Image scanning microscopy: an overview

• Published in: Journal of microscopy (Oxford) 2017-05, Vol.266 (2), p.221-228
• Main Authors: WARD, E.N., PAL, R.
• Format: Article
• Language: English
• Subjects: Image scanning microscopy; structured illumination; super‐resolution microscopy
• ISSN: 0022-2720; 1365-2818
• DOI: 10.1111/jmi.12534

Summary For almost a century, the resolution of optical microscopy was thought to be limited by Abbé’s law describing the diffraction limit of light. At the turn of the millennium, aided by new technologies and fluorophores, the field of optical microscopy finally surpassed the diffraction barrier: a milestone achievement that has been recognized by the 2014 Nobel Prize in Chemistry. Many super‐resolution methods rely on the unique photophysical properties of the fluorophores to improve resolution, posing significant limitations on biological imaging, such as multicoloured staining, live‐cell imaging and imaging thick specimens. Structured Illumination Microscopy (SIM) is one branch of super‐resolution microscopy that requires no such special properties of the applied fluorophores, making it more versatile than other techniques. Since its introduction in biological imaging, SIM has proven to be a popular tool in the biologist's arsenal for following biological interaction and probing structures of nanometre scale. SIM continues to see much advancement in design and implementation, including the development of Image Scanning Microscopy (ISM), which uses patterned excitation via either predefined arrays or raster‐scanned single point‐spread functions (PSF). This review aims to give a brief overview of the SIM and ISM processes and subsequent developments in the image reconstruction process. Drawing from this, and incorporating more recent achievements in light shaping (i.e. pattern scanning and super‐resolution beam shaping), this study also intends to suggest potential future directions for this ever‐expanding field. Lay Description The resolving ability of a light microscope is limited by the diffraction of light. This resolution barrier can be surpassed in a number of ways: by using the unique photophysical properties of the fluorophores; localising sparsely emitting fluorophores; or by using patterned illumination. Image Scanning Microscopy (ISM) is a technique that uses grid patterns of diffraction‐limited spots to achieve super‐resolution. This review discusses the theory of the technique and its limitations, and suggests potential future directions.