Fast controllable confocal focus photoacoustic microscopy using a synchronous zoom opto-sono objective

Although variable optical focus lenses have been exploited in photoacoustic microscopy (PAM) to improve imaging performance, an optical and acoustic synchronous zoom lens-based confocal PAM system has not yet been achieved previously, to the best of our knowledge. Here we develop a fast controllable confocal focus PAM (FC-PAM) equipped with a synchronous zoom opto-sono objective to facilitate horizontal slice imaging of specimens with irregular surfaces or multilayered structures at different depths. The integration of an opto-sono objective of an electrowetting-based zoom lens allows for the adjustment of the confocal focal length. Using this objective, the FC-PAM achieved a confocal focus-shifting range of approximately 6 to 43 millimeters with a high transverse resolution, and the confocal focus-shifting time was substantially reduced. Phantom experiments and human skin imaging were performed to demonstrate that the opto-sono objective has great potential for studying living biological tissue and promoting the development of in vivo rapid-noninvasive PAM depth imaging.