A Novel Surface Acoustic Wave Sensor for Optical Lens Surface Dirt Detection

This paper presents a novel SAW sensor on ST-X quartz substrate with excellent long-term stability for on-line monitoring towards the dirt retention on the surfaces of the optical lenses. New designs are done on the SAW resonators acting as the feedback of the oscillator to decrease the insertion loss and to achieve single-mode control, resulting in superior long-term frequency stability of the oscillator.