US Patent 7957223 Ultrasonic ranging in the near zone

An ultrasonic ranging device for ultrasonic ranging in the near zone. The device may include a transducer for generating an ultrasonic signal and for detecting an echo signal. The device may also include a processor for calculating the distance to a target object based on a first time period defined by a first set of ultrasonic signals when the target object is located outside the near zone and a second time period defined by a second set of ultrasonic signals when the target object is located within the near zone. The processor may also adjust the amplitude of the generated ultrasonic signal until the first set of ultrasonic signals is detected at the transducer.