In industrial applications, especially in material inspection, water immersion ultrasonic scanning microscopy is primarily used to improve the transmission efficiency of ultrasound and the quality of imaging. The specific reasons are as follows:

Improving Ultrasound Transmission: Ultrasound requires a medium for transmission. In air, ultrasound propagates very inefficiently because the density and acoustic impedance of air are significantly different from most industrial materials. Water, as a transmission medium, has an acoustic impedance that closely matches many materials (such as metals, ceramics, composites, etc.), which helps reduce the reflection and scattering of ultrasound, ensuring effective signal transmission.

Reducing Signal Reflection: Without water, the interface between the ultrasound sensor and the object being inspected (usually air) would generate significant reflection, greatly reducing image quality and affecting inspection results. The addition of water helps reduce these reflections because the acoustic impedance of water is better matched to common industrial materials (like metals, plastics, composites), allowing ultrasound signals to penetrate the object more easily and improving image resolution.