title: Enhancing the isotropy of lateral resolution in coherent structured illumination microscopy.
abstract: 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.
authors.affiliation: Nano and Bio Surface Science, University of Science and Technology, Daejeon 305-350, South Korea ; These authors contributed equally to this work.
authors.forename: Joo Hyun
authors.initials: JH
authors.lastname: Park
authors.affiliation: 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.
authors.forename: Jae Yong
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Center for Nanometrology, Korea Research Institute of Standards and Science, Daejeon 305-340, South Korea.
authors.forename: Eun Seong
authors.initials: ES
authors.lastname: Lee
keywords: (100.6640) Superresolution; (110.0180) Microscopy; (110.1650) Coherence imaging; (110.2990) Image formation theory; (110.3010) Image reconstruction techniques