1. Method of detecting and identifying substances or mixtures and/or determining their characteristics, said method comprising the steps of: irradiating an inspected object by pulse signals of fixed duration, receiving a signal reflected by the inspected object; amplifying and analog-to-digital converting the received signal and comparison of parameters of the converted signal to prerecorded reference values; and wherein the inspected object is irradiated by a single wave pulse with a frequency of 20 kHz to 200 MHz or a series of such pulses, the analogue-to-digital conversion of the received signal is up to at least 128 discrete values and followed by the steps of: forming of output detailing wavelet coefficients Di,k (where i varies from 1 to N) and of output approximating wavelet coefficients AN,k by means of fast discrete wavelet transformation of the digitized signal, performed by Mallet's pyramidal algorithm and orthogonal base functions, when using a suitable number of transformation levels N, comprising high frequency ( 4. i ) and low frequency ( 5. i ) wavelet filtering and binary decimation ( 6. i ) after each filtering at each level i, until at least one approximating and at least one detailing wavelet coefficient is obtained after the last transformation level, whereat only the approximating wavelet coefficients Ai,k are subjected to successive transformation by a wavelet filter at high frequencies ( 4. i ) and by a wavelet filter at low frequencies ( 5. i ) and binary decimation ( 6. i ), until the last level N is reached; filtering ( 7 ) of the output approximating AN,k and detailing Di,k wavelet coefficients up to preselected ones, according to the type of inspected object; and comparing the filtered approximating and/or detailing wavelet coefficients in their capacity of recognition attributes with preselected respective reference coefficients by classifying device ( 8 ), by a preselected image recognition method, where after, according to the comparison result, the presence and type is determined and/or the studied characteristics of the inspected object is determined.