Multi-depth photoacoustic microscopy with a focus tunable lens

Optical-resolution photoacoustic microscopy (OR-PAM) has been studied to improve its imaging resolution and functional imaging modality without labeling on biology sample. However the use of high numerical aperture (NA) objective lens confines the field of view or the axial imaging range of OR-PAM. In order to obtain images at different layers, one needs to change either the sample position or th e focusing position by mechanical scanning. This mechanical movement of the sample or the objective lens limits the scanning speed and the positioning precision. In this study, we propose a multi-depth PAM with a focus tunable lens. We electri cally adjusted the focal length in the depth direction of the sample, and twice extended the axial imaging range up to 660 m with the objective lens (20X, NA 0.4). The proposed approach can increase scanning speed and avoid step motor induced distortions during PA signal acquisitions without mechanical scanning in the depth direction. To in vestigate the performance of the multi-depth PAM system, we scanned a black human hair and the ear of a living nude mouse (BALB/c Nude). The obtained PAM images presented the volumetric rendering of black hair and the vasculature of the nude mouse. Keywords: photoacoustic imaging, focus tunable le ns, optical imaging, biomedical imaging