Abstract
Recently, ℓ1 -norm based reconstruction approaches have been used with linear array systems to improve photoacoustic resolution and demonstrate undersampled imaging when there is sufficient sparsity in some domain. However, such approaches have yet to beat the half-wavelength resolution limit. In this paper, the ability to beat the half-wavelength diffraction limit is demonstrated using a 5 MHz ring array photoacoustic tomography system and ℓ1 -norm based reconstruction approaches. We used the array system to image wire targets at ≈ 2 - 3cm depth in both intralipid scattering solution and water. The minimum observable separation was estimated as 70 ± 10μm , improving on the half-wavelength resolution limit of 145μm . This improvement was demonstrated even when using a random projection transform to reduce data by 99% , enabling substantially faster reconstruction times. This is the first photoacoustic tomography approach capable of beating the half-wavelength resolution limit with a single laser shot.