Focal length switching type liquid lens

Abstract

The invention discloses a focal length switching type liquid lens, the lens structure comprises window glass, a lens cavity, a micro-fluidic chip, a transparent filling liquid I and a transparent filling liquid II, the two filling liquids are mutually insoluble, different in refractive index and matched in density, and the window glass, the lens cavity and the micro-fluidic chip share the same optical axis. The micro-fluidic chip is made of ITO glass, a dielectric layer, a hydrophobic layer and a flexible electrode, the ITO electrode is designed into three annular belt parts, and the liquid I filled in the chip is controlled by applying voltage to the ITO film layer and the flexible electrode attached to the hydrophobic layer. The liquid lens provided by the invention can be switched in four different focal power states, and has the advantages of low cost, simplicity in operation, high response speed, large zoom range and the like. The method can be widely applied to optical microscopes, photographic lenses, measuring instruments, medical optical devices and other scenes.

Description

Technical Field

[0001] The present invention relates to a liquid lens, and more particularly to a focal length switchable liquid lens. Background Art

[0002] Many optical systems are now restricted by the size of the lens. In mobile phone lenses, car cameras, medical microscopes and other occasions, system size and manufacturing cost are key factors in an optical system. Therefore, lightweighting has become a new trend in the development of optical systems. Adaptive lenses such as liquid lenses and liquid crystal lenses make zoom imaging systems more compact and lightweight due to their adjustable curvature radius or refractive index. Liquid lenses do not require moving parts to change the focal length, and all components are fixed. It is easier to apply liquid lenses to the design and manufacture of optical systems than traditional solid lenses. Liquid lenses have a variety of driving mechanisms, such as electrowetting, dielectrophoresis, mechanical wetting, electromagnetic control, etc., all of which achieve the zoom function of the lens by controlling the liquid to change its surface curvature. Microfluidic technology can also realize the manipulation of liquids, which makes microfluidic technology more in line with the needs of lightweight liquid lenses.

[0003] Microfluidics can realize the generation, transportation, splitting and merging of planar droplets. With the establishment of basic fluid manipulation technology, microfluidics devices based on electrowetting have important applications in various fields. The main idea is to provide a substrate with a series of individually addressable electrodes, which can move droplets along any path according to the activation sequence of the electrodes that can be freely programmed, and achieve response to tiny droplets at the millisecond level.

[0004] Liquid lenses driven by microfluidic technology can achieve repeated switching of multiple focal lengths by directional movement of droplets. They have the advantages of fast response, compact size, light weight, and low manufacturing cost. They play an important role in scenarios such as biological microscopy, video surveillance, and lidar. Summary of the invention

[0005] The present invention proposes a focal length switching liquid lens, as shown in the attached Figure 1 The lens structure includes a microfluidic chip, a lens cavity, a window glass, a filling liquid I, and a filling liquid II. The window glass, the lens cavity and the microfluidic chip are coaxial. The microfluidic chip is as shown in the attached Figure 2 The electrodes of the middle lens are shown in the attached Figure 3 As shown in the figure, it is divided into four parts, namely the first ring electrode in the lens, the second ring electrode in the lens, the third ring electrode in the lens and the additional electrode in the lens. The four parts are connected to the bottom electrode glass outside the lens part respectively, and each electrode part can be addressed separately. The overall structure of the microfluidic chip is shown in the attached figure. Figure 4The bottom is a transparent glass with customized electrodes engraved on it. The customized electrodes are shown in the attached Figure 2 , Attachment Figure 3 As shown, the electrode component is indium tin oxide (ITO), and a dielectric layer and a hydrophobic layer of a specific thickness are plated on the middle lens part of the ITO glass, and an intermediate additional electrode is covered on the hydrophobic layer. The filling liquids in the cavity are filling liquid I, filling liquid II, and filling liquid I from top to bottom, among which filling liquid I is a colorless, transparent, conductive polar liquid, and filling liquid II is a colorless, transparent, insulating, non-polar liquid. Filling liquid I and filling liquid II are two immiscible liquids with different refractive indices and matching densities. The liquid-liquid surface formed between the two liquids can change the radius of curvature to achieve a change in the optical focal length.

[0006] 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 the microfluidic chip within the first ring electrode. Figure 5 As shown, the lens is in concave lens mode at this time, and the light is refracted through the upper and lower liquid-liquid surfaces.

[0007] When voltage is applied to the first ring electrode and the middle additional electrode of the microfluidic chip, the bottom filling liquid I undergoes electrowetting effect, and the contact angle between the bottom filling liquid I and the filling liquid II changes. At this time, the curvature of the liquid-liquid interface between the bottom filling liquid I and the filling liquid II changes, so the optical power of the concave lens increases, and the concave lens switches from the initial state to state 1. Figure 6 shown.

[0008] When 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 bottom filling liquid I diffuses to the position of the second ring electrode of the chip due to the dielectric wetting effect. At this time, the curvature of the liquid-liquid interface between the bottom filling liquid I and the filling liquid II changes again, and the focal length of the concave lens increases again. The concave lens switches from state 1 to state 2. Figure 7 shown.

[0009] When voltage is applied to the third ring electrode and the middle additional electrode of the microfluidic chip and the second ring electrode is removed, the bottom filling liquid I is split and finally converges at the position of the third ring electrode of the chip to form a ring shape. At this time, the liquid-liquid interface between the bottom filling liquid I and the filling liquid II in the middle of the lens disappears, and the light is refracted through the liquid-liquid interface between the top filling liquid I and the filling liquid II. The focal length of the concave lens increases again, and the concave lens switches from state 2 to state 3. Figure 8 shown.

[0010] If voltages are applied in reverse to the first ring electrode, the second ring electrode, the third ring electrode and the intermediate additional electrode respectively through the operations described above, the concave lens can be switched from state 3 to state 2, state 1 and the initial state in sequence.

[0011] Preferably, the effective aperture of the focus-switchable liquid lens is D≥1mm and D≤7.2mm.

[0012] Preferably, the filling liquid I and the filling liquid II in the focal length switching liquid lens 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.

[0013] Preferably, the focus-switchable liquid lens can be driven by an electrowetting mechanism, or by a non-uniform electric field generated by a customized bottom electrode through a dielectrophoresis effect.

[0014] Preferably, the driving electrode is outside the imaging cavity and has the same optical axis as the imaging cavity. The initial state, state 1 and state 2 of the focal length switching liquid lens are three-phase liquid lenses, and state 3 is a two-phase liquid lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Attached Figure 1 This is a schematic diagram of the front-view cross-sectional structure of a focal-switching liquid lens.

[0016] Attached Figure 2 Schematic diagram of the electrodes of the focal-switching liquid lens microfluidic chip.

[0017] Attached Figure 3 This is an enlarged schematic diagram of the electrodes in the middle lens part of the microfluidic chip.

[0018] Attached Figure 4 Schematic diagram of the structural composition of the microfluidic chip.

[0019] Attached Figure 5 Schematic diagram of the initial state of the focal-switching liquid lens.

[0020] Attached Figure 6 Schematic diagram of state 1 of the focal length switching liquid lens.

[0021] Attached Figure 7 Schematic diagram of state 2 of the focal length switching liquid lens.

[0022] Attached Figure 8 Schematic diagram of state 3 of the focal length switching liquid lens.

[0023] Attached Fig. 9 It is a schematic diagram of the structural cross-section of a wide-angle + telephoto optical system composed of a focal length switching liquid lens and a convex lens.

[0024] The diagram numbers in the above-mentioned drawings are:

[0025] 1 microfluidic chip, 2 lens cavity, 3 filling liquid I, 4 filling 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 part, 15 first ring electrode in lens, 16 second ring electrode in lens, 17 third ring electrode in lens, 18 additional electrode in lens, 19 glass sheet, 20 ITO electrode layer, 21 dielectric layer, 22 hydrophobic layer, 23 flexible electrode. It should be understood that the above drawings are only schematic and not drawn to scale. DETAILED DESCRIPTION

[0026] In order to make the structure, function and technical solution of the present invention more clearly understood, a liquid lens with adjustable surface shape and aperture is further described in detail in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Those skilled in the art may make some non-essential improvements and adjustments to the present invention based on the above invention content, which still fall within the scope of protection of the present invention.

[0027] The device structure of the present invention is as shown in the attached Figure 1 , Attachment Figure 2As shown, the structure includes: 1 microfluidic chip, 2 lens cavity, 3 filling liquid I, 4 filling 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 part. From top to bottom, the liquid lens cavity has a window glass diameter of 12 mm and a thickness of 0.5 mm, a lens cavity height of 10 mm, an outer diameter of 12 mm, an inner diameter of 10 mm, a microfluidic chip diameter of 60 mm, a thickness of 1.1 mm, and the electrode is magnetron ITO coated and customized by laser engraving, and the ITO film thickness is 185 nm. The first ring electrode is circular with a diameter of 4mm. The second ring electrode is annular and divided into four areas. One group of diagonal edges are connected to form the second ring electrode I, and the other group of diagonal edges are connected to the second ring electrode II. The inner diameter of the second ring electrode is 4.6mm and the outer diameter is 6.6mm. The middle connecting pin of the second ring electrode I surrounds the gap between the first ring electrode and the second ring electrode, with an inner diameter of 4.2mm and an outer diameter of 4.4mm. The middle connecting pin of the second ring electrode II surrounds the gap between the second ring electrode and the third ring electrode, with an inner diameter of 6.8mm and an outer diameter of 7mm. The third ring electrode is annular and divided into four areas, namely the third ring electrode I, the third ring electrode II, the third ring electrode III, and the third ring electrode IV. The inner diameter of the third ring electrode is 7.2mm and the outer diameter is 9.6mm. A layer of parylene is coated on the ITO film layer of the middle lens part of the microfluidic chip as a dielectric layer with a thickness of 3μm. A layer of Teflon is coated on this dielectric layer with a spin coater at 1500r / min as a hydrophobic layer with a thickness of 300nm. The intermediate additional electrode is made of PET flexible material coated with ITO film, which is pasted on the top of the hydrophobic layer with a thickness of 0.05mm. Figure 4 As shown. In the middle lens part, this electrode is divided into two rings, covering the gaps between the first ring electrode, the second ring electrode and the third ring electrode at the bottom respectively. The inner diameter of the first ring is 3.8mm and 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 immiscible liquids with different refractive indices and matching densities. The filling liquid I is a colorless and transparent NaCl solution with a refractive index of 1.36 and an Abbe number of 46. The filling liquid II is a colorless and transparent silicone oil with a refractive index of 1.58 and an Abbe number of 37.8, forming a three-phase water-oil-water lens. The lens cavity is made of polished aluminum.

[0028] The working wavelength band adopted in this embodiment is 380nm~760nm. Taking the focal length switchable liquid lens as an example, a convex lens with an optical power of +80D is placed at the rear end of the liquid lens to form a wide-angle + telephoto optical system with the liquid lens, as shown in the attached figure. Fig. 9 When the liquid lens is in the initial state, no voltage is applied. Figure 5As shown. The contact angle between the bottom water and the microfluidic chip is 110°, and the curvature of the liquid-liquid surface formed with the oil is negative. At this time, the focal length of the liquid lens is about -140D, the effective diameter is 4mm, and the overall focal length of the optical system is -60D. Apply 100V p-p When AC (1KHz) is applied to the first ring electrode and the middle additional electrode, the liquid lens switches from the initial state to state 1. Figure 6 As shown, at this time, the contact angle between the bottom water and the microfluidic chip is about 45°, and the curvature of the liquid-liquid surface formed with the oil changes. At this time, the focal length of the liquid lens is about -63D, the effective diameter is 4mm, and the overall focal length of the optical system is +17D. Apply 100V p-p When AC (1KHz) is applied to the second ring electrode and the middle additional electrode, the liquid lens switches from state 1 to state 2. Figure 7 As shown, at this time, the contact angle between the bottom water and the microfluidic chip is about 25°, and the curvature of the liquid-liquid surface formed with the oil changes. At this time, the focal length of the liquid lens is about -25D, the effective diameter is 6.6mm, and the overall focal length of the optical system is +55D. Apply 100V p-p When AC (1KHz) is applied to the third ring electrode and the middle additional electrode, the liquid lens switches from state 2 to state 3. Figure 8 As shown, at this time, the bottom water is pulled to the edge, and the effective liquid-liquid surface with the oil disappears. At this time, the optical focal length of the liquid lens is about -12D, the effective aperture is about 7.2mm, and the overall optical focal length of the optical system is +68D.

[0029] By applying the same voltage in reverse order according to the above operation, the liquid lens can be restored from state 3 to the initial state.

Claims

1. A focal length switchable 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 switchable liquid lens according to claim 1, characterized in that: Filling liquid I and filling liquid II are two immiscible liquids, filling liquid II is a dielectric liquid, and filling liquid I can use a conductive solution or a dielectric liquid.

3. The focal length switchable liquid lens according to claim 1, 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 focal length switchable liquid lens according to claim 1, characterized in that: The effective diameter D is ≥ 1mm and D is ≤ 7.2mm.

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