Ultrasonic method and apparatus for detecting and identifying contamination such as ice on the surface of a structure

Apparatus for detecting and identifying the nature of a contaminant belonging to the group consisting of ice, water, defrosting liquids, slush and mixtures thereof covering a surface of a structure, comprising:

• a probe having
• a delay block of polysulfone with an interface apt to be placed flush with said surface of said structure, constituting an interface with any said contaminant, and with two faces, said faces having a same angle of inclination of from 40.degree. to 55.degree. relative to the interface,
• a transmission transducer oriented perpendicularly to one of said faces and in contact therewith;
• a reception transducer oriented perpendicularly to the other one of said faces and in contact therewith;
• energization means for applying an electrical energization pulse to the transmission transducer;
• and
• analysis means for comparing the amplitude and phase of an echo signal delivered by said reception transducer and due to an echo on the interface with a reference echo signal obtained when there is no contaminant on said interface;
• and
• storage means for storing said reference echo signal whereby the analysis means detects and identifies the nature of any contaminant present.

A method for detecting and identifying the type of contaminant on an outer surface of a structure, comprising the steps of:

• (a) directing a burst of incident ultrasound waves through a block of material to a surface of said block flush, with said outer surface and constituting an interface with any said contaminant present on said structure, said block constituting a delay line and having an acoustic impedance that is intermediate between impedances of liquids and the impedance of ice, the burst being directed at an oblique angle of incidence with respect to said interface;
• (b) receiving an echo formed at said interface;
• (c) comparing an amplitude and a phase of said echo with an amplitude and a phase of the incident ultrasound waves or with an amplitude and a phase of a reference echo as obtained from a clean said interface;
• and
• (d) identifying the type of contaminant, if present, from both comparisons of step (c).