LiuLab
Spectrometer
LiuLab Sectrometer (US Patents 7,652,755, 7,388,656 and one in pending)
The US patented LiuLab
spectrometer is the most advanced gemological instrument with the artificial
intelligence for spectral measurement, color measurement and color grading of
colored gemstones and colored diamonds. The patented dual integrating sphere
optical arrangement (Fig. 1) provides the best possible illuminating and viewing
geometry under a controlled measurement environment for measuring the spectrum
and color of faceted colored diamonds and gemstones. The LiuLab spectrometer is
a vital instrument for gemological laboratories to grade color and identify
gemstones and colored diamonds.
Figure 1. The dual integrating sphere optical arrangement.
The color grading
software can simulate the human visual color grading method to grade the color
by “considering” the parameters of faceted gemstones, such as shape, size,
refractive index etc, through a neural network. The spectrometer is calibrated
by a patented novel three-step method. The Gem spectrometer can accurately and
precisely measure the spectral reflectance, calculate the CIELAB data, determine
the average color grade, and then provide the true color grade by the fuzzy
logical method. The average color represents the color of the gem material, and
the true color represents the face-up color, i.e. the “Key color” for faceted
colored gemstones, and the “Characteristic color” for colored diamonds.
The LiuLab spectrometer
is also designed to measure the color of any rough gemstones, minerals and
crystals. In addition, the measured spectral reflectance can be used for
spectroscopic research and gem identification.
Figure 2. The color measurement and color grading screen for colored gemstones;
1. shape; 2. size; 3. RI; 4. fluorescence; 5. CIELAB data; 6. average color
grade; 7. true color grade; 8. color monitor button; 9. color measurement button
and 10. spectral reflectance.
The Gem Spectrometer is
a high precision instrument developed for laboratory applications, but designed
in a compact size for portable . The compact design and universal power input
make the spectrometer very versatile for being used by gemological researchers,
gemologists, mineralogists, diamond and gemstone buyers in diamond and gemstone
mines, jewelry markets, gemstone factories, trade shows, jewelry stores, and any
place as long as there is a power outlet. The spectrometer can be carried in a
suitcase with all necessary accessories.
Figure 2 shows the
measurement window of the LiuLab spectrometer. The measured spectral reflectance
of a faceted aquamarine has two reflectance bands centered at about 480 nm and
over 760 nm, and an absorption maximum at about 615 nm. The calculate hue angle,
saturation and lightness in the CIELAB color space is 235.140, 74.8
and 16.24. The average color of the measured aquamarine is Strong Light
Greenish Blue, and the color grade is Vivid Greenish Blue.
Figure 3. The color measurement and color grading screen for colored diamonds.
The average color of the diamond is Fancy Intense Greenish Blue, and the color
grade is Fancy Vivid Greenish Blue.
A colored diamond color
grading plug-in software is provided for the LiuLab Spectrometer. The software
can automatically calculate the
“Characteristic color” for colored diamonds, and determines the “Fancy Color
Grade” using the fuzzy logic algorithm and a look-up-table. The color grading
accuracy and precision of colored diamonds by the spectrometer is much better
than that by human color graders. Figure 3 shows a typical measurement window
for color measurement and color grading of colored diamonds.
The measured spectral
reflectance is very useful for colored diamond identification. Depending on the
color and the absorption peaks of the colored centers in the visible region,
such as the N3, H3, H4, 550 nm, NV and GR1 centers, most colored diamonds can be
identified as natural, synthetic, treated or other mixed type by this
spectrometer.
The LiuLab spectrometer
can be used to grade the color of jadeites, and to identify dyed only jadeites
(C type) as well as impregnated and dyed jadeites (B+C type) (see Figure 4).
Since FTIR cannot identify dyed jadeites, the LiuLab spectrometer is more useful
than a FTIR spectrophtometer, besides the LiuLab spectrometer can grade the
color.
Figure 4. Spectra of dyed and natural green jadeites measured by the LiuLab
Spectrometer.
The LiuLab spectrometer
is an indispensable instrument for all gemological laboratories due to that it
can not only measure and grade color of all colored diamonds and gemstones, but
also measure the spectrum for gem identification and gemological research. A
gemological laboratory can do most, if not all, color grading and identification
tasks by the LiuLab spectrometer without other instruments, such as Roman
spectrometer, IR spectrometer, XRF spectrometer, and other more expensive
instruments.
1.
Y. Liu, Apparatus and method for color measurement and color grading of
diamonds, gemstones and the like, US Patent No. 7,652,755, 2010.
2.
Y. Liu, Apparatus and method for color measurement and color grading of
diamonds, gemstones and the like, US Patent Publication No. 2008/0204705.
3.
Y. Liu, Method and system for color grading of gemstones, US Patent No.
7,388,656, 2008.
4.
Y. Liu, Optical filter for CIE daylight simulator, US Patent No.
7,378,784, 2008.
5.
Y. Liu and K. Hurwit, The TrueGemColor system: A new computer color
imaging system based on a uniform CIELAB color space for color grading of
gemstone, Z. Dt. Gemmol. Ges. Vol. 57, No. 3-4, pp. 133-142, 2008.
6.
Y. Liu et al., Identification of dyed jadeite using visible reflection
spectra, J. Gemmology, Vol. 31, No. 5-8, pp. 181-184, 2009.
Liu
Research Laboratories, LLC
