Electrically switchable liquid crystal cell, contact lens, and related method

Abstract

An electrically switchable liquid crystal cell (10) is provided together with a lens (50) having this liquid crystal cell, and a method for manufacturing the liquid crystal cell. The liquid crystal cell (10) has a diffractive optical element (12) and a liquid crystal material (14) that can be switched between a mismatched (unswitched) state and a matched (switched) state. In the mismatched state, the effective refractive index of the liquid crystal material (14) is different from the effective 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) matches the effective refractive index of the substrate (18). In the matched state, the diffractive optical element does not contribute to the focal power of the lens. The diffractive optical element (12) has a number of peaks (20) and valleys (30) with rounded corners.

Description

Technical Field

[0001] The present disclosure relates to off - spectacle contact lenses. In particular, but not limited to, the present disclosure relates to electrically switchable off - spectacle contact lenses.

Background Art

[0002] Presbyopia is a condition in which the eye cannot focus on nearby objects due to the hardening of the lens inside the eye, and such presbyopia affects almost all people as they age. Reading glasses with a near - vision power of +1.0 to +3.0 diopters (in this specification, power (or diopter) and refractive power are used interchangeably) have provided solutions to this problem over the years, including bifocal or multifocal glasses, which have the additional advantage of being able to provide additional corrective power for other eye conditions, such as myopia. Thus, only one pair of glasses was needed to obtain both near - vision and far - vision.

[0003] Multifocal contact lenses are nothing more than a separate technical improvement for presbyopic patients. For example, multifocal contact lenses with a concentric ring pattern are known, where the central zone functions in either the myopic or the hyperopic direction, and the surrounding rings have alternating myopic and hyperopic prescriptions. These multifocal contact lenses have the disadvantages of poor image quality and not being suitable for all users.

[0004] Ophthalmic contact lenses are increasingly technologically advanced with the development of electronic components. For example, contact lenses with "tunable" diffractive optical elements have been fabricated using cholesteric liquid crystals (nematic liquid crystals doped with chiral dopants). Such liquid crystals are well known to those skilled in the art and may include, for example, E78 and BL037 and / or BL038. Chiral dopants are also well known to those skilled in liquid crystal science, and examples of such chiral dopants include Merck ZLI-3786, CB15 and S811.

[0005] The related lens circuit allows the contact lens incorporating such a tunable diffractive optical element to be electrically switchable between a diffractive state and a non-diffractive state, thus providing a multifocal contact lens with two alternately switchable optical refractive powers. [Overview of the project] [Problems that the invention aims to solve]

[0006] A known challenge with this configuration is the difficulty in achieving acceptable optical performance without generating undesirable light scattering originating from the diffractive optical element. Furthermore, these contact lenses are difficult to manufacture.

[0007] This disclosure aims to provide an improved liquid crystal cell and contact lens having a diffractive optical element. [Means for solving the problem]

[0008] According to a first aspect of this disclosure, an electrically switchable liquid crystal cell for changing the focal ability of a contact lens, wherein the liquid crystal cell has a diffractive optical element that can be switched between a mismatched state and a matched state, In a mismatched state, the effective refractive index of the liquid crystal cell differs from that of the diffractive optical element. In a matched state, the effective refractive index of the liquid crystal cell matches that of the diffractive optical element; therefore, the diffractive optical element does not contribute to the focal capability of the contact lens. A liquid crystal cell is provided, characterized in that the diffractive optical element has a plurality of diffractive blades, each of the plurality of diffractive blades has defined peaks and valleys, and at least one of the plurality of diffractive blades has peaks and / or valleys with rounded corners.

[0009] According to a second aspect of this disclosure, there is a contact lens provided that is electrically switchable for correcting a user's vision and is characterized by having the above-mentioned liquid crystal cell.

[0010] According to a third aspect of this disclosure, a method for manufacturing an electrically switchable contact lens assembly for correcting a user's vision, the method comprising: The process includes the step of preparing first and second polymer elements for contact lenses, each having its own front and rear surfaces, wherein the front surface of the first polymer element for contact lenses has a recess, The process includes inserting a liquid crystal cell containing a diffractive optical element into a recess, wherein the liquid crystal cell is switchable between a mismatched state and a matched state. The process includes the step of attaching the front surface of a first polymer element for a contact lens to the rear surface of a second polymer element to form a contact lens assembly. A method is provided characterized in that, in a mismatched state, the effective refractive index of the liquid crystal cell is different from that of the diffractive optical element, and in a matched state, the effective refractive index of the liquid crystal cell matches that of the diffractive optical element, and therefore, in a matched state, the diffractive optical element does not contribute to the focusing ability of the contact lens assembly.

[0011] Naturally, it will be recognized that features described in relation to one aspect of this disclosure can be incorporated into other aspects of this disclosure. For example, the methods of this disclosure can incorporate any of the features described in relation to the products of this disclosure, and vice versa.

[0012] Next, an exemplary embodiment will be described with reference to the attached drawings, but these are merely illustrative examples. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic side view of an embodiment of a liquid crystal cell according to the first aspect of this disclosure. [Figure 2] Figure 1 is a schematic side view of one embodiment of a contact lens having a liquid crystal cell. [Figure 3A] This is a schematic diagram of the local alignment of liquid crystal molecules in a misaligned liquid crystal cell. [Figure 3B] This is a schematic diagram of the local alignment of liquid crystal molecules in a liquid crystal cell in a matched state. [Figure 4A] These are plots (4A and 4B) showing the relationship between diffraction efficiency and wavelength at the near and far fields of view for a powered diffraction element with a diffraction height of 3.33 μm. [Figure 4B] This plot shows the relationship between diffraction efficiency and wavelength at the near and far fields of view for a powered diffraction element with a diffraction height of 3.33 μm. [Figure 5A] This plot shows the relationship between diffraction efficiency and wavelength at the near and far fields of view for a powered diffraction element with a diffraction height of 3.76 μm. [Figure 5B] This plot shows the relationship between diffraction efficiency and wavelength at the near and far fields of view for a powered diffraction element with a diffraction height of 3.76 μm. [Figure 6A] This plot shows the relationship between diffraction efficiency and wavelength at the near and far fields of view for a powered diffraction element with a diffraction height of 4.19 μm. [Figure 6B] A plot diagram showing the relationship between diffraction efficiency and wavelength in the near field and far field of a diffractive element with a diffracted height of 4.19 μm supplied with power. [Figure 7] An explanatory diagram of a diffraction grating that forms part of the liquid crystal cell of FIG. 1. [Figure 8] A schematic plan view of the alignment of the directors of the liquid crystal located adjacent to the alignment polymer. [Figures 9A-9F] FIGS. 9A to 9F are a series of side views and cross-sectional views showing the method steps for manufacturing a contact lens according to another aspect of the present application. [Figure 10] A flowchart of the method steps shown in FIGS. 9A to 9F.

Embodiments for Carrying Out the Invention

[0014] According to a first aspect, the present disclosure is an electrically switchable liquid crystal cell for changing the focusing power of a contact lens, the liquid crystal cell having a diffractive optical element that can be switched 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 effective refractive index of the diffractive optical element. In the matched state, the effective refractive index of the liquid crystal cell matches the effective refractive index of the diffractive optical element, and thus the diffractive optical element does not contribute to the focusing power of the contact lens. The diffractive optical element has a plurality of diffraction gratings, each of the plurality of diffraction gratings defining a peak and a valley, and at least one of the plurality of diffraction gratings has a peak and / or valley with a rounded corner.

[0015] The liquid crystal cell is preferably not supplied with power in the unmatched state and is preferably supplied with power in the matched state. As a modification, the liquid crystal cell is preferably supplied with power in the unmatched state and is preferably not supplied with power in the matched state.

[0016] For example, when no current flows through the liquid crystal cell, it is preferable that the liquid crystal cell be positioned to provide an effective refractive index that does not match the effective refractive index of the diffractive optical element. The incident light undergoes diffraction by the diffractive optical element, thus contributing to the focal power of the lens. When current flows through the liquid crystal cell, the liquid crystal cell provides an effective refractive index that matches the effective refractive index of the diffractive optical element, and therefore the incident light is not diffracted, and no contribution to the focal power of the lens occurs.

[0017] As a variation, when no current is passed through the liquid crystal cell, the liquid crystal may be arranged to provide an effective refractive index that matches the effective refractive index of the diffractive optical element, so that the incident light is not diffracted and does not contribute to the lens power. When current is passed through the liquid crystal cell, the liquid crystal cell provides an effective refractive index that does not match the effective refractive index of the diffractive optical element, so that the incident light is diffracted by the diffractive optical element and contributes to the lens's focal power.

[0018] The liquid crystal cell is preferably configured to be selectively powered by a power supply and optoelectronic circuit located within the contact lens during use.

[0019] Furthermore, in contrast to standard diffraction designs with steep diffraction blazes (which maximize diffraction efficiency), the applicant provides a series of diffraction blazes defining peaks and valleys with rounded corners, and optionally non-vertical edges, thereby reducing the impact of image interference caused by light scattering, improving the alignment characteristics of the liquid crystal cell when switched on (powered), while still providing sufficient diffraction efficiency for the lens.

[0020] The radius of curvature of the rounded corners of the peaks and valleys may be the same or different for each of the multiple diffraction blazes within the diffractive optical element.

[0021] The radius of curvature of the rounded corners in the peaks and valleys should preferably be between 0.1 μm and 50 μm.

[0022] More specifically, the radius of curvature at the rounded corners of one or more (or all) of the diffraction blazes should ideally be between 5 μm and 50 μm.

[0023] Regarding the diffraction blaze formed by the upper (peak) corner, the lower (valley) corner, and the edge between the peak and valley corners, it was confirmed that the curvature of the valley corner helps to reduce the impact of image interference caused by light scattering, and further assists in crystal alignment, while minimizing the loss of diffraction efficiency related to the lens.

[0024] Similarly, the radius of curvature at the peaks of one or more (or all) of the diffraction blazes should preferably be between 0.1 μm and 20 μm.

[0025] Furthermore, it was confirmed that by providing a peak section with rounded corners, and a non-vertical edge between the peak corner and the valley corner, the impact of image interference, primarily caused by light scattering, is reduced while minimizing the loss of diffraction efficiency related to the lens.

[0026] The non-vertical edge between the peak corner and the valley corner is preferably between near horizontal (1°) and near vertical (89°), and is also constrained only by the physical geometric shape of the diffractive optical element.

[0027] The multiple diffraction blazes preferably have an average height of 2.5 μm to 3.8 μm (the distance between the peaks and valleys of each diffraction blaze). As an alternative, the multiple diffraction blazes may have an average height of 3.7 μm to 3.8 μm.

[0028] The height between the peaks and valleys of each diffraction blaze is preferably substantially uniform and also preferably equal to the height of the diffractive optical element along the optical axis. This is also preferably 2.5 μm to 3.8 μm, or, as a variation, 3.7 μm to 3.8 μm.

[0029] In the context of this application, a diffractive optical element is an optical element such that the diffractive blaze is small enough in size and scale to produce a controlled and desired optical effect that arises solely from the diffraction of light, with respect to the wavelength of light incident upon it. To avoid misunderstanding, a diffractive optical element does not include a Fresnel lens that utilizes a refractive optical effect for focusing rather than diffraction.

[0030] In this context, the effective refractive index is the refractive index of the liquid crystal with respect to light incident perpendicularly on the contact lens and on the liquid crystal cell. The refractive index is "effective" in that it is the average of the ordinary and extraordinary refractive indices of the cholesteric liquid crystal cell.

[0031] In the matched state, the effective refractive index of the liquid crystal and the effective refractive index of the diffractive optical element are the same, and therefore the diffractive optical element does not diffract the incident light.

[0032] In this matching state, the difference between the effective refractive index of the liquid crystal and the effective refractive index of the diffractive optical element at a wavelength of 450 nm is likely to be 0.03 or less, optionally 0.02 or less, and optionally 0.01 or less.

[0033] The effective refractive index of liquid crystals and diffractive optical elements at a wavelength of 700 nm is likely to be 0.03 or less, optionally 0.02 or less, and optionally 0.01 or less.

[0034] The effective refractive index of liquid crystals and diffractive optical elements in the visible part of the electromagnetic spectrum (between wavelengths of 450 nm to 700 nm) is likely to be 0.03 or less, optionally 0.02 or less, and optionally 0.01 or less. Optionally, this difference should be calculated over multiple wavelengths between 450 nm and 700 nm.

[0035] In a mismatched state, the effective refractive index of the liquid crystal and the effective refractive index of the diffractive optical element do not match, and therefore, the diffractive optical element diffracts the incident light.

[0036] In this mismatched state, the effective refractive index of the liquid crystal is preferably 0.80 to 1.20 times the effective refractive index of the diffractive optical element at both 450 nm and 700 nm. The effective refractive index of the liquid crystal is preferably 0.90 to 1.10 times the effective refractive index of the diffractive optical element at both 450 nm and 700 nm. The effective refractive index of the liquid crystal is preferably 0.95 to 1.05 times the effective refractive index of the diffractive optical element at both 450 nm and 700 nm. The effective refractive index of the liquid crystal is preferably 0.97 to 1.03 times the effective refractive index of the diffractive optical element at both 450 nm and 700 nm. The effective refractive index of the liquid crystal is preferably 0.98 to 1.02 times the effective refractive index of the diffractive optical element at both 450 nm and 700 nm.

[0037] The liquid crystal should preferably consist of a cholesteric liquid crystal. By using a cholesteric liquid crystal cell in a switchable contact lens, a structure with only one liquid crystal cell is possible (in contrast to purely nematic liquid crystal cells and others), because a second liquid crystal cell is not needed to address the polarization effect.

[0038] In the mismatched state, the liquid crystal directors located far from the first and second inner surfaces (optionally, midway between the first and second inner surfaces) should preferably form angles with respect to the first and second inner surfaces of 20° or less, 15° or less, 10° or less, 8° or less, 5° or less, and 3° or less, as optional. In the switching (power supply) state, the liquid crystal directors located far from the first and second inner surfaces (optionally, midway between the first and second inner surfaces) should preferably form angles with respect to the first and second inner surfaces of 60°, 70° or less, 80° or less, and 85°, as optional.

[0039] The applicant has discovered that it is advantageous for the average effective refractive index of a liquid crystal to be approximately the same as the effective refractive index of a diffractive optical element in the visible portion of the electromagnetic spectrum.

[0040] The average effective refractive index of liquid crystals and the effective refractive index of diffractive optical elements should ideally be determined at 37°C (a temperature corresponding to the human body temperature).

[0041] The applicant has found that it is advantageous to use a diffractive optical element that has a natural operating wavelength lower than the natural operating wavelength typically used for other lenses, such as eyeglass lenses.

[0042] Contact lenses should ideally incorporate liquid crystal cells as described above.

[0043] A contact lens has a lens body for correcting the user's vision. The lens body provides an optical refractive power (power), which may be a positive refractive power such as +0.5D, +1.0D, or +1.5D, or a negative refractive power such as -0.5D, -3.0D, or 4.0D, or it may be plano (0D). The optical refractive power of the lens body may be fixed. The contact lens can provide a first optical refractive power in a mismatched state and a second optical refractive power in a matched state, so that the visual acuity can be corrected for any two of the user's near vision, distance vision, and / or intermediate vision.

[0044] In the context of this application, the phrase "for correcting the user's vision" means that it is suitable for correcting the user's near vision, distance vision, and / or intermediate vision.

[0045] The contact lens body should preferably be made of a polymer material. For example, polymerizable silicone elastomer can be used.

[0046] In the non-powered state, the liquid crystal cell is mismatched and its contribution to the lens is negative; therefore, the resulting focal power of the lens is smaller in positive values ​​than in the powered state. In the powered state, the liquid crystal cell is preferably in a matched state, its contribution to the lens is zero, and as a result, only the optical refractive power of the lens itself contributes to vision correction in this state.

[0047] Thus, the lens has a "fail-safe" structure; that is, if power to the liquid crystal cell is interrupted or lost, the lens defaults to a "far" focal length, in which case the lens focusing capability is reduced by the negative focusing capability provided by the mismatched liquid crystal cell. When power is supplied, the liquid crystal has zero focusing capability contributing to the lens, and therefore the lens focusing capability remains unchanged, thereby obtaining a "near" focal length.

[0048] Similarly, in the non-powered state, the liquid crystal cell is preferably in a matched state and has zero focal power contributing to the lens. In the powered state, the liquid crystal cell is preferably in a mismatched state and has positive focal power contributing to the lens; therefore, the resulting focal power of the lens is a larger positive value than in the matched state.

[0049] Thus, the lens has a "fail-safe" structure; that is, if power to the liquid crystal cell is interrupted or lost, the lens defaults to a "far" focal length, in which case the focusing capability of the lens body is not replaced by that of the liquid crystal cell. When power is supplied, the liquid crystal contributes positive focusing capability to the lens, thereby obtaining a "near" focal length.

[0050] Such a fail-safe structure is important for the user because, even if there is a loss of power within the lens, the user must remain able to see objects at a distance. Reading glasses can be used as an alternative to the near-vision state of a switchable contact lens, even if the contact lens is still fitted to the user. Without this "fail-safe," the power supply state is at the "far" focal length, and a loss of power within the lens would cause the contact lens to default to "near," which can be problematic until the user is able to remove the contact lens.

[0051] This disclosure further provides, in accordance with another aspect of this disclosure, a method for fabricating an electrically switchable contact lens assembly for correcting a user's vision. The method includes the step of preparing first and second polymer elements for contact lenses, each having its own front and rear surfaces, the front surface of the first polymer element for contact lenses having a recess. Next, a liquid crystal cell is inserted into the recess. The liquid crystal cell includes a diffractive optical element and is also switchable between a mismatched 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 mismatched state, the effective refractive index of the liquid crystal is different from the effective refractive index of the diffractive optical element, and in the matched state, the effective refractive index of the liquid crystal matches the effective refractive index of the diffractive optical element. Thus, when in the matched state, the diffractive optical element does not contribute to the focusing ability of the contact lens assembly.

[0052] The method may further include the steps of lathing a first shape onto the front surface of a first polymer element for a contact lens and lathing a second shape onto the rear surface of a second polymer element for a contact lens. The second shape may match the first shape.

[0053] Thus, the two shapes take into account the presence of recesses within the main body of the lens assembly.

[0054] The method may further include the step of racing the front surface of the contact lens after the first and second polymers have been attached.

[0055] This racing step is good at cutting and removing material from the front of the second polymer element of the contact lens assembly, and in addition, this racing step can also cut and remove material from the front of the first polymer element, as far as the geometric shape allows.

[0056] The step of inserting a liquid crystal cell into a recess may further include the step of inserting photoelectric power and control elements into the recess in order to selectively supply power to the liquid crystal cell.

[0057] As recognized, such photoelectric power and control elements supply selective power to the liquid crystal cell via terminals electrically coupled to the electrodes of the liquid crystal cell.

[0058] Next, illustrative embodiments of the present disclosure will be described with reference to Figures 1 to 8, but these are merely illustrative examples.

[0059] Figure 1 shows an example of an electrically switchable liquid crystal cell 10 as an embodiment of the first aspect of this disclosure. The liquid crystal cell 10 is made of a substrate 18 into which a diffractive optical element having a number of diffractive blazes 12 is fabricated. Each of the diffractive blazes 12 is located between the front inner surface 16 and the rear inner surface 17 of the liquid crystal cell 10. For clarity, only the diffractive blazes 12 located on the left side of this figure are labeled. Each diffractive blaze 12 has an upper corner or peak 20 that is in contact with the front inner surface 16 and a lower corner or valley 30 that is in contact with the rear inner surface 17. The edge 25 of each diffractive blaze 12 extends between each peak 20 and each valley 30.

[0060] As can be seen, Figure 1 is a lateral section view, and when viewed from above, the diffraction blaze 12 has an annular shape, and the corresponding upper corner 20 and lower corner 30 are annular ridges (protrusions).

[0061] The lower half of each diffraction blaze 12 is filled with a liquid crystal material, which is a cholesteric liquid crystal consisting of a nematic liquid crystal doped with a chiral dopant. Such nematic liquid crystals are well known to those skilled in the art (those skilled in liquid crystal science), and may include E78, BL037 and / or BL038. Such chiral dopants, such as Merck ZLI-3786, CB15 and S811, are also well known to those skilled in the art in liquid crystal science.

[0062] The upper portion of each diffraction blaze 12 is made of a base material 18.

[0063] 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 peaks 20 and valleys 30 of each diffractive blaze 12.

[0064] The liquid crystal cell 10 further has electrodes (not shown) that receive voltages, which are described further below, in connection with the electrical switching of the liquid crystal cell 10 between a non-powered state and a powered state.

[0065] Figure 2 is a schematic cross-sectional view of a contact lens 50, which has a lens body 55 made of any suitable contact lens material into which the liquid crystal cell 10 shown in Figure 1 is incorporated. Furthermore, an optoelectronic component 15 associated with the liquid crystal cell 10 is incorporated into the lens body 55, and the optoelectronic component preferably includes a power supply and control elements. The optoelectronic component 15 is coupled to selectively supply power to the liquid crystal cell 10 via an electrical coupling 19.

[0066] The liquid crystal cell 10 is provided to correct the user's vision as follows: In summary, the liquid crystal cell 10 is switchable between a first mismatched state and a second matched state. In the matched state, the effective refractive index of the liquid crystal matches the effective refractive index of the diffractive optical element, and the diffractive optical element has a first focal capability. In the mismatched state, the effective refractive index of the liquid crystal does not match the effective refractive index of the diffractive optical element, and the diffractive optical element has a second focal capability different from the first focal capability.

[0067] The effective refractive index of the liquid crystal material 14 is determined by the orientation of the molecules of the liquid crystal material 14. The local alignment of molecules in the liquid crystal cell 10 is schematically shown in Figure 3A in the non-powered state. Between the front inner surface 16 and the rear inner surface 17, the director of the liquid crystal material 14 forms a helical structure, which will be further described below. The shape of the rod 60 indicates that the director of the liquid crystal is approximately parallel to the front inner surface 16 and the rear inner surface 17 and is located in the plane of this figure. In this non-powered state, the effective refractive index of the liquid crystal is polarization-independent, and n ave =0.5(n e +n o Given ), in this equation, n e is the extraordinary refractive index, n o This is the ordinary refractive index. Those skilled in the art will recognize that for a liquid crystal to behave with reasonable approximations as a single refractive index material, it is desirable that the pitch of the liquid crystal be 500 nm or less (i.e., approximately the same as or shorter than the wavelength of the incident light).

[0068] When an appropriate voltage is applied to the liquid crystal cell 10 via the photoelectronic component 15 and the electrical coupling 19, the molecules of the liquid crystal material 14 are switched to a homeotropic (perpendicular) state schematically shown in Figure 3B, in which the rod-shaped object 70 indicates that the director of the liquid crystal material 14 is perpendicular to the front inner surface 16 and the rear inner surface 17. This realignment of the liquid crystal material 14 results in a different effective refractive index. In this second switching (power supply) state, the effective refractive index is preferably n0.

[0069] When the liquid crystal material 14 is under power supply, the effective refractive index of the liquid crystal material 14 is preferably the same as the effective refractive index of the substrate 18, and in this case, the diffractive optical element does not contribute to the focal capability of the lens at all. Conversely, when the liquid crystal material 14 is not under power supply, the effective refractive index of the liquid crystal material 14 does not match the effective refractive index of the substrate 18, and therefore, the diffractive optical element contributes to the focal capability of the lens.

[0070] Now, considering the contact lens 50 containing the liquid crystal cell 10, it is preferable that the lens body 55 has positive focal capability, and that the selectively applied diffractive power to the liquid crystal cell 10 has negative focal capability. When the power to the liquid crystal cell 10 is switched off, the negative optical power of the diffractive optical element combines with the positive lens power of the lens body 55, thereby providing optical power, which has a smaller positive value than the lens power of the lens body 55 alone and is also suitable for distance vision.

[0071] Conversely, when power to the diffracting element is switched on (supplied by the photoelectronic component 15 and the electrical coupling 19), the effective refractive index of the liquid crystal cell 10 matches the effective refractive index of the substrate 18, and the contribution of optical diffraction power from the liquid crystal cell 10 is zero. In this state, the optical power of the contact lens 50 is simply the positive lens power of the lens body 55, which is the power required for near vision.

[0072] For example, the lens body 55 preferably has a focusing capability of +2D, while the focusing capability of the diffractive element in the visible light case preferably has a focusing capability of -2D. Therefore, the optical power of the contact lens can be switched between 0D (diffractive when switched off) and +2D (diffractive when switched on).

[0073] Figure 8 shows the alignment of the director of the liquid crystal material 14 located adjacent to the alignment polymer 80, with arrow 85 indicating the direction of the director of the liquid crystal material 14 located adjacent to the alignment polymer. Such alignment is used to provide polarization-independent operation of the contact lens 50.

[0074] Next, we will describe the optical modeling for different diffraction heights with reference to Figures 4 to 6B, which show graphs of diffraction efficiency (%) for different diffraction orders as a function of wavelength (nm). The diffraction efficiency for a given order is the ratio of the optical power propagating away from the diffracting element to the optical power incident on the diffracting element.

[0075] The selected substrate 18 is one with a low refractive index, such as polymethyl methacrylate (PMMA) lens material.

[0076] The liquid crystal material 14 is preferably a mixture of BL037 and BL038 materials, and it has been found that a 50 / 50 mixture produces an extremely good refractive index suitable for near-field performance without producing any undesirable characteristics in far-field performance (100% BL037 has been found to produce a slight shift towards red in the far-field view).

[0077] Figure 4A is 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, in which the effective refractive indices of the liquid crystal and the diffractive optical element are substantially identical, i.e., matched, and therefore the diffractive optical element is not in an active state. The intensities of various order diffraction profiles are observed from the diffractive optical element. As can be seen, the intensity of the profiles observed from the diffractive optical element is small at all wavelengths. The first curve 110 in 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. The first and second-order diffraction profiles in Figure 4A are shown multiplied by 100. As can be seen from the graph, the residual first-order light at 450 nm is approximately 0.05%, and the residual second-order light at the same wavelength is close to 0.01%. The overall diffraction efficiency (given by line 120) is approximately 50%. The 0th order (i.e., directly incident) light accounts for over 99%, as shown by the dotted line 125.

[0078] Figure 4B shows a graph of diffraction efficiency in the far field of view when the height of the diffractive element is 3.33 μm. This occurs when the liquid crystal cell 10 is in a non-powered state, and as a result, the diffractive optical element is visible and also contributes to the power of lens 50. This can be considered the far field of view state. In the case of power cut-off, the contact lens defaults to this far vision state, in which case the power of lens 50 is without the contribution of the diffractive element. Curve 130 shows the primary peak, which represents the majority of the light visible to the user. It has a peak at 480 nm and a tail at higher wavelengths. Curve 130 shows the zeroth order (i.e., direct light), which should be as small as possible in this case, but has a trough at 450 nm and shows a slightly higher level at higher wavelengths, thereby introducing some blue shift. Curve 145 shows the secondary light.

[0079] Figure 5A shows a graph of near-field diffraction efficiency that is almost the same as that of Figure 4A, but the height of the diffracting element is 3.76 μm. In this case as well, the liquid crystal cell 10 is in a matched state, in which the effective refractive indices of the liquid crystal and the diffracting optical element are substantially the same, i.e., they are in a matched state. The first and second order diffraction profiles in Figure 5A are shown multiplied by 100. As can be seen from curve 210, the residual first order light at 450 nm is approximately 0.1%. Another curve 215 shows the second order diffraction. The overall diffraction efficiency (given by line 220) is approximately 55%. The zero-order (i.e., directly incident) light exceeds 99%, as shown by the dotted line 225.

[0080] Figure 5B shows a graph of far-field diffraction efficiency that is almost the same as that of Figure 4B, with a diffracting element height of 3.76 μm. In this case as well, far-field diffraction occurs when the liquid crystal cell 10 is in a second inactive state, i.e., a far-field vision state. Curve 230 shows a primary peak now occurring at approximately 525 nm, achieving an acceptable performance level beyond the visible spectrum. Similarly, curve 240 shows a zero-order trough at 500-55 nm. Curve 245 shows the secondary light.

[0081] Figure 6A shows a graph of near-field diffraction efficiency that is almost the same as that of Figures 5A and 6A, but the height of the diffracting element is 4.19 μm. In this case as well, the liquid crystal cell 10 is in a matched state, in which the effective refractive indices of the liquid crystal and the diffracting optical element are substantially the same, i.e., they are in a matched state. The first and second order diffraction profiles in Figure 6A are shown multiplied by 100. As can be seen from curve 260, the residual first order light at 450 nm is approximately 0.1%. Another curve 265 shows the second order diffraction. The overall diffraction efficiency (given by line 270) is approximately 55%. The 0th order (i.e., directly incident) light exceeds 99%, as shown by dotted line 275.

[0082] Figure 6B shows a graph of far-field diffraction efficiency that is almost the same as that of Figures 5B and 6B, but the height of the diffracting element is 4.19 μm. In this case as well, far-field diffraction occurs when the liquid crystal cell 10 is in the second inactive state, i.e., the far-field visual acuity state.

[0083] Curve 280 shows that the 0th and 1st order peaks now occur at approximately 500 nm, and curve 290 shows that the 0th order trough is at 500-600 nm. This indicates a slight redshift. Curve 295 shows the 2nd order light.

[0084] Therefore, as can be understood, diffraction height primarily affects far-field performance, with a diffraction height of 3.33 μm causing the envelope to shift to the left (representing some effect on the blue end of the shift), and conversely, a diffraction height of 4.19 μm causing a shift to the right (representing some effect on the red end of the spectrum). Given these results, the preferred refractive height in this example was determined to be approximately 3.76 μm.

[0085] Referring also to Figure 7, a magnified cross-sectional view of the diffractive blaze 12 of the liquid crystal cell 10 is shown in a side view. As can be seen, viewed from above, the blaze 12 has an annular shape. As can be understood by observing Figure 1, a number of diffractive blazes 12 are required to form a diffractive optical element. There may be 16 diffractive blazes, or there may be more or fewer diffraction orders than 16. The number of blazes may be proportional to the square of the diameter of the optical zone of the contact lens, and also directly proportional to the optical power to be provided by the diffractive optical element.

[0086] The standard diffraction blaze shape used to obtain the optimal diffraction efficiency is shown by a dotted line, and both of these standard diffraction blaze shapes have an upper corner 20 and a lower corner 30 at substantially 90° angles, along with a vertical edge 25 between the upper corner 20 and the lower corner 30. The height 35 of the diffractive optical element substantially coincides with the length of the vertical edge 25 (i.e., the vertical separation distance between the upper corner 20 and the lower corner 30).

[0087] To our surprise, the applicant discovered that by replacing one or both of the upper and lower corners 20, 30 with curves of appropriate length, the problem in scattering field liquid crystal alignment is mitigated in a way that the trade-off in terms of diffraction efficiency is acceptable.

[0088] In this embodiment, a lower curve 21 having radius r1 (line 23) and terminating at a valley 28 is replaced by a lower corner 30. An upper curve 22 having radius r2 (line 24) and terminating at a valley 28 is replaced by an upper corner 20. Now, the height 35 of the diffractive optical element is determined by the vertical separation distance 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. (The edge 26 between the lower curve 21 and the upper curve 22 can be omitted entirely if the lower curve 21 and the upper curve 22 touch each other.)

[0089] Furthermore, the lower curve 21 and the upper curve 22 can create arcs with a central angle of less than 90°. Variations of 40°, 60°, or other central angles can be adopted. In these cases, the edge 26 is preferably angled away from the perpendicular.

[0090] Surprisingly, it was found that, for a diffraction height of approximately 3.76 μm, by replacing the lower corner 30 of each blaze 12 with a downward curve 21 having a radius of curvature r1 (line 23) of 5 μm to 50 μm, and replacing the upper corner 20 of each blaze 12 with an upward curve 22 having a radius of curvature r2 (line 24) of 0.1 nm to 20 nm, an acceptable level of optical performance of the diffracting element of the liquid crystal cell 10 can be obtained while compensating for the good switching characteristics of the liquid crystal material 14.

[0091] The contact lens described above provides unexpectedly good peripheral imaging performance. Light is expected to enter the diffractive optical element from a wide range of angles, and due to the wide variation in the angle of incidence and the curvature of the cornea, large changes in the optical path length through the diffractive optical element can occur, resulting in poor optical performance. However, the applicant has discovered that peripheral light entering the contact lens and traveling through the pupil passes through a portion of the diffractive optical element that is almost perpendicular to the incident light, meaning that this light is from almost the same direction and there is almost no variation in the angle of incidence. This results in good peripheral imaging performance.

[0092] Furthermore, as the angle of incidence of light increases from the perpendicular, the amount of light passing through the diffractive optical element decreases. At a certain angle, virtually no light passes through the diffractive optical element, and no optical artifacts are observed. For example, with incident light at approximately 53° and a pupil size of 5mm, about half of the detected light beam enters the diffractive optical element, and the other half passes through the non-diffractive region of the contact lens. For light with a larger angle of incidence than this, the effective area of ​​the diffractive optical element exposed to light decreases further, so once the light beam completely leaves the diffractive region, optical artifacts become non-negligible. Therefore, as far as the user is concerned, there should be no abrupt start / stop of the diffractive region; only the amplitude of the contribution changes smoothly. In contrast to the eyeglass lens example, a clear leap can be observed when switching between viewing through the diffractive optical element and not viewing through the diffractive optical element.

[0093] The applicant also found that the astigmatism of peripheral light caused by incident light passing through the diffractive optical element at a non-right angle is acceptable (average of about 0.3D).

[0094] Next, referring to Figures 9A to 9F and Figure 10, a method for fabricating contact lenses is shown. In Figure 9A, a first anhydrous polymer blank 200 is prepared. This method begins with a cut 320, which is made on the rear surface 310 of the first polymer blank 300 to the required curvature using a lathe tool (box 400 in Figure 10). The lathe tool used is typically a digital lathe with an industrial diamond.

[0095] As shown in Figure 9B, the corresponding cut surface 335 of the first polymer blank 300 is then firmly attached to the jig 330 (box 410) by wax 340 applied along the cut surface 335.

[0096] Next, as shown in Figure 9C, material 350 is removed from the front surface 345 of the first polymer blank 300 using a lace tool, the purpose of which is to engrave a stepped shape (box 420) on the front surface 345, which includes a recess 360.

[0097] Next, the second polymer blank 370 is subjected to a cutting process as shown in Figure 9D, in which case the cutting tool is to create another stepped shape (box 430) that substantially matches the stepped shape of the front surface of the first polymer blank 300, except for the recess 360.

[0098] The optoelectronic package 380 is inserted into the recess 360 of the first polymer blank 300 (box 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.

[0099] Next, glue is applied between the first polymer blank 300 and the second polymer blank 370, and these two are bonded together with the photoelectron package 380 sandwiched between them in the recess 360 (box 450).

[0100] Next, the front surface 385 of the second polymer blank 370 is cut off using a lathe tool (box 460) to form a lens assembly 390 as shown in Figure 9E, which includes a shaped lens element 395 bonded to the first polymer blank 300, which is still mounted on the jig 330 (not shown in the side view of Figure 9E).

[0101] Finally, as shown in Figure 9F, the lens assembly 390 is removed from the fixture (box 470) by dissolving the wax 340. The photoelectron package 380 is shown in this excision diagram.

[0102] It is preferable to polish one or both sides of the lens assembly 400 if necessary to remove any edges, and then hydrate the lens assembly 400 by immersing it in an extraction and / or hydration solution.

[0103] Although the contents of this disclosure have been described and illustrated in relation to specific embodiments, those skilled in the art will understand that the contents of this disclosure can be implemented in a wide variety of modifications not specifically shown herein. Some possible modifications are described below, but these are merely illustrative examples.

[0104] The use of diffractive optical elements is not limited to liquid crystal cells made of cholesteric liquid crystals. For example, other types of liquid crystal cells, including undoped nematic and smectic liquid crystals, can be used.

[0105] The stepped arrangements formed by cutting in the first and second polymer blanks may differ from those shown in the drawings, as may be the shapes and forms of the recesses.

[0106] Furthermore, instead of the racing process described above, another contact lens manufacturing process, such as molding, may be used.

[0107] The structure of the diffraction element described above, including numerous diffraction blades and dimensions such as blade height and radii of curvature of peaks and valleys, may differ from the structure described above.

[0108] Furthermore, in contrast to the above-described configuration, the liquid crystal cell may be configured such that it is mismatched when powered and matched when not powered. In such a configuration, the liquid crystal cell does not provide positive power when not powered, and provides positive power to the lens when powered.

[0109] Where the above description refers to integers or elements for which known, obvious, or predictable equivalents exist, such equivalents are incorporated herein as if they were individually described. The claims that define the true scope of this disclosure should be referred to, and such true scope should be understood to include any such equivalents. Furthermore, it will be understood that integers or features of this disclosure described as preferred, advantageous, or favorable are optional and do not limit the scope of the invention as described in the independent claims. Moreover, such optional integers or features may be beneficial in some embodiments of this disclosure, but may be undesirable and therefore should not be described in other embodiments.

Claims

1. An electrically switchable liquid crystal cell for changing the focal ability of a contact lens, wherein the liquid crystal cell has a diffractive optical element that can be switched between a mismatched state and a matched state. In the aforementioned mismatched state, the effective refractive index of the liquid crystal cell is different from the effective refractive index of the diffractive optical element. In the aforementioned matching state, the effective refractive index of the liquid crystal cell matches the effective refractive index of the diffractive optical element, and therefore, the diffractive optical element does not contribute to the focal capability of the contact lens. The diffractive optical element has a plurality of diffraction blades, each of the plurality of diffraction blades having a peak and a valley, and at least one of the plurality of diffraction blades has a peak and / or valley with a rounded corner, in a liquid crystal cell.

2. The liquid crystal cell according to claim 1, wherein at least one of the plurality of diffraction blades has a valley portion with a rounded corner having a radius of curvature of 5 μm to 50 μm.

3. The liquid crystal cell according to claim 1, wherein each of the plurality of diffraction blades has a valley portion with a rounded corner having a radius of curvature of 5 μm to 50 μm.

4. The liquid crystal cell according to claim 1, wherein at least one of the plurality of diffraction blades has a peak with a rounded corner having a radius of curvature of 0.1 μm to 20 μm.

5. The liquid crystal cell according to claim 1, wherein each of the plurality of diffraction blades has a peak with a rounded corner having a radius of curvature of 0.1 μm to 20 μm.

6. The liquid crystal cell according to claim 1, wherein the plurality of diffraction blazes have an average height of 2.5 μm to 3.8 μm.

7. The liquid crystal cell according to claim 6, wherein the plurality of diffraction blazes have an average height of 3.7 μm to 3.8 μm.

8. The liquid crystal cell according to claim 1, wherein the liquid crystal cell is made of cholesteric liquid crystal.

9. An electrically switchable contact lens for correcting a user's vision, comprising the liquid crystal cell described in claim 1.

10. The contact lens according to claim 9, wherein the contact lens has a polymer lens body.

11. In the mismatched state, the liquid crystal cell has a negative focal capacity that contributes to the contact lens, and as a result, in the mismatched state, the resulting focal capacity of the contact lens is less positive than in the matched state, according to claim 9.

12. A method for manufacturing an electrically switchable contact lens assembly for correcting a user's vision, wherein the method is: The process includes the step of preparing first and second polymer elements for contact lenses, each having its own front and rear surfaces, wherein the front surface of the first polymer element for contact lenses has a recess, The process includes inserting a liquid crystal cell containing a diffractive optical element into the recess, wherein the liquid crystal cell is switchable between a mismatched state and a matched state. The process includes the step of attaching the front surface of the first polymer element for contact lenses to the rear surface of the second polymer element to form the contact lens assembly, In the aforementioned mismatched state, the effective refractive index of the liquid crystal cell is different from the effective refractive index of the diffractive optical element, and in the aforementioned matched state, the effective refractive index of the liquid crystal cell is the same as the effective refractive index of the diffractive optical element, and therefore, in the aforementioned matched state, the diffractive optical element does not contribute to the focusing ability of the contact lens assembly, a method.

13. The step further includes racing a first shape onto the front surface of the first polymer element for the contact lens, wherein the first shape includes the recess. The method according to claim 12, further comprising the step of racing a second shape onto the rear surface of the second polymer element for a contact lens, wherein the second shape conforms to the first shape.

14. The method according to claim 12, further comprising the step of racing the front surface of the contact lens assembly after the mounting step.

15. The method according to claim 12, wherein the step of inserting the liquid crystal cell into the recess further includes the step of inserting photoelectric power and control elements for selectively supplying power to the liquid crystal cell.

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