Conventional optical lenses are usually used in OCT systems to perform high lateral resolution imaging. However, the
Gaussian beam profile typically used in OCT links the depth of focus (DOF) to the lateral resolution. We have
experimentally shown that using a cascade system of an ultrasonic virtual tunable optical waveguide (UVTOW) and a
short focal-length lens can provide a large DOF without severely compromising the lateral resolution compared to an
external lens with the same effective focal length. We demonstrate the tunability of the focal length that this system
offers without any need for mechanical perturbation to the imaging setup.
We discuss the characterization and analysis of ultrasonically sculpted virtual optical waveguides in scattering media using a novel physics-based renderer. Our renderer is physically accurate, unbiased, and fast. Unlike other simulators, our renderer can handle heterogeneous refractive index profiles in scattering media. Using the renderer, we characterized the effect of different parameters of virtual optical waveguides to enhance the overall light throughput in transparent and scattering media. The simulator can potentially be used for analysis-by-synthesis and design of innovative acousto-optics systems, capable of generating complex virtual elements in scattering media.
We demonstrate a novel technique for in situ 3D spatial light patterning using ultrasound. By employing a customdesigned ultrasonic phased array, we form standing pressure waves that modulate the refractive index of the target medium in which light patterns are to be formed. Ultrasound pressure waves change the density of the medium locally and as a result, the refractive index is changed. Therefore, the phase front of the traveling optical waves in the medium is modulated. The interaction of light and ultrasound through the medium can be designed such that a collimated beam of light is gradually focused to multiple points deep into the medium to form arbitrary patterns of light illumination, as well as multipoint parallel imaging. These patterns can be reconfigured by changing the ultrasound interference patterns by controlling the frequency and phase of the ultrasound array elements. In this work, we demonstrate experimentally that this technique can be used to perform multi-point imaging in turbid media.
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