# A Self-Color-Changing Film with Periodic Nanostructure for Anti-Counterfeit Application
## 3 Results and Discussion
### Validation of the Color  
This section confirms the accuracy of the proposed color analysis method by comparing with the experimental results. In 2020, [PERSON] et al. [38] created a security film with nanoparticles coated on top by shooting a laser onto them. The particle size was changed to the desired size by adjusting the laser intensity, which resulted in different colored particles. In [PERSON]'s experiments, the nanoparticles were similar in size to ours. Therefore, it is appropriate to compare our results with those of [PERSON] et al.'s. The transmittance and the color of the nanoparticles are measured by using an ultraviolet\(-\)visible-near-infrared. Our analysis begins by implementing the measured transmittance, following the steps in Figure 11. The results are summarized in Table 2. The experimental colors by [PERSON] et al. [38], compared to our results on the CIE chromaticity diagram, are shown in Figures 13 and 14. Since the true colors seen by the human eye are not those derived from RGB values, but rather those derived from CIE (x,y) values, we present a comparative analysis of color error that is obtained from the proposed color analysis method with the experimental colors from the CIE chromaticity diagram in Table 3.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample No.**} & \multicolumn{2}{c}{**\% Transmittance**} & \multicolumn{3}{c}{**\% Transmittance**} & \multirow{2}{*}{**Colors from RGB Analysis**} & \multirow{2}{*}{**Colors from Measurement**} \\  & & [38] & & & **(Normalized)** & & \\ \cline{2-2} \cline{5-8}  & **R** & **G** & **B** & **R** & **G** & **B** & \\ \hline
1 & 46.29 & 32.96 & 51.11 & 35.51 & 25.28 & 39.21 & \\
2 & 85.92 & 72.60 & 30.00 & 46.22 & 37.65 & 16.13 & \\
3 & 73.33 & 30.00 & 33.33 & 53.66 & 21.95 & 24.39 & \\
4 & 88.52 & 76.30 & 28.15 & 45.87 & 39.54 & 14.59 & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Results comparison.  
Figure 12: The CIE chromaticity diagram with the proposed color-changing nano-film colors.  
Figure 14: The CIE chromaticity diagram with mapping comparison from our proposed method and the measured color of photograph at laser intensity (2 nd scan) 200 J/cm\({}^{2}\) from [38].  
Figure 13: The CIE chromaticity diagram with mapping comparison from our proposed method and the measured color of photograph at laser intensity 60 J/cm\({}^{2}\) from [38].  
The CIE chromaticity diagrams in Figures 12-14 show colors as they would appear when viewed by the naked eye. The diagram divides color groups into regions on the diagram. Similar colors are close to each other in the same region. The dots in the figures show a comparison between the colors from the experiment and our proposed technique. The locations of these points are in the same color shade. In other words, the results show that the dots from our proposed method lie in close proximity to the ones from [PERSON]'s technique. This implies that our method can accurately convert transmittance to actual colors. We also learn that sampling only specific wavelengths (RGB) when analyzed with our technique can predict the overall characteristics of the transmittance curve. This technique can be applied to complex tasks that require a lot of effort to calculate or measure the transmittance characteristic. By calculating or measuring just three wavelengths (RGB), transmittance across the visible light regime can be mapped to true colors, without the need for all the transmittance values across the entire VIS regime.