Method for manufacturing optical devices with microstructures, manufacturing system for carrying out such a method, and optical devices obtained thereby

Abstract

A method for manufacturing an optical device (1) includes the steps of obtaining a transparent base (2) with a free surface (21) having a predetermined curvature, immersing at least a portion of the free surface (21) in a first curable material (14), determining a first grayscale image (12) representing a microstructure (3) to be created on the portion of the free surface (21), projecting the first grayscale image (12) onto the portion of the free surface (21) with UV light having a predetermined intensity, and curing a volume of the first curable material (14) covering the portion of the free surface (21) by irradiating said volume through the transparent base (2). An optical device (1) manufactured by this method and a system for manufacturing such an optical device (1) by this method are also disclosed.

Description

[Technical Field]

[0001] The present disclosure relates to methods for manufacturing optical devices comprising microstructures and manufacturing systems configured to carry out such methods. The present disclosure also relates to the optical devices obtained thereby. [Background technology]

[0002] The document (Patent Document 1) discloses a method for producing an optical device from a volume of curable composition, in which portions of the volume are polymerized by irradiating the outer surface of the volume and optionally a pre-polymerized top with light irradiation. In such a method, the light irradiation results in a light intensity that varies on the outer surface (i.e., locally changes the light intensity on the surface) through the use of a spatial light modulator, and can also vary over time. Thus, polymerization is carried out sequentially for each portion of the curable composition.

[0003] On the other hand, in optical devices such as ophthalmic lenses, specific surface morphologies, including microstructures, may be useful to produce specific effects and / or to control various vision disorders.

[0004] For example, microlenses may be useful in ophthalmic lenses, particularly for the purpose of slowing the progression of myopia in children.

[0005] It is therefore desirable to provide a method for manufacturing optical devices that includes specific surface morphologies, such as microstructures, that is flexible in use compared to other techniques, such as diamond turning or lithography, injection molding or casting processes, and that allows for flexibility in forming lenslets or other shapes, and that allows for such microstructures to be fabricated on a surface and ultimately encapsulated inside an optical device, such as a lens. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2019002905 Brochure Summary of the Invention [Means for solving the problem]

[0007] According to a first aspect, there is provided a method for manufacturing an optical device comprising a microstructure from a transparent base, the method comprising the steps of: - obtaining a transparent base having a free surface on which at least a portion is to be microstructured, the free surface having a predetermined curvature; Immersing at least a portion of the free surface in a first hardenable material; determining a first grayscale image representative of a microstructure to be created on a portion of the free surface; projecting a first grayscale image onto a portion of the free surface of the transparent base with ultraviolet light having a predetermined intensity; curing a volume of first curable material covering a portion of the free surface by irradiating the volume of first curable material through the transparent base with a first grayscale image of ultraviolet light that provides different doses of light to portions of the surface, thereby forming a microstructure on the portion of the free surface of the transparent base; A method is provided, comprising:

[0008] Here, the transparent base includes, for example, a substrate and a film.

[0009] By "transparent" is meant here that the base transmits at least 1% or preferably at least 80% of light at a given wavelength, in particular here at least UV light. For example, 1000 mw / cm 2 At 1% of this, it is 10mW / cm 2 is obtained, which is already suitable for some chemicals. The rate may be strongly dependent on the chemical reactivity under UV.

[0010] For example, the first grayscale image projected by a DMD (Digital Micromirror Device) acts as a projection pattern.

[0011] Thus, the first grayscale image allows for the illumination of at least a portion of the free surface with a light beam for a predetermined exposure time and at a predetermined intensity, and depending on the gray level at a point (pixel) in the image, a specific corresponding light dose is provided at the corresponding point on the surface, resulting in a corresponding height of the microstructure made from the first curable material cured at that point on the surface.

[0012] It is worth noting that here grey levels or greyscales refer to patterns in light in the UV region.

[0013] Grey level modulation by the projection device over time can then be avoided.

[0014] Such a method therefore allows for the formation of a modified surface comprising a microstructure on at least a portion of a transparent base in a single step by volume additive manufacturing, without the need for layering.

[0015] Compared to the free surface of the transparent base, microstructures of different heights can be created simultaneously during the same step by the first grayscale image.

[0016] Therefore, the method provides different doses (e.g., measured in millijoules (mJ)) locally and different intensities (e.g., milliwatts times square centimeter (mW / cm)). 2 ) does not provide localized light intensity (measured by ). The intensity is the same and does not change or changes very little, but the light is distributed differently in time over parts of the surface due to the gray levels and, according to an exemplary embodiment, due to the associated vibrations of the micromirrors of the DMD.

[0017] In other words, the design to be produced is obtained using one calculated image pattern and one calculated exposure time, and these are closely linked, i.e., to change the design to be produced, both must be changed.

[0018] Such methods therefore allow for the creation of personalized or customized optical devices, such as lenses.

[0019] According to one embodiment, determining the first greyscale image comprises determining the height of the microstructures per pixel compared to the free surface.

[0020] According to one embodiment, the method includes displacing a transparent base relative to the grayscale image projection tiles, and generating a separate first grayscale image according to the displacement of the transparent base.

[0021] According to one embodiment, the method includes removing at least a portion of the remaining first curable material from the optical device by at least rotating the optical device.

[0022] According to one embodiment, the method includes cleaning at least a surface of the microstructure with a cleaning material, removing the surface of the microstructure from the cleaning material, and rotating the optical device.

[0023] For example, such a step may be performed before the step of immersing at least the surface of the microstructure in a second curable material, as described below.

[0024] According to one embodiment, the method includes immersing at least the surface of the microstructure in a second curable material.

[0025] According to one embodiment, the method includes emptying a container containing a first curable material into which at least one surface of the microstructure is immersed while a transparent base is maintained by a blocker, and filling the container with a second curable material while the transparent base is maintained on the blocker.

[0026] According to one embodiment, the method includes, prior to the step of immersing at least the surface of the microstructure (3) in the second curable material, the steps of cleaning at least the surface of the microstructure (3) with the second curable material, removing the surface of the microstructure (3) from the second curable material, and rotating the optical device (1).

[0027] According to one embodiment, the method comprises: determining a second grayscale image according to the surface of the microstructure (3) and the design of the encapsulation layer (4) to be created to encapsulate at least a part of the microstructure (3); projecting a second grayscale image onto at least a portion of the surface of the microstructure (3) using UV light; irradiating a volume of a second curable material through the transparent base and the microstructure (3) with a second grayscale UV light image to cure the volume covering a portion of the surface of the microstructure (3), thereby encapsulating at least a portion of the microstructure (3); Includes:

[0028] According to a second aspect, there is provided an optical device manufactured by the method described above.

[0029] Because the micromirrors in a DMD are not perfectly bonded, corresponding discontinuities can be found in the material, which can ultimately be detected using very powerful machines.

[0030] Furthermore, some designs are very difficult or nearly impossible to obtain in any other way, for example, diffractive lenslets on surfaces or encapsulated lenslets are very difficult to manufacture using molds.

[0031] The method described above allows for the production of things in one go that require several molding / countermolding steps to get the same product.

[0032] For example, a π Fresnel lens would be a very difficult design to achieve otherwise.

[0033] For example, the optical device comprises a microstructure formed on at least the surface of a transparent base.

[0034] For example, the optical device may include an encapsulation layer, and the microstructure may be encapsulated beneath the encapsulation layer.

[0035] For example, the microstructures comprise at least one of lenslets, diffusive elements, diffractive elements, and / or π-Fresnel lenslets.

[0036] According to a third aspect, there is provided a system for manufacturing an optical device as described above.

[0037] For example, the system may be configured to perform the methods described above.

[0038] For example, the system mainly a container for containing a volume of hardenable material; a DLP projector comprising a UV light source configured to emit UV light at a predetermined intensity; a digital micromirror device configured to project at least one grayscale image onto a projection tile toward the interior of the container using UV light; Equipped with.

[0039] The optional features presented above in relation to the proposed method may also be applied to such a system.

[0040] The present disclosure can be used for any type of optical device, such as an optical lens or an ophthalmic element or device.

[0041] Non-limiting examples of ophthalmic elements include corrective and non-corrective lenses, including single-vision or multi-vision lenses that may or may not be segmented, as well as other elements used to correct, protect, or improve vision, including, without limitation, eyeglasses, glasses, goggles, and magnifying and protective lenses or visors such as those found in helmets.

[0042] Therefore, the above-described embodiment may have the following advantages. Creating any type of microstructure (lenslets: refractive, diffractive, diffusing) on ​​a flat or curved transparent base; Microstructures can be made directly on any transparent substrate (lens or other element, e.g. mold (glass or plastic), insert (glass or metal), wafer, film, etc.), Creating microstructures with a refractive index different from that of a transparent base (e.g. for encapsulation), Creating optical devices with at least two parts with different refractive indices for encapsulation of microstructures; Creating personalized microstructures (power, density, type of array, area on the lens) depending on the wearer (e.g. depending on the wearer's sensitivity to contrast reduction, the wearer's activity, the wearer's retinal shape, the wearer's rate of progression of myopia (or other visual disorder or refractive error), etc.), · Provides a non-stratified process.

[0043] In the case of encapsulation, the following additional advantages may be offered: The microstructure is protected by an encapsulation layer, The chemicals used for microstructuring do not necessarily have the usual thermomechanical properties (HDT around 80°C, E>2GPa, etc.) suitable for ophthalmic applications, since they are embedded inside the appropriate microstructure. This allows for greater freedom to design chemicals with typically high refractive indexes. The encapsulation layer can provide a smooth top surface, so there are no hard coat deposition issues due to the microstructure design; The very high refractive index allows for microstructures with materials that do not necessarily meet the requirements of ophthalmic applications.

[0044] Advantageous embodiments are described below by way of non-limiting example with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0045] [Figure 1] 1 illustrates an exemplary embodiment of an optical device having a transparent base with microstructures formed on its surface. [Figure 2] 1 illustrates an exemplary embodiment of an optical device having microstructures formed inside the optical device. [Figure 3] 1A and 1B illustrate a schematic diagram of an exemplary embodiment of an optical device comprising aspheric lenslets arranged in concentric rings. [Figure 4] 1 shows a schematic representation of a monofocal lenslet. [Figure 5] 1 shows a schematic representation of a bifocal lenslet. [Figure 6] 1 shows a schematic representation of a π-Fresnel lenslet. [Figure 7] An exemplary embodiment of a system for manufacturing an optical device such as that shown in FIG. 1 or FIG. 2 is presented. [Figure 8] 1 is an illustration of a manufacturing system in accordance with an illustrative embodiment. [Figure 9] 10A and 10B illustrate schematic diagrams of lenslets forming on the surface of a transparent base, according to an exemplary embodiment; [Figure 10] 10A and 10B illustrate schematic contours of lenslets forming on the surface of a transparent base according to another exemplary embodiment. [Figure 11] Schematic representation of the experiment to identify the parameters of the Jacob equation (Ec and Dp). [Figure 12] Grayscale images for forming a refractive spherical lenslet (10 μm pixel size) for myopia are shown. [Figure 13]Grayscale images for forming a diffractive π Fresnel lenslet (5 μm pixel size) for myopia are shown. [Figure 14] 10 illustrates the relative displacement of a grayscale image projection tile compared to a transparent base when the projection tile is smaller than the transparent base. [Figure 15] Shown is a calculated image of a refractive spherical lenslet (10 μm pixel size, 4k projector). [Figure 16] The calculated image is shown to create a base radius of curvature CX=500 mm and a lens diameter=70 mm using a DLP with a pixel size of 35 μm and a resolution of 4 k. DETAILED DESCRIPTION OF THE INVENTION

[0046] The following disclosure refers to additive manufacturing techniques for producing ophthalmic lenses, for example to reduce myopia progression in children.

[0047] For example, lenslet fabrication by the specific technique of volumetric additive manufacturing is described herein.

[0048] The disclosed method allows for the provision of optical devices with any surface geometry, in particular ophthalmic lenses for myopia control using lenslets, however, it can be extended to other subjects besides myopia control, depending for example on the microstructures to be produced.

[0049] It should be noted that the ophthalmic lens may be any ophthalmic device for spectacle lenses or any other device adapted to a wearer and having ophthalmic properties.

[0050] It is also noted that the additive manufacturing method may be carried out according to any suitable existing technology, for example a technology included in the definition given by the reference ISO / ASTM52900:2021 or a corresponding reference.

[0051] Structural aspects of the optical lens are described below. The optical lens comprises microstructures that may be located on the convex anterior side (also called the object side) or on the concave posterior side (also called the eye side) of a major surface of the optical lens, or on both major surfaces.

[0052] The microstructure comprises at least one lenslet.

[0053] A lenslet modifies the power of an input light to produce an output light by modifying either its refractive power or its phase.

[0054] The lenslets may form bumps and / or depressions in the major surface on which they are disposed. The outer shape of the lenslets may be round or polygonal, for example hexagonal.

[0055] The lenslets may be spherical, toric, or have an aspheric shape, and may or may not be rotationally symmetric. The lenslets may have a single focus, or a cylindrical strength, or a non-focusing focus. In a preferred embodiment, the lenslets may be used to arrest the progression of myopia or hyperopia. In that case, the base lens substrate includes a base lens that provides a refractive power to correct myopia or hyperopia, and the lenslets may each provide a refractive power greater than that of the base lens if the wearer is myopic, or have a refractive power less than that of the base lens if the wearer is hyperopic.

[0056] The lenslets may also be diffractive structures such as Fresnel structures, lenslets each defining a Fresnel structure, permanent technological bumps, or phase shifting elements. The lenslets may also be refractive optical elements such as microprisms, and light dispersive optical elements such as small protrusions or cavities, or any type of element that creates irregularities on a substrate.

[0057] The lenslets may also be π-Fresnel lenslets as described in U.S. Patent No. 2021109379, i.e., Fresnel lenslets whose phase function has a π phase jump at the nominal wavelength, as opposed to a monofocal Fresnel lens whose phase jump is a multiple of 2π. Such lenslets include structures with discontinuous shapes. In other words, the shape of such structures can be described by an elevation function in terms of distance from the base level of the major surface of the optical lens to which the lenslet belongs, and that function exhibits a discontinuity, or its derivative exhibits a discontinuity.

[0058] The lenslets of the present invention may have a contour shape that can be inscribed in a circle having a diameter of 0.5 micrometers (μm) or more and 2.5 millimeters (mm) or less.

[0059] The lenslets of the present invention have a maximum height, measured in a direction perpendicular to the major surface on which they are disposed, that is equal to or greater than 0.1 μm and equal to or less than 50 μm. The major surface can be defined as a surface, which can be planar, spherical, cylindrical, or even complex, and includes the central locations of all microstructures. This major surface can be a virtual surface when the microstructures are embedded in the lens, or it can be close to or identical to the physical outer surface of the ophthalmic lens when the microstructures are not embedded. The height of the microstructures can then be determined by using a local normal axis to this major surface and calculating, for each point of the microstructure, the difference between the maximum positive deviation and the minimum negative deviation relative to the major surface along this axis.

[0060] The lenslets may have a periodic or quasi-periodic layout, but may also have random positions. Typical layouts of lenslets may be a honeycomb layout with a constant grid step, a plurality of concentric rings, or a continuous grid, e.g., with no spaces between the microstructures.

[0061] These structures can modify an optical wavefront in intensity, curvature, or light deflection, where the wavefront intensity is configured such that the structures can be absorptive and can locally absorb wavefront intensity in the range of 0% to 100%, the curvature is configured such that the structures can locally modify wavefront curvature in the range of ±20 diopters, and the light deflection is configured such that the structures can locally scatter light at angles in the range of ±1° to ±30°.

[0062] The distance between structures can range from 0 (adjacent) to 3 times the distance between structures (distinct microstructures).

[0063] In this example, first, several types of lenslet designs and lenses as optical devices will be described with reference to FIGS.

[0064] Currently, various design solutions exist for optical devices, such as ophthalmic or contact lenses, that can slow the progression of myopia. These examples are based on the use of microstructures, such as optical lenslets, that generate a defocused or unfocused light signal in front of the retina. Such lenslets slow the process of elongation of the eye, also called the "myopic" process.

[0065] Such microstructures are formed, for example by volume additive manufacturing, on the surface of the transparent base 2 of the optical device 1, as shown in FIG. 1, or inside the optical device 1, as shown in FIG.

[0066] More specifically, here, FIG. 2 shows an optical device 1 comprising a transparent base 2 and a microstructure 3, where the microstructure 3 can even be formed by material A on the surface of the transparent base 2 in a first step and then encapsulated in another material, material B, after which a second step results in a microstructure made of material A, which is finally formed inside the optical device 1, after which the optical device 1 comprises the transparent base 2, the microstructure 3, and the encapsulation 4 covering the microstructure 3.

[0067] According to one exemplary embodiment, the microstructured elements may be arranged in concentric rings and may comprise aspheric lenslets that create multiple volumes of unfocused light in front of the retina.

[0068] Such an arrangement is shown diagrammatically in FIG.

[0069] According to another exemplary embodiment not shown here, the lenslets are arranged in a pattern of spherical lenslets in a hexagonal array and in "isolated islands" that create multiple defocus areas in front of the retina.

[0070] Other studies of diffuse / scattering lenslets have also demonstrated favorable results for myopia control efficacy.

[0071] Other shapes of microstructures also appear to be interesting for different visual impairment suppression.

[0072] It therefore seemed interesting to be able to fabricate optical devices with microstructures either on the surface of the elements or even inside the elements themselves, as the case may be.

[0073] It also appeared interesting to be able to fabricate optical devices with very different shaped microstructures, such as diffusing lenslets, scattering lenslets, diffusing or scattering dots, refractive lenslets (e.g., monofocal lenslets as shown in FIG. 4, or bifocal lenslets as shown in FIG. 5, or toric lenslets), diffractive lenslets (e.g., π-Fresnel lenslets as shown in FIG. 6), etc., optionally with a second optical function for myopia suppression, which may be spherical or aspherical or other shapes.

[0074] For example, the lenslets of one optical device may have a "gradient law" which refers to a change in the optical function of the lenslet (e.g., the surface power of an aspheric lenslet varies with the position of the lenslet on the lens, e.g., depending on the lens decenter), or may have a mixture of at least two of different forms of lenslets.

[0075] Documents WO2022112531, WO2022112533 ​​or WO2022112534 disclose refractive, diffractive and diffusing lenslets.

[0076] However, all of these shapes are very difficult to form in optical devices using conventional optical device manufacturing methods and corresponding systems.

[0077] An exemplary embodiment of a method and corresponding system for manufacturing such an optical device is described with reference to FIGS.

[0078] In the described embodiment, a volumetric additive manufacturing method is used to fabricate microstructures on a predetermined surface.

[0079] This method uses a DLP projector 10 that projects a UV light grayscale image 12 onto a projection tile 11 to harden a volume of material 14, e.g., resin, at specific / predetermined locations. In other words, the grayscale image 12 can selectively activate hardening of the material 14 in predetermined areas. Thus, the higher the light dose provided to a single point, the thicker the voxel of hardenable material 14 will be (as explained by the Jacobs equation, as detailed below).

[0080] For example, an image pattern is generated (calculated) to form an image or document file (such as a .tiff, .jpg, or .png document file). This is a grayscale image that is loaded into a DLP, which consists of LEDs and a DMD. The DMD is like a "grid" that can "structure" the light coming from the LEDs. In other words, the DMD "pixelates" or "shapes" the light flow. Each micromirror in the DMD can be controlled individually. At gray level 256 (white), the micromirror (or pixel) remains "open" (light is passing through). At gray level "0," the micromirror (or pixel) remains "closed" (light flux is stopped). At gray level 128, the micromirror alternates between the "open" and "closed" states, providing half the amount of light compared to gray level 256.

[0081] FIG. 7 shows an exemplary embodiment of a system for performing such a method.

[0082] For example, a system for manufacturing optical devices comprises such a DLP projector 10.

[0083] The DLP projector 10 comprises a light source configured to emit light at a predetermined intensity and in a defined wavelength range, for example in the UV (ultraviolet) range, for example at wavelengths between 190 nm and 550 nm, more particularly between 300 nm and 420 nm.

[0084] To this end, the light source comprises, for example, an LED for emitting light in the desired wavelength range.

[0085] For example, the DLP projector 10 here comprises a UV video projector.

[0086] DLP projector 10 is also configured to provide a desired grayscale light pattern (image) 12 that is displayed on projection tile 11 .

[0087] To this end, the DLP projector 10 includes a DMD (Digital Micromirror Device).

[0088] A DMD comprises hundreds or even thousands of microscopic mirrors arranged in an array. One micromirror corresponds to one pixel in the projected image. The micromirrors can be individually rotated to be positioned in either an "on" or "off" position. In the "on" position, light from the light source is reflected back into the lens, making the image pixel appear bright, while in the "off" position, the light is directed elsewhere, i.e., not into the projection tile 11, making the pixel appear dark. To create grayscale, the micromirrors are switched on and off at a predetermined frequency, with the ratio of "on" to "off" time determining the color tone produced (also known as "binary pulse width modulation").

[0089] Therefore, the grey scale allows intermediate values ​​of light energy to be provided.

[0090] Thus, the light intensity simply remains the same, but the amount of light varies from pixel to pixel.

[0091] For example, a screen projector such as a DLP (Digital Light Processor) can provide different levels of gray in a 2D projection. The micromirrors of the DMD embedded in the DLP vibrate at up to 256 or even 1024 different frequencies, and can therefore generate up to 256 or even 1024 different light energies across a single projection tile (i.e., one image), and therefore 256 or even 1024 gray levels from "dark" to "white," and 254 (or 1022) intermediate gray levels.

[0092] For example, the grayscale image 12 that must be projected onto a surface to generate the microstructure is calculated with respect to a digital material (resin) model that takes into account the gray levels and thickness changes over time as it hardens under light.

[0093] As an example of a digital material model, a modified Jacobs equation can be used to predict the grayscale provided in relation to the height of a voxel polymerized over a given time period.

[0094] Thus, the DLP projector 10 also comprises a container 13 for containing a volume of curable material 14 .

[0095] To grow the microstructures 3 on the surface 21 of the transparent base 2 , the surface 21 is positioned relative to the projection tile 12 .

[0096] Light emitted by the light source passes through the transparent base 2 and reaches the curable material 14 , growing microstructures on the surface 21 .

[0097] According to an interesting embodiment, the system also comprises a blocker configured to keep at least the transparent base of the optical device 1 in place.

[0098] FIG. 8 shows a flow chart of the method steps for fabricating the designed optical device.

[0099] Two exemplary embodiments of adjacent lenslets constructed according to the chart of FIG. 8 are described: a refractive spherical lenslet and a diffractive π-Fresnel.

[0100] For example, the transparent base can be an optical element made of, for example, MR7, MR8, ORMA, or the like.

[0101] For the present example, a biplanar ORMA (refractive index RI=1.498) is chosen as the transparent base.

[0102] It is worth noting that the transparent base must transmit a minimum amount of light energy from the light source so that the material (resin) that forms the microstructure on the surface of the transparent base can be cured. In this regard, the transparent base and / or the light source can be adapted depending on the optical device to be manufactured.

[0103] Step S1: Design to be created First design In step S1, the design to be created is the shape that must be cured on a transparent base.

[0104] According to a first design, it is desirable to form refractive spherical lenslets on a transparent base as described above.

[0105] A cross section of such a microstructure 3 is represented diagrammatically in FIG.

[0106] In this figure, the abscissa represents the length of the microstructures 3 (in particular the diameter of the lenslets) and the ordinate represents the height of the microstructures 3 (lenslet height).

[0107] Thus, nine lenslets and two halves on either side are shown in this diagram.

[0108] All lenslets are now identical and have the same height and diameter.

[0109] Second Design According to a second design, it is desirable to form a diffractive π Fresnel lenslet on the transparent base described above.

[0110] Such a profile is represented diagrammatically in FIG.

[0111] 9, the abscissa in FIG. 10 represents the length of the microstructure 3 and the ordinate represents the height of the microstructure 3. In the same manner as in FIG.

[0112] Thus, three diffractive π Fresnel lenslets are depicted in FIG.

[0113] All these lenslets are now identical and have the same height and the same diameter.

[0114] Step S2a: Hardware specifications The projector used here has the following specifications in the system described in relation to FIG. Resolution: 3840 x 2160 pixels (4k) Pixel size: 35 μm, 10 μm or 5 μm (the pixel size is set depending on the required accuracy of the (de)focusing system), Projection Tile 11: 134.4 x 75.6 mm, or 38.4 mm x 21.6 mm, or 19.2 x 1.08 mm, Light source LED emission wavelength: 365nm, LED light intensity: 10mW / cm 2

[0115] Step S2b: Digital material model In this example, the Jacobs equation is used as the digital material model because it provides a good fit with the corresponding experiments, as explained in connection with FIG.

[0116] However, it is worth noting that digital material models do not necessarily follow the Jacobs equation. This depends strongly on the "material response" under light exposure. Therefore, alternative equation models can be used instead of the Jacob equation.

[0117] Therefore, the digital material model adapted to the resin used in the exemplary embodiment of this description is based on the Jacobs equation as follows: E(z)=Ec*exp[z / Dp] where: Z is the thickness of the polymerized material (in μm), which corresponds to its height compared to the surface of the transparent base, E(z) is millijoules × square centimeters (mJ / cm 2 is the amount of energy provided to polymerize a material thickness of z, in units of Ec is the minimum energy (i.e., energy threshold) provided to polymerize a non-null thickness, here Ec=10.9 mJ; ·Dp is the light penetration depth (micrometers), here Dp=11 μm.

[0118] The light penetration depth (Dp) represents the distance that light traverses through the resin before being absorbed by approximately 35%.

[0119] The critical energy (Ec) indicates the minimum light dose that must be applied to cause a material to change from a liquid state to a solid state.

[0120] This means that a light dose (E) above a critical energy (Ec) is required to polymerize the material onto the transparent base.

[0121] On the other hand, the delivered energy (light dose) is also a function of the gray level, intensity and time of light irradiation, as follows: E=GS*I*t where: GS is the gray level that varies from 0 to 1, · i is milliwatts × square centimeters (mW / cm 2 ) is the intensity of the emitted light, ·t is the exposure time (seconds).

[0122] Substituting the energy amounts into the equation involving the grayscale values ​​gives the following:

number

number

[0123] In this example, EC and DP are determined by linearization of the Jacobs equation, which consists of measuring polymerization thickness for different light doses.

[0124] For example, as shown diagrammatically in FIG. 11, an experiment was performed as follows. (i) A transparent base 2, here comprising a glass plate transparent to UV light, is placed on a curable material 14, here comprising a liquid resin, as shown in Figure 11A). (ii) UV light of a square shape (for example, at 365 nm in this case) is projected across the transparent base 2. (iii) Steps (i) and (ii) are repeated for different irradiation times t1, t2, t3, and t4 (where t1 < t2 < t3 < t4), as shown in Fig. 11B. Next, the polymerization thickness is measured with a micrometer. This indicates that the longer the irradiation time (light dose), the thicker the polymerization structure. (iv) Finally, the polymerization thickness (in mm) versus ln(E) is plotted as shown in Fig. 11C (the "standard curve") and fitted with the Jacob equation to reach Ec and Dp.

[0125] Composition of the material 14 used In this example, the material 14 to be polymerized, which is used to form the microstructure 3, is a resin, and its properties are obtained while blending the compounds as follows:

[0126]

Table 1

[0127] [[ID=,27]]Due to the relatively high level of the UV absorber, a special mixing must be applied.

[0128] [[ID=,30]] The acrylate monomer / oligomer resin is heated to 50 °C, and then the UV absorber is gradually added while stirring vigorously for 3 days.

[0129] Thereafter, vigorous stirring is continued at 50 °C for 1 week.

[0130] After 1 week, the resin is slowly cooled to 23 °C, the photoinitiator is added, and the mixing continues for 24 hours.

[0131] The formulation is filtered through a 1-μm filter to control Dp.

[0132] The refractive index of the material (resin) after curing is approximately 1.498, resulting in: · The simultaneous refractive power of -0 / +4dp (λ=550nm) of the diffractive π Fresnel lenslet (described above), +2.75dp for the refractive spherical lenslet design (described above), By changing the curvature and sag of the lenslets and adapting the manufacturing parameters, different optics of the lenslets can be defined in order to change the refractive power or the efficiency ratio at 550 nm, or by using materials with different refractive indices, or encapsulation solutions can also be envisaged with lower refractive index differences (explained below).

[0133] Step S3: Image calculator The image calculator is a numerical tool (eg, a script) that converts the "design to be created" (step S1 in FIG. 8) into a grayscale image by taking into account the hardware specifications and digital material models.

[0134] Also, if the projection tiles 11 are smaller than the entire design to be produced, the image is cut for sequential projection (eg, as shown in FIG. 14).

[0135] Step S4: Grayscale image to be projected is loaded into the DLP For illustrative purposes, FIGS. 12 and 13 show grayscale images for forming lenslets for myopia, corresponding to the contours of FIGS.

[0136] More specifically, FIG. 12 shows a grayscale image for forming a refractive spherical lenslet (10 μm pixel size) corresponding to the profile of FIG. 9, and FIG. 13 shows a grayscale image for forming a diffractive π Fresnel lenslet (5 μm pixel size) corresponding to the profile of FIG. 10.

[0137] Step S5: Image projection The at least one generated image is projected onto the surface 21 of the transparent base 2 that is at least in contact with the curable material 14 .

[0138] This step is also called "curing."

[0139] The images are projected according to a time calculated by an image calculator, e.g. -26.75 seconds for refractive spherical lenslets (Fig. 12), · For diffracted π Fresnel lenslets, -43.25 seconds (Figure 13).

[0140] When using a grayscale image to create microstructures, it may be appropriate to activate this grayscale image (i.e., the light on the image) multiple times, especially when the propagation frontier of the cured material (between the cured and uncured material) releases a lot of thermal energy due to the polymerization process.

[0141] When printing high resolution microstructures with high spatial frequencies, e.g., Fresnel structures, propagation of such front surfaces along the Z axis (height compared to the surface of the transparent base) causes diffraction / scattering, thereby altering the initial desired shape of the microstructures.

[0142] This leads to undesirable light distribution in the further Z direction caused by constructive / destructive interference, which is difficult or even impossible to compensate for by changing the illumination pattern.

[0143] Similarly, if it is necessary to create scattering / diffusing microstructures on a transparent base at a specific location, for similar reasons it is desirable to activate the grayscale image when the propagation front reaches this location in order to limit undesired light distribution at the propagation front.

[0144] As an example, if it is desired to provide a lens with microstructures on one surface, it may be desirable to use a first grayscale image to create a propagation front corresponding to the lens refractive power (low spatial frequencies), and then, when the propagation front is close to the location of the desired microstructure, display a second grayscale image to create a propagation front corresponding to the microstructure.

[0145] In this case, the microstructures are positioned on the transparent base surface furthest from the light source.

[0146] Step S6: Cleaning and post-curing After the microstructure 3 has been formed, the method may further comprise a step of cleaning the surface of the optical device 1 thus obtained.

[0147] For example, the transparent base with the microstructures 3 is rotated to remove residual material 14 from the surface of the optical device 1 .

[0148] When the size of the projection tile is smaller than the size of the surface on which the microstructure is formed If the size of the projection tiles 11 is smaller than the surface 21 of the transparent base 2 on which the microstructures (lenslets) need to be formed, the fabrication of the optical device is performed by relative displacement of the projection tiles 11 compared to the transparent base 2. This is illustrated by Figure 14.

[0149] The relative motion can be stepwise or continuous.

[0150] If the displacement is continuous, then a "film" or a series of images must be used.

[0151] In this way, the grayscale image is reproduced as a function of the frequency of displacement of the projection tile 11 and the discretization of the theoretical shape of the microstructure by "pixelation" (e.g., the grayscale image is reproduced each time the relative movement between the projection tile 11 and the transparent base 2 is approximately one pixel size).

[0152] First modified embodiment It has been shown that the lenslet design can be more varied to combat myopia, for example, diffusing elements can be used.

[0153] As such, the present disclosure also allows for the construction of myopic optical control elements using translucent materials.

[0154] The translucent material can be easily formulated by adding fillers within the curable material, resulting in a translucent material that can control myopia.

[0155] Second Variant Embodiment It has also been shown that the lenslet design can be more diverse to combat myopia, for example, diffractive elements can also be used.

[0156] Diffraction can be produced in the disclosed method by modifying the DLP, its focusing and defocusing.

[0157] Diffraction can occur from the DMD.

[0158] Diffraction caused by pixels / DMD / DLP is usually considered an optical defect in conventional additive manufacturing of optically transparent substrates.

[0159] Optional Embodiments Just as it is possible for an optical element (microstructure) to be constructed on another optical element (e.g., on a transparent base as described above), it is also possible for the microstructure (lenslet) to be encapsulated in an additional microstructure (e.g., in a polymer matrix), referred to herein as an "encapsulation layer" 4.

[0160] This can be done by the same process as above, but the encapsulation layer 4 should have a different refractive index to maintain optical functionality.

[0161] To this end, after constructing the microstructure 3 (a set of lenslets), the curable material 14 is modified and the process is applied with a new (second) digital material model and ultimately other hardware specifications.

[0162] Thus, the container 13 containing the first hardenable material 14 is emptied.

[0163] Optionally, the method includes arranging the containers.

[0164] The same container 13 is then filled with the second curable material.

[0165] Step 6 can also be applied to the optical device 1 thus obtained later. [Example]

[0166] Composition of the resin used for the microstructure 3 containing the lenslets (refractive index in the solid state: 1.72X):

[0167] [Table 2]

[0168] Its hardening characteristics also follow the Jacobs equation.

[0169] As a result, Ec=25.2 mJ and Dp=12 μm.

[0170] The calculated image applied to a refractive spherical lenslet (matrix ML2D junction P4D, λ=550 nm, dn=0.073, diameter=0.6 mm, 10 μm pixel size, 4k projector) is shown in FIG. 15.

[0171] The exposure time is set to, for example, 38.978 seconds.

[0172] The transparent base with the microstructures 3 is then rotated to remove the residual material 14 .

[0173] After this first microstructure 3 is formed (ie, the formation of the lenslets), the resin is modified in the following examples.

[0174] Composition of the resin used to encapsulate the lenslets (solid state refractive index: 1.498):

[0175] [Table 3]

[0176] Its curing characteristics also follow the Jacobs equation (EC=21 mJ, Dp approximately 0.39 μm).

[0177] The calculated image applied (for Cx=500 mm, lens diameter=70 mm) is shown in Figure 16 for a refractive spherical lenslet (35 μm pixel size, 4k projector).

[0178] In this exemplary embodiment, the exposure time is set to 48.75 seconds.

[0179] As such, the lenslets are encapsulated in a CX500mm design with an arrow (thickness at the center of the encapsulation layer) of 1.227mm.

[0180] It is worth noting that the calculated image takes into account the first microstructure 3, since the height (thickness) of the material 14 has been pre-polymerized and the light path has been corrected accordingly.

[0181] It is also worth noting that the calculated image should take into account, if applicable, the design of the transparent base and its optics: in effect, the transparent base modifies the projected pattern.

[0182] It should also be noted that the encapsulation induces an increase in the overall height design of the microstructure on the transparent base, which is an advantage for the process used here, since the thinner the microstructure, the more difficult it is to ensure polymerization precision.

[0183] This is the case, for example, for spherical lenslets.

[0184] For a spherical lenslet, compared to an unencapsulated lens of 2.75 dp and size 0.6 mm, as previously defined as diopter 1.498 / air (index difference 0.498), this is now over 2 times smaller since there is an index difference of 0.23 between the two clear bases with RI=1.72 and 1.49.

[0185] Therefore, the curvature of the encapsulated spherical lenslet to be manufactured must be at least twice as small, so that the sag of the spherical lenslet will be at least twice as large to achieve the same optical power of +2.75 dp after encapsulation.

[0186] For the same reason, it may be necessary to increase the Fresnel curvature to compensate for the effect of the refractive index difference, except that the refractive power of the lenslets is not rebalanced, but the efficiency ratio of both the main diffraction orders 0 and +1 (the refractive power at 550 nm remains constant due to the specific properties of the π Fresnel design).

Claims

1. A method for manufacturing an optical device (1) comprising a microstructure (3) from a transparent base (2), comprising: - obtaining said transparent base (2) with a free surface (21) on at least a portion of which a microstructure (3) is to be created, said free surface (21) having a predetermined curvature; - immersing at least said portion of said free surface (21) in a first hardenable material (14); - determining a first greyscale image (12) representative of the microstructure (3) to be created on the portion of the free surface (21); - projecting said first greyscale image (12) onto said portion of said free surface (21) of said transparent base (2) by means of ultraviolet light having a predetermined intensity; - curing a volume of the first curable material (14) covering said portion of the free surface (21) by irradiating said volume of the first curable material (14) through said transparent base (2) with a first greyscale image (12) of ultraviolet light, which provides different doses of light to a portion of said free surface (21), thereby forming said microstructures (3) on said portion of the free surface (21) of the transparent base (2); A method comprising:

2. 2. The method of claim 1, wherein the step of determining the first grayscale image comprises determining the height of the microstructure (3) at each pixel compared to a free surface (21).

3. 3. The method according to claim 1 or 2, comprising the steps of displacing the transparent base (2) relative to a grayscale image projection tile, and generating a different first grayscale image according to the displacement of the transparent base.

4. The method according to any one of claims 1 to 3, comprising removing at least a portion of the remaining first curable material (14) from the optical device (1) by rotating at least the optical device (1).

5. 5. The method according to any one of claims 1 to 4, comprising the steps of cleaning at least a surface of the microstructure (3) with a cleaning material, removing the surface of the microstructure (3) from the cleaning material, and rotating the optical device (1).

6. The method according to any one of the preceding claims, comprising the step of immersing at least the surface of the microstructure (3) in a second curable material.

7. 7. The method of claim 6, comprising the steps of: emptying a container containing the first curable material (14) into which at least one surface of the microstructure (3) is immersed while the transparent base (2) is maintained by a blocker; and filling the container with the second curable material while the transparent base (2) is maintained on the blocker.

8. 8. The method according to claim 6 or 7, further comprising the steps of: cleaning at least the surface of the microstructure (3) with the second curable material; removing the surface of the microstructure (3) from the second curable material; and rotating the optical device (1) before immersing at least the surface of the microstructure (3) in the second curable material.

9. - determining a second greyscale image according to the surface of the microstructure (3) and according to a design of an encapsulation layer (4) to be created to encapsulate at least a part of the microstructure (3); - projecting said second greyscale image onto at least said part of said surface of said microstructure (3) using UV light; - irradiating a volume of the second curable material through the transparent base and the microstructures (3) with a second grayscale UV light image, thereby curing the volume covering the portion of the surface of the microstructures (3), thereby encapsulating at least the portion of the microstructures (3); The method according to any one of claims 6 to 8, comprising:

10. An optical device (1) manufactured by the method according to any one of claims 1 to 9, characterized in that it comprises a microstructure (3) formed on at least the surface of a transparent base (2).

11. 11. The optical device (1) according to claim 10, comprising an encapsulation layer (4), wherein the microstructure (3) is encapsulated under the encapsulation layer (4).

12. 12. The optical device (1) according to claim 10 or 11, wherein the microstructures (3) comprise at least one of lenslets, diffusing elements, diffractive elements, and / or π-Fresnel lenslets.

13. A system for manufacturing an optical device (1) according to any one of claims 10 to 12, said system being configured to carry out the method according to any one of claims 1 to 9, said system comprising: a container (13) for containing a volume of hardenable material (14); a DLP projector (10) comprising: a UV light source configured to emit UV light at a predetermined intensity; and a digital micromirror device configured to use the UV light to project at least one grayscale image onto a projection tile toward the inside of the container; A system comprising:

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