Method and apparatus for acoustic energy identification of objects

Abstract

Acoustic energy is used to detect and identify objects buried in soil by imaging acoustic energy reflected from the soil and buried objects. Acoustic energy is injected into soil at an oblique angle relative to the surface of the soil, reflected and received. Signals representative of the reflected energy are processed to generate image signals used to generate images representative of the reflected energy. Objects buried within the soil are identified by viewing the images. In one embodiment, obliquely oriented acoustic energy signals are carried from a source to a soil sample by a first duct and reflections of that energy are carried to a receiver within an adjacent second duct. The ducts acoustically isolate the source from the receiver. A beveled end of the first duct and the second duct are supported above the soil sample for noncontact operations. In another embodiment, an acoustic energy source is obliquely supported upon and forced into engagement with soil in a reservoir. The reservoir is placed in contact with soil to be probed to effect a soil 'impedance match' for oblique injection of acoustic energy into the soil. An acoustic energy receiver contacts the soil adjacent to the reservoir to receive acoustic energy reflected from the soil and objects buried within the soil. Pulse compression increases penetration depth. To compensate for soil attenuation characteristics, frequency-swept sinusoidal acoustic energy pulses are preferably amplitude modulated to have an exponentially changing envelope.