FIELD: mining industry. SUBSTANCE: increased efficiency of extraction of low-contrast investigated objects is achieved by induction (focusing) of electromagnetic field on to investigated object (layer) with the aid of harmonic exponentially decaying current signal which parameters - angular frequency, amplitude of second extremum, number of passes through zero are established depending on conditions of provision of maximum relative signal of transition process from investigated field. EFFECT: increased efficiency of extraction of low-contrast investigated objects. 2 cl, 2 dwg
