Electrically Tunable Lenses: A Review.

Michele Ghilardi,Leihao Chen,James J. C. Busfield,Federico Carpi

doi:10.3389/frobt.2021.678046

Michele Ghilardi, Leihao Chen + Show 2 more

Open Access

https://doi.org/10.3389/frobt.2021.678046

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Abstract

Optical lenses with electrically controllable focal length are of growing interest, in order to reduce the complexity, size, weight, response time and power consumption of conventional focusing/zooming systems, based on glass lenses displaced by motors. They might become especially relevant for diverse robotic and machine vision-based devices, including cameras not only for portable consumer electronics (e.g. smart phones) and advanced optical instrumentation (e.g. microscopes, endoscopes, etc.), but also for emerging applications like small/micro-payload drones and wearable virtual/augmented-reality systems. This paper reviews the most widely studied strategies to obtain such varifocal “smart lenses”, which can electrically be tuned, either directly or via electro-mechanical or electro-thermal coupling. Only technologies that ensure controllable focusing of multi-chromatic light, with spatial continuity (i.e. continuous tunability) in wavefronts and focal lengths, as required for visible-range imaging, are considered. Both encapsulated fluid-based lenses and fully elastomeric lenses are reviewed, ranging from proof-of-concept prototypes to commercially available products. They are classified according to the focus-changing principles of operation, and they are described and compared in terms of advantages and drawbacks. This systematic overview should help to stimulate further developments in the field.

Highlights

Research on electrically tunable optical lenses has been growing in the past couple of decades
Such tunable lenses might become especially relevant for a diversity of robotic and machine vision-based devices
It is worth noting that this Review aims at covering only strategies that ensure controllable focusing of multi-chromatic light, with spatial continuity in wavefronts and focal lengths, as required for visible-range imaging applications

Summary

INTRODUCTION

Research on electrically tunable optical lenses has been growing in the past couple of decades. Its application to electrode-coated polymeric chambers filled in with dielectric liquids has led to new kinds of actuators, proposed for soft robotics (Kellaris et al, 2018) and tactile displays (Leroy et al, 2020) They have been applied to tune the focal length of oilfilled lenses, according to the concept described in Figure 5E: electrical charging of metalized plastic membranes creates attraction between them, resulting in a progressive closure (zipping effect) of their initial angle and a concomitant displacement of the interposed insulating fluid; as a result, the curvature of a transparent elastomeric membrane in the lens chamber is increased (Hartmann et al, 2020). In some cases current tunable lenses might already be practically usable, whilst, in other cases, greater potentialities offered by less mature technologies might encourage further developments

CONCLUDING REMARKS

DATA AVAILABILITY STATEMENT

Findings

Objective