Heterodyne Interferometric Sound-Field Imaging with Full-Field Lock-In Detection

Interference-based sound-field imaging techniques, such as digital holography, have a maximum measurable frequency limited by the frame rate of image sensors according to the sampling theorem. In this study, we propose Heterodyne Interferometric Sound-field Imaging (HISI), which combines optical heterodyne interferometry with full-field lock-in detection to visualize high-frequency sound field beyond the Nyquist frequency. The principle is verified through both simulations and experiments, demonstrating that the sound field can be reconstructed from a down-converted signal recorded at a frame rate one order of magnitude lower than the original frequency. The proposed HISI overcomes the conventional frequency limitations in sound-field recording and further extends the achievable measurement duration and field of view.