Blue phase liquid crystal lens

Abstract

The invention relates to the technical field of liquid crystal display, in particular to a blue-phase liquid crystal lens which comprises a blue-phase liquid crystal layer, plane electrodes arranged on the two sides of the blue-phase liquid crystal layer respectively and a round hole electrode provided with a through hole. The semiconductor device further comprises a high-resistance layer, and the outer edge of the high-resistance layer is connected with the inner wall of the through hole. The defect that in the prior art, the imaging quality is reduced due to uneven electric field distribution is overcome, the high-resistance layer is arranged in the round hole structure of a common round hole electrode, the high-resistance layer can be regarded as a plurality of small resistors connected between the electrode and the blue phase liquid crystal layer in series, and applied voltage is divided. The voltage dividing effect of the high-resistance layer enables the electric field to be in smooth transition from the edge of the through hole to the center, the problem that the central electric field is weak is solved, a phase delay distribution curve is closer to an ideal parabola, aberration (such as spherical aberration and coma aberration) is reduced, and finally the imaging quality is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid crystal display, more particularly, to a blue phase liquid crystal lens. BACKGROUND

[0002] The blue phase liquid crystal lens is a frontier research direction in the field of optoelectronics in recent years. The blue phase liquid crystal is a metastable liquid crystal phase between isotropic phase and cholesteric phase. The three-dimensional cubic structure of the self-assembly of the blue phase liquid crystal is periodically arranged on the nanometer scale, and exhibits unique birefringence effect and fast response characteristics (microsecond level). Compared with the traditional nematic liquid crystal, the blue phase liquid crystal can realize optical isotropy without an alignment layer, and has wider viewing angle and higher transmittance. Moreover, it does not need to stack two liquid crystal layers to realize polarization independence. Based on the Kerr effect, the blue phase liquid crystal can produce dynamic refractive index modulation under an applied electric field, and continuous focusing of the lens can be realized by design. This characteristic makes it have the potential to replace the mechanical zoom system in the fields of AR / VR near-eye display, autostereoscopic display system, adaptive optics, etc., and has a very great research value compared with the traditional non-variable-focus lens. For example, the prior art discloses a blue phase liquid crystal lens, which comprises an upper substrate, a double dielectric layer, a liquid crystal layer and a lower substrate. The liquid crystal layer adopts blue phase liquid crystal, and the thickness of the liquid crystal layer is uniform. The inner sides of the upper substrate and the lower substrate are respectively formed with a planar first transparent electrode and a second transparent electrode. The double dielectric layer is composed of a first dielectric layer and a second dielectric layer. The refractive index n1 of the first dielectric layer and the refractive index n2 of the second dielectric layer are the same. The dielectric constant ε1 of the first dielectric layer and the dielectric constant ε2 of the second dielectric layer are different. The second dielectric layer is in a convex structure or a concave structure, and is filled flat by the first dielectric layer. By controlling the shape of the second dielectric layer, a desired gradient electric field distribution is formed in the liquid crystal layer, so that a parabolic phase distribution is obtained. The focal length of the blue phase liquid crystal lens is controlled by the voltage applied by the first transparent electrode and the second transparent electrode.

[0003] However, the dielectric constant of the blue phase liquid crystal is usually low, resulting in a high driving voltage required for the reorientation of the molecules under the action of the electric field. High driving voltage leads to a significant increase in device power consumption and may cause local heating, affecting the stability of the blue phase liquid crystal. In addition, the existing circular hole electrode has a weak electric field strength near the center and a concentrated electric field at the edge, which is difficult to form a uniform electric field distribution in the lens area, resulting in a deviation of the phase delay distribution from the ideal parabolic distribution, and finally leading to the deformation of the focusing spot of the lens (such as coma, spherical aberration) and the decline of the imaging quality, which seriously limits its application in precision optical systems. SUMMARY

[0004] In view of the problem of reducing the imaging quality due to uneven electric field distribution in the prior art, the present application provides a blue phase liquid crystal lens, which can make the electric field distribution of the lens more uniform and improve the imaging quality.

[0005] To solve the above technical problems, the technical scheme provided by the present application is: A blue phase liquid lens comprises a blue phase liquid crystal layer, a planar electrode and a circular hole electrode with a through hole arranged on both sides of the blue phase liquid crystal layer; further comprising a high resistance layer, the outer edge of the high resistance layer is connected with the inner wall of the through hole.

[0006] It can be understood that the planar electrode is grounded and the circular hole electrode is connected to a driving power supply. When the planar electrode and the circular hole electrode are applied with a voltage, a gradient refractive index is formed in the blue phase liquid crystal layer to achieve lens focusing. In the above technical scheme, the high resistance layer can be regarded as a plurality of small resistances connected in series between the electrode and the blue phase liquid crystal layer, which divides the applied voltage. The voltage dividing effect of the high resistance layer makes the electric field smoothly transition from the edge of the through hole to the center, solves the problem of weak electric field in the center, makes the electric field distribution of the lens more uniform, makes the phase delay distribution curve closer to the ideal parabola, thereby reducing aberrations (such as spherical aberration and coma), and ultimately improving the imaging quality.

[0007] Preferably, a high dielectric layer with a dielectric constant higher than that of the blue phase liquid crystal layer is further included, and the high dielectric layer is located between and connected with the blue phase liquid crystal layer and the circular hole electrode. The dielectric constant of the high dielectric layer is much higher than that of the blue phase liquid crystal layer, and the electric field lines will concentrate towards the low dielectric constant, that is, towards the blue phase liquid crystal layer, thereby enhancing the effective electric field strength in the blue phase liquid crystal layer. This is conducive to reducing the driving voltage. The high dielectric layer can globally enhance the electric field and reduce the voltage requirement; the high resistance layer can locally fine-tune the electric field gradient through voltage division, which can further homogenize the refractive index distribution; the combination of the two can make the phase delay distribution almost fit the ideal curve, greatly improving the imaging quality.

[0008] Preferably, the high dielectric layer adopts barium titanate material. Barium titanate material has a relatively high relative dielectric constant, which is 100-1000 times that of the blue phase liquid crystal layer, and can greatly reduce the driving voltage. Moreover, it has a high dielectric strength and is not easy to be punctured under high voltage.

[0009] Preferably, the high resistance layer adopts aluminum-doped zinc oxide material. Aluminum-doped zinc oxide material has a relatively high resistance, which can ensure effective voltage division, and has moderate conductivity, which can avoid completely blocking the electric field. The resistivity of aluminum-doped zinc oxide can be controlled by different aluminum doping concentrations to meet the voltage division requirement. In addition, aluminum-doped zinc oxide material has a relatively high light transmittance, which can avoid additional light scattering.

[0010] Preferably, the thickness of the high-resistance layer and the circular hole electrode is between 1.5 μm and 2.5 μm. The thickness of the high-resistance layer is equal to that of the circular hole electrode, which can ensure smooth transition of the electric field from the circular hole electrode to the high-resistance layer and reduce the interface electric field distortion. Controlling the thickness of the two layers between 1.5 μm and 2.5 μm can ensure that the high-resistance layer has sufficient resistance volume to achieve effective voltage division and avoid insufficient resistance value caused by excessive thinness. Moreover, the high-resistance layer has certain mechanical strength under the premise of ensuring sufficient light transmittance.

[0011] Preferably, the thickness of the high-resistance layer and the circular hole electrode is between 1.5 μm and 2.5 μm. The thickness of the high-resistance layer is equal to that of the circular hole electrode, which can ensure smooth transition of the electric field from the circular hole electrode to the high-resistance layer and reduce the interface electric field distortion. Controlling the thickness of the two layers between 1.5 μm and 2.5 μm can ensure that the high-resistance layer has sufficient resistance volume to achieve effective voltage division and avoid insufficient resistance value caused by excessive thinness. Moreover, the high-resistance layer has certain mechanical strength under the premise of ensuring sufficient light transmittance.

[0012] Preferably, the first substrate and the second substrate are further included, the planar electrode is connected between the first substrate and the blue phase liquid crystal layer, and the circular hole electrode is connected between the second substrate and the blue phase liquid crystal layer. The first substrate and the second substrate can provide rigid support for the electrodes and the liquid crystal layer to prevent electrode fracture or liquid crystal layer leakage caused by bending or pressure. Moreover, the first substrate and the second substrate can block the invasion of water and oxygen to avoid oxidation of the blue phase liquid crystal material or degradation of the polymer network, thereby prolonging the service life of the device.

[0013] Preferably, the thickness of the first substrate and the second substrate is between 90 μm and 110 μm, which can avoid the problem of easy breakage caused by excessive thinness and avoid the adverse effects on overall light transmittance and weight.

[0014] Preferably, the first substrate and the second substrate are both quartz glass structures. Quartz glass is wear-resistant, has a transmittance of more than 99.5% under natural light, and has good thermal stability, corrosion resistance and ion blocking ability, which can improve the service life and reliability of the device.

[0015] Preferably, the planar electrode and the circular hole electrode are both ITO electrodes, i.e., the planar electrode and the circular hole electrode are both made of ITO (indium tin oxide) material. Compared with other transparent electrodes, the ITO electrode has higher light transmittance and smaller dielectric loss, without signal delay. The refractive index of the ITO electrode is between the glass substrate and the blue phase liquid crystal layer, which can reduce the interface Fresnel reflection and improve the overall optical efficiency.

[0016] The beneficial effects of the present application are as follows: 1. A high resistance layer is arranged in the structure of the common round hole electrode, which can be regarded as a plurality of small resistances connected in series between the electrode and the blue phase liquid crystal layer, and divides the applied voltage. The voltage dividing effect of the high resistance layer makes the electric field transition smoothly from the edge to the center of the hole, compensates for the weak central electric field, makes the phase delay distribution curve closer to the ideal parabola, thereby reducing aberrations (such as spherical aberration and coma), and ultimately improving the imaging quality.

[0017] 2. The high resistance layer in combination with the high dielectric layer can further optimize the electric field distribution of the blue phase liquid crystal lens, making the actual phase delay distribution almost close to the ideal curve, and greatly improving the imaging quality of the lens. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a phase delay distribution diagram of a blue phase liquid crystal lens of a common round hole electrode; Figure 2 is a potential distribution diagram of a first embodiment of a blue phase liquid crystal lens; Figure 3 is a structural schematic diagram of a blue phase liquid crystal lens of the present application; Figure 4 is a phase delay distribution diagram of a second embodiment of a blue phase liquid crystal lens.

[0019] In the drawings: 1-blue phase liquid crystal layer; 2-plane electrode; 3-round hole electrode; 4-high resistance layer; 5-high dielectric layer; 6-first substrate; 7-second substrate. DETAILED DESCRIPTION

[0020] The drawings are only used for illustrative description, and cannot be understood as a limitation of the present patent; in order to better illustrate the embodiments, some components in the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted. The positional relationship described in the drawings is only used for illustrative description, and cannot be understood as a limitation of the present patent.

[0021] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it should be understood that if the terms "upper", "lower", "left", "right", "long" and "short" indicate the orientation or positional relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the positional relationship in the drawings are only used for illustrative description, and cannot be understood as a limitation of the present patent, for those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0022] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings: Example 1 Phase delay distribution is the optical effect of refractive index distribution, which directly determines the focusing ability of the lens. The phase delay distribution of ordinary circular hole electrode type blue phase liquid crystal lens under electric field is simulated by finite element method. The simulation parameters are shown in Table 1: Table 1 Simulation parameters of ordinary circular hole electrode type blue phase liquid crystal lens

[0023] The phase delay distribution curve of the blue phase liquid crystal lens with ordinary circular hole electrode under 50V driving voltage is as follows: Figure 2 As shown in the figure, the steepest (sharpest) parabola is the ideal curve, while the less steep (flatter) parabola is the actual curve. Due to the uneven electric field distribution in circular-aperture electrode-type blue-phase liquid crystal lenses, the actual phase retardation distribution deviates significantly from the ideal curve. This problem prevents light from converging at the ideal focal point after passing through the lens, resulting in large wavefront aberrations, causing lens imaging distortion and reducing the imaging quality of the blue-phase liquid crystal lens.

[0024] This embodiment is the first embodiment of a blue phase liquid crystal lens, which aims to overcome the above problems, such as Figure 2 As shown, it includes a blue phase liquid crystal layer 1, planar electrodes 2 and circular hole electrodes 3 provided with through holes respectively arranged on both sides of the blue phase liquid crystal layer 1. Furthermore, the lens also includes a high resistance layer 4, the outer edge of which is connected to the inner wall of the through hole.

[0025] Furthermore, both the planar electrode 2 and the circular hole electrode 3 are ITO electrodes, i.e., both are made of ITO (indium tin oxide) material. Compared to other transparent electrodes, ITO electrodes have higher light transmittance, lower dielectric loss, and no signal delay. The refractive index of the ITO electrode is between that of the glass substrate and the blue phase liquid crystal layer 1, which reduces interfacial Fresnel reflections and improves overall optical efficiency.

[0026] Furthermore, the high resistance layer 4 is made of aluminum-doped zinc oxide material, and the square resistance value R sq = 0.6 MΩ , the width of the high resistance layer 4 is 400 um , with a height of 2 um The material of the high dielectric layer 5 is barium titanate BaTiO3, with a dielectric constant of 2000 and a frequency of 150 kHz.The aluminum-doped zinc oxide material has a high resistance, which can ensure an effective partial pressure, and has moderate conductivity, which can avoid complete blocking of the electric field. The resistivity of the aluminum-doped zinc oxide can be controlled by different aluminum doping concentrations to meet the partial pressure requirement. In addition, the aluminum-doped zinc oxide material has a high light transmittance, which can avoid additional light scattering.

[0027] Further, the thicknesses of the planar electrode 2, the high-resistance layer 4, and the circular hole electrode 3 are all 2 μm, and the wavelength of the light wave used is 550 nm nm. The thickness of the high-resistance layer 4 is equal to that of the circular hole electrode 3, which can ensure smooth transition of the electric field from the circular hole electrode 3 to the high-resistance layer 4 and reduce interface electric field distortion. The thicknesses of the two are set to 2 μm, which can ensure that the high-resistance layer 4 has sufficient resistance volume to achieve effective partial pressure and avoid insufficient resistance value due to being too thin. Moreover, the high-resistance layer 4 has certain mechanical strength under the premise of ensuring sufficient light transmittance.

[0028] Specifically, the related parameter values of the blue phase liquid crystal layer 1 used are as follows: n e = 1.7, n o = 1.5, E s = 5.6 V / um ), Δn s = 0.2, λ= 555 nm , the relative dielectric constant of the dielectric layer ε =2000, the relative dielectric constant of the blue phase liquid crystal in the voltage-off state ε LC =30.

[0029] The working principle or working process of the embodiment is as follows: when no voltage is applied to the lens, the blue phase liquid crystal is optically isotropic, and its refractive index is n iso , wherein n o is the ordinary light refractive index of the blue phase liquid crystal molecule, n e is the extraordinary light refractive index of the blue phase liquid crystal molecule. When a voltage is applied to the lens, a vertical electric field is generated in the blue phase liquid crystal layer 1, and according to the extended Kerr effect model, the electric field-induced birefringence of the blue phase liquid crystal can be obtained as Δn ind (E) , wherein Δn s is the saturation birefringence of the blue phase liquid crystal molecule,E s is the value of the saturated electric field. For normally incident light rays, o light and e The refractive index of light is the ordinary refractive index of the blue phase liquid crystal n o (E) , which can be expressed by the following formula: .

[0030] In the implementation of the present embodiment, the planar electrode 2 is grounded, the circular hole electrode 3 is applied with a driving voltage of 50V, and the wavelength of the light wave adopted is 550nm. When the voltage is applied to the planar electrode 2 and the circular hole electrode 3, a gradient refractive index distribution is formed in the blue phase liquid crystal layer 1 to achieve lens focusing. The high resistance layer 4 can be regarded as a plurality of small resistances connected in series between the electrode and the blue phase liquid crystal layer 1, which divides the applied voltage. The voltage dividing effect of the high resistance layer 4 makes the electric field transition smoothly from the edge to the center of the through hole, solves the problem of weak electric field in the center, and makes the electric field distribution of the lens more uniform. As shown in Figure 3 The potential distribution in the lens of the present embodiment is shown in the figure. As can be seen from the figure, the distribution of the electric field is smoother and more uniform. Therefore, the phase delay distribution curve can be closer to the ideal parabola, thereby reducing aberrations such as spherical aberration and coma, and ultimately improving the imaging quality.

[0031] Embodiment 2 The present embodiment is a second embodiment of a blue phase liquid crystal lens. The present embodiment is similar to embodiment 1, except that it further comprises a high dielectric layer 5 with a dielectric constant higher than that of the blue phase liquid crystal layer 1. The high dielectric layer 5 is located between and connected with the blue phase liquid crystal layer 1 and the circular hole electrode 3. The dielectric constant of the high dielectric layer 5 is much higher than that of the blue phase liquid crystal layer 1, and the electric field lines will concentrate towards the low dielectric constant, i.e. towards the blue phase liquid crystal layer 1, thereby enhancing the effective electric field strength in the blue phase liquid crystal layer 1. This is beneficial to reduce the driving voltage. The high dielectric layer 5 can globally enhance the electric field and reduce the voltage requirement; the high resistance layer 4 can locally fine-tune the electric field gradient by voltage division, which can further homogenize the refractive index distribution; the combination of the two can make the phase delay distribution curve almost fit the ideal curve, greatly improving the imaging quality. As shown in Figure 4 The phase delay distribution of the blue phase liquid crystal lens with the high resistance layer 4 is shown in the figure. As can be seen from the figure, after the combination of the high resistance layer 4 and the high dielectric layer 5, the actual phase delay distribution curve almost approaches the ideal curve. The root mean square value of the optical path difference error calculated is 0.007456 um , and the root mean square value of the optical path difference error of the ordinary circular hole electrode type blue phase liquid crystal lens is 0.036725 um , indicating that the wavefront error value is reduced by about 5 times, greatly reducing the wavefront error of the lens and improving its imaging quality.

[0032] Specifically, the high-dielectric layer 5 is made of barium titanate. Barium titanate has a high relative dielectric constant, 100 to 1000 times that of the blue-phase liquid crystal layer 1, significantly reducing the driving voltage. It also has high dielectric strength, making it capable of withstanding high voltages without breakdown.

[0033] Specifically, the high-dielectric layer has a thickness of 30μm. A high-dielectric layer that is too thin can easily lead to dielectric breakdown, while a high-dielectric layer that is too thick can cause a decrease in light transmittance and an increase in driving voltage. A high-dielectric layer with a thickness of 25μm to 35μm can optimize the electric field while maintaining high reliability.

[0034] Other features, working principles and beneficial effects of this embodiment are consistent with those of embodiment 1.

[0035] Example 3 This embodiment is the third embodiment, and this embodiment is similar to embodiment 2, except that: Figure 2 As shown, the thickness of the first substrate 6 and the second substrate 7 is 100 μm and the width is 600 μm. ， This can avoid the problem of easy breakage caused by too thin thickness, while avoiding adverse effects on overall light transmittance and weight.

[0036] Furthermore, the first substrate 6 and the second substrate 7 are both made of quartz glass. Quartz glass is relatively wear-resistant, with a transmittance greater than 99.5% under natural light, and has good thermal stability, corrosion resistance, and ion blocking capabilities, which can improve the service life and reliability of the device.

[0037] Other features, working principles and beneficial effects of this embodiment are consistent with those of Example 2.

[0038] In the specific contents of the above-mentioned specific implementation methods, the various technical features can be combined in any non-contradictory manner. In order to make the description concise, not all possible combinations of the above-mentioned technical features are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0039] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description, and it is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A blue phase liquid crystal lens, comprising a blue phase liquid crystal layer (1), planar electrodes (2) respectively arranged on both sides of the blue phase liquid crystal layer (1), and a circular hole electrode (3) provided with a through hole, characterized in that: It also includes a high-resistance layer (4), the outer edge of the high-resistance layer (4) being connected to the inner wall of the through hole.

2. The blue phase liquid crystal lens according to claim 1, characterized in that: It also includes a high dielectric layer (5) having a higher dielectric constant than the blue phase liquid crystal layer (1), and the high dielectric layer (5) is located between the blue phase liquid crystal layer (1) and the circular hole electrode (3) and is connected to both.

3. The blue phase liquid crystal lens according to claim 2, characterized in that: The high dielectric layer (5) is made of barium titanate material.

4. The blue phase liquid crystal lens according to claim 1, wherein: The high resistance layer (4) is made of aluminum-doped zinc oxide material.

5. The blue phase liquid crystal lens according to claim 2, characterized in that: The thickness of the high-resistance layer (4) and the circular hole electrode (3) are both between 1.5 μm and 2.5 μm.

6. The blue phase liquid crystal lens according to claim 5, characterized in that: The thickness of the high dielectric layer (5) is between 25 μm and 35 μm.

7. The blue phase liquid crystal lens according to claim 1, characterized in that: It also includes a first substrate (6) and a second substrate (7), the planar electrode (2) is connected between the first substrate (6) and the blue phase liquid crystal layer (1), and the circular hole electrode (3) is connected between the second substrate (7) and the blue phase liquid crystal layer (1).

8. The blue phase liquid crystal lens according to claim 7, characterized in that: The thickness of the first substrate (6) and the second substrate (7) is between 90 μm and 110 μm.

9. The blue phase liquid crystal lens according to claim 7, characterized in that: The first substrate (6) and the second substrate (7) are both quartz glass structures.

10. The blue phase liquid crystal lens according to any one of claims 1 to 9, characterized in that: The planar electrode (2) and the circular hole electrode (3) are both ITO electrodes.

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