FIELD: optoelectronic instrumentation, high-speed diffractometers. SUBSTANCE: characteristic feature of invention lies in recording of central part of diffraction distribution out of narrow slit with the help of multielement photodetector, in quantization and computation of amplitude spectrum of significant harmonics whose amplitude exceeds specified threshold normalized to amplitude of first harmonic with the aid of discrete Fourier transform of readings of signals of multielement photodetector, in computation of coefficients of linear function approximating significant harmonics of amplitude spectrum, in calculation of boundary frequency as quotient of coefficients of approximating function and in computation of quasi-period as quantity reciprocal to boundary frequency. EFFECT: increased speed of measurement. 2 dwg
