## 3 Results
### Illumination  
The experimental method of this research is the principle of light reflection, so the intensity of light will indirectly affect the experimental value. The following statistics are mainly used to test the performance of the system under various lighting conditions, where the illuminance is below 200 lumens, 350-550 lumens, and above 600 lumens; the forehead and cheek measurements were taken at a measurement distance of 50 cm for analysis. The heart rate measured below represents the performance of this research on various light levels, and the data are expanded, as shown in Appendices 13 to 15, and its error statistics are shown in Table 3.  
As the experimental method used in this study was based on the principle of light reflection, the intensity of the light would indirectly affect the value of the experiment. The following statistics were mainly used to test the performance of the system under various illumination conditions, including below 200 lumens, 350 to 550 lumens, and above 600 lumens, respectively. The forehead and the forehead plus cheeks were measured at a distance of 50 cm for analysis. The following measured heart rates represent the performance of the system under different illumination conditions, and the error statistics are shown in the table.  
As shown in Table 3, it can be seen that the measurement is better in an environment with an illuminance of 350-550 lumens. In other environments with more extreme light, it is realized by turning off the lights and supplementing the light of the table lamp. It may be a deliberately created environment, so the error presented is relatively large.  
From the above, it can be seen that the light intensity is 350-550 lumens, the measurement distance is 50 cm, and the measurement of the forehead and cheek is the best  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Measurement Area**} & \multicolumn{2}{c}{**Measurement Standard**} & \multirow{2}{*}{**RMSE**} & \multirow{2}{*}{**MAPE**} & \multirow{2}{*}{\(\mathbf{R^{2}}\)} \\  & & & & \\ \hline \multirow{5}{*}{the forehead} & Heart Rate & 2.09 ppm & 2.092.6\% & 0.823737 \\  & SDNN & 1.18 ms & 3.33\% & 0.63904 \\ \cline{1-1}  & LF & 2.11\% & 2.86\% & 0.909543 \\ \cline{1-1}  & HF & 2.11\% & 4.133\% & 0.909543 \\ \hline \multirow{5}{*}{forehead} & Heart Rate & 5.01 ppm & 6.13\% & 0.284089 \\ \cline{1-1}  & SDNN & 2.804 ms & 9.4\% & 0.76545001 \\ \cline{1-1}  & LF & 4.96\% & 7.26\% & 0.6345715 \\ \cline{1-1}  & HF & 4.96\% & 15.2\% & 0.6345715 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Comparison of measuring forehead and forehead plus cheek performance at 50 cm.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Illumination**} & \multirow{2}{*}{**Measurement Items**} & \multirow{2}{*}{**RMSE**} & \multirow{2}{*}{**MAPE**} & \multirow{2}{*}{\(\mathbf{R^{2}}\)} \\ \cline{1-1}  & & & & \\ \hline Below 200 lumens & Heart Rate & 5.84 ppm & 6.4\% & 0.2843022 \\
350–550 lumens & Heart Rate & 1.73 ppm & 1.66\% & 0.7890768 \\
600 lumens or more & Heart Rate & 6.58 ppm & 7.4\% & 0.1442480 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Measuring performance comparison of different lights.  
environment for this research. The accuracy of various physiological parameters is RMSE of heart rate 1.968 bpm and MAPE 2%, SDNN's RMSE is 1.85 ms, MAPE is 4.87%, HF's RMSE is 1.77%, MAPE is 3.95%, LF's RMSE is 1.77%, and MAPE is 2.425%. As a result, an illumination condition of 350 to 550 lumens was suitable for measurement. The other extreme light conditions were implemented by turning off the lights and supplementing them with reading lamps. It was possible that because the environment was deliberately created, the errors were relatively large. From the above, an illumination level of 350 to 550 lumens and a measuring distance of 50 cm was optimal for this study to capture the forehead and cheeks for measurement, and the accuracy of each physiological parameter was the RMSE of the heart rate.