Abstract
Super-resolution structured illumination microscopy (SIM) routinely performs image reconstruction in the frequency domain using an approach termed frequency-domain reconstruction (FDR). Due to multiple Fourier transforms between the spatial and frequency domains, SIM suffers from low reconstruction speed, constraining its applications in real-time, dynamic imaging. To overcome this limitation, we developed a new method for SIM image reconstruction, termed spatial domain reconstruction (SDR). SDR is intrinsically simpler than FDR, does not require Fourier transforms and the theory predicts it to be a rapid image reconstruction method. Results show that SDR reconstructs a super-resolution image 7-fold faster than FDR, producing images that are equal to either FDR or the widely-used FairSIM. We provide a proof-of-principle using mobile fluorescent beads to demonstrate the utility of SDR in imaging moving objects. Consequently, replacement of the FDR approach with SDR significantly enhances SIM as the desired method for live-cell, instant super-resolution imaging. This means that SDR-SIM is a “What You See Is What You Get” approach to super-resolution imaging.
Highlights
In the conventional optical microscopy, using either wide-field or point-scanning illumination to detect scattering or fluorescence signals, the spatial resolution of the object’s image is confined by the well-known Abbe diffraction limit
Based on directly compressing the point spread function [1], [2]; single-molecule localization microscopy by precisely localizing enormous point-source positions [3], [4], and special patterned illumination microscopy via extending the detected spectrum in the spatial frequency domain or, called k-space based on the Fourier transform theory [5], [6]
The expenditure time for pre-calculations such as the OTF transformed from point spread function (PSF), the coefficient matrix of spatial domain reconstruction (SDR), and the weighted factors for frequency-domain reconstruction (FDR) spectra separation are excluded in the reconstruction time because they only depend on the system and the structured illumination parameters that are invariable during the reconstruction
Summary
In the conventional optical microscopy, using either wide-field or point-scanning illumination to detect scattering or fluorescence signals, the spatial resolution of the object’s image is confined by the well-known Abbe diffraction limit. This has been a barrier for optical imaging for over a century. In the SDR scheme, the SR image is attained by linear superposition of the patterned illuminated raw images with appropriately weighted coefficients that are derivable analytically This concept appeared in the early works of Lucosz and So et al [28], [29]. As the proposed approach is fully compatible with conventional SIM systems, it can be applied to any linear SIM system, and conceivably can be further extended to non-linear SIM schemes to achieve theoretical, unlimited resolution as well
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