An optical lens to slow down the progression of vision impairment

Abstract

An optical lens to slow down the progression of vision impairment An optical lens intended to be worn in front of an eye of a wearer to correct a vision impairment and to slow down the progression of said vision impairment of an eye of a wearer, said ophthalmic optical lens having a substrate, a front surface and a back surface, said ophthalmic optical lens comprises a plurality of optical elements, wherein: at least one light ray passing through the optical lens over a pupil having at least a 4 mm diameter passes through at least one of the plurality of optical elements, wherein over the said pupil the optical lens produces a first optical path map (OPD1), a best atorical form fitting of the first optical path map (OPD1) produces a second optical path difference map (OPD2), a differential optical path map (DOP) being composed as the difference between said first optical path difference map (OPD1) and said second optical path difference map (OPD2), each optical element produces constant phase shifting so that the differential optical path map (DOP) is a piecewise constant surface of at least two levels and at least part of the at least two levels is spatially randomly distributed.

Description

[0001] An optical lens to slow down the progression of vision impairment

[0002] TECHNICAL FIELD

[0003] The disclosure relates to an optical lens intended to be worn in front of an eye of a wearer to correct a vision impairment and to slow down the progression of said vision impairment of an eye of a wearer, said optical lens comprises a plurality of optical elements, the disclosure also relates to a method of obtaining the optical lens according to the disclosure.

[0004] BACKGROUND OF THE DISCLOSURE

[0005] Myopia of an eye is characterized by the fact that the eye focuses distant objects in front of its retina. Myopia is usually corrected using a concave lens and hyperopia is usually corrected using a convex lens.

[0006] It has been observed that some individuals, in particular children, when corrected using conventional single vision optical lenses focus inaccurately when they observe an object which is situated at a short distance away, that is to say, in near vision conditions. Because of this focusing defect on the part of a myopic child which is corrected for his far vision, the image of an object close by is formed behind his retina, even in the foveal area.

[0007] Such focusing defects may have an impact on the progression of myopia of such individuals. One may observe that for most of said individuals the myopia defect tends to increase over time.

[0008] Recent controlled clinical trials provided evidence of the benefit of optical elements, such as microlenses or lenslets, in the peripheral visual field to slow down myopia progression. The purpose of the optical elements is to provide an optical blurred image on the retina of the wearer, triggering a stop signal to the eye’s growth. More generally, the purpose of the optical elements is to provide a myopia control signal, slowing down the eye growth.

[0009] The central area of the lens element having the optical elements may be free of optical elements, to enable a good and clear vision.

[0010] Recent studies also showed that myopia progression could be slowed down by providing a slight diffusion in the peripheral visual field, with arrays of small scattering dots. The basic principle of this solution is to decrease the contrast of retinal image in the peripheral visual field.

[0011] In the areas of the lens element comprising optical elements (like microlenses, or lenslets or dots of diffusion, or concentric rings of defocusing torus) the pattern formed by the optical element may show an alternance of two main areas: the “refractive areas” used to correct the myopia of the wearer, and the “defocus areas” used to control the myopia.

[0012] Different designs of optical elements have been designed with unifocal spherical lenslets, aspherical lenslets, “bifocal” lenslets, Pi-Fresnel lenslets, or even continuous torus, the optical elements may be contiguous or not.

[0013] Although the different proposed myopia control designs appear to provide some efficiency, there is a need to provide even more efficient myopia control solutions. In particular, there is a need for a well-controlled anti-progression of vision impairment signal, for example an anti-myopic signal, to the retina while maintaining a good visual acuity.

[0014] SUMMARY OF THE DISCLOSURE

[0015] To this end, the present disclosure proposes, an optical lens intended to be worn in front of an eye of a wearer to correct a vision impairment and to slow down the progression of said vision impairment of an eye of a wearer, said optical lens comprises a plurality of optical elements, wherein: at least one light ray passing through the optical lens over a pupil having at least a 4 mm diameter passes through at least one of the plurality of optical elements, over the said pupil the optical lens produces a first optical path map (OPD1), a best form fitting of the first optical path map (OPD1) produces a second optical path difference map (OPD2), a differential optical path map (DOP) being composed as the difference between said first optical path difference map (OPD1) and said second optical path difference map (OPD2), each optical element produces constant phase shifting so that the differential optical path map (DOP) is a piecewise constant surface of at least two levels, for example three, four or six levels, and at least part of the at least two levels is spatially randomly distributed. The optical lens according to the disclosure has a new design type using diffraction modelling. The optical lens according to the disclosure allows managing the wavefront phase, i.e. the scattering distribution function by designing at least two levels of diffractive optical elements.

[0016] Thanks to the piecewise constant surface, the optical elements provide constant phase shifting of light and thus, their combined effect provides an image with a reduced contrast at the retina level. Such phase shifts bring myopia control thanks to contrast reduction resulting from diffraction. Light travels different distances in the optical elements depending on the angle of incidence, yielding different phase shifts and thus different contrast behaviors. This makes it possible to reduce contrast in peripheral vision for myopia control, while preserving as much as possible central vision acuity.

[0017] Thanks to having at least part of the at least two levels spatially randomly distributed, any grating effect (like peak on the MTF) is avoided.

[0018] The optical elements may be transversely spatially randomly distributed across the lens surface, within a surface, for example a plane, that is substantially perpendicular to the axis perpendicular to the surface of the lens at the major reference point., meaning the distribution lies in a surface, for example a plane, that is substantially parallel to the front and rear faces of the lens, i.e., within the transverse plane of the lens structure.

[0019] The major reference point being the point on the front surface of the lens at which the dioptric power for the distance portion apply as defined in ISO 13666 : 1998 ; 5.15.

[0020] The transversal spatial random distribution of the optical elements occurs within a surface perpendicular to the general direction of light propagation, such that the variation of optical path length (DOP) introduced by the optical elements is primarily along the optical axis, while their distribution is lateral across the lens surface. This ensures that the optical phase modulation occurs transversely across the lens area used for vision, without imposing structured patterns visible from outside the lens.

[0021] Furthermore, the disclosure has numerous advantages. Simple manufacturing processes can be used to manufacture such optical lenses. Advantageously, such optical lens is compliant with antireflective coating steps or even hard coating, such that no special insert or mold is required to provide the above-mentioned patterns. According to further embodiments which can be considered alone or in combination:

[0022] - the optical lens is part of an eye wearer equipment and / or a head mounted device; and / or each optical element has a characteristic dimension greater than or equal to 1 pm and smaller than or equal to 250 pm; and / or at least one level of the differential optical path map (DOP) is close to zero, for example smaller than or equal to 10 nm, corresponding to the part of the optical lens without optical elements; and / or

[0023] - the at least two levels of the differential optical path map (DOP) are smaller than or equal to 1 pm, preferably, smaller than or equal to 700 nm; and / or

[0024] - the pupil has a diameter greater than or equal to 10 mm, for example greater than or equal to 20 mm; and / or

[0025] - the optical lens comprises an optical center and the center of the pupil is at distance smaller than or equal to 25 mm, for example smaller than or equal to 12 mm, for example smaller than or equal to 7 mm, from the optical center of the optical lens; and / or

[0026] - the density of optical elements over the pupil is greater than or equal to 10 % of the surface, for example greater than or equal to 20%, for example greater than or equal to 40% of the surface of the pupil; and / or

[0027] - the density of optical elements over the pupil is smaller than or equal to 95 % of the surface, for example smaller than or equal to 85%, for example smaller than or equal to 75% of the surface of the pupil; and / or

[0028] - the piecewise constant surface has two levels and the density of optical elements over the pupil is greater than or equal to 10 % of the surface and smaller than or equal to 50 % of the surface; and / or a modulation transfer function produced by the differential optical path map (DOP) is greater or equal to 0.07, preferably greater or equal to 0.10, over the range of spatial frequencies comprised from 10 to 25 cycles per degree, when measured through the pupil; and / or a modulation transfer function produced by the differential optical path map (DOP) has a cutoff frequency smaller than or equal to 8 cpd, for example smaller than or equal to 4cpd; and / or - the autocovariance of the differential optical path map (DOP) when calculated with a spatial shift corresponding to the characteristic dimension of the smallest optical element comprised in the pupil is greater than or equal to 0.4; and / or

[0029] - the autocovariance of the differential optical path map (DOP) when calculated with any spatial shift comprised between one and ten times the characteristic dimension of the smallest optical element comprised in the pupil is smaller than or equal to 0.8; and / or

[0030] - the autocovariance of the differential optical path map (DOP) between a shift corresponding to the characteristic dimension of the smallest optical element comprised in the pupil and a shift corresponding to the radius of the pupil is smaller than or equal to 0.75, for example smaller than or equal to 0.55; and / or

[0031] - the autocovariance of the differential optical path map (DOP) is greater than or equal to 0.4 when calculated with any shift greater than or equal to the characteristic dimension of the smallest optical element comprised in the pupil and smaller than or equal to the radius of the pupil; and / or

[0032] - the optical lens comprises a plurality of dots, each dot comprising a plurality of optical elements randomly distributed over the dots and the differential optical path map (DOP) is close to zero in the zone of the optical lens without dots; and / or

[0033] - the density of optical elements within each dot is greater than or equal to 20 % of the surface of the dot, for example greater than or equal to 30%, for example greater than or equal to 40%,

[0034] - the density of optical elements within each dot is smaller than or equal to 95%, for example smaller than or equal to 85%, for example smaller than or equal to 75%, of the surface of the dot; and / or

[0035] - the density of dots over the pupil is greater than or equal to 15 %, for example greater than or equal to 25%, for example greater than or equal to 35%, of the surface of the dot; and / or

[0036] - the density of dots over the pupil is smaller than or equal to 95%, for example smaller than or equal to 85%, for example smaller than or equal to 80% of the surface of the dot; and / or

[0037] - the dots are positioned according to a regular mesh; and / or

[0038] - the dots are spatially randomly distributed, wherein the dots are spatially randomly distributed; and / or each dot has a characteristic dimension greater than or equal to 150 pm for example greater than or equal to 200 pm, for example greater than or equal to 250 pm; and / or each dot has a characteristic dimension smaller than or equal to 400 pm, for example smaller than or equal to 350 pm, for example smaller than or equal to 300 pm; and / or

[0039] - the optical elements are positioned in a mesh, such as for instance a grid or a honeycomb; and / or

[0040] - at least 50%, for example at least 80%, for example at least 99%, of the optical elements are contiguous optical elements; and / or

[0041] - at least part, for example all, of the front and / or the back surface of the lens element is covered with a coating; and / or

[0042] - at least part, for example all, of the optical elements are located on the front surface of the lens element; and / or

[0043] - at least part, for example all, of the optical elements are located on the back surface of the lens element; and / or

[0044] - at least part, for example all, of the optical elements are located between the front and the back surfaces of the lens element; and / or

[0045] - said plurality of optical elements is obtained by photolithography; and / or

[0046] - said plurality of optical elements is obtained by using a mask having holes corresponding to said plurality of optical elements, depositing said optical elements in said holes and removing said mask; and / or

[0047] - said mask is a laser-cut sheet of metal; and / or

[0048] - said plurality of optical elements is made of a layer having a predetermined thickness deposited on a hardcoat of said optical lens; and / or

[0049] - said layer is deposited on said hardcoat by an inkjet process; and / or

[0050] - said optical lens is obtained from a semi-finished lens and said at least one optical element is arranged on or in said semi-finished lens;

[0051] - said optical lens is obtain using a molding process; and / or

[0052] - said optical elements are contained in an adhesive film; and / or

[0053] - the optical lens comprises a central zone free of optical elements; and / or

[0054] - the central zone free of optical elements is centered on an optical center and / or a geometrical center of the optical lens; and / or

[0055] - the central zone free of optical elements has a diameter greater than or equal to 2.5 mm, for example greater than or equal to 5.0 mm, more preferably greater than or equal to 7.5 mm, and smaller than or equal to 15 mm, for example smaller than or equal to 12 mm, for example smaller than or equal to 10 mm.

[0056] BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Non-limiting embodiments of the disclosure will now be described with reference to the accompanying drawing wherein:

[0058] - Figure 1 illustrates a schematic front view of an optical lens according to an embodiment of the disclosure;

[0059] - Figure 2 illustrates a close up view of the schematic front view of an optical lens according to an embodiment of the disclosure;

[0060] - Figure 3 illustrates a schematic profile view of a lens element according to an embodiment of the disclosure;

[0061] - Figures 4 to 6 illustrates graphs of MTF curves of an optical lens according to different embodiments of the disclosure;

[0062] - Figures 7a and 7b illustrate different embodiments of the disclosure; and

[0063] - Figures 8 illustrates graphs of MTF curves of the embodiments illustrated on figures 7a and 7b.

[0064] Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve the understanding of the embodiments of the present disclosure.

[0065] DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

[0066] The disclosure relates to a lens element intended to be worn by a wearer.

[0067] In the description, terms like « up », « bottom », « horizontal », « vertical », « above », « below », « front », « rear » or other words indicating relative position may be used. These terms are to be understood in the wearing conditions of the optical lens.

[0068] The disclosure relates to an optical lens intended to be worn in front of an eye of a wearer in specific wearing conditions, for example in standard viewing conditions.

[0069] In the context of the present disclosure, the term "optical lens" can refer to a contact lens or an optical lens or a spectacle optical lens edged to fit a specific spectacle frame or an ophthalmic lens or a progressive multifocal addition lens, or an optical device adapted to be positioned on the ophthalmic lens. The optical device may be positioned on the front or back surface of the ophthalmic lens. The optical device may be an optical patch or film. The optical device may be adapted to be removably positioned on the ophthalmic lens for example a clip configured to be clipped on a spectacle frame comprising the ophthalmic lens.

[0070] The wearing conditions are to be understood as the position of the optical lens with relation to the eye of a wearer, for example defined by a pantoscopic angle, a wrap angle, a Cornea to lens distance, and eventually any of a Pupil-cornea distance, a center of rotation of the eye (CRE) to pupil distance, or a CRE to lens distance.

[0071] The Cornea to lens distance is the distance along the visual axis of the eye in the primary position (usually taken to be the horizontal) between the cornea and the back surface of the lens; for example comprised between 8 and 16 mm, preferably 10 and 14 mm, more preferably equal to 12mm.

[0072] The Pupil-cornea distance is the distance along the visual axis of the eye between its pupil and cornea; usually comprised between 1 and 4 mm, for example equal to 2mm.

[0073] The CRE to pupil distance is the distance along the visual axis of the eye between its center of rotation (CRE) and cornea; for example comprised between 10 and 15 mm, preferably 11 and 12 mm, more preferably equal to 11.5mm.

[0074] The CRE to lens distance is the distance along the visual axis of the eye in the primary position (usually taken to be the horizontal) between the CRE of the eye and the back surface of the lens, for example comprised between 20 and 30 mm, preferably 22.5 and 28 mm, more preferably equal to 25.5mm.

[0075] The pantoscopic angle is the angle in the vertical plane, at the intersection between the back surface of the lens and the visual axis of the eye in the primary position (usually taken to be the horizontal), between the normal to the back surface of the lens and the visual axis of the eye in the primary position; for example comprised between -25° and +5°, preferably -12° and 0°, more preferably between -10° and -6°, for example equal to -8°, preferably equal to 0°.

[0076] The wrap angle is the angle in the horizontal plane, at the intersection between the back surface of the lens and the visual axis of the eye in the primary position (usually taken to be the horizontal), between the normal to the back surface of the lens and the visual axis of the eye in the primary position for example comprised between -10° and +25°, preferably 0° and 10°, more preferably between 0° and +5°, for example equal to 0°. An example of standard wearing condition may be defined by a pantoscopic angle of -8°, a Cornea to lens distance of 12 mm, a Pupil-cornea distance of 2 mm, a CRE to pupil distance of 11.5 mm, a CRE to lens distance of 25.5 mm and a wrap angle of 0°.

[0077] Another example of standard wearing condition more adapted for younger wearers may be defined by a pantoscopic angle of 0°, a Cornea to lens distance of 12 mm, a Pupil-cornea distance of 2 mm, a CRE to pupil distance of 11.5 mm, a CRE to lens distance of 25.5 mm and a wrap angle of 0°.

[0078] The optical lens may be adapted for a wearer, to correct a vision impairment and to slow down the progression of said vision impairment of the eye of the wearer. In the following disclosure, the vision impairment will be considered to be a myopia of an eye of the wearer. However, the present disclosure is not limited to myopia. In particular, the person skilled in the art will be able to adapt the present disclosure to other kind of vision impairment such as hyperopia, astigmatism among others.

[0079] The optical lens is adapted for a wearer according to a prescription to restore a person’s ability to see clearly, especially at distance vision for myopes.

[0080] The term “prescription” is to be understood to mean a set of optical characteristic of optical power, of astigmatism, of prismatic deviation, determined by an ophthalmologist or optometrist in order to correct the vision defects of the eye, for example by means of a lens positioned in front of his eye. For example, the prescription for a myopic eye comprises the values of optical power and of astigmatism with an axis for the distance vision. The prescription may comprise an indication that the eye of the wearer has no defect and that no refractive power is to be provided to the wearer.

[0081] The prescription in ophthalmic field may comprise, in addition to the power prescription, an astigmatism prescription. Such a prescription is composed of an axis value (in degrees) and a module value (in diopters). The module value represents the difference between the maximal and minimal power in a given direction allowing to correct the visual default of a wearer. Following the convention, the axis represents the orientation of one of the two powers versus a reference axis and following a given rotation direction. TABO convention may be used. In this convention the reference axis is horizontal and the rotation direction is counterclockwise when looking at the wearer. A 45° axis corresponds to an axis orientated obliquely linking, when looking at the wearer, the upper right quadrant to the lower left quadrant. Such an astigmatism prescription is measured for the wearer in far vision. The term 'astigmatism' is used to refer to the couple (module, axis). That term is sometimes used to simply designate the module. The skilled person easily understands what it refers to depending on the context. The skilled person is also aware that the power / astigmatism prescription for a wearer is commonly described with the terms sphere, cylinder and axis.

[0082] As represented in figures 3, an optical lens 10 according to the disclosure comprises a substrate 12. The substrate 12 comprises at least a first surface and a second surface opposed to the first surface. For example, the first surface may comprise an object side surface Fl formed as a convex curved surface toward an object side and the second surface may comprise an eye side surface F2 formed as a concave surface. Alternatively, the object side surface Fl and / or the eye side surface F2 may be any one of a piano surface, a convex surface, or a concave surface.

[0083] The optical lens 10 may be made of any suitable material such as organic material, for example polycarbonate, plastic, resin, or mineral material such as glass.

[0084] The eye side surface Fl and / or the object side surface F2 of the substrate 12 may have any suitable shape, such as spherical or non-spherical. The term "spherical shape" refers to the curvature of the lens surface, which closely follows the shape of a perfect or almost perfect sphere. A spherical surface has a substantially uniform curvature over the entire surface of the lens element, which remains substantially the same in all meridians. A non-spherical surface should be understood as not being uniform over the entire surface of the lens element, with different curvatures in different meridians.

[0085] The eye side surface Fl and / or the object side surface F2 of the substrate 12 may have a toric shape. A toric surface has two principal meridians that are perpendicular to each other, often referred to as the "steep" and "flat" meridians. The curvature of the surface in these meridians is different.

[0086] The eye side surface Fl and / or the object side surface F2 of the substrate 12 may have an aspherical shape. An aspherical surface has a curvature that progressively varies over the surface of the lens element. The curvature along different meridians varies from the geometrical center of the lens element towards the periphery, for example, the curvature of the surface increases or decreases towards the peripheral part of the surface. The shape of an aspherical surface is typically described using a mathematical equation, such as a conic section or a polynomial equation.

[0087] The eye side surface Fl and / or the object side surface F2 of the substrate 12 may have progressive addition lens profile. In the sense of the disclosure, a “progressive addition lens profile surface” should be understood as a surface comprising two areas having different spherical surface, and a third areas joining the two first areas, along which the curvature value of the surface transitions from the first the second curvature values of the corresponding two areas.

[0088] Alternatively, the eye side surface Fl and / or the object side surface F2 of the substrate 12 may have a piano shape. A piano surface has no curvature over the entire surface of the lens element.

[0089] At least one part, preferably all, of a surface of the optical lens 10 may be covered by at least one layer of coating element. The at least one layer of coating element may comprise features selected from the group consisting of anti-scratch, antireflection, anti-smudge, anti-dust, UV30 filtration, blue light-filtration, anti-abrasion features.

[0090] As illustrated in figures 1 to 3, the optical lens 10 comprises a plurality of optical elements 14, for example at least twenty optical elements, for example at least a hundred of optical elements, for example at least five hundred optical elements.

[0091] As illustrated in figure 3 A, at least part, for example at least 50%, for example at least 80%, for example at least 95%, for example all of the optical elements 14 may be superimposed on the optical lens 10. In the sense of the disclosure, the expression “superimposed” should be understood as located on the front surface Fl of the substrate 12 of the optical lens 10 and / or on the back surface F2 of the substrate 12 of the optical lens 10, and / or in between the front and back surfaces of the optical lens.

[0092] As illustrated in figure 3B, at least part, for example at least 50%, for example at least 80%, for example at least 95%, for example of the optical elements 14 may be encapsulated between the front and back surfaces of the substrate 12 of the optical lens 10. For example, the optical lens 10 may be formed by at least two sub-lens elements having complementary surfaces designed to fit precisely into the other to ensure a tight and secure fit when the two sub-lens elements are brought and bonded together. The optical elements 14 may be disposed on any of the two complementary surfaces so that when the sub-lens are bonded together, the optical elements are encapsulated between them. The at least two sub-lens elements are made of material having different indices of refraction.

[0093] According to one embodiment, the encapsulation involves two optically transparent materials of optical quality, selected such that their refractive indices differ by at least 0.1 (subject to confirmation by the inventors). This refractive index contrast enables the generation of a stable optical path difference (DOP) at their interface. Suitable materials may include polycarbonate (PC), polymethyl methacrylate (PMMA), Durabio (a bio-based polycarbonate resin), and Trivex (a high-performance optical polymer known for its lightweight and impact resistance).

[0094] For example, in addition to PC / PMMA, other examples of encapsulation material pairs include polycarbonate (PC) and Durabio, or polycarbonate (PC) and Trivex. These combinations offer distinct refractive index contrasts and mechanical properties suitable for generating stable DOP interfaces.

[0095] For example, three layers of TiCh, two or three layers of ZrCh, one or two layers of SiCh or AhOs. ^etc. The materials of the substrate and the encapsulating medium may be identical or different, such as polycarbonate (PC) and polymethyl methacrylate (PMMA), polycarbonate and Durabio, or polycarbonate and Trivex. These combinations are selected for their suitable refractive index contrast and mechanical compatibility. The difference or match in refractive indices between the stack and the surrounding medium creates a controlled phase shift, for example greater than or equal to 145° and smaller than or equal to 180°, for a given wavelength, e.g., 550 nm.

[0096] Advantageously, having the optical elements encapsulated within the optical lens allows having an optical lens having a smooth back or eye side surface Fl and / or a front or object side surface F2.

[0097] According to an embodiment, the optical elements are produced by an anti- reflective (AR) coating designed to generate a phase shift, and this coating can be encapsulated within the lens material. The phase shift may be greater than or equal to 145° and smaller than or equal to 180° for a given wavelength, for example 550 nm. The encapsulation medium and the substrate may have identical or different refractive indices, and may be made of polymer materials such as polycarbonate (PC) or polymethyl methacrylate (PMMA). The interface between these materials provides minimal reflection, preferably less than or equal to 0.1%, ensuring invisibility of the optical elements once encapsulated.

[0098] In one embodiment, the optical elements are formed from a structured anti- reflective (AR) coating applied onto a substrate. The AR coating comprises a multilayer stack, for example three layers of TiCh, two layers of ZrCh and two layers of AI2O3. The coating may be patterned through a mask to form random-dot distributions. The coating may then be encapsulated between two sub-lens elements to preserve the integrity of the optical elements and improve mechanical resistance, especially abrasion resistance. The resulting structure provides constant phase shifting at the designed wavelengths. According to an embodiment, the encapsulated optical elements comprise anti- reflective coatings deposited in the form of multiple layers, for example three layers of TiCh, two or three layers of ZrCh, one or two layers of SiCh or AI2O3. The stack of layers is deposited on a substrate and embedded in a polymer medium such as polycarbonate (PC) or polymethyl methacrylate (PMMA). The materials of the substrate and the encapsulating medium may be identical or different. The difference or match in refractive indices between the stack and the surrounding medium creates a controlled phase shift, for example greater than or equal to 145° and smaller than or equal to 180°, for a given wavelength, for example 550 nm. Preferably, the reflectance at the interface of the encapsulated stack is smaller than or equal to 0.2%, more preferably smaller than or equal to 0.1%, ensuring that the structure is almost invisible once encapsulated.

[0099] According to an embodiment, the encapsulation process comprises depositing the optical elements in the form of a patterned AR coating using deposition techniques such as vacuum deposition, inkjet printing, or stamp printing. A removable mask may be used to define the pattern of optical elements. After deposition, the mask is removed, and the coated substrate is encapsulated with a second polymer layer. This ensures the micro / nano structures are embedded within the lens volume, offering protection from mechanical stress while preserving their optical functionality.

[0100] The encapsulated AR coating approach requires only one AR stack to be deposited selectively, either in the random-dot areas or on the full surface excluding those areas. The encapsulated zones with different phase shifts create the required optical path difference. The simplicity of this configuration reduces processing steps compared to dual-AR stack systems and avoids optical interference in non-pattemed regions due to material matching.

[0101] According to another embodiment, the optical lens is manufactured from a semi-finished lens substrate. A removable mask defining the location of optical elements is applied to the surface using a deposition method such as inkjet printing, stamp transfer or lithographic patterning. An anti-reflective coating stack is deposited layer-by-layer through vacuum deposition. After deposition, the mask is removed using a solvent, such as isopropanol or methoxyl propanol. The substrate carrying the patterned coating is then encapsulated by injection molding or casting with a second layer of polymer material, for example polycarbonate. The remaining manufacturing steps such as surfacing and hard multicoating are compatible with standard lens production methods. According to another embodiment, the encapsulation of the optical elements may use a configuration where only one anti -reflective coating stack is applied. The said coating may be deposited solely in the dot areas of the lens, or conversely, on the full surface of the lens except for the dots. In the uncoated regions, optical neutrality is preserved by matching the substrate and encapsulation material refractive indices, for example using PC / PC or PC / PMMA combinations, resulting in a reflectance lower than or equal to 0.1%. This approach reduces process complexity compared to configurations requiring two different coating stacks and ensures optical consistency across the full surface.

[0102] In the sense of the present disclosure, the term “smooth” may refer to a state of surface of an optical lens in which the roughness of said surface is smaller than or equal to lOnm, for example smaller than or equal to 4nm. The term “roughness of a surface” refers to the average of height deviations from the best form, for example best sphere, best asphere, or best atoric surface. The currently used standard for surface roughness is ISO 10110-8, which defines how surface roughness should be analyzed and specified. The term “most approximate sphere” is a spherical shape calculated from a measured value (height) of the surface for example on a pupil, using the least squares method. From the viewpoint of the average surface power, the term “smooth” may be defined as follows. The term “smooth” refers to the state of a surface whose rate of change in the average surface power (unit: D) at a given position of the surface in a given direction is smaller than or equal to 0.5 D / mm, for example smaller than or equal to 0.4 D / mm.

[0103] The term “smooth” may be defined as a state in which the difference between the minimum value and the maximum value of the average surface power is smaller than the difference (the power added by the filled segments) between the minimum value and the maximum value of the transmission power, for example measured at 550nm.

[0104] The optical elements 14 are designed to provide a constant phase shift of light which reduces the contrast of images formed at the retina level, at least for specific ranges of wavelengths. Advantageously, the image contrast reduction allows slowing down the progression of the visual impairment of the eye of the wearer.

[0105] Each optical element produces constant phase shifting so that the differential optical path map (DOP) is a piecewise constant surface of at least two levels, wherein at least part of the at least two levels is spatially randomly distributed transversely — that is, within a plane orthogonal to the direction of light propagation (typically the XY-plane, with light propagating along the Z-axis. According to a preferred embodiment, the differential optical path is created not by surface relief but by an internal interface between two materials with different refractive indices. This interface is formed within the volume of the lens, while both external faces of the lens remain smooth. Such a structure provides the desired phase modulation while maintaining surface polish, compatibility with coatings, and aesthetic neutrality.

[0106] As illustrated in figures 1 and 2, the plurality of optical elements is spatially randomly distributed.

[0107] As illustrated in figure 1, the optical lens 10 may comprise a central zone free of optical elements. The central zone is preferably centered on an optical center and / or a geometrical center of the optical lens. The central zone free of optical elements may have a diameter greater than or equal to 2.5 mm, for example greater than or equal to 5.0 mm, more preferably greater than or equal to 7.5 mm, and smaller than or equal to

[0108] 15 mm, for example smaller than or equal to 12 mm, for example smaller than or equal to 10 mm.

[0109] As illustrated in figures 1 and 2, one can define a pupil area 16 having a diameter equal to or greater than 4.0 mm. It should be understood that the pupil area

[0110] 16 does not correspond to a physical structure of the optical lens but serves as a tool for defining a zone of the optical lens over which measurements can be performed.

[0111] Although the disclosure is described in detailed with a pupil area having a diameter of 4 mm, the disclosure may also refer to a pupil having, according to an embodiment of the disclosure, a diameter greater than or equal to 10 mm, for example greater than or equal to 20 mm.

[0112] According to an embodiment of the disclosure, the optical lens comprises an optical center and the center of the pupil is at a distance smaller than or equal to 7 mm from the optical center of the optical lens.

[0113] The use of encapsulated AR coatings generating phase shifts within a designed range allows the modulation transfer function (MTF) curve of the optical lens to mimic that of established myopia control lenses, especially in the low spatial frequency range. Both theoretical simulations and empirical measurements demonstrate that this structure achieves an appropriate contrast reduction while maintaining optical clarity in the central vision zone.

[0114] In the following description, it is referred to a pupil area to characterize the invention. The invention may be characterized over at least four pupils of 6 mm diameters, for example at least over eight pupils of 6 mm diameters, whose centers are at 7.5 mm from the reference point, for example the optical center of the lens element, said four pupils, for example said eight pupils, being evenly spread along a circle of 7.5 mm radius centered on the reference point, for example the optical center of the lens element. The features described for the pupil area may apply to each of the four, for example eight, pupils.

[0115] The invention may be characterized over at least twenty pupils of 6 mm diameters whose centers are at 7.5 mm from the reference point, for example the optical center of the lens element, said twenty pupils being evenly spread along a circle of 10 mm radius centered on the reference point, for example the optical center of the lens element and each of the twenty pupils having the features described for the pupil area in the following description.

[0116] When measured over the pupil area 16 having a diameter equal to or greater than 4.0 mm, the density of optical elements over the pupil area, defined as the ratio of the sum of the areas covered by the optical elements and the total area of the pupil, is greater than or equal to 10 %, for example greater than or equal to 30% and smaller than or equal to 90%, for example smaller than or equal to 80 %, for example smaller than or equal to 75%, for example smaller than or equal to 65%, of the total surface of the pupil area.

[0117] Over a pupil area 16 having a diameter equal to or greater than 4.0 mm and passing through at least one of the plurality of optical elements, the optical lens 10 produces a first optical path difference map (OPD1), a best form fitting of the first optical path map (OPD1) produces a second optical path difference map (OPD2), a differential optical path map (DOP) being composed as the difference between said first optical path difference map (OPD1) and said second optical path difference map (OPD2).

[0118] The differential optical path map (DOP) is a well-known feature describing the optical performances of an optical system. The differential optical path map (DOP) refers to the discrepancy in optical path length experienced by light rays after suppressing the best form and optionally the low-frequency range of the waviness in OPD1. The differential optical path map provides a spatial distribution of the optical path difference values across the pupil on the optical lens. It essentially corresponds to a two-dimensional representation illustrating how the optical path length varies across the pupil.

[0119] The measurement of the OPD1 should be done with an appropriate equipment to measure the optical lens with sufficient accuracy. For example, if optical elements are located on the front and / or back surface of the optical lens and the difference between the minimum and maximum levels is a few hundreds of nanometers, the optical elements may be measured by a 3D optical profiler based on coherence scanning interferometry with sub-nanometer precision in altitude. The optical path may then be derived by multiplying the altitudes by the refractive index difference between the air and the lens material at a specified wavelength.

[0120] The OPD1 may be determined by first, determining three-dimensional information of the optical lens over at least a pupil surface of 8 mm diameter for example at least 16 mm diameter, comprising the shape of the rear face and the front face, the thickness of the optical lens defined between the origins of the rear and front faces and the kinematics between the front and rear surface origins. In addition, the three-dimensional information of the optical lens comprises three-dimensional information about the shape of the optical elements, for example the positions of each optical element in the optical lens (even if the optical elements are encapsuled in a coating or embedded in the thickness of the optical lens between its front and rear faces) the curvature, the diameter, etc.

[0121] Secondly, OPD2 corresponding to the best form of OPD1, is determined using a parametric model such as the aspherical equation, atorical equation, complex polynomial equation, Zernike polynomial or other method to simulate the optical lens. Typically, the skilled person may increase the degree of the polynomial equation or Zernike polynomial until the difference between OPD1 and the parametric model converges.

[0122] The second optical path difference map (OPD2) may be defined over the same pupil area 16. In the context of the disclosure, the second optical path difference map should be understood as the optical path difference map of a theoretical lens having no optical elements and smooth surfaces. In other words, the second optical path difference map (OPD2) corresponds to a spatial distribution of the optical path difference values across the pupil on the theoretical optical lens. For example, the second optical path difference map (OPD2) may correspond to the optical path difference map of the spherical lens that best fits the prescription adapted for the wearer or the average mean spherical power of the optical lens.

[0123] According to one embodiment, the optical path difference is generated at an internal interface between two distinct material layers embedded within the lens volume, without necessarily extending to the external surfaces. Prior to any external coating, the front and rear surfaces of the lens remain smooth and free of microstructures.

[0124] According to the disclosure, each optical element produces constant phase shifting so that the differential optical path map (DOP) is a piecewise constant surface of at least two levels, for example three, for example four, for example eight levels.

[0125] According to an embodiment of the disclosure the at least two levels of the differential optical path map (DOP) are smaller than or equal to 1 pm, preferably, smaller than or equal to 700 nm.

[0126] To demonstrate the presence of at least two discrete levels within a differential optical path map, a method involving the construction of a histogram can be employed. This histogram is created using the range of values obtained from the measurement, spanning from the minimum observed value to the maximum observed value. Each bin in the histogram represents a range of values, determined by a specified width delta, delta being the tolerance around a specific level. The presence of only two discrete levels in the measurement is confirmed if, and only if, exactly two bins within the histogram contain values. In other words, there should be two distinct peaks or populated bins, each representing a discrete level, and the remaining bins should be empty or contain negligible counts. This approach assumes that the variation within each discrete level k is bounded by the tolerance Ak of ±20%, preferably ±10%, more preferably ±5%, allowing for a clear distinction between the different levels present in the measurement. The delta value retained for the histogram would be the maximum of Ak values.

[0127] Alternatively, the presence of at least two discrete piecewise levels within a differential optical path map (DOP) may be determined from the DOP distribution over at least part of the two dimensional representation of the optical lens in the form of a representation of the data as a histogram or a stem-and-leaf plot; and characterizing at least the part of the optical lens within said at least part of the two dimensional representation of the optical lens by analyzing the representation of the data, for example characterizing the histogram or stem-and-leaf plot.

[0128] The histogram can be created using the range of optical path values obtained from the DOP, spanning from the minimum observed value to the maximum observed value. Each bin or bar width in the histogram represents a range of optical path values, determined by a specified bin or bar width. The bin or bar width may be the difference between the maximum observed value and minimum observed value divided by 100, or by the difference between the two extreme peaks of the histogram divided by 100, or by fixing a bin width (for example of 1, 5 or 10 nanometers). The inventors propose to fit each peak area corresponding to a discrete level by a Gaussian curve using a least square adjustment method. One may recover from that a central optical path difference value (mean value of the gaussian) corresponding to a level and a standard deviation.

[0129] If the heights of the levels are fabricated with extremely high precision, only the bins corresponding to each discrete levels should have no null counts. There should be distinct peaks or populated bins, each representing a discrete level, and the remaining bins should be empty or contain negligible counts. In practice, the optical path length differences corresponding to a discrete level k may be fabricated with some tolerances. This approach assumes that the standard deviation of each discrete level k is bounded. The standard deviation of each peak histogram should be below the absolute value of the optical path difference between the lowest and highest levels divided by 10, or preferably divided by 20, and or preferably divided by 40.

[0130] Typically, each optical element of the plurality of optical elements has a characteristic dimension greater than or equal to 1 pm, for example greater than or equal to 2.5 pm, for example greater than or equal to 5 pm and smaller than or equal to 250 pm, for example smaller than or equal to 200 pm, for example smaller than or equal to 50 pm.

[0131] According to an embodiment of the disclosure, the characteristic dimension of an optical element may be the diameter of the circle in which the optical element is inscribed.

[0132] According to an embodiment, at least 50%, for example at least 75%, for example at least 90%, for example all of the optical elements have the shape of a straight block (pixel), a cylinder or a hexagon.

[0133] According to an embodiment at least one level of the differential optical path map (DOP) is close to zero, for example smaller than or equal to 10 nm corresponding to the part of the optical lens without optical elements.

[0134] The at least two levels of the differential optical path map (DOP) may be smaller than or equal to 1 pm, preferably, smaller than or equal to 700 nm.

[0135] At least part of the at least two levels of the optical elements are spatially randomly distributed.

[0136] According to an embodiment of the invention, the random distribution of the at least two levels of optical elements may be characterized using the autocovariance of the differential optical path map (DOP). In particular, the autocovariance of the differential optical path map (DOP) is greater than or equal to 0.4 when calculated with a shift corresponding to the characteristic dimension of the smallest optical element comprised in the pupil of at least 4 mm diameter.

[0137] The autocovariance function of a surface is a measure of the rate of correspondence between the original surface and the same offset of given coordinates.

[0138] For any pair (tx,ty), one may calculate the area under the surface resulting from the product of the original surface and this same surface area offset by (tx,ty). This area calculation is normalized, so we have a value of 1 in (tx=0,ty=0):

[0139] According to an embodiment of the disclosure, the of the autocovariance of the differential optical path map (DOP) between a shift corresponding to the characteristic dimension of the smallest optical element comprised in the pupil and a shift corresponding to the radius of the pupil is smaller than or equal to 0.75, for example smaller than or equal to 0.55.

[0140] According to an embodiment of the disclosure, the autocovariance of the differential optical path map (DOP) is greater than or equal to 0.4 when calculated with any shift greater than or equal to the characteristic dimension of the smallest optical element comprised in the pupil and smaller than or equal to the radius of the pupil.

[0141] According to an embodiment, the autocovariance of the differential optical path map (DOP) when calculated with any spatial shift comprised between one and ten times, for example 20 times, the characteristic dimension of the smallest optical element comprised in the pupil is smaller than or equal to 0.8, for example smaller than or equal to 0.7.

[0142] According to an embodiment, the spatial randomization of the optical elements is quantitatively assessed using the autocovariance function applied to the altitude surface representing the phase modulation. The autocovariance function is defined as the normalized correlation between a surface and its spatially shifted copy. In the present disclosure, the surface altitude is sampled over a grid of 1024x 1024 pixels across a 4 mm pupil diameter, corresponding to a pixel resolution of approximately 3.9 pm. In the case of ideal randomization, where each pixel phase value is selected independently following a uniform distribution, the autocovariance exhibits a sharp drop from 1 to approximately 0.5 after one-pixel shift, with no periodic rebounds. This autocovariance drop characterizes the lack of spatial correlation and thus the truly random nature of the surface perturbation. The randomization is also maintained in dot-based configurations, provided the dots are sparsely distributed such that adjacent dots do not significantly overlap in the shifted domain. In such cases, the autocovariance between a shift corresponding to one pixel and a shift up to the pupil radius remains in a range consistent with a uniform random distribution. This provides a reliable and reproducible metric to quantify the spatial organization of phasemodulating optical elements and to distinguish randomized distributions from periodic or structured ones.

[0143] The inventors have observed that the optical lens comprising the optical elements according to the disclosure, in particular being randomly distributed, allows slowing down the progression of the visual impairment of the eye while maintaining a better visual acuity.

[0144] The image quality (IQ) evaluates the quality of an image formed by the optical lens for an object, for example for central vision. Typically, the image quality may be determined using any well-known eye model and an optical lens model placed in front of the eye model in standard wearing conditions.

[0145] The image quality (IQ) may be based on a Strehl ratio, and / or a Modulation Transfer Function (MTF), and / or a power error, and / or an astigmatism error, and / or a fraction of encircled energy radius, and / or, a spot diagram radius, and / or a point spread function (PSF), and / or an optical transfer function (OTF), and / or a visual Strehl ratio (VSX, VSOTF, VSMTF), and / or a wavefront aberrations.

[0146] The Strehl ratio corresponds to the ratio between the peak value of the actual point spread function (PSF) divided by the peak value of the diffraction-limited point spread function (DL-PSF) for the same pupil size. The image quality (IQ) may also be based on the visual Strehl ratio VSX, VSOTF and VSMTF of the optical system composed of the eye model and the optical lens.

[0147] The image quality (IQ) may be based on the modulation transfer function (MTF). The modulation transfer function is a well-known quantitative measurement that describes the imaging performance of an optical system. It measures the contrast transfer as a function of the spatial frequency of the object being imaged and provides information about the optical system's resolving power and the amount of contrast degradation for different spatial frequencies. The modulation transfer function value may be determined by measuring the 3D surface of the optical lens, determining a 2D representation of optical path differences of a light beam arriving normal to the lens element, determining the point spread function over a pupil aperture, and determining the modulation transfer function over said pupil by a Fourier transform operation. For example, the area under the modulation transfer function curve between two specific limiting frequencies is measured and compared to the area under the diffractionlimited modulation transfer function curve for the same pupil size.

[0148] The value of the modulation transfer function (MTF) produced by the differential optical path map (DOP) may be greater or equal to 0.07, preferably greater or equal to 0.10, over the range of spatial frequencies comprised from 10 to 25 cycles per degree, when measured through the pupil.

[0149] The modulation transfer function (MTF) produced by the differential optical path map (DOP) is obtained with the double Fourier transform of the differential optical path map.

[0150] The modulation transfer function of the differential optical path map (DOP) has a cutoff frequency smaller than or equal to 8 cpd, for example smaller than or equal to 4cpd.

[0151] The cutoff frequency can be defined by:

[0152] „ , PixelSize v cut-off frequency = ————— ——

[0153] , where “Pixel size” corresponds to characteristic dimension of the smallest optical element comprised in the pupil and X being the considered wavelength.

[0154] In the following examples, a surface is composed of an array 1024*1024 square pixels where each pixel representing an optical element. The full surface size is 4 x 4mm, thus the characteristic dimension of the smallest optical element is equal to 3.9 pm. This resolution is also used to compute the MTF produced by the DOP to not limit this calculation.

[0155] Figure 4 illustrates the modulation transfer function (MTF) calculated for a planar wavefront and a pixelated surface with optical elements having randomized optical path lengths. To do that, the inventors have selected a maximal level of optical path length noise (between 0 and coeff*X , X being the considered wavelength). Then, for each pixel on the pupil plane, one may choose a random value x between 0 and this maximal level, defined as coeff* A with coeff and x between [0,1] and x following a uniform distribution.

[0156] Figure 4 illustrated the modulation transfer function (MTF) along a horizontal cross section for several levels of maximal perturbation, coeff* k, and a 4mm pupil diameter. The initial fall is typical of the diffusion. It can be controlled by choosing the maximum level of optical path perturbation. In other words, the scattering can be tuned from the choice of the maximum level the optical path perturbation. Depending on this level, scattering can be light or strong. The manufacturing of this type of optical element may be done using grey-scale lithography.

[0157] Figure 5 corresponds to an embodiment with an optical element that produces constant phase shifting so that the differential optical path map (DOP) is a piecewise constant surface of four levels (0, coeff* / . / 3, 2coeff*X / 3 , coeff* A), with coeff between strictly greater than 0 and smaller than or equal to 1.

[0158] Although the values of the initial drops are different, the effect on the MTF seems similar to the continuous case.

[0159] Advantageously, a four-level piecewise constant surface making is adapted to photolithography. With this process, one can control the altitude (and then the optical path) on each optical element using two masks. The constraint only concerns the level number that must be a power of two (combining many masks).

[0160] Figure 6 corresponds to an embodiment with an optical element that produces constant phase shifting so that the differential optical path map (DOP) is a piecewise constant surface of two levels (0, coeff* / .), with the coeff strictly greater than 0 and smaller than or equal to 1 (NB : curves for coeff and (1 -coeff) values are exactly the same).

[0161] Once again, one obtains an initial fall that is characteristic of the diffusion behavior.

[0162] Therefore, it is possible to control the level of diffusion by photolithography with only one mask.

[0163] According to an embodiment of the disclosure, illustrated on figure 7a and 7b, the optical lens comprises a plurality of dots, each dot comprising a plurality of optical elements randomly distributed over the dots and the differential optical path map (DOP) is close to zero in the zone of the optical lens without dots.

[0164] According to an embodiment, at least 50%, for example at least 75%, for example at least 95%, for example all of the dots have a circular shape. According to an embodiment, at least 50%, for example at least 75%, for example at least 95%, for example all of the dots have a square shape.

[0165] Each dot may have a characteristic dimension greater than or equal to 150 pm and smaller than or equal to 400 pm.

[0166] The density of optical elements within each dot is preferably greater than or equal to 20 % of the surface of the dot and smaller than or equal to 75% of the surface of the dot.

[0167] The density of dots over the pupil is greater than or equal to 15 % of the surface and smaller than or equal to 80% of the surface of the pupil.

[0168] As illustrated on figure 7a, the dots may be positioned according to a regular mesh. According to such embodiment, each optical element within a dot produces constant phase shifting so that the differential optical path map (DOP) is a piecewise constant surface of at least two levels and at least part of the at least two levels is spatially randomly distributed over the dot.

[0169] Alternatively, as illustrated on figure 7b, the dots may be spatially randomly distributed.

[0170] Preferably, each optical element within a dot produces constant phase shifting so that the differential optical path map (DOP) is a piecewise constant surface of at least two levels and at least part of the at least two levels is spatially randomly distributed over the dot.

[0171] Many further modifications and variations will be apparent to those skilled in the art upon making reference to the foregoing illustrative embodiments, which are given by way of example only and which are not intended to limit the scope of the disclosure, that being determined solely by the appended claims.

[0172] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be advantageously used. Any reference signs in the claims should not be construed as limiting the scope of the disclosure.

Claims

CLAIMS1. An optical lens intended to be worn in front of an eye of a wearer to correct a vision impairment and to slow down the progression of said vision impairment of an eye of a wearer, said optical lens comprises a plurality of optical elements, wherein: at least one light ray passing through the optical lens over a pupil having at least a 4 mm diameter passes through at least one of the plurality of optical elements, wherein over the said pupil the optical lens produces a first optical path map (OPD1), a best form fitting of the first optical path map (OPD1) produces a second optical path difference map (OPD2), a differential optical path map (DOP) being composed as the difference between said first optical path difference map (OPD1) and said second optical path difference map (OPD2), each optical element produces constant phase shifting so that the differential optical path map (DOP) is a piecewise constant surface of at least two levels and at least part of the at least two levels is spatially randomly distributed.

2. An optical lens according to claim 1, wherein each optical element has a characteristic dimension greater than or equal to 1 pm and smaller than or equal to 250 pm.

3. The optical lens according to claim 1 or 2, wherein at least one level of the differential optical path map (DOP) is close to zero, for example smaller than or equal to 10 nm, corresponding to the part of the optical lens without optical elements.

4. The optical lens according to any of the preceding claims, wherein the at least two levels of the differential optical path map (DOP) are smaller than or equal to 1 pm, preferably, smaller than or equal to 700 nm.

5. The optical lens according to any of the preceding claims, wherein the pupil has a diameter greater than or equal to 10 mm, for example greater than or equal to 20 mm.

6. The optical lens according to any of the preceding claims, wherein the optical lens comprises an optical center and the center of the pupil is at a distance smaller than or equal to 7 mm from the optical center of the optical lens.

7. The optical lens according to any of the preceding claims, wherein the density of optical elements over the pupil is greater than or equal to 10 % of the surface and smaller than or equal to 75 % of the surface.

8. The optical lens according to any of the preceding claims, wherein a modulation transfer function produced by the differential optical path map (DOP) is greater or equal to 0.07, preferably greater or equal to 0.10, over the range of spatial frequencies comprised from 10 to 25 cycles per degree, when measured through the pupil.

9. The optical lens according to any of the preceding claims, wherein a modulation transfer function produced by the differential optical path map (DOP) has a cutoff frequency smaller than or equal to 8 cpd, for example smaller than or equal to 4cpd.

10. The optical lens according to any of the preceding claims, wherein the autocovariance of the differential optical path map (DOP) when calculated with a spatial shift corresponding to characteristic dimension of the smallest optical element comprised in the pupil is greater than or equal to 0.4.

11. The optical lens according to claim 10, wherein the autocovariance of the differential optical path map (DOP) when calculated with any spatial shift comprised between one and ten times the characteristic dimension of the smallest optical element comprised in the pupil is smaller than or equal to 0.8.

12. The optical lens according to any of the preceding claims, wherein the autocovariance of the differential optical path map (DOP) between a shift corresponding to the characteristic dimension of the smallest optical element comprised in the pupil and a shift corresponding to the radius of the pupil is smaller than or equal to 0.75, for example smaller than or equal to 0.55.

13. The optical lens according to any of the preceding claims, wherein the autocovariance of the differential optical path map (DOP) is greater than or equal to 0.4 when calculated with any shift greater than or equal to the characteristic dimension of the smallest optical element comprised in the pupil and smaller than or equal to the radius of the pupil.

14. The optical lens according to any of claims 1 to 12, comprising a plurality of dots, each dot comprising a plurality of optical elements randomly distributed over the dots and the differential optical path map (DOP) is close to zero in the zone of the optical lens without dots.

15. The optical lens according to claim 14, wherein the density of optical elements within each dot is greater than or equal to 20 % of the surface of the dot and smaller than or equal to 75% of the surface of the dot.

Images