CN119717091A

CN119717091A - A focal length switching liquid lens

Info

Publication number: CN119717091A
Application number: CN202311266760.2A
Authority: CN
Inventors: 李磊; 王梓源; 尹汶琪; 刘淑斌
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2023-09-28
Filing date: 2023-09-28
Publication date: 2025-03-28

Abstract

The present invention discloses a focal length switching liquid lens, wherein the lens structure includes window glass, lens cavity, microfluidic chip, transparent filling liquid I and transparent filling liquid II, the two filling liquids are immiscible, have different refractive indices and matched densities, and the window glass, lens cavity and microfluidic chip are coaxial. The microfluidic chip is made of ITO glass, a dielectric layer, a hydrophobic layer and a flexible electrode. The ITO electrode is designed as three annular belt parts, and voltage is applied to the ITO film layer and the flexible electrode attached to the hydrophobic layer to control the filling liquid I on the chip. The liquid lens provided by the present invention can be switched between four different optical focal lengths, and has the advantages of low cost, simple operation, fast response speed, and large zoom range. It can be widely used in scenes such as optical microscopes, photographic lenses, measuring instruments and medical optical devices.

Description

Focus switching type liquid lens

Technical Field

The present invention relates to a liquid lens, and more particularly, to a focus-switching liquid lens.

Background

At present, many optical systems are limited by the factors of lens size, and in the occasions of mobile phone lenses, vehicle-mounted cameras, medical microscopes and the like, the system size and the manufacturing cost are key factors in the optical systems, so that the light weight is a new trend of the development of the optical systems. The curvature radius or refractive index of the liquid lens, the liquid crystal lens and other self-adaptive lenses can be adjusted, so that the zoom imaging system is more compact and lighter. The liquid lens does not require moving parts to change the focal length and all elements are fixed, and the application of the liquid lens to the design and manufacture of an optical system is easy relative to a conventional solid lens. Liquid lenses have a variety of driving mechanisms, such as electrowetting, dielectrophoresis, mechanical wetting, electromagnetic control, etc., all of which are controlled by controlling the liquid to change its surface curvature to achieve the zoom function of the lens. The micro-fluidic technology can also realize the control of liquid, so that the micro-fluidic technology meets the requirement of light weight of a liquid lens.

The microfluidic technology can realize the generation, transportation, splitting, merging and the like of planar liquid drops, and with the establishment of a basic fluid manipulation technology, the electrowetting-based microfluidic device has important application in the research of various fields. The main idea is to provide a substrate with a series of individually addressable electrodes that can move the droplet along an arbitrary path according to an activation sequence where the electrodes are freely programmed, achieving a response to a tiny droplet on the order of milliseconds.

The liquid lens driven by the microfluidic technology can realize repeated switching of a plurality of focal lengths through directional movement of liquid drops, has the advantages of quick response, compact size, light weight, low manufacturing cost and the like, and plays an important role in scenes such as biological microscopy, video monitoring, laser radar and the like.

Disclosure of Invention

The invention provides a focal length switching type liquid lens, which is shown in figure 1. The lens structure comprises a microfluidic chip, a lens cavity, window glass, filling liquid I and filling liquid II, wherein the window glass, the lens cavity and the microfluidic chip are coaxial, and the microfluidic chip is shown in figure 2. The electrodes of the middle lens part are shown in figure 3 and are divided into four parts, namely a first ring electrode in the lens, a second ring electrode in the lens, a third ring electrode in the lens and an additional electrode in the lens, wherein the four parts are respectively connected to the bottom electrode glass outside the lens part, and each electrode part can be individually addressed. The overall structure of the microfluidic chip is shown in fig. 4. The bottom is transparent glass carved with customized electrode, the customized electrode is shown in figure 2 and figure 3, the electrode component is Indium Tin Oxide (ITO), the middle lens part of the ITO glass is plated with dielectric layer and hydrophobic layer with specific thickness, and the middle additional electrode is covered above the hydrophobic layer. The filling liquid in the cavity is filled liquid I, filled liquid II and filled liquid I from top to bottom in sequence, wherein the filled liquid I is colorless transparent conductive polar liquid, the filled liquid II is colorless transparent insulating nonpolar liquid, the filled liquid I and the filled liquid II are two liquids which are mutually insoluble, different in refractive index and matched in density, and the liquid-liquid surface formed between the two liquids can change the curvature radius to realize the change of the optical focal length.

In the initial state, when no voltage is applied to any electrode of the microfluidic chip, the bottom of the lower filling liquid I contacts with the microfluidic chip in the first ring electrode, as shown in fig. 5, at this time, the lens is in a concave lens mode, and light is refracted through the upper liquid-liquid surface and the lower liquid-liquid surface.

When voltage is applied to the first ring electrode and the middle additional electrode of the microfluidic chip, the electrowetting effect of the underfill liquid I occurs, the contact angle between the underfill liquid I and the microfluidic chip changes, and at the moment, the curvature of the liquid-liquid interface of the underfill liquid I and the filling liquid II changes, so that the focal power of the concave lens becomes larger, and the concave lens is switched from an initial state to a state 1, as shown in fig. 6.

When a voltage is applied to the second ring electrode and the middle additional electrode of the microfluidic chip, and the first ring electrode is removed, the underfill liquid I diffuses to the second ring electrode position of the chip due to the dielectric wetting effect, at this time, the curvature of the liquid-liquid interface between the underfill liquid I and the filling liquid II changes again, the focal power of the concave lens becomes larger again, and the concave lens is switched from the state 1 to the state 2, as shown in fig. 7.

When voltage is applied to the third ring electrode and the middle additional electrode of the microfluidic chip, the second ring electrode is removed, the bottom filling liquid I is split and finally converged at the position of the third ring electrode of the chip to form a circular ring shape, at the moment, the liquid-liquid interface of the bottom filling liquid I and the filling liquid II in the middle of the lens disappears, light rays are refracted through the liquid-liquid interface of the top filling liquid I and the filling liquid II, the focal power of the concave lens is increased again, and the concave lens is switched from the state 2 to the state 3, as shown in fig. 8.

If voltages are reversely applied to the first ring electrode, the second ring electrode, the third ring electrode, and the intermediate additional electrode, respectively, by the operations described above, the concave lens can be sequentially switched from the state 3 to the state 2, the state 1, and the initial state.

Preferably, the effective caliber D of the focal length switching liquid lens is more than or equal to 1mm, and D is less than or equal to 7.2mm.

Preferably, the filling liquid I and the filling liquid II in the focal length switching type liquid lens are two liquids which are insoluble, the filling liquid II is dielectric liquid, and the filling liquid I can use conductive solution or dielectric liquid.

Preferably, the focal length switching liquid lens may be driven by an electrowetting mechanism, or by a non-uniform electric field generated by the bottom customized electrode, via a dielectrophoresis effect.

Preferably, the drive electrode is outside the imaging cavity and on the same optical axis as the imaging cavity. The initial state, state 1 and state 2 of the focal length switching type liquid lens are three-phase liquid lenses, state 3 is a two-phase liquid lens.

Drawings

Fig. 1 is a schematic diagram of a front view cross-section structure of a focal length switching liquid lens.

Fig. 2 is an electrode schematic diagram of a focal length switching type liquid lens microfluidic chip.

Fig. 3 is an enlarged schematic view of the middle lens portion electrode of the microfluidic chip.

Fig. 4 is a schematic structural diagram of a microfluidic chip.

Fig. 5 is a schematic diagram of an initial state of the focal length switching liquid lens.

Fig. 6 is a schematic view of a state 1 of the focal length switching liquid lens.

Fig. 7 is a schematic view of a state 2 of the focal length switching liquid lens.

Fig. 8 is a schematic view of a state 3 of the focus switching liquid lens.

Fig. 9 is a schematic structural cross-sectional view of a wide-angle + tele optical system composed of a focus-switching liquid lens and a convex lens.

The graphic reference numerals in the above drawings are:

1 microfluidic chip, 2 lens cavity, 3 fill liquid I, 4 fill liquid II, 5 top window glass, 6 first ring electrode, 7 second ring electrode I, 8 second ring electrode II, 9 third ring electrode I, 10 third ring electrode II, 11 third ring electrode III, 12 third ring electrode IV, 13 intermediate additional electrode, 14 intermediate lens portion, 15 in-lens first ring electrode, 16 in-lens second ring electrode, 17 in-lens third ring electrode, 18 in-lens additional electrode, 19 glass sheet, 20 ITO electrode layer, 21 dielectric layer, 22 hydrophobic layer, 23 flexible electrode, it should be understood that the above figures are schematic only and not drawn to scale.

Detailed Description

In order to make the structure, function and technical scheme of the invention more clear, the matched embodiment is used for further describing the surface shape and diaphragm adjustable liquid lens in detail. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. Those skilled in the art will appreciate from the foregoing disclosure that many insubstantial modifications and variations of the invention are possible without departing from its scope.

The device structure of the invention is shown in the accompanying drawings 1 and 2, and comprises a1 micro-fluidic chip, a 2 lens cavity, 3 filling liquid I, 4 filling liquid II, 5 top window glass, 6 first ring electrodes, 7 second ring electrodes I, 8 second ring electrodes II, 9 third ring electrodes I, 10 third ring electrodes II, 11 third ring electrodes III, 12 third ring electrodes IV, 13 middle additional electrodes and 14 middle lens parts. The liquid lens cavity is 12mm in window glass diameter, 0.5mm in thickness, 10mm in lens cavity height, 12mm in outer diameter, 10mm in inner diameter, 60mm in micro-fluidic chip diameter and 1.1mm in thickness from top to bottom sequentially, the electrode adopts magnetic control ITO coating film, laser engraving is customized, and ITO coating film thickness is 185nm. The first ring electrode is circular, the diameter is 4mm, the second ring electrode is annular, the first ring electrode is divided into four areas, one group of diagonal sides are communicated to form a second ring electrode I, the other group of diagonal sides are communicated with a second ring electrode II, the inner diameter of the second ring electrode is 4.6mm, the outer diameter of the second ring electrode I is 6.6mm, the middle communication pin of the second ring electrode I surrounds a gap between the first ring electrode and the second ring electrode, the inner diameter of the second ring electrode I is 4.2mm, the outer diameter of the second ring electrode I is 4.4mm, the middle communication pin of the second ring electrode II surrounds a gap between the second ring electrode and the third ring electrode, the inner diameter of the second ring electrode II is 6.8mm, and the outer diameter of the second ring electrode I is 7mm. The third ring electrode is annular and divided into four areas, namely a third ring electrode I, a third ring electrode II, a third ring electrode III and a third ring electrode IV, wherein the inner diameter of the third ring electrode is 7.2mm, and the outer diameter of the third ring electrode is 9.6mm. A parylene layer is coated on an ITO film layer of the middle lens part of the microfluidic chip as a dielectric layer with the thickness of 3 mu m, and a Teflon layer with the thickness of 300nm is coated on the dielectric layer with a spin coater at 1500r/min as a hydrophobic layer. The middle additional electrode is coated with ITO film layer made of PET flexible material, and is adhered to the upper end of the hydrophobic layer, and the thickness is 0.05mm, as shown in figure 4. Wherein, the electrode is divided into two rings in the middle lens part, and the gaps of the first ring electrode, the second ring electrode and the third ring electrode at the bottom are respectively covered, the inner diameter of the first ring is 3.8mm, the outer diameter is 4.8mm, the inner diameter of the second ring is 6.4mm, and the outer diameter is 7.4mm. The lens cavity is filled with two mutually-incompatible liquids with different refractive indexes and matched densities, the filled liquid I is colorless transparent NaCl solution, the refractive index is 1.36, the Abbe number is 46, the filled liquid II is colorless transparent silicone oil, the refractive index is 1.58, and the Abbe number is 37.8, so that the three-phase water-oil-water lens is formed. The lens cavity is made of aluminum by polishing.

The working band adopted by the embodiment is 380 nm-760 nm. Taking a focal length switching type liquid lens as an example, a convex lens with focal power of +80d is placed at the rear end of the liquid lens, and the convex lens and the liquid lens form a wide angle +long focal optical system, as shown in fig. 9. When the liquid lens is in the initial state, no voltage is applied at this time, as shown in fig. 5. The contact angle between the bottom water and the microfluidic chip is 110 degrees, the curvature of the liquid-liquid surface formed by the bottom water and the oil is negative, the focal power of the liquid lens is about-140D, the effective caliber is 4mm, and the focal power of the whole optical system is-60D. When 100V _p-p AC (1 KHz) is applied to the first ring electrode and the middle additional electrode, the liquid lens is switched from the initial state to the state 1, as shown in figure 6, the contact angle between the bottom water and the microfluidic chip is about 45 degrees, the curvature of the liquid-liquid surface formed by the bottom water and the oil changes, the focal power of the liquid lens is about-63D, the effective caliber is 4mm, and the integral focal power of the optical system is +17D. When 100V _p-p AC (1 KHz) is applied to the second ring electrode and the middle additional electrode, the liquid lens is switched from state 1 to state 2, as shown in figure 7, the contact angle between the bottom water and the microfluidic chip is about 25 degrees, the curvature of the liquid-liquid surface formed by the bottom water and the oil changes, the focal power of the liquid lens is about-25D, the effective caliber is 6.6mm, and the integral focal power of the optical system is +55D. When 100V _p-p AC (1 KHz) was applied to the third ring electrode and the intermediate additional electrode, the liquid lens was switched from state 2 to state 3, as shown in fig. 8, at which time the bottom water was pulled to the rim and the effective liquid-liquid surface of the oil disappeared, at which time the optical power of the liquid lens was about-12D, the effective aperture was about 7.2mm, and the optical power of the optical system was +68d.

The liquid lens can be restored from state 3 to the original state by applying the same voltages in reverse order according to the above operations.

Claims

1. A focal length switching liquid lens, comprising: window glass, lens cavity, microfluidic chip, transparent filling liquid I and transparent filling liquid II, characterized in that the middle lens part of the microfluidic chip is designed as three ring electrodes, and each ring electrode can be addressed individually.

2. The focal length switching liquid lens according to claim 1 is characterized in that the filling liquid I and the filling liquid II are two immiscible liquids, the filling liquid II is a dielectric liquid, and the filling liquid I can be a conductive solution or a dielectric liquid.

3. The focus-switching liquid lens according to claim 1 is characterized in that when the filling liquid is a conductive-dielectric liquid, the driving mechanism is the electrowetting effect; when the filling liquid is a dielectric-dielectric liquid, the driving mechanism is the dielectrophoresis effect.

4 . The focus-switchable liquid lens according to claim 1 , wherein the effective aperture D is ≥ 1 mm and D is ≤ 7.2 mm.