From US 3,532,038 there is known an optical system in which a transparent base member is provided with lenticular lens cavities, which cavities are filled with a refractive fluid, the surface of which fluid is covered with a cover member. The cover member is provided with an aperture plate, on which finally a second base member is present, which is also provided with lenticular lens cavities, which cavities are likewise filled with a refractive fluid.

From US 2004/0100700 there is known a method of manufacturing a micro lens array, wherein the cavities in a mould are filled with a UV curable resin, whilst the resin outside the cavities is removed by placing a transparent quartz board on top of the mould. The fluid present in the cavities is then formed into a plurality of separate lenses, whereupon a second UV curable resin layer is applied to the transparent board, which resin layer is cured by making use of the already formed separate lenses. The excess amount of the cured second resin layer is removed by using an organic solvent. Only one layer of replicated lenses is mentioned in said document, which lenses are separately arranged and do not exhibit any interconnection.

The replication process is known per se from U.S. Pat. Nos. 4,756,972 and 4,890,905, which disclose the possibility of manufacturing a high- quality optical component by means of a replication process. Such a replication process is considered to be a quick and inexpensive manner of manufacturing optical components in large numbers. In the replication process, a mould having a precisely defined surface, for example an aspherical surface, is used, and a small amount of a radiation curable resin, for example a UV curable resin, is applied to the mould surface. Subsequently, the resin is spread over the mould surface, so that the cavities in the mould are filled with the resin, after which the whole is irradiated so as to cure the resin and the thus cured product is removed from the mould. The cured product is a negative of the mould surface. An advantage of the replication process is that lenses having a complex refractive surface, such as an aspherical surface, can be manufactured in a simple manner without having to subject the lens body to intricate grinding and polishing processes.

From International application WO 03/069740 in the name of the present applicant there is also known a replication process by which an optical element is formed.

WO 2012100356 relates to a method for manufacturing a plurality of optical devices, comprising the steps of: providing a replication tool, the replication tool comprising a replication surface defining an array of replication cells, each replication cell comprising a lens replication portion and a spacer replication portion, bringing the replication tool and a support in contact with each other with replication material between the replication surface and the support; causing the replication material to harden, wherein, during the step of causing the replication material to harden, the lens replication sections are caused to be kept at a distance from the support.

US 2009022949 relates to a process for producing a functional- element-mounted module, comprising the steps of disposing a substrate having mounted thereon a functional element having a mounting portion and a resin sealing plate formed therein with an opening corresponding in position to the functional portion of the functional element as opposed to each other at a predetermined distance; and impregnating and filling a sealing resin between the substrate and the resin sealing plate utilizing a capillary phenomenon.

WO 2015093945 in the name of the present applicant relates to a method of fabricating a wafer level optical lens assembly, comprising: providing a first wafer substrate having a plurality of bumps; applying a first polymer liquid on a first contact optical surface of said plurality of bumps; providing a second wafer substrate; contacting said first wafer substrate with said second substrate in such that said first polymer liquid is located in a slit created between said first contact optical surface of said plurality of bumps and said second wafer substrate under capillary forces; curing said polymer liquid(s) to form a lens.

US 2009034088 relates to a method of making a micro-optical device, comprising: providing a replication material between a support substrate and a master substrate having structural features for forming a micro-optical lens, the replication material covering at least a portion of an opaque material on the support substrate; applying pressure to at least one of the support substrate and the master substrate; curing the replication material to form a replica including the micro-optical lens; and removing the support substrate including the opaque material and the replica.

US 2012200943 relates to a method of forming a lens, comprising: molding a pre-final lens using a first master, using a second master to form a top layer atop the pre-final lens, wherein the pre-final lens includes a deformity due to shrinkage of the pre-final lens after molding the pre-final lens, and wherein the top layer substantially corrects the deformity, wherein the pre-final lens forms a majority of a final volume of the lens.

WO 2014092148 relates to a method for manufacturing a lens array structure, whereby an adhesive is applied between first lens elements formed on a lens array and pushing out of the adhesive applied on the periphery of the outside lens elements to the surroundings can be limited.

EP 1 837 165 relates to a method of manufacturing an element by means of a replication tool, comprising the steps of providing a replication tool that defines the shape of the element; providing a substrate; pressing the replication tool against the substrate, with a replication material in a liquid or viscous or plastically deformable state located between the tool and the substrate; confining the replication material to a predetermined area of the substrate, which predetermined area exceeds the desired area of the element on the substrate, in at least one direction along the surface of the substrate by less than a predetermined distance; hardening the replication material to form the element.

JP2008152040 relates to a manufacturing method of a micro lens array involving injecting UV ray cured resin into metallic molds having curved respective mold surfaces corresponding to front-side and back side lens surface of micro lens arrays. The glass substrates are positioned on the metallic molds using positioning structure such as gap material. Such a gap material maintains a predetermined distance at the surroundings of the mold. The resin is hardened for forming micro lens arrays by irradiating UV ray from the side of glass substrates. The micro lens arrays are mutually aligned and integrated using positioning portions provided at the glass substrates.

WO2010050290 relates to a wafer lens manufacturing method for manufacturing a wafer lens provided with convex lens portions on a glass substrate by curing resin between the glass substrate and a resin mold in which concave cavities are formed. Uncured resin is disposed as a continuous layer on the cavities in the resin mold and cured, and uncured resin is disposed as a continuous layer between the resin mold and the glass substrate and the disposed resin is cured while being pressed from above by the glass substrate.

WO2015122769 relates to a method of fabricating a wafer level optical lens assembly, comprising the following steps: providing a wafer substrate having a plurality of lens shapes arranged side by side; providing a spacer substrate having a plurality of spacer posts; applying a first polymer liquid on a specific location chosen from the group of positions located on said wafer substrate between said plurality of lens shapes and positions located on the contact surface of said spacer posts, or a combination thereof; contacting said wafer substrate with said spacer substrate such that said spacer posts force said first polymer liquid to flow towards said plurality of lens shapes arranged side by side; curing said first polymer liquid; applying a second polymer liquid onto said plurality of lens shapes of said wafer substrate; curing said second polymer liquid to form a lens.

US2006262410 relates to a method of manufacturing a microlens having a convex shape on a substrate, comprising: providing a first droplet on the substrate; forming a first convex portion by drying the first droplet so as to solidify the first droplet; providing a second droplet of a lens material in a concave area that is placed at a center of the first convex portion; and forming a second convex portion by curing the second droplet.

From the above state of the art there are thus known methods by which optical systems are obtained which are made up of separately manufactured optical elements, as a result of which the dimensions of such systems may be considered to be large. In addition, the positional accuracy, viz. in the X, Y and Z directions (between the lens surfaces) of such systems may be called critical.

Current controlled contour shapes of optical elements are determined by mold shapes. Toolings for these complex shapes are expensive. Mold surfaces for only optical surfaces need to be very accurately shaped (typical λ/40 or better). Peripheral structures require far lower shape accuracies of at least 100 times lower.

An aspect of the present invention is to provide a method of fabricating an array of optical lens elements by means of a replication process in which contour shapes of optical elements can be controlled in an accurate manner. The present invention thus relates to a method of fabricating an array of optical lens elements, comprising:

providing a first mold having a plurality of recesses;

applying a first polymer liquid in said plurality of recesses;

providing a first contact shaping substrate;

contacting said first contact shaping substrate with said first polymer liquid in said plurality of recesses, wherein said contact between said first contact shaping substrate and said first polymer liquid results in a deformation of the contour configuration of said first polymer liquid facing away from said plurality of recesses;

curing said first polymer liquid to form an array of optical lens elements.

The present inventors found that by applying such a method the contour shapes of optical elements can be controlled in an accurate manner. In this embodiment the first polymer liquid is pressed by the first contact shaping substrate into the plurality of recesses such that a part of the first polymer liquid will flow out these pluralities of recesses into the direction of the surface of the first mold. This will be the surface directly surrounding the plurality of recesses. By maintaining the first contact shaping substrate in contact with the first polymer liquid during the step of curing an array of optical lens elements having well defined contour shapes is obtained. Thus, the first polymer liquid is positioned, i.e. confined, between the first contact shaping substrate and the first mold having a plurality of recesses. The array of optical lens elements thus obtained comprises one single cured polymer, namely the cured first polymer.

The method of fabricating an array of optical lens elements as discussed above preferably comprises, after curing said first polymer liquid, a step of removing said first mold.

In another preferred embodiment the present method of fabricating an array of optical lens elements further comprises, after curing said first polymer liquid,

a step of removing said first contact shaping substrate from said array of optical lens elements;

a step of providing a second polymer liquid onto said an array of optical lens elements;

curing said second polymer liquid. In such an embodiment according to the invention the present method can be identified as a two step replication process comprising, in a first step, the manufacturing of a preform structure and, in a second step, the replication of a second layer upon the cured preform to provide the final shape. The present inventors found that current processes for manufacturing optical elements are not accurate enough because of too large variations in vertexes of the preform and post filling part of the optical element. The array of optical lens elements thus obtained comprises a combination of two cured polymers, namely the cured first polymer and the cured second polymer.

In another preferred embodiment the present method of fabricating an array of optical lens elements further comprises, after providing said second polymer liquid onto said array of optical lens elements:

a step of providing a second contact shaping substrate;

a step of contacting said second contact shaping substrate with said second polymer liquid, wherein said contact between said second contact shaping substrate and said second polymer liquid results in a complete coverage of the contour configuration of said array of optical lens elements facing away from said first mold having a plurality of recesses;

curing said second polymer liquid.

In this embodiment the second polymer liquid is pressed by the second contact shaping substrate into the direction of the array of optical lens elements such that the second polymer liquid will distribute across the contours of the array of optical lens elements. By maintaining the second contact shaping substrate in contact with the second polymer liquid during the step of curing an array of optical lens elements having well defined contour shapes is obtained. Thus, the second polymer liquid is positioned, i.e. confined, between the second contact shaping substrate and the first mold. The array of optical lens elements thus obtained comprises a combination of two cured polymers, namely the cured first polymer and the cured second polymer.

The method of fabricating an array of optical lens elements as discussed above preferably comprises, after curing said second polymer liquid,

a step of removing said first mold.

The present inventors found that in a preferred embodiment the first contact shaping substrate is provided with a flow stop pattern acting as a flow stop for said first polymer liquid upon contacting said first contact shaping substrate with said first polymer liquid.

It is also preferred that the second contact shaping substrate is provided with a flow stop pattern acting as a flow stop for said second polymer liquid upon contacting said second contact shaping substrate with said second polymer liquid.

The flow stop pattern preferably comprises a layer of submicron thickness.

According to another preferred embodiment the flow stop pattern comprises a surface area having a surface energy being different than said first and/or second contact shaping substrate.

In a preferred embodiment of the present method of fabricating an array of optical lens elements the first mold having a plurality of recesses has a specific construction, namely at least some of said plurality of recesses is provided with a peripheral portion. Control of vertexes of preform resulting from prefill process and total lens shape is improved using a specific mold design with such a peripheral buffer zone. Resin flow may further be controlled by local surface geometries such as peripheral flow buffer zones and flow stops/ retarders on mold and/or shaping substrates and/or lens.

The shape of a droplet liquid-vapor interface on a surface, is determined by the Young-Laplace equation Y _S G- Y SL - Y _L G COS Q _C = 0, where Q _C denotes the contact angle and Y _S G, YSL X _LG the interfacial energies between the different phases liquid, gaseous and solid phases. A droplet deposited on a surface with a similar surface energy will have a low contact angle and will spread out. For example, a hydrophobic liquid resin will spread rapidly over a hydrophobic surface with low surface energy. The present inventors found that the surface energy of a substrate can modified trough a variety of technologies, such as plasma activation and chemical or physical vapor deposition (CVD, PVD) of thin layers on the substrates.

It is preferred when the first contact shaping substrate is configured as a flat substrate.

It is preferred when the second contact shaping substrate is configured as a flat substrate. According to a preferred embodiment of the method of fabricating an array of optical lens elements the surface energy of the contact surface of said second contact shaping substrate is such that said complete coverage of the contour configuration results in a lateral curvature shape.

A preferred lateral curvature shape is a half moon shape.

Another preferred lateral curvature shape is a bell clock curve shape.

The present invention will be discussed with reference to the figures.

Fig. 1 shows a first phase of the method of fabricating an array of optical lens elements.

Fig. 2 shows a second phase of the method of fabricating an array of optical lens elements.

Fig. 3 shows another embodiment of a second phase of the method of fabricating an array of optical lens elements.

Fig. 4 shows another embodiment of a second phase of the method of fabricating an array of optical lens elements.

Fig. 5 shows another embodiment of a second phase of the method of fabricating an array of optical lens elements.

Fig. 6 shows different contour variations of a lateral curvature shape.

Fig. 7 shows different embodiments of a flow stop zone.

Fig. 8 shows different embodiments of features controlling resin flow.

Fig.1 shows in Fig.1 A-G a first phase of the method of fabricating an array of optical lens elements. A first mold 1 having a plurality of recesses 3 is provided wherein a first polymer liquid 2 is applied in the plurality of recesses 3 (see Fig. 1A). According to Fig. 1 B a first contact shaping substrate 5 is provided and first contact shaping substrate 5 is contacted with first polymer liquid 2 present in plurality of recesses 3. By this contact the first polymer liquid 2 will be pressed into the plurality of recesses 3 and will partly flow out the plurality of recesses and cover some area of the surface of first mold 1 . Thus there is no continuous layer of the first polymer liquid 2 on the surface of first mold LThis contact between first contact shaping substrate 5 and first polymer liquid 2 results thus in a deformation of the contour configuration of first polymer liquid 2 facing away from the plurality of recesses 3. In Fig. 1 C the position of first contact shaping substrate 5 is maintained during the curing step, wherein first polymer liquid 2 is cured by energy 4 to form a plurality of replicated lenses 6. In case first contact shaping substrate 5 is removed (as shown in Fig. 1 D) the surface 7 of replicated lenses 6 is deformed. In Fig. 1 E first polymer liquid is cured by energy 4 to form a plurality of replicated lenses 6. In Fig. 1 E no first contact shaping substrate 5 has been used during the step of curing. I n Fig. 1 E there is no deformation of the surface of replicated lenses 6. In Fig. 1 F and 1 G an array of optical lens elements 6 is shown after removal of first mold 1 . The array of optical lens elements 6 comprises one single polymer, i.e. cured first polymer and first contact shaping substrate 5. A shown in both Fig. 1 F and 1 G parts 63 of the surface of first contact shaping substrate 5 have not been provided with cured polymer. The contour shape 64 (see Fig. 1 F) and contour shape 60 (see Fig. 1 G) are influenced by the surface tension of first contact shaping substrate 5, wherein the surface of first contact shaping substrate 5 has been identified by reference number 63. Surface part 61 is the result of the step of contacting first contact shaping substrate 5 with the first polymer liquid 2 before curing (see Fig. 1 B). The contour diameter of each lens element is determined by, inter alia, the amount of the first polymer liquid, and the distance between the contact shaping substrate and the mold and the local surface tension. The shape of contour 62 is determined by the shape of the plurality of recesses 3 in first mold 1 .

Fig.2 shows in Fig.2 A-D a second phase of the method of fabricating an array of optical lens elements. First mold 1 having a plurality of recesses 3 is provided with replicated lenses 6 therein. A second polymer liquid 8 is provided onto the plurality of replicated lenses 6 in Fig.2 A. According to Fig. 2B a second contact shaping substrate 9 is provided and second contact shaping substrate 9 is contacted with replicated lenses 6 present in plurality of recesses 3. This second polymer liquid 8 covers replicated lenses 6 completely as shown in Fig. 2B. The peripheral contour of second polymer liquid 8 is indicated with reference number 10. In Fig. 2C second polymer liquid 8 is cured by energy 4. In Fig. 2D a step of removing first mold 1 after curing the second polymer liquid for obtaining said array of optical lens elements is shown, comprising second contact shaping substrate 9 provided wit cured second polymer 1 1 and replicated lenses 6.

Fig.3 shows another embodiment of a second phase of the method of fabricating an array of optical lens elements, starting with the construction as shown in Fig. 1 D. In Fig. 3A first mold 1 having a plurality of recesses 3 is provided with replicated lenses 6 therein. A second polymer liquid 8 is provided onto the deformed surface 7 of the plurality of replicated lenses 6 in Fig.3 A. According to Fig. 3B a second contact shaping substrate 12 is provided and second contact shaping substrate 12 is contacted with the second polymer liquid 8 located on the replicated lenses 6 present in plurality of recesses 3. This second polymer liquid 8 covers replicated lenses 6 completely as shown in Fig. 3B. The peripheral contour of second polymer liquid 8 is indicated with reference number 14. In Fig. 3C second polymer liquid 8 is cured by energy 4. In Fig. 3D a step of removing first mold 1 after curing the second polymer liquid 8 for obtaining said array of optical lens elements is shown, comprising second contact shaping substrate 12 provided with cured second polymer and replicated lenses 6. Fig. 3D also shows the peripheral contour 14 of cured second polymer, the post fill interface 15, 16. Fig. 3F shows an embodiment similar to Fig. 3D but with different peripheral contour 17. This different peripheral contour can be achieved with different surface energy on mold surface. Fig. 3G shows a lateral curvature shape 14 as a half moon shape. Fig. 3H shows a lateral curvature shape 17 as a bell clock curve shape. Reference number 13 is a clear aperture edge, reference number 15, 18 is a lateral rim.

Fig.4 shows another embodiment of a second phase of the method of fabricating an array of optical lens elements. In Fig. 4A first mold 1 having a plurality of recesses 3 is provided with replicated lenses 6 therein. The lens surface of lens 6 has a shape peripheral portion 19, buffer zone. A second polymer liquid 8 is provided onto the surface of the plurality of replicated lenses 6 in Fig.4 A. According to Fig. 4B a second contact shaping substrate 21 is provided and second contact shaping substrate 21 is contacted with the second polymer liquid 8 located on the replicated lenses 6 present in plurality of recesses 3. This second polymer liquid 8 covers replicated lenses 6 completely as shown in Fig. 4B. The peripheral contour of second polymer liquid 8 is indicated with reference number 20. In Fig. 4C second polymer liquid 8 is cured by energy 4. I n Fig. 4D a step of removing first mold 1 after curing the second polymer liquid 8 for obtaining said array of optical lens elements is shown, comprising second contact shaping substrate 21 provided with cured second polymer and replicated lenses 6. Fig. 3D also shows the peripheral contour 20, 23 of cured second polymer, the post fill interface 19, 22. Fig. 3D shows a lateral curvature shape 20, 23 as a half moon shape. Fig.5 shows another embodiment of a second phase of the method of fabricating an array of optical lens elements. In Fig. 5A first mold 1 having a plurality of recesses 3 is provided with replicated lenses 6 therein. First mold 1 is provided with additional curvatures or slopes 25 between lenses 6. A second polymer liquid 8 is provided onto the surface of the plurality of replicated lenses 6 in Fig.5 A. According to Fig. 5B a second contact shaping substrate 24 is provided and second contact shaping substrate 24 is contacted with the second polymer liquid 8 located on the replicated lenses 6 present in plurality of recesses 3. This second polymer liquid 8 covers replicated lenses 6 completely as shown in Fig. 5B. The peripheral contour of second polymer liquid 8 is indicated with reference number 26. In Fig. 5C second polymer liquid 8 is cured by energy 4. In Fig. 5D a step of removing first mold 1 after curing the second polymer liquid 8 for obtaining said array of optical lens elements is shown, comprising second contact shaping substrate 24 provided with cured second polymer and replicated lenses 6.

Fig. 6A-E shows different contour variations of a lateral curvature shapes. In Fig 6A lens substrate 32 is provided with cured polymer 31 , wherein cured polymer 31 is provided with cured polymer 30. Cured polymer 31 covers cured polymer 30 completely. Fig. 6A further shows a flow stop zone 37, a lateral curvature shape 36, a lateral rim 35, post fill interface 34, clear aperture edge 33. All optical elements shown in Fig. 6A-6E have at least two contiguous resin material zones 30, 31 where the prefill/postfill interface 34 between the zones is positioned between the clear aperture edge 33 and outer edge 38 interfacing lens substrate 32. Shapes of lateral curvature 36 and lateral rim 35 are determined by local differences of surface tensions between the mold (not shown here) and lens substrate 32. Outer edge contours are determined by shape of flow stop zone 37. Fig. 6A, 6B, 6D and 6E show a lateral curvature shape 36 as a half moon shape. Fig. 6C shows a lateral curvature shape 36 as a bell clock curve shape.

Fig. 7 shows in Fig. 7A-7F different embodiments of a flow stop zone. Outer edge 41 contour is determined by shape of a thin flow 'stop" layer 42 or pattern with a different surface energy/ wettability acting as a flow stop for the liquid resin. Thickness of stop layer 42 is in the range of submicron down to molecular monolayer. Stop layer 42 may have any shape or pattern according to design. Contour of lens (clear aperture edge 40) is circular here but may have also any other shape (elliptical, cylindrical, truncated, connected.) according to optical design. Fig. 8 shows different embodiments of features 46, 47, 48, 49, 50, 51 for controlling resin flow. Patterns with locally modified surface tensions on molds and/or shaping substrates and/or lens substrates. Local modification can be chemical, by plasma (using masks), by laser or by applying thin films with specific surface tension. Patterns may be permanent and may have optical functions such as diaphragms or filters. Substrates are indicated by reference number 44, molds by reference number 45.

When a spreading droplet encounters a zone with different surface energy, the border between the two zones will act as a flow stop for the droplet. A substrate with pattern of contrasting surface energy patterns will therefore control the flow of resin droplet within a predetermined contours and direction. Thus, present Fig. 7 A-F illustrate some examples of substrates with surface energy patterns. Examples of techniques for creating flow stop patterns comprise, inter alia, screen printing, stamping, plasma treatment and lithographic methods. Alternatively, surface energy patterns may be written directly using a laser beam. Starting from multilayer precursors subtractive techniques such as laser ablation or etching techniques can also be used to obtain a surface energy patterned substrate.

The sag height of the replicated lens in the Z direction is determined with the distance between the shaping substrate (5,8, 12) and the mold 1 , as shown in the Figures. The sag height is obtained by precise control of the mutual position of the mold and shaping substrate in a replication machine. Alternatively, spacers between the shaping substrate and the mold may be used (not shown here). These spacers may be integrated on either the mold or the shaping substrate. The type of spacer does not influence the results in the present invention.

Further, an accurate resin droplet dispensing system is preferred to control the combined height, shape and contour of the replicated lens. This can be achieved trough needle dispensing, ink jetting or 3D printing methods, or a combination thereof.

It should be noted that the above methods to control the peripheral contour of a replicated lens through providing patterned surface energies operate in the X-Y direction, i.e. substrate surface. Apart from achieving specific contour shapes, the flow stops also act as containers for the height of the droplet by limiting the spread of the liquid at the flow stop contours. An excessive spread of the droplet may result in an unwanted height of the droplet below the designed sag height of the replicated lens.