Image performance in optoacoustic endoscopy depends markedly on the design of the transducer employed. Ideally, high-resolution performance is required over an expanded depth of focus. Current optoacoustic focused transducers achieve lateral resolutions in the range of tens of microns in the mesoscopic regime, but their depth of focus is limited to hundreds of microns by the nature of their spherical geometry. We designed an ultra-broadband axicon detector with a 2 mm central aperture and investigated whether the imaging characteristics exceeded those of a spherical detector of similar size. We show a previously undocumented ability to achieve a broadband elongated pencil-beam optoacoustic sensitivity with an axicon detection geometry, providing approximately 40 μm-lateral resolution maintained over a depth of focus of 950 μm—3.8 times that of the reference spherical detector. This performance could potentially lead to optoacoustic endoscopes that can visualize optical absorption deeper and with higher resolution than any other optical endoscope today.
Current optoacoustic (OA) microscopy configurations often have narrow focal ranges that limit their use for fast volumetric imaging applications. Herein, the focal range of OA microscopes is extended by matching the elongated optical illumination profile of a Bessel beam with the pencil beam acoustic sensitivity profile of a broadband axicon detector. An inverted OA microscope is developed with interchangeable optical illumination and acoustic detection units to assess the working distance and resolutions retained with several combinations of illumination and detection profiles. Matching Bessel illumination with axicon detection extends the depth of focus 17‐fold over traditional configurations. Imaging a tilted mouse ear with the matched Bessel−axicon configuration reveals vasculature over a working distance exceeding 4.2 mm with optical resolution, while affording a sixfold increase in imaging volume over the same scanning duration compared with configurations using standard Gaussian illumination, demonstrating this approach's promise for increasing applications for OA microscopy in preclinical research.
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