Real-time ultrahigh-speed imaging based on time-varying acousto-optic filtering

Ultrahigh-speed imaging is crucial for capturing transient phenomena across a wide range of scientific and industrial applications. Time-wavelength mapping-based high-speed imaging, which encodes temporal information into the spectral domain via optical modulation, has attracted significant interest. However, achieving both flexible time windows and high imaging fidelity remains challenging. To overcome this limitation, we propose an ultrahigh-speed imaging technique based on time-varying acousto-optic filtering (TAFUI). By modulating a broadband supercontinuum light source using an acousto-optic tunable filter driven by a time-varying radio frequency signal, TAFUI encodes the temporal evolution of dynamic scenes into the spectral domain with adaptable time windows. The spectrally encoded information is then captured by a hyperspectral camera and reconstructed into a temporal sequence through wavelength-time mapping, which attains high fidelity by minimizing spectral crosstalk. The technique achieves high-fidelity ultrahigh-speed imaging with a frame rate of 1.6 million frames per second, a spatial resolution of 724 lp/mm, and a sequence depth of 16. The imaging capability of TAFUI is demonstrated through experimental observations of the rotation of an optical chopper, the motion of microspheres in a microfluidic chip, and the morphological evolution of presheared water-in-oil droplets during transport. With its compact configuration, flexible time window adjustment, and high image fidelity, TAFUI serves as a powerful tool for high-resolution, real-time observation of complex ultrahigh-speed phenomena in scientific, engineering, and biomedical applications.