Park Joo Hyun, Lee Jae Yong, Lee Eun Seong
Nano and Bio Surface Science, University of Science and Technology, Daejeon 305-350, South Korea ; These authors contributed equally to this work.
Nano and Bio Surface Science, University of Science and Technology, Daejeon 305-350, South Korea ; Center for Length, Korea Research Institute of Standards and Science, Daejeon 304-340, South Korea ; These authors contributed equally to this work.
Biomed Opt Express. 2014 May 21;5(6):1895-912. doi: 10.1364/BOE.5.001895. eCollection 2014 Jun 1.
We present a method to improve the isotropy of spatial resolution in a structured illumination microscopy (SIM) implemented for imaging non-fluorescent samples. To alleviate the problem of anisotropic resolution involved with the previous scheme of coherent SIM that employs the two orthogonal standing-wave illumination, referred to as the orthogonal SIM, we introduce a hexagonal-lattice illumination that incorporates three standing-wave fields simultaneously superimposed at the orientations equally divided in the lateral plane. A theoretical formulation is worked out rigorously for the coherent image formation with such a simultaneous multiple-beam illumination and an explicit Fourier-domain framework is derived for reconstructing an image with enhanced resolution. Using a computer-synthesized resolution target as a 2D coherent sample, we perform numerical simulations to examine the imaging characteristics of our three-angle SIM compared with the orthogonal SIM. The investigation on the 2D resolving power with the various test patterns of different periods and orientations reveal that the orientation-dependent undulation of lateral resolution can be reduced from 27% to 8% by using the three-angle SIM while the best resolution (0.54 times the resolution limit of conventional coherent imaging) in the directions of structured illumination is slightly deteriorated by 4.6% from that of the orthogonal SIM.
我们提出了一种方法，用于在为非荧光样本成像而实现的结构照明显微镜（SIM）中提高空间分辨率的各向同性。为了缓解与先前采用两个正交驻波照明的相干SIM方案（称为正交SIM）相关的各向异性分辨率问题，我们引入了一种六边形晶格照明，该照明同时包含三个在横向平面上等分方向叠加的驻波场。针对这种同时多光束照明的相干图像形成，我们严格推导了理论公式，并得出了用于重建高分辨率图像的显式傅里叶域框架。使用计算机合成的分辨率目标作为二维相干样本，我们进行了数值模拟，以研究我们的三角度SIM与正交SIM相比的成像特性。对具有不同周期和方向的各种测试图案的二维分辨能力的研究表明，使用三角度SIM时，横向分辨率的方向依赖性波动可从27%降低到8%，而在结构照明方向上的最佳分辨率（传统相干成像分辨率极限的0.54倍）与正交SIM相比略有下降，下降了4.6%。
