Variable-focus Liquid Lens Based on a Laterally-integrated Thermopneumatic Actuator

Abstract

We report a focal-length tunable liquid lens based on thermopneumatically driven fluidic pressure. The fluidic pressure is generated by deformation of an elastomeric diaphragm induced by thermopneumaticity from a laterally integrated microheater sealed within an air chamber. The pressure is transmitted by a confined liquid to a lens diaphragm through an internal fluid channel. The liquid filling under the lens diaphragm functions as a liquid lens for dynamic focusing with properties depending on the curvature of the deformed diaphragm. The diaphragm area of the air chamber is designed five times larger than that of the lens cavity to yield high focal-length tunability by amplified deflection of the lens diaphragm. With our method, we achieved excellent focal-length tunability from infinity (without an input current) to 4 mm (with an input current of 12 mA) with a lens aperture diameter of 2 mm.

Thermally actuated tunable liquid microlens with sub-second response time

“…Replacing gas, used as a working fluid in previous designs, 11,17,18 with liquid results in a simpler device construction since there is no need to encapsulate the working fluid separately from the liquid used in the optical part of the device. Effectively, the working fluid of the heat engine and the liquid used in the optical system are the same.…”

“…16 Recently, focus tunable lenses based on thermopneumatic actuators were reported. 17,18 This approach exploits the thermal expansion of an encapsulated gas, to move the liquid inside the lens, thus inducing a change in the lens surface profile. The thermopneumatic lens has an inherent simplicity since only a resistive element is needed to actuate the device.…”

“…Yet owing to the bi-directional heat pumping capability of the TE device, one can implement a controller with a relatively large overshoot, which in turn results in a much faster system compared to a resistive based heat pump. 17,18 In order to test the operation of the proposed design, a prototype was fabricated and placed on top of a printed object on a transparent film, while the resulting image was observed via a microscope. As the temperature of the water cavity varied from 20 C to 30 C, images acquired through the curved meniscus varied accordingly.…”

Optical Design and Optimization of a Micro Zoom System with Liquid Lenses

“…There are three main types of tunable-focus liquid lenses: liquid crystal lens [1][2], electrowetting effect based liquid lens [3][4][5] and liquid-filled membrane lens [6][7][8]. The electrowetting effect based liquid lens was first reported by the researchers of Philips Optical in 2003 in [3].…”

A liquid progressive multifocal lens adjusted by the deformation of a non-uniform elastic membrane due to the variation of liquid pressure

“…In addition, a liquid-filled tunable focus microlens was designed by using a membrane with different thickness between the central and peripheral region [8]. Besides, many kinds of liquid-filled lens with different actuators or control strategies were also designed in recent years, furthermore, the liquid tunable aspherical lenses are formed by liquid sealed with a non-uniform thickness membrane which could alleviate the edge clamping effect and reduce spherical aberration [9][10][11][12][13][14][15]. In order to decrease the influence of gravity to the performance of liquid lens, one of a method is using an in-plane pretention force to a membrane to take the place of surface tension and the other is using a non-uniform thickness profile of the flexible membrane [16,17].…”