Systems and methods for spectroscopic analyses of diamonds

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.

A portable spectroscopic analysis apparatus for distinguishing between colorless gems, the apparatus comprising:

• a sample holder to retain 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 of the gem;
• a first light source configured to emit a first primary beam, at an excitation wavelength greater than or equal to 550 nanometers (nm) and less than or equal to 680 nm, directed toward the analysis position to impact on the first side of the gem when the gem is in the sample holder, and to generate emission or diffusion of light;
• a second light source configured to emit a second primary beam, comprising ultraviolet (UV) light, wherein the second primary beam is directed toward the analysis position to impact on the first side of the gem;
• an optical focusing system configured to focus the light emitted or diffused by the first side of the gem in a secondary optical beam;
• a spectral dispersion device configured to collect the secondary optical beam downstream of the optical focusing system and configured to spatially disperse the collected secondary optical beam;
• a first photodetector device configured to collect the light spatially dispersed by the spectral dispersion device and configured to output a distribution of spectral intensity as a function of emission wavelength in a range of emission wavelengths greater than or equal to 600 nm and less than or equal to 950 nm;
• a second photodetector device, in front of the second side of the gem, configured to detect visible light so as to collect light transmitted through the gem;
• a film of material, fluorescent to the UV light, configured to move between a first position, between the second side of the gem and the second photodetector device, and a second position, external to a field of view of the second photodetector device;
• and
• a central processing unit connected to the first light source, the second light source, the first photodetector device, and the second photodetector device, wherein the central processing unit is configured to:
• activate the first light source to emit the first primary beam toward the analysis position;
• acquire from the first photodetector device the distribution of spectral intensity as the function of emission wavelength;
• analyze 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, establish that the gem is not a diamond and output an indication that the gem is not a diamond;
• and
• if, as the result of the first analysis, the Raman intensity peak is determined to be present, establish that the gem is a diamond and proceed with verifying whether the diamond absorbs the UV light, wherein the verifying whether the diamond absorbs the UV light comprises:
• deactivating the first light source and activating the second light source to emit the second primary beam toward the analysis position;
• positioning the film of material, fluorescent to the UV light, in the first position 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 detectable by the second photodetector device;
• acquiring, from the second photodetector device, 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 the 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.