Super-resolution photoacoustic microscopy using blind structured illumination

We present a method for enhancing the spatial resolution of optical-absorption-based photoacoustic imaging through or within highly scattering media. The optical speckle pattern that emerges as light propagates through diffuse media provides structured illumination to an object placed behind a scattering wall. The photoacoustic signal produced by such illumination is detected using a focused ultrasound transducer. We demonstrate through both simulation and experiment that, by acquiring multiple photoacoustic images, each produced by a different random and unknown speckle pattern, an image of an absorbing object can be reconstructed with a spatial resolution far exceeding that of the ultrasound transducer. The imaging approach and reconstruction method exploiting joint sparsity will be valuable for biomedical applications and other fields where high-frequency structural information is scrambled by diffusive processes.