Method for manufacturing an optical device comprising a microstructure, manufacturing system for performing such a method, and optical device obtained thereby

Abstract

A method for manufacturing an optical device (1), the method comprising the steps of: obtaining a transparent substrate (2) comprising 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 a first grayscale image (12) onto the portion of the free surface (21) by UV light having a predetermined intensity; the volume of the first curable material (14) is cured on the portion of the free surface (21) by irradiating the volume of the first curable material (14) through the transparent substrate (2). An optical device (1) manufactured by such a method, and a system for manufacturing such an optical device (1) by such a method.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing an optical device comprising a microstructure, and a manufacturing system configured to perform such a method. The present disclosure also relates to the optical device obtained thereby. Background Art

[0002] The document WO 2019002905 discloses a method for producing an optical device from a volume of a curable composition, wherein a portion of the volume is polymerized by irradiating the outer surface of the volume and optionally the upper part previously polymerized with light. In this method, the light intensity of the light irradiation varies on the outer surface due to the use of a spatial light modulator (i.e., the spatial light modulator locally modifies the light intensity on the surface) and may also vary over time. Therefore, the curable composition is continuously polymerized part by part.

[0003] On the other hand, in optical devices such as ophthalmic lenses, specific surface morphologies (including microstructures) can be used to provide specific effects and / or control various visual impairments.

[0004] For example, in ophthalmic lenses, microlenses can be used to slow the progression of myopia, particularly in children.

[0005] Therefore, it is desirable to provide a method for manufacturing an optical device including a specific surface morphology (such as a microstructure), which method can be flexible in use, especially more flexible than other techniques (such as diamond turning or lithography, or injection molding or casting processes, etc.) in forming small lenses or other shapes, and the method is capable of making such microstructures on the surface or ultimately encapsulating such microstructures inside an optical device (such as a lens). Summary of the invention

[0006] According to a first aspect, there is provided a method for manufacturing an optical device comprising a microstructure from a transparent substrate, the method comprising the following steps:

[0007] - obtaining a transparent substrate comprising a free surface on at least a portion of which the microstructure is to be created, the free surface having a predetermined curvature;

[0008] - immersing at least the portion of the free surface in the first curable material;

[0009] - determining a first grayscale image representing a microstructure to be created on the portion of the free surface;

[0010] - projecting a first grayscale image onto the portion of the free surface of the transparent substrate by means of ultraviolet light having a predetermined intensity;

[0011] -Curing a certain volume of first curable material on the portion of the free surface by irradiating the volume of first curable material through the transparent substrate with a first grayscale image of ultraviolet light providing different doses of light on that portion of the surface, thereby forming a microstructure on that portion of the free surface of the transparent substrate.

[0012] The transparent substrate herein includes, for example, substrates and films.

[0013] "Transparent" means here that the substrate allows at least 1%, preferably at least 80%, of light to pass through at a given wavelength, here in particular at least UV light. For example, 1000 mw / cm 2 1% is 10mw / cm 2 , which is already very good for some chemicals. This ratio can depend a lot on the chemical's reactivity under UV.

[0014] The first grayscale image, projected by, for example, a DMD (digital micromirror device), plays a role similar to a projected pattern.

[0015] Thus, the first grayscale image enables at least a portion of the free surface to be illuminated with a light beam with a predetermined exposure time and a predetermined intensity. Depending on the grayscale level at a point (pixel) in the image, a specific corresponding light dose is provided to the corresponding point of the surface so that the microstructure made of the first curable material cured at this point of the surface has a corresponding height.

[0016] It is worth noting here that grayscale or grayscale refers to a pattern of light in the UV range.

[0017] It is thus possible to avoid that the projection device modulates the grey level over time.

[0018] This method thus enables forming a modified surface comprising microstructures on at least a portion of a transparent substrate by volumetric additive manufacturing in a single step without the need for layer manufacturing.

[0019] Due to the first greyscale image, microstructures having different heights relative to the free surface of the transparent substrate can be simultaneously produced in the same step.

[0020] Thus, the method locally provides different doses (e.g. measured in millijoules (mJ)) rather than different intensities (e.g. measured in milliwatts per square centimeter (mW / cm 2 )). The intensity of the light is the same (it does not change or changes very little), but the distribution of the light over parts of the surface differs in time due to the grayscale and, according to an exemplary embodiment, due to the associated vibrations of the micromirrors of the DMD.

[0021] Here, in other words, the design to be produced is obtained using a calculated image pattern and a calculated irradiation time. The two are inextricably linked: in order to change the design to be produced, both must be changed.

[0022] This approach thus allows for the fabrication of individualized or customized optical devices (eg, lenses).

[0023] According to one embodiment, the step of determining the first greyscale image comprises the step of determining the height of the microstructure relative to the free surface at each pixel.

[0024] According to one embodiment, the method comprises the steps of shifting the transparent substrate relative to the grayscale image projection patch and generating another first grayscale image according to the shifting of the transparent substrate.

[0025] According to one embodiment, the method comprises the step of removing at least part of the remaining first curable material from the optical device by at least spinning the optical device.

[0026] According to one embodiment, the method comprises the steps of washing at least the surface of the microstructure with a washing material, removing the surface of the microstructure from the washing material, and spinning the optical device.

[0027] For example, such a step is performed before the step of immersing at least the surface of the microstructure in the second curable material as mentioned below.

[0028] According to one embodiment, the method comprises the step of immersing at least the surface of the microstructure in a second curable material.

[0029] According to one embodiment, the method comprises: a step of emptying a container containing a first curable material in which at least one surface of the microstructure is immersed while maintaining the transparent substrate by a stopper; and a step of filling the container with a second curable material while the transparent substrate is held on the stopper.

[0030] According to one embodiment, the method comprises: before the step of immersing at least the surface of the microstructure (3) in the second curable material, a step of washing at least the surface of the microstructure (3) with the second curable material, a step of removing the surface of the microstructure (3) from the second curable material, and a step of spinning the optical device (1).

[0031] According to one embodiment, the method comprises the following steps:

[0032] - determining a second grayscale image based on the surface of the microstructure (3) and the design of an encapsulation layer (4) to be produced for encapsulating at least a part of the microstructure (3);

[0033] - projecting a second greyscale image onto at least the portion of the surface of the microstructure (3) using UV light;

[0034] - Encapsulating at least that part of the microstructure (3) by irradiating a volume of second curable material through the transparent substrate and the microstructure (3) with a second greyscale UV light image, causing said volume to cure on that part of the surface of the microstructure (3).

[0035] According to a second aspect, there is provided an optical device manufactured by the method as described above.

[0036] Since the micromirrors in a DMD are not perfectly connected, corresponding discontinuities may be found in the material, which can ultimately be detected by a powerful machine.

[0037] Furthermore, some designs are difficult or nearly impossible to obtain in any other way; for example, diffractive lenslets on a surface or encapsulated lenslets would be difficult to manufacture using molds.

[0038] The above-described method of the invention makes it possible to produce in one go a product which would require several moulding / reverse moulding steps to obtain the same product.

[0039] For example, an epi-fresnel lens would be a design that would be difficult to achieve otherwise.

[0040] For example, the optical device includes a microstructure formed on at least one surface of a transparent substrate.

[0041] For example, the optical device includes an encapsulation layer, and the microstructure is encapsulated below the encapsulation layer.

[0042] For example, the microstructure includes at least one of a lenslet, a diffusing element, a diffractive element and / or a Pi-Fresnel lenslet.

[0043] According to a third aspect, there is provided a system for manufacturing an optical device as described above.

[0044] For example, the system is configured to implement the method as described above.

[0045] For example, the system mainly includes:

[0046] - a container for containing a volume of curable material,

[0047] - a DLP projector, the DLP projector comprising: a UV light source configured to emit UV light at a predetermined intensity; and

[0048] - a digital micromirror device configured to project at least one grayscale image in the form of a projection tile toward the interior of the container using UV light.

[0049] The optional features presented above in connection with the proposed method may also be applicable to such a system.

[0050] The present disclosure may be used with any type of optical device, such as an optical lens or an ophthalmic component or device.

[0051] Non-limiting examples of ophthalmic elements include corrective and non-corrective lenses, including single vision lenses or multifocal lenses, which may be segmented or non-segmented, and other elements used to correct, protect, or enhance vision, including but not limited to magnifying lenses and protective lenses or goggles, such as those found in goggles, glasses, swimming goggles, and helmets.

[0052] Therefore, the above embodiment may have the following advantages:

[0053] - Any type of microstructure (lenses: refractive, diffractive, diffuse) on a flat or curved transparent substrate;

[0054] - Microstructures can be made directly on any transparent substrate (lens or other element, such as molds (glass or plastic), inserts (glass or metal), wafers, films, etc.);

[0055] - microstructures with a refractive index different from that of the transparent substrate (e.g. for encapsulation);

[0056] - making the optical device into at least two parts with different refractive indices for encapsulation of microstructures;

[0057] - Personalized microstructure (power, density, array type, area on the lens) according to the wearer (e.g. according to his sensitivity to contrast reduction, his activity type, the shape of his retina, the rate of progression of his myopia (or other vision disease, or refractive error), etc.);

[0058] - Provides a non-layered process.

[0059] In the case of encapsulation, the following additional advantages can be provided:

[0060] -The microstructure is protected by the encapsulation layer;

[0061] - Chemicals used for microstructures do not necessarily need to have conventional thermomechanical properties suitable for ophthalmic applications (HDT ~ 80 °C, E> 2 GPa, etc.) as they will be embedded inside a suitable encapsulation layer. This enables greater flexibility, typically enabling the design of chemicals with high refractive indices;

[0062] - Because the encapsulation layer can provide a smooth top surface, there is no problem of hard coating deposition due to the design of the microstructure;

[0063] - Microstructures can achieve very high refractive indices with materials that do not necessarily meet the requirements for ophthalmic applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Advantageous embodiments are described below by way of non-limiting examples and with reference to the accompanying drawings.

[0065] Figure 1 An exemplary embodiment of an optical device is shown, in which a microstructure is formed on a surface of a transparent substrate;

[0066] Figure 2 An exemplary embodiment of an optical device is shown, wherein a microstructure is formed inside the optical device;

[0067] Figure 3 An exemplary embodiment of an optical device including lenslets is diagrammatically illustrated, wherein the aspheric lenslets are arranged in concentric rings;

[0068] Figure 4 Diagrammatically showing a single focus lenslet;

[0069] Figure 5 Diagrammatically showing a bifocal lenslet;

[0070] Figure 6 A Pi-Fresnel lenslet is diagrammatically shown;

[0071] Figure 7 Indicates the use for manufacturing Figure 1 or Figure 2 An exemplary embodiment of a system of optical devices is presented;

[0072] Figure 8 A manufacturing system according to an exemplary embodiment is shown;

[0073] Fig. 9 Diagrammatically illustrating the profile of a lenslet formed on a surface of a transparent substrate according to an exemplary embodiment;

[0074] Fig.10 Diagrammatically illustrating the profile of a lenslet formed on a surface of a transparent substrate according to another exemplary embodiment;

[0075] Fig.11 The experiment to confirm the parameters (Ec and Dp) of Jacob's equation is shown in the figure;

[0076] Fig.12 Grayscale images of a spherical lenslet (pixel size 10 μm) used to form a refractive lens for myopia are shown;

[0077] Fig.13Grayscale images of a diffractive Pi-Fresnel lenslet (pixel size 5 μm) used to form myopia-targeted lenses are shown;

[0078] Fig.14 The relative displacement of the grayscale image projection block relative to the transparent substrate is shown when the projection block is smaller than the transparent substrate;

[0079] Fig.15 Calculated images for a refractive spherical lenslet (pixel size 10 μm, 4k projector) are shown;

[0080] Fig.16 Calculated images are shown for producing a substrate curvature radius CX = 500 mm, mirror diameter = 70 mm using a DLP with a pixel size of 35 μm and a resolution of 4k. DETAILED DESCRIPTION

[0081] The following disclosure relates to additive manufacturing techniques for making ophthalmic lenses that slow the progression of myopia (e.g., myopia progression in children).

[0082] For example, the manufacturing of lenslets by a specific technique of volumetric additive manufacturing is described herein.

[0083] The disclosed method is able to provide any surface shape to an optical device, in particular an ophthalmic lens using lenslets for myopia control. However, the disclosed method can be extended to other topics than myopia control, for example depending on the created microstructures.

[0084] It should be noted that an ophthalmic lens may be any ophthalmic device for eyeglasses or other devices that are adapted to a wearer and have ophthalmic properties.

[0085] It should also be noted that the additive manufacturing method may be performed according to any existing suitable technique, such as those included in the definition given in reference ISO / ASTM 52900:2021 or corresponding references.

[0086] Structural aspects of the optical lens will be described later. The optical lens includes microstructures that may be arranged on the convex front (also called object side) major surface or the concave rear (also called eyeball side) major surface of the optical lens or on both major surfaces.

[0087] The microstructure comprises at least one small lens.

[0088] The lenslets modify the power of the input light by modifying the power of the input light or the phase of the input light, thereby producing output light.

[0089] The lenslets may form protrusions and / or depressions on the major surface they are arranged on. The outline of the lenslets may be circular or polygonal, for example hexagonal.

[0090] The lenslets may be spherical, toric or have an aspherical shape, rotationally symmetric or not. The lenslets may have a single focus, or a cylindrical power, or a non-focused point. In a preferred embodiment, the lenslets may be used to prevent the progression of myopia or hyperopia. In this case, the base lens substrate comprises a base lens providing a power for correcting myopia or hyperopia, and the lenslets may provide a power greater than the power of the base lens if the wearer is myopic, or a power less than the power of the base lens if the wearer is hyperopic, respectively.

[0091] The lenslets can also be Fresnel structures, diffractive structures such as lenslets defining each Fresnel structure, permanent technical protrusions or phase shifting elements. The lenslets can also be refractive optical elements such as microprisms and light diffusing optical elements such as small protrusions or recesses, or any type of element that creates roughness on the substrate.

[0092] The lenslet may also be a π-Fresnel lenslet as described in US2021109379 A1, i.e. a Fresnel lenslet 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 a lenslet comprises a structure having a discontinuous shape. In other words, the shape of such a structure may be described by a height function which exhibits a discontinuity, or a derivative thereof, in terms of a distance from a reference plane of a main surface of the optical lens to which the lenslet belongs.

[0093] The small lens of the present invention may have an outer shape that can be inscribed in a circle having a diameter greater than or equal to 0.5 micrometers (μm) and less than or equal to 2.5 millimeters (mm).

[0094] The lenslets of the present invention have a maximum height measured in a direction perpendicular to the main surface on which they are arranged, which is greater than or equal to 0.1 μm and less than or equal to 50 μm. The main surface can be defined as a surface including the center point of each microstructure, which can be a plane, a spherical surface, a sphero-cylindrical surface, or even a composite surface. This main surface can be a virtual surface when the microstructures are embedded in the lens, or close to or identical to the physical outer surface of the ophthalmic lens when the microstructures are not embedded. The height of the microstructure can then be determined using a local axis perpendicular to this main surface, and the difference between the maximum positive deviation from the main surface minus the minimum negative deviation along this axis is calculated for each point of the microstructure.

[0095] The lenslets may have a periodic or pseudo-periodic layout, but may also have random positions. Exemplary layouts of lenslets may be a grid with a constant grid step size, a honeycomb layout, multiple concentric rings, contiguous (eg no spaces between microstructures).

[0096] These structures can provide light wavefront modifications in terms of intensity, curvature, or light deviation, wherein the intensity of the wavefront is configured such that the structure can be absorptive and can locally absorb the wavefront intensity in the range of 0% to 100%, wherein the curvature is configured such that the structure can locally modify the wavefront curvature in the range of + / -20 diopters, and the light deviation is configured such that the structure can locally scatter light in the angular range of + / -1° to + / -30°.

[0097] The distance between structures can range from 0 (adjoint) to 3 times the distance between structures (separated microstructures).

[0098] In this example, first combine Figures 1 to 6 Describes some types of lenslet designs and lenses as optical devices.

[0099] Nowadays, there are various design solutions for optical devices (such as ophthalmic lenses or contact lenses) that can slow down the progression of myopia. Examples are based on the use of microstructures (such as optical lenslets) that generate a signal of out-of-focus or unfocused light in front of the retina. Such lenslets slow down the process of eye elongation, the so-called "myopia" process.

[0100] Such a microstructure is formed on the surface of the transparent substrate 2 of the optical device 1 by volume additive manufacturing, for example (eg Figure 1 ), or formed inside the optical device 1 (such as Figure 2 shown).

[0101] More specifically here, Figure 2 An optical device 1 including a transparent substrate 2 and a microstructure 3 is shown. The microstructure can even be formed on the surface of the transparent substrate 2 from material A in a first step and then encapsulated in another material (material B) in a subsequent second step, so that the microstructure made of material A is finally formed inside the optical device 1, which then includes the transparent substrate 2, the microstructure 3 and the encapsulation part 4 covering the microstructure 3.

[0102] According to one exemplary embodiment, the elements of the microstructure may be arranged in concentric rings and include aspherical lenslets that produce multiple volumes of unfocused light in front of the retina.

[0103] Figure 3 Such an arrangement is shown diagrammatically in .

[0104] According to another exemplary embodiment not shown here, the lenslets are in a pattern of spherical lenslets on a hexagonal array and arranged in "independent islands" that produce multiple defocuses in front of the retina.

[0105] Other studies on diffuse / scattering lenslets have also demonstrated promising results in terms of myopia control efficacy.

[0106] Microstructures of other shapes also show value in controlling different vision diseases.

[0107] It is therefore of value to be able to produce optical devices with microstructures, either on the surface of the element or within the element itself, as the case may be.

[0108] Also of value is the ability to fabricate microstructures with very different shapes (e.g., diffusing lenslets, scattering lenslets, diffusing or scattering dots, refractive lenslets (e.g., Figure 4 The single focus lenslet shown, or Figure 5 The bifocal lenslets, or toric lenslets shown), diffractive lenslets (e.g. Figure 6 The Pi-Fresnel lenslets shown) etc.) and optionally an optical device of a second optical function for myopia control, which second optical function can be spherical or aspherical, or other shapes.

[0109] For example, an optical device may have a lenslet with a "gradient law", meaning a variation 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 eccentricity)), or may have a mixture of at least two different forms of lenslets.

[0110] Documents WO 2022112531 A2, WO 2022112533 ​​A1 or WO 2022112534A1 disclose refractive lenslets, diffractive lenslets, and diffuse lenslets.

[0111] However, all of these shapes would be difficult to form in an optical device using conventional optical device manufacturing methods and corresponding systems.

[0112] Combination Figures 7 to 16 Exemplary embodiments of methods and corresponding systems for manufacturing such optical devices are described.

[0113] In the described embodiments, a volumetric additive manufacturing method is used to manufacture microstructures on a predetermined surface.

[0114] The method uses a DLP projector 10 to project a UV light grayscale image 12 onto a projection block 11 to cure a volume of material 14 (e.g., resin) at a specific / predetermined location. In other words, the grayscale image 12 is capable of selectively activating the curing of the material 14 in a predetermined area. Therefore, the higher the light dose provided to a point, the thicker the voxel of the cured material 14 (as described in the Jacobs equation, see below for details).

[0115] For example, an image pattern is generated (calculated) to form an image document file (such as .tiff, .jpg, .png document files, etc.). It is a grayscale image that will be loaded into the DLP composed of LEDs and DMDs. The DMD is like a "grid" that can "structure" the light from the LED. In other words, the DMD "pixels" or "shapes" the light flow. Each micromirror of the DMD can be controlled individually. For a grayscale level of 256 (white), the micromirror (or pixel) will remain "on" (light flows through). For a grayscale level of "0", the micromirror will remain off (blocking the light flux). For a grayscale level of 128, the micromirror will alternate between "on" and "off" states, providing half the light dose compared to a grayscale level of 256.

[0116] Figure 7 An exemplary embodiment of a system for performing such a method is shown.

[0117] For example, a system for manufacturing an optical device includes such a DLP projector 10 .

[0118] The DLP projector 10 includes a light source configured to emit light of predetermined intensity and within a prescribed wavelength range, for example, within the UV (ultraviolet) range, such as wavelengths between 190 nm and 550 nm, more specifically between 300 nm and 420 nm.

[0119] To this end, the light source comprises, for example, an LED for emitting light in the desired wavelength range.

[0120] For example, the DLP projector 10 here includes a UV video projector.

[0121] The DLP projector 10 is also configured to provide a desired grayscale light pattern (image) 12 , which is displayed in the projection tile 11 .

[0122] To this end, the DLP projector 10 includes a DMD (Digital Micromirror Device).

[0123] The DMD includes hundreds or even thousands of micromirrors arranged in an array. One micromirror corresponds to one pixel in the projected image. The micromirrors can be rotated individually to be positioned in an "on" position or an "off" position. In the "on" position, light from the light source is reflected to the mirror, making the pixels of the image appear bright, while in the "off" position, the light is directed elsewhere, that is, not directed into the projection block 11, making the pixels appear dim. To produce grayscale, the micromirrors are switched on and off at a predetermined frequency, and the ratio of the "on" time to the "off" time determines the chromaticity produced (also known as "binary pulse width modulation").

[0124] Due to the grayscale, intermediate values ​​of light energy can be provided.

[0125] Therefore, the light intensity remains almost the same, while the light dose varies pixel by pixel.

[0126] For example, screen projectors such as DLP (digital light processor) can provide different levels of gray on a 2D plane. The micromirrors of the DMD embedded inside the DLP can vibrate at up to 256 or even 1024 different frequencies, thus generating up to 256 or even 1024 different light energies on a single projected tile (i.e., an image), thereby generating 256 or even 1024 gray levels from "black" to "white", as well as 254 (or 1022) intermediate gray levels.

[0127] For example, the grayscale image 12 that must be projected on a surface to generate the microstructure is calculated from a digital material (resin) model that takes into account the evolution of thickness and grayscale levels over time when cured under light.

[0128] As an example of a digital material model, a modified Jacobs equation may be used to predict the grayscale to be provided corresponding to the height of a voxel to be aggregated within a predetermined time.

[0129] Accordingly, the DLP projector 10 further comprises a container 13 for containing a certain volume of curable material 14 .

[0130] In order to grow the microstructure 3 on the surface 21 of the transparent substrate 2 , the surface 21 is positioned relative to the projection pattern 12 .

[0131] Light emitted by the light source passes through the transparent substrate 2 to the curable material 14 to grow microstructures on the surface 21 .

[0132] According to an interesting embodiment, the system further comprises a stopper configured to maintain at least the transparent substrate of the optical device 1 in a predetermined position.

[0133] Figure 8 A flow chart of the method steps for producing the designed optical device is presented.

[0134] Describes the Figure 8 Flowchart of the production of two exemplary embodiments of adjoining lenslets: a refractive spherical lenslet and a diffractive Pi-Fresnel.

[0135] For example, the transparent substrate may be an optical element made of, for example, MR7, MR8, ORMA, or the like.

[0136] In this example, biplanar ORMA (refractive index RI = 1.498) was chosen as the transparent substrate.

[0137] It is worth noting that the transparent substrate must transmit light of the minimum energy of the emitting light source in order to be able to cure the material (resin) with which the microstructure will be formed on the surface of the transparent substrate. In this regard, the transparent substrate and / or the light source can be adapted according to the optical device to be manufactured.

[0138] Step S1: Design to be produced

[0139] The first design

[0140] In step S1 , the design to be produced is a shape that has to be solidified on a transparent substrate.

[0141] On the transparent substrate, according to the first design, it is desirable to form a refractive spherical lenslet.

[0142] Fig. 9 A cross section of such a microstructure 3 is diagrammatically represented.

[0143] In this figure, the horizontal axis represents the length of the microstructure 3 (particularly the diameter of the lenslet), and the vertical axis represents the height of the microstructure 3 (the height of the lenslet).

[0144] Thus, in this figure, nine lenslets are represented as well as two half lenslets on either side.

[0145] All lenslets are identical here, having the same height and the same diameter.

[0146] Second design

[0147] On the above transparent substrate, according to the second design, it is desired to form a diffractive Pi-Fresnel small lens.

[0148] Fig.10 Such an outline is shown diagrammatically in .

[0149] and Fig. 9 Same, Fig.10 The horizontal axis represents the length of the microstructure 3 , and the vertical axis represents the height of the microstructure 3 .

[0150] Therefore, in Fig.10 In FIG. 3 , three diffractive Pi-Fresnel lenslets are shown.

[0151] All of these lenslets are identical here, having the same height and the same diameter.

[0152] Step S2a: Hardware Specifications

[0153] The projector used here is combined with Figure 7 The system described has the following specifications:

[0154] - Resolution: 3840×2160 pixels (4k)

[0155] -Pixel size: 35μm or 10μm or 5μm (the pixel size is set with the (de)focusing system according to the required accuracy)

[0156] - Projection block 11: 134.4×75.6mm, or 38.4mm×21.6mm, or 19.2×1.08mm

[0157] -Emission wavelength of LED light source: 365nm

[0158] -LED light intensity: 10mW / cm 2

[0159] Step S2b: Digital material model

[0160] In this example, the Jacobs equation is used as the numerical material model because it is combined with Fig.11 The corresponding experiments described are well adapted.

[0161] However, it is important to note that digital material models do not necessarily follow the Jacobs equation. This depends a lot on the "material response" under exposure. Therefore, another equation model can be used instead of the Jacobs equation.

[0162] Therefore, the digital material model adapted to the resin for the present exemplary embodiment described here is based on the following Jacobs equation:

[0163] E(z)=Ec*exp[z / Dp]

[0164] in:

[0165] - Z is the thickness of the material to be polymerized (in μm), corresponding to the height compared to the surface of the transparent substrate;

[0166] - E(z) is the energy dose required to polymerize a material with a thickness of z, expressed in millijoules per square centimeter (mJ / cm 2 )

[0167] - Ec is the minimum energy required to polymerize a non-zero thickness (i.e., energy threshold), in millijoules; here, Ec = 10.9 mJ;

[0168] - Dp is the light penetration depth in micrometers; here, Dp = 11 μm.

[0169] Light penetration depth (Dp) indicates the distance light travels before being absorbed by about 35% in the resin.

[0170] The critical energy (Ec) represents the minimum light dose required to transform the material from a liquid state to a solid state.

[0171] This means that in order to polymerize the material on the transparent substrate, a light dose (E) higher than the critical energy (Ec) is required.

[0172] On the other hand, the provided energy (light dose) is also a function of the gray level, intensity, and time of light irradiation, as shown below:

[0173] E = GS * I * t

[0174] Where:

[0175] - GS is the gray level, ranging from 0 to 1,

[0176] - I is the intensity of the emitted light, in milliwatts per square centimeter (mW / cm 2 )

[0177] - t is the exposure time, in seconds (s).

[0178] By substituting the energy dose with an expression containing the gray value, we get:

[0179]

[0180] Where

[0181] In this example, Ec and Dp are determined by linearizing the Jacobs equation, which involves measuring the thickness polymerized at different light doses.

[0182] For example, an experiment is conducted as follows, as Fig.11 illustrated:

[0183] (i) Place the transparent substrate 2 (here including a glass plate transparent to UV light) on the curable material 14 (here including a liquid resin), as Fig.11 shown in A).

[0184] (ii) Project square UV light (e.g., 365 nm in this example) through the transparent substrate 2.

[0185] (iii) For different irradiation times t1, t2, t3, and t4 (where t1 < t2 < t3 < t4), repeat steps (i) and (ii), as Fig.11 shown in B).

[0186] Then measure the polymerized thickness with a caliper,

[0187] which shows that the higher the irradiation time (light dose), the thicker the polymerized structure.

[0188] (iv) Finally, a graph is plotted showing the relationship between the thickness of the polymer (in mm) and ln(E) (the "working curve"), e.g. Fig.11 C) and were fitted with the Jacobs equation to obtain Ec and Dp.

[0189] Composition of the materials used 14

[0190] In this example, the material 14 to be polymerized for forming the microstructure 3 is a resin, the properties of which are obtained when the compound is formulated as follows:

[0191] Chemical compounds effect Ratio (g / L) Acrylate Monomer / oligomer - Phenazine UV absorbers 5.188 Avobenzone UV absorbers 2.297 Omnirad 819 Photoinitiator 5.5

[0192] Due to the relatively high content of UV absorbers, special mixing has to be applied.

[0193] The acrylate monomer / oligomer resin was heated to 50°C and then the UV absorber was added gradually with vigorous stirring over the next 3 days.

[0194] Then, vigorous stirring was continued at 50°C for one week.

[0195] After one week, the resin was slowly cooled to 23°C and the photoinitiator was added and mixing continued for 24 hours.

[0196] The formulation was filtered with a 1 μm filter and the Dp was controlled.

[0197] The refractive index of the cured material (resin) is about 1.498, so that:

[0198] - for a diffractive Pi-Fresnel lenslet (as described above), with a focal power of 0 / +4 dp (λ=550nm);

[0199] - +2.75dp for the design of refractive spherical lenslets (described above);

[0200] - By varying the curvature and sag of the lenslets and adapting the manufacturing parameters accordingly, or using materials with different refractive indices, different lenslet optical properties can be defined in order to vary the focal power or the efficiency ratio at 550 nm, or it is also possible to envision using packaging solutions with smaller differences in refractive indices (described below).

[0201] Step S3: Image calculator

[0202] The image calculator is a process that takes into account the hardware specifications and digital material models to produce a "design to be produced" ( Figure 8 A numerical tool (e.g., a script) that converts step S1) into a grayscale image.

[0203] If the projection image block 11 is smaller than the entire design to be produced (e.g. Fig.14 ), the image calculator also cuts the image for sequential projection.

[0204] Step S4: Load the grayscale image to be projected into the DLP

[0205] For illustrative purposes, Fig.12 and Fig.13 shows the method for forming Fig. 9 and Fig.10 The grayscale image of the small lens for myopia corresponds to the contour.

[0206] More specifically, Fig.12 Demonstrated for forming and Fig. 9 The grayscale image of the refractive spherical lenslet (pixel size is 10μm) corresponding to the outline of Fig.13 Demonstrated for forming and Fig.10 Grayscale image of a diffractive Pi-Fresnel lenslet (pixel size 5 μm) corresponding to the profile.

[0207] Step S5: Image projection

[0208] The generated at least one image is projected onto at least the surface 21 of the transparent substrate 2 that is in contact with the curable material 14 .

[0209] This step is also called "curing".

[0210] The image is projected according to the time calculated by the image calculator, for example:

[0211] - In the refractive spherical lenslet ( Fig.12 ) is 26.75 seconds

[0212] - In the diffractive Pi-Fresnel lenslet ( Fig.13 ) is 43.25s

[0213] When using a grayscale image to create microstructures, it may be necessary to time-share activate the grayscale image (i.e., illuminate the image) multiple times, particularly when the propagation front of the cured material (between the cured and uncured materials) releases a lot of thermal energy due to the polymerization process.

[0214] When printing high-resolution microstructures with high spatial frequency (such as Fresnel structures), the propagation of this front along the Z-axis (height compared to the transparent substrate surface) can cause diffraction / scattering, thereby changing the initial desired shape of the microstructure.

[0215] This results in unwanted light distribution in the further Z direction caused by constructive / destructive interference, which is difficult or even impossible to compensate by changing the illumination pattern.

[0216] Likewise, if it is desired to create a scattering / diffusing microstructure at a specific location of a transparent substrate, then for similar reasons it is desirable to activate the grayscale image when the propagation front reaches that location in order to limit unwanted light distribution in the propagation front.

[0217] As an example, if it is desired to provide a lens having a microstructure on one surface, it may be desirable to use a first grayscale image to create a propagation front corresponding to the focal length of the lens (low spatial frequency), and then, when the propagation front approaches the location of the desired microstructure, display a second grayscale image to create a propagation front corresponding to the microstructure.

[0218] In this case, the microstructures are positioned on the surface of the transparent substrate that is farthest from the light source.

[0219] Step S6: Cleaning and post-curing

[0220] After forming the microstructure 3, the method may further include the step of cleaning the surface of the optical device 1 thus obtained.

[0221] For example, the transparent substrate having the microstructure 3 is spun to remove the residual material 14 from the surface of the optical device 1 .

[0222] Case where the size of the projected image patch is smaller than the size of the surface on which the microstructure is to be formed

[0223] If the size of the projection image block 11 is smaller than the surface 21 of the transparent substrate 2 on which the microstructures (small lenses) must be formed, the manufacture of the optical device will be completed by a relative displacement of the projection image block 11 with respect to the transparent substrate 2. Fig.14 exhibit.

[0224] Relative movement can be sequential or continuous.

[0225] If the shift is continuous, you have to use a "video film", i.e. a sequence of images.

[0226] In this way, the grayscale image is regenerated by discretization of "pixelation" according to the displacement frequency of the projection block 11 and the theoretical shape of the microstructure (for example: the grayscale image is regenerated every time the relative movement between the projection block 11 and the transparent substrate 2 is approximately 1 pixel size).

[0227] First variant embodiment

[0228] It has been shown that the design of the lenslets can be more diverse in order to control myopia. For example, diffusing elements can be used.

[0229] In this manner, translucent materials may also be used in the present disclosure to construct optical control elements for myopia.

[0230] Translucent materials can be easily formulated by adding fillers to the curable material to obtain a translucent material capable of controlling myopia.

[0231] Second variant embodiment

[0232] It has also been shown that the design of the lenslets can be more diverse for controlling myopia. For example, diffractive elements can also be used.

[0233] Diffraction can be produced using the process of the present disclosure by varying the DLP, focusing the DLP, and blurring the DLP.

[0234] Diffraction can be produced by a DMD.

[0235] Typically, in conventional additive manufacturing of optically transparent substrates, diffraction generated by pixels / DMD / DLP is considered an optical defect.

[0236] Alternative Embodiments

[0237] Since another optical element (microstructure) can be built on an optical element (eg on a transparent substrate as described above), the microstructure (lenslet) can also be encapsulated in an additional microstructure (eg in a polymer matrix), which is then referred to here as an “encapsulation layer” 4 .

[0238] This can be done by the same process described previously, but in order to maintain the optical functionality, the encapsulation layer 4 should have a different refractive index.

[0239] To this end, after the microstructure 3 (lenslet group) is built, the curable material 14 is replaced and the process is applied using the new (second) digital material model and eventually the other hardware specifications.

[0240] The container 13 containing the first curable material 14 is thus emptied.

[0241] Optionally, the method comprises the step of placing the containers on a shelf.

[0242] The same container 13 is then filled with the second curable material.

[0243] Step 6 can also be applied to the optical device 1 subsequently obtained therefrom.

[0244] Example

[0245] Composition of the resin for the microstructure 3 including small lenses (refractive index: 1.72X in the solid state):

[0246] Chemical compounds effect Ratio (g / L) Acrylate Monomer / oligomer - Avobenzone UV absorbers 4.204 Omnirad 819 Photoinitiator 5.5

[0247] Its curing characteristics also follow the Jacobs equation.

[0248] The results were Ec=25.2 mJ, and Dp=12 μm.

[0249] Fig.15 Computational images applied for a refractive spherical lenslet are shown (Matrice ML2D with P4D, λ=550nm, dn=0.073, diameter=0.6mm, pixel size 10μm, 4k projector).

[0250] The irradiation time is set to, for example, 38.978 s.

[0251] Then, the transparent substrate having the microstructure 3 is spun to remove the residual material 14 .

[0252] After forming this first microstructure 3 (ie, forming the small lenses), the resin is replaced with the following example:

[0253] Composition of the resin used to encapsulate the small lens (refractive index: 1.498 in solid state):

[0254] Chemical compounds effect Ratio (g / L) Acrylate Monomer / oligomer - Avobenzone UV absorbers 0.013 Omnirad 819 Photoinitiator 5.5

[0255] Its curing characteristics also follow the Jacobs equation (Ec=21mJ, Dp is about 0.39μm).

[0256] Fig.16 An image of the calculation applied for a refractive spherical lenslet (pixel size 35 μm, 4k projector) is shown (lens diameter = 70 mm for CX = 500 mm).

[0257] In this exemplary embodiment, the irradiation time is set to 48.75 s.

[0258] In this way, the lenslet will be packaged to have a CX 500mm design with a sag (thickness at the center of the packaging layer) of 1.227mm.

[0259] It is worth noting that the calculated image takes into account the first microstructure 3, since the height (thickness) of the material 14 has previously been polymerized and therefore the optical path has been modified.

[0260] It is also worth noting that the calculated image should also take into account the transparent substrate design and its optical properties, as the case may be. In practice, a transparent substrate will cause the projected pattern to be modified.

[0261] It should also be noted that encapsulation leads to an increase in the height design of the overall microstructure on the transparent substrate. This is an advantage of the process used here, because the thinner the microstructure, the more difficult it is to ensure the accuracy of the polymerization.

[0262] This is the case, for example, for spherical lenslets.

[0263] On the spherical lenslet, here the refractive index difference between the two transparent substrates with RI=1.72 and 1.49 will be 0.23, less than half of the former, compared to the non-packaged lenslet of 2.75 dp and size 0.6 mm (refractive index difference of 0.498) as defined previously with a refractive power of 1.498 / air.

[0264] Therefore, in order to obtain the same +2.75 dp power after encapsulation, the encapsulated spherical lenslet to be manufactured would need to have a curvature that is at least half that of the unencapsulated one, and thus a sag that is at least twice that of the unencapsulated one.

[0265] For the same reasons, it may be necessary to increase the Fresnel curvature to compensate for the effect of the refractive index difference, but this is not to rebalance the focal power of the lenslet, but to rebalance the efficiency ratio of the two main diffraction orders 0 and +1 (the focal power at 550nm remains constant due to the specific characteristics of the Pi-Fresnel design).

Claims

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

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

3. The method according to any one of claims 1 or 2 comprises the steps of shifting the transparent substrate (2) relative to the grayscale image projection block and generating another first grayscale image according to the displacement of the transparent substrate.

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

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

6. Method according to any one of claims 1 to 5, comprising the step of immersing at least the surface of the microstructure (3) in a second curable material.

7. The method according to claim 6, comprising: A step of emptying a container containing the first curable material (14) in which at least one surface of the microstructure (3) is immersed while maintaining the transparent substrate (2) by a stopper; and a step of filling the container with the second curable material while the transparent substrate (2) is kept on the stopper.

8. The method according to any one of claims 6 or 7, comprising: Prior to the step of at least immersing the surface of the microstructure (3) in the second curable material, there are a step of at least washing the surface of the microstructure (3) with the second curable material, a step of removing the surface of the microstructure (3) from the second curable material, and a step of spinning the optical device (1).

9. The method according to any one of claims 6 to 8, comprising the steps of: - determining a second grayscale image based on the surface of the microstructure (3) and the design of an encapsulation layer (4) to be produced for encapsulating at least a part of the microstructure (3); - projecting said second grayscale image onto at least said portion of the surface of said microstructure (3) using UV light; - Encapsulating at least said part of said microstructure (3) by irradiating a volume of said second curable material through said transparent substrate and said microstructure (3) with a second greyscale UV light image, causing said volume to cure on said part of the surface of said microstructure (3).

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

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

12. An optical device (1) according to any one of claims 10 or 11, wherein: The microstructure (3) comprises at least one of a small lens, a diffusion element, a diffraction element and / or a Pi-Fresnel small lens.

13. A system for manufacturing an optical device (1) according to any one of claims 10 to 12, the system being configured to implement the method according to any one of claims 1 to 9, the system comprising: - a container (13) for containing a volume of curable material (14); - A DLP projector (10), comprising a UV light source and a digital micromirror device, wherein the UV light source is configured to emit UV light of a predetermined intensity, and the digital micromirror device is configured to project at least one grayscale image in the form of a projection tile toward the interior of the container using the UV light.

Images