Patent ID: 11906437
Assignee: UNIVERSITà DEGLI STUDI DI MILANO - BICOCCA
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 5:
6. A spectroscopic analysis method for distinguishing between colorless gems, the method comprising:
positioning a gem in an analysis position, wherein the analysis position exposes a first side of the gem and a second side of the gem, opposite to the first side;
directing a first primary beam, emitted by a first light source at an excitation wavelength greater than or equal to 600 nanometers (nm) and less than or equal to 680 nm, toward the analysis position to impact on the first side of the gem and to generate emission or diffusion of light;
focusing and spatially dispersing the light emitted or diffused by the first side of the gem;
detecting the spatially dispersed light and producing a distribution of spectral intensity as a function of emission wavelength using a first photodetector device in a range of emission wavelengths greater than or equal to 660 nm and less than or equal to 900 nm;
acquiring from the first photodetector device the distribution of spectral intensity as the function of emission wavelength; and
analyzing the distribution of spectral intensity as the function of emission wavelength to determine a presence or absence of a Raman intensity peak, corresponding to a difference in wavenumbers between the light emitted or diffused by the first side of the gem and the excitation wavelength, equal to 1332 cm−1;
if, as a result of this first analysis, the Raman intensity peak is determined to be absent, establishing that the gem is not a diamond and outputting an indication that the gem is not a diamond; and
if, as a result of the first analysis, the Raman intensity peak is determined to be present, establishing that the gem is a diamond and proceeding with verifying whether the diamond absorbs ultraviolet (UV) light, wherein verifying whether the diamond absorbs the UV light comprises:
deactivating the first light source and activating a second light source configured to emit a second primary beam comprising the UV light toward the analysis position to impact on the first side of the gem;
positioning a film of material, fluorescent to the UV light, at the second side of the gem so that the second primary beam, transmitted through the gem, interacts with the film of material, fluorescent to the UV light, to generate visible light; and
acquiring, using a second photodetector device, the visible light emitted by the film of material, fluorescent to the UV light, to output a fluorescence signal representative of the UV light transmitted through the gem and analyzing the fluorescence signal to determine whether fluorescence intensity is greater than, less than, or equal to a predetermined transmission threshold value;
if, as a result of this second analysis, the fluorescence intensity is determined to be less than or equal to the predetermined transmission threshold value, establishing that the gem is a type I natural diamond and outputting an indication that the gem is a natural diamond; and
if, as a result of the second analysis, the fluorescence intensity is determined to be greater than the predetermined transmission threshold value, establishing that the gem is a type II diamond and outputting an indication that the gem is a type II diamond.