Lens Free Super-Resolution Microscopy
Distributed Aperture Illumination Allows Large Working Distances
- Fig. 1: Principle of Distributed Aperture Illumination Microscopy. Blue discs: Individual sources S1, S2,…SK,.. SN of coherent, collimated light at positions (xK,yK,zK) with defined phase and polarization relations emitting the light in defined directions (purple, one indicated by a white arrow); the red “spot” indicates the joint focal illumination distribution (i.e. the “focal volume” or the “observation volume of the illumination spot”) produced by the constructive interference of the collimated waves. Altogether, the sources span a solid angle Ω = 2π (1-cosθ), corresponding to the numerical aperture (NA) of a conventional objective lens with half opening angle θ. Published in Scientific Reports under the Creative Commons Attribution License (CC-BY) by Birk et al. .
- Fig. 2: Focal spot for sources covering a solid angle of Ω = 1.25π. Intensity distribution calculated for 6,580 sources distributed over Ω = 2π (1-cosθ) = 1.25π (this corresponds to an objective lens with NA =1.4). In this calculation, the refractive index at the position of the focus is given by n = 1.518. (a) Lateral distribution of the focal intensity F(x,y). (b) Profile across the lateral focus intensity distribution along the x- or y-axis. (c) x-z-section through the focus intensity distribution. (d) Shows the corresponding axial profile Fx=y=0(z). In principle, the light sources may be positioned at arbitrary large distances from the focal region. Published in Scientific Reports under the Creative Commons Attribution License (CC-BY)  by Birk et al. .
- Fig. 3: Implementation of Stimulated Emission Depletion (STED)/MINFLUX mode. Left: z-projection of the arrangement of N = 6,576 coherent light sources (e.g. glass fibers with low numerical aperture) directed towards the origin. Sources are distributed within a solid angle of Ω = 2π(1-cosθ) = 1.25π (This corresponds to an objective lens with NA =1.4). Center: y-z section across the intensity distribution around the origin. The STED beam width given (axial: 378 nm, lateral: 293 nm) refers to the FWHMs of the respective minima (z; x,y). Right: x-y section across the intensity distribution around the origin. For STED-type illumination, half of the sources in the center were phase-delayed by π. In principle, the STED producing light sources may be positioned at arbitrary large distances from the focal region. Instead of using the donut structure at high illumination intensities for STED, it may be used also in the low illumination “Minflux” mode for enhancing the optical resolution down to the nm range. Published in Scientific Reports under the Creative Commons Attribution License (CC-BY)  by Birk et al. .
In the following, it is described an alternative approach based on a “lens free” illumination concept to combine high/enhanced resolution with very large working distances; this approach could lead to the development of “lens free” super-resolution microscopy.
Christoph Cremer1,2, Johann von Hase2, Udo Birk3
1Kirchhoff Institute for Physics (KIP), University Heidelberg, Germany, and Institute of Molecular Biology, Mainz, Germany
2Institute of Pharmacy & Molecular Biotechnology, University Heidelberg, Germany
3Institute for Photonics and ICT, University of Applied Sciences (FHGR), Chur, Switzerland
Prof. Dr. Christoph Cremer
Kirchhoff Institute for Physics (KIP)
Institute of Pharmacy & Molecular Biotechnology
University Heidelberg, Germany
Institute of Molecular Biology
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