Square-Wave Driven Ultrasonic Liquid Crystal Optical Lenses

Conventional optical lenses only have one focal point. Whereas compound lens systems with multiple lenses and mechanical actuators are used in modules to focus on near and far objects. Camera modules with these systems tend to be bulky and have a slow time response. Electrically-controllable varifocal lenses will accelerate the development of compact photographic devices with high-speed responses. Here, we discuss an ultrasound varifocal liquid crystal (LC) lens that consists of an LC layer between two glass discs and an ultrasound transducer. The orientation of nematic LC molecules could be controlled by acoustic radiation forces, and the lens could change the refractive index distribution and its focal length by ultrasound vibration by utilizing the high LC liquidity and optical anisotropy. The effects of input waveforms on the optical characteristics of the ultrasonic LC lens were investigated in an industrial setting. We applied sinusoidal and square waves at the resonant frequency of the lenses to assess the impact on the optical characteristics. Those characteristics were largely similar. However, slight differences were observed in the vibrational distributions on the lens substrate, indicating that the lens could be controlled by a square-wave drive.