FIELD: photometry. SUBSTANCE: modulated light flux is iteratively substituted at each step by source of displacement flux forming across output of photodetector signal equal to sum of signals created by source of displacement flux of previous step of iteration and modulated by source of constant light flux which makes it feasible to move working point of photodetector to the right along axis of light flux by value equal to value of flux from modulated source of constant light flux. At next step modulated flux is restored and light flux equal to next sum of fluxes is substituted. After this operation is repeated many times. At each step of iteration sought-for point of light characteristic is defined as sum of reactions of photodetector to light flux from modulated source of constant light flux with value of flux from source of displacement flux multiple of it. Device for realization of technique has modulated source 14 of constant light flux, source 15 of displacement flux, photodetector 1, adder 2, amplifier 3 of signal of photodetector, integration and storage unit 7, first and second analog keys 4 and 5, first and second buffer stages 12 and 13, selector 8 of analog signal, storage 6, digital-to-analog converter 11, analog-to-digital converter 9 and microprocessor 10. EFFECT: increased accuracy of measurement. 2 cl, 1 dwg
