Modeling and design of micromachined optical Soller collimators for lensless CCD-based fluorometry
Modeling and design of micromachined optical Soller collimators for lensless CCD-based fluorometry
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DOI：
10.1039/c2an35729a
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发表时间：
2012-01-01
期刊：
影响因子：
4.2
通讯作者：
Rasooly, Avraham
中科院分区：
文献类型：
--
作者：
Balsam, Joshua;Ossandon, Miguel;Rasooly, Avraham
为了满足资源匮乏环境下医疗诊断的需求，有必要开发低成本、简单和便携的用于集成医疗诊断的关注点检测器。之前，我们已经描述了一种简单的无透镜荧光计，其灵敏度在当前的ELISA平板读取器的范围内。无透镜荧光仪的关键是光的空间分布均匀，我们使用一个简单的光学准直器实现了这一点，该准直器基于“针孔堆叠”(一堆黑色PMMA板，带有通过激光加工的针孔阵列)，使得来自LED光源的光可以通过必要的波长滤光器和分析的微流体直接准直到CCD上，而不需要透镜。在这篇文章中，我们描述了设计这些索勒准直器的光学原理，用于无透镜的基于CCD的荧光测量。将发光面模拟为均匀球面发射的不同区域的集合，求出每个发光区对探测器表面的光强贡献。为了从这样的微分模型计算最终的光强分布，我们推导了一个积分方程式，以求和来自二维发射面的单个光强贡献。该方程适用于单孔准直器。通过在ccd图像传感器上放置具有特定纵横比(孔长径比(L/d))的准直器并捕获图像来进行光强度测量。生成的图像是由准直器生成的2D光强度分布。随着纵横比的增加，光强度分布的斜率增加，对应于准直度的增加。为了验证该模型，将测量的最大光强度和平均光强度与由该模型产生的理论预测进行了比较。光强的平均值(R2=0.990)和最大值(R2=0.938)的变化与基于长宽比的建模结果一致。这些轮廓测量表明，与理论预测非常吻合。本文给出的积分方程式可用于完善光学索勒准直器的设计。这些结果可能会导致开发更有效的索勒准直器，用于基于无透镜CCD的荧光测量，用于简单、低成本的无透镜光学探测器，有可能提高服务不足人群的可及性和医疗保健质量。
To address the needs of medical diagnostics in resource-poor settings, it is necessary to develop low cost, simple and portable Point of Care detectors for integrated medical diagnostics. Previously, we have described a simple lensless fluorometer with sensitivity in the range of current ELISA plate readers. The key to the lensfree fluorometer is the uniform spatial distribution of light, which we achieved using a simple optical collimator based on a "stack of pinholes'' (a stack of black PMMA plates with arrays of pinholes machined via laser) enabling the light to be collimated from the LED light source through the necessary wavelength filters and the assay's microfluidics directly onto the CCD without a lens. In this paper, we describe the optical principle for designing these Soller collimators for lensfree CCD-based fluorometry. The illuminating surface was modeled as a collection of differential areas emitting uniformly and spherically, and the intensity contribution of each emitting area was summed over the detector surface. To compute the final light intensity distribution from such a differential model we derived an integral equation to sum the individual intensity contributions from the two-dimensional emitting surface. The equation is for a single-hole collimator. Light intensity measurements were taken by placing a collimator with a particular aspect ratio (the ratio of hole length to diameter (L/d)) over the CCD image sensor and capturing an image. The resulting image is the 2D light intensity profile generated by the collimator. As the aspect ratio is increased the slope of the light intensity profile increases, corresponding to an increased degree of collimation. To test the model, the measured maximum and mean light intensities were compared with the theoretical predictions generated from the model. There was an agreement between the variation of the mean (R-2 = 0.990) and maximum (R-2 = 0.938) values of light intensities with aspect ratios based modeling. These profile measurements suggest an excellent agreement with the theoretical predictions. The integral equation presented here can be used to perfect the design of the optical Soller collimator. These results may lead to the development of more effective Soller collimators for lensfree CCD-based fluorometry for use in simple low cost lensfree optical detectors with the potential to enhance the accessibility and the quality of health care for underserved populations.