Large-aperture cascaded mode-controlled variable-focus liquid crystal lens system and method

Abstract

The application discloses a large-aperture cascade mode control variable-focus liquid crystal lens system and a preparation method. Through the correlation technology between the piezoelectric film control technology and the flexible lens forming technology, a piezoelectric film composite liquid crystal molecule orientation conversion film capable of realizing the flexible lens is prepared, a cascade liquid crystal lens system based on the voltage control structure of the piezoelectric film composite liquid crystal molecule orientation conversion film, the center electrode and the circular hole electrode stack is invented, high-resolution imaging of a large range zoom can be realized, and the cascade mode control variable-focus liquid crystal lens system from visible light to near-infrared waveband with a large aperture is invented by cooperating with the use of an infrared waveband low-absorption high-refractive anisotropy (Delta n) fast-response liquid crystal.

Description

Technical Field

[0001] This invention belongs to the field of electronically controlled variable focus lenses, and particularly relates to a large-aperture cascaded mode-controlled variable focus liquid crystal lens system. Background Technology

[0002] Zoom glasses allow for adjustment of the lens focal length as needed, enabling wearers to obtain images at different focal lengths without changing their glasses. There are several ways to achieve zoom glasses, among which liquid crystal lenses (LCDs) utilize an applied voltage to create a gradient refractive index distribution in the liquid crystal layer, thereby modulating the phase of incident light. Compared to traditional optical lenses, LCDs offer advantages such as electrically adjustable focal length, no need for mechanical moving parts, small size, low cost, and ease of integration, leading to their widespread use.

[0003] For high-resolution imaging systems in both military and civilian applications, liquid crystal lens systems still require breakthroughs in several key technologies to achieve large lens apertures, polarization independence, continuous electronically controlled focusing over a wide range from concave to convex lenses, and a wide operating wavelength covering the visible to near-infrared spectrum. To address these needs, an electronically controlled liquid crystal lens with a polarization-independent large zoom range has been invented. Summary of the Invention

[0004] This invention discloses a large-aperture cascaded mode-controlled zoom liquid crystal lens system and its fabrication method. By employing piezoelectric thin film control technology and the correlation technology between forming a flexible lens, this invention fabricates a piezoelectric thin film composite liquid crystal molecule orientation conversion film capable of realizing a flexible lens. It also invents a cascaded liquid crystal lens system based on a voltage-controlled structure of a piezoelectric thin film composite liquid crystal molecule orientation conversion film, a central electrode, and a circular aperture electrode stack. This system enables high-resolution imaging with a wide zoom range. Furthermore, by utilizing a fast-response liquid crystal with low absorption and high refractive index anisotropy (Δn) in the infrared band, a large-aperture cascaded mode-controlled zoom liquid crystal lens system covering the visible to near-infrared bands is invented.

[0005] The specific technical solution of the present invention is as follows:

[0006] A liquid crystal lens with mode control forms a gradient refractive index distribution, thereby realizing the function of a large-aperture lens;

[0007] A double-layer liquid crystal lens structure is adopted, with a flexible composite liquid crystal molecule orientation conversion film in the middle, to achieve polarization independence of the liquid crystal lens system;

[0008] By employing a stacked structure of a central electrode and a circular hole electrode, and by switching the electrodes under appropriate driving conditions, the conversion of liquid crystal lenses with the same parallel orientation from concave lenses to convex lenses is realized.

[0009] By using fast-response liquid crystal materials with low infrared absorption and high refractive index difference, the working band covers the visible to near-infrared band, broadening the working band of the liquid crystal lens, increasing the range of focal length adjustment, and improving the response speed of the liquid crystal lens.

[0010] The large-aperture cascaded mode-controlled variable-focus liquid crystal lens system and method of the present invention have the following advantages:

[0011] The large-aperture cascaded mode-controlled variable-focus liquid crystal lens system proposed in this invention can meet the requirements of electronically controlled zoom, can operate in a wide spectral band from visible light to near infrared, can achieve large-aperture high-resolution focusing imaging, and can realize a polarization-independent flexible liquid crystal lens system that can achieve continuous large-range focusing from convex lens to concave lens. Attached Figure Description

[0012] Figure 1 Initial state diagram of a large-aperture cascaded mode-controlled variable-focus liquid crystal lens system.

[0013] Figure 2 A diagram showing the convex lens status of a large-aperture cascaded mode-controlled variable-focus liquid crystal lens system.

[0014] Figure 3 Diagram of the concave lens state in a large-aperture cascaded mode-controlled variable-focus liquid crystal lens system.

[0015] Figure 4 Schematic diagram of the working principle of a stacked electrode structure liquid crystal lens.

[0016] Figure 5 A liquid crystal lens with mode control.

[0017] The markings in the diagram are as follows: 100, Large-aperture cascaded mode-controlled variable-focus liquid crystal lens system; 200, Mode-controlled liquid crystal lens; 201, Equivalent convex lens system; 202, Equivalent concave lens system; 1, Substrate glass; 2, Ring electrode; 3, Center electrode; 4, Common electrode; 5, Liquid crystal alignment layer; 6, Fast-response liquid crystal with low absorption and high refractive index anisotropy (Δn) in the infrared band; 7, Flexible piezoelectric film; 8, Liquid crystal molecular alignment conversion film; 9, ZnO high-resistivity layer; 10, Cured mixed liquid crystal polymer; 11, Flexible piezoelectric film negative electrode; 12, Flexible piezoelectric film positive electrode; 13, Driving signal source; 14, Piezoelectric film composite liquid crystal molecular alignment conversion film; 15, Upper liquid crystal layer; 16, Lower liquid crystal layer; 17, Liquid crystal molecular alignment conversion film. Detailed Implementation

[0018] To better understand the purpose, structure, and function of this invention, the following detailed description of a large-aperture cascaded mode-controlled variable-focus liquid crystal lens system and method is provided in conjunction with the accompanying drawings.

[0019] A large-aperture cascaded mode-controlled variable-focus liquid crystal lens system 100 mainly includes:

[0020] A flexible lens is achieved by combining a piezoelectric thin film with a liquid crystal molecule orientation conversion film 14.

[0021] The mode-controlled liquid crystal lens 200 enables high-resolution imaging and wide-range zoom technology;

[0022] A voltage control structure for the stacked central electrode 3 and circular hole electrode 2;

[0023] Fast-response liquid crystal with low absorption and high refractive index anisotropy (Δn) in the infrared band;

[0024] The preparation of the piezoelectric thin film composite liquid crystal molecule orientation conversion film 14 mainly includes the preparation of flexible piezoelectric thin film 7, the preparation of liquid crystal molecule orientation conversion film 8, and the combination of flexible piezoelectric thin film 7 and liquid crystal molecule orientation conversion film 8.

[0025] The preparation method and steps for the flexible piezoelectric thin film 7 are as follows:

[0026] PMN-PT piezoelectric single crystal particles were mixed with a 5 mol / L AgNO3 solution in a dark environment and stirred for 40 to 60 minutes to ensure homogeneity. The mixture was then irradiated with ultraviolet light for 30 to 50 minutes while maintaining continuous stirring. The prepared Ag@PMN-PT heterojunction was then separated from the solution using a centrifuge, washed several times with deionized water, and dried in a nitrogen atmosphere to obtain Ag@PMN-PT heterojunction particle powder. An appropriate amount of PVDF-TrFE was then weighed and dispersed in DMF organic solvent, stirred and shaken to ensure homogeneity, yielding a PVDF-TrFE solution. The Ag@PMN-PT heterojunction was then dispersed in... In a PVDF-TrFE solution, the phases are stirred and oscillated to ensure uniform dispersion, thus preparing an Ag@PMN-PT / PVDF-TrFE composite solution. Then, an appropriate amount of copper nanorods are doped as a conductive phase, and the solution is stirred and oscillated to ensure uniform dispersion, thus preparing a copper nanorod / Ag@PMN-PT / PVDF-TrFE flexible composite piezoelectric film precursor solution. The precursor solution is then coated onto a casting plate, hot-pressed, and dried under a nitrogen atmosphere to prepare a flexible composite piezoelectric film. ITO is then sputtered onto both sides of the flexible composite piezoelectric film surface as transparent electrodes to prepare a film with electrodes on both sides. An alternating electric field is then applied to the film after electrode sputtering to polarize it, and finally, the film is removed and cooled.

[0027] The liquid crystal molecule orientation conversion film 8 is prepared as follows:

[0028] The E7 / RM257 mixture was poured into an empty cell with vertically aligned upper and lower substrates, a thickness of 20μm to 100μm, and removable upper and lower substrates. The liquid crystal cell was then subjected to a square wave voltage with an intensity of 5mW / cm². 2 Up to 15mW / cm 2 The liquid crystal cell was exposed to ultraviolet light for 40 to 80 minutes. Finally, the upper and lower substrates of the liquid crystal cell were removed to obtain a liquid crystal molecular alignment conversion film with a thickness of 20 μm to 50 μm.

[0029] The flexible piezoelectric film 7 and the liquid crystal molecule alignment conversion film 8 are bonded together by using epoxy adhesive to adhere the flexible piezoelectric film 7 to the upper surface of the liquid crystal molecule alignment conversion film 8, and then spin-coating the liquid crystal molecule alignment layer onto the upper surface of the flexible piezoelectric film 7.

[0030] The packaging process of the mode-controlled liquid crystal lens 200 includes:

[0031] The piezoelectric thin film composite liquid crystal molecule orientation conversion film 14 is tightly attached to a rigid substrate and encapsulated with an upper substrate having a central electrode 3 and a ring electrode 2. After the sealant is completely cured, the rigid substrate is gently peeled off to obtain an upper liquid crystal layer 15 empty cell. The upper liquid crystal layer 15 empty cell is then encapsulated with a lower substrate having a common electrode 4 to obtain a liquid crystal lens empty cell 200 with mode control embedded in the piezoelectric thin film composite liquid crystal molecule orientation conversion film 14. During this process, the surface orientation of the upper and lower substrates needs to be aligned with the surface orientation of the piezoelectric thin film composite liquid crystal molecule orientation conversion film 14, while the orientation direction of the upper liquid crystal layer 15 empty cell is orthogonal to the orientation direction of the lower liquid crystal layer 16 empty cell. Finally, a fast-response liquid crystal 6 with low absorption and high refractive index anisotropy (Δn) in the infrared band is injected.

[0032] The fabrication process of the voltage-controlled structure of the stacked central electrode 3 and circular hole electrode 2 is as follows:

[0033] A ZnO thin film is sputtered on the substrate with the ring electrode 2 by radio frequency magnetron sputtering as a high-resistivity layer 9, and then a central electrode 3 is prepared in the center of the ring electrode 2 by photolithography and led out.

[0034] The working principle of the voltage-controlled liquid crystal lens with the stacked center electrode 3 and circular hole electrode 2 is as follows:

[0035] By adjusting the applied electric field, the alignment of liquid crystal molecules is altered, and the wavefront is modulated according to the resulting potential distribution, thus forming convex and concave lenses. When no voltage is applied, the liquid crystal lens is in an unfocused state. When the common electrode 4 and the annular electrode 2 are grounded, and the central electrode 3 is connected to a signal source, the electric field at the center of the circular aperture is higher than that at the edge, inducing the liquid crystal molecules to be perpendicular to the substrate in the center and maintain their original parallel orientation on both sides, forming a convex lens. When the common electrode 4 and the central electrode 3 are grounded, and the annular electrode 2 is connected to a signal source, the electric field at the center of the circular aperture is lower than that at the edge, inducing the liquid crystal molecules to maintain their original parallel orientation in the center and be perpendicular to the substrate on both sides, forming a concave lens.

[0036] The fabrication process of the infrared band low-absorption, high-refractive-index anisotropic (Δn) fast-response liquid crystal 6 is as follows:

[0037] Based on the selected biphenyl, NCS, and diphenylacetylene-based liquid crystal molecular structures, a coupling reaction was first carried out, followed by the preparation of a group sensitive to Pd(PPh3)4, and the amino group was deprotected to prepare the NCS structure product.

[0038] A first embodiment of a method for fabricating a large-aperture cascaded mode-controlled variable-focus liquid crystal lens system 100:

[0039] 1. The flexible piezoelectric film 7 is prepared using AgNO3 as the solute and ethanol as the solvent to prepare an AgNO3 solution with a concentration of 3 mol / L to 6 mol / L;

[0040] 2. In the dark, mix PMN-PT piezoelectric single crystal particles with AgNO3 solution and stir for 40 to 60 minutes to ensure uniform mixing;

[0041] 3. Irradiate the mixed solution with ultraviolet light for 30 to 50 minutes, while continuously stirring.

[0042] 4. Then, the prepared Ag@PMN-PT heterojunction was separated using a centrifuge, washed several times with deionized water, and dried in a nitrogen atmosphere to finally prepare Ag@PMN-PT heterojunction particle powder.

[0043] 5. Weigh an appropriate amount of PVDF-TrFE, disperse it in DMF organic solvent, stir and shake to make the dispersion uniform, and obtain PVDF-TrFE solution;

[0044] 6. Disperse the Ag@PMN-PT heterojunction in the PVDF-TrFE solution, stir and vibrate to make the phases uniformly dispersed, and prepare the Ag@PMN-PT / PVDF-TrFE composite solution;

[0045] 7. In the Ag@PMN-PT / PVDF-TrFE composite solution, an appropriate amount of copper nanorods were doped as a conductive phase. The solution was stirred and oscillated to ensure uniform dispersion, thus preparing a copper nanorod / Ag@PMN-PT / PVDF-TrFE flexible composite piezoelectric film precursor solution.

[0046] 8. The precursor solution is coated onto a casting plate, and dried under hot pressing and nitrogen atmosphere to prepare an unpolarized flexible piezoelectric film.

[0047] 9. ITO was sputtered on both sides of the surface of the unpolarized flexible piezoelectric thin film as transparent electrodes to prepare a thin film with electrodes on both sides.

[0048] 10. Apply an alternating electric field to the film with electrodes on both sides to polarize it. Adjust the polarization temperature to 75℃ to 95℃. The frequency of the applied alternating voltage is 3Hz to 7Hz, the amplitude is 15kV / cm to 15kV / cm, and the number of cycles is 12. Remove the film and cool it to finally prepare a transparent flexible piezoelectric film 7.

[0049] 11. Preparation of the liquid crystal molecular orientation conversion film 8: RM257 (2-methyl-1,4-phenyl 4-(3-acryloyloxypropoxy)benzoic acid), liquid crystal E7, and photoinitiator 184 (1-hydroxycyclohexylphenyl ketone) are mixed in a suitable ratio to prepare an E7 / RM257 mixture.

[0050] 12. Pour the E7 / RM257 mixture into an empty box with vertically aligned upper and lower substrates, a thickness of 20μm to 100μm, and removable upper and lower substrates.

[0051] 13. The liquid crystal cell is subjected to a square wave voltage with a frequency of 800Hz to 1.5kHz and an amplitude of 18Vrms to 30Vrms, with an intensity of 5mW / cm. 2 Up to 15mW / cm 2 Expose the liquid crystal cell to ultraviolet light for 40 to 80 minutes, and finally peel off the upper and lower substrates of the liquid crystal cell to obtain the liquid crystal molecular alignment conversion film 8.

[0052] 14. The voltage control structure of the stacked center electrode 3 and the circular hole electrode 2 is a high-resistivity layer 9 with a thickness of 50 nm to 300 nm, formed by radio frequency magnetron sputtering of a ZnO thin film on a substrate with an annular electrode 2.

[0053] 15. A central electrode 3 is fabricated at the center of the ring electrode 2 using photolithography and led out to obtain a voltage-controlled structure of the stacked central electrode 3 and the circular hole electrode 2.

[0054] 16. The upper substrate with the voltage control structure having the stacked center electrode 3 and the circular hole electrode 2 and the lower substrate with the common electrode 4 are ultrasonically cleaned for 15 minutes in sequence with detergent, deionized water, acetone and anhydrous ethanol, and then dried.

[0055] 17. On the lower surface of the upper substrate with a voltage control structure having a stacked central electrode 3 and a circular hole electrode 2, and on the upper surface of the lower substrate with a common electrode 4, a polyimide (PI) liquid crystal alignment agent layer with a thickness of 50 nm to 150 nm is spin-coated using a spin coating process.

[0056] 18. The liquid crystal alignment agent layer is subjected to mechanical friction treatment to obtain liquid crystal alignment layer 5;

[0057] 19. The piezoelectric thin film composite liquid crystal molecule alignment conversion film 14 is tightly attached to the rigid substrate and sealed with the upper substrate with the central electrode 3 and the annular electrode 2. After the frame adhesive is completely cured, the rigid substrate is gently peeled off to obtain the empty cell of the upper liquid crystal layer 15. During this process, the surface orientation of the upper substrate needs to be aligned with the surface orientation of the piezoelectric thin film composite liquid crystal molecule alignment conversion film 14.

[0058] 20. Then, the upper liquid crystal layer 15 empty cell and the lower substrate with the common electrode 4 are sealed together to obtain a large aperture cascaded mode control variable focus liquid crystal lens system 100 empty cell with embedded piezoelectric thin film composite liquid crystal molecule orientation conversion film 14. In this process, the surface orientation of the lower substrate needs to be aligned with the lower surface orientation of the piezoelectric thin film composite liquid crystal molecule orientation conversion film 14.

[0059] 22. A fast-response liquid crystal 6 with low absorption and high refractive index anisotropy (Δn) in the infrared band was injected using a capillary tube and then sealed to finally obtain a large-aperture cascaded mode-controlled variable-focus liquid crystal lens system.

Claims

1. A large-aperture cascaded mode-control variable-focus liquid crystal lens system, characterized in that, It comprises: piezoelectric film composite liquid crystal molecule orientation conversion film (14) to realize flexible lens; and mode control liquid crystal lens (200) to realize high-resolution imaging and large range zoom; The piezoelectric film composite liquid crystal molecule orientation conversion film (14) is formed by combining flexible piezoelectric film (7) and liquid crystal molecule orientation conversion film (8), which is used to separate the upper liquid crystal layer (15) and the lower liquid crystal layer (16), so that the liquid crystal molecules of the upper liquid crystal layer (15) and the lower liquid crystal layer (16) are vertically oriented to each other, thereby realizing polarization independence of incident light; the surface of the flexible piezoelectric film (7) is provided with a flexible piezoelectric film positive electrode (12) and a flexible piezoelectric film negative electrode (11) on both sides respectively; The piezoelectric film composite liquid crystal molecule orientation conversion film (14) is stretched or shrunk by adjusting the voltage polarity and size loaded on the flexible piezoelectric film positive electrode (12) and the flexible piezoelectric film negative electrode (11), so that the shape of the piezoelectric film composite liquid crystal molecule orientation conversion film (14) is changed, thereby changing the focal length of the flexible lens formed by the piezoelectric film composite liquid crystal molecule orientation conversion film (14) and the liquid crystal molecules; when the piezoelectric film composite liquid crystal molecule orientation conversion film (14) is controlled to be in a stretched state, a flexible concave lens is formed, while maintaining the orientation conversion of the liquid crystal molecules, realizing large-aperture cascade mode control variable focus liquid crystal lens system polarization independence; when the piezoelectric film composite liquid crystal molecule orientation conversion film (14) is controlled to be in a shrunk state, a flexible convex lens is formed, while maintaining the orientation conversion of the liquid crystal molecules, realizing large-aperture cascade mode control variable focus liquid crystal lens system polarization independence.

2. The large-aperture cascaded mode-control variable-focus liquid crystal lens system according to claim 1, wherein, It also comprises a voltage control structure of a center electrode (3) and a circular hole electrode (2) stack; an infrared waveband low absorption high refractive anisotropy (Dn) fast response liquid crystal (6) to realize a wide working waveband of 380nm to 1300nm visible light to near infrared.

3. The method of claim 1 or 2, wherein the preparation method of the large-aperture cascaded mode-control variable-focus liquid crystal lens system is characterized in that, It comprises the preparation of the piezoelectric film composite liquid crystal molecule orientation conversion film (14), specifically comprising the following steps: A flexible piezoelectric film is prepared by coating a flexible composite piezoelectric film precursor solution on a casting plate, drying under hot pressing and nitrogen atmosphere, and sputtering electrodes on both sides; The flexible piezoelectric film is polarized by applying an alternating electric field, and finally a transparent flexible piezoelectric film (7) is prepared; A mixture of liquid crystal material E7 and polymer RM257 is filled into an empty box with vertically oriented upper and lower substrates and can be disassembled, and is exposed to ultraviolet light to obtain a liquid crystal molecule orientation conversion film; The flexible piezoelectric film (7) is adhered to the upper surface of the liquid crystal molecule orientation conversion film (8), and a liquid crystal molecule orientation layer (5) is spin-coated on the upper surface of the flexible piezoelectric film to obtain a piezoelectric film composite liquid crystal molecule orientation conversion film (14).

4. The method of claim 3, wherein, It also comprises the following steps: A glass substrate with a center electrode (3) and a circular hole electrode (2) stack structure is used as an upper substrate, and a general ITO glass substrate is used as a lower substrate, and a high resistance thin film is prepared on the lower surface of the upper substrate by a method of radio frequency magnetron sputtering zinc oxide film; The flexible piezoelectric film composite liquid crystal molecule orientation conversion film (14) is closely attached to the hard substrate, the hard substrate is aligned and attached to the upper substrate, and the upper liquid crystal layer empty box is formed; The upper liquid crystal layer empty box is aligned and attached to the lower substrate, and a cascade liquid crystal lens empty box embedded with the piezoelectric film composite liquid crystal molecule orientation conversion film (14) is obtained; The fast-response liquid crystal (6) with low absorption and high refractive anisotropy (Dn) in the infrared wave band is filled, and a large-aperture cascade mode control variable-focus liquid crystal lens system is obtained.

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