Imaging Optical Fields Through Heavily Scattering Media

In the field of biomedical optics, optical scattering has traditionally limited the range of imaging within tissue to a depth of one millimetre. A recently developed class of wavefront-shaping techniques now aims to overcome this limit and achieve diffraction-limited control of light beyond one centimetre. By manipulating the spatial profile of an optical field before it enters a scattering medium, it is possible to create a micrometre-scale focal spot deep within tissue. To successfully operate in vivo, these wavefront-shaping techniques typically require feedback from within the biological sample. This Review summarizes recently developed ‘guidestar’ mechanisms that provide feedback for intra-tissue focusing. Potential applications of guidestar-assisted focusing include optogenetic control over neurons, targeted photodynamic therapy and deep tissue imaging.

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“…Acquiring a sequence of speckle measurements may also help compute an image of such an embedded moving object, as recently considered in ref. 93.…”

Section: Wavefront Shaping With Conjugation Guidestarsmentioning

confidence: 99%

Guidestar-assisted wavefront-shaping methods for focusing light into biological tissue

2015

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“…Field incident on a 9 mm thick scattering sample having µ ′ s = 4 cm −1 : (a) reconstruction from measured intensity data and (b) estimated for two apertures of 0.8 mm diameter separated by 1.6 mm, center to center. 5 Phase retrieval 8 is needed to obtain the phase term, φ(∆r), in Eq. (4), to obtain the magnitude of the Fourier spectrum of the object image.…”

Section: Aperturementioning

confidence: 99%

“…We describe an approach to access complex field information related to the object from speckle spatial correlation measurements, which are taken as the object is translated to different positions. 4,5 It is demonstrated that, after phase retrieval, imaging through or inside a strongly scattering environment is effective. This work stems from earlier understanding 6 with two beams incident on a randomly scattering medium.…”

Section: Introductionmentioning

confidence: 99%

Imaging fields through heavily scattering random media with speckle correlations over source position

2015

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“…light scattering | imaging | nanoparticles | plasmonics | metamaterials O ur understanding of light scattering in complex media is built almost exclusively on the interaction of light with broadband low-loss scatterers, characteristic of many natural systems such as animal tissue, fog, or sea spray (1)(2)(3)(4)(5)(6). In contrast, metallic nanoparticles possess plasmon resonances with strongly frequency-dependent absorption and scattering cross-sections, where the resonant frequency is controlled by nanoparticle size, shape, and local dielectric environment (7)(8)(9).…”

mentioning

confidence: 99%

Imaging through plasmonic nanoparticles

Tanzid

Sobhani

DeSantis

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The optical properties of metallic nanoparticles with plasmon resonances have been studied extensively, typically by measuring the transmission of light, as a function of wavelength, through a nanoparticle suspension. One question that has not yet been addressed, however, is how an image is transmitted through such a suspension of absorber-scatterers, in other words, how the various spatial frequencies are attenuated as they pass through the nanoparticle host medium. Here, we examine how the optical properties of a suspension of plasmonic nanoparticles affect the transmitted image. We use two distinct ways to assess transmitted image quality: the structural similarity index (SSIM), a perceptual distortion metric based on the human visual system, and the modulation transfer function (MTF), which assesses the resolvable spatial frequencies. We show that perceived image quality, as well as spatial resolution, are both dependent on the scattering and absorption cross-sections of the constituent nanoparticles. Surprisingly, we observe a nonlinear dependence of image quality on optical density by varying optical path length and nanoparticle concentration. This work is a first step toward understanding the requirements for visualizing and resolving objects through media consisting of subwavelength absorber-scatterer structures, an approach that should also prove useful in the assessment of metamaterial or metasurface-based optical imaging systems.light scattering | imaging | nanoparticles | plasmonics | metamaterials O ur understanding of light scattering in complex media is built almost exclusively on the interaction of light with broadband low-loss scatterers, characteristic of many natural systems such as animal tissue, fog, or sea spray (1-6). In contrast, metallic nanoparticles possess plasmon resonances with strongly frequency-dependent absorption and scattering cross-sections, where the resonant frequency is controlled by nanoparticle size, shape, and local dielectric environment (7-9). This characteristic enables the predictive design and fabrication of nanoparticles and nanoparticle-based media with specific absorption and scattering properties at precise wavelengths of choice throughout the UV, visible, and infrared regions of the spectrum (10-16). Since their use in antiquity as the vivid colorants in stained glass windows, this frequency dependence has been of primary interest. In the context of modern optics, plasmon-resonant lineshapes are studied extensively through spectroscopic measurements. However, the problem of resolving an image through a suspension of plasmonic nanoparticles, for example, dispersed in an otherwise transparent solid or liquid medium, or patterned onto a transparent substrate, has yet to be investigated. Here, we examine how the properties of plasmonic nanoparticles in dilute suspension modify a transmitted image. To do so, we use two very different strategies. First, we determine the Structural SIMilarity index (SSIM) of the plasmonic medium-transmitted image relative to the origi...

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Imaging Optical Fields Through Heavily Scattering Media

Cited by 55 publications

References 28 publications

Guidestar-assisted wavefront-shaping methods for focusing light into biological tissue

Guidestar-assisted wavefront-shaping methods for focusing light into biological tissue

Imaging fields through heavily scattering random media with speckle correlations over source position

Imaging through plasmonic nanoparticles

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