Skandarajah Arunan, Reber Clay D, Switz Neil A, Fletcher Daniel A
Department of Bioengineering, University of California, Berkeley, Berkeley, California, United States of America.
Biophysics Graduate Group, University of California, Berkeley, Berkeley, California, United States of America.
PLoS One. 2014 May 13;9(5):e96906. doi: 10.1371/journal.pone.0096906. eCollection 2014.
Use of optical imaging for medical and scientific applications requires accurate quantification of features such as object size, color, and brightness. High pixel density cameras available on modern mobile phones have made photography simple and convenient for consumer applications; however, the camera hardware and software that enables this simplicity can present a barrier to accurate quantification of image data. This issue is exacerbated by automated settings, proprietary image processing algorithms, rapid phone evolution, and the diversity of manufacturers. If mobile phone cameras are to live up to their potential to increase access to healthcare in low-resource settings, limitations of mobile phone-based imaging must be fully understood and addressed with procedures that minimize their effects on image quantification. Here we focus on microscopic optical imaging using a custom mobile phone microscope that is compatible with phones from multiple manufacturers. We demonstrate that quantitative microscopy with micron-scale spatial resolution can be carried out with multiple phones and that image linearity, distortion, and color can be corrected as needed. Using all versions of the iPhone and a selection of Android phones released between 2007 and 2012, we show that phones with greater than 5 MP are capable of nearly diffraction-limited resolution over a broad range of magnifications, including those relevant for single cell imaging. We find that automatic focus, exposure, and color gain standard on mobile phones can degrade image resolution and reduce accuracy of color capture if uncorrected, and we devise procedures to avoid these barriers to quantitative imaging. By accommodating the differences between mobile phone cameras and the scientific cameras, mobile phone microscopes can be reliably used to increase access to quantitative imaging for a variety of medical and scientific applications.
将光学成像用于医学和科学应用需要对诸如物体大小、颜色和亮度等特征进行准确量化。现代手机上配备的高像素密度摄像头使摄影对于消费应用而言变得简单便捷；然而，实现这种简便性的摄像头硬件和软件可能会对图像数据的准确量化造成障碍。自动设置、专有图像处理算法、手机的快速更新换代以及制造商的多样性加剧了这一问题。如果手机摄像头要充分发挥其在低资源环境中增加医疗服务可及性的潜力，就必须充分了解基于手机成像的局限性，并通过尽量减少其对图像量化影响的程序来加以解决。在此，我们聚焦于使用与多家制造商的手机兼容的定制手机显微镜进行微观光学成像。我们证明，使用多部手机可以实现具有微米级空间分辨率的定量显微镜检查，并且可以根据需要校正图像的线性度、畸变和颜色。通过使用2007年至2012年间发布的所有版本的iPhone以及部分安卓手机，我们表明，像素超过500万的手机在广泛的放大倍数范围内，包括与单细胞成像相关的放大倍数下，能够实现近乎衍射极限的分辨率。我们发现，如果不进行校正，手机上的自动对焦、曝光和颜色增益标准会降低图像分辨率并降低颜色捕捉的准确性，并且我们设计了程序来避免这些定量成像的障碍。通过适应手机摄像头与科学摄像头之间的差异，手机显微镜可以可靠地用于增加各种医学和科学应用中定量成像的可及性。
