Electrically switched liquid crystal cells, contact lenses, and related methods

Abstract

An electrically switchable liquid crystal cell (10) is provided, as well as a lens (50) comprising the cell and a method of manufacturing the cell. The liquid crystal cell (10) comprises a diffractive optical element (12) and a liquid crystal material (14) switchable between an unmatched state and a matched state. In the mismatched state, the effective refractive index of the liquid crystal material (14) is different from the refractive index of the substrate (18) of the diffractive optical element (12). In the matched state, the effective refractive index of the liquid crystal material (14) is matched to the refractive index of the substrate (18). In the matched state, the diffractive optical element does not promote the power of the lens. The diffractive optical element (12) has a plurality of peaks (20) and valleys (30) having rounded corners.

Description

Technical Field

[0001] The present disclosure relates to ophthalmic contact lenses. More particularly, but not exclusively, the present disclosure concerns an electrically switchable ophthalmic contact lens. Background Art

[0002] Presbyopia, the inability of the eye to focus on nearby objects due to hardening of the lens in the eye, affects almost everyone as people age. Reading glasses with a power between +1.0 and +3.0 diopters for myopia have provided a solution to this problem for many years, as have bifocal or multifocal glasses, which have the added advantage of being able to provide additional correction power for other conditions such as myopia, so that only one pair of glasses need be worn for both myopia and hyperopia.

[0003] For patients with presbyopia, multifocal contact lenses represent a further improvement. For example, multifocal contact lenses with a pattern of concentric rings are known, in which a central area is for near or far vision, and the surrounding rings alternate between near and far vision prescriptions. The image quality of these multifocal contact lenses is poor, and not all users can adapt.

[0004] Ophthalmic contact lenses with electronic components are increasingly being developed. For example, cholesteric liquid crystals (nematic liquid crystals that have been doped with chiral dopants) have been used to form contact lenses with 'tunable' diffractive optical elements. Such liquid crystals are well known to those skilled in the art (liquid crystal science) and may include, for example, E7, BL037 and / or BL038. Chiral dopants are also well known to those skilled in the art of liquid crystal science and include Merck ZLI-3786, CB15 and S811.

[0005] By virtue of associated lens circuitry, a contact lens incorporating such a tunable diffractive optical element can be electrically switched between diffractive and non-diffractive states, thereby providing a multifocal contact lens having two alternatively switchable optical powers.

[0006] A known problem with this arrangement is that it is difficult to achieve acceptable optical performance without introducing unwanted light scattering produced by the diffractive optical element. Furthermore, these contact lenses are difficult to manufacture.

[0007] The present disclosure seeks to provide an improved liquid crystal cell and contact lens comprising a diffractive optical element. Summary of the invention

[0008] According to a first aspect of the present disclosure, there is provided an electrically switchable liquid crystal cell for changing the focal power of a contact lens, the liquid crystal cell comprising a diffractive optical element switchable between an unmatched state and a matched state, wherein:

[0009] In the mismatched state, the effective refractive index of the liquid crystal cell is different from the refractive index of the diffractive optical element; and

[0010] In the matched state, the effective refractive index of the liquid crystal cell matches the refractive index of the diffractive optical element, so that the diffractive optical element does not contribute to the focal power of the lens.

[0011] The diffractive optical element includes a plurality of diffractive glares, each of the plurality of diffractive glares defines a peak and a valley, and at least one of the plurality of diffractive glares has a peak and / or a valley with rounded corners.

[0012] According to a second aspect of the present disclosure, there is provided an electrically switchable contact lens comprising the above-mentioned liquid crystal unit.

[0013] According to a third aspect of the present disclosure, there is provided a method of manufacturing an electrically switchable contact lens assembly for correcting a user's vision, the method comprising:

[0014] providing first and second contact lens polymer elements, each having a respective anterior surface and posterior surface, the anterior surface of the first contact lens polymer element comprising a groove;

[0015] inserting a liquid crystal cell including a diffractive optical element into the groove, the liquid crystal cell being switchable between a mismatched state and a matched state; and

[0016] attaching the anterior surface of the first polymeric element to the posterior surface of the second polymeric element to form the contact lens assembly;

[0017] Wherein in an unmatched state, the effective refractive index of the liquid crystal is different from the refractive index of the diffractive optical element, and in a matched state, the effective refractive index of the liquid crystal matches the refractive index of the diffractive optical element, so that in the matched state, the diffractive optical element does not contribute to the focal length of the lens assembly.

[0018] Of course, it should be understood that features described with respect to one aspect of the present disclosure may be incorporated into other aspects of the present disclosure. For example, the method of the present disclosure may incorporate any features described with reference to the apparatus of the present disclosure, and vice versa. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Example embodiments will now be described, by way of example only, with reference to the accompanying schematic drawings.

[0020] Figure 1 is a schematic side-expanded cross-sectional view of an example of a liquid crystal cell according to the first aspect of the present disclosure.

[0021] Figure 2 is incorporated Figure 1 Schematic side-expanded cross-sectional view of an example of a contact lens with a liquid crystal cell.

[0022] Figure 3A is a schematic representation of the local alignment of liquid crystal molecules in a liquid crystal cell in a mismatched state.

[0023] Figure 3B is a schematic representation of the local alignment of the liquid crystal molecules in a liquid crystal cell in a matched state.

[0024] Figure 4A and 4B Graphs of diffraction efficiency and wavelength in the near field and far field of a powered diffraction element with a diffraction height of 3.33 μm, respectively.

[0025] Figure 5A and 5B Graphs of diffraction efficiency and wavelength in the near field and far field of a powered diffraction element with a diffraction height of 3.76 μm, respectively.

[0026] Fig. 6A and 6B Graphs of diffraction efficiency and wavelength in the near field and far field of a powered diffraction element with a diffraction height of 4.19 μm, respectively.

[0027] Figure 7 is formed Figure 1 An illustrative diagram of the diffraction glare of a portion of a liquid crystal cell.

[0028] Figure 8 is a schematic plan view of the alignment of a liquid crystal director adjacent to an alignment polymer.

[0029] Figures 9A to 9F A series of side and cross-sectional views are shown illustrating steps in a method of making a contact lens according to another aspect of the present application.

[0030] Fig.10 yes Figures 9A to 9F Flowchart of the method steps shown in . DETAILED DESCRIPTION

[0031] According to a first aspect, the present disclosure provides an electrically switchable liquid crystal cell for changing the focal power of a contact lens, the liquid crystal cell comprising a diffractive optical element switchable between an unmatched state and a matched state. In the unmatched state, the effective refractive index of the liquid crystal cell is different from the refractive index of the diffractive optical element. In the matched state, the effective refractive index of the liquid crystal cell matches the refractive index of the diffractive optical element, so that the diffractive optical element does not contribute to the focal power of the lens. The diffractive optical element comprises a plurality of diffractive glares, each of the plurality of diffractive glares defining peaks and valleys, at least one of the plurality of diffractive glares having peaks and / or valleys having rounded corners.

[0032] The liquid crystal cell may be powered off in the unmatched state and powered on in the matched state. Alternatively, the liquid crystal cell may be powered on in the unmatched state and powered off in the matched state.

[0033] For example, when no current is applied to the liquid crystal cell, the liquid crystal may be arranged so as to present an effective refractive index that does not match the refractive index of the diffractive optical element. The incident light undergoes diffraction by the diffractive optical element and thus provides a boost to the focal power of the lens. When current is applied to the liquid crystal cell, the liquid crystal presents an effective refractive index that matches the refractive index of the diffractive optical element, so that the incident light is not diffracted and the focal power of the lens is not boosted.

[0034] Alternatively, when no current is applied to the liquid crystal cell, the liquid crystal may be arranged so as to present an effective refractive index that matches the refractive index of the diffractive optical element, so that incident light is not diffracted and the focal power of the lens is not contributed. When current is applied to the liquid crystal cell, the liquid crystal presents an effective refractive index that does not match the refractive index of the diffractive optical element, so that incident light is diffracted by the diffractive optical element and a contribution to the focal power of the lens is provided.

[0035] The liquid crystal cell may be arranged, in use, to be selectively powered by a power supply and optoelectronic circuitry within the contact lens.

[0036] Furthermore, applicants have discovered that providing a series of diffraction glares defining peaks and valleys with rounded corners and optionally non-vertical edges reduces the effects of image interference due to light scattering, and improves the alignment characteristics of the liquid crystal when switched on (powered), while still providing adequate diffraction efficiency for the lens, compared to standard diffraction designs with sharp diffraction glare (which maximize diffraction efficiency).

[0037] For each of the plurality of diffractive glares within the diffractive optical element, the radii of curvature of the rounded corners of the peaks and valleys may be the same, or may be different.

[0038] The radius of curvature of the rounded corners of the peaks and valleys may be between 0.1 μm and 50 μm.

[0039] More specifically, the radius of curvature at the rounded corners of the valleys of at least one or more (or all) of the plurality of diffraction glares may be between 5 μm and 50 μm.

[0040] It has been determined that for diffraction glare defined by upper (peak) and lower (valley) angles and the edges between the peak and valley angles, the curvature of the valley angles helps reduce the effects of image interference due to light scattering and also helps with crystal alignment, but with minimal loss of diffraction efficiency of the lens.

[0041] Similarly, the radius of curvature at the peak of one or more (or all) of the plurality of diffraction glares may be between 0.1 μm and 20 μm.

[0042] It has also been determined that providing peaks with rounded corners and providing non-perpendicular edges between peak and valley corners substantially reduces the effects of image interference due to light scattering with minimal loss of diffraction efficiency of the lens.

[0043] The non-perpendicular edges between peak and valley angles can be between nearly horizontal (1°) and nearly vertical (89°), and are constrained only by the physical geometry of the diffractive optical element.

[0044] The plurality of diffraction glares may have an average height (between the peak and the valley of each diffraction glare) between 2.5 μm and 3.8 μm. Alternatively, the plurality of diffraction glares may have an average height between 3.7 μm and 3.8 μm.

[0045] The height between the peaks and valleys of each diffractive flare may be substantially uniform, and may also be the height of the diffractive optical element along the optical axis. This may also be between 2.5 μm and 3.8 μm, or alternatively between 3.7 μm and 3.8 μm.

[0046] In the context of the present application, a diffractive optical element is one in which the size and scale of the diffraction glare is sufficiently small relative to the wavelength of the light incident thereon so as to cause a controlled and desired optical effect produced solely by the diffraction of the light. For the avoidance of doubt, a diffractive optical element does not include a Fresnel lens, which relies on the optical effect of refraction rather than diffraction for focusing.

[0047] In this context, the effective refractive index is the refractive index of the liquid crystal for light incident normally on the contact lens and the liquid crystal cell. The refractive index is 'effective' because it is the average of the ordinary and extraordinary refractive indices in the cholesteric liquid crystal.

[0048] In the matched state, the effective refractive index of the liquid crystal matches the refractive index of the diffractive optical element, and thus the diffractive optical element does not diffract incident light.

[0049] In this matching state, the difference between the effective refractive index of the liquid crystal and the refractive index of the diffractive optical element at a wavelength of 450 nm may be no more than 0.03, optionally no more than 0.02, and optionally no more than 0.01.

[0050] The difference between the effective refractive index of the liquid crystal and the refractive index of the diffractive optical element at a wavelength of 700 nm may be no more than 0.03, optionally no more than 0.02, and optionally no more than 0.01.

[0051] The difference between the effective refractive index of the liquid crystal and the refractive index of the diffractive optical element in the visible light part of the electromagnetic spectrum (wavelength between 450nm and 700nm) may not exceed 0.03, optionally not exceed 0.02, and optionally not exceed 0.01. Optionally, such a difference can be calculated at multiple wavelengths from 450nm to 700nm.

[0052] In the mismatched state, the effective refractive index of the liquid crystal and the refractive index of the diffractive optical element do not match, and thus the diffractive optical element diffracts incident light.

[0053] In this mismatched state, at both 450nm and 700nm, the effective refractive index of the liquid crystal may be 0.80 to 1.20 times the refractive index of the diffractive optical element. At both 450nm and 700nm, the effective refractive index of the liquid crystal may be 0.90 to 1.10 times the refractive index of the diffractive optical element. At both 450nm and 700nm, the effective refractive index of the liquid crystal may be 0.95 to 1.05 times the refractive index of the diffractive optical element. At both 450nm and 700nm, the effective refractive index of the liquid crystal may be 0.97 to 1.03 times the refractive index of the diffractive optical element. At both 450nm and 700nm, the effective refractive index of the liquid crystal may be 0.98 to 1.02 times the refractive index of the diffractive optical element.

[0054] The liquid crystal may comprise a cholesteric liquid crystal.Using cholesteric liquid crystal (as opposed to pure nematic or other liquid crystals) in a switchable contact lens allows for arrangements with only one liquid crystal cell, as no second liquid crystal cell is required to account for polarising effects.

[0055] In the unmatched state, the director of the liquid crystal away from the first and second inner surfaces (and optionally midway between the first and second inner surfaces) may optionally be at an angle of no more than 20 degrees, optionally no more than 15 degrees, optionally no more than 10 degrees, optionally no more than 8 degrees, optionally no more than 5 degrees, and optionally no more than 3 degrees to the first and second inner surfaces. In the on (powered) state, the director of the liquid crystal away from the first and second inner surfaces (and optionally midway between the first and second inner surfaces) may optionally be at an angle of at least 60 degrees, optionally at least 70 degrees, optionally at least 80 degrees, and optionally at least 85 degrees to the first and second inner surfaces.

[0056] Applicants have found that it is advantageous for the average effective refractive index of the liquid crystal to be similar to the refractive index of the diffractive optical element in the visible part of the electromagnetic spectrum.

[0057] The average effective refractive index of the liquid crystal and the refractive index of the diffractive optical element may be determined at 37° C. (a temperature approximately corresponding to human body temperature).

[0058] The applicant has found that it is advantageous to use a diffractive optical element having a characteristic operating wavelength that is lower than the characteristic operating wavelength that is typically available for other lenses, such as lenses for spectacles.

[0059] Contact lenses may incorporate liquid crystal cells as described above.

[0060] The contact lens includes a lens body for correcting the user's vision. The lens body provides an optical power, which may be a positive power (e.g., +0.5, +1.0, or +1.5D) or a negative power (e.g., -0.5, -3.0, or -4.0D, or a flat (0D)). The optical power of the lens body may be fixed. The contact lens may have a first optical power in an unmatched state and a second optical power in a matched state, so that the vision may be corrected for any two of the user's near, far, and / or intermediate vision.

[0061] In the context of the present application, "for correcting the vision of a user" means being suitable for correcting the near, far and / or intermediate vision of a user.

[0062] The contact lens body can be composed of a polymer material. For example, a polymerizable silicone elastomer can be used.

[0063] In the unpowered state, the liquid crystal cells may be unmatched and contribute negative power to the lens, so that the resulting power of the lens is less positive than in the powered state. In the powered state, the liquid crystal cells may then be matched and contribute no power to the lens, so that only the optical power of the body of the lens contributes to vision correction in this state.

[0064] In this way, the lens has a 'fail-safe' arrangement; if power to the liquid crystal cell is interrupted or fails, the lens is at a 'far' focal length, where the lens power is reduced by the negative power provided by the unmatched liquid crystal cell. In the powered state, the liquid crystal contributes no power to the lens, so the lens power remains unchanged, resulting in a 'near' focal length.

[0065] Similarly, in the unpowered state, the liquid crystal cells may be matched and not contributing power to the lens. In the powered state, the liquid crystals are then unmatched and arranged to add positive power to the lens so that the resulting power of the lens is more positive than in the matched state.

[0066] In this way, the lens has a 'fail-safe' arrangement; if power to the liquid crystal cell is interrupted or fails, the lens defaults to a 'far' focal length, where the focal power of the lens body is not altered by the liquid crystal cell. In the powered state, the liquid crystal promotes positive power to the lens, resulting in a 'near' focal length.

[0067] This 'fail safe' arrangement is important to the user as any power failure within the lens should enable the user to see objects in the far field. Reading glasses can be used as a substitute for the near field state of a switchable contact lens, even if the contact lens is still worn on the user. If this 'fail safe' is not provided, the powered state will be the 'far' focal length, and a power failure within the lens will cause the contact lens to default to 'near', which can be problematic until the user is able to remove the contact lens.

[0068] According to another aspect of the present disclosure, the present disclosure further provides a method for manufacturing an electrically switchable contact lens assembly for correcting a user's vision. The method includes providing a first and a second contact lens polymer element, each having a corresponding front surface and a rear surface, the front surface of the first contact lens polymer element including a groove. A liquid crystal cell is then inserted into the groove. The liquid crystal cell includes a diffractive optical element and can be switched between an unmatched state and a matched state. The front surface of the first polymer element is attached to the rear surface of the second polymer element to form a contact lens assembly. In the unmatched state, the effective refractive index of the liquid crystal is different from the refractive index of the diffractive optical element, and in the matched state, the effective refractive index of the liquid crystal matches the refractive index of the diffractive optical element. In this way, when in the matched state, the diffractive optical element does not contribute to the focal length of the lens assembly.

[0069] The method can further include lathing a first shape including a groove on an anterior surface of the first contact lens polymer element, and lathing a second shape on a posterior surface of the second contact lens polymer element. The second shape can match the first shape.

[0070] As such, both shapes allow for a groove to exist within the body of the lens assembly.

[0071] The method may further include the step of lathing the front surface of the contact lens assembly after attaching the first and second polymers.

[0072] This turning step may cut material from the front surface of the second polymer element of the assembly and, additionally, if the geometry permits, it may also cut material from the front surface of the first polymer element.

[0073] The step of inserting the liquid crystal cell into the recess may further include inserting an optoelectronic power and control element into the recess for selectively powering the liquid crystal cell.

[0074] It should be appreciated that such optoelectronic power and control elements provide selective power to the liquid crystal cells via terminals that are electrically coupled to electrodes of the liquid crystal cells.

[0075] Now we will only refer to the examples Figures 1 to 8 Exemplary embodiments of the present disclosure are described.

[0076] Figure 1 An example of an electrically switchable liquid crystal cell 10 according to an embodiment of the first aspect of the present disclosure is shown. The liquid crystal cell 10 is made of a substrate 18 in which a diffractive optical element is formed, the diffractive optical element comprising a plurality of diffractive glares 12. Each diffractive glare 12 is disposed between a front inner surface 16 and a rear inner surface 17 of the liquid crystal cell 10. For clarity, only the diffractive glares 12 on the left side of the figure are marked. Each diffractive glare 12 has an upper corner or peak 20 in contact with the front inner surface 16, and a lower corner or valley 30 in contact with the rear inner surface 17. An edge 25 of each diffractive glare 12 extends between each peak 20 and each valley 30.

[0077] It should be understood that Figure 1 2 is a side-expanded cross-sectional view, and when viewed from above, the diffraction glare 12 is annular, and its corresponding upper corner 20 and lower corner 30 are respectively annular ridges.

[0078] The lower half of each diffraction glare 12 is filled with a liquid crystal material 14, which is a cholesterol liquid crystal, including a nematic liquid crystal that has been doped with a chiral dopant. Such nematic liquid crystals are well known to those skilled in the art (liquid crystal science) and may include, for example, E7, BL037 and / or BL038. Such chiral dopants are also well known to those skilled in the art of liquid crystal science (e.g., Merck ZLI-3786, CB15, and S811).

[0079] The upper portion of each diffraction glare 12 includes a substrate 18 .

[0080] The height 35 of the diffractive optical element is the height between the front inner surface 16 and the rear inner surface 17. This is also the height between the peak 20 and the valley 30 of each diffractive glare 12.

[0081] The liquid crystal cell 10 also includes electrodes (not shown) for receiving a voltage, which will be further described below with respect to electrical switching of the liquid crystal cell 10 between unpowered and powered states.

[0082] Figure 2 is a schematic cross-sectional view of a contact lens 50 comprising a lens body 55 comprising any suitable contact lens material having incorporated therein Figure 1 The liquid crystal unit 10. The optoelectronic component 15 associated with the liquid crystal unit 10 is also incorporated into the lens body 55, and the optoelectronic component 15 may include power and control elements. The optoelectronic component 15 is coupled via an electrical coupler 19 to selectively provide power to the liquid crystal unit 10.

[0083] The liquid crystal cell 10 for correcting the vision of a user is provided in the following manner: In brief, the liquid crystal cell 10 can be switched between a first non-matching state and a second matching state. In the matching state, the effective refractive index of the liquid crystal matches the refractive index of the diffractive optical element, and the diffractive optical element has a first focal power. In the non-matching state, the effective refractive index of the liquid crystal does not match the refractive index of the diffractive optical element, and the diffractive optical element has a second focal power different from the first focal power.

[0084] The effective refractive index of the liquid crystal material 14 depends on the molecular orientation of the liquid crystal material 14. Figure 3A The local alignment of the molecules in the liquid crystal cell 10 in the unpowered state is schematically shown in FIG. Between the front inner surface 16 and the rear inner surface 17, the directors of the liquid crystal material 14 form a helical structure, which will be described further below. The rod shape 60 indicates that the directors of the liquid crystal are generally parallel to the front inner surface 16 and the rear inner surface 17 and are in the plane of the figure. In this unpowered state, the effective refractive index of the liquid crystal is independent of polarization and is determined by n ave =0.5(n e +n o ) is given, where n e is the extraordinary refractive index, and n o Those skilled in the art will recognize that it is desirable for the pitch of the liquid crystal to be no greater than 500 nm (ie, approximately equal to or less than the wavelength of the incident light) so that the liquid crystal behaves, to a reasonable approximation, as a single index material.

[0085] When a suitable voltage is applied to the liquid crystal cell 10 via the optoelectronic component 15 and the electrical coupler 19, the molecules of the liquid crystal material 14 switch to Figure 3B The in-line state is schematically shown, with rod shapes 70 indicating that the directors of the liquid crystal material 14 are perpendicular to the front inner surface 16 and the rear inner surface 17. This realignment of the liquid crystal material 14 provides a different effective refractive index. In this second switched (powered) state, the effective refractive index may be n o .

[0086] When the liquid crystal material 14 is in a powered state, the effective refractive index of the liquid crystal material 14 matches the refractive index of the substrate 18, in which case the diffractive optical element does not contribute to the focal power of the lens. Conversely, when the liquid crystal material 14 is in an unpowered state, the effective refractive index of the liquid crystal material 14 does not match the refractive index of the substrate 18, and therefore the diffractive optical element contributes to the focal power of the lens.

[0087] Consider now the contact lens 50 in which the liquid crystal cell 10 is mounted, the lens body 55 may have positive power, and the selectively applied diffractive power of the liquid crystal cell 10 may be negative power. When the power to the liquid crystal cell 10 is turned off, the negative optical power of the diffractive optical element is combined with the positive lens power of the lens body 55 to provide a synthetic optical power that is not as positive as the lens power of the lens body 55 alone, and which is suitable for farsightedness.

[0088] In contrast, when power to the diffractive element is turned on (supplied by optoelectronic assembly 15 and electrical coupler 19), the effective refractive index of liquid crystal cell 10 matches the refractive index of substrate 18, and liquid crystal cell 10 does not contribute to optical diffraction power. In this state, the optical power of contact lens 50 is only the positive lens power of lens body 55, which is the power required for myopia.

[0089] For example, the lens body 55 may have a power of +2D, and the power of the diffractive element when visible may be -2D. Thus, the optical power of the contact lens may be switched between 0D (when off, diffraction works) and +2D (when on, diffraction does not work).

[0090] exist Figure 8 80, wherein arrow 85 indicates the direction of the director of the liquid crystal material 14 adjacent to the alignment polymer. This alignment is used to provide polarization-independent operation of the contact lens 50.

[0091] Reference now Figures 4A to 6B Optical modeling describing different diffraction heights showing a graph of diffraction efficiency (%) for different diffraction orders as a function of wavelength (nm). The diffraction efficiency of a given order is the ratio of the optical power propagating away from the diffraction element to the optical power incident on the diffraction element.

[0092] The substrate 18 is selected to have a low diffraction index, such as polymethylmethacrylate (PMMA) lens material.

[0093] The liquid crystal material 14 may be a mixture of BL037 and BL038 materials and a 50 / 50 mixture has been found to produce very good index matching for near field performance without any undesirable shift in far field performance (100% BL037 has been found to produce a slight shift towards red in the far field).

[0094] Figure 4Ais a graph of the near-field efficiency of a diffractive element with a height of 3.33 μm. The liquid crystal cell 10 is in a matched state, wherein the effective refractive index of the liquid crystal and the diffractive optical element is substantially the same, i.e. matched, and therefore the diffractive optical element is inactive. The intensity of the various order diffraction profiles is observed from the diffractive optical element. It can be seen that the intensity of the profile observed from the diffractive optical element is small at all wavelengths. The first curve 110 of the graph shows the first order diffraction as a function of wavelength, and the second curve 115 shows the second order diffraction as a function of wavelength. Figure 4A The first and second order diffraction profiles in are shown as multiplied by 100. As can be seen from the figure, the residual first order light at 450nm is about 0.05%, and the residual second order light at that wavelength is closer to 0.01%. The total diffraction efficiency (given by line 120) is about 50%. The 0th order (i.e. directly incident) light is greater than 99%, as shown by the dotted line 125.

[0095] Figure 4B A graph showing the diffraction efficiency of a diffractive element with a height of 3.33 μm in the far field. This occurs when the liquid crystal cell 10 is in an unpowered state, which causes the diffractive optical element to be visible and promotes the focal length of the lens 50. This can be considered to be a hyperopic state. In the event of a power failure, the contact lens defaults to this hyperopic state, in which the optical focal length of the lens 50 does not promote the diffractive element. Curve 130 shows a primary peak, which represents most of the light seen by the user. Its peak is at 450nm, and the tail is at higher wavelengths. Curve 140 shows the 0th order (i.e. direct light), in which case the 0th order should be as small as possible, but has a valley at 450nm and a slightly higher level at higher wavelengths, which introduces some blue shifts. Curve 145 shows secondary light.

[0096] Figure 5A Shows something like Figure 5A The near-field diffraction efficiency of FIG. 1 is shown in FIG. 1 , but the height of the diffraction element is 3.76 μm. Similarly, the liquid crystal cell 10 is in a matching state, wherein the effective refractive index of the liquid crystal and the diffractive optical element is substantially the same, ie, matched. Figure 5A The first and second order diffraction profiles shown in are shown multiplied by 100. As can be seen from curve 210, the residual first order light at 450nm is about 0.1%. Another curve 215 shows the second order diffraction. The total diffraction efficiency (given by line 220) is about 55%. Finally, the 0th order (i.e. directly incident) light is greater than 99%, as shown by line 225.

[0097] Figure 5B Shows something like Figure 5B2 shows a graph of the far field diffraction efficiency of the diffraction element 10 with a diffraction element height of 3.76 μm. When the liquid crystal cell 10 is in the second inactive state, the far-view state, the far field appears again. Curve 230 shows that the primary peak now occurs at about 525 nm, with an acceptable performance level over the visible spectrum. Similarly, curve 240 shows the 0th order valley between 500 and 550 nm. Curve 245 shows the secondary light.

[0098] Fig. 6A Shows something like Figure 5A and 6A The near-field diffraction efficiency of FIG. 1 is shown in FIG. 2 , but the height of the diffractive element is 4.19 μm. Similarly, the liquid crystal cell 10 is in a matched state, wherein the effective refractive index of the liquid crystal material 14 and the substrate 18 of the diffractive optical element is substantially the same, ie, matched. Fig. 6A The first and second order diffraction profiles shown in are shown multiplied by 100. As can be seen from curve 260, the residual first order light at 450nm is about 0.1%. Another curve 265 shows the second order diffraction. The total diffraction efficiency (given by line 270) is about 55%. Finally, the 0th order (i.e. directly incident) light is greater than 99%, as shown by line 275.

[0099] Figure 6B Shows something like Figure 5B and 6B 1 , the diffraction element height is 4.19 μm. When the liquid crystal unit 10 is in the second inactive state, ie, the far-view state, the far field appears again.

[0100] Curve 280 shows that the 0th and primary peaks now occur at about 500 nm, and curve 290 shows that the 0th order valley is between 550 and 600 nm. This indicates a slight red shift. Curve 295 shows the secondary light.

[0101] It can therefore be seen that the diffraction height primarily affects the far field performance; at a diffraction height of 3.33 μm, the envelope is shifted to the left (revealing some effects at the blue end of the spectrum), and at a diffraction height of 4.19 μm, the envelope is shifted in the opposite direction to the right (revealing some effects at the red end of the spectrum). In view of these results, in this example, the preferred diffraction height has been determined to be approximately 3.76 μm.

[0102] Now also refer to Figure 7 , a cross-sectional close-up representation of a side view of a liquid crystal cell 10 showing a diffraction glare 12. It will be appreciated that when viewed from above, the glare 12 has a ring-shaped form. Figure 1 It can be observed that to form a diffractive optical element, a plurality of diffractive glares 12 are required. There may be 16 diffractive glares, or more or less than 16 diffractive glares. The number of glares may be proportional to the square of the diameter of the optical zone of the contact lens, and linearly proportional to the optical power provided by the diffractive optical element.

[0103] A standard diffractive glare shape for optimal diffraction efficiency is illustrated by the dashed line, which includes both upper and lower corners 20 and 30 of substantially 90 degrees, and a vertical edge 25 between the upper and lower corners 20 and 30. The height 35 of the diffractive optical element substantially corresponds to the length of the vertical edge 25 (i.e., the vertical spacing between the upper and lower corners 20 and 30).

[0104] Applicants have surprisingly found that by replacing one or both of the upper corners 20 and lower corners 30, respectively, with curves of appropriate length, scattering and liquid crystal alignment problems are reduced with an acceptable compromise in terms of diffraction efficiency.

[0105] In this example, the lower corner 30 is replaced by a lower curve 21 having a radius r1 (line 23) and terminating in a valley 28. The upper corner 20 is replaced by an upper curve 22 having a radius r2 (line 24) and terminating in a peak 27. The height 35 of the diffractive optical element is now defined by the vertical spacing between the peak 27 of the upper curve 22 and the valley 28 of the lower curve 21. The vertical edge 25 is now replaced by an edge 26, which extends between the lower curve 21 and the upper curve 22. (If the lower curve 21 and the upper curve 22 are in contact with each other, the edge 26 between the lower curve 21 and the upper curve 22 can be completely omitted).

[0106] In addition, the lower curve 21 and the upper curve 22 can produce an arc that subtends a central angle of less than 90 degrees. Alternative arrangements of 45 degrees, 60 degrees or other intermediate subtending angles are possible. In these cases, the edge 26 can be angled away from the vertical direction.

[0107] Surprisingly, it has been found that for a diffraction height 35 of approximately 3.76 μm, replacing the lower corner 30 of each glare 12 with a lower curve 21 having a radius of curvature r1 (line 23) between 5 μm and 50 μm, and replacing the upper corner 20 of each glare 12 with an upper curve 22 having a radius of curvature r2 (line 24) between 0.1 μm and 20 μm provides an acceptable level of optical performance of the diffraction element of the liquid crystal cell 10 while ensuring good switching characteristics of the liquid crystal material 14.

[0108] The exemplary contact lenses described above provide unexpectedly good peripheral imaging performance. It is expected that light is incident on the diffractive optical element from a wide range of angles, and this wide variation in the angle of incidence and corneal curvature can result in large variations in the optical path length through the diffractive optical element, resulting in poor optical performance. However, applicants have discovered that peripheral light entering the contact lens and passing through the pupil passes through a portion of the diffractive optical element that is approximately perpendicular to the incident light, i.e., the light comes from approximately the same direction, and the angle of incidence varies very little. This results in good peripheral imaging performance.

[0109] In addition, as the incident angle of the light increases from vertical, the amount of light passing through the diffractive optical element decreases. At a certain angle, essentially no light passes through the diffractive optical element and no optical artifacts are seen. For example, for light with an incidence of about 53° and a pupil size of 5 mm, approximately half of the detected light beam is incident on the diffractive optical element and the other half passes through the non-diffractive area of ​​the contact lens. For light at higher incident angles, the effective area of ​​the diffractive optical element exposed to the light is further reduced, so that when the light beam moves completely out of the diffractive area, the optical artifacts become negligible. Therefore, as far as the user's attention is concerned, there is no abrupt start / stop of the diffractive area, only a smoothly varying boost amplitude. In contrast to the eyeglass lens embodiment, a sharp jump can be observed when switching between viewing through the diffractive optical element and not viewing through the diffractive optical element.

[0110] Applicants have also found that the astigmatism of peripheral light caused by incident light passing through the diffractive optical element at non-perpendicular angles is acceptable (about 0.3D on average).

[0111] Now also refer to Figures 9A to 9F and 10, showing a method of manufacturing a contact lens. Fig.9A In the present invention, a first water-free polymer blank 300 is provided. The method starts by forming a cutout 320 in a rear surface 310 of the first polymer blank 300 by a turning tool ( Fig.10 The turning tool used is usually a digital turning tool using industrial diamonds.

[0112] like Fig. 9B As shown, the corresponding cut surface 335 of the first polymer blank 300 is then securely mounted on the fixture 330 (block 410 ) with the wax 340 applied along the cut surface 335 .

[0113] Then, if Fig. 9C As shown, a turning tool is used to remove material 350 (block 420 ) from the front surface 345 of the first polymer blank 300 in order to engrave a stepped shape therein, which includes a groove 360 ​​.

[0114] After this, if Fig.9D As shown, the second polymer blank 370 is subjected to a cutting process in which a turning tool removes material 375 from the rear surface of the polymer blank 370 (block 430 ) to create another stepped shape in addition to the grooves 360 that generally coordinates with the stepped shape of the front surface of the first polymer blank 300 .

[0115] The optoelectronic package 380 is inserted into the recess 360 of the first polymer blank 300 (block 440). The optoelectronic package 380 includes the liquid crystal cell 10 and the optoelectronic component 15, which includes power and control elements as described above.

[0116] Glue is then applied between the first polymer blank 300 and the second polymer blank 370 and both are attached within the recess 360 with the optoelectronic package 380 sandwiched therebetween (block 450 ).

[0117] The front surface 385 of the second polymer blank 370 is then cut away using a turning tool (block 460) to form a Fig.9E The lens assembly 390 shown includes a formed lens element 395 glued to the first polymer blank 300, which is still mounted on the fixture 330 ( Fig.9E Not shown, this is a side view).

[0118] Finally, if Fig.9F As shown, the lens assembly 390 is removed from the fixture (block 470) by dissolving the wax 340. The optoelectronic package 380 is shown in this cross-sectional view.

[0119] If desired, prior to soaking in an extraction and / or hydration solution to hydrate the lens assembly 400, one or both sides of the lens assembly 400 may be polished to remove any edges.

[0120] Although the present disclosure has been described and illustrated with reference to specific embodiments, those skilled in the art will appreciate that the present disclosure lends itself to many different variations not specifically described herein. By way of example only, certain possible variations will now be described.

[0121] The use of the diffractive optical element is not limited to the liquid crystal cell including the cholesteric liquid crystal. For example, other types of liquid crystal including undoped nematic and smectic liquid crystals may be used.

[0122] The arrangement of the step shapes cut into the first and second polymer blanks may be different than that shown in the drawings, and the shape and configuration of the grooves may also be different.

[0123] Furthermore, the turning process described above may be replaced with an alternative contact lens manufacturing process such as molding.

[0124] The arrangement of the diffractive elements (including the number of diffractive glares) and their dimensions (eg, glare height and the radius of curvature of the peaks and valleys) may be different from those described above.

[0125] Furthermore, in contrast to the above arrangement, it should be appreciated that the liquid crystal cells may be arranged to be unmatched in a powered state and matched in an unpowered state. In this arrangement, in the unpowered state, the liquid crystal cells provide no positive power to the lens, and in the powered state, the liquid crystal cells provide positive power to the lens.

[0126] In the foregoing description, if reference is made to an integral body or element with a known, obvious or foreseeable equivalent, such equivalents are incorporated herein as if individually stated. Reference should be made to the claims to determine the true scope of the present disclosure, which should be interpreted as covering any such equivalents. The reader will also appreciate that the integral bodies or features of the present disclosure described as preferred, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. In addition, it should be understood that such optional integral bodies or features, while potentially beneficial in some embodiments of the present disclosure, may not be ideal in other embodiments and therefore may not exist.

Claims

1. An electrically switchable liquid crystal cell for changing the focal power of a contact lens, the liquid crystal cell comprising a diffractive optical element switchable between an unmatched state and a matched state, in: In the mismatched state, the effective refractive index of the liquid crystal cell is different from the refractive index of the diffractive optical element; and In the matched state, the effective refractive index of the liquid crystal cell matches the refractive index of the diffractive optical element such that the diffractive optical element does not contribute to the power of the lens, and The diffractive optical element includes a plurality of diffractive glares, each of the plurality of diffractive glares defines a peak and a valley, and at least one of the plurality of diffractive glares has a peak and / or a valley with rounded corners. 2 . The liquid crystal cell of claim 1 , wherein at least one of the plurality of diffraction glares has a valley with rounded corners having a radius of curvature between 5 μm and 50 μm.

3. The liquid crystal cell of claim 1 or claim 2, wherein each of the plurality of diffraction glares has a valley with rounded corners having a radius of curvature between 5 μm and 50 μm.

4. A liquid crystal cell according to any preceding claim, wherein at least one of the plurality of diffraction glares has a peak with rounded corners having a radius of curvature between 0.1 μm and 20 μm.

5. A liquid crystal cell according to any preceding claim, wherein each of the plurality of diffraction glares has a peak with rounded corners having a radius of curvature between 0.1 μm and 20 μm.

6. A liquid crystal cell according to any preceding claim, wherein the plurality of diffraction glares have an average height of between 2.5 μm and 3.8 μm. 7 . The liquid crystal cell according to claim 6 , wherein the plurality of diffraction glares have an average height between 3.7 μm and 3.8 μm.

8. A liquid crystal cell according to any preceding claim, wherein the liquid crystal cell comprises cholesteric liquid crystals.

9. An electrically switchable contact lens for correcting the vision of a user, comprising a liquid crystal cell as claimed in any preceding claim.

10. The contact lens of claim 9, wherein the contact lens comprises a polymer lens body.

11. A contact lens according to claim 9 or claim 10, wherein in the unmatched state, the liquid crystal cell contributes negative power to the lens so that in the unmatched state, the resultant power of the lens is less positive than in the matched state.

12. A method of manufacturing an electrically switchable contact lens assembly for correcting a user's vision, the method include: providing first and second contact lens polymer elements, each having a respective anterior surface and posterior surface, the anterior surface of the first contact lens polymer element comprising a groove; inserting a liquid crystal cell including a diffractive optical element into the groove, wherein the liquid crystal cell is switchable between a mismatched state and a matched state; and attaching the anterior surface of the first polymeric element to the posterior surface of the second polymeric element to form the contact lens assembly; Wherein in the unmatched state, the effective refractive index of the liquid crystal is different from the refractive index of the diffractive optical element, and in the matched state, the effective refractive index of the liquid crystal matches the refractive index of the diffractive optical element, so that in the matched state, the diffractive optical element does not contribute to the focal length of the lens assembly.

13. The method according to claim 12, further comprising: The following steps are involved: lathing a first shape at the front surface of the first contact lens polymer element, the shape comprising the groove; A second shape is machined at the back surface of the second contact lens polymer element, the second shape matching the first shape.

14. The method of claim 12 or claim 13, wherein the method further comprises, after the attaching step, lathing the front surface of the contact lens assembly.

15. The method of any one of claims 12 to 14, wherein the step of inserting a liquid crystal cell into the recess further comprises inserting an optoelectronic power and control element for selectively powering the liquid crystal cell.

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