Background <p>Fogging on optical components such as eyeglasses and safety goggles in humid environments can significantly degrade visibility and pose safety risks. While passive anti-fogging methods, such as hydrophobic surface coatings, are commonly used, they are prone to degradation and have limited durability.</p> Objective <p>This study investigates a multiphysics approach to actively defog optical surfaces, transparent in the visible wavelength range, using ultrasonic excitation to enhance anti-fogging performance.</p> Methods <p>An approach consisting of analytical, computational, and experimental methods is developed to validate the efficacy of ultrasound as an active anti-fogging mechanism. Analytical and computational models provide quantitative insights into the hydrodynamic interactions between micro-droplets and ultrasonic energy, and these are validated by tomographic measurements using Optical Coherence Tomography (OCT). A custom environmental chamber was constructed and instrumented with temperature and humidity control, as well as advanced imaging tools to monitor visibility, surface condensation, thermal behavior, and substrate dynamics using Scanning Laser Doppler Vibrometry (SLDV).</p> Results <p>Experiments across a frequency range of 25 kHz to 1 MHz revealed that defogging rates varied significantly with excitation frequency and actuator configuration, with optimal performance observed at the resonant modes of the substrate. With a 122-kHz ultrasonic load, fog was reduced by over 90% within 5 min, and visibility through the fog improved by over 70%.</p> Conclusions <p>The results provide insights into defogging rates at various dynamic conditions, enabling the exploitation and enhancement of anti-fogging performance. Current work presents a promising solution for adaptable anti-fogging of transparent substrates that have important applications in industrial and practical situations.</p>