Method for determining an optical property (p) of a sample, comprising the following steps: i) illumination of a surface of the sample, using a light beam produced by a light source, so as to form, on the surface of said sample, an elementary illumination zone, corresponding to the part of said surface lit by said light beam; ii) acquisition, using a photodetector, of a backscattering signal (S 1 (λ),...,S N (λ)), at a wavelength (λ), representative of a radiation backscattered (52 1...52 F), at said wavelength, by the sample at a distance (D 1,...,D N), called backscattering distance, from said elementary illumination zone; iii) selection of a calibration factor f n 1 λ corresponding to said backscattering distance and to said wavelength (λ); iv) application of the calibration factor f n 1 λ, f n i λ to the backscattering signal (S 1 (λ),...,S N (λ)), so as to obtain a quantity of interest (R 1 (λ),...,R N (λ)), associated with said backscattering distance; v) determination of at least one optical scattering or absorption property (p) of the sample, at said wavelength, using said quantity of interest; the method being characterized in that it comprises: vi) repetition of the steps iv) to v), by updating the calibration factor f n i + 1 λ, as a function of said optical property (p) determined in the step v), the calibration factor being replaced by a calibration factor ( f n,p ( λ)) selected as a function of said optical property (p), the steps iv) to v) being repeated until the deviation between the optical properties (p i, p i+1) determined during two successive iterations (i, i+1) is below a predetermined threshold or up to a predetermined number of iterations; and in that the calibration factor is updated by using a library comprising calibration factors for different optical properties (p), at least one calibration factor being measured by obtaining a ratio between: - an estimation of a quantity R calib − n model λ representative of a backscattered radiation emanating from a surface of a calibration sample, at said wavelength, at the backscattering distance ( D n) from the elementary illumination zone of said calibration sample, when the calibration sample is illuminated by said light beam; - a measurement of said quantity ( R calib-n (λ))., using a backscattering signal ( S calib - n (λ)) detected by said photodetector, at said wavelength, the calibration sample being illuminated by said light beam. i) illumination of a surface of the sample, using a light beam produced by a light source, so as to form, on the surface of said sample, an elementary illumination zone, corresponding to the part of said surface lit by said light beam; ii) acquisition, using a photodetector, of a backscattering signal (S 1 (λ),...,S N (λ)), at a wavelength (λ), representative of a radiation backscattered (52 1...52 F), at said wavelength, by the sample at a distance (D 1,...,D N), called backscattering distance, from said elementary illumination zone; iii) selection of a calibration factor f n 1 λ corresponding to said backscattering distance and to said wavelength (λ); iv) application of the calibration factor f n 1 λ, f n i λ to the backscattering signal (S 1 (λ),...,S N (λ)), so as to obtain a quantity of interest (R 1 (λ),...,R N (λ)), associated with said backscattering distance; v) determination of at least one optical scattering or absorption property (p) of the sample, at said wavelength, using said quantity of interest; - an estimation of a quantity R calib − n model λ representative of a backscattered radiation emanating from a surface of a calibration sample, at said wavelength, at the backscattering distance ( D n) from the elementary illumination zone of said calibration sample, when the calibration sample is illuminated by said light beam; - a measurement of said quantity ( R calib-n (λ))., using a backscattering signal ( S calib - n (λ)) detected by said photodetector, at said wavelength, the calibration sample being illuminated by said light beam.