Super-resolution in imaging through a transparent spherical microlens has attracted lots of attention because of recent promising experimental results with remarkable resolution improvement. To provide physical insight for this super-resolution phenomenon, previous studies adopted a phenomenological explanation mainly based on the super-focusing effect of a photonic nanojet, while a direct imaging calculation with classical imaging theory has rarely been studied. Here we theoretically model the imaging process through a microlens with vectorial electromagnetic analysis, and then exclude the previously plausible explanation of super-resolution based on the super-focusing effect. The results showed that, in the context of classical imaging theory subject to the two-point resolution criterion, a microlens with a perfect spherical shape cannot achieve the experimentally verified sub-100 nm resolution. Therefore, there must be some other physical mechanisms that contribute to the reported ultrahigh resolution but have not been revealed in theory.

This paper reviews the first challenge on high-dynamic range (HDR) imaging that was part of the New Trends in Image Restoration and Enhancement (NTIRE) workshop, held in conjunction with CVPR 2021. This manuscript focuses on the newly introduced dataset, the proposed methods and their results. The challenge aims at estimating a HDR image from one or multiple respective low-dynamic range (LDR) observations, which might suffer from underor over-exposed regions and different sources of noise. The challenge is composed by two tracks: In Track 1 only a single LDR image is provided as input, whereas in Track 2 three differently-exposed LDR images with inter-frame motion are available. In both tracks, the ultimate goal is to achieve the best objective HDR reconstruction in terms of PSNR with respect to a ground-truth image, evaluated both directly and with a canonical tonemapping operation.

Microsphere-based microscopy systems have garnered lots of recent interest, mainly due to their capacity in focusing light and imaging beyond the diffraction limit. In this paper, we present theoretical foundations for studying the optical performance of such systems by developing a complete theoretical model encompassing the aspects of illumination, sample interaction and imaging/collection. Using this model, we show that surface waves play a significant role in focusing and imaging with the microsphere. We also show that by designing a radially polarized convergent beam, we can focus to a spot smaller than the diffraction limit. By exploiting surface waves, we are able to resolve two dipoles spaced 98 nm apart in simulation using light at a wavelength of 402.292 nm. Using our model, we also explore the effect of beam geometry and polarization on optical resolution and focal spot size, showing that both geometry and polarization greatly affect the shape of the spot.

Multi-dimensional fluorescence imaging of live animal models demands strong optical sectioning, high spatial resolution, fast image acquisition, and minimal photobleaching. While conventional laser scanning microscopes are capable of deep penetration and sub-cellular resolution, they are generally too slow and causing excessive photobleaching for volumetric or time-lapse imaging. We demonstrate the performance of an augmented line-scan focal modulation microscope (aLSFMM), a high-speed imaging platform that affords above video-rate imaging speed by the use of line scanning. Exceptional background rejection is accomplished by combining a confocal slit with focal modulation. The image quality is further improved by merging the information from simultaneously acquired focal modulation and confocal images. Such a hybrid imaging scheme makes it possible to use very low power excitation light in high-speed imaging, and therefore leads to reduced photobleaching that is desirable for three-dimensional (3D) and four-dimensional (4D) in vivo image acquisition.

An approach for the construction of 5trifluoromethyl-1,4-dihydro-1,2,4-triazines has been developed via base-mediated [3 + 3] cycloaddition of in-situ generated nitrile imines and CF 3 -substituted imidoyl sulfoxonium ylides. The metal-free protocol is characterized by readily available starting materials, mild conditions, a broad substrate scope, high efficiency, good synthetic prospect, and scalability.