圆圈测量尺寸的差异，以及它们的景深值。据观察，校准目标的使用导致对液滴尺寸测量误差的低估，以及对景深的高估。对于液滴，观察到测量误差小于 5%，选择参数。