Ultra-wide varifocal imaging with selectable region of interest capacity using Alvarez lenses actuated by a dielectric elastomer

Abstract

A remarkable feature of Alvarez lenses is that a wide focal length tuning range can be achieved using lateral displacement rather than commonly used axial translation, thus, reducing the overall length of varifocal imaging systems. Here, we present novel lens elements based on Alvarez lenses actuated by a dielectric elastomer (DE). The proposed lens elements are composed of the varifocal component and the scanning component. Based on the proposed lens elements, an imaging system is built to realize ultra-wide varifocal imaging with a selectable region of interest. The lens elements have a variable focus function based on an Alvarez lens structure and a DE actuator and a scanning function based on the DE-based four-quadrant actuators. The large deformation generated by the DE actuators permits the lateral displacement of the Alvarez lenses up to 1.145 mm. The focal length variation of the proposed varifocal component is up to 30.5 times, where the maximum focal length is 181 mm and the minimum focal length is 5.94 mm. The rise and fall times of the varifocal component are 160 ms and 295 ms, respectively. By applying different voltages on four-quadrant actuators, the scanning component allows the varifocal component to move in different directions and endows the varifocal component with a selectable region of interest imaging capability. The scanning range of the scanning component is 17.57°. The imaging resolution of the imaging system is approximately 181 lp/mm. The system developed in the current study has the potential to be used in consumer electronics, endoscopy, and microscopy in the future.