Sonar distance sensing apparatus

Claim 1

Distance sensing apparatus comprising a measurement signal generator including exciting means for generating pulsed electrical signals and a transducer responsive to the exciting means for radiating pulsed sonic or ultrasonic measurement signals along a measurement path, said transducer also receiving and converting into return electrical signals reflections of said measurement signals from a remote surface back along the measurement path, a time measurement device for determining the time lapse between radiation of a measurement signal pulse and receipt of a reflected signal, thereby to provide a distance signal which will be representative of the path distance between the apparatus and said surface, an amplifier for increasing the amplification of said return electrical signals as a function of the time elapsed from radiation of a measurement signal pulse, said amplifier including an attenuator and means coupled to said attenuator for reducing the attenuation of the attenuator as a function of time elapsed from the radiation of a measurement signal pulse and a sound lens or sound horn provided adjacent to the transducer to create a narrow directional beam sonic or ultrasonic signal, said beam having a projection angle of about 3° or less.