Fig. 7: Virtual relay imaging through scattering media.

a A local refractive index contrast is generated in the tissue by US pressure waves. b A collimated beam of light is expanded as a result of scattering in the tissue. c Light is confined in the high refractive index region, counterbalancing the effect of scattering in the tissue. Experimental results showing: d laser beam focused by ultrasound in a minimally scattering tissue phantom; e dispersion and attenuation of the laser beam passing through a scattering tissue phantom without ultrasound; f laser beam focused by ultrasound in a scattering tissue. g The measurement setup to demonstrate the relaying effect of the virtual ultrasonically sculpted GRIN lens through a deep scattering medium, which is normally opaque in the visible range. h When the transducer is OFF, the image is out of focus, and the strong background caused by scattering is evident. i When the transducer is driven at 46.3 V, the image of the target object is relayed through the 29 mm depth of the turbid medium and is clearly resolved. The depth of this turbid medium corresponds to an optical thickness of OT = 5.7 MFP. The exposure time used for acquiring Fig. 7h was three times higher than the exposure time used for Fig. 7i