Imaging with scattered light

Random scattering of light in complex samples such as biological tissue renders most objects opaque to optical imaging techniques, diffusing every focused beam into a complicated speckle pattern. However, although random, scattering is a deterministic process, and it can be undone and also exploited by controlling the incident optical wavefront, using computer controlled spatial light modulators (SLMs). These insights form the basis for the emerging field of optical wavefront-shaping [1]. Opening the path to new possibilities, such as imaging through visually opaque samples and around corners [2].

The major challenge in the field today is in determining the required wavefront correction without accessing the far side (target side) of the scattering sample.

I will present some of our recent efforts in addressing this challenge [3-8]. These include the use of optical nonlinearities [3], the photoacoustic effect [4-6], and acousto-optics [7] to focus and control light non-invasively inside scattering samples. I will also show how by exploiting inherent correlations of scattered light, it is possible to image through scattering layers and ‘around corners’ using nothing but a smartphone camera [8].

If time permits, I will present the use of these principles for endoscopic imaging through optical fibers [9-10].

References

[1] A.P. Mosk et al., "Controlling waves in space and time for imaging and focusing in complex media", Nature Photonics 6, 283 (2012).

[2] O. Katz et al., "Looking around corners and through thin turbid layers in real time with scattered incoherent light", Nature Photonics 6, 549 (2012).

[3] O.Katz et al., "Noninvasive nonlinear focusing and imaging through strongly scattering turbid layers", Optica, 1, 3, 170-174 (2014).

[4] T. Chaigne et al. "Controlling light in scattering media noninvasively using the photo-acoustic transmission-matrix.", Nature Photonics 8, 58 (2014).

[5] E.Hojman et al. "Photoacoustic imaging beyond the acoustic diffraction-limit with dynamic speckle illumination and sparse joint support recovery", Optics Express Vol. 25, Issue 5, pp. 4875-4886 (2017)

[6] T. Chaigne et al. "Super-resolution photoacoustic imaging via flow-induced absorption fluctuations", Optica Vol. 4, Issue 11, pp. 1397-1404 (2017)

[7] O. Katz et al. " Controlling light in complex media beyond the acoustic diffraction-limit using the acousto-optic transmission matrix", Nature Communications (2019)

[8] O. Katz et al., "Non-invasive single-shot imaging through scattering layers and around corners via speckle correlations", Nature Photonics, 8, 784–790 (2014)

[9] A.Porat et al., "Widefield lensless imaging through a fiber bundle via speckle-correlations", Optics Express (2016)

[10] SM Kolenderska, O Katz, M Fink, S Gigan Scanning-free imaging through a single fiber by random spatio-spectral encoding, Optics letters 40 (4), 534-537 (2015)