PURPOSE: To quickly detect data and process the data in real time or quasi-real time by forming the ratio of each paired signals generated from an optical channel separator and comparing the values of the ratios with those of a series of values stored in a recording carrier.

CONSTITUTION: A laser source emits a beam of radiation F1 and the beam is reflected toward a target by a mirror system 3 and 5. The target excited by the beam emits back scattered radiation F2 and the radiation F2 is converged through an optical system 7 and 9. The converged beam F3 advances to a separator 11 and the separator 11 separates the beam F3 into (n) electric signals S1,..., Sn proportional to the intensity of fluorescence radiation detected in a preset specific band. The signals obtained by this method are supplied to a multiplexer 17 and a microprocessor 19. In order to execute the analysis of detected signals, the data stored in a memory 21 are also used.