A prior art computerised ultrasonic examination is first performed by moving an ultrasonic probe over the surface of an object, emitting short pulses of ultrasonic energy into the material. Combined digital position and echo pulse signals are electronically stored, processed and used for the display of video images presenting accumulated echo amplitude data in circular patterns associated with selected sectional planes through the object. The results of the examination are then analysed and evaluated by means of a mathematical model, able to produce imaginary digital data simulating the progression and reflection of sound pulses emitted by the ultrasonic probe. Imaginary echo signals from imaginary point reflection sources corresponding to selected individual flaw image pixels are then compared with the actual echo pulse signals electronically stored, and in cases of identical sound path lengths, the corresponding actual echo pulse signals are deleted from the memory. By such successive elimination of individual flaw echo signals from the totality of echo signals received, it becomes possible to analyse complex flaw combinations in successively revised sectional images, removing individual flaw images one by one. The peak amplitude values of deleted echo pulse signals may further be re-stored, processed and used for the display of video sectional and projection flaw images of drastically improved quality and precision.
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