Zhu Jinlong, Zhou Renjie, Zhang Lenan, Ge Baoliang, Luo Chongxin, Goddard Lynford L
Opt Express. 2019 Mar 4;27(5):6719-6733. doi: 10.1364/OE.27.006719.
Recovering tiny nanoscale features using a general optical imaging system is challenging because of poor signal to noise ratio. Rayleigh scattering implies that the detectable signal of an object of size d illuminated by light of wavelength λ is proportional to d/λ, which may be several orders of magnitude weaker than that of additive and multiplicative perturbations in the background. In this article, we solve this fundamental issue by introducing the regularized pseudo-phase, an observation quantity for polychromatic visible light microscopy that seems to be more sensitive than conventional intensity images for characterizing nanoscale features. We achieve a significant improvement in signal to noise ratio without making any changes to the imaging hardware. In addition, this framework not only retains the advantages of conventional denoising techniques, but also endows this new measurand (i.e., the pseudo-phase) with an explicit physical meaning analogous to optical phase. Experiments on a NIST reference material 8820 sample demonstrate that we can measure nanoscale defects, minute amounts of tilt in patterned samples, and severely noise-polluted nanostructure profiles with the pseudo-phase framework even when using a low-cost bright-field microscope.
使用普通光学成像系统恢复微小的纳米级特征具有挑战性，因为信噪比很低。瑞利散射表明，由波长为λ的光照射的尺寸为d的物体的可检测信号与d/λ成正比，这可能比背景中的加性和乘性扰动信号弱几个数量级。在本文中，我们通过引入正则化伪相位解决了这个基本问题，正则化伪相位是一种用于多色可见光显微镜的观测量，在表征纳米级特征方面似乎比传统强度图像更敏感。我们在不对成像硬件做任何改变的情况下实现了信噪比的显著提高。此外，该框架不仅保留了传统去噪技术的优点，还赋予了这个新的测量量（即伪相位）一个类似于光学相位的明确物理意义。对美国国家标准与技术研究院（NIST）参考材料8820样品的实验表明，即使使用低成本的明场显微镜，我们也可以用伪相位框架测量纳米级缺陷、图案化样品中的微小倾斜量以及噪声严重污染的纳米结构轮廓。
