Dynamic lens for controlling myopia

Abstract

Eyeglasses (20) for treating myopia comprise an eyeglasses frame (25) and first and second optical elements (22, 24) having a controllable optical phase distribution and mounted in the eyeglasses frame such that when a user wears the eyeglasses, the optical phase distribution of the first and second optical elements (22, 24) is controlled by the optical phase distribution of the first and second optical elements (22, 24). The first and second optical elements are positioned in respective lines of sight of the left and right eyes of the user. The eyewear further comprises a control circuit (26) configured to control an optical phase distribution of the first optical element and the second optical element, the first optical element and the second optical element are arranged so as to apply optical disturbances to light incident on the left eye and the right eye through respective peripheral regions (39) of the first optical element and the second optical element in a time alternation between the first optical element and the second optical element.

Description

Cross-references to related applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 505,429 and U.S. Provisional Patent Application No. 63 / 505,430, both filed on June 1, 2023, which are incorporated herein by reference. Invention Field

[0002] This invention relates generally to optical devices, and more particularly to electrically tunable lenses. background

[0003] Myopia (nearsightedness) is a condition in which the human eye overfocuses light, creating an image in front of the retina instead of on it. Therefore, the image perceived on the retina is blurry. Several treatments have been investigated to slow the progression of myopia (the increase in optical power required over time to make distant views clear). These methods are often referred to as “myopia progression control,” “myopia management,” or “myopia management.” Research has shown that applying perturbation to peripheral vision can slow the progression of myopia. Perturbations can include reducing image contrast and / or blurring, such as by applying defocus; all of these are referred to as “perturbations” below.

[0004] An electrically tunable lens is an optical element having an optical phase profile that can be controlled by applying an appropriate control voltage. The optical characteristics of such an element, such as focal length and / or the position of the optical axis, can be adjusted during use, typically under electronic control. Such lenses can be used in a variety of applications, including, in particular, as visual aids.

[0005] U.S. Patent 10,036,901 (the disclosure of which is incorporated herein by reference) describes an optical device. The optical device includes an electro-optical layer having a locally effective refractive index at any given location within an active region of the layer, the locally effective refractive index being determined by a voltage waveform applied across the layer at that location. The device also includes a common electrode and an array of excitation electrodes located above an active region on a first side of the electro-optical layer, the array of excitation electrodes including parallel conductive strips extending above an active region on a second side of the electro-optical layer opposite the first side. The device further includes control circuitry individually connected to each excitation electrode and configured to independently control each excitation electrode by applying a corresponding control voltage waveform to the excitation electrode to tune the phase modulation distribution of the electro-optical layer, and configured to simultaneously modify the corresponding control voltage waveforms applied to multiple excitation electrodes, thereby modifying the phase modulation distribution.

[0006] U.S. Patent 10,466,391 (the disclosure of which is incorporated herein by reference) describes an electrically tunable lens having an electro-optic layer and segmented excitation electrodes. The segmented electrodes are driven by a control voltage waveform to generate a specified phase modulation distribution on the lens.

[0007] U.S. Patent Application Publication 2022 / 0214566 (the disclosure of which is incorporated herein by reference) describes an electrically tunable lens in which a drive signal is applied to generate a first phase modulation distribution in a central region that intercepts the user’s eye’s line of sight and corrects the eye’s refractive error, and to generate a second phase modulation distribution in a peripheral region that causes a disturbance in the peripheral region. Overview

[0008] The embodiments of the present invention described below provide improved electronically tunable optical devices and methods of operation thereof.

[0009] Therefore, according to embodiments of the present invention, eyeglasses for treating myopia are provided, including an eyeglass frame and a first optical element and a second optical element, the first and second optical elements having a controllable optical phase distribution and being mounted in the eyeglass frame such that when a user wears the eyeglasses, the first and second optical elements are positioned in the respective lines of sight of the user's left and right eyes. The eyeglasses also include a control circuit configured to control the optical phase distribution of the first and second optical elements to apply optical perturbations to light incident on the left and right eyes through the respective peripheral regions of the first and second optical elements with a temporal alternation between the first and second optical elements.

[0010] In one embodiment, an optical perturbation blurs the image seen by the eye through the peripheral region. For example, an optical perturbation may include a refractive power, such as a positive refractive power, selected to defocus the image formed on the retina of the eye.

[0011] In some embodiments, optical perturbations reduce the contrast of the image seen by the eye through the peripheral region.

[0012] In another embodiment, the control circuit is configured to control the optical phase distribution so that, while optical perturbations are alternately applied in the peripheral region, the left and right eyes can achieve clear vision through the respective central zones of both the first and second optical elements. Additionally or alternatively, the respective central zones have a fixed lateral dimension. Alternatively, the respective central zones have a variable lateral dimension. Further alternatively, the optical phase distribution is controlled such that, while optical perturbations are applied alternately in the peripheral region over time, the respective central zones of the first and second optical elements have the same lateral dimension. Further alternatively, the control circuit is configured to alternately change the lateral dimensions of the respective central zones of the first and second optical elements in conjunction with the time-interval alternation of optical perturbations in the peripheral region.

[0013] In some embodiments, the control circuit is configured to change the lateral dimensions of the respective central regions of the first and second optical elements among at least three different values.

[0014] In another embodiment, the central region of clear vision has a lateral dimension of at least 8 mm. Additionally or alternatively, the control circuitry is configured to control the optical phase distribution such that when an optical disturbance is applied to the peripheral region of one of the optical elements, the other optical element provides clear vision in both the central and peripheral regions. Alternatively, the central region of clear vision has a lateral dimension of less than 2 mm.

[0015] In some embodiments, the control circuitry is configured to control the optical phase distribution in order to apply myopia correction in the central area.

[0016] In another embodiment, the control circuit is configured to control the optical phase distribution such that the optical disturbance alternates at a time alternation rate between 10 Hz and once per day. Additionally or alternatively, the control circuit is configured to control the optical phase distribution such that the period of the optical disturbance's time alternation is between one minute and four hours.

[0017] In another embodiment, the time alternation between the first and second optical elements includes a gradual time transition of the perturbation in the respective peripheral regions, for example, having a duration of at least 5 seconds.

[0018] In some embodiments, the control unit is configured to apply optical disturbances to the first optical element and the second optical element at different corresponding time periods.

[0019] In another embodiment, the control unit is configured to apply optical disturbances to the first optical element and the second optical element with different corresponding disturbance intensities.

[0020] In another embodiment, the first optical element and the second optical element include a compound lens, each compound lens including a corresponding fixed lens component having a predetermined refractive power and a corresponding optical phase modulator configured to apply an optical perturbation under the control of a control circuit.

[0021] In some embodiments, the glasses include at least one sensor configured to output a signal indicating operating conditions of the glasses, wherein control circuitry is configured to modify the optical phase distribution in response to the signal. Additionally or alternatively, the signal indicates the distance to an object viewed by the user. Further additionally or alternatively, the signal indicates the user's gaze direction. Further additionally or alternatively, the signal indicates the level of ambient light, and control circuitry is configured to adjust the size of the clear central area of ​​the optics in response to the level of ambient light.

[0022] According to an embodiment of the present invention, a method for treating myopia is also provided, comprising applying an optical perturbation to light incident on the user's left and right eyes at the periphery, such that the optical perturbation is applied alternately between the left and right eyes over time.

[0023] According to embodiments of the present invention, eyeglasses for treating myopia are also provided, comprising an eyeglass frame and a first optical element and a second optical element mounted in the eyeglass frame such that, when a user wears the eyeglasses, the first optical element and the second optical element are positioned within the respective lines of sight of the user's left and right eyes. Each of the first optical element and the second optical element includes at least one liquid crystal layer and conductive electrodes extending over opposing first and second sides of the at least one liquid crystal layer. The electrodes include an excitation electrode array comprising parallel conductive strips extending along respective mutually parallel axes across the first side of the at least one liquid crystal layer. The eyeglasses also include control circuitry coupled to apply corresponding control voltage waveforms to the excitation electrodes located in respective peripheral regions of the first optical element and the second optical element, so as to apply optical perturbations to light passing through the peripheral regions at time alternations between the first optical element and the second optical element.

[0024] In the disclosed embodiments, in each of the first optical element and the second optical element, at least one liquid crystal layer includes a first liquid crystal layer and a second liquid crystal layer arranged in series, and the conductive electrode includes a first set of parallel conductive strips extending over the first liquid crystal layer along a first direction and a second set of parallel conductive strips extending over the second liquid crystal layer along a second direction orthogonal to the first direction.

[0025] In some embodiments, the control circuit is configured to apply a control voltage waveform to a corresponding peripheral group of parallel conductive strips in both the first and second sets, thereby ensuring that the rectangular central region of each of the optical elements remains undisturbed. In one embodiment, the control circuit is configured to apply a control voltage waveform to a corresponding central group of parallel conductive strips in both the first and second sets to apply myopia correction in the rectangular central region.

[0026] In another embodiment, each of the conductive strips is divided into two or more segments extending above corresponding, non-intersecting portions of the strip's axis, and control circuitry is coupled to apply corresponding control voltage waveforms to corresponding peripheral segments of the excitation electrode in order to apply optical perturbations.

[0027] In the disclosed embodiments, the control circuit is configured to apply a corresponding control voltage waveform such that the optical phase distribution of the liquid crystal layer in the peripheral region simulates a microlens array. Alternatively, the control circuit is configured to apply a corresponding control voltage waveform such that the optical phase distribution of the liquid crystal layer in the peripheral region simulates a positive lens. Additionally or alternatively, the control circuit is configured to apply a corresponding control voltage waveform such that the optical phase distribution of the liquid crystal layer in the peripheral region simulates a Fresnel lens. Further alternatively, the control circuit is configured to apply a corresponding control voltage waveform such that the liquid crystal layer applies a pseudo-random phase pattern in the peripheral region.

[0028] The invention will be more fully understood from the following detailed description of embodiments thereof, taken in conjunction with the accompanying drawings, in which: Brief description of the attached diagram Figure 1 This is a schematic illustration of eyeglasses for myopia control according to an embodiment of the present invention; Figure 2 This is a schematic side view of an electrically tunable lens according to an embodiment of the present invention; Figure 3A This is a schematic diagram of an electrically tunable optical phase modulator according to an embodiment of the present invention; Figure 3B yes Figure 3A A schematic detail of the excitation electrodes in an optical phase modulator; Figure 3C yes Figure 3A A schematic front view of the common electrode in an optical phase modulator; Figure 3D This is a schematic illustration of a two-dimensional electrically tunable optical phase modulator according to an embodiment of the present invention; Figure 4 This is a schematic front view of an electrically tunable lens for myopia control according to an embodiment of the present invention; Figure 5 This is a schematic front view of the segmented excitation electrodes of an optical phase modulator according to an embodiment of the present invention; Figure 6 According to an embodiment of the present invention Figure 5 A schematic front view of an optical phase modulator, showing the electrical control circuitry of segmented electrodes; Figure 7A and Figure 7B This is an embodiment of the present invention. Figure 1 Schematic front views of the left and right lenses of the glasses in two corresponding time periods; Figure 8A , Figure 8B and Figure 8C This is according to another embodiment of the present invention. Figure 1 Schematic front views of the left and right lenses of the glasses in three corresponding time periods; Figure 9A This is a schematic curve showing the change in refractive power (in diopters) of an electrically tunable optical phase modulator according to an embodiment of the present invention as a function of position on the lens; Figure 9B It is based on an embodiment of the present invention. Figure 9A A schematic curve showing how the phase modulation distribution (in arbitrary units of phase (AU)) applied by the optical phase modulator varies with the position on the lens. Figure 9C This is a schematic curve showing the change of phase modulation distribution applied by an optical phase modulator with position on the lens according to another embodiment of the present invention; Figure 10 This is a schematic curve of the phase modulation distribution applied by an electrically tunable optical phase modulator according to another embodiment of the present invention; and Figure 11 This is a schematic curve of the phase modulation distribution applied by an electrically tunable optical phase modulator according to another embodiment of the present invention. Detailed Implementation

[0029] summary The aforementioned U.S. Patent Application Publication 2022 / 0214566 describes a lens for myopia control having a sharp, optically corrected central area and a disturbed peripheral area produced on each lens. The central area is sharp to allow the user to view objects undisturbed, although it can be combined with refractive correction according to the user's prescription. The refractive properties of the peripheral area surrounding the entire sharp area or a portion thereof are modified to disturb the user's peripheral vision by blurring the peripheral image in the user's eye or by reducing the contrast of these images. Myopia control requires a sufficient portion of peripheral vision to be disturbed, thus limiting the usable area of ​​the central area.

[0030] Spectacular lenses with a fixed central area of ​​sharpness for each lens will work satisfactorily, as long as the line of sight for each eye is blocked by the corresponding area of ​​sharpness. However, when a user views different parts of a wider scene, the user's eyes rotate and may shift the corresponding line of sight from the fixed central area to the peripheral area, thus blurring the user's vision. Therefore, the user's field of vision (the range of angles at which the user can rotate their eyes while still experiencing sharp vision) is limited by the size of the central area in conjunction with the distance of the spectacular lens from the pupil. The lateral size of the fixed, sharp central area should be large enough so that the user can see clearly straight ahead and also clearly when looking to the sides at a reasonable angle. Otherwise, the user may experience discomfort due to a narrow field of vision ("tunneling vision") and may even stop wearing the glasses altogether. On the other hand, the central area should be small enough to leave sufficient space for peripheral disturbances. Increasing the size of the central area to reduce tunneling vision and associated discomfort reduces the area of ​​disturbance and may reduce the therapeutic efficacy of the glasses.

[0031] As noted in U.S. Patent Application Publication 2022 / 0214566, electrically tunable lenses can be controlled to shift the central region of each lens along with its peripheral region to accommodate changes in the direction of gaze. However, controlling the position of the central region may require the use of an eye tracker or other devices capable of detecting the direction of the user's gaze. While this approach can mitigate the problem of narrowed field of vision due to a disturbed peripheral region, the required tracking equipment increases the complexity, cost, and power consumption of the glasses.

[0032] The embodiments of the invention described herein resolve the conflicting requirements of a large field of vision and therapeutic efficacy by dynamically alternating the perturbation between the left and right eyes. A pair of electrically tunable spectacle lenses are controlled such that at any given time, one eye sees through a large, clear central area (or even the entire central area of ​​the lens, i.e., without perturbation), while the other eye has a smaller, clear central area (or even no central area), resulting in a large area of ​​perturbation on the retina. Thus, the user sees clearly with one eye in a large field of vision, while the other eye experiences considerable perturbation. Alternating this arrangement between the two eyes ensures that both eyes experience peripheral perturbation while allowing each eye to see clearly in turn. This alternation provides the user with the subjective feeling of clear vision while simultaneously treating myopia.

[0033] In the disclosed embodiments, the eyeglasses for treating myopia include an eyeglass frame, a first optical element, a second optical element, and control circuitry. The optical elements have a controllable optical phase distribution and are mounted in the eyeglass frame such that when the user wears the eyeglasses, the first and second optical elements are positioned within the respective lines of sight of the user's left and right eyes. The control circuitry controls the optical phase distribution of the first and second optical elements to apply optical perturbations to light incident on the left and right eyes through their respective peripheral regions at time intervals between the first and second optical elements.

[0034] In some embodiments, each of the first and second optical elements includes at least one liquid crystal layer and a conductive electrode extending over an opposite side of the at least one liquid crystal layer. The electrode includes an excitation electrode array comprising parallel conductive strips extending along respective mutually parallel axes across one side of the at least one liquid crystal layer. A control circuit applies a corresponding control voltage waveform to the excitation electrode located in a corresponding peripheral region of the optical element to alternately apply optical perturbations between the first and second optical elements at desired times.

[0035] Alternatively, other means can be applied to alternately perturb the peripheral areas of the left and right optical elements. For example, optical or mechanical perturbations can be applied to blur or otherwise defocus the user's vision, or to reduce the optical contrast in the peripheral areas. Alternating perturbations between the left and right eyes using any suitable means can effectively control myopia and is considered to be within the scope of this invention.

[0036] System Description Figure 1 This is a schematic illustration of eyeglasses 20 for myopia control according to an embodiment of the present invention. Eyeglasses 20 includes electrically tunable lenses 22 and 24 mounted in a frame 25. As will be described in detail below, the optical characteristics of the lenses are controlled by a control circuit 26 powered by a battery 28 or other power source. The control circuit 26 typically includes an embedded microprocessor with hardwired and / or programmable logic components and a suitable interface for performing the functions described herein. These and other components of eyeglasses 20 are typically mounted on or within the frame 25, or alternatively contained in a separate unit (not shown) connected to the frame 25 by wires.

[0037] The control circuit 26 may also be coupled to an external computing device 42, such as a computer, tablet, or mobile phone, via a wired link 40 or a wireless link (such as WiFi). The computing device 42 typically includes a microprocessor with logic components, internal memory, a display, and input / output devices, the specifics of which vary depending on the device type. The computing device 42 is configured to upload instructions to the control circuit 26 and download data related to the functionality of the glasses 20 from the control circuit.

[0038] Each lens 22 and 24 includes a central region 37 and a peripheral region 39. For clarity, in Figure 1 Only the central region 37 and the peripheral region 39 of lens 22 are shown. In the illustrated example, the peripheral region 39 is annular, extending 360° around the circular central region 37; alternatively, the peripheral region 39 may extend around a smaller arc angle. The central region 37 and the peripheral region 39 may alternatively have different shapes, such as rectangular or square. The corresponding central regions 37 of lenses 22 and 24 may have equal or different lateral dimensions, and these lateral dimensions may be fixed or variable, as will be described in further detail below.

[0039] For myopia control, control circuit 26 applies control waveforms to lenses 22 and 24 according to phase modulation distribution parameters stored in memory 38. These parameters indicate the characteristics to be applied in the respective central region 37 and peripheral region 39 of the lenses. As previously described, the phase modulation distribution of the central region 37 in each lens 22, 24 is typically selected such that the central region provides clear vision for the corresponding eye while potentially correcting refractive errors. Parameters for each peripheral region 39 are selected to perturb the peripheral vision of the corresponding eye, while the extent of the peripheral region (and therefore the extent of the corresponding central region) dynamically changes alternately between the left and right eyes. The scheme for alternation between eyes is described in further detail below.

[0040] In some embodiments, the glasses 20 may additionally include one or more sensors 30 that output signals indicative of the glasses' operating conditions. Control circuitry 26 modifies the optical phase distribution in response to these signals. For example, sensor 30 may sense the gaze direction 32 of the wearer's eyes and may also sense the distance from the eyes to the object 34 being viewed, as well as the level of ambient lighting. Further details of this sensing are described in the aforementioned U.S. Patent Application Publication 2022 / 0214566. However, alternating perturbations between lenses 22 and 24 can eliminate the need to control the lenses based on sensor readings.

[0041] In addition, the control circuit 26 can adjust the lateral dimension of the clear center area 37 of the optical element in response to the measured ambient light level.

[0042] Figure 2 This is a schematic side view of an electrically tunable lens according to an embodiment of the present invention. Lens 24 typically has a similar design.

[0043] In the illustrated embodiment, lens 22 is a compound lens comprising multiple elements: fixed lenses 52 and 56, typically made of glass or plastic, provide baseline refractive power, which is dynamically modified by an electrically tunable phase modulator 54, as described below. Figures 3A-3D and Figures 5-6 The following is a more detailed description. Although the electrically tunable phase modulator 54 is shown as a flat plate, it can also be bent (cylindrical or spherical) in one or two dimensions on one or both sides.

[0044] Although fixed lenses 52 and 56 are shown as physically separate from the tunable phase modulator 54, in practice these components are typically packaged in a single unit, in the form of an eyeglass lens. (For this reason, lens 22 itself can be considered an electrically tunable lens). Therefore, in any region of lens 22, the total refractive power of the lens is generally the sum of the fixed refractive power of lenses 52 and 56 and the variable refractive power (or other phase modulation distribution) applied by the phase modulator 54. Alternatively, lens 22 may consist only of electrically tunable elements and may not require fixed lenses 52 and 56, especially when the amount of refractive correction is small.

[0045] Figures 3A-3C A one-dimensional optical phase modulator 60 is schematically shown according to an embodiment of the present invention, while Figure 3D This is a diagram of a two-dimensional optical phase modulator 62 comprising two one-dimensional phase modulators 60. (The terms "one-dimensional" and "two-dimensional" refer to the characteristics of the phase distribution applied by the optical phase modulators.) Figure 3A This is a diagram of a one-dimensional phase modulator 60, and Figure 3B and Figure 3C This is a side view of the phase modulator from the opposite side.

[0046] As described in U.S. Patent 10,036,901, the phase modulator 60 includes an electro-optic layer 64 (such as a liquid crystal layer), which, as is known in the art, is typically contained by a suitable encapsulation. Layer 64 has a locally effective refractive index at any given location within its active region (e.g., within the region of the layer that actually contains the liquid crystal), which is determined by a voltage applied across the layer at that location.

[0047] Transparent substrates 66 and 68 (such as glass preforms) are positioned on opposite sides of layer 64, and as... Figure 3B and Figure 3CAs shown, corresponding excitation electrodes are disposed on the substrate. The electrodes comprise a transparent conductive material, such as indium tin oxide (ITO) known in the art. Alternatively, non-transparent electrodes can be used, provided they are thin enough that they do not cause disturbing optical effects. A common electrode 70 on substrate 68 is located above the active region of layer 64 on one side. Although this common electrode is shown as a monolithic rectangle, it can alternatively have any suitable shape that adequately covers the active region of layer 64. An array of excitation electrodes 72 (comprising parallel strips of transparent conductive material on substrate 66) extends above the active regions on the opposite sides of layer 64. (Hereinafter, "parallel" may also include electrodes offset by a few degrees in angle). In this example, the parallel strips are vertically oriented, i.e., the reference coordinate system 80 is oriented in the Y direction. Although for visual clarity, in Figure 3B Only a few electrodes 72 are shown, but in reality, a much larger number of electrodes can be used to achieve good optical quality. For example, modulator 60 may include approximately 20 strip electrodes, or possibly at least 100 strip electrodes for excitation, or even 400 or more.

[0048] Control circuitry 74 is coupled to apply a corresponding control voltage to excitation electrode 72 relative to a common voltage level of electrode 70. As is known in the art, control circuitry 74 typically includes amplifiers and / or switches that control the amplitude or duty cycle, or both, of the voltage applied to each electrode 72. The pattern of the amplitude and / or duty cycle applied to the electrodes determines the phase modulation distribution of layer 64. The circuit components in circuitry 74 are typically fabricated as silicon chips and then glued onto substrate 66, such as… Figure 3B As shown. Alternatively, some or all components of circuit 74 can be formed on a separate chip and connected to substrate 66 via suitable bonding wires or other connectors. In either case, control circuitry can be located on one side of the electrode array, such as... Figure 3B As shown, and no part of the control circuitry needs to be located above the active area of ​​layer 64.

[0049] Circuit 74 can simultaneously and independently modify the control voltage applied to each of a set of excitation electrodes 72 (which may include all electrodes). For example, circuit 74 can alternately update the control voltage applied to all odd-numbered electrodes and all even-numbered electrodes in the array. This method is easily scalable to large electrode counts and can therefore be used to create electrically tunable optical systems with high pixel counts and fine resolution. (See below...) Figure 4 Another example of selectively applying a control voltage is shown in the figure.

[0050] Figure 3DThis is an illustration of a two-dimensional phase modulator 62, which includes two one-dimensional phase modulators 76 and 78. Each one-dimensional modulator is identical or similar to modulator 60, wherein the excitation electrode of modulator 76 is oriented in the Y direction, while the excitation electrode of modulator 78 is oriented in the X direction. The two one-dimensional modulators can be bonded together. Furthermore, they can be oriented "back-to-back" and share a common joint electrode, such as electrode 70.

[0051] The two-dimensional phase modulator 62 can be used as the phase modulator 54 of the lens 22. Figure 2 When using a birefringent liquid crystal, lens 22 may include a polarizer, as known in the art (omitted from the figures for simplicity), to select the polarization of light that will pass through and be refracted by the liquid crystal layer of phase modulator 62. When phase modulator 62 is used within glasses 20 as described above, corresponding control circuitry (such as circuitry 74 of modulator 60) is coupled to control circuitry 26 of the glasses for receiving control voltage waveforms.

[0052] As further described in the aforementioned U.S. Patent Application Publication 2022 / 0214566, the phase modulator 54 may include four optical phase modulators (not shown) that combine phase modulation in two orthogonal directions with two orthogonal polarizations in each direction.

[0053] In alternative embodiments, other types of phase modulators may be used for lens 22, such as the two-dimensional phase modulators shown in Figures 3A-3D of U.S. Patent 10,036,901, or modulators with circular electrodes.

[0054] Figure 4 This is a schematic front view of an electrically tunable lens 22 for myopia control according to an embodiment of the present invention. In this embodiment, the modulator 54 may include, for example, a two-dimensional phase modulator 62. Figure 3D ).

[0055] like Figure 1 As shown, lens 22 is mounted in frame 25; only the portion of the frame surrounding the lens is shown. The two orthogonal one-dimensional modulators 76 and 78 of modulator 62 include a vertical excitation electrode 82 and a horizontal excitation electrode 84, respectively. For myopia control, only the peripheral group of electrodes 82 and 84, i.e., those electrodes that do not pass through the central region 118 of the lens, is excited (a control voltage is applied) by control circuit 26, while the central group of electrodes, i.e., those electrodes that pass through the central region, is not excited. For clarity, in Figure 4 The arrangement is presented by showing only the excited electrodes. The selective excitation of electrodes 82 and 84 divides lens 22 into nine regions based on the type of phase modulation: - In regions 102 and 104 where only the vertical (Y) electrode 82 is excited, the phase is modulated in the horizontal (X) direction; - In regions 106 and 108 where only the horizontal (X) electrode 84 is excited, the phase is modulated in the vertical (Y) direction; - In regions 110, 112, 114 and 116 where both the X and Y electrodes are excited, the phase is modulated in both the X and Y directions; - In region 118 where no electrodes are excited, there is no phase modulation.

[0056] Therefore, regions 102-116 disturb the light incident on lens 22 and define the disturbed peripheral region 39. Figure 1 Region 118 allows for clear vision and defines the central region 37. By selecting a larger or smaller set of electrodes 82 and 84 for excitation, the control circuit 26 can decrease or increase the size of the central region 118 (and can do so alternately between the left and right eyes as described above).

[0057] By stimulating other groups of the X and / or Y electrodes, the central region 37 (i.e., region 118) can be laterally displaced on the lens 22. In glasses 20 including an optional eye tracker 30, signals from the eye tracker can be used to control the lateral displacement of the central region 37 (as described above).

[0058] Segmented Electrode In some cases, it may be desirable to segment the excitation electrodes of an electrically tunable lens, as described in U.S. Patent 10,466,391 above. The control strategies described below can be used to modify the phase distribution of the lens in a flexible manner. For example, the refractive power in the central region can be adjusted according to the refractive correction required by the user's eye, while perturbations in the peripheral region can be selected to achieve maximum therapeutic efficacy.

[0059] Figure 5 This is a schematic side view of the segmented excitation electrode 202 of the optical phase modulator 200 according to an embodiment of the present invention.

[0060] The excitation electrode array 201 includes parallel conductive strips 204 that extend above the active region of the electro-optic layer (e.g., liquid crystal) along respective mutually parallel axes across the transparent substrate 203. The segmented electrodes 202 divide each strip 204 into segments labeled R1, R2, ..., R... i R i+1 ..., R n The array is formed by groups of n segments, where n and i are integers, 1 ≤ i ≤ n. For myopia control, an appropriate control voltage waveform is applied to segments in the peripheral portion of the array 201 to perturb vision, while segments in the central portion of the array allow clear vision. As in the previous embodiment, the perturbation is applied alternately between the left and right eyes.

[0061] Segment 202 can be located on a Cartesian grid with a grid spacing of 1 mm in both the X and Y directions. Alternatively, other (non-Cartesian) grid arrangements and other grid spacings can be used. To achieve good optical quality of the phase modulator 200, the gaps between segments 202 are typically much smaller than the length of the segment itself. (As in...) Figure 5 In the example shown, segments can all have similar lengths, or different segments can have different lengths within each strip and between different strips.

[0062] Figure 6 This is a schematic side view of a phase modulator 200 according to an embodiment of the present invention, showing the electrical control of the segmented electrode 202.

[0063] Section 202 passes through sections marked G1, G2, ..., G i ... G n-1 The switches 206 (e.g., suitable thin-film transistors) are interconnected in series. The integer n has a connection with... Figure 5 The same value is assigned to each of the following: 1 ≤ i ≤ n-1. Control lines 208 are connected to actuate the corresponding switch rows 206 on all strips, wherein a single control line is connected to each switch G on all strips. i By actuating the appropriate control line, control circuit 26 ( Figure 1 Therefore, it is possible to simultaneously connect each segment 202 to its adjacent segments or disconnect it from its adjacent segments in all strips.

[0064] As detailed in U.S. Patent 10,466,391, control circuitry 26 is typically connected to apply a control voltage waveform to one or both ends of each conductive strip 204, for example, to segment group R1, and possibly to segment group R within each strip. n To apply different, corresponding control voltage waveforms to different groups of segments, the control circuit can actuate appropriate switches 206 and modify the control voltage waveforms applied to the corresponding ends of the conductive strip 204. To enlarge or reduce the size of the sharp central region of the lens, different switches 206 are turned on and off to activate or deactivate disturbances imposed by segments 202 in the central region.

[0065] Phase modulator 200 can be used as a two-dimensional phase modulator 54 for lens 22. Figure 2 In an alternative embodiment, two such phase modulators connected in series and rotated 90 degrees relative to each other about an axis perpendicular to the modulator plane can advantageously increase the flexibility of phase modulation of lens 22.

[0066] Myopia control program Figure 7A and Figure 7BThis is a schematic front view of the left lens 22 and right lens 24 of the eyeglasses 20 according to an embodiment of the present invention during two corresponding time periods.

[0067] Figure 7A The left lens 22 and right lens 24 are shown during the time period ΔT1. During this time period, the phase modulator 54 of lens 22 is driven by control circuit 26, such that the lens has a square central region 302 with a lateral dimension D and a peripheral region 304 with a phase distribution simulating the effect of an array of microlenses 306, while the right lens 24 has a central region 308 that fills the entire lens, meaning the right lens has no peripheral perturbation. The central region 302 has no phase modulation or phase modulation that provides the refractive power for correcting the user's left eye vision. Therefore, the user can see external objects clearly through the central region 302. The microlenses 306 have a different refractive power than the central region 302, such as positive refractive power, thus perturbing the peripheral visual field of the left eye. For the purpose of myopia control, this perturbation blurs the vision in the peripheral visual field and / or reduces the contrast of the viewed object.

[0068] Figure 7B The left lens 22 and right lens 24 are shown during the time period △T2 following time period △T1. During time period △T2, control circuit 26 is in conjunction with... Figure 7A The phase modulation of lenses 22 and 24 is opposite to the phase modulation of lenses 24: lens 22 has an unmodulated (clear) central region 310 that fills the entire lens, while lens 24 has a square central region 312 with a lateral dimension of D and a peripheral region 314 that simulates an array of microlenses 306.

[0069] The control circuit 26 continuously and alternately switches between time periods △T1 and △T2. Figure 7A and Figure 7B The switching between states can occur every few minutes to every few hours (minutes ≤ ΔT1, ΔT2 ≤ hours), but can also occur at a rate as fast as 10 Hz, or as slow as once a day (0.1 seconds ≤ ΔT1, ΔT2 ≤ 1 day), or at an intermediate rate, such as once per minute to once every 4 hours (1 minute ≤ ΔT1, ΔT2 ≤ 4 hours). The time periods ΔT1 and ΔT2 can have equal or different lengths, the length of which can be determined based on treatment considerations.

[0070] Peripheral vision is highly sensitive to detecting sudden changes in motion in the real world. When switching between states at a rate below 0.2 Hz (5 seconds ≤ ΔT1, ΔT2), the switching itself can be gradual so as not to trigger motion detection in the user's peripheral field of view. Gradual switching is achieved by including a gradual transition between two time intervals ΔT1, ΔT2, where the length of the gradual transition is typically greater than 5 seconds.

[0071] In the illustrated embodiment, central regions 302 and 312 are squares with the same lateral dimension D. In alternative embodiments, the central regions may have a rectangular shape or some other shape within the constraints of the structure and driving strategy of the excitation electrodes. A typical lateral dimension of the central region (within the peripheral region) can be 8 mm, although smaller or larger lateral dimensions can be used. For example, the lateral dimension D can be less than 2 mm, or even zero, in which case the peripheral region fills the entire optical element, i.e., the entire optical element is perturbed. The lateral dimensions can also be different for the left lens 22 and the right lens 24. Furthermore, instead of the central region filling the entire lens, for example, for central region 308 in time period ΔT1, this central region can be larger than central region 302, but still surrounded by the perturbed peripheral region. This embodiment is described below. Figures 8A-8C Further examples will be provided.

[0072] While in the illustrated embodiment, the perturbations in peripheral regions 304 and 314 are implemented by simulating an array of microlenses 306, other types of perturbations can be applied in alternative embodiments. For example, the peripheral regions can be driven to apply continuous positive refractive power or random phase modulation. The optical characteristics of the perturbation phase modulation can be adjusted to different perturbation intensities between the left and right eyes, where "different perturbation intensities" means different defocusing forces or random phases resulting in different amounts of blur and / or contrast loss.

[0073] In the illustrated embodiment, central regions 302 and 312 are located at the centers of the respective lenses 22 and 24. In an alternative embodiment, central regions 302 and 312 may be based, for example, on data from sensor 30 (…). Figure 1 The input is shifted laterally from the center position.

[0074] Figure 8A , Figure 8B and Figure 8C This is a schematic front view of the left lens 22 and right lens 24 of the eyeglasses 20 according to another embodiment of the present invention in three corresponding time periods.

[0075] The control circuit 26 alternately cycles the left lens 22 and the right lens 24 through three configurations during consecutive time periods ΔT3, ΔT4 and ΔT5, the parameters of which are summarized in Table 1 below.

[0076] Table 1: Configuration of lenses 22 and 24

[0077] All peripheral regions 406, 410, 414, 418, 422, and 426 simulate an array of microlenses 404, similar to... Figures 7A-7BThe microlens 306 is shown in Table 1. The lateral dimensions D1, D2, and D3 of the central region can be, for example, D1 = 8 mm, D2 = 16 mm, and D3 = 12 mm. In alternative embodiments, other dimensions may be used.

[0078] Time periods △T3, △T4, and △T5 have similar characteristics Figures 7A-7B The values ​​of △T1 and △T2 in the equation.

[0079] Adjustable lens distribution for myopia control The following figures illustrate the optical distribution of refractive power and phase shift of the electrically tunable phase modulator 54 as a function of position along a line passing through the lens (e.g., along the horizontal (X) axis, through the central region 37 and the peripheral region 39). Alternatively, similar distributions can be generated in other types of electrically tunable lenses.

[0080] For the purpose of myopia control, it is assumed in these examples that the central region 37 has a lateral dimension of 4 mm, although a larger or smaller dimension can be used. For example, the control circuit 26 can increase or decrease the size of the central region 37 based on the pupil size measured by the eye tracker 30 or based on ambient light. As in the previous embodiments, the size of the central region 37 alternately increases and decreases between the left and right eyes. The perturbation applied to the peripheral region 39 can also vary between the eyes.

[0081] Figure 9A According to an embodiment of the present invention, the electrically tunable optical phase modulator 54 of lens 22 ( Figure 2 A schematic curve 502 illustrates how the refractive power (in diopters) of the lens changes with its position on the lens. In this example, it is assumed that the baseline refractive power provided by the fixed lenses 52 and 56 is equal to the refractive correction required by the user, for example, -2D (two diopters, negative sign). Therefore, control circuit 26 drives phase modulator 54 to apply no additional refractive power in the central region 37. In the peripheral region 39, phase modulator 54 applies an additional +1D refractive power, resulting in a net refractive power of -1D for lens 22. Other, stronger refractive powers can also be used. The reduction in refractive power in the peripheral region and the accompanying peripheral visual blur can be used for myopia control.

[0082] Figure 9B This is a schematic curve 504 illustrating the variation of the phase modulation distribution (in arbitrary units of phase (AU)) applied by the phase modulator 54 with the position on the lens 22 according to an embodiment of the present invention. In this case, the phase modulation distribution represented by curve 504 varies continuously in the horizontal direction over the peripheral region 39 relative to the line of sight located at the origin X=0. A similar distribution can be applied in the vertical direction.

[0083] Figure 9CThis is a schematic curve 506 illustrating the variation of the phase modulation distribution applied by the phase modulator 54 with position on the lens 22 according to another embodiment of the invention. In this case, the phase modulation distribution comprises a pattern of alternating peaks and valleys in the peripheral region 39 in the lateral direction relative to the site line. The pattern is chosen such that the phase modulation distribution simulates a Fresnel lens. A Fresnel lens achieves the same refractive power (+1D) as the smooth distribution of curve 504, but with a lower maximum phase shift. Therefore, the use of a Fresnel distribution, in contrast to a smooth distribution, allows for the use of a thinner electro-optic layer in the phase modulator 54, and a lower voltage when driving the phase modulator.

[0084] In order to move the central region 37, for example, along the X-axis toward the negative X value, curves 502, 504, and 506 are moved accordingly.

[0085] Figure 10 This is a schematic curve 602 illustrating the change in phase modulation distribution applied by phase modulator 54 with position on the lens, according to another embodiment of the invention. Here, the phase shift is also plotted in arbitrary units. The phase modulation distribution of curve 602 includes a pattern of alternating peaks and valleys simulating the microlens array in the peripheral region 39. For example, the refractive power of each microlens can be between +1D and +8D.

[0086] Figure 11 This is a schematic curve 702 illustrating the change in phase modulation distribution applied by phase modulator 54 with position on the lens, according to another embodiment of the invention. The phase shift is plotted in arbitrary units. The phase modulation distribution of curve 702 includes a pseudo-random phase pattern for blurring and / or reducing the contrast of peripheral vision.

[0087] It should be understood that the above embodiments are cited by way of example, and the present invention is not limited to what has been specifically shown and described above. More precisely, the scope of the present invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications of these features that would occur to those skilled in the art after reading the foregoing description and that are not disclosed in the prior art.

Claims

1. A pair of glasses for treating myopia, comprising: Eyeglass frames; A first optical element and a second optical element, having a controllable optical phase distribution and mounted in the eyeglass frame, such that when the user wears the eyeglasses, the first optical element and the second optical element are positioned in the corresponding lines of sight of the user's left and right eyes; and A control circuit configured to control the optical phase distribution of the first optical element and the second optical element to apply optical perturbations to light incident on the left and right eyes through the respective peripheral regions of the first optical element and the second optical element at time intervals between the first optical element and the second optical element.

2. The eyeglasses according to claim 1, wherein, The optical disturbance causes the image seen by the eye through the peripheral region to become blurred.

3. The eyeglasses according to claim 2, wherein, The optical perturbation includes refractive forces selected to defocus the image formed on the retina of the eye.

4. The eyeglasses according to claim 3, wherein, The refractive power is positive.

5. The eyeglasses according to claim 1, wherein, The optical perturbation reduces the contrast of the image seen by the eye through the peripheral region.

6. The eyeglasses according to any one of claims 1-5, wherein, The control circuit is configured to control the optical phase distribution so that, while the optical perturbation is alternately applied in the peripheral region, the left and right eyes can achieve clear vision through the respective central areas of both the first and second optical elements.

7. The eyeglasses according to claim 6, wherein, The corresponding central area has a fixed lateral dimension.

8. The eyeglasses according to claim 6, wherein, The corresponding central area has a variable lateral dimension.

9. The eyeglasses according to claim 8, wherein, The optical phase distribution is controlled such that while the optical perturbation is applied alternately to the peripheral region at the stated time, the corresponding central regions of the first optical element and the second optical element have the same lateral dimension.

10. The eyeglasses according to claim 8, wherein, The control circuit is configured to alternately change the lateral dimensions of the corresponding central areas of the first and second optical elements in conjunction with the time alternation of optical disturbances in the peripheral region.

11. The eyeglasses according to claim 6, wherein, The control circuit is configured to change the lateral dimensions of the respective central regions of the first and second optical elements between at least three different values.

12. The eyeglasses according to claim 6, wherein, The central area of ​​the clear vision has a lateral dimension of at least 8 mm.

13. The eyeglasses according to claim 6, wherein, The control circuit is configured to control the optical phase distribution such that when the optical disturbance is applied to the peripheral region of one of the optical elements, the other of the optical elements provides clear vision in both the central and peripheral regions.

14. The eyeglasses according to claim 6, wherein, The central area of ​​the clear vision has a lateral dimension of less than 2 mm.

15. The eyeglasses according to claim 6, wherein, The control circuit is configured to control the optical phase distribution in order to apply myopia correction in the central area.

16. The eyeglasses according to any one of claims 1-5, wherein, The control circuit is configured to control the optical phase distribution such that the optical disturbance alternates at a time alternation rate between 10 Hz and once per day.

17. The eyeglasses according to claim 16, wherein, The control circuit is configured to control the optical phase distribution such that the period of time alternation of the optical disturbance is between one minute and four hours.

18. The eyeglasses according to any one of claims 1-5, wherein, The time alternation between the first optical element and the second optical element includes a gradual transition of the disturbance in the respective peripheral regions.

19. The eyeglasses according to claim 18, wherein, The gradual transition has a duration of at least 5 seconds.

20. The eyeglasses according to any one of claims 1-5, wherein, The control unit is configured to apply the optical disturbance to the first optical element and the second optical element at different corresponding time periods.

21. The eyeglasses according to any one of claims 1-5, wherein, The control unit is configured to apply the optical disturbance to the first optical element and the second optical element with different corresponding disturbance intensities.

22. The eyeglasses according to any one of claims 1-5, wherein, The first optical element and the second optical element include a compound lens, each compound lens including a corresponding fixed lens component having a predetermined refractive power and a corresponding optical phase modulator configured to apply the optical perturbation under the control of the control circuit.

23. The eyeglasses according to any one of claims 1-5, further comprising at least one sensor, said at least one sensor being configured to output a signal indicating operating conditions of the eyeglasses, wherein, The control circuit is configured to modify the optical phase distribution in response to the signal.

24. The eyeglasses according to claim 23, wherein, The signal indicates the distance to the object being viewed by the user.

25. The eyeglasses according to claim 23, wherein, The signal indicates the user's gaze direction.

26. The eyeglasses according to claim 23, wherein, The signal indicates the level of ambient light, and the control circuit is configured to adjust the size of the clear central region of the optical element in response to the level of ambient light.

27. A method for treating myopia, comprising applying an optical perturbation to light incident peripherally on a user's left and right eyes, such that the optical perturbation is applied alternately between the left and right eyes over time.

28. The method according to claim 27, wherein, Applying the optical perturbation includes blurring the image seen by the eye in the peripheral region of vision.

29. The method according to claim 28, wherein, Applying the optical perturbation includes applying a refractive force selected to defocus an image seen by the eye in the peripheral region of vision.

30. The method according to claim 29, wherein, The refractive power is positive.

31. The method according to claim 27, wherein, Applying the optical perturbation involves reducing the contrast of the image as seen by the eye in the peripheral region of vision.

32. The method according to any one of claims 27-31, wherein, Applying the optical perturbation includes: while alternating the light incident on the left and right eyes at the periphery with the time, enabling the left and right eyes to achieve clear vision in the corresponding central areas of the user's left and right eyes.

33. The method according to claim 32, wherein, The corresponding central area has a fixed lateral dimension.

34. The method according to claim 32, wherein, The corresponding central area has a variable lateral dimension.

35. The method according to claim 34, wherein, Achieving the clear vision includes applying the optical perturbation to peripherally incident light at the time intervals while maintaining the same lateral size of the central area of ​​clear vision for the left and right eyes.

36. The method according to claim 34, wherein, Achieving the clear vision involves alternating the corresponding lateral dimension of the central region of the clear vision between the left and right eyes, together with the optical perturbation applied to the light incident on the periphery.

37. The method according to claim 32, wherein, Achieving the clear vision involves varying the lateral dimension of the central region of the clear vision among at least three different values.

38. The method according to claim 32, wherein, The central area of ​​the clear vision has a lateral dimension of at least 8 mm.

39. The method according to claim 32, wherein, Achieving the clear vision includes providing clear vision in both the central and peripheral areas of the other eye when the optical disturbance is peripherally applied to one eye.

40. The method according to claim 32, wherein, The central area of ​​the clear vision has a lateral dimension of less than 2 mm.

41. The method of claim 32, further comprising applying myopia correction to the central area of ​​the clear vision.

42. The method according to any one of claims 27-31, wherein, Applying the optical perturbation involves alternating the perturbation between the left and right eyes at a rate between 10 Hz and once per day.

43. The method according to claim 42, wherein, The time alternation period of the optical perturbation is between one minute and four hours.

44. The method according to any one of claims 27-31, wherein, The time alternation between the first optical element and the second optical element includes a gradual transition of the optical disturbance between the eyes.

45. The method according to claim 44, wherein, The gradual transition has a duration of at least 5 seconds.

46. ​​The method according to any one of claims 27-31, wherein, The optical disturbances were applied to the left and right eyes at different corresponding time periods.

47. The method according to any one of claims 27-31, wherein, The optical disturbances were applied to the left and right eyes with different corresponding disturbance intensities.

48. The method according to any one of claims 27-31, wherein, Applying the optical perturbation includes: positioning a first optical element and a second optical element having a controllable optical phase distribution in the respective lines of sight of the left and right eyes, and controlling the optical phase distribution to apply the optical perturbation.

49. The method according to claim 48, wherein, The first optical element and the second optical element include compound lenses, each compound lens including a corresponding fixed lens component having a predetermined refractive power and a corresponding optical phase modulator configured to alternately apply the optical perturbation at the said time.

50. The method according to any one of claims 27-31, further comprising sensing the operating conditions of the glasses and modifying the optical disturbance in response to the operating conditions.

51. The method according to claim 50, wherein, Sensing the operating conditions includes sensing the distance to an object being viewed by the user.

52. The method according to claim 50, wherein, Sensing the operating conditions includes sensing the user's gaze direction.

53. The method according to claim 50, wherein, Sensing the operating conditions includes sensing the level of ambient light, and wherein modifying the optical perturbation includes changing the lateral dimension of the central region of clear vision in response to the level of ambient light.

54. A pair of eyeglasses for treating myopia, comprising: - Eyeglass frames; - A first optical element and a second optical element, the first optical element and the second optical element being mounted in the eyeglass frame such that when the user wears the eyeglasses, the first optical element and the second optical element are positioned in the respective lines of sight of the user's left and right eyes, each of the first optical element and the second optical element comprising: -- At least one liquid crystal layer; and -- A conductive electrode extending over opposing first and second sides of the at least one liquid crystal layer, the electrode comprising an excitation electrode array including parallel conductive strips extending along respective mutually parallel axes across the first side of the at least one liquid crystal layer; and - A control circuit coupled to apply a corresponding control voltage waveform to excitation electrodes located in respective peripheral regions of the first optical element and the second optical element, so as to apply optical perturbations to light passing through the peripheral regions at time intervals between the first optical element and the second optical element.

55. The eyeglasses according to claim 54, wherein, In each of the first optical element and the second optical element, the at least one liquid crystal layer includes a first liquid crystal layer and a second liquid crystal layer arranged in series, and the conductive electrode includes a first set of parallel conductive strips extending over the first liquid crystal layer along a first direction and a second set of parallel conductive strips extending over the second liquid crystal layer along a second direction orthogonal to the first direction.

56. The eyeglasses according to claim 55, wherein, The control circuit is configured to apply the control voltage waveform to the respective outer groups of the parallel conductive strips in both the first set and the second set, thereby ensuring that the rectangular central region of each of the optical elements remains undisturbed.

57. The eyeglasses according to claim 56, wherein, The control circuit is configured to apply the control voltage waveform to the corresponding central group of parallel conductive strips in both the first set and the second set, so as to apply myopia correction in the rectangular central area.

58. The eyeglasses according to claim 54, wherein, The first optical element and the second optical element include a compound lens, each compound lens including a corresponding fixed lens component having a predetermined refractive power and the at least one liquid crystal layer.

59. The eyeglasses according to any one of claims 54-58, wherein, Each of the conductive strips is divided into two or more segments extending above corresponding, non-intersecting portions of the strip's axis, and the control circuit is coupled to apply the corresponding control voltage waveform to the corresponding peripheral segment of the excitation electrode in order to apply the optical perturbation.

60. The eyeglasses according to any one of claims 54-58, wherein, The control circuit is configured to apply the corresponding control voltage waveform, such that the optical phase distribution of the liquid crystal layer in the peripheral region simulates a microlens array.

61. The eyeglasses according to any one of claims 54-58, wherein, The control circuit is configured to apply the corresponding control voltage waveform, such that the optical phase distribution of the liquid crystal layer in the peripheral region simulates a positive lens.

62. The eyeglasses according to any one of claims 54-58, wherein, The control circuit is configured to apply the corresponding control voltage waveform, such that the optical phase distribution of the liquid crystal layer in the peripheral region simulates a Fresnel lens.

63. The eyeglasses according to any one of claims 54-58, wherein, The control circuit is configured to apply the corresponding control voltage waveform, causing the liquid crystal layer to apply a pseudo-random phase pattern in the peripheral region.

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