Flexible zoom lens module with polyhedral cylindrical linear ultrasonic motor-actuated transparent elastomer

Traditional zoom lenses employ multiple solid lens elements and electromagnetic driving mechanisms. This results in complex structures and large sizes. These limitations significantly restrict their application in compact optical systems where miniaturization is critical. To address this issue, this paper presents a flexible zoom lens module. This module is driven by a cylindrical ultrasonic motor (CYUSM). The CYUSM comprises a stator, a hollow mover, and piezoelectric ceramic (PZT) elements. It acts as a direct-drive actuator to deform a transparent elastomeric lens axially. Polydimethylsiloxane (PDMS) was selected as the optical lens material. The precise linear motion of the CYUSM dynamically controls its surface curvature. This enables continuous adjustment of the focal length. We optimized the structural parameters of the CYUSM stator and the PDMS lens using ANSYS finite element analysis. This optimization aimed to achieve modal frequency degeneracy and high electromechanical coupling efficiency. Experimental characterization of the prototype demonstrated that the CYUSM could deliver a maximum output velocity of 1.21 mm/s and a thrust force of 5.4 N (under 43.3 kHz, 200 Vp). The optical performance was evaluated using ZEMAX. The results indicated a minimum focal length of 36.5 mm for the lens module. The experimentally measured focal length trend showed high consistency with the simulation results, thereby validating the design accuracy. The module employs a coaxial hollow structure to integrate the actuator and optical path, resulting in high integration, miniaturization, self-locking, and electromagnetic interference immunity.