| Imaging through opaque, highly scattering walls is a long sought after capability with potential applications in a variety of fields, such as biomedical imaging. The use of wavefront shaping to compensate for scattering has recently brought a renewed interest as a potential solution to this problem. This method relies on the ability to shape an incident wavefront to pre-compensate for scattering, thus providing light control through a scattering layer. In order for these techniques to begin to extend the imaging depth inside of living biological tissue several constraints must be overcome. As living biological tissue is dynamic these techniques must be able to optimize fast enough to overcome the dynamic nature of the tissue. Also key to the practicality of overcoming scattering is focusing light without direct access behind the scattering wall. This thesis presents means of overcoming these limitations through novel optimization algorithms, wavefront shaping for high-speed modulation, and photoacoustic feedback and imaging behind a scattering layer.;A genetic algorithm (GA) is applied for wavefront optimization as a means of enabling parallel mode optimization to increase the speed of the optimization procedure. The results presented show that not only does the GA optimize more quickly, it is more robust in low signal-to-noise (SNR) environments than other optimization algorithms. The low SNR performance is critical to high speed performance, because SNR decreases with the integration time. The GA wavefront optimization is extended towards more complex light control problems, specifically multi-color image projection through scattering layers.;To overcome wavefront shaping modulation frequency limitations a novel wavefront shaping technique utilizing a binary amplitude Digital Micromirror Device (DMD) is demonstrated. The DMD enables wavefront modulation at 24 kHz by encoding binary amplitude computer generated holograms. To achieve real-time optimization and focusing, FPGA computation is demonstrated. This high-speed wavefront optimization system is applied to light control through multi-mode fibers, which exhibit similar light scattering characteristics to highly scattering materials.;The blind focusing limitation of focusing through turbid media is addressed by photoacoustic feedback. By combining the GA optimization with the photoacoustic feedback the optical fluence is enhanced by a factor of ten. This was extended to high-contrast, three-dimensional photoacoustic image creation by scanning the object behind the scatterer. This photoacoustic optimization technique is analyzed in detail through simulation and further experimentation. Interestingly, the photoacoustic optimization yields a sub-acoustic sized optical focus. This result is explained and discussed, and then utilized in the construction of a super-resolution photoacoustic image. |
