# Rapid and Precise Zoom Lens Design Based on Voice Coil Motors with Tunnel Magnetoresistance Sensors
## 5 Discussion and Conclusions  
It is of great practical significance to integrate VCMs and TMR sensors into zoom lens systems to realize rapid zooming and precise positioning. In particular, the proposed designs solve the time delay problem of high-magnification zoom lenses and are suitable \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Test Points**} & \multicolumn{3}{c}{**Target Position 1 (0 mm)**} & \multicolumn{2}{c}{**Target Position 2 (38 mm)**} \\  & \(\downarrow\)* & \(\uparrow\) & \(\downarrow\) & \(\uparrow\) \\ \hline \multirow{5}{*}{Positioning Deviation (mm) for Cycles \(j=1,2,3,4,5\)} & 1 & \(-0.001500\) & \(-0.000100\) & \(-0.000900\) & 0 \\  & 2 & 0 & 0 & \(-0.001000\) & 0 \\ \cline{1-1}  & 3 & 0 & 0 & \(-0.001900\) & 0.000200 \\ \cline{1-1}  & 4 & \(-0.004500\) & \(-0.004800\) & 0.000300 & 0.000100 \\ \cline{1-1}  & 5 & 0 & 0 & 0.002300 & 0.000300 \\ \hline \hline \end{tabular}
* Movement direction.  
\end{table} 
Table 1: Measurement results for positioning accuracy under ISO 230-2-1997. Figure 13: Zooming time for (**a**) rapid zoom lens with VCMs and (**b**) traditional zoom lens with step motors. for applications in zoom lenses that move from a wide-area search to high-resolution target identification. The entire process of realizing a novel zoom lens with VCMs and TMR sensors was undertaken, including goal establishment, structural design, control system design, prototype assembly, and performance testing. Rapid zooming and precise positioning were our main goals, and this system exhibits potential universality for other large-travel zoom lenses if the functions are implemented by changing the drive mechanism without altering the original optical design. Furthermore, system performance requirements like the zoom travel distance and time were established through practical applications and can be customized on demand. In movement trajectory planning, the design principles emphasize smooth acceleration and deceleration throughout the motion process, with no sudden changes in acceleration and maintaining a certain stabilization time. Notably, the total zoom travel time (0.2 s) of our design is less than the required time (0.3 s) because it is necessary to leave enough time for signal transmission and processing within the closed-loop control at a later point. In addition, the VCM structure needed to be as compact as possible in order to ensure its functionality, which guided our design of the magnetic circuit and energized coil. The driving force \(F_{drive}\) = 2.076 N for the VCM was obtained from the designed coil and magnetic field strength simulation results, which far exceeded the peak driving force requirement (0.338 N), indicating that the VCM is capable of meeting the minimum zoom time requirement. The redundant gap between the simulated and required driving forces can meet the demands of other usage scenarios, such as the vertical motion of the zoom group during gravitational acceleration, even when the driving elements are heavy. Moreover, harsh environments should be considered because the temperature may affect the resistance of the coil, thus affecting the driving force. Significantly, precise positioning is realized through a high-precision magnetic-scale closed-loop control system, in which a single magnetic grating unit measures about 2.5 \(\upmu\)m, ensuring that the positioning control accuracy of the zoom group meets the 5 \(\upmu\)m requirement. In order to test and verify the reliability of our design, a rapid zoom lens prototype was assembled and experiments to measure the zoom time and positioning accuracy were performed.