Compact photoacoustic endoscopy by measuring initial photoacoustic pressure using phase-shift interferometry.

This paper demonstrates a novel photoacoustic endoscopy method using phase-shift interferometry (PSI) for photoacoustic signal detection. The method employs a three-step phase-shifting interferometry technique to detect changes in light intensity induced by the initial photoacoustic pressure. This enables identical optical structures for photoacoustic excitation and detection, simplifying the probe design and facilitating miniaturization. The proposed method eliminates the need for acoustic coupling agents, enabling non-contact detection. We employ a phase-shifting technique to mitigate the influence of random phase variations caused by environmental disturbances. The performance of the proposed method is verified by endoscopic imaging of carbon rods, leaf skeletons, and ex vivo mouse rectum tissues.