阅读说明：本技术 用于通过增材制造来制造光学镜片的方法以及对应的中间光学元件 (Method for manufacturing an optical lens by additive manufacturing and corresponding intermediate optical element ) 是由 A·古罗 于 2019-09-24 设计创作，主要内容包括：一种用于通过增材制造来制造光学镜片(1)的方法,包括以下步骤：-沉积具有第一厚度(h-(271))的第一层(271),-将具有第二厚度(h-(273))的第二层(273)沉积到所述第一层(271)上,所述第二层(273)与所述第一层(271)形成第一微凸体(331),-沉积具有第三厚度(h-(275))的第三层(275),-将具有第四厚度(h-(277))的第四层(277)沉积到所述第三层(275)上,由此形成中间光学元件(5),所述第四层(277)与所述第三层(275)形成第二微凸体(333),-对所述中间光学元件(5)上的所述第一微凸体(331)和所述第二微凸体(333)进行光滑处理,由此形成所述光学镜片(1),其中,所述第二厚度(h-(273))和所述第四厚度(h-(277))不同。还描述了对应的中间光学元件。(A method for manufacturing an optical lens (1) by additive manufacturing, comprisingThe following steps: -depositing a layer having a first thickness (h) 271 ) Will have a second thickness (h) (271) 273 ) Is deposited onto the first layer (271), the second layer (273) forming first microprotrusions (331) with the first layer (271), -is deposited with a third thickness (h) 275 ) A third layer (275), -will have a fourth thickness (h) 277 ) Onto the third layer (275), thereby forming an intermediate optical element (5), the fourth layer (277) forming a second microprotrusion body (333) with the third layer (275), smoothing the first and second microprotrusions (331, 333) on the intermediate optical element (5), thereby forming the optical lens (1), wherein the second thickness (h) is greater than the first thickness (h), and wherein the third layer (277) and the third layer (275) form a second microprotrusion body (333) 273 ) And the fourth thickness (h) 277 ) Different. Corresponding intermediate optical elements are also described.)

1. A method for manufacturing an optical lens (1) by additive manufacturing, the method comprising the steps of:

-depositing a layer having a first thickness (h)₂₇₁) Of the first layer (271),

will have a second thickness (h)₂₇₃) Onto the first layer (271), the second layer (273) forming with the first layer (271) first microprotrusions (331),

-depositing a layer having a third thickness (h)₂₇₅) Of a third layer (275) of the first layer,

will have a fourth thickness (h)₂₇₇) Is deposited onto the third layer (275), thereby forming an intermediate optical element (5), the fourth layer (277) forming with the third layer (275) a second microprotrusion body (333),

-smoothing the first and second micro-relief (331, 333) on the intermediate optical element (5), thereby forming the optical lens (1),

wherein the second thickness (h)₂₇₃) And the fourth thickness (h)₂₇₇) Different.

2. The method of claim 1, wherein the thickness of each of the layers is determined based on the location of the associated layer in the intermediate optical element.

3. The method according to claim 1 or 2, wherein a first smoothing time required for smoothing the first asperities (331) is equal to a second smoothing time for smoothing the second asperities (333).

4. The method according to any of claims 1 to 3, further comprising the step of determining geometrical parameters of the first layer (271), the second layer (273), the third layer (275) and the fourth layer (277) based on smoothing parameters.

5. The method according to any of the claims 1 to 4, further comprising the step (S0) of determining geometrical parameters of the first layer (271), the second layer (273), the third layer (275) and the fourth layer (277) based on the curvature of the optical lens (1).

6. The method according to any one of claims 4 or 5, wherein the geometrical parameter comprises a first thickness (h) of the first layer (271)₂₇₁) A second thickness (h) of the second layer (273)₂₇₃) A third thickness (h) of the third layer (275)₂₇₅) And a fourth thickness (h) of the fourth layer (277)₂₇₇)。

7. The method of any of claims 4 to 6, wherein the geometrical parameter comprises a first exposure length (r) of the first layer (271)₂₇₁) A second exposed length (r) of the second layer (273)₂₇₃) A third exposed length (r) of the third layer (275)₂₇₅) And a fourth exposed length (r) of the fourth layer (277)₂₇₇)。

8. The method according to claims 1 to 7, wherein the cross-sectional area of the first microprotrusions (331) is equal to the cross-sectional area of the second microprotrusions (333).

9. The method according to any one of claims 1 to 8, wherein the smoothing step comprises polishing the surface of the intermediate optical element (5).

10. The method according to any one of claims 1 to 8, wherein the step of smoothing comprises applying a coating onto the surface of the intermediate optical element (5).

11. The method of claim 10, wherein a first volume of coating is applied to the first asperities (331) and a second volume of coating is applied to the second asperities (333).

12. An intermediate optical element (5) manufactured by additive manufacturing, the intermediate optical element comprising:

-has a first thickness (h)₂₇₁) Of the first layer (271),

-on the first layer (271) having a second thickness (h)₂₇₃) The second layer (273) of (C), the second layer (273) forming with the first layer (331) first microprotrusions (331),

-has a third thickness (h)₂₇₅) A third layer (275), and

-on said third layer (275) having a fourth thickness (h)₂₇₇) Said fourth layer (277) forming with said third layer (275) a second microprotrusion body (333),

wherein the second thickness (h)₂₇₃) And the fourth thickness (h)₂₇₇) Different.

13. Intermediate optical element (5) according to claim 12, wherein, on the intermediate optical element (5), the product of the thickness (h) of a layer (27) and the exposed length (r) of another layer juxtaposed on said layer (27) is constant.

14. The intermediate optical element (5) according to any one of claims 12 or 13, having a first end layer (278), a second end layer (279) and a plurality of layers located between the first end layer (278) and the second end layer (279), each layer having a thickness (h) and an exposed length (r), and wherein the thickness (h) increases with the layers from the first end layer (278) to the second end layer (279), and wherein the exposed length (r) decreases from the first end layer (278) to the second end layer (279).

15. The intermediate optical element (5) of claim 12, having a first end layer (278), a second end layer (279), and a plurality of layers between the first end layer (278) and the second end layer (279), each layer having a thickness (h) and an exposed length (r), and wherein the thickness (h) is constant from the first end layer (278) to a first transition layer and increases from the first transition layer to the second end layer (279), and wherein the exposed length (r) decreases from the first end layer (278) to a second transition layer and is constant from the second transition layer to the second end layer (279).

Technical Field

The present invention relates to the manufacture of optical lenses.

More specifically, the invention relates to a method for manufacturing an optical lens by additive manufacturing.

The invention also relates to an intermediate optical element manufactured by additive manufacturing.

Background

It is interesting to manufacture optical lenses using additive manufacturing techniques, since the obtained optical lenses are directly shaped to fit the frame that is to support it and/or the obtained optical lenses conform to the wearer's ophthalmic prescription.

The additive manufacturing process needs to be performed accurately; in particular, it is necessary to position the new layer very accurately on the already polymerized layer in order to manufacture the optical lens correctly.

The main drawback of this technique is that the obtained article does not have a good surface quality due to the microprotrusions formed by the edges of the layers.

In additive manufacturing, there are two main methods available for improving the surface quality of lenses. The first method is to reduce the thickness of the layer, thereby minimizing the asperities; however, this approach increases manufacturing time since more layers must be deposited. The second method is to post-treat the lens surface by polishing the microprotrusions; however, precision polishing can increase manufacturing time.

There is a need to find a method for producing optical lenses with good surface quality without increasing the manufacturing time.

Disclosure of Invention

It is therefore an object of the present invention to provide a method for manufacturing an optical lens by additive manufacturing, the method comprising the steps of:

-depositing a first layer having a first thickness,

-depositing a second layer having a second thickness onto the first layer, the second layer forming first microprotrusions with the first layer,

-depositing a third layer having a third thickness,

-depositing a fourth layer having a fourth thickness onto the third layer, thereby forming an intermediate optical element, the fourth layer and the third layer forming a second microprotrusion,

-smoothing the first and second microprotrusions on the intermediate optical element, thereby forming the optical lens.

According to the invention, the second thickness and the fourth thickness are different.

In general, the smoothing of the asperities depends not only on their thickness (on the thickness of the layer) but also on their position in the intermediate optical element. Generally, the microprotrusions located at the periphery of the intermediate optical element are removed more easily and more quickly than the microprotrusions located at the apex thereof.

Thus, for an intermediate optical element with layers of the same thickness, the smoothing process will be achieved more quickly at the periphery than at the center. The smoothing step must take this difference into account. This can be a complex process and increases manufacturing time.

Here, the thickness of each layer is determined based on the position of the layer in the intermediate optical element and in order to simplify the smoothing step.

For example, by making the layer near the periphery thicker and the layer near the apex thinner, all of the asperities can be removed at the same rate. Due to the method of the invention, the smoothing step is simplified and the manufacturing time is reduced.

Other advantageous and non-limiting features of the method according to the invention include:

-the thickness of each of the layers is determined based on the position of the relevant layer in the intermediate optical element,

-a first smoothing time required for smoothing the first asperities is equal to a second smoothing time for smoothing the second asperities,

-the method further comprises the step of determining geometrical parameters of the first, second, third and fourth layers based on smoothing parameters,

the method further comprises the step of determining geometrical parameters of the first, second, third and fourth layers based on the curvature of the optical lens,

-the geometrical parameters of the first, second, third and fourth layers are determined such that a first smoothing time required for smoothing the first asperities is equal to a second smoothing time for smoothing the second asperities,

-the geometrical parameters comprise a first thickness of the first layer, a second thickness of the second layer, a third thickness of the third layer and a fourth thickness of the fourth layer,

-the geometrical parameters comprise a first exposed length of the first layer, a second exposed length of the second layer, a third exposed length of the third layer and a fourth exposed length of the fourth layer,

-the intermediate optical element is rotationally symmetric,

the cross-sectional area of the first asperity (in a given plane of the intermediate optical element, for example a radial plane when the intermediate optical element is rotationally symmetric) is equal to the cross-sectional area of the second asperity (in the given plane),

-evaluating the cross-sectional area of the first asperities as the surface of a depression (on the given plane) between the end of the second layer and the first layer,

-evaluating the cross-sectional area of the second asperities as the surface of a depression (on the given plane) between the end of the fourth layer and the third layer,

-the smoothing step comprises polishing the surface of the intermediate optical element,

-the smoothing step comprises applying a coating onto the surface of the intermediate optical element,

-applying a first volume of coating onto the first asperities and a second volume of coating onto the second asperities.

The invention also relates to an intermediate optical element manufactured by additive manufacturing, the intermediate optical element comprising:

-a first layer having a first thickness,

-a second layer of a second thickness on the first layer, the second layer forming a first microprotrusion with the first layer,

-a third layer having a third thickness, an

-a fourth layer of a fourth thickness on the third layer, the fourth layer and the third layer forming a second microprotrusion.

According to the invention, the second thickness and the fourth thickness are different.

Other advantageous and non-limiting features of the intermediate optical element according to the invention include:

-on said intermediate optical element, the product of the thickness of a layer and the exposed length of another layer juxtaposed on said layer is constant,

-the intermediate optical element comprises a first end layer, a second end layer and a plurality of layers between the first end layer and the second end layer, each layer having a thickness and an exposed length,

-the thickness increases with the layer from the first end layer to the second end layer (layer by layer), and wherein the exposed length decreases from the first end layer to the second end layer,

-the thickness is constant from the first end layer to a first transition layer and increases from the first transition layer to the second end layer, and wherein the exposed length decreases from the first end layer to a second transition layer and is constant from the second transition layer to the second end layer,

-the first end layer comprises the fourth layer,

-the second end layer comprises the first layer,

-the first thickness of the first layer is greater than the fourth thickness of the fourth layer,

-the first exposed length of the first layer is shorter than the fourth exposed length of the fourth layer.

Each of the above thicknesses (and/or exposed lengths) may be a thickness (or exposed length) in at least one plane of the intermediate optical element, in particular in a radial plane of the intermediate optical element when the intermediate optical element is rotationally symmetric.

Detailed Description

The method and the intermediate optical element according to the invention will be described next with reference to the figures.

In the drawings:

figure 1 illustrates a system for manufacturing an optical lens by additive manufacturing,

figure 2 illustrates a cross-sectional view of an intermediate optical element manufactured by the system of figure 1,

FIG. 3 illustrates a detailed cross-sectional view of the intermediate optical element of FIG. 2, its layers and some of its geometrical parameters,

figure 4 illustrates a top view of a detail of the intermediate optical element of figure 2,

figure 5 illustrates a cross-sectional view of an optical lens manufactured by the system of figure 1,

figure 6 is a schematic representation of the steps of the method according to the invention,

figure 7 illustrates the intermediate optical element of figure 2 and its envelope curve,

figure 8 is a graph of the variation of the geometrical parameters with the position of the points of the intermediate optical element 5,

FIG. 9 is a graph of another geometrical parameter as a function of the position of the point of the intermediate optical element 5,

FIG. 10 is a graph illustrating the problem of smoothing an intermediate optical element,

FIG. 11 is a graph illustrating the variation of the geometrical parameters of the first embodiment of the method,

figure 12 is a graph illustrating the variation of the geometrical parameters of a variant of the first embodiment of the method,

fig. 13 is a graph illustrating the variation of the geometrical parameters of the second embodiment of the method.

Fig. 1 shows a system 2 for manufacturing an optical lens 1. The system comprises an additive manufacturing machine 3 for producing an intermediate optical element 5. The system comprises a smoothing machine 7 for smoothing the intermediate element 5 into the optical lens 1.

The additive manufacturing machine 3 comprises a deposition device 9. The deposition means 9 is adapted to use additive manufacturing techniques to manufacture the intermediate optical element 5. The expression "additive manufacturing technique" refers to a process of manufacturing a real object by juxtaposing volume elements or voxels. In the case of the present invention, the intermediate optical element 5 is thus produced layer by layer, volume element by volume element. Indeed, the additive manufacturing technique may be a Stereolithography (SLA) or polymer jetting or Continuous Liquid Interface Production (CLIP) technique.

In the example shown, the deposition device 9 comprises a nozzle or a group of nozzles to deposit the layers.

In the examples described below, subsequent layers are deposited on a previous layer, thereby defining a deposition axis a. The deposition axis a is therefore here perpendicular to the main surface of each deposited layer or, put another way, extends along the thickness of each deposited layer.

The additive manufacturing machine 3 further comprises a first control unit 11 to control the deposition arrangement 9. The first control unit 11 comprises a first microprocessor 12 and a first memory 13. The first memory 13 stores instructions that, when executed by the first microprocessor 12, allow the additive manufacturing machine 3 to implement a method for manufacturing the intermediate optical element 5 as described below.

The smoothing machine 7 comprises a smoothing device 15 and a second control unit 17.

The smoothing machine 7 is configured to smooth the surface of the intermediate optical element 5 in order to produce the optical lens 1.

The smoothing means 15 comprise polishing means capable of subtracting a volume of material from the intermediate optical element 5.

The smoothing device 15 includes, for example, a spindle-supported polishing tool, such as a polishing pupil (polishing pupil) having a predetermined diameter.

Alternatively, the smoothing device 15 may comprise a vibratory finishing device 15. The vibratory finishing apparatus comprises a barrel in which an intermediate optical element 5 is placed together with some abrasive material (e.g. sand). When the barrel is vibrated, the sand will rub against the surface of the intermediate optical element 5, thereby polishing it.

Alternatively, the smoothing device 15 comprises a coating deposition machine capable of adding a volume of material to the intermediate optical element 5.

The second control unit 17 comprises a second microprocessor 19 and a second memory 21. The second memory 21 stores parameters which, when executed by the second microprocessor 19, allow the smoothing machine 7 to implement the method for smoothing the intermediate optical element 5 as described below.

In the case of polishing the pupil, the parameters include, for example, the trajectory of the polishing pupil on the surface of the intermediate optical element 5, the number of sweeps to be performed, the rotational speed of the polishing pupil and/or of the intermediate optical element 5, and the angle of the polishing pupil axis to the surface of the intermediate optical element 5.

In the case of a vibratory bowl, the parameters include the duration of the smoothing process, as well as the type of abrasive and its average size in the case of a vibratory finishing apparatus 15.

In the case of a thin film deposition machine, the parameters include the volume of the coating or the average thickness of the coating.

Fig. 2 schematically illustrates the intermediate optical element 5. In the present example, the intermediate optical element 5 has a body provided with a first face 23, here convex, and a second face 25, here concave. The intermediate optical element 5 has a peripheral edge connecting the first face 23 to the second face 25.

Here, the intermediate optical element 5 is formed by a plurality of predetermined volume elements juxtaposed and superimposed to form a stack of superimposed layers 27 of material.

These predetermined volume elements have different geometries and volumes from each other. These volume elements may also be composed of the same material or, as a variant, of at least two different materials (for example with different refractive indices).

Fig. 2 also shows the object first side 29 and the object second side 31 in dashed lines. The target first face 29 corresponds to the first face 45 of the optical lens 1, as shown in fig. 5. The target second face 31 corresponds to the second face 47 of the optical lens 1.

The target surfaces 29 and 31 are predetermined, for example according to the ophthalmic prescription of the wearer of the lens.

The first face 23 and the second face 25 of the intermediate optical element 5 have microprotrusions 33 formed by edges of the layer 27 with the first face 23 and the second face 25 offset from the target faces 29, 31.

Thus, the center or vertex of the intermediate optical element 5 may be defined as the uppermost point along the deposition axis a corresponding to the target first face 29. The layer of the intermediate optical element 5 defining the center or apex is thus the last deposited layer here. When the intermediate optical element 5 is rotationally symmetric (and the axis of rotational symmetry is parallel to the deposition axis), this center or apex lies on the axis of rotational symmetry.

In the example of fig. 2, the periphery of the intermediate optical element 5 corresponds to the lowermost region of the intermediate optical element 5 along the deposition axis (i.e. corresponds to the region deposited first).

Fig. 3 illustrates a detail of the first face 23 of the first embodiment of the intermediate optical element 5.

The superimposed layer 27 forms a "step" in the direction of the axis a (here the deposition axis a) at the interface between the lower layer and the end of the upper juxtaposed layer. The "step" has an exposed surface 40 that is not covered by the overlying juxtaposed layer.

Each layer 27 is provided here with peaks 35 (also called high spots) at the free end of the layer 27 and with depressions 37 (also called low spots) at the junction between the end of the upper layer and the immediately underlying lower layer.

Furthermore, each layer 27 is provided with a shoulder 38, which is arranged between the peaks 35 and the dimples 37 and substantially represents the thickness h of the layer 27.

Each layer 27 further has a length l. The superimposed layers 27 shown here have different lengths l in order to form the first face 23 and the second face 25.

Each layer further has an exposed length r corresponding to the length of the exposed surface 40.

The superimposed layers 27 shown here have different lengths l in order to form the first face 23 and the second face 25.

At the free ends of the two adjacent layers 27, asperities 33 are formed. As explained below, the volume or the cross-sectional surface (on a given plane) of the asperities 33 can be estimated by taking into account the volume or the cross-sectional surface of the corresponding depressions 37, or, as a variant, by taking into account the volume or the cross-sectional surface of the corresponding peaks 35.

Illustrated in fig. 3 are a first layer 271, a second layer 273, a third layer 275, and a fourth layer 277.

The first layer 271 has a first thickness h₂₇₁A first length l₂₇₁And a first exposure length r₂₇₁。

The second layer 273 is positioned on top of the first layer 271. The second layer has a second thickness h₂₇₃A second length l₂₇₃And a second exposure length r₂₇₃. The exposed surfaces of the first layer 271 and the second layer 273 form first microprotrusions 331.

The third layer 275 has a third thickness h₂₇₅A third length l₂₇₅And a third exposure length r₂₇₅. In the example shown in fig. 3, the third layer 275 is positioned on top of the second layer 273. Alternatively, the third layer 275 and the second layer 273 may not be adjacent. Between the third layer 275 and the second layer 273So that one or more intermediate layers are present.

The fourth layer 277 is located on top of the third layer 275. The fourth layer 277 has a fourth thickness h₂₇₇A fourth length l₂₇₇And a fourth exposure length r₂₇₇. The exposed surfaces of the third layer 275 and the fourth layer 277 form the second asperities 333.

Since the third layer 275 is positioned on top of the second layer 273 in this example, the exposed surfaces of the second and third layers 273, 275 form the third asperities 335.

The intermediate optical element 5 also has a first end layer 278 and a second end layer 279 (which in the example represented here is the first layer 271). The second end layer 279 is a layer that is first deposited along the deposition axis a. The first layer 278 is the layer that is last deposited along the deposition axis a.

In this example, since the first face 23 is convex, the first length l₂₇₁Is greater than the second length l₂₇₃The second length itself being greater than the third length l₂₇₅The third length itself being greater than the fourth length l₂₇₇. The first end layer 278 is the shortest layer; in some embodiments, the second end layer 279 may be the longest layer of the intermediate optical element 5.

Each layer 27 has a substantially constant thickness h over its length l. However, the respective layers 27 have respective thicknesses different from each other.

In the first embodiment of the intermediate optical element 5 shown in fig. 3, the first thickness h of the first layer 271₂₇₁Is greater than the second layer h₂₇₃Second thickness h of₂₇₃. Second thickness h₂₇₃Itself greater than the third thickness h of the third layer 275₂₇₅. Third thickness h₂₇₅Itself is greater than the fourth thickness h₂₇₇。

In other words, in this first embodiment, the thickness h increases from the first end tier 278 to the second end tier 279.

In other words, a layer with the free end further from the deposition axis a has a greater thickness h than a layer with the free end closer to the deposition axis a.

The first layer 271 extends a first exposed length r further than the second layer 273₂₇₁. The second ply 273 is larger than the third ply275 further extend a second exposed length r₂₇₃. The third layer extends a third exposed length r further than the fourth layer 277₂₇₅。

In other words, in this first embodiment, the exposed length r decreases from the first end tier 278 to the second end tier 279.

In other words, layers with the free end further from the deposition axis a have a shorter exposed length r than layers with the free end closer to the deposition axis a.

As shown in fig. 4, the intermediate optical element 5 may not have rotational symmetry. In this case, the exposed length r of layer 27 may vary across layer 27.

For example, the exposed length r of the second layer 273₂₇₃Can be determined by the following equation:

r₂₇₃＝r_273.0+Δr

wherein r is_273.0There may be a minimum exposed length of the second layer 273 and ar is the change in exposed length in a radial direction relative to the deposition axis a.

In other embodiments, the intermediate optical element 5 has rotational symmetry. The layers 27 of such intermediate optical elements 5 each have a constant exposed length r.

In a second embodiment of the intermediate optical element (not shown), the thickness h is constant from the first end layer to the first transition layer. The thickness h then increases from the first transition layer to the second end layer.

In this second embodiment, the exposed length r of the layers increases from the first end layer to the second transition layer. The exposed length is then constant from the second transition layer to the second end layer.

In an example of the second embodiment, the first transition layer and the second transition layer are the same layer. In another example of the second embodiment, the first transition layer and the second transition layer are different layers.

Fig. 5 illustrates the optical lens 1 obtained after the intermediate optical element 5 has been subjected to a smoothing treatment. The first face 45 and the second face 47 of the optical lens 1 are smoothed to meet ophthalmic requirements.

The method for manufacturing an optical lens by additive manufacturing is based on the deposition of a layer 27 of optical material and on its subsequent smoothing.

Fig. 6 is a schematic representation of steps of a method for manufacturing an optical lens by additive manufacturing.

In step S0, manufacturing settings for additive manufacturing of the optical lens 1 are determined. Step S0 is realized by the first control unit 11. The manufacturing settings include, for example, the number of layers 27 to be deposited, the thickness h, length l, and exposed length r of each layer 27, the material to be deposited.

In step S01, the first control unit 11 receives a file containing the prescription value for the wearer of the optical lens 1 to be manufactured. The first control unit 11 also receives complementary fitting and personalization data relating to the wearer and/or the frame intended to receive the ophthalmic lens 1. These complementary fitting and personalization data correspond, for example, to geometric values that characterize, in particular, the visual behavior of the frame and of the wearer. The complementary fitting and personalization data include, for example, the ophthalmic lens distance, the position of the center of rotation of the eye, etc.

In step S02, the first control unit 11 determines a corrective optical function tailored to the wearer according to the wearer prescription values and the complementary fitting and personalization data.

In step S03, the first control unit 11 determines a target geometrical feature of the optical lens 1 to be manufactured according to the optical function.

The target geometric feature comprises for example the coordinates (x, y, z) of a limited number of points of the optical lens 1. Alternatively, the target geometric feature includes a surface function z ═ f (x, y) defining the target first face 29 and the target second face 31.

In step S04, the first control unit 11 also receives a file containing smoothing data. The smoothing data include, for example, the diameter of the polished pupil, the rotation speed, the sweeping speed, the pressure exerted by the pupil on the surface of the intermediate optical element 5.

In step S05, the first control unit 11 determines the geometric feature of the intermediate optical element 5 based on the smoothing processing data and on the target geometric feature. The first control unit 11 then generates a file containing the determined geometrical characteristics of the intermediate optical element 5.

The geometrical feature may take the form of, for example, the coordinates (x, y, z) of a limited number of points of the intermediate optical element 5. Alternatively, the geometric parameter may take the form of a surface function z ═ f (x, y) defining the first and second faces 23, 25 of the intermediate optical element 5.

Fig. 7 to 13 illustrate how the geometric features may be determined.

This explanation is given by considering a particular plane across the intermediate optical element 5, here the radial plane of the intermediate optical element 5 (i.e. the plane containing the axis of rotational symmetry). However, this solution is also applicable to non-rotationally symmetric intermediate optical elements 5, either by determining the geometric features separately in several different planes intersecting the intermediate optical element 5 (and possibly out of these planes by interpolation), or by determining the geometric features in a particular plane intersecting the intermediate optical element 4 as described below and by using the determined features in other planes. These solutions make it possible to homogenize the volume of the micro-convex bodies of an optical lens, which usually has an almost rotationally symmetric shape.

Fig. 7 illustrates the intermediate optical element 5 and its envelope curve C. Curve C passes through each peak 35 of layer 27. In the embodiment shown in fig. 7, the intermediate optical element 5 has a spherical envelope and the curve C is a circle with a center I. Other types of curves are possible. To determine the geometric characteristics of the layer, curve C is approximated by a line connecting adjacent peaks 35. As shown in the detailed view included in fig. 7, the line d connects the two adjacent peaks 35 represented. Fig. 7 also illustrates the deposition axis a.

Angle theta represents the angle between the free end of layer 27 (i.e., exposed surface 40 of layer 27) and line d. The further the free end is from the deposition axis a, the larger the angle θ.

Thus, the angle θ is also the angle between the deposition axis a (perpendicular to the exposed surface of the layer 27) and a line N perpendicular to the line d and passing through the dimple 37. Since the curve C is a circle in the present example and the straight line d approximates the curve C, the angle θ (between the deposition axis a and the straight line N) corresponds to the angle between the deposition axis a and the radius R of the circle C passing through the depression 26, and the angle θ then represents the position of the point (depression 37) on the first face 23 of the intermediate element 5.

Since the triangle formed by the shoulder 38, the exposed surface 40, and the line d is a right triangle, the angle θ can be determined using the following equation:

this equation establishes the relationship between the thickness h and the exposed length r of the layer 27 and its position in the intermediate optical element 5.

As now explained, not all thicknesses h and exposed lengths r are ideal in order to facilitate the smoothing step and improve the quality of the resulting optical lens 1.

The boundary conditions for determining the thickness h and the exposed length r of the layer 27 will now be described.

FIG. 8 shows the point at constant thickness h for the intermediate optical element 5_cNext, a graph of the exposed length r as a function of the angle θ.

As the value of the angle θ increases, the value of the exposure length r decreases. In other words, the layer 27 extending further away from the deposition axis a has a shorter exposed length r than a shorter layer.

As a result, the microprotrusions 33 become more easily smoothed as the angle θ increases. In other words, for one sweep of the pupil, the microprotrusions 33 farther from the deposition axis a are removed faster than the microprotrusions closer to the deposition axis a. In other words, the smoothing process at the outer periphery of the intermediate optical element 5 is achieved faster than the smoothing process near the center (here, the apex).

If the number of sweeps is set based on the smoothing of the microprotrusions 33 at the outer periphery, the microprotrusions near the center will not reach the target at the end of the smoothing step.

If the number of sweeps is set based on the smoothing of the microprotrusions 33 at the center, at the end of the smoothing step, excess material will be removed at the periphery.

Therefore, it is not desirable that all layers 27 have the same thickness h.

In addition, there is a maximum exposure length rmax beyond which it is considered difficult to smooth the asperities (e.g., the optical lenses produced are not of ophthalmic quality). Therefore, it is undesirable for the exposed length r of the layer to be greater than the maximum exposed length rmax. The maximum exposure length rmax may be determined experimentally.

FIG. 9 shows the spot for the intermediate optical element 5 at a constant exposure length r_cNext, a graph of the thickness h as a function of the angle θ.

Constant length of exposure r_cIs determined by the geometric requirements of the first end layer 278.

As the value of the angle θ increases, the value of the thickness h also increases.

As a result, as the angle θ increases, the asperities 33 become more difficult to smooth. In other words, for one sweep of the pupil, the microprotrusions 33 closer to the deposition axis a are removed faster than the microprotrusions further from the deposition axis a. In other words, the smoothing process near the center of the intermediate optical element 5 is achieved faster than the smoothing process at the periphery.

If the number of sweeps is set based on the smoothing of the microprotrusions 33 at the outer periphery, excess material will be removed at the center at the end of the smoothing step.

If the number of sweeps is set based on the smoothing of the asperities 33 near the center, the asperities at the periphery will not reach the target at the end of the smoothing step.

Therefore, it is not desirable that all layers 27 have the same exposed length r.

In addition, there is a maximum thickness hmax, beyond which the difficulty of smoothing the microprotrusions increases. Therefore, a thickness of layer 27 greater than maximum thickness hmax is undesirable. The maximum thickness hmax can be determined by experiment.

On the graph of fig. 10, a second line L2 illustrates a point for the common intermediate optical element 5 and for a constant exposure length r_cThe thickness h varies with the angle theta.

The common value for the diameters of the intermediate optical elements 5 is 62 mm. The common value for the radii of curvature of the intermediate optical elements 5 is 125 mm. The common value of the refractive indices of the intermediate optical elements 5 is 1.5.

As a result, the common value of the angles θ at the outer periphery of the intermediate optical element 5 is pi/12.

The common value of the exposed length of the top layer 279 is 1.6mm, here a constant exposed length r_cThe value of (c).

The current minimum thickness hmin, determined by the current state of additive manufacturing technology, is 10 μm. The minimum thickness hmin is illustrated by a third line L3.

The shaded area S represents a set of coordinate points (h, θ) that are considered difficult to be subjected to smoothing processing. The set of points is determined, for example, by experimentation. For example, a test intermediate optical element having geometric features contained in this set of points cannot provide an optical lens having ophthalmic quality.

The shaded area S has a lower limit indicated by a fourth line L4. The lower limit corresponds to the maximum thickness hmax. The common value for the maximum thickness hmax is, for example, 13 μm.

As can be seen on the graph of fig. 10, for a constant exposure length r_cThe maximum thickness hmax is reached for angles theta less than the desired pi/12.

In other words, it is impossible to achieve a constant exposure length r_cOf an intermediate optical element 5 of angle pi/12.

In order to determine the thickness h and the exposed length r, which are well suited to subsequent smoothing, a first embodiment of the method is to vary the values of the thickness h and the exposed length r over the entire intermediate optical element 5. The first embodiment of the method produces a first embodiment of the intermediate optical element 5 (as shown in figure 3).

On the graph of fig. 11, a first line L1 represents the thickness h as a function of angle θ, where the thickness h increases as the angle θ increases, and where the exposure length r decreases as the angle θ increases. The second line L2 represents the variation of the thickness h with the angle theta for a constant exposure length r.

The third line L3 represents the minimum thickness value (e.g. 10 μm).

The fourth line L4 represents the minimum thickness value of the shaded area S, i.e. the maximum thickness hmax (for example 13 μm)

Angle theta_pIndicating the angle at the periphery of the intermediate optical element 5.

In order to achieve an optimal smoothing process, all coordinate points (h, θ) (and their corresponding exposed lengths r) located in the region bounded by the first, second, third and fourth lines L1, L2, L3, L4 may be used to determine parameters of the intermediate geometric element 5, including the thickness h and exposed length r of the layer 27.

A variant of the first embodiment of the method is to determine the parameters, including the thickness t and the exposed length r of the layer 27, such that the cross-sectional area of the asperities 33 in the radial plane remains constant for all layers 27.

This variant represented on the graph of fig. 12 facilitates the smoothing of the intermediate optical element 5, since the polishing pupil polishes approximately the same volume for each of the microprotrusions 33 during the sweeping of the intermediate optical element 5.

The graph of fig. 12 represents another plot of thickness h as a function of angle theta for varying exposed lengths r. The graph of fig. 12 comprises a variant of the first embodiment of the method.

A second line L2 represents the variation in thickness h for a constant exposed length (as shown in fig. 10).

The fifth line L5 represents the variation in thickness h when keeping the cross-sectional area of the asperities 33 constant as proposed above.

The surface S of the asperities of the top layer 279, evaluated in the present case by taking into account the cross section of the dimples 37_asp279Is given by:

2S_asp279＝h×r

wherein, as previously described:

then:

h＝k×(tanθ)^1/2

wherein:

for an optimal smoothing process all points comprised between the second line L2 and the fifth line L5 may be used to determine the geometry file of the intermediate optical element 5. However, in order to keep the surface of the asperities constant during the polishing step, these points should be selected near the fifth line L5.

On the graph of fig. 12, a sixth line L6 represents when for a constant exposure length r_cThe variation of the thickness h while keeping the cross section of the surface of the asperities 33 constant. However, it can be seen that for angles θ less than the desired π/12, a maximum thickness hmax is reached. Therefore, it is not desirable to select a point on the sixth line L6.

Fig. 13 illustrates a second embodiment of the method. The second embodiment of the method produces a second embodiment of the intermediate optical element 5.

The graph of fig. 13 illustrates the variation of the thickness h with the angle θ for a second possibility for determining a parameter of the intermediate optical element 5.

In this case, the thickness h is at 0 and the first transition angle θ₁Is constant within a first range of angles theta included therebetween. First transition angle theta₁Corresponding to the angle between the deposition axis a of the second embodiment of the intermediate optical element and the first transition layer.

Then, for a transition angle θ including more than the first transition angle₁In a second range of angles, the thickness h increases. For the maximum angle θ max, the thickness h reaches a maximum thickness hmax.

The exposure length r is between 0 and the second transition angle theta₂In another first range of angles included therebetween. Second transition angle theta₂Corresponding to the angle between the deposition axis a of the second embodiment of the intermediate optical element and the second transition layer.

The exposed length r is then greater than the second transition angle theta₂Is constant over a further second range of angles.

In the present example, the first transition angle θ₁And a second transition angle theta₂Are equal.

In a variant of the second embodiment of the method, the first transition angle θ₁And a second transition angle theta₂Different.

In order to achieve an optimal smoothing process, all coordinate points (h, θ) (and their corresponding exposure lengths r) located in the region bounded by the first, second, third and fourth lines L1, L2, L3, L4 may be used to determine the parameters of the intermediate geometric element 5.

In step S06, the first control unit 11 generates a manufacturing file corresponding to the manufacturing settings of the intermediate optical element 5 based on the geometric features of the intermediate optical element 5.

This "set" file is similar to the previously generated geometry file of the intermediate optical element 5, except that it reflects a transcribed description of the desired geometry of this intermediate optical element 5 to be manufactured, which in fact has the arrangement of the predetermined volume elements of the material or materials with respect to the reference frame of the additive manufacturing machine, and the deposition order of these volume elements with respect to each other.

Alternatively, step S0 may be implemented partly or entirely by an external computing unit, which then sends the parameters to the first control unit 11.

In step S1, layer 27 is deposited by additive manufacturing machine 3. The first microprocessor 12 implements the manufacturing settings received from the first control unit 11.

In step S11, a first thickness h is deposited₂₇₁And a first length l₂₇₁The first layer 271.

At step S12, the second thickness h₂₇₃And a second length l₂₇₃Is deposited onto the first layer 271. The second layer 273 is positioned to conform to the first exposed length r of the first layer 271₂₇₁。

At step S13, it will have a third thickness h₂₇₅And length l₂₇₅The third layer 275 is deposited onto the second layer 273. The third layer 275 is positioned to conform to the second exposure length of the second layer 273Degree r₂₇₃。

Alternatively, an intermediate layer (not shown) may be deposited onto the second layer 273. The intermediate ply is positioned to conform to the second exposed length r of the second ply 273₂₇₃。

A third layer 275 is then deposited onto the intermediate layer. The third layer 275 is positioned to conform to the exposed length of the middle layer.

Alternatively, a plurality of other intermediate layers may be deposited on top of the intermediate layer. Each intermediate layer is positioned to respect the exposed length of the immediately underlying intermediate layer.

At step S14, it will have a fourth thickness h₂₇₇And length l₂₇₇Is deposited onto the third layer 275. The fourth layer 277 is positioned to conform to the third exposed length r of the third layer 275₂₇₅。

These deposition steps are carried out until all layers 27 are deposited.

The intermediate optical element 5 is then placed in a smoothing machine 7.

In step S2, the smoothing device 15 smoothes the surface of the intermediate optical element 5. The smoothing instruction is determined or received by the second control unit 17.

In the case of a polishing apparatus comprising a polished pupil, the smoothing instructions comprise the previously mentioned data, such as the sweep speed, the rotational speed of the pupil, the number of sweeps. The smoothing instructions are determined such that the same number of sweeps of the surface of each face 21, 25 of the intermediate optical element 5 is required to smooth the microprotrusions 33.

The second microprocessor 19 implements the smoothing instructions and the polishing pupil sweeps the surface of the intermediate optical element 5, thereby smoothing the first, second and third microprotrusions 331, 333, 335.

According to a variant, the smoothing treatment comprises the application of a coating onto the surface of the intermediate optical element 5. A first volume of coating is applied to the first asperities 331. Applying a second volume of coating to the second asperities 333)

Optionally, the method comprises the step of subjecting the first face 45 and the second face 47 of the optical lens 1 to: to which one or more predetermined functional coatings are added. Functional coatings include, for example, antifog coatings, antireflective coatings, colored coatings, scratch resistant coatings.

Alternatively, a cylinder of optical material is provided to the additive manufacturing machine 3 prior to the deposition step. The cylinder forms the core of the intermediate optical element 5. Then, a layer 27 is deposited around the cylinder to obtain the intermediate optical element 5.

The cylinder is buried in layer 27. The cylinder does not form any microprotrusions of the intermediate optical element 5 and therefore does not undergo a smoothing step.