The disclosure is directed to a system for variably refracting, and is transparent for, ultrasound as well as for light. By choosing liquids with the right optical and acoustical properties, it is possible to variably refract (including focusing and deflecting or steering) ultrasound while not affecting the refraction of light, or vice versa. Two lenses in series, or preferably one lens, allow for variably refracting ultrasound and light.