Direct imaging of fluorescent structures behind turbid layers

Giulia Ghielmetti,Christof M Aegerter

doi:10.1364/oe.22.001981

Abstract

We present a method to directly image fluorescent structures inside turbid media. This is based on wave-front shaping to optimize the scattered light onto a single fluorescent particle, as the optical memory effect for a scanning image of the surroundings of this particle. We show that iterating the optimization leads to the focusing on a single particle whose surroundings are subsequently scanned. In combination with a parabolic phase pattern, this method can be extended to a three dimensional imaging method inside turbid media.

Highlights

IntroductionWith the advent of wave-front shaping in extremely turbid media allowing the control of diffusely scattered light [1] either in transmission [2, 3, 4, 5, 6, 7, 8, 9] or in reflection [10, 11, 12], imaging behind or inside turbid media has found renewed interest [13, 14, 15, 16, 17, 18, 19]
We present a method to directly image fluorescent structures inside turbid media
Initial proposals have created a focus behind the turbid layer, either using direct optical access and wave-front shaping [2] or phase conjugation using second harmonic particles [23], which was scanned for obtaining an image [14, 16]

Summary

Introduction

With the advent of wave-front shaping in extremely turbid media allowing the control of diffusely scattered light [1] either in transmission [2, 3, 4, 5, 6, 7, 8, 9] or in reflection [10, 11, 12], imaging behind or inside turbid media has found renewed interest [13, 14, 15, 16, 17, 18, 19]. Initial proposals have created a focus behind the turbid layer, either using direct optical access and wave-front shaping [2] or phase conjugation using second harmonic particles [23], which was scanned for obtaining an image [14, 16]. In the present paper we will follow this second route and show that an iteration of the optimization algorithm on the fluorescence signal can be used to focus on the brightest particle, whose surrounding can be scanned using the optical memory effect [14, 15] This iterative technique is based on previous experiments in acoustic waves, where the focusing on scattering structures has been demonstrated as well [26]. We conclude by putting the method in context and describing further extensions in order to create a three dimensional scanning microscope in turbid media

Setup and samples

Principle

Conclusion