Optical devices with electroactive lenses

Abstract

This disclosure relates to an electroactive unit for eyeglasses, the electroactive unit comprising an electroactive element, the electroactive element comprising: a first optically transparent substrate and a second optically transparent substrate, at least one liquid crystal layer between the first and second optically transparent substrates comprising nematic liquid crystal; and a Fresnel lens structure disposed thereon, wherein a first transparent electrode and a second transparent electrode are formed on the first and second substrates respectively, and wherein an alignment layer is present on the first substrate, the alignment layer being in contact with the liquid crystal layer and configured to align the nematic liquid crystal in a first direction; and a polarization element configured to adjust light having polarization along a second direction perpendicular to the first direction, wherein the liquid crystal of the liquid crystal layer is in a Mauguin state.

Description

Technical Field

[0001] This disclosure relates to an optical device for eyeglasses, the optical device including a first electroactive lens for tunable light transmission. This disclosure also relates to a lens unit including such an optical device, to eyeglasses comprising a frame in which the optical device is disposed, and to a method of operating the optical device. Background Technology

[0002] An optical device comprising a liquid crystal (LC) layer as part of an electroactive lens and a Fresnel lens structure can switch from a state where the refractive index of the LC matches the refractive index of the lens along the optical axis to a state where the refractive index of the LC does not match the refractive index of the lens in the direction perpendicular to the optical axis. In the latter state, the lens conducts polarized light whose polarization angle depends on the alignment of the LC. The liquid crystal lens can be a lens made entirely of liquid crystal or a lens made of an isotropic material filled with liquid crystal.

[0003] Several methods have been proposed to make such lenses suitable for unpolarized light, such as natural light:

[0004] 1. Two similar lenses are stacked on top of each other, wherein the liquid crystals in each lens are aligned perpendicularly to each other (US201715787082).

[0005] 2. Use the lens in combination with a linear polarizer with certain orientations (US4190330A).

[0006] Some patent documents concerning tunable liquid crystal lenses describe lens stacking, but tend to use planar alignment and do not consider how the Fresnel lens structures in the LC cavity are oriented relative to each other. Even when considered, Fresnel lens structures are typically stacked with their surfaces oriented in the same direction. See, for example, US20070216851A1, US9448456B2, US9690116B2, US10863949, US201715787082, or US4190330A.

[0007] This disclosure relates to electroactive lenses made of isotropic polymeric materials combined with vertically aligned liquid crystals. Such electroactive lenses are known, for example, from US 8,587,734. These known electroactive lenses have several drawbacks. For example, the orientation in the plane perpendicular to the optical axis is affected by the structure of the lens in the optical device. This orientation differs in different parts of the optical device. Therefore, in the methods mentioned above, the device will transmit not only a magnified image but also an unmagnified image in certain parts. This results in a dual image.

[0008] When the tilt angle of the vertically aligned liquid crystal is small and the tilt of the off-axis (relative to unidirectional tilting orientation) local lens surface is large, dual images appear when the electroactive cell is in the conducting state.

[0009] A switchable lens consisting of an isotropic polymer lens and a vertically aligned liquid crystal is known from US 8,587,734. The lens is fabricated by imprinting a polymer layer onto a substrate. During this process, spacers are also formed to maintain a distance between the second substrate and the lens. The cavity between the substrates covered with transparent electrodes is filled with liquid crystal. The orientation of the liquid crystal along the substrate is determined by several factors. The orientation in the off state is controlled by a polyimide layer serving as an alignment layer. Typically, this layer aligns the liquid crystal director (wherein the liquid crystal director is defined as the average direction of the long molecular axes of the liquid crystal molecules) uniformly perpendicular to the surface, also known as vertical alignment. If a voltage is then applied to the electrodes, the liquid crystal will randomly reorient along the surface in a plane. Rubbing the alignment layer on the substrate, for example, rubbing a polyimide-covered substrate, results in a small deviation of the director from the vertical orientation in the off state. Additional description of the concept of pre-tilting by rubbing (or similar techniques, such as photo-alignment) on an alignment layer in an electroactive lens is provided in WO 2019 / 038439 A1, the contents of which are incorporated herein by reference.

[0010] The deviation of the director vector is related to the friction direction and is referred to as pre-tilt. When a voltage is applied, the orientation on the substrate opposite the lens is determined solely by the friction direction. On substrates with lenses, the situation is more complex. The orientation of the liquid crystal director vector is affected by both the friction direction and the geometry of the lens surface. Since the orientation of the lens surface varies at different locations, the liquid crystal director vector is also non-uniform on the lens substrate. This is why, in some sections, the orientation of the director vector differs for the top and bottom substrates, resulting in director vector distortion. Note that a similar alignment can be achieved using photoalignment techniques (i.e., the application of appropriate pre-tilt). Summary of the Invention

[0011] The purpose of this disclosure is to provide an optical device including at least one tunable electroactive lens, which provides improved optical quality and / or reduced risk of double image occurrence.

[0012] Another objective is to improve optical quality and reduce the occurrence of optical artifacts such as double images when the light to be focused or dispersed by the electroactive lens is unpolarized.

[0013] According to a first aspect, an optical device for eyeglasses is provided, wherein the optical device includes a first electroactive lens for tunable light focusing or dispersion, the electroactive lens comprising:

[0014] - A first optically transparent substrate and a second optically transparent substrate, wherein the first optically transparent substrate and the second optically transparent substrate extend substantially parallel to each other and define an axial (z) direction and a transverse (x, y) direction;

[0015] - A diffractive lens structure, such as a Fresnel lens structure, is arranged between a first optically transparent substrate and a second optically transparent substrate on the side of the second optically transparent substrate.

[0016] - A first optically transparent electrode formed on a first optically transparent substrate and a second optically transparent electrode formed on a second optically transparent substrate or a diffractive lens structure;

[0017] -A sealed cavity (108) between the first optically transparent substrate and the second optically transparent substrate, wherein a diffractive lens structure and at least one LC layer of nematic liquid crystal (LC) material are arranged in the sealed cavity, and wherein the liquid crystal in the nematic liquid crystal (LC) material is substantially axially aligned in the off state.

[0018] The first optically transparent electrode includes an alignment layer having a contact surface that contacts the LC layer and is configured to linearly align the liquid crystal in the nematic liquid crystal material in a first horizontal direction in a conducting state by introducing pre-tilt in a turned-off state.

[0019] A polarizing element configured to adjust light having polarization along a second horizontal direction perpendicular to a first horizontal direction;

[0020] The LC layer of the nematic liquid crystal material has a thickness (D) measured between the portion of the diffractive lens structure closest to the first optically transparent electrode and the contact surface of the alignment layer on the first optically transparent electrode.

[0021] Among them, thickness (D) is chosen to satisfy the condition. n o n is the ordinary refractive index of the LC layer. e It is the unusual refractive index of the LC layer. λ is the twist angle of the liquid crystal director of the LC layer, and λ is the wavelength of light, with the wavelength λ ranging from 350nm to 750nm.

[0022] The range of the twist angle can be from 0 degrees to 180 degrees.

[0023] The pre-tilt caused by the alignment layer and other alignment layers (if present) discussed below provides a relatively small deviation from perfect axial alignment. In embodiments of this disclosure, the pre-tilt (defined as a small deviation from perfect axial (vertical) alignment) typically varies between 1 degree and 6 degrees relative to the axial (z) direction. Also refer to WO2019 / 038439 A1 filed by the same inventors, which also provides an explanation of how including a small pre-tilt can help the correct alignment of LC materials in both the off and on states.

[0024] When conditions are met, the liquid crystal in the liquid crystal layer is well in the Mauguin state, causing waveguides to form within the liquid crystal layer. This allows the linear polarization of light traveling through the optical device to be maintained. Furthermore, since a specific linear alignment direction can be applied to the first optically transparent electrode using an alignment layer of the first optically transparent electrode, a uniform and appropriate response of the optical device on its surface can be achieved. Additionally, by maintaining linear polarization, any unwanted artifacts such as double images can be filtered out. In some embodiments, filtering can be achieved by including a linear polarizer in the optical device, while in other embodiments, filtering is achieved by providing a second electroactive lens stacked on top of the first electroactive element, as will be described below. For example, in embodiments of this disclosure, the aforementioned polarizing element includes a polarizer (preferably a linear polarizer) configured to allow light with a first linear polarization to pass through and substantially block light with a second linear polarization perpendicular to the first linear polarization. Alternatively or additionally, in other embodiments of this disclosure, the aforementioned polarizing element includes a second electroactive lens stacked on top of the first electroactive lens, preferably similar to the first electroactive lens.

[0025] The optical device as defined herein may include a first substrate and a second substrate and / or a first alignment layer or a second alignment layer, the first substrate and the second substrate and / or the first alignment layer or the second alignment layer being substantially flat and arranged to extend generally parallel to each other. In these embodiments, when the flat substrate and / or the flat alignment layer are arranged to extend in a horizontal direction, the axial alignment corresponds to the vertical alignment. In other embodiments, the first substrate and the second substrate and / or the first alignment layer or the second alignment layer may be curved elements, wherein these curved elements are arranged to still extend generally parallel to each other. In these embodiments, the axial alignment of the nematic liquid crystal (LC) material is defined in an alignment in a direction locally perpendicular to the surface of the substrate / alignment layer facing the sealing cavity. In other words, an axial direction may be defined at each location on the surface, which is a direction perpendicular to the local orientation of the surface of the substrate / alignment layer. This direction is typically different for different locations on the surface. Therefore, in embodiments with curved substrates and alignment layers, it is preferable to refer to "axial alignment" rather than "vertical alignment".

[0026] While alignment layers are typically required in diffractive lens structures to axially (vertically) align the liquid crystal in the off state, introducing orientation pre-tilt is not strictly necessary. In the on state, a non-uniform director profile will exist at the diffractive lens structure, resulting in a varying twist angle that is highly dependent on the local diffractive lens structure. However, introducing pre-tilt in the same transverse (horizontal) direction as the linear alignment direction of the alignment layer on the first optically transparent electrode will generally reduce the twist angle value and thus increase the Mauguin condition value. This will lead to better optical performance.

[0027] Throughout this disclosure, when referring to liquid crystals in nematic liquid crystal (LC) materials that are typically axially aligned, it means that the main portion of the liquid crystal is aligned in a uniaxial direction.

[0028] According to an embodiment of the present disclosure, a diffraction lens structure disposed between a first optically transparent substrate and a second optically transparent substrate on the side of the second optically transparent substrate is disposed at the second optically transparent layer. A second optically transparent electrode may be formed on the diffraction lens structure. According to an embodiment of the present disclosure, the diffraction lens structure disposed between the first optically transparent substrate and the second optically transparent substrate on the side of the second optically transparent substrate is disposed at the second optically transparent electrode, wherein the second optically transparent electrode is disposed on the second optically transparent substrate.

[0029] According to embodiments of this disclosure, the polarization element includes a second electroactive lens stacked on a first electroactive lens. The first optically transparent layer of the first electroactive lens includes an alignment layer having a contact surface that contacts the LC layer and is configured to linearly align the liquid crystal in the nematic liquid crystal material in a first horizontal direction when in the on state. The first optically transparent layer of the second electroactive lens includes an alignment layer having a contact surface that contacts the LC layer and is configured to linearly align the liquid crystal in the nematic liquid crystal material in a second horizontal direction when in the on state, wherein the first direction is perpendicular to the second horizontal direction. In this manner, the optical device can transmit (i.e., disperse or focus) unpolarized light through the electroactive lens with improved accuracy, thereby avoiding or at least reducing the possibility of dual images.

[0030] Preferably, the optical power of the first electroactive lens corresponds to the optical power of the second electroactive lens, such that when the optical device is in the conducting state, the lensing effect provided by the optical device for the first linear polarization direction corresponds to the lensing effect for the second linear polarization direction (the second direction is orthogonal to the first direction).

[0031] The first and second electroactive lenses can be identical, which may be advantageous considering manufacturing costs. However, the first and second electroactive lenses can also be different. For example, in an embodiment where the diffractive lens elements of both electroactive lenses are Fresnel lens structures, the blaze axial height and / or blaze lateral position of the Fresnel lens structure of the first electroactive lens can be at least partially different from the blaze axial height and / or blaze lateral position of the Fresnel lens structure of the second electroactive lens. This helps to reduce parallax and moiré effects, for example, when viewed from an oblique direction.

[0032] Alternatively, the nematic liquid crystal material of the first electroactive lens may be different from that of the second electroactive lens. When viewed from an oblique direction, using different nematic liquid crystal materials can help reduce parallax and moiré effects. Furthermore, the choice of nematic liquid crystal material may affect the desired location of scintillation in the diffraction structure and / or may reduce the occurrence of chromatic aberration.

[0033] In an embodiment of a stack of first and second electroactive lenses, the first optically transparent substrate of the first electroactive lens and the first optically transparent substrate of the second electroactive lens are combined into a single common optically transparent substrate. The stack of electroactive lenses can then have only three substrates.

[0034] Instead of stacking two electroactive lenses on top of each other, a single electroactive lens can be provided with at least one linear polarizer. The linear polarizer is configured to allow light with a first linear polarization to pass through and substantially block light with a second linear polarization perpendicular to the first linear polarization. Furthermore, the polarizer is preferably aligned to the side of the first optically transparent layer such that the first linear polarization is substantially parallel to the alignment of the liquid crystal near the first electrode in the liquid crystal layer. In other words, the polarizer axis can be aligned with the direction of the liquid crystal director in the nematic liquid crystal (LC) material of the first electroactive lens in the on state. In this way, incident unpolarized light (when the optical device is on) will produce a magnified image of light with the first polarization along the first linear alignment direction and an unmagnified image of light with the second polarization perpendicular to the first direction. The unmagnified image can then be easily filtered out by a suitable polarizer.

[0035] In a preferred embodiment, the linear polarizer includes one or more polarizing layers attached to the first substrate and / or the first optically transparent electrode. More preferably, the linear polarizer includes a polarizing layer attached to an alignment layer and aligned to the alignment direction of the alignment layer. Note that the alignment direction can be implemented in different ways and can correspond to the friction direction when the alignment layer has undergone a rubbing operation or to the photoalignment direction when the alignment layer has undergone a photoalignment treatment.

[0036] In another embodiment, the optical device includes at least one polarizing layer formed on the LC-facing surface of the diffractive lens structure, wherein the polarization director of at least one other polarizing layer is tuned in different regions of the diffractive lens structure to match the local liquid crystal director on the lens surface.

[0037] The optical device may be in which at least one electroactive lens is configured to tune the type of focusing or dispersion of light by changing the orientation of the liquid crystal in the LC layer when a voltage is applied to an optically transparent electrode. As those skilled in the art will recognize, the voltage can be applied in different ways. A specific example of attaching the electrodes of one or more electroactive lenses to a power source (e.g., a battery disposed in different parts of the frame of a pair of glasses) is described in WO 2019 / 101966A1. Furthermore, the optically transparent electrodes of the electroactive lens may be electrically connected for simultaneously switching between a first electroactive lens and a second electroactive lens. Tuning of the focusing or dispersion of light by changing the refractive index of the LC layer in the lateral direction when a voltage is applied to the optically transparent electrode may cause a change in the optical power of the electroactive lens, as this redirects the LC director in the lateral direction.

[0038] The optical device can be configured to switch at least one electrically active lens from a state where the at least one electrically active lens substantially does not exhibit lensing function in an off state, and a state where the at least one electrically active lens exhibits lensing function in a conducting state when a voltage is applied to the optically transparent electrode of the at least one electrically active lens. Depending on the type of diffractive lens element, the lensing function may include magnifying the incident image.

[0039] In the off state, the liquid crystal in the nematic liquid crystal material is oriented such that the refractive index of the LC layer in the lateral direction substantially matches the refractive index of the diffraction structure, and / or wherein, in the on state, the orientation of the tilted liquid crystal makes the orientation parallel to the alignment direction of the alignment layer.

[0040] The optical device may include a plurality of spacers arranged in the liquid crystal layer, the spacers extending in a direction perpendicular to the plane in which the second electrode extends, and the spacers are preferably formed on the diffraction lens structure. The spacers ensure that the desired minimum and maximum thickness of the LC layer can be accurately achieved. In a particular embodiment, the spacers are configured to provide an additional height, measured from the portion of the diffraction lens structure closest to the second substrate, between 1 μm and 20 μm, preferably between 2 μm and 12 μm.

[0041] The liquid crystal material of the LC layer is preferably selected to have a birefringence Δn in the range of 0.15 to 0.40.

[0042] According to another aspect, a lens unit for eyeglasses is provided, the lens unit including a first lens portion, a second lens portion, and an optical device as defined herein, wherein an electroactive lens is disposed between the first lens portion and the second lens portion, preferably sandwiched between the first lens portion and the second lens portion.

[0043] According to another aspect, a pair of eyeglasses is provided, wherein the eyeglasses include a frame on which a first lens unit and a second lens unit or a first optical device and a second optical device as defined herein are mounted.

[0044] According to another aspect, a method is provided for operating an optical device including a first electroactive lens and a second electroactive lens as defined herein, wherein an alternating voltage is applied to a first electrode and a second electrode of the first electroactive lens and a first electrode and a second electrode of the second electroactive lens stacked on the first electroactive lens to align liquid crystal in a direction substantially perpendicular to the first substrate and the second substrate. This disclosure also relates to applications in eyeglasses, lens units, and / or optical devices as defined herein.

[0045] General description

[0046] As a uniaxial material, liquid crystals exhibit birefringence. This means that two rays of light with a certain phase delay always emerge from the liquid crystal layer:

[0047]

[0048] Where d is the thickness of the layer, λ is the wavelength of the incident light, and n e -n o =Δn is the birefringence, where n e Is it an unusual refractive index and n o It is the ordinary refractive index. The angle below... The twist angle of the liquid crystal pointer is indicated and varies linearly with the distance d along the z-direction (i.e., the thickness of the LC layer). The Mauguin condition is satisfied under the following conditions:

[0049]

[0050] A waveguide that generates input polarization occurs when the Mauguin condition is satisfied. Then, both the unusual and ordinary waves rotate along the optical axis, and the liquid crystal acts as a polarization rotator.

[0051] In a liquid crystal lens, the refractive index of the lens material can be one of the refractive indices of the liquid crystal (i.e., n). e or n oMatching. This means that there is no lensing effect for linearly polarized light in the direction of the matched refractive index. For polarized light perpendicular to it, all the light will be refracted by the lens. If unpolarized light that can be decomposed into two orthogonally polarized directions will be transmitted, then half of the light will encounter the lensing effect and half of the light will not encounter the lensing effect. Thus, a double image will be transmitted. To make all the light encounter the lensing effect, one solution is to add a second liquid crystal lens, which is perpendicular to the first liquid crystal lens. This is also proposed in US7724347 and US201715787082. However, in the two patents, the liquid crystal arrangement differs from that in this disclosure in the way the two liquid crystal layers are stacked.

[0052] In the present disclosure, the liquid crystal director is non-uniformly oriented on the substrate with the Fresnel lens structure, but uniformly oriented on the counter substrate (which does not have a Fresnel lens structure). When two lenses are stacked, if the substrate with the Fresnel lens structure is placed opposite the other lens, it is impossible to make the liquid crystal director perpendicular to the substrate on the second lens that it contacts in each part of the lens. This is only possible when the two lenses are stacked together and the counter substrates face each other.

[0053] Another solution for manufacturing an electroactive lens suitable for unpolarized light is to add a polarizer to the lens. In this case, the polarizer axis should be aligned with the liquid crystal director. Since the liquid crystal director is uniform only on the opposing substrate of the lens, the (linear)polarizer should be attached to the substrate and aligned with the liquid crystal (= rubbing or photoalignment) direction.

[0054] In another solution, a polarizer is also added to the electroactive lens. However, in this case, the polarizer is a special type where the polarizer director is tuned in different regions of the lens to match the local liquid crystal director on the lens surface. The polarizer is attached to the lens substrate. This type of polarizer can be fabricated using photoalignment (see, for example, VG. Chigrinov et al., Photoalignment of liquid crystal materials: Physics and applications).

[0055] As mentioned earlier, in order to split the original light into one polarization for magnified images and another for unmagnified images, the liquid crystal twist should be greatly extended in the waveguide state. This means that the Mauguin condition must be satisfied, which, for clarity, is rewritten here as: 0.5pΔn >> λ, where λ is the wavelength of the light and p is the pitch (equal to...). ) and Δn are the birefringence. Pitch is the length, where the pointer of the liquid crystal is twisted 360 degrees.

[0056] For example, under the given conditions, λ is the wavelength of light, typically 0.5 micrometers. Δn is the difference in refractive index along the ordinary and extraordinary axes (typically 0.2), and p is the helical pitch. This means that to satisfy the Mauguin condition, considering the alignment geometry, the helical pitch p should be much greater than 0.5 / (0.5 × 0.2) = 5 micrometers.

[0057] The amount of torsion in an electroactive lens depends on the extent to which the lens structure alters the direction of the directional vector between the two surfaces of the liquid crystal contact. In the context of this disclosure, the amount of torsion in an electroactive lens depends on the extent to which the lens structure alters the direction of the directional vector between the lens surface and the opposing substrate (opposing substrate).

[0058] The inventors used finite element numerical calculations to determine the torsional behavior of liquid crystals in electroactive lenses and found that this torsional behavior depends on the pretilt angle of the liquid crystals on the lens surface. This pretilt angle can be affected by alignment materials, friction or illumination conditions, and the surface angle of the polymer (Fresnel) lens relative to its substrate. Generally, the smaller the pretilt, the greater the torsional distortion. For example, an 87-degree pretilt on a surface oriented at a 3-degree angle perpendicular to the alignment direction results in a total torsional distortion of 45 degrees.

[0059] Considering the cross-section of the electroactive lens perpendicular to the alignment surface, the torsion value varies with the azimuth angle. When the side of the cross-section is aligned with the friction direction, the torsion between the lens and the opposing substrate should be 0 degrees. However, the torsion angle increases with the azimuth angle and can theoretically reach 180 degrees. In this case, the director on the Fresnel lens surface and the opposing substrate are oriented parallel to each other, and it is not a bending deformation of the director-selective torsion. This selection occurs when the system attempts to achieve equilibrium and the overall minimum energy state corresponds to a torsion of 180 degrees. For large torsion values, the distance between the two substrates should be greater than 2.5 micrometers. For this purpose, a spacer at least 4 micrometers higher than the flare top of a lens with a 1.5 diopter power (diameter 21 mm, Δn = 0.2) is applied.

[0060] Depending on the lens power and diameter, the height of the spacer on the top of the lens should be optimized to meet the Mauguin state across the entire lens surface.

[0061] If the waveguide / Mauguin state condition is met, the linear polarization of light is consistent with the twisting of the liquid crystal molecules. The inventors have discovered that this effect can be used to improve the quality of electroactive lenses.

[0062] Here, if linear polarization is maintained by the lens box and the linear alignment direction is applied to the opposing substrates, a uniform optical response exists on the surface. More specifically, there will be a magnified image along the linear alignment direction and an unmagnified image perpendicular to it. Therefore, if a linear polarizer is placed on this side, the unmagnified image can be filtered out without problems. Furthermore, a polarization-independent switchable lens can then be manufactured by stacking similar electroactive lenses on a first electroactive lens, provided that the two opposing substrates are oriented toward each other and placed at a 90-degree angle. Attached Figure Description

[0063] Figure 1 An embodiment of an optical device including an electroactive lens is shown;

[0064] Figure 2 The distortion of liquid crystal in an electroactive lens is shown;

[0065] Figure 3A The alignment of liquid crystals in an electroactive lens is shown;

[0066] Figure 3B The alignment of the liquid crystals in the two liquid crystal layers of the corresponding electroactive lens is shown;

[0067] Figure 4 An example of polarization-dependent magnification of an electroactive lens is shown;

[0068] Figure 5 An electroactive lens with a polarizer layer provided according to an embodiment of the present disclosure is shown;

[0069] Figure 6 An electroactive lens with a polarizer layer provided according to another embodiment of the present disclosure is shown;

[0070] Figure 7 The diagram shows a first lens section, a second lens section, and a section sandwiched between the two lens sections. Figure 5 Implementation method of the lens unit of the optical device;

[0071] Figure 8 It shows the corresponding Figure 1 An embodiment of the optical device including two stacked electroactive lenses;

[0072] Figure 9 An electroactive unit comprising two electroactive lenses stacked according to the present disclosure is shown; and

[0073] Figures 10A to 10C Several exemplary test results of an electroactive lens according to embodiments of this disclosure are shown.

[0074] Detailed description of the attached figures

[0075] In the following description, numerous specific details are set forth for illustrative purposes to provide a thorough understanding of this disclosure. However, it will be apparent that this disclosure can be practiced without these specific details. In other instances, well-known structures and apparatuses have not been described in exhaustive detail to avoid unnecessarily obscuring this disclosure.

[0076] It will be apparent to those skilled in the art, upon reading this disclosure, that each of the individual embodiments described and illustrated herein has discrete components and features that can be readily separated from or combined with features of any of the other embodiments without departing from the scope of this disclosure. Any of the described methods may be performed in the order of the events stated or in any other logically possible order.

[0077] Note that, unless the context clearly specifies otherwise, the singular forms “a,” “an,” and “the” as used herein and in the appended claims include plural indicators. It should also be noted that claims may be drafted to exclude any optional elements. Thus, this statement is intended to serve as a precondition for the use of exclusive terms such as “merely,” “only,” etc., or for the use of a negative limitation, in conjunction with the description of the elements of the claim.

[0078] Figure 1 An electroactive lens 101 is shown. The electroactive lens 101 may be part of a lens. The electroactive lens 101 includes: a first substrate 104 where a first electrode 106 is formed; a second substrate 105 where a second electrode 107 is formed; and a volume or cavity 108 enclosed between the first substrate 104 and the second substrate 106 (or between the electrodes 106 and 107 in a particular embodiment) and sealed by two boundaries 103 arranged at opposite ends of the electroactive lens 101. The first substrate 104, the second substrate 105, the first electrode 106, and the second electrode 107 may be made of an optically transparent material. For example, electrodes 106 and 107 may include indium tin oxide (ITO) layers and / or indium zinc oxide (IZO) layers. The first electrode 106 and the second electrode 107 may be connected to a power source (not shown). The power source may be configured to apply a voltage difference between the first and second electrodes when the optical device is switched on, and substantially no voltage difference between the first and second electrodes in the off state.

[0079] The sealed volume or cavity 108 between the optically transparent electrode 106 and the optically transparent electrode 107 includes a diffractive lens structure 102 and at least a nematic liquid crystal (LC) layer 113 formed of nematic liquid crystal. The cavity 108 of the electroactive lens 101 may include a diffractive lens structure in the form of a Fresnel lens structure, but other types of diffractive structures may also be used. In the illustrated embodiment, the diffractive structure 102 extends over only a portion of the width of the cavity 108, such that corresponding intermediate spaces 108a, 108b exist at the two lateral ends of the diffractive structure. However, in other embodiments, the diffractive structure extends to contact two boundaries 103 (boundaries 103 may be formed by plugs disposed between the first substrate 104 and the second substrate 105). Furthermore, the Fresnel lens structure 102 is located at the center of the cavity 108, but in other embodiments, the Fresnel lens structure may be arranged closer to either of the boundaries 103 of the electroactive lens 101. The Fresnel lens structure 103 is also made of a transparent material, such as an isotropic polymer material.

[0080] Alternatively, one or more spacers 109 may be arranged within volume 108. Spacers 109 may be arranged between Fresnel lens structure 102 and opposing electrodes 106, 107. For example, as... Figure 1 As shown, the Fresnel lens structure 102 can be arranged on the second electrode 107. Then, one or more spacers 109 are arranged between the Fresnel lens structure 102 and the first electrode 106 and extend through the volume 108. One or more spacers (not shown) can also be arranged between the electrodes 106 and 107, extending from the first electrode 106 through the volume 108 to the second electrode 107.

[0081] Furthermore, an alignment layer 111 is disposed on top of (or as part of) the first electrode 106 to align the LC material 113 within the cavity 108. Optionally, a second alignment layer 112 is disposed on top of the diffraction structure 102, i.e., on the surface of the diffraction structure 102 facing the LC material in the cavity 108. In this case, the second electrode layer exists on top of the diffraction structure rather than being disposed between the second substrate 105 and the diffraction structure 102. Figure 1 In an embodiment (not shown), the second alignment layer 102 may be a part of the second electrode 102.

[0082] Electrodes 106 and 107 are configured to change the alignment of the liquid crystal within the liquid crystal (LC) layer, thereby changing the lateral orientation of the liquid crystal (LC) layer in the electroactive lens 101. Figure 1The refractive index in the x-direction. More specifically, the refractive index in the transverse (horizontal) direction is the refractive index that needs to match or not match one of the diffraction structures. This allows for a change in the optical power of the electroactive lens 101. The alignment of the liquid crystal can be altered by activating the electroactive lens 101. The electroactive lens 101 is configured to be activated using a voltage applied to the optically transparent electrodes 106 and 107, as will be explained later.

[0083] When no voltage is applied to electrodes 106 and 107, the orientation of the liquid crystal molecules in the nematic liquid crystal (LC) is determined by the alignment layer. More specifically, the liquid crystal molecules in the nematic liquid crystal (LC) layer exhibit both in-plane and out-of-plane orientations, wherein the in-plane alignment direction of the liquid crystal is usually aligned with the direction of friction or illumination. The average uptilt angle of the liquid crystal relative to the alignment surface plane is called the (unidirectional) pretilt angle. When a voltage is applied to electrodes 106 and 107, the electric field generated between electrodes 106 and 107 will cause different alignment directions of the liquid crystal.

[0084] For example, in the first state, also referred to herein as the off state, i.e., when no voltage is applied to the optically transparent electrodes 106 and 107, the liquid crystal can orient itself in such a way that the refractive index of the LC layer in the transverse direction (x-direction) of the electroactive lens 101 substantially matches the refractive index of the diffractive lens structure 102. Therefore, the diffractive lens structure 102 and the LC layer effectively form a combined optical layer having the same refractive index in the transverse direction (x-direction) (i.e., substantially no optical interface exists in volume 108). In other words, the combined optical layer has a substantially constant refractive index in volume 108, while its refractive index varies with its width position (i.e., along the x-direction). Figure 1 The position in the x-direction shown is irrelevant. Furthermore, the combined optical layer also has two parallel surfaces. Therefore, when in the first state, the light beam incident on the electroactive lens 101 will not be collimated or dispersed.

[0085] In the second state, also referred to herein as the conducting state, i.e., when a voltage is applied to the first electrode 106 and the second electrode 107, the orientation of the liquid crystal molecules typically becomes parallel to the alignment direction of the alignment layer, resulting in an additional optical interface between the liquid crystal in the LC layer and the diffraction lens structure 102. This additional optical interface leads to a different refractive index in the composite layer. Therefore, the light beam incident on the electroactive lens 101 will be refracted by the optical interface between the diffraction lens structure 102 and the LC layer, thereby collimating or dispersing the light beam incident on the diffraction lens structure 102.

[0086] In summary, the first state can be a state where no voltage is applied to electrodes 106 and 107, and the second state is a state in which an appropriate voltage is applied to electrodes 106 and 107 such that the refractive index of the combined optical layer in the lateral direction of the electroactive element 101 matches and differs from the refractive index of the diffractive lens structure 102 (e.g., a Fresnel lens structure), respectively. Similarly, in the following description, the switched-on state refers to a state in which additional optical power is provided to the electroactive lens 101 by creating a refractive optical interface between the diffractive lens structure 102 and the liquid crystal in volume 108, while the off state refers to a state in which the refractive index of the liquid crystal in the lateral direction of the electroactive lens 101 matches the refractive index of the diffractive lens structure 102, thereby not providing additional optical power to the electroactive lens 101. Preferably, the refractive indices of the LC layer (in the off state) and the Fresnel lens structure 102 also match the refractive indices of the first substrate 104 and / or the second substrate 105.

[0087] The Fresnel lens structure 102 can be a positive Fresnel lens structure or a negative Fresnel lens structure. Preferably, the Fresnel lens structure 102 is a negative Fresnel lens structure (e.g., ...). Figure 1 (As shown in the diagram). In the application of the electroactive lens 101, the type of Fresnel lens structure 102 used can vary; for example, Fresnel lens structures 102 of different sizes, intensities, and shapes can be used. The Fresnel lens structure 102 can be disposed on an electrode 107 connected to a second substrate, or in an embodiment where the electrode is disposed on top of the Fresnel structure 102, the Fresnel structure can be connected to the second substrate. In an embodiment where the Fresnel structure 102 is disposed on the electrode 107, the Fresnel structure 102 can be formed on the electrode 107 using any technique, such as nanoimprint lithography. The Fresnel lens structure 102 can be formed from a plurality of concentric ring shapes referred to as blaze 110. The flash 110 is formed in an annular shape with a triangular cross-section, wherein one side extends in the axial direction (i.e., the z-direction) of the electroactive lens 101, an electrode of the Fresnel lens structure 102 (i.e., the xy-plane) is formed thereon on the other side, and the tilted side (which may be curved) provides a refractive optical interface between the Fresnel lens structure 102 and the liquid crystal in the on state. The shape of the flash 110 can be optimized for a specific application of the electroactive lens 101, and the examples or exemplary figures discussed above are non-limiting.

[0088] The first substrate 104 and the second substrate 105 can be bonded by applying an adhesive between them, thereby forming at least a portion of the boundary 103. The adhesive used to bond the first substrate 104 and the second substrate 105 can be, for example, NOA71 or NOA160. The boundary 103 or a portion thereof can also be formed during the formation of the Fresnel lens structure 102, for example, during a nanoimprinting step in which the Fresnel lens structure 102 is formed.

[0089] according to Figure 1 The same description as above can also be applied to Figures 5 to 7 In the embodiments shown herein, the same reference numerals may refer to the same elements.

[0090] Due to the birefringence properties of liquid crystals, such as Figure 1 Nematic liquid crystals in electroactive lenses can induce birefringence. For example... Figure 4 As shown, in the conductive state of the electroactive lens, the electroactive lens provides lens power. However, due to the birefringence of the liquid crystal, different polarizations are refracted differently. For example, points 402 and 403 ideally coincide to form a single point. However, due to the different refraction of different polarizations, these points appear separated in the magnified image 401. In the following description, according to Figures 2 to 4 This will further clarify the issue, followed by... Figure 5 , Figure 6 and / or Figure 7 How to solve this problem? Figure 8 A to Figure 8 C is an illustrative measurement demonstrating the success of the proposed solution.

[0091] Figure 2 A liquid crystal layer comprising a liquid crystal 205 disposed between two surfaces 200 and 210 is shown. As a uniaxial material, liquid crystals exhibit birefringence. This means that two rays with phase delay are always emitted from the layer:

[0092]

[0093] Where d is the layer thickness, λ is the wavelength, and n e It is an unusual refractive index, n o It is the ordinary refractive index, and (n e -n o )=Δn is the birefringence. Equation (1) and Figure 2 The angle in the middle The twist angle of the liquid crystal pointer vector varies linearly in the z-direction. This is achieved when the Mauguin condition is satisfied, i.e.:

[0094]

[0095] A waveguide generates the input polarization. Then, both the unusual and ordinary polarizations of the incident light follow the rotation of the optical axis, and the liquid crystal 205 acts as a polarization rotator.

[0096] According to Figure 1 In the liquid crystal layer of the described electroactive lens, the refractive lens material 102 and one of the refractive indices of the liquid crystal (i.e., n) e or n o Matching. This means that there is no lensing effect for linearly polarized light in the matched refractive index direction. For polarized light with polarization perpendicular to it, all light will be refracted by the lens. If unpolarized light, which can be described as the superposition of light in two orthogonal polarization directions, is transmitted, then half of the light will encounter lensing and half will not. Therefore, a double image will be transmitted.

[0097] In other words, the birefringent liquid crystal 205 is disposed between surface 201 and surface 210, and the liquid crystal 205 tends to be distorted at a distance d. As described above, when the Mauguin condition is satisfied, the liquid crystal 205 guides (waveguides) the input polarization. Therefore, for example, if light is incident on the transparent surface 200 in the z-direction, the polarization of the light in the x-direction will experience a different refractive index of the liquid crystal layer, rather than a different polarization of light having a polarization direction in the y-direction (at surface 200).

[0098] The distortion of the liquid crystal 205 can be affected not only by the thickness of the layer between surface 200 and surface 210, but also by known methods such as frictional or photoalignment of the alignment layer. Furthermore, the orientation of the second surface 210 relative to the first surface 200 also affects the distortion of the liquid crystal 205. For example, if the second surface is rotated in the yz plane, the liquid crystal 205 will distort in a different way than it currently does. Figure 2 Rotate as shown. For example, this might happen at position 110.

[0099] This can be done Figure 3A The image shows a lens profile 300. Such a lens profile can include, for example... Figure 1The electroactive lens 101 is an electroactive lens. In the lens of FIG. 3, both the first electrode 106 and the Fresnel structure 102 disposed on the second electrode 107 are provided with alignment layers, such that these alignment layers are aligned in direction 306. This may cause the liquid crystals on the first electrode 106 and the Fresnel structure 102 to be aligned in direction 306. However, the Fresnel structure 102 does not provide a surface parallel to the surface of the first electrode 106, so as schematically shown by arrows 301, 302, 303, 304 and 305, the surface of the Fresnel structure 102 affects the orientation of the liquid crystals thereon. Even though the alignment in the middle of the lens profile 300 (shown by arrow 301) is parallel to the alignment direction 306, the alignment of the liquid crystals in the first lower left orientation 302, the first lower right orientation 303, the first upper left orientation 304 and the first upper right orientation 305 have a large component that is not parallel to the friction direction (306). Therefore, using a linear polarizer will not be sufficient to obtain a single image, because the outgoing light includes multiple polarizations that have passed through the different refractive properties of the birefringent liquid crystal.

[0100] It can be assumed that the above problem can be solved by placing another electroactive lens on the electroactive lens of profile 300, for example... Figure 1 Component 101 is used to solve the problem of obtaining a stack of two components with contour 310, such as Figure 3B The above description also applies to the other electrically active lens, however, which will be aligned in a direction 316 orthogonal to the alignment direction 306. In fact, the first central orientation 301 is orthogonal to the second central orientation 311, and therefore, polarization-independent refraction is obtained near the center of the lens profile 310. However, away from the center, for example, where the first lower left orientation 302 and the second lower left orientation 312 overlap, their mutual alignment is not orthogonal, producing different refractions for two different ellipsoidal polarizations. Therefore, in the region where the first lower left orientation 302 and the second lower left orientation 312 overlap, the lens produces a double image. The same applies to the regions where the first lower right orientation 303 and the second lower right orientation 313 overlap, the regions where the first upper left orientation 304 and the second upper orientation 314 overlap, and the regions where the first upper right orientation 305 and the second upper right orientation 315 overlap.

[0101] In other words, light can be decomposed into two independent polarization states (two linear, two circular, or two elliptical), and unpolarized light consists of a superposition of these two states. Liquid crystals are composed of elongated molecules with different refractive index values ​​along different axes. When a single lens box is used with ideal linear alignment on the top and bottom surfaces, in the conductive state, linear polarization in the longitudinal direction of the molecules experiences a lensing effect, while other polarizations orthogonal to the linear polarization will not experience a lensing effect. Therefore, the image obtained through the lens is a dual image, namely a magnified image and an unmagnified image.

[0102] However, by placing a linear polarizer parallel to the linear alignment direction, the unmagnified image can be filtered out. With a double-stacked lens box at a 90-degree angle, two polarizations are added, and the overall incident unpolarized light is magnified. However, in reality, although the linear alignment in the lens box is desired, the lens introduces a deviation. As a result, a position-dependent distortion exists, causing the linear polarization to change to a position-dependent elliptical polarization (e.g., ...). Figure 3B The position-dependent elliptically polarization states are shown in the diagram. Therefore, it is impossible to filter out the unmagnified image with the aid of a linear polarizer. More specifically, elliptically polarizations generated from independent linear polarizations (where each polarization includes either a magnified or unmagnified image) cannot be further decomposed using a linear polarizer.

[0103] Furthermore, it is difficult to fabricate a completely polarization-independent lens using two stacked boxes. After all, at each location, it is necessary to ensure that the polarization change in both boxes is the same but rotated by 90 degrees, which is achieved through methods such as... Figure 3B The two identical lens boxes shown are impossible.

[0104] Figure 4 It shows, for example, according to Figure 1 The image shows the electroactive lens 101 in its off state according to the discussed embodiment. In the off state, the uniaxial liquid crystal molecules are preferably aligned in the axial direction of the electroactive lens 101, that is, in a direction substantially perpendicular to the surface of the first electrode 106. Therefore, in this state, the refractive index of the liquid crystal matches the refractive index of the Fresnel lens structure 102. Therefore, there is no lensing effect in the off state. Image 401 shows an image of a light screen including a plurality of black dots arranged in a repeating pattern (as seen through the electroactive lens 101). Here, the dots in the screen are also considered as a repeating pattern. Pattern 401 is the same pattern of dots arranged on the screen.

[0105] If the electroactive lens 101 is switched on, the liquid crystal is preferably aligned radially, i.e., aligned in a direction substantially parallel to the surface of the first electrode 106. Therefore, the refractive index of the liquid crystal does not match the refractive index of the Fresnel lens structure 102, and a lensing effect is achieved. As shown in image 401, an image comprising multiple points of light is magnified. However, the magnification is different for two orthogonal polarizations. For example, points 402 and 403 are independent points belonging to different polarizations; ideally, these points would coincide to form a single point, i.e., ideally, polarization-independent magnification is achieved.

[0106] Since this problem mainly occurs in states where an electric field is applied to the liquid crystal layer by electrodes, the following description will refer to such states unless otherwise explicitly stated.

[0107] Figure 5 An embodiment of the electroactive lens 501 in which the aforementioned problems have been solved is shown. The electroactive lens 501 basically includes... Figure 1 The same components as the electroactive lens 101 are indicated by similar reference numerals (400). To avoid obscuring the scope of this disclosure, the same descriptions applicable to this drawing are not repeated herein. The electroactive lens 501 includes (from top to bottom in the figure) a first substrate 504, a first electrode layer 506, an alignment layer 506, a cavity 508 filled with an LC material layer 513 and a diffraction structure 502, other alignment layers 512, a second electrode layer, and a second substrate 505. Additionally, the electroactive lens 501 includes a polarizer layer 560 disposed between the first substrate 504 and the electrode layer 506.

[0108] Figure 6 Another embodiment of the electroactive lens 801 in which the aforementioned problems have also been solved is shown. The electroactive lens 801 basically includes... Figure 5 The same components as the electroactive lens 501 are indicated by similar reference numerals (denoted by 300). To avoid obscuring the scope of this disclosure, the same descriptions applicable to this drawing will not be repeated herein. Additionally, the electroactive lens 801 includes a polarizer layer 860, the function of which will be described later. In this embodiment, the polarizer layer 860 is disposed on top of the first substrate 604 (i.e., at the outer surface of the first substrate 804).

[0109] Figure 7 The diagram shows a lens assembly arranged between two lens components 651 and 652. Figure 5 An exploded view of the lens unit 650 of the optical device. Two of these lens units 650 can be arranged in the frame of a pair of glasses worn by a person, and allow the person to change the optical power of the lens unit between the off state and the on state.

[0110] exist Figures 5 to 7In this embodiment, linear polarizers forming polarizer layers 560, 860 are provided. The polarizing layers are configured to allow a first linear polarization to pass through and substantially block a second linear polarization orthogonal to the first linear polarization. Furthermore, the polarizer layers are aligned such that the first linear polarization is substantially parallel to the alignment of the liquid crystal near the first electrodes 506, 806 in the liquid crystal layers 508, 808. For example, the linear polarizers 560, 860 can allow the polarization of electromagnetic waves traveling in the axial (z) direction in a first lateral direction (e.g., the x-direction) to pass through, while blocking polarization in a second lateral direction (e.g., the y-direction perpendicular to both the first lateral direction and the z-direction, i.e., perpendicular to the xz plane). In this example, the liquid crystal near the first electrodes 506, 806 is aligned in the x-direction. Furthermore, the thickness d0 of the liquid crystal layers 508 and 808, measured from the outer surface of any scintillation 510 of the diffraction structures 502 and 802 (or the outer surface of any scintillation of the second alignment layer disposed on top of the diffraction structures 502 and 802) to the outer surface of the alignment layers 561 and 861 facing the cavity 508, ensures that the liquid crystal layers satisfy the Mauguin condition (Equation 1). Therefore, it prevents conditions such as... Figure 4 The dual image 401 shown.

[0111] Those skilled in the art will recognize that the thickness d0 can also be chosen such that the Mauguin condition (Equation 1) is not fully satisfied; however, waveguide effects will still occur to some extent. For example, for thickness d0, Where f≥1, the influence of the polarization state can be evaluated using the well-known Gooch-Tarry alternative condition of a 90° twist. The transmission of such a twisted box placed between parallel polarizers is calculated as a function of thickness d (see Figure X). Transmission is obtained by equation... A series of minimum values ​​for control, where M is an integer [Reference: Gooch, CH and Hatarry. "The optical properties of twisted nematic liquid crystal structures with twist angles less than or equal to 90 degrees." Applied Physics, Vol. 8 (1975): 1575-1584].

[0112] In many devices, a first minimum transmission value is used to define the required minimum thickness; however, a major drawback here is that the first minimum applies only to a single wavelength. Physically, this means that for a thickness of the first minimum, the resulting polarization state is not purely linear for most other wavelengths. Generally, the polarization state will be elliptic, with its major contribution still along the preferred direction (i.e., the alignment direction on the opposing substrate). By increasing the integer M and calculating over multiple wavelengths, an optimal thickness d0 with nearly similar transmission values ​​is obtained, and the waveguide condition can be considered sufficiently satisfied. Therefore, when replacing the thickness value on the left side of the Mauguin condition, depending on the purity of the desired resulting polarization state, the target wavelength range, and the birefringence of the LC material, f can be found to be approximately 1, 2, 5, or 10.

[0113] The above solution can still largely solve this problem because, measured from the portion closest to the first electrode 506, the thickness of most areas of the liquid crystal layer 508 is substantially greater than d0.

[0114] Furthermore, the polarizing layer 560 can be placed between the first substrate 504 and the first electrode 506 (e.g., Figure 5 (as shown), between the first electrode 806 and the first alignment layer 811 or on the top of the first substrate 804 (as shown). Figure 6 ).

[0115] In principle, a polarizer layer can also be disposed on the side of the second substrates 505, 805 (e.g., between the second substrate and the diffraction structure). In this case, a position-dependent quasi-spherical polarizer layer should be added. Such a position-dependent quasi-spherical polarizer can be specifically formed to filter out one of the polarization directions of the light emitted from the Fresnel lens structures 502, 802 after passing through the first substrates 504, 804, the first electrodes 506, 806, the alignment layers 511, 811, and the liquid crystal layers 508, 808. The position-dependent quasi-spherical polarizer will have a spherical shape to accurately filter the non-refractive polarization component of the emitted light. For this purpose, the electroactive lens 501 will have a specific pattern. For example, referring to Figure 3, when a position-dependent quasi-spherical polarizer is incorporated into an electrically active lens having a profile 300, it will block light with polarization directions perpendicular to each of arrows 301, 302, 303, 304, and 305 at the respective locations of arrows 301, 302, 303, 304, and 305. This will require measuring the polarization direction of light emitted from the Fresnel lens structure 502 at each location in the electrically active lens (in the xy plane) for each thickness d0, each Fresnel lens structure 502, and each liquid crystal layer, and forming the position-dependent quasi-spherical polarizer based on such measurements.

[0116] Furthermore, also in the embodiment described above where the polarizer layer is located on the side of the second substrate, the second solution is to measure the thickness d0 of the liquid crystal layer from any end of the scintillation 510 to the opposite end of the liquid crystal layer 508 (i.e., near the first electrode 506) such that the liquid crystal layer satisfies the Mauguin condition (Equation 1). Therefore, it prevents, for example... Figure 4 The dual images shown.

[0117] Those skilled in the art will recognize that the thickness d0 can also be chosen such that the Mauguin condition (Equation 1) is not fully satisfied; for example, the thickness d0 can be partially satisfied, i.e. Where f ≥ 1, for example, f can be approximately 1, 2, 5, 10, or preferably between 5 and 10 or > 10. The above solution can still substantially solve the problem because, measured from the portion of the shimmering 510 closest to the first electrode 506, the thickness of most areas of the liquid crystal layer 508 is substantially greater than d0.

[0118] Those skilled in the art will recognize that the first and second solutions can be combined. This can adequately address the problems discussed above. However, in some embodiments, having two polarizing layers, thereby reducing the intensity of light transmission, may not be preferred.

[0119] Figure 8 A third solution to the aforementioned problem is shown. In the embodiment of this figure, the electroactive lens 601 and the electroactive lens 601' essentially include... Figure 1 The same components as the electroactive lens 101 (i.e., lenses without one or more polarizer layers) are indicated by similar reference numerals (denoted by the number 500). In order not to obscure the contents of this disclosure, the same descriptions that also apply to these figures are not entirely repeated herein.

[0120] Figure 8 An optical device 600 is shown, comprising a first electroactive lens 601 and a second electroactive lens 601' stacked on top of the first electroactive lens 601. Figure 1Similar to the electroactive lens 101, the first electroactive lens 601 and the second electroactive lens 601' each include: a first optically transparent substrate 604 and a second optically transparent substrate 605; a first optically transparent substrate 604' and a second optically transparent substrate 605'. As shown, the first optically transparent substrates 604, 604' and the second optically transparent substrates 605, 605' extend substantially parallel to each other and define the axial (z) direction and the lateral (x, y) direction. The first electroactive lens 601 and the second electroactive lens 601' are stacked such that the second substrates 605, 605' of each of the electroactive lenses 601, 601' are located on the outer side of the stack, and each of the first substrates 604, 604' is arranged on the inner side of the stack.

[0121] The first electroactive lens 601 is optically connected to another electroactive lens 601', that is, the second substrate 604 is optically coupled to another second substrate 604', such that preferably there is no optical interface between the two substrates. According to... Figure 5 Similar to the electroactive lenses discussed earlier, the first electroactive lens 601 and the other electroactive lens 601' each have thicknesses d1 and d2, respectively, measured from the diffraction structure 602 or 602' (or the alignment layers 612, 612' disposed thereon) to the alignment layers 611, 611' of the electrodes opposite the diffraction lens structure (i.e., the electrode 606 of the first electroactive lens 601 or the electrode 606' of the second electroactive lens 601'). Each of the thicknesses d1 and d2 causes the liquid crystal layer 613 of the first electroactive lens 601 and the liquid crystal layer 613' of the second electroactive lens 601' to satisfy the Mauguin condition (Equation 1). Therefore, to a considerable extent, at least the following conditions are reduced or prevented: Figure 4 The dual image 401 shown.

[0122] The first electrode 606 and the other first electrode 606' each include alignment layers 611 and 611', such as polyimide layers treated by, for example, friction. The alignment of liquid crystals on the opposing surfaces of alignment layers 611 and 611' is orthogonal to each other. For example, the liquid crystal in the first liquid crystal layer 613 is aligned in the x-direction on the surface of alignment layer 611 near the first electrode 606, while the liquid crystal in the second liquid crystal layer 613' is aligned in the y-direction (not shown, perpendicular to the x and z directions) on the surface of alignment layer 611' near the other first electrode 606'. Therefore, if the first polarization of light incident on the first electrically active lens 601 is amplified by the first electrically active lens 601, while the second polarization (orthogonal to the first polarization direction) of light incident on the first electrically active lens 601 is not amplified, then the amplified first polarization of light incident on the other electrically active lens 601' is not further amplified by the other electrically active lens 601', while the second polarization of light incident on the other electrically active lens 601' is amplified. Thus, the first electrically active lens 601 and the other electrically active lens 601' constitute an optical device 600, jointly providing polarization-independent amplification.

[0123] For manufacturing purposes, it may be preferred if d1 and d2 are the same, or even if the first electroactive lens 601 and the other electroactive lens 601' are substantially the same. Therefore, the two elements can be formed using the same manufacturing process parameters. However, in some embodiments, d1 and d2 can be different (i.e., the blaze height can be different if the diffraction lens element is a Fresnel lens element). Even the blaze position of the Fresnel lens element of the first electroactive lens can differ from the blaze position of the Fresnel lens element of the second electroactive lens. For example, the blaze height may be slightly different in the two electroactive lenses when perfect alignment of the blaze edges is not required. However, in a preferred embodiment, the optical power of the first electroactive lens 601 is the same as that of the second electroactive lens 601'.

[0124] This third solution offers an advantage over the first and second solutions in that the intensity of light incident on the electroactive lenses 601 and 601' is substantially conserved, whereas the first and second solutions suffer from reduced light intensity due to at least one polarizer. On the other hand, the units according to the first and second solutions may be relatively thinner than those according to the third solution. Depending on the application, the first, second, and third solutions, or any combination thereof, can be applied.

[0125] Depending on the size of the electroactive lens and the desired optical quality, the alignment layer on top of the diffractive lens structure (e.g., alignment layer 512) may also include a pre-tilt, the preferred orientation of which is parallel to the linear alignment direction of the alignment layer on the first electrode. Introducing this pre-tilt typically reduces the twist angle value and thus increases the Mauguin condition value. This will result in better optical performance.

[0126] Figure 9 yes Figure 8 A schematic exploded view of the electroactive unit. For illustrative purposes, several components are omitted in this document. The first electroactive lens 701 and the other electroactive lens 711 are actually optically connected.

[0127] A liquid crystal layer and a Fresnel lens structure (not shown) are disposed between the second electrode 707 and the first electrode 706. The distance between the second electrode 707 and the first electrode 706 is such that the liquid crystal disposed therebetween satisfies the Mauguin condition (Equation 1). The first electrode 706 is provided with an alignment layer schematically shown by 730. The liquid crystal is aligned parallel to the alignment direction 730 on the first electrode 706. On the second electrode 707, the liquid crystal can be aligned according to schematic pattern 731 due to the geometry of the first Fresnel lens structure (not shown). This schematic pattern can be a star shape starting from the center. Note that the alignment pattern on the second electrode 707 may also be different due to friction, for example, with surfaces in contact with the liquid crystal near the second electrode 707 (e.g., the surface of the Fresnel lens structure or electrode 707 or the layer disposed thereon (excluding the liquid crystal layer)). For example, due to friction with surfaces near the electrode 707, the alignment on the electrode may be similar according to... Figure 3A The orientations discussed.

[0128] A liquid crystal layer and a Fresnel lens structure (not shown) are disposed between another second electrode 717 and another first electrode 716. The distance between the other second electrode 717 and the other first electrode 716 is such that the liquid crystal disposed therebetween satisfies the Mauguin condition (Equation 1). The other first electrode 716 is provided with an alignment layer schematically shown by 740. In order to obtain a uniform linear polarization state at the other first electrode 716, the liquid crystal in the other electroactive lens 711 will be aligned parallel to the alignment direction 740 on the other first electrode 716. On the other second electrode 717, the liquid crystal can be aligned according to the schematic pattern 741 due to the geometry of the second Fresnel lens structure (not shown). Note that the alignment pattern on the other second electrode 717 may also be different due to friction, for example, with the surface in contact with the liquid crystal near the other second electrode 717 (e.g., the surface of the Fresnel lens structure or electrode 717 or the layer disposed thereon (excluding the liquid crystal layer)). For example, due to friction with the surface near the electrode 717, the alignment on the electrode may be similar according to the pattern 740. Figure 3A The orientations discussed.

[0129] The alignment direction 730 is orthogonal to the alignment direction 740 of the other first alignment direction. Therefore, as discussed above, if the first polarization is amplified by the first electroactive lens 701 and the second polarization direction (orthogonal to the first polarization direction) is not amplified, then the second polarization is amplified by the other electroactive lens 711 and the first polarization direction (orthogonal to the first polarization direction) is not amplified. Thus, both orthogonal polarization directions are amplified, achieving polarization-independent amplification.

[0130] Exemplary Implementation

[0131] In the following non-limiting examples, for instance, the lens diameter is 21 mm, that is, the Fresnel lens structure (e.g., 102, 502, 602 and 612) has a diameter of 21 mm in both the x and y directions.

[0132] Besides the birefringence of the liquid crystal and the maximum torsion within the cell, the cell thickness is also an important parameter. To ensure the Mauguin state is achieved throughout the lens and the thickness varies within the Fresnel blaze, it is important to design the spacer height at the top of the Fresnel lens structure to be sufficiently high. In this way, the state preferably reaches above the highest point of the blaze.

[0133] This state allows for the complete specification of the linear alignment direction on the lens surface, using only the circularly symmetrical alignment obtained through the application of an isotropic alignment layer that has not been rubbed or subjected to photoalignment treatment. However, this may still be the case in some implementations. After all, there are trade-offs between the spacer height on the top of the lens, the degree to which the Mauguin state is achieved, and the switching voltage and speed of the lens. A certain spacer height and (quasi-)linear alignment direction on the lens surface (such as...) Figure 3A A lens box with a (quasi)linear alignment direction and a smaller spacer height can have better optical quality than an identical lens box with a circularly symmetrical alignment direction because the former is more deeply in the Mauguin state. A lens box with a (quasi)linear alignment direction and a smaller spacer height can have similar optical quality to a lens box with a circularly symmetrical alignment direction, but switches between the off and on states faster.

[0134] To test the electroactive lens, the Hartmann test was used. A matrix of projection points (e.g., ...) was used. Figure 4 The contrast value (as shown) is used to determine the quality of the electroactive lens. In the following example, the electroactive lens is divided into three concentric zones from the inside out: C1, C2, and C3. The average contrast value of the entire zone summarizes the quality of the entire zone.

[0135] Example 1 (not based on this disclosure)

[0136] The Hartmann test image of the electroactive lens in the off state shows almost no Mauguin state. This electroactive lens has a blaze height of 16 μm, an additional spacer height of 3 μm, and a liquid crystal with Δn = 0.2. The electroactive lens is rubbed on both sides of the liquid crystal layer. Assuming linear alignment of the LC on the top substrate with the alignment direction towards the lower substrate (approaching a Fresnel lens structure), this alignment approximates... Figure 3A Orientation within. The result of the off state is as follows: Figure 4 As shown in item 400. In the on state, the image is similar to item 401, where the unmagnified image and the magnified image are superimposed on each other.

[0137] Example 2 (not based on this disclosure)

[0138] The electroactive lens in the off state has almost no Mauguin state. Figure 10A The electroactive lens in this example is essentially the same as the electroactive lens in Example 1. Figure 10A The conduction state is shown, supplemented by the corresponding contrast values ​​at each point of the Hartmann test. The results were obtained using a linear polarizer on the side of the upper substrate, parallel to the linear alignment direction of the upper substrate. As can be seen from the values ​​C1, C2, and C3, the contrast values ​​are only moderate.

[0139] from Figure 10A It can be concluded that the value of C1 is 0.553 and corresponds to region AA1, the value of C2 is 0.434 and corresponds to region AA2, and the value of C3 is 0.377 and corresponds to region AA3. Example 3 (First solution according to this disclosure)

[0140] The electroactive lens in the conducting state is in the Mauguin state. Figure 10B This example relates to an electroactive lens in the Mauguin state, wherein the surface of a Fresnel lens structure is rubbed. The blaze height is 15 micrometers, with an additional spacer height of 10 micrometers and Δn = 0.25. The electroactive lens is measured using a linear polarizer on the side of the upper substrate, parallel to the linear alignment direction of the opposing electrode substrate. Because the maximum torsion of the electroactive lens is finite, the electroactive lens has an optimal contrast value (in Examples 2 through 4).

[0141] from Figure 10B It can be seen that the value of C1 is 0.532 and corresponds to region BA1, the value of C2 is 0.48 and corresponds to region BA2, and the value of C3 is 0.453 and corresponds to region BA3. Example 4 (First solution according to this disclosure)

[0142] The electroactive lens in the conducting state is in the Mauguin state. Figure 10C This example relates to an electroactive lens in the Mauguin state, where there is no friction on the surface of the Fresnel lens structure. The blaze height is 15 micrometers, with an additional spacer height of 10 micrometers and Δn = 0.25. The electroactive lens was measured using a linear polarizer on the side of the upper substrate, parallel to the linear alignment direction of the opposing electrodes. The electroactive lens exhibits better contrast values ​​than the second example, primarily in the outer C3 region.

[0143] from Figure 10C It can be seen that the value of C1 is 0.562 and corresponds to region CA1, the value of C2 is 0.487 and corresponds to region BA2, and the value of C3 is 0.442 and corresponds to region CA3.

[0144] Based on the above examples, it can be objectively and quantitatively demonstrated that the present disclosure does indeed improve the quality of electroactive lenses.

[0145] It should be understood that this disclosure is not limited to the specific aspects described, and therefore may vary. It should also be understood that the terminology used herein is for the purpose of describing specific aspects only and is not intended to be limiting, as the scope of this disclosure will be limited only by the appended claims.

Claims

1. An optical device for eyeglasses, the optical device comprising a first electroactive lens for tunable light transmission, the first electroactive lens comprising: - A first optically transparent substrate and a second optically transparent substrate, wherein the first optically transparent substrate and the second optically transparent substrate extend substantially parallel to each other; - A diffractive lens structure, wherein the diffractive lens structure is arranged between the first optically transparent substrate and the second optically transparent substrate on the side of the second optically transparent substrate; - A first optically transparent electrode formed on the first optically transparent substrate and including a first alignment layer, and a second optically transparent electrode formed on the second optically transparent substrate or the diffractive lens structure and including a second alignment layer; Wherein, the axial (z) direction is locally perpendicular to the orientation of the surfaces of the first alignment layer and the second alignment layer at each position on the surface, and the transverse (x, y) direction is perpendicular to the axial direction; - A sealed cavity (108) between the first optically transparent substrate and the second optically transparent substrate, wherein, in the sealed cavity, at least a liquid crystal LC layer of the diffractive lens structure and the nematic liquid crystal LC material is arranged, and wherein, the liquid crystal in the nematic LC material is substantially axially aligned in the off state; The first alignment layer has a contact surface that contacts the LC layer and is configured to linearly align the liquid crystal in the nematic LC material in the on-state in a first lateral direction by introducing a pre-tilt in the off state. - A polarizing element configured to adjust light having polarization along a second lateral direction perpendicular to the first lateral direction; The LC layer of the nematic LC material has a thickness D measured between the portion of the diffraction lens structure closest to the first optically transparent electrode and the contact surface of the first alignment layer on the first optically transparent electrode. Wherein, the thickness D is selected to satisfy the condition n o n is the ordinary refractive index of the LC layer. e φ is the unusual refractive index of the LC layer, φ is the twist angle of the liquid crystal director of the LC layer, and λ is the wavelength of the light, with the wavelength λ ranging from 350 nm to 750 nm.

2. The optical device according to claim 1, wherein, The diffractive lens structure disposed between the first optically transparent substrate and the second optically transparent substrate is disposed on the side of the second optically transparent substrate at the second optically transparent electrode.

3. The optical device according to claim 1 or 2, wherein, The polarization element includes a second electroactive lens stacked on the first electroactive lens. The second alignment layer of the first electroactive lens has a contact surface that contacts the LC layer and is configured to linearly align the liquid crystal in the nematic LC material in a first lateral direction. The second alignment layer of the second electroactive lens has a contact surface that contacts the LC layer and is configured to linearly align the liquid crystal in the nematic LC material in the second lateral direction. Wherein, the first lateral direction is perpendicular to the second lateral direction.

4. The optical device according to claim 3, wherein, The first electroactive lens and the second electroactive lens are stacked on top of each other, such that the second optically transparent substrate is disposed on the outside of the stack and the first optically transparent substrate is disposed on the inside of the stack.

5. The optical device according to claim 3, wherein, The first optically transparent substrate of the first electroactive lens and the first optically transparent substrate of the second electroactive lens are combined into a single common optically transparent substrate.

6. The optical device according to claim 3, wherein, The optical power of the first electroactive lens corresponds to the optical power of the second electroactive lens.

7. The optical device according to claim 3, wherein, The diffractive lens structure is a Fresnel lens structure, wherein the blaze axial height and / or blaze lateral position of the Fresnel lens structure of the first electrically active lens are at least partially different from the blaze axial height and / or blaze lateral position of the Fresnel lens structure of the second electrically active lens.

8. The optical device according to claim 3, wherein, The diffraction lens structure of the first electroactive lens faces the diffraction lens structure of the second electroactive lens.

9. The optical device according to claim 3, wherein, The first electroactive lens and the second electroactive lens are the same.

10. The optical device according to claim 3, wherein, The nematic LC material of the first electroactive lens is different from that of the second electroactive lens.

11. The optical device according to claim 1 or 2, comprising a linear polarizer configured to allow light having a first linear polarization to pass through and substantially block light having a second linear polarization perpendicular to the first linear polarization, wherein, The linear polarizer is aligned such that the first linear polarization is substantially parallel to the alignment of the liquid crystal near the first optically transparent electrode in the LC layer.

12. The optical device according to claim 11, wherein, The first linear polarization is parallel to the first transverse direction (x), and the second linear polarization is parallel to the second transverse direction (y) which is perpendicular to the first transverse direction.

13. The optical device according to claim 11, wherein, The linear polarizer includes one or more polarizing layers attached to the first optically transparent substrate and / or attached to the first optically transparent electrode.

14. The optical device of claim 11, comprising at least one polarizing layer formed on the surface of the diffractive lens structure facing the LC layer, wherein, The polarization pointer of the at least one polarization layer is tuned in different regions of the diffractive lens structure to match the local liquid crystal pointer on the lens surface.

15. The optical device according to any one of claims 1-2, 4-10, and 12-14, wherein, The diffractive lens structure or the second optically transparent electrode includes additional alignment layers configured to linearly align the liquid crystal in the nematic LC material in the first transverse direction in the on state by introducing pre-tilt in the off state.

16. The optical device according to any one of claims 1-2, 4-10, and 12-14, wherein, At least one electroactive lens is configured to tune the focusing or dispersion of light by changing the orientation of the liquid crystal in the LC layer when a voltage is applied to the first optically transparent electrode and the second optically transparent electrode.

17. The optical device according to claim 16, wherein, The at least one electroactive lens is configured to change the optical power of the electroactive lens by changing the refractive index of the LC layer in the lateral direction when a voltage is applied to the first optically transparent electrode and the second optically transparent electrode.

18. The optical device of claim 16, configured to switch the at least one electrically active lens from a state in which the at least one electrically active lens substantially does not exhibit lensing in an off state, and a state in which the at least one electrically active lens exhibits lensing in an on state when a voltage is applied to the first optically transparent electrode and the second optically transparent electrode of the at least one electrically active lens.

19. The optical device according to any one of claims 1-2, 4-10, 12-14, and 17-18, wherein, In the off state, the liquid crystal in the nematic LC material is oriented such that the refractive index of the LC layer in the lateral direction substantially matches the refractive index of the diffraction lens structure, and / or wherein, in the on state, the liquid crystal is tilted so that the orientation becomes parallel to the alignment direction of the alignment layer.

20. The optical device according to claim 3, wherein, The first and second optically transparent electrodes of the electroactive lens are electrically connected to simultaneously switch between the first and second electroactive lenses.

21. The optical device according to any one of claims 1-2, 4-10, 12-14, 17-18, and 20, wherein, Multiple spacers are arranged in the LC layer and extend in a direction perpendicular to the plane from which the second optically transparent electrode extends.

22. The optical device according to claim 21, wherein, The spacer is formed on the diffractive lens structure.

23. The optical device according to claim 22, wherein, The spacer is configured to provide an additional height, measured from the portion of the diffractive lens structure closest to the second optically transparent substrate, between 1 μm and 20 μm.

24. The optical device according to claim 16, wherein, The LC material of the at least one electroactive lens has a birefringence Δn in the range of 0.15 to 0.

40.

25. The optical device according to any one of claims 1-2, 4-10, 12-14, 17-18, 20, and 22-24, wherein, The optical device is configured to provide polarization-independent light transmission.

26. A lens unit for eyeglasses, the lens unit comprising a first lens portion, a second lens portion, and an optical device according to any one of the preceding claims, wherein, The electroactive lens is arranged between the first lens portion and the second lens portion.

27. A pair of eyeglasses comprising a frame, wherein a first lens unit and a second lens unit according to claim 26, or a first optical device and a second optical device according to any one of claims 1 to 25, are mounted thereon.

28. Application of an optical device according to any one of claims 1 to 25.

29. A method of operating an optical device according to any one of claims 3 to 10, wherein, An alternating voltage is applied to the first and second optically transparent electrodes of the first electroactive lens and the first and second optically transparent electrodes of the second electroactive lens stacked on the first electroactive lens, so that the liquid crystal is aligned in a direction substantially perpendicular to the first and second optically transparent substrates.

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