# Research on Monocular-Vision-Based Finger-Joint-Angle-Measurement System
## 5 Experimental Verification
As shown in Figure 11, the minimum-knuckle-angle mean deviation was 0.27\({}^{\circ}\) and the maximum-knuckle-angle mean deviation was 1.38\({}^{\circ}\) for the nine volunteers using visual identifiers at different scales. The knuckle-angle deviations for the nine volunteers using visual identifiers at a scale of 1.5 mm were 0.43\({}^{\circ}\), 0.47\({}^{\circ}\), 0.58\({}^{\circ}\), 0.27\({}^{\circ}\), 0.45\({}^{\circ}\), 0.5\({}^{\circ}\), 0.5\({}^{\circ}\), 0.59\({}^{\circ}\), and 0.51\({}^{\circ}\), which were much smaller than the mean deviation of the knuckle angle when using other scales of visual identifiers. Therefore, the scale of a 1.5-millimeter visual marker was chosen as the test condition for the subsequent experiments. To verify the accuracy of the finger-abduction angle, three different finger-abduction-joint angles were measured using visual measures on nine volunteers, and the accuracy of the angles was verified using conventional methods. The results of the measurement of the three different abduction-joint angles are shown in Table 4. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Volunteer**} & **Mark on the** & & & & **Length of** & **Length of** \\  & **Scale** & & & & **Phalanx (mm)** & **Phalanx (mm)** \\ \hline \multirow{8}{*}{volunteer 6} & \multirow{8}{*}{1.5 mm} & 145.31 & 109.12 & 114.33 & 40.12 & 30.21 \\  & & 160.33 & 130.22 & 109.22 & 44.45 & 29.22 \\  & & 150.22 & 165.72 & 130.33 & 43.43 & 27.34 \\  & & 145.33 & 110.47 & 115.33 & 39.65 & 28.79 \\  & & 161.43 & 130.99 & 109.44 & 41.76 & 30.33 \\  & & 150.67 & 165.33 & 131.65 & 42.22 & 30.67 \\  & & 146.12 & 110.22 & 115.48 & 45.97 & 30.15 \\  & 2.5 mm & 158.91 & 130.21 & 110.77 & 42.71 & 31.33 \\  & & 149.23 & 163.47 & 131.22 & 42.45 & 29.78 \\ \hline \multirow{8}{*}{volunteer 7} & \multirow{8}{*}{1.5 mm} & 145.33 & 110.32 & 116.12 & 36.45 & 27.13 \\  & & 159.31 & 130.07 & 110.77 & 36.84 & 26.56 \\  & & 150.21 & 165.22 & 129.22 & 37.32 & 26.32 \\  & & 146.71 & 110.42 & 113.41 & 34.78 & 25.72 \\  & 2 mm & 160.12 & 130.65 & 110.89 & 37.77 & 28.23 \\  & & 151.14 & 164.31 & 130.22 & 37.96 & 27.45 \\  & & 145.42 & 110.31 & 114.21 & 39.03 & 29.81 \\  & 2.5 mm & 161.31 & 128.64 & 109.01 & 39.76 & 25.33 \\  & & 152.12 & 166.21 & 129.13 & 38.78 & 25.91 \\ \hline \multirow{8}{*}{volunteer 8} & \multirow{8}{*}{1.5 mm} & 145.32 & 110.77 & 114.57 & 43.15 & 27.49 \\  & & 160.74 & 129.22 & 110.10 & 41.33 & 28.27 \\  & & 151.12 & 165.33 & 129.38 & 44.54 & 27.39 \\  & & 145.72 & 110.31 & 116.66 & 42.56 & 29.72 \\  & & 159.21 & 131.72 & 110.07 & 42.33 & 27.59 \\  & & 150.56 & 166.77 & 130.33 & 41.12 & 28.23 \\  & & 145.32 & 110.07 & 115.21 & 44.45 & 30.02 \\  & 2.5 mm & 157.42 & 131.72 & 110.99 & 41.75 & 29.67 \\  & & 150.22 & 166.23 & 129.25 & 45.39 & 28.37 \\ \hline \multirow{8}{*}{volunteer 9} & \multirow{8}{*}{1.5 mm} & 145.31 & 110.23 & 115.76 & 35.46 & 23.57 \\  & & 160.22 & 130.74 & 110.55 & 34.90 & 24.88 \\ \cline{1-1}  & & 159.31 & 165.21 & 130.90 & 37.04 & 24.42 \\ \cline{1-1}  & & 146.13 & 111.31 & 114.31 & 36.24 & 25.56 \\ \cline{1-1}  & & 158.91 & 129.10 & 110.12 & 39.35 & 23.78 \\ \cline{1-1}  & & 149.01 & 165.12 & 131.14 & 37.67 & 24.33 \\ \cline{1-1}  & & 143.21 & 109.22 & 115.33 & 38.91 & 24.89 \\ \cline{1-1}  & 2.5 mm & 160.33 & 131.55 & 107.32 & 37.33 & 26.33 \\ \cline{1-1}  & & 151.33 & 165.77 & 129.22 & 37.57 & 23.91 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: _Cont._  
From Table 5, it can be seen that the time taken by the vision-based knuckle-angle-detection method is much less than that of the conventional knuckle-angle-detection method. This result was produced because the vision-based knuckle-angle-detection method not only enables the simultaneous measurement of multiple knuckles compared to the conventional knuckle-angle-detection method, but also increases the speed of the knuckle measurement and the speed at which the knuckle-angle data are recorded.