Direct measurements of time- and size-resolved particulate matter (PM) concentrations are of major importance in air quality studies and pollution monitoring. Low-cost, compact optical particle counters (OPCs), which provide accurate PM measurements independent of the particle complex index of refraction (CRI), can be useful in personal exposure monitoring and distributed sensor network studies applications. A methodology is presented for the optimization of the sensor design and operation parameter space aimed at reducing the effect of the CRI on particle sizing errors. The Monte Carlo numerical simulation, which utilizes Mie scattering calculations, is used to determine the optimal detector angle for the specific set of constraints described by the weighting coefficients. The optimized detector position (θ = 48°) has the lowest dependency on CRI over the entire particle size range of 0.5-10 microns. The near-forward, optimized, and perpendicular detector angles are compared experimentally using monodisperse 2 μm and 4 μm particles of silica, PSL, and alumina; the light collection cone angle is set at α = 20° in all experiments. The data agree well with the numerical results for all tested scenarios. Overall, the perpendicular detector location has the best precision and worst accuracy related to the CRI variations. The optimized detector position has the best accuracy for both silica and alumina particles. The use of low-cost components, such as laser diodes, photodiodes, miniaturized integrated electronics, and simple component layouts allows for the development of compact OPCs capable of accurately sizing PM. The number of sizing bins, sizing accuracy and precision, and other parameters of interest can be used as an input to an optimization algorithm.

中文翻译：

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紧凑型低成本光学粒度仪的设计与优化

直接测量时间和尺寸分辨的颗粒物 (PM) 浓度对于空气质量研究和污染监测至关重要。低成本、紧凑型光学粒子计数器 (OPC) 可提供独立于粒子复合折射率 (CRI) 的精确 PM 测量，可用于个人暴露监测和分布式传感器网络研究应用。提出了一种优化传感器设计和操作参数空间的方法，旨在减少 CRI 对粒径误差的影响。蒙特卡罗数值模拟利用米氏散射计算，用于确定加权系数描述的特定约束集的最佳探测器角度。优化的探测器位置 (θ = 48°) 在 0.5-10 微米的整个颗粒尺寸范围内对 CRI 的依赖性最低。使用二氧化硅、PSL 和氧化铝的单分散 2 μm 和 4 μm 颗粒对近前、优化和垂直探测器角度进行了实验比较；在所有实验中，光收集锥角均设置为α = 20°。这些数据与所有测试场景的数值结果非常吻合。总体而言，垂直探测器位置与 CRI 变化相关的精度最高，精度最差。优化的检测器位置对于二氧化硅和氧化铝颗粒都具有最佳的精度。使用低成本元件，如激光二极管、光电二极管、小型化集成电子器件和简单的元件布局，可以开发出能够精确确定 PM 尺寸的紧凑型 OPC。尺寸调整箱的数量、尺寸调整准确度和精密度以及其他感兴趣的参数可以用作优化算法的输入。