Optimization method for improving focal power of liquid lens

Abstract

The invention discloses an optimization method for improving the focal power of a liquid lens, and belongs to the field of liquid lenses. The method specifically comprises the following steps: (1) screening drugs by virtue of a material physical property database, selecting polyelectrolyte and electrolyte mixed with the polyelectrolyte, and preparing polyelectrolyte mixture solution combinations with different blending ratios; (2) extracting fluid viscosity data of all combined liquids through a viscosity experiment; (3) extracting spectral data of the characteristic group liquid through a Raman spectrum experiment; (4) determining the electrowetting effect of all combined liquids by means of an electrowetting contact angle determination method, and analyzing and selecting an optimal liquid combination by combining viscosity and spectral data; and (5) manufacturing a liquid lens by using the optimal liquid combination and measuring focal power data of the liquid lens in a continuous voltage interval. By means of the optimization method, the high-performance conductive liquid of the electrowetting liquid lens is obtained, and finally the optimal liquid lens with the large focal power tuning range and the small driving voltage is obtained.

Description

Technical Field

[0001] The present invention belongs to the field of liquid lenses, and more specifically, relates to an optimization method for improving the optical power of a liquid lens. Background Art

[0002] Optical systems are gradually developing towards lightweight and integrated directions. Liquid lenses have been widely studied and applied in the field of optical devices due to their tunable focal length. Liquid lenses use liquid as optical material and achieve focal length tunability by changing the curvature of the liquid surface, making the structure of the optical system simpler and lighter.

[0003] With the development of imaging technology, the demand for high-power, light-weight, and small-volume tunable optical devices has increased significantly in application scenarios such as optical microscopy and biomedicine. In order to achieve functional integration and rapid adjustment, electrowetting liquid lenses are mostly used. Their advantages are fast response speed and light volume, but their disadvantage is that they are difficult to meet the demand for high power. In addition, the commonly used conductive liquids in electrowetting liquid lenses are saline and similar simple electrolyte solutions. Liquid lenses composed of such liquids usually cannot achieve higher power, which is not conducive to the further application of electrowetting liquid lenses. Therefore, in-depth research on high-power liquid lenses and their materials is very necessary, which is conducive to the further development and application of miniaturized and lightweight optical systems. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of the present invention is to provide an optimization method for improving the optical focal length of a liquid lens based on a polyelectrolyte mixture solution, aiming to prepare and select a high-performance liquid lens conductive liquid through this method to obtain an electrowetting liquid lens with a large optical focal length tuning range and a small driving voltage.

[0005] To achieve the above object, the present invention provides a method for optimizing the optical power of a liquid lens, comprising the following steps:

[0006] (1) Screening the drugs required for the mixture with the help of a material property database, that is, polyelectrolyte and electrolyte mixed therewith, and preparing multiple groups of polyelectrolyte mixture solutions with different blending ratios by changing the relative proportions of the mixture at a fixed solute fraction;

[0007] (2) extracting and analyzing the fluid viscosity data of the polyelectrolyte mixture solutions of all the above combinations at high shear rates through viscosity measurement experiments;

[0008] (3) extracting and analyzing the spectral data of the liquids in the characteristic ratio groups in all combinations through laser Raman spectroscopy experiments;

[0009] (4) Using the electrowetting contact angle measurement method, the electrowetting effect of all liquid combinations is measured, and the viscosity and spectrum data are combined for comprehensive analysis to select the optimal liquid combination and measure its optical properties;

[0010] (5) Using the optimal liquid combination selected, an electrowetting liquid lens is produced and its optical power data is measured.

[0011] Beneficial effect: The present invention uses the above-mentioned optimization method and multidisciplinary experiments to verify that the polyelectrolyte mixture solution can improve the optical focal length performance of the electrowetting liquid lens when used as a conductive liquid, and obtains the optimal polyelectrolyte mixture solution and its corresponding ratio range through the above-mentioned optimization selection, and finally obtains an electrowetting liquid lens with a large optical focal length tuning range and a small driving voltage.

[0012] Preferably, in the process of using the drug to prepare the polyelectrolyte mixture solution, the polyelectrolyte mixture solution needs to contain at least one polyelectrolyte and one to five electrolytes mixed therewith.

[0013] Preferably, the fluid parameters involved in the multidisciplinary experimental approach used to verify the properties of the liquid include: viscosity, spectral data and contact angle number.

[0014] Preferably, in the viscosity test, all the liquid combinations are taken at 10-100 s. -1 The average viscosity in the high shear rate range is taken as the fluid viscosity data.

[0015] Preferably, in the spectral experiment, the polyelectrolyte content difference between the selected liquids of each characteristic ratio group should be no less than 5%, and the spectral data of the liquids are measured by a laser Raman spectrometer in the excitation band of 488~633nm.

[0016] Preferably, an ammonium polyphosphate and potassium chloride mixed solution is selected as the conductive liquid of the liquid lens, the mass fraction of ammonium polyphosphate in the conductive liquid is not less than 10%, and the total mass fraction of ammonium polyphosphate and potassium chloride is 20%, the insulating liquid of the liquid lens is colorless transparent silicone oil, the insulating liquid and the conductive liquid are immiscible and have matching densities.

[0017] Beneficial effects: The selection of conductive liquid for liquid lens not only takes into account the influence of density, transmittance, refractive index and Abbe number of the fluid itself, but also comprehensively considers the macroscopic viscosity properties, microscopic spectral performance and angle of electrowetting contact angle of the fluid, so that the optimal liquid combination obtained by optimization selection can produce more obvious electrowetting phenomenon while having excellent optical properties.

[0018] Preferably, polyelectrolytes with low polymerization degree and metal small molecule electrolytes are selected for aqueous phase blending, and the total solute mass fraction and different blending ratio combinations are set according to actual experiments for blending and preparation. The solution properties are characterized at the macro and micro levels by viscosity and spectrum, and the angle data of the electrowetting contact angle are used to comprehensively analyze and select the material with the optimal electrowetting effect.

[0019] Beneficial effects: For polyelectrolyte materials with different properties, the optimal blended solutions corresponding to different polyelectrolyte materials can be obtained by changing the total solute mass fraction, the relative proportion combination of the blended drugs, or the material combination of the blended drugs, making this optimization method have excellent universality.

[0020] Compared with the prior art, the above technical solution proposed by the present invention can achieve the following beneficial effects.

[0021] 1. The optimization method for improving the optical focal length of a liquid lens based on a polyelectrolyte mixture solution provided by the present invention verifies through multidisciplinary experiments that the polyelectrolyte mixture solution can improve the optical focal length performance of an electrowetting liquid lens when used as a conductive liquid, and the optimal polyelectrolyte mixture solution and its ratio range are obtained by the above optimization selection.

[0022] 2. The optimization method for improving the optical focal length of a liquid lens based on a polyelectrolyte mixture solution provided by the present invention, the selection of the conductive liquid for the liquid lens not only takes into account the influence of the density, transmittance, refractive index and Abbe number of the fluid itself, but also comprehensively considers the macroscopic viscosity properties and microscopic spectral performance of the fluid, so that the optimal liquid combination obtained by the optimization selection has excellent optical properties and is easy to drive.

[0023] 3. The optimization method for improving the optical focal length of a liquid lens based on a polyelectrolyte mixture solution provided by the present invention, the selection of the conductive liquid for the liquid lens not only takes into account the influence of the density, transmittance, refractive index and Abbe number of the fluid itself, but also takes into account the angle of the electrowetting contact angle of the fluid, so that the optimal liquid combination obtained by the optimization selection can produce a more obvious electrowetting phenomenon and can meet the needs of practical applications.

[0024] 4. The optimization method for improving the optical focal length of a liquid lens based on a polyelectrolyte mixture solution provided by the present invention can obtain the optimal liquid lens conductive liquid material suitable for different types of materials by selecting different blended electrolyte materials, changing the relative proportion of blended drugs and increasing the number of blended electrolytes, so that the optimization method has excellent universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic flow chart of an optimization method for improving the optical power of a liquid lens based on a polyelectrolyte mixture solution provided by the present invention.

[0026] Figure 2 These are the Raman spectra of liquid 1, liquid 5 and liquid 7 at an excitation wavelength of 532 nm in the spectral experiment.

[0027] Figure 3 Schematic diagram of the initial contact angle and the contact angle after power application in the electrowetting effect experiment.

[0028] Figure 4 This is a schematic diagram of the three-dimensional cross-sectional structure of the liquid lens provided by the present invention.

[0029] Figure 5 A schematic diagram of the liquid surface of the liquid lens provided by the present invention when no power is applied.

[0030] Figure 6 This is a schematic diagram of the liquid surface of the liquid lens provided by the present invention after voltage is applied.

[0031] Figure 7 A line graph comparing the optical power of the liquid lens provided by the present invention and a conventional liquid lens.

[0032] Figure 8 The transmittance spectrum of the optimal polyelectrolyte mixture solution provided by the present invention in the visible light band (400~800nm).

[0033] Fig. 9 The transmittance spectrum of the optimal polyelectrolyte mixture solution provided by the present invention in the 200-1400nm band. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and 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. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The performance of electrowetting liquid lens is mainly related to the material type of conductive liquid and its corresponding comprehensive physical and chemical properties. Therefore, the present invention proposes an optimization method for improving the optical power of liquid lens based on polyelectrolyte mixture solution, such as Figure 1 As shown, it includes the following steps:

[0036] (1) Using the material property database, the drugs required for the mixture are screened, i.e., polyelectrolytes and electrolytes mixed therewith. Under a fixed solute fraction, the relative proportion of the mixture is changed to prepare several groups of polyelectrolyte mixture solutions with different blending ratios. Taking ammonium polyphosphate and potassium chloride as an example, all the prepared liquid combinations are shown in Table 1.

[0037] Table 1 Liquid combination index value Ammonium polyphosphate mass (g) Potassium chloride mass (g) Distilled water volume (mL) 1 0.25 1.75 8.00 2 0.50 1.50 8.00 3 0.75 1.25 8.00 4 1.00 1.00 8.00 5 1.25 0.75 8.00 6 1.50 0.50 8.00 7 1.75 0.25 8.00

[0038] (2) Through viscosity measurement experiments, a modular intelligent rotational rheometer was used to measure and extract the viscosity of all combined liquids at high shear rates (10~100s -1 ) data on the viscosity variation with shear rate, and the average viscosity value within the rate range is calculated as the fluid viscosity data for evaluating the viscosity of the liquid. The calculation results are shown in Table 2;

[0039] Table 2 Liquid combination index value 1 2 3 4 5 6 7 Average viscosity (mPa·s) 1.035 1.065 1.142 1.304 1.316 1.412 1.425

[0040] (3) A laser Raman spectrometer is used to extract spectral data, and characteristic ratio groups are selected from all liquid combinations for measurement. The polyelectrolyte content difference between the selected characteristic ratio groups must be no less than 5%. Three liquids, namely liquid 1, liquid 5 and liquid 7, from the above liquid combination are selected as characteristic ratio groups for Raman spectral measurement, and the Raman spectra of the three characteristic ratio groups are compared and analyzed. Figure 2 As shown, the excitation wavelength used in this embodiment is 532nm;

[0041] (4) With the help of the electrowetting contact angle measurement method, all the combined liquids are treated as conductive liquids to measure the electrowetting effect, and the viscosity and spectrum data are combined for comprehensive analysis to select the optimal liquid combination. In the initial state, the initial contact angle θ0 of each conductive liquid is 165°. After applying the same voltage, the contact angle θ of each conductive liquid after power-on will decrease due to the electrowetting effect. The angle change is shown in the figure below. Figure 3 As shown, the angle data of the contact angle θ after power-on corresponding to all combinations of liquids after applying a sinusoidal signal of 80 Vrms DC (50 Hz) are shown in Table 3. The angle of the contact angle after power-on and the above data on viscosity and spectrum can be combined to select the optimal polyelectrolyte mixture solution. The specific ratio range is: the mass fraction of ammonium polyphosphate in the mixed solution is not less than 10%, and the total mass fraction of ammonium polyphosphate and potassium chloride is 20%;

[0042] Table 3 Liquid combination index value 1 2 3 4 5 6 7 Contact angle θ after power-on (°) 79 75 70 62 63 63 62

[0043] (5) The optimal polyelectrolyte mixture solution selected above was used to make an electrowetting liquid lens, and the optical power data of the lens in a continuously changing voltage range (0-45 V) was measured by a focal meter, as shown in Table 4.

[0044] Table 4 Voltage (V) 0 10 15 20 25 30 35 40 45 Optical power (D) -37.97 -37.66 -33.09 -26.96 -17.78 -9.19 0.67 9.36 18.71

[0045] Wherein, the structure of the liquid lens is as follows Figure 4 As shown, 1 window glass, 2 filling liquid I, 3 filling liquid II, 4 lens cavity, 5 extension electrode, 6 cavity electrode. The lens length is 5.75 mm, the diameter is 11 mm, and the effective aperture is 6.4 mm. The lens cavity, cavity electrode and the center of the liquid-liquid surface are coaxial. Among them, the upper part of the lens cavity and the lower part of the cavity electrode are both circular window glasses with a diameter of 8 mm and a thickness of 0.8 mm. The length, width and thickness of the two groups of symmetrical extension electrodes on the outside are 1.5 mm, 1.2 mm and 0.5 mm respectively. The length of the lens cavity is 4.45 mm, the outer diameter is 11 mm, and the inner wall of the lens cavity is a cylinder with a diameter of 6.4 mm. The cavity electrode is connected to the bottom of the lens cavity. The length of the cavity electrode is 1.3 mm, the outer diameter is 11 mm, and the inner diameter is 6.4 mm. The lens cavity is filled with two immiscible liquids with matching densities. The filling liquid I is colorless and transparent silicone oil with a refractive index of 1.556 and an Abbe number of 39, which is located in the upper layer. Filling liquid II is the optimal polyelectrolyte mixture solution selected, which is colorless and transparent, with a refractive index of 1.362 and an Abbe number of 46, and serves as the conductive liquid of the lower layer. The density of filling liquid I and filling liquid II is 1.15 g / cm 3 The liquid lens is an electrowetting liquid lens. The curvature of the liquid-liquid surface formed between two immiscible liquids is changed by voltage to achieve tunable optical focal length. The liquid surface shapes before and after power-on are as follows: Figure 5 , 6 shown.

[0046] In order to verify the beneficial effect of the optimization method provided by the present invention, a liquid lens made of the optimal polyelectrolyte mixture solution obtained by optimization and a conventional liquid lens made of a sodium chloride solution were compared and analyzed in terms of optical focal performance. The two liquid lenses only differed in the type of conductive liquid. Figure 7 This is a comparison chart of the optical power of these two liquid lenses. Simple electrolyte solutions such as sodium chloride solution are commonly used materials for conventional electrowetting liquid lenses. It can be seen that the liquid lens based on the polyelectrolyte mixture solution optimized by the present invention has greatly improved optical power and driving force performance compared to the liquid lens based on sodium chloride solution. The minimum driving voltage of the liquid lens based on sodium chloride solution is 20V, while the liquid lens based on the polyelectrolyte mixture solution can be driven at a low voltage of 10V. The light transmittance test results of the optimized optimal polyelectrolyte mixture solution show that the solution has a high transmittance (≥89%) in the visible light band (400~800nm), as shown in the following figure. Figure 8 As shown, it can be seen that the solution material can be well applied in the field of optical imaging. Fig. 9As shown in the figure, the transmittance spectrum in the 200~1400nm band proves that the material can also have specific applications in the near-infrared band.

[0047] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for optimizing the optical power of a liquid lens, characterized in that: The following steps are involved: (1) Screening the drugs required for the mixture with the help of a material property database, that is, polyelectrolyte and electrolyte mixed therewith, and preparing multiple groups of polyelectrolyte mixture solutions with different blending ratios by changing the relative proportions of the mixture at a fixed solute fraction; (2) extracting and analyzing the fluid viscosity data of the polyelectrolyte mixture solutions of all the above combinations at high shear rates through viscosity measurement experiments; (3) extracting and analyzing the spectral data of the liquids in the characteristic ratio groups in all combinations through laser Raman spectroscopy experiments; (4) Using the electrowetting contact angle measurement method, the electrowetting effect of all liquid combinations is measured, and the viscosity and spectrum data are combined for comprehensive analysis to select the optimal liquid combination and measure its optical properties; (5) Using the optimal liquid combination selected, an electrowetting liquid lens is produced and its optical power data is measured.

2. The optimization method for improving the optical power of a liquid lens according to claim 1, characterized in that: In the step (1), the polyelectrolyte mixture solution needs to contain at least one polyelectrolyte and one to five electrolytes mixed therewith.

3. The optimization method for improving the optical power of a liquid lens according to claim 1, characterized in that: In step (2), the fluid viscosity data is the viscosity of all combined liquids at 10-100s -1 The average viscosity in the high shear rate range.

4. The optimization method for improving the optical power of a liquid lens according to claim 1, characterized in that: In the step (3), the polyelectrolyte content difference between the selected liquids in each characteristic ratio group must be no less than 5%.

5. The optimization method for improving the optical power of a liquid lens according to claim 1, characterized in that: In the step (4), the electrowetting effect, viscosity and spectral properties are used as comprehensive performance evaluation indicators to select the optimal polyelectrolyte mixture solution, and ammonium polyphosphate and potassium chloride are selected as blended chemicals. The mass fraction of ammonium polyphosphate in the optimal polyelectrolyte mixture solution is not less than 10%, and the total mass fraction of ammonium polyphosphate and potassium chloride is 20%.

6. The optimization method for improving the optical power of a liquid lens according to claim 4, characterized in that: The spectral data of the characteristic ratio group liquid was obtained by measuring with a laser Raman spectrometer in the excitation band of 488~633nm.

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