High stability liquid lens with optical path modulation function

Rapid depth estimation based on a key electrowetting liquid-lens with electrically adjusted imaging focus

An effective method for rapidly performing depth estimation using a type of electrowetting liquid-lens is proposed. The liquid-lens is architectured by directly coupling a cylindrical copper sidewall electrode and a top ITO electrode, leading to a dual-mode lens adjusted electrically, including a beam diverging mode and a beam converging mode, and also an intermedium phase retard state. By increasing the applied signal voltage from 0 to 120 V, the focus of the liquid-lens presents a wide dynamic range of (-∞, -128.6 mm) ∪ (45.6 mm, +∞). The key performances of the liquid-lens, such as the focus tunable electrically and an element response duration of less than 5 ms, are evaluated experimentally. By sweeping the signal voltage applied over the liquid-lens coupled with an arrayed CMOS sensor to form an imaging setup, a sequence of images leading to a focal stack is acquired. Considering the dual-mode character of the liquid-lens, the depth of field of the imaging equipment mainly based on the liquid-lens can be remarkably extended by further utilizing the phase retard effect in the transition region between the positive and negative focus. A rapid algorithm for aligning the focal stack and then eliminating the scene parallax is also achieved.

Dielectric Liquid Microlens Array with Tunable Focal Length Based on Microdroplet Array Created via Dip-Coating Method

A dielectric liquid microlens array (LMA) with a tunable focal length was fabricated by using a microdroplet array generated through the dip-coating method. The process began with treating the octadecyltrichlorosilane (OTS) layer with selective UV/O3 irradiation for 20 min to establish a hydrophilic-hydrophobic patterning surface. The substrate was subsequently immersed in glycerol and then withdrawn at a constant rate to create a microdroplet array. Upon filling the cell with matching oil (SL5267) and placing it within a square array of a 200 μm diameter glycerol microdroplet array, the LMA was produced. The focal length ranged from approximately -0.96 to -0.3 mm within a voltage range of 0 to 60 Vrms. The glycerol microdroplets, characterized by their shapes, sizes, curvatures, and filling factors, can be precisely controlled by designing an OTS patterning or adjusting the dip-coating speed. This approach offers a rapid and high-throughput method for preparation. Our approach to fabricating tunable LMA offers several advantages, including simplicity of fabrication, uniform structural properties, cost-effectiveness, polarization independence, and excellent optical performance. These focus-tunable LMAs hold significant potential for applications in image processing, 3D displays, medical endoscopy, and military technologies.

Three-phase electrowetting liquid lens with deformable liquid iris

Inspired by the arrangement of iris and crystalline lens in human eyes, we propose a three-phase electrowetting liquid lens with a deformable liquid iris (TELL-DLI). The proposed electrowetting liquid lens has three-phase fluid: air, conductive liquid, and dyed insulating liquid. The insulating liquid is distributed on the inner wall of the chamber in a ring shape. By applying voltage, the contact angle is changed, so that the dyed insulating liquid contracts towards the center, which is similar to the contraction of iris and the function of crystalline lens muscle in human eyes. The variation range of focal length is from -451.9 mm to -107.9 mm. The variation range of the aperture is from 4.89 mm to 0.6 mm. Under the step voltage of 200 V, the TELL-DLI can be switched between the maximum aperture state and the zero aperture state, and the switching time is ∼150/200 ms. Because of the discrete electrodes, TELL-DLI can regionally control the shape and position of the iris, and switch between circle, ellipse, sector, and strip. The TELL-DLI has a wide application prospect in imaging systems, such as microscopic imaging system, and has the potential to be applied in the field of complex beam navigation.

Adaptive liquid lens with controllable light intensity

An adaptive liquid lens with controllable light intensity is demonstrated, which can modulate both light intensity and beam spot size. The proposed lens consists of a dyed water solution, a transparent oil, and a transparent water solution. The dyed water solution is used to adjust light intensity distribution by varying the liquid-liquid (L-L) interface. The other two liquids are transparent and designed to control the spot size. In this way, two problems can be solved: the inhomogeneous attenuation of light can be achieved through the dyed layer, and a larger optical power tuning range can be achieved through the two L-L interfaces. Our proposed lens can be used for homogenization effects in laser illumination. In the experiment, an optical power tuning range from - 44.03 m^-1 ∼ + 39.42 m^-1 and an ∼ 89.84% homogenization level are achieved. Our proposed lens may also ease the vignetting problem in imaging systems.

Design and fabrication of a focus-tunable liquid cylindrical lens based on electrowetting

In this study, a focus-tunable liquid cylindrical lens based on electrowetting was designed and fabricated. The cylindrical cavity usually used in common electrowetting zoom spherical lenses was replaced by a 20 mm × 10 mm × 8 mm cuboid cavity, in which the interface of two liquids formed a toroid owing to the electrowetting effect. The proposed liquid cylindrical lens can serve as either a converging or diverging lens with the response time under 110 ms by changing the supplied voltage. The zoom lens we fabricated worked stably under 0-110 V voltage for a long time, guaranteeing that the focal length of the liquid cylindrical lens can range within (-∞, -148.36 mm) ∪ (697.21 mm, +∞). By combining the liquid lens that we designed with a simple fixed cylindrical lens, a cylindrical lens system with an arbitrary focal length suitable for various tasks in beam manipulation can be realized.

Design, fabrication, and characterization of an optofluidic phase modulator array based on the piezoelectric effect

In this paper, an optofluidic phase modulator array based on the piezoelectric effect is designed, fabricated, and characterized. This array is composed of three piezoelectric ceramics arranged on the vertices of an equilateral triangle. A transparent liquid fills the inner cavity of the ceramics. Due to the inverse piezoelectric effect, the length of the transparent liquid is changed at different voltages, which contributes to the optical phase modulation. According to experiment results, it is found that our modulator arrays exert continuous optical phase adjustment ability. When the voltage ranges from 0 to 135 V, the relative length variation reaches up to 9.286 µm, and consequently our proposed modulator arrays perform about 9.685 π optical phase modulation.

Variable-focus liquid lens based on electrically responsive fluid

In this work, an adaptive liquid lens using a novel transparent electrically responsive fluid, dibutyl adipate (DBA), is demonstrated. The DBA liquid lens with a hemispherical plano-convex shape can change its curvature according to the application of various input voltages. More specifically, when an external direct current (DC) electric field is applied to the DBA liquid, the charges that are injected from the cathode move along with the DBA molecules toward the anode and accumulate on the surface of the anode. When the DC electric field is removed, the shape of the DBA liquid is recovered to its original state. This electrostatic force induces the deformation of the DBA liquid lens within a concentric annular anode electrode. In addition, the focal length of our system is increased from a value of approximately 7.5 mm to 13.1 mm when the voltage is changed from 0 to 100 V. Interestingly, the resolution of our DBA liquid lens can reach a value of ∼28.5 lp/mm. The proposed DBA liquid lens exhibits high optical transmittance (∼95%), good thermal stability (20-100°C), simple structure, and an excellent imaging property, which implies that the DBA liquid is a promising candidate for fabricating novel adaptive liquid lenses.