Recent Advances in 3D Structured Illumination Microscopy

In structured illumination microscopy (SIM) the sample under investigation is illuminated using a structured illumination (SI) pattern. This SI pattern encodes high spatial frequencies of fine features within the sample, which usually are not transferred by the conventional three-dimensional (3D) optical transfer function (OTF) of the imaging system and fills the missing cone of frequencies in the OTF for better discrimination of the out-of-focus light. Thereby, SIM provides super-resolution (SR) performance beyond the diffraction limit and optical-sectioning (OS) capability with the use of data post-processing approaches. 3D structured patterns that include lateral and axial variations in the illumination have attracted more attention recently as they provide OS and SR enhancement in three dimensions. In this paper, we review recent implementations in generating a 3D SI pattern with tunable modulation frequency (independently of both the objective lens and the wavelength used) using a Fresnel biprism or a Wollaston prism. From the raw SIM images, final SIM images with simultaneous OS and SR are retrieved without artifacts due to coherent noise.