Scattering Assisted Imaging

Marco Leonetti,Giuseppe Antonacci,Silvia Ghirga,Alfonso Grimaldi,Giancarlo Ruocco

doi:10.1038/s41598-019-40997-6

Abstract

Standard imaging systems provide a spatial resolution that is ultimately dictated by the numerical aperture (NA) of the illumination and collection optics. In biological tissues, the resolution is strongly affected by scattering, which limits the penetration depth to a few tenths of microns. Here, we exploit the properties of speckle patterns embedded into a strongly scattering matrix to illuminate the sample at high spatial frequency content. Combining adaptive optics with a custom deconvolution algorithm, we obtain an increase in the transverse spatial resolution by a factor of 2.5 with respect to the natural diffraction limit. Our Scattering Assisted Imaging (SAI) provides an effective solution to increase the resolution when long working distance optics are needed, potentially paving the way to bulk imaging in turbid tissues.

Highlights

Standard imaging systems provide a spatial resolution that is dictated by the numerical aperture (NA) of the illumination and collection optics
In a typical blind-SIM experiment, the speckle grain size is limited by the NA of the illumination and collection optics, which imposes a threshold on the maximum resolution achievable with linear techniques
To control the illumination NA, we introduced an iris of variable diameter D between L1 and DH and measured the speckle patterns as

Summary

Introduction

Standard imaging systems provide a spatial resolution that is dictated by the numerical aperture (NA) of the illumination and collection optics. We exploit the properties of speckle patterns embedded into a strongly scattering matrix to illuminate the sample at high spatial frequency content. The use of speckle patterns has further seen extensive use, for example, in blind structured illumination microscopy (Blind-SIM) where an image is reconstructed with an improved resolution by sophisticated deconvolution algorithms[14,15], typically exploiting the prior knowledge of the sample properties[16,17,18]. In a typical blind-SIM experiment, the speckle grain size is limited by the NA of the illumination and collection optics, which imposes a threshold on the maximum resolution achievable with linear techniques. Our SAI approach exploits the high spatial frequency content generated by the strongly scattering materials placed in the vicinity of the fluorescent samples under analysis. A backscattering (reflection) rather than a typical transmission geometry[5], is used to enhance the resolution, resulting in an imaging protocol which is advantageous when long working distance optics is needed and transmission geometry is forbidden

Methods

Results

Conclusion