WO2025153383A1

WO2025153383A1 - A method of manufacturing a matrix assembly of interconnected lenses

Info

Publication number: WO2025153383A1
Application number: PCT/EP2025/050414
Authority: WO
Inventors: Rifat Ata Mustafa Hikmet; Ties Van Bommel
Original assignee: Signify Holding BV
Current assignee: Signify Holding BV
Priority date: 2024-01-15
Filing date: 2025-01-09
Publication date: 2025-07-24
Anticipated expiration: 2026-07-15

Abstract

The invention provides a method for manufacturing a matrix assembly of interconnected lenses (20) comprising a plurality of lenses (22) arranged in a first direction (11) and a second direction (12) perpendicular to the first direction (11), by means of 3D printing using a 3D printer (500), wherein the matrix assembly of interconnected lenses (20) comprises a plurality of subassemblies of interconnected lenses (21), each subassembly of interconnected lenses (21) comprising a subset of the plurality of lenses (22) interconnected in the first direction (11), the plurality of subassemblies of interconnected lenses (21) being interconnected in the second direction (12) in at least one position. Each lens of the plurality of lenses (22) comprises a light input surface (221) and a light output surface (222), wherein the light output surface is at least partly convex, and the light input surface is at least partly concave, wherein the matrix assembly of interconnected lenses (20) comprises one or more open spaces (23), each open space (23) being located in between two subassemblies of interconnected lenses (21) of the plurality of subassemblies of interconnected lenses (21), a surface area (231) of the one or more open spaces (23) being at least 30% of a surface area (201) of the matrix assembly of interconnected lenses (20), and wherein the 3D printer (500) comprises a vessel (510) for holding a 3D printable material (511) being polymerizable at a curing wavelength, a light emitting element (520) and a light modulating element (522) for exposing the 3D printable material (511) to patterned light comprising the curing wavelength, and a carrier platform (530) using an elevator mechanism (540) to advance a distance between the carrier platform (530) and the light emitting element (520) to form successive layers of 3D printed material (223) by exposing each layer of 3D printable material (511) to the patterned light. The method comprising printing the matrix assembly of interconnected lenses (20) by printing a stack of layers (223) having a stacking direction extending in parallel to the first direction (11) such that successive layers (223) of 3D printed material are oriented in the second direction (12).

Description

A method of manufacturing a matrix assembly of interconnected lenses

FIELD OF THE INVENTION

The invention relates to a method of manufacturing a matrix assembly of interconnected lenses by means of 3D printing. The invention also relates to a lighting device comprising a matrix LED panel and the matrix assembly of interconnected lenses. The invention further relates to a computer program product comprising instructions which, when the computer program product is executed by the 3D printer, cause the 3D printer to carry out the method of manufacturing.

BACKGROUND OF THE INVENTION

Digital manufacturing is expected to increasingly transform the nature of global manufacturing. One of the main processes used in digital manufacturing is 3D printing. The term “3D printing” refers to processes wherein a material is joined or solidified under computer control to create a three-dimensional object of almost any shape or geometry. Such three-dimensional objects are typically produced using data from a three-dimensional model, and usually by successively adding material layer by layer.

Many different 3D printing technologies are known in the art.

For example, US8998601B2 discloses a stereolithography machine comprising a tank suited to contain a liquid substance; a supporting plate; emitter means suited to direct a predefined electromagnetic radiation towards the tank; a holding unit of the tank operatively associated an actuator means configured so as to move the tank with respect to the supporting plate according to a predefined trajectory of movement.

3D printing technologies, such as stereolithography (SLA) or digital light processing (DLP) make use of photosensitive resins which can be polymerized by UV, violet or blue light to create 3D objects. Such 3D printing technologies can produce highly detailed and accurate prints, with resolution down to a few microns depending on the size of the object. The 3D printer prints the 3D object by polymerization (solidifying) the liquid resin, layer by layer, according to the digital design representation of the object. As each layer is partially polymerized, the distance between the carrier platform and the print bed is increased, allowing the printer to add the next layer until the entire object is complete. Once the printing is finished the object is then subjected to flood light exposure for polymerizing the unreacted groups within the resin and make it ready for use. Such 3D printers are known for their high accuracy and speed, making them ideal for creating highly detailed and complex objects. The technique is also being further developed in the production of LED luminaires and lighting solutions.

For this and other purposes, it is desired to manufacture optical elements with good performance and smooth surfaces using 3D printing. Nex to that, especially lens plates comprising multiple lenses face the additional challenge of buildup of internal stress and deformation caused by shrinkage of the 3D printed material. Currently single lenses and micro-lens arrays may be manufactured using material jetting 3D printing. This 3D printing technique is however limited in the types of lenses or lens arrays that may be produced and generally requires printing on a substrate becoming part of the final product. Furthermore, this method can not be used for producing lenses or lens arrays having a structure on both surfaces (i.e. lenses which are not planar on one of the surfaces).

US11400668B2 discloses a 3D printing process for producing a spectacle lens. The process includes providing a coated substrate, providing at least one printing ink, typically a 3D printing ink, building up the spectacle lens from the sum of the individual two- dimensional layers with a printing operation on the substrate, and hardening of the spectacle lens.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partly overcome one or more of the aforementioned disadvantages of the prior art, or to provide a useful alternative.

In a first aspect, the invention provides a method for manufacturing a matrix assembly of interconnected lenses comprising a plurality of lenses arranged in a first direction and a second direction perpendicular to the first direction, by means of 3D printing using a 3D printer. The matrix assembly of interconnected lenses comprises a plurality of subassemblies of interconnected lenses, each subassembly of interconnected lenses comprising a subset of the plurality of lenses interconnected in the first direction, the plurality of subassemblies of interconnected lenses being interconnected in the second direction in at least one position. Each lens of the plurality of lenses comprises a light input surface and a light output surface, wherein the light output surface is at least partly convex, and the light input surface is at least partly concave. The matrix assembly of interconnected lenses comprises one or more open spaces, each open space being located in between two subassemblies of interconnected lenses of the plurality of subassemblies of interconnected lenses, a surface area of the one or more open spaces being at least 30% of a surface area of the matrix assembly of interconnected lenses. The 3D printer comprises a vessel for holding a 3D printable material being polymerizable at a curing wavelength, a light emitting element for exposing the 3D printable material to light comprising the curing wavelength, and a carrier platform using an elevator mechanism to advance a distance between the carrier platform and the light emitting element to form successive layers of 3D printed material by exposing each layer of 3D printable material to the light, the method comprising printing the matrix assembly of interconnected lenses by printing a stack of layers having a stacking direction extending in parallel to the first direction such that successive layers of 3D printed material are oriented in the second direction.

The matrix assembly of interconnected lenses obtained by this method may have a good optical performance while being free from warping and deformations to a large extent. By printing the lens assembly such that the stack of layers extends in parallel to the first direction in combination with the open spaces in between the subassemblies, the deformation forces can be significantly reduced. Additionally, the method of this invention makes it possible to print a lens assembly of interconnected lenses in which both the light input surface as well as the light output surface of the plurality of lenses are at least partially convex or concave.

In other words, a method is provided for manufacturing a lens array by means of stereolithography. The lens array may have a first plurality of lenses and a second plurality of lenses, the first plurality of lenses may have a first lens and a second lens interconnected in a column direction and the second plurality of lenses may have a third lens and a fourth lens interconnected in the column direction. The first plurality of lenses may be interconnected to the second plurality of lenses in a row direction, the row direction being perpendicular to the column direction. The lens array may have an open space located between the first plurality of lenses and the second plurality of lenses, a surface area of the open space being at least 30% of a surface area of the lens array.. Each lens of the lens array may have a first surface and a second surface, the first surface being at least partly concave, and the second surface being at least partly convex. The method may comprise the step of moving a build platform in a platform direction, and the platform direction may be parallel to the column direction.

The method comprises the step of layer-wise adding a 3D printable polymerizable material to form a 3D printed object. Herein, the term “3D printable material” refers to the material to be cured or printed, and the term “3D printed material” or “polymerized material” refers to the material that is obtained after polymerizing a layer of 3D printable material (i.e. by exposing a layer to patterned light which initiating polymerization). The 3D printable material is typically provided in a liquid form which is provided in a vessel or vat of the 3D printer.

Herein, the term “3D printable material” may also be indicated as “printable material”, “polymerizable material” or simply “resin”. The term “3D printed material” may also be indicated as “printed material” or “polymerized material”. The term “polymerizable material” may refer to a blend or mixture of different materials as described below but may also refer to essentially a single type of material.

Materials that may qualify as 3D printable material in the above-described method may include liquid resins, also known as photopolymers or light-reactive cross linkable materials. This group of 3D printable materials can be solidified or polymerized when exposed to certain wavelengths of light. Under the exposure to their respective curing wavelengths molecules with reactive groups react with each other, polymerizing the liquid resin into solidified rigid or flexible objects.

Photopolymer resins may comprise monomers, oligomers, and photo initiators. Monomers may comprise small molecules that can react with other monomers to form long chains of polymers which are cross-linked. Monomers may comprise reactive groups such as acrylic, vinyl groups, epoxy groups which can be cross-linked by exposure to (UV, violet, or blue) light in the presence of a photo initiator. Oligomers are larger molecules that may be made of an acrylic or vinyl main chain designed to have specific properties, such as flexibility, toughness, or heat resistance. Oligomers may also have reactive groups. Photo initiators are chemicals that absorb (UV, violet, or blue) light, thereby generating free radicals which may initiate a polymerization reaction which leads to a cross-linking reaction between monomers and/or oligomers. Photo initiators may be added to the resin to initiate a polymerization reaction and to ensure rapid curing. Photopolymer resins may additionally comprise additives, such as pigments, fillers, or stabilizers, to enhance their performance and appearance.

Resins may also comprise excited state quenchers, UV -violet light absorbers as well as thermal polymerization initiators. Thermal initiators may help to induce polymerization of unreacted groups upon heating the matrix assembly of interconnected lenses. The 3D printable material may additionally comprise thermally polymerizable components, such as epoxy-amine systems, which may be polymerized by a heating step. The 3D printable material may comprise a material having an acrylate group and a photo initiator activated by the curing wavelength selected from a range of 100 nm - 450 nm.

The material may have one or more acrylate groups, such as a mono acrylate, diacrylate, tri acrylate, or tetra acrylate. The material may comprise for example acrylic acid, methyl methacrylate (MMA), polymethyl methacrylate (PMMA), ethyl acrylate, butyl acrylate, or 2-Hydroxyethyl methacrylate (HEMA) oligomers. To induce cross-linking acrylates with two or more reactive groups may be used. Systems with multiple reactive groups may increase the rate of polymerization.

The 3D printer used in the above-described method comprises a vessel for holding a 3D printable material being polymerizable at a curing wavelength, a light emitting element in combination with light modulating element for exposing the 3D printable material to light comprising the curing wavelength, and a carrier platform using an elevator mechanism to advance the carrier platform away from the light emitting element to form successive layers of 3D printed material by exposing each layer of 3D printable material to patterned light.

A 3D printer as described above is generally known in the art and will not be described in detail. Such a 3D printer may typically be used for stereolithography (SLA), which may also be referred to as vat polymerization, optical fabrication, photo-solidification, or resin printing. The term “SLA” may generally refer to laser stereolithography but also includes other technologies such as DLP (digital light processing), LCD (liquid crystal display) and MSLA (masked stereolithography). Instead of the term “3D printer” the terms “SLA printer” or “printer” may be used.

Laser SLA printers use a laser light source and a light modulating element configured to trace out print layers point by point. When a laser is used as a light emitting element, then patterned light exposure can be obtained by scanning the laser. In DLP the light source is a projector instead of a laser. DLP printers can cure a complete layer at once. Similar to DLP, MSLA solidifies entire layers at once. Instead of a projector, however, MSLA printers leverage an array of LEDs as a light source. The LEDs shine through a LCD screen, which selectively masks the light by illuminating or turning off specific pixels. An MSLA printer’s resolution hence depends on its LCD screen’s resolution. MSLA is also often referred to as LCD 3D printing. Light modulating or light patterning may thus be done using a pixelated image forming element such as a liquid crystal display or an image forming projection element such as DMD (digital micro mirror device). The “light modulating element” may also be indicated as “image forming element”.

The 3D printed object is typically printed onto the carrier platform, which may include directly printing on the carrier platform, or printing on a coating on the carrier platform, or printing on 3D printed material earlier printed on the carrier platform. The term “carrier platform” may refer to a printing platform, a build platform, a print bed, a print surface, a substrate, etc..

The term “matrix assembly of interconnected lenses” may also be indicated as “matrix assembly” or “lens assembly”. Structural aspects of the matrix assembly will be described in more detail below.

The matrix assembly of interconnected lenses comprises a plurality of lenses arranged in a matrix extending in a first direction and a second direction, thus having multiple rows and columns. The first and second direction may both be substantially perpendicular to the optical axis of each lens of the plurality of lenses. The method comprises printing the matrix assembly of interconnected lenses by printing a stack of layers having a stacking direction extending in parallel to the first direction such that successive layers of 3D printed material are oriented in the second direction. Each layer of 3D printed material is thus arranged such that it creates a plane defined by a vector in the second direction and a vector perpendicular to the first direction and the second direction.

In other words, the plurality of lenses of the lens assembly are not printed all at once, built up layer by layer, starting from light input surface to light output surface. The lens assembly is thus not printed resting flat on the print bed. Instead, the matrix assembly of interconnected lenses is printed row by row, such that each layer extends from the light input surface to the light output surface of each lens. The lens assembly is thus printed standing up on one of its sides, i.e., 90° or perpendicular with respect to the light output surface. If comparing the matrix assembly to a simplified rectangular plate, the stack of layers is therefore not built up in the thickness direction but in the length or width direction, depending on the dimensions of the matrix assembly. This significantly reduces the deformation stress and warpage experienced by the matrix assembly. The lens assembly may also be placed onto the print surface at an angle in the range 80° - 110° with respect to the light output surface.

Each layer of the stack of layers may have a layer height being in a range of 20

- 100 micrometers. The lens assembly is built up of a stack of layers in which the layer height or step height is chosen to be within a certain range, such as between 10-200 micron, preferably between 20-100 micron. In this range, the optical performance of the lenses may be optimized.

Each layer of the stack of layers may have a layer height or step height within this range. All layers within the stack of layers may have the same layer height. However, the layer height may also vary within this range within the stack of layers from layer to layer.

A surface of the matrix assembly of interconnected lenses may comprises an excess 3D printable material. In such examples, the method may subsequently further comprises one or more of removing at least part of an excess 3D printable material, distributing at least part of an excess 3D printable material present across the surface of the matrix assembly of interconnected lenses, and exposing the matrix assembly of interconnected lenses to light comprising the curing wavelength.

An object created using resin printing may carry excess resin on its surface after all layers of the stack of layers have been created using the 3D printing process. Alternatively or additionally, the excess 3D printable material may be applied to the surface of the matrix assembly of interconnected lenses after 3D printing. In such examples, the excess 3D printable material may be the same material used for 3D printing, but may also be a different (i.e. photo or heat) polymerizable material. The one or more of the above- mentioned additional steps may be executed with the aim to remove excess resin from the surface and/or spread excess resin across the surface of the lens assembly, and/or to cure the complete lens assembly after the lens assembly has been created by the 3D printer.

The layers created by the 3D printer form a roughness on the surface of the produced item, in particular the surface of the lenses. The surface roughness is most visible when, after printing, excess (not polymerized) resin on the surface of the object is removed by a washing step. Washing a 3D printed object may (depending on the resin used for printing) be for example performed by dunking the object (multiple times) into a tub containing a washing fluid (i.e. isopropyl alcohol (IP A), tripropylene glycol monomethyl ether (TPM), dipropylene glycol monomethyl ether (DPM), or water) and subsequently rinsing it, or by cleaning the object using an ultrasonic bath. After such a washing step a layer of polymerizable resin material may be placed on the surface of the lenses for coating and therewith covering the surface roughness. The thickness of this coating layer may be balanced to be thick enough to remove the surface roughness but not too thick so as to alter the working of the lens function. Alternatively or additionally, the carrier platform may be mounted to a rotor for spinning the rotor with the carrier platform connected thereto while the matrix assembly of interconnected lenses remains connected to the carrier platform to remove excess resin from the surface of lenses. The matrix assembly of interconnected lenses may be exposed to light comprising the curing wavelength. In some cases, after printing there might be not enough resin on the matrix assembly of interconnected lenses therefore extra resin may be added. The matrix assembly of interconnected lenses produced by 3-D printing may thus comprise an additional layer which is produced after the 3D printing.

After the 3D printing process is completed, the carrier platform still carrying the matrix assembly of interconnected lenses may be transferred to a rotor. The matrix of interconnected lenses may alternatively be removed from the printing platform and placed onto another platform for spinning. The rotor may have means for removably securing the carrier platform and means for rotating the carrier platform around an axis to centrifugally spin off surplus resin which may have remained on the matrix assembly surface. The rotor may for example be driven by electric, pneumatic, or hydraulic drives. The rotor may be rotated at any rotation speed suitable (i.e. at a speed higher than one cycle per second), and for the time period needed. The spinning aims to remove the surplus resin but to leave a layer thick enough for inducing a smooth layer on top of the matrix assembly of interconnected lenses. The thickness of the coating layer may balance creating a smooth layer on top of the lenses, however not being too thick so as to adversely affect the optical function of the matrix assembly of interconnected lenses. The rotation speed and time period may thus depend on several factors, such as the viscosity of the resin and the geometry of the matrix assembly.

The matrix assembly of interconnected lenses may additionally be exposed to light comprising the curing wavelength (also referred to as “curing light”). This step may also be referred to as “curing” or “post-curing” of the 3D printed matrix assembly and may be completed for purposes such as additional strength, stability, reducing surface stickiness, or temperature resistance. Post curing may be done in several steps. For example, during the last step of spinning the matrix assembly of interconnected lenses may be subjected to polymerization radiation, preferably in an atmosphere containing no oxygen such as nitrogen atmosphere. In a second step, the temperature of the matrix assembly of interconnected lenses may be increased to enable polymerization of unreacted groups and also in case the resin comprised groups or monomers which can be thermally polymerized.

The step of spinning the matrix assembly on the rotor and the step of exposing the matrix assembly to curing light may thus be executed sequentially or may alternatively overlap in time, such as partly overlap in time, or entirely overlap in time. The step of spinning the matrix assembly on the rotor and the step of exposing the matrix assembly to curing light may be performed by the same device having means for rotating the matrix assembly and means for exposing the matrix assembly to curing light. Alternatively, the steps of rotating the matrix assembly and exposing the matrix assembly to curing light may be performed by different devices or at different locations.

In a second aspect, the invention provides a computer program product comprising instructions which, when the computer program product is executed by a 3D printer, cause the 3D printer to carry out the method according to the first aspect.

In a third aspect, the invention provides a lighting device comprising a matrix lighting panel comprising a plurality of light sources arranged in a matrix configuration on a carrier, and a 3D printed matrix assembly of interconnected lenses comprising a crosslinked polymer, the matrix assembly of interconnected lenses being mounted over the matrix LED panel. The 3D printed matrix assembly of interconnected lenses comprises a plurality of lenses distributed in a first direction and in a second direction, the 3D printed matrix assembly of interconnected lenses comprising a plurality of subassemblies of interconnected lenses, each subassembly of interconnected lenses comprising a subset of the plurality of lenses interconnected in the first direction. The plurality of subassemblies of interconnected lenses are interconnected in the second direction in at least one position. Each of the plurality of lenses comprises a light input surface and a light output surface, the light output surface being at least partly convex, and the light input surface being at least partly concave. The 3D printed matrix assembly of interconnected lenses comprises one or more open spaces located in between the plurality of subassemblies of interconnected lenses, and a surface area of the one or more open spaces is at least 30% of a surface area of the 3D printed matrix assembly of interconnected lenses.

A lighting device comprising the 3D printed matrix assembly of interconnected lenses has multiple advantages compared to a lighting device having a solid lens plate as is known in the art. The 3D printed matrix assembly of interconnected lenses is flexible and thus adapts to the shape of the matrix LED panel when mounted over the matrix LED panel. Additionally, the 3D printed matrix assembly of interconnected lenses is lightweight and can be produced using significantly less material compared to a solid lens plate without compromising on the optical performance of the plurality of lenses comprised by the matrix assembly. The 3D printed matrix assembly of interconnected lenses is described for use in a lighting device, such as an outdoor lighting device, an indoor lighting device, or an automotive lighting device. However, the matrix assembly of interconnected lenses may be equally suitable for use in other types of devices, such as cameras, microscopes, telescopes, projectors, 3D printers, or virtual reality headsets.

The matrix may have a size of at least 3 columns (extending in the first direction) and 3 rows (extending in the second direction), thus may comprise at least 9 lenses.

The lighting device comprises a matrix lighting panel comprising a plurality of light sources arranged in a matrix configuration on a carrier. The lighting device may especially comprise a plurality of solid state light sources, such as a light emitting diode (LED). The light sources may be configured to generate light, especially visible light, i.e., light with spectral power in the visible wavelength range (380-780 nm). Especially, the light may be white light. More especially, the white light may have a correlated color temperature selected from the range of 1800-6500 K and/or a color rendering index of at least 70, such as at least 80. However, the light may also be colored light. The light may have a wavelength in one of the UV and IR wavelength ranges to be used in application such as disinfection, radar as Lidar (750 nm to 1.5pm) and LiFi applications.

The term “light source” may in principle relate to any light source known in the art. It may be a conventional light bulb, a low pressure mercury lamp, a high pressure mercury lamp, a fluorescent lamp, an LED (light emissive diode). The light source may comprise a solid state light source (such as an LED or laser diode (or “diode laser”)). The term “light source” may also relate to a plurality of light sources, such as 2-2000 (solid state) LED light sources. Hence, the term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so-called chip-on-board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB.

The term “light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser, etc... The term “light source” may also refer to an organic light-emitting diode (OLED), such as a passive-matrix (PMOLED) or an active-matrix (AMOLED). The terms “light source” or “solid state light source” may also refer to a superluminescent diode (SLED).

The light source may especially be configured to generate light having an optical axis (O), (a beam shape,) and a spectral power distribution. The light may comprise one or more bands, having band widths as known for lasers. The term “light source” may (thus) refer to a light generating element as such, like e.g. a solid state light source, or e.g. to a package of the light generating element, such as a solid state light source, and one or more of a luminescent material comprising element and (other) optics, like a lens, a collimator. A light converter element (“converter element” or “converter”) may comprise a luminescent material comprising element. For instance, a solid state light source as such, like a blue LED, is a light source. A combination of a solid state light source (as light generating element) and a light converter element, such as a blue LED and a light converter element, optically coupled to the solid state light source, may also be a light source (but may also be indicated as light generating device). Hence, a white LED is a light source (but may e.g. also be indicated as (white) light generating device).

The carrier may for example be a printed circuit board (PCB) and may be configured to support the plurality of light sources. Especially, the plurality of light sources may be configured on the carrier in a matrix configuration. Hence, the light sources may be physically coupled to the carrier. Further, plurality of light sources may also be electrically connected to the carrier, i.e., the carrier may be configured to provide electricity to the light sources. The carrier may be flat such that the lighting matrix is flat. Alternatively, the carrier may be uneven or may have a shape, such as having a curved surface. Examples may be imagined in which different rows or different columns of the matrix lighting panel have a different carrier shape.

The term “arranged in a matrix configuration” in the context of this invention describes a plurality of light sources arranged in a preferably rectangular configuration, although other shapes may also possible. The light sources may be configured in plurality of columns extending in a first direction and a plurality of rows extending in a second direction.

The 3D printed matrix assembly of interconnected lenses comprises a crosslinked polymer. The cross-linked polymer can be obtained using a monomer or a monomer mixture comprising bifunctional, trifunctional, tetra functional, and/or higher functional groups. In a mixture with multi-functional groups a monomer with a mono-functional groups may be used for decreasing the cross-link density within the polymer. Cross linked polymers, also known as thermoset polymers (when thermally induced cross-linking is used), may for example be based on one or more of acrylates, epoxy-amine, epoxy-anhydride, vinyl ethers, thiol-ene systems, polyurethane, epoxy, and phenolic resins. To obtain photo polymerized cross-linked polymer, reactive monomers with two or more functional groups may be used. Groups between functional groups such as alkene or alkoxy chains, phenyl and/or bisphenol- A groups may form the cross links between the main chain (meta) acrylate or vinyl polymer. For example, decan diol diacrylate, Trimethylolpropane trimethacrylate (TMPTMA), bisphenol-A diacrylate, Glyceryl propoxy triacrylate (GPTA), etc. are well known acrylates which can be used for printing. The cross-linked polymer may be obtained by the 3D printing method according to the first aspect using the above-described materials.

The 3D printed matrix assembly of interconnected lenses may be manufactured using the method according to the first aspect. However, also alternative methods for manufacturing may be used, such as different methods for resin printing, or alternative printing techniques such as material jetting or fused deposition modelling (FDM). Each of the plurality of lenses comprises a light input surface and a light output surface, the light output surface being at least partly convex, and the light input surface being at least partly concave. Each of the plurality of lenses is thus curved on both surfaces, creating a plurality of concavo-convex lenses.

The light input surface needs to be understood as the surface of the lens which is facing the light source and thus directly receives the light emitted by the light source. This surface is at least partly concave or hollow so that a cavity may be created for receiving at least part of the light source when the matrix assembly is mounted over the matrix lighting panel. The height of the cavity may in examples have at least the dimensions of the light source, such as the width, length, and height of the light source mounted on the carrier.

The light output surface needs to be understood as the surface of the lens which faces away from the light source and which outputs the light received on the light input surface to the surroundings of the lighting device. The light output surface is at least partly convex or curved outwards.

The matrix assembly of interconnected lenses comprises a plurality of subassemblies of interconnected lenses. Each subassembly of interconnected lenses comprising a subset of the plurality of lenses interconnected in the first direction.

As described above, the matrix assembly of interconnected lenses comprises a plurality of lenses arranged in a first direction and in a second direction, configured to be mounted on the matrix lighting array. Contrary to a lens plate known in the art, the plurality of lenses is not embedded in a solid lens plate. The plurality of lenses is arranged in a plurality of subassemblies, each comprising a subset of multiple lenses of the plurality of lenses. Each of the multiple lenses in the subassembly is interconnected with its neighboring lenses of the same subassembly in the first direction. The subset of lenses comprised by a subassembly may be positioned in different arrangements, such as for example in on a straight line extending in the first direction, a curved line extending in the first direction, or in a zigzag pattern extending in a first direction. The plurality of subassemblies may be arranged adjacent to each other in the second direction, preferably may be arranged in parallel to each other. However, the plurality of subassemblies is not interconnected by a solid lens plate. In fact, the subset of lenses in one subassembly may not be directly interconnected at all in a second direction to lenses in a neighboring subassembly. Such examples may provide a matrix assembly of interconnected lenses with the highest flexibility and lowest material use.

The subassemblies of interconnected lenses are interconnected in the second direction in at least one location with the aim to create one single matrix assembly of interconnected lenses which has additional stability, and which can be mounted to the matrix lighting panel in a single assembly step. Each of the plurality of subassemblies of interconnected lenses comprises a proximate end and a distal end. Preferably, the proximate ends and/or the distal ends may be interconnected in the second direction. An interconnection in the second direction may however also be realized at any intermediate location in between the proximate end and the distal end along the subassembly of interconnected lenses.

Hence, the 3D printed matrix assembly of interconnected lenses comprises one or more open spaces located in between the plurality of subassemblies of interconnected lenses. The term “open spaces” needs to be understood as an area of the matrix assembly not covered by matrix lens assembly material. In other words, the matrix assembly thus comprises one or more openings, apertures, gaps, or holes, of the one or more open spaces is at least 30%, at least 40, such as at least 50% of a surface area of the 3D printed matrix assembly of interconnected lenses. The surface area of the 3D printed matrix assembly of interconnected lenses needs to be understood as the area described by the outer perimeter of the matrix assembly of interconnected lenses.

Each of the plurality of lenses may correspond to one of the plurality of light sources comprised by the matrix lighting panel.

In such examples the amount and distribution of lenses comprised by the matrix assembly of interconnected lenses may equal the amount and distribution of light sources comprised by the matrix lighting panel. Hence, each light source may aligned with one of the plurality of lenses, which may be beneficial for the optical performance and light distribution of the lighting device.

Each subassembly of interconnected lenses may comprise one or more interconnects interconnecting adjacent lenses of the subset of the plurality of lenses, and the one or more interconnects may have a bar shape having a width W1 measured in the second direction which is in the range of 1 mm < W1 < 5 mm.

To increase the flexibility and decrease the material usage of the matrix assembly of interconnected lenses, the subset of lenses comprised by each subassembly may be interconnected by bars of 3D printed material. These bars or lines connecting the lenses may have a width which is wide enough to create a stable interconnection between adjacent lenses, but may be thin enough to ensure flexibility, low material usage, and to avoid warping and deformation of the lens plate. To this end, the width W1 of the bar shaped interconnects may be smaller than 15 mm, smaller than 10 mm, such as in the range of 1 mm < W1 < 5 mm.

The term “bar-shaped” in the context of this inventions needs to be interpreted as generally or approximately rectangular or bar shaped. However, the skilled person understands that the same effect may be achieved with interconnects which are not rectangular or bar-shaped at all. Interconnects may for example have rounded comers, curved surfaces, an S shape, a zig zag pattern, a diamond shape, or may have a cross-section which is triangular, circular, or semi-circular. The most suitable shape for the interconnects may be determined so as to minimize the warpage of the matrix assembly.

The interconnects may have a surface having a surface roughness which is larger than 5 micrometers, and the interconnects may further comprise geometrical structures comprising repeating units having open cell structures.

Interconnects having a rough or (micro) structured surface, thus having an increased surface roughness, may have the advantage of preventing light leakage from the light sources and lenses into the interconnects. The surface roughness may preferably be in a range of 1-100 micrometers, preferably 5-30 micrometers. The light distribution may thus be improved with the light being mainly emitted from the light output surface of the plurality of lenses and less light may leak and be emitted from the interconnects. This effect can be further enhanced by additional geometrical structures comprising repeating units having open cell structures. Hence, the interconnects may not be made solid but may comprise open structures further contributing to a reduced light leakage and to an even further decreased material usage. Such structures and surfaces may be easily manufactured using 3D printing techniques.

At least one subassembly of interconnected lenses may comprise mounting means for mounting the matrix assembly of interconnected lenses over the matrix lighting panel. The mounting means may facilitate alignment of the matrix assembly of interconnected lenses with the matrix lighting panel and may serve to securely mount the matrix assembly of interconnected lenses over the matrix lighting panel. Preferably, the mounting means may be comprised by the interconnects. In this way the mounting means do not interfere with the optical performance of the lighting device and may be located in positions convenient for stable fixation. The mounting means may for example be circular holes, such as pin holes configured to receive screws or pins for fastening the matrix assembly over the matrix lighting panel. However, the mounting means may alternatively also be holes of any other shape (e.g. oval, square) or other mounting means such as clips, hooks, or protrusions.

The open spaces may extend to at least 90% of the surface area of the 3D printed matrix assembly of interconnected lenses not being covered by the plurality of subassemblies of interconnected lenses.

The surface area of the 3D printed matrix assembly of interconnected lenses comprises surface areas covered by the plurality of lenses and surface areas not covered by the plurality of lenses, thus the surface area in between the lenses. As described above, the surface area in between the lenses, in particular the surface area in between the subassemblies of interconnected lenses comprises open spaces. At least 70%, at least 80%, such as at least 90% of the surface area in between the lenses may be implemented as open space. In other words, the matrix assembly of interconnected lenses may have material only in such surface areas that are covered by lenses or covered by interconnects and may have open spaces in all areas not covered by lenses or interconnects. Larger open spaces may increase the flexibility of the matrix assembly of interconnected lenses as well as reduce the material usage.

Each of the plurality of lenses may comprise an optically active area and an optically inactive area together forming a total area of each of the plurality of lenses. The optically inactive area may form less than 40% of the total area of each of the plurality of lenses.

The optically active areas of the plurality of lenses may be at least partially embedded in optically inactive areas. In a standard, solid lens plate these optically inactive areas make up the areas of the lens plate not covered by lenses. In the lens assembly described above, the optically inactive areas around the lenses may be minimized and made to follow the contours of the optically active areas of the lenses. Smaller optically inactive areas may result in less warpage or deformation of the matrix assembly of interconnected lenses. The optically inactive areas may comprise round edges or straight edges. The optically inactive areas may form preferably less than 40%, more preferably less than 30%, and most preferably less than 20% of the total area of the plurality of lenses.

Each lens of the plurality of lenses may have a substantially elliptical shape, and the major axis of the ellipse may be oriented in the first direction.

Lenses having a substantially elliptical shape may be well suited for this use in the lighting device described above. The elliptical shape may extend in the first direction and the second direction, with the major axis extending in the first direction and the minor axis extending in the second direction. In other words, the longer axis of the ellipse may be oriented in line with the interconnects, while the shorter axis of the ellipse may be oriented perpendicular to the interconnects. This configuration may be especially successful in minimizing warpage and deformation.

Each lens of the plurality of lenses may be a peanut-shaped lens.

Peanut-shaped lenses are commonly used in the art in lighting devices, especially for applications in outdoor lighting, such as in lighting devices for road or street lighting. Peanut-shaped lenses may be used on their own as a single lens but are often embedded in lens plates, typically manufactured by extrusion. Peanut-shaped lenses may have a curved, at least partly convex light output surface, remotely resembling the doublecurved shape of a peanut. On the light input surface, the lens may typically comprise a hollow cavity which is at least partly concave so as to be mounted on top of a light source. Due to their rather complex shape, producing peanut-shaped lenses with a good optical performance and little deformation using 3D printing faces many challenges. Even more so when attempting to manufacture a lens assembly comprising multiple peanut-shaped lenses using 3D printing. The above-described method for manufacturing a matrix lens assembly of interconnected lenses may be especially suitable to manufacture a lens assembly comprising peanut-shaped lenses.

Each lens of the plurality of lenses may comprise a stack of layers having a stacking direction extending in parallel to the first direction, and the stack of layers may be created using 3D printing.

Each lens of the 3D printed matrix assembly of interconnected lenses may comprise a stack of layers. Each layer of the stack of layers may be oriented in parallel (with an angle of up to ± 10°) to the second direction, while the layers may have a stacking direction in parallel to the first direction. Layers or print lines which are oriented in this way may result in a beneficial and more uniform light distribution of the lighting device. The 3D printed matrix assembly of interconnected lenses may comprise a coating covering at least part of a surface of the 3D printed matrix assembly of interconnected lenses.

Coating at least part of the 3D printed matrix assembly of interconnected lenses may improve the optical performance of the lighting device. In examples, one or more of the plurality of lenses may comprise a coating. Such a coating may result in an increased smoothness of the lens surface and thereby improve the optical performance of the lens. In other examples, the whole lens plate may be coated. Such a coating may for example be applied for additional scratch-resistance of the surface or a desired appearance or finish of the surface. The coating may comprise the same material as the 3D printed layers of the matrix assembly but may alternatively or additionally also comprise a different material having different properties, such as different optical properties (e.g. different scattering, light diffusion, color, ... ), or different mechanical properties.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Fig. 1 shows some general aspects of a 3D printer and of the method;

Fig. 2 schematically depicts an example of the lighting device;

Figs. 3A-3B schematically depict aspects of the matrix assembly of interconnected lenses;

Figs. 4a-4e show examples of the matrix assembly of interconnected lenses; Fig. 5 schematically depicts aspects of a single lens of the plurality of lenses. Figs. 6A-6B schematically depict additional aspects of a single lens of the plurality of lenses; and

Figs. 7A-7C show examples of single lenses.

The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 shows in a highly schematic form a 3D printer 500 comprising a vessel 510 for containing a 3D printable material 511 which is polymerizable at one or more curing wavelengths of radiation. The 3D printable material may be, for example, a polymerizable resin, adhesive, monomer, oligomer, prepolymer, a colloidal suspension, etc. The 3D printer 500 also comprises a carrier platform 530, which is coupled to an elevator or drive mechanism 540 for moving the build platform 530 towards and away from a light emitting element 520. In the example illustrated in Fig. 1, the light emitting 520 is located below a light modulating element 522 being in optical contact with a window 521 at the bottom of the vessel 510 and the build platform 530 is lowered (i.e. moved towards) or raised (i.e. moved away) in a first direction 11 with respect to the light emitting element 520.

To print the first layer 223 of a three-dimensional object 20, the carrier platform 530 moves to a position such that a thin layer of 3D printable material 511 is sandwiched between the build surface of the carrier platform 530 and the window 521. After the 3D printable material has been exposed to patterned light comprising the curing wavelength from the light modulating element 522 which modulates light from the light emitting element 520, the exposed region will have polymerized or solidified to form a layer of 3D printed material 223 adhering to the carrier platform 530. After the first layer of resin 223 is cured, the carrier platform 530 is moved in a first direction 11 away from the window. Successive layers 223 of the 3D object 20 are progressively added to the build platform 530 to form a stack of layers of 3D printed material 223, as will be described in more detail below.

The 3D printer 500 further comprises a light emitting element 520, also referred to as curing unit, which is configured to emit radiation at the one or more curing wavelengths, through the window 521 and into the volume of vessel 510, in order to selectively cure portions of the polymerizable material 511 in the vessel 510. To this end, the window 521 is at least partially transparent (e.g., fully transparent or translucent) to the radiation emitted by the light emitting element 520. For example, if the radiation source of light emitting element 520 is a violet light or UV radiation source, then the window 521 is at least partially, and preferably completely, transparent to violet or UV radiation, or at least to wavelengths which correspond to one or more peaks of the emission spectrum of the radiation source.

The light modulating element 522 may be a dynamic mask in the form of a liquid crystal display (LCD). The LCD forms part of a programmable radiation module which can be configured to produce a patterned beam of radiation to cure a layer of resin in the vessel 510 with a desired pattern. The pixels of the LCD may constitute individually addressable elements which may be switched on or off by a control system 550 of the 3D printer 500 or functionally coupled to the 3D printer 500 and to the LCD. When a pixel is activated (switched on), it allows light to be transmitted through it, whereas when it is inactive (switched off), it blocks light. Accordingly, the pixels of LCD are individually addressable light transmitters which can be programmed by the control system 550 to produce the desired pattern of radiation, with the inactive pixels acting as masking elements.

The LCD may preferably be monochrome LCD. For printing applications, light in the ultraviolet (UV) or true violet (TV) range may be most effective, as each photon carries a relatively large amount of energy. The wavelength for these photons ranges from approximately 100-41 Onm, preferably from 300-450 nm.

The light emitting element 520 may comprise a panel of individually addressable light emitters in an array, such as an LED or OLED display. In similar fashion to the LCD 32, the panel can be programmed by the controller 550 such that selected light emitters are active at any given time, in order to produce the desired pattern of radiation. In such examples, the individually addressable elements of the radiation module themselves emit the radiation in the desired curing pattern, rather than acting as a mask for a separate radiation source. LEDs and Organic LEDs can in principle be designed to emit any particular wavelength of light (visible, UV, IR) to match the specific curing requirement of the polymerizable material 511.

The light emitting element 520 may be a point emitter such as a bulb or LED light or a panel having an array of such point emitters. It may also be a laser emitter. In some examples, the radiation source may be an image projector such as a Digital Light Processing (DLP) projector which may also have an internal optical assembly in addition to being the source of radiation. If the light emitting element comprises a laser emitter or comprises a DLP or other type of projector, a masking component such as LCD may not be required since the image of the desired layer pattern can be projected directly onto the resin without the need for masking. If the 3D printer comprises a scanning laser the laser will be scanning the window while being switched on and off to produce an image. Fig. 1 shows an example of a printer configuration where the resin is in a shallow container which is illuminated from below. Alternative examples of 3D printers may comprise a deep tank full of resin which is illuminated from the top. In such examples, after each exposure the carrier platform moves downwards to form the object.

The light emitting element 520 may also comprise an optical assembly (not shown), which may have one or multiple lenses and mirrors, collimators, or any combination of these, via which patterned radiation from the light emitting element 520 and the light modulating element 522 may travel in a beam path through the window 521 to trace a layer of the object 20 in the 3D printable material 511. The method comprises printing the matrix assembly of interconnected lenses 20 by printing a stack of layers 223 having a stacking direction extending in parallel to the first direction 11 (at an angle of up to ± 10°) such that successive layers 223 of 3D printed material are oriented in the second direction 12.

The matrix assembly of interconnected lenses 20 comprises a plurality of lenses 22 arranged in a matrix extending in a first direction 11 and a second direction 12 (11,12 plane), thus having multiple rows and columns. The plane defined by first and second direction 11,12 may be substantially perpendicular to the plane define by second and third direction 12,13 (i.e. the optical axis of each lens of the plurality of lenses extending in a third direction 13). The method comprises printing the matrix assembly of interconnected lenses 20 by printing a stack of layers 223 having a stacking direction extending in parallel to the plane defined by the first and second direction (11,12 plane). The LCD may be placed so that the edges of pixels are aligned along the second direction 12 and the third direction 13. The orientation of the lens plate plane is chosen so that it is perpendicular to the plane defined by the second direction 12and the third direction 13, such that successive layers of 3D printed material 223 are oriented in the second direction 12 (and third direction 13). Each layer of 3D printed material 223 is thus arranged such that it is in a plane defined by the second direction 12 and the third direction 13. The lens assembly 20 is thus printed standing up on one of its sides instead of being printed resting flat on the carrier platform 530. The matrix assembly of interconnected lenses 20 is thus printed while being oriented in a vertical direction and may preferably be printed with a tilt angle of less than 20°, less than 10°, such as less than 6°. The 3D printed matrix assembly of interconnected lenses 20 comprises a plurality of subassemblies of interconnected lenses 21, each comprising a subset of the plurality of lenses 22 interconnected in the first direction 11, i.e. in a direction perpendicular to the plane defined by 12,13-plane. This direction is oriented in the direction perpendicular to the surface of the carrier platform 530, thus creating vertically oriented subassemblies of interconnected lenses 21. The plane of the lens plate may be oriented in the 11,12-plane or in 11,13-plane.

The method may further comprise the subsequent steps of mounting the carrier platform 530 to a rotor (not shown), rotating said rotor about an axis perpendicular to the carrier platform 530 while the matrix assembly of interconnected lenses 20 remains connected to the carrier platform 530. Subsequently or simultaneously, the matrix assembly of interconnected lenses 20 may be exposed to light comprising the curing wavelength. The finished lens assembly 20 may then be removed from the carrier platform 530. The matrix assembly 20 may also be separated from the carrier platform 530 before spinning and may be place onto another platform connected to the rotor so that the plane of the matrix assembly 20 is parallel to the rotation axis.

The method may further comprise applying an additional coating 224 (shown in Fig. 5) covering at least part of a surface of the 3D printed matrix assembly of interconnected lenses 20 before performing the spinning process described above. A coating 224 may be applied to the lens assembly as a whole, for example by immersing the 3D printed lens assembly 20 in a second material such that a layer of second material covers the surface of the lens assembly 20. The second material may be a material suitable for photopolymerization at a curing wavelength but may also be polymerizable by other means. The second material may be the same material as the 3D printable material used to print the matrix assembly of interconnected lenses, or it may be a different material. Alternatively or additionally, a coating 224 may be applied only to parts of the lens assembly 20, such as for example to one or more lenses 22 of the plurality of lenses 22. In this way, the printing lines created by the stack of layers 223 on the lens 22 may be smoothed out by adding small amount extra resin to the surfaces the lens 22.

Materials with (methyl)acrylate groups may be most suitable as 3D printable material (polymerisable resin material). They may be used in combination with Phosphinoxides and Phosphinatesas photo initiator molecules.

Experiments were successfully performed using the method as described herein and using 3D printable material comprising an acrylate mixture comprising hexanediol di methacrylate mixture (such as Diacryl Sartomer 540) and initially comprising a photo initiator (such as photoinitiator Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, TPO which can be initiated at 405nm radiation).

Fig. 2 schematically shows a lighting device 1 comprising a matrix lighting panel 100 comprising a plurality of light sources 110 arranged in a matrix configuration on a carrier 120 and a 3D printed matrix assembly of interconnected lenses 20 comprising a crosslinked polymer, the matrix assembly of interconnected lenses being mounted over the matrix lighting panel 100. In the following, the invention will be described in terms of a lighting device 1 comprising the matrix assembly of interconnected lenses 20. All aspects described the lighting device 1 and the matrix assembly of interconnected lenses 20 is equally applicable to the method of manufacturing the matrix assembly of interconnected lenses 20.

In this example, the matrix lighting panel 100 as well as the matrix assembly of interconnected lenses 20 comprise a 4x4 matrix having four columns extending in a first direction 11 and four rows extending in a second direction 12. Each of the plurality of lenses 22 thus corresponds to one of the plurality of light sources (i.e. LEDs) 110 comprised by the matrix lighting panel 100.

The 3D printed matrix assembly of interconnected lenses 20 comprises a plurality of subassemblies of interconnected lenses 21, each comprising a subset of the plurality of lenses 22 interconnected in the first direction 11. The subset of the plurality of lenses 22 may be interconnected by one or more first direction interconnects 214 interconnecting adjacent lenses 22 of the subset of the plurality of lenses 22 in the first direction 11.

At least one subassembly of interconnected lenses 21 may comprise mounting means 215 for securely mounting the matrix lighting assembly of interconnected lenses 20 over the matrix lighting panel 100. The mounting means 215 may be comprised by the interconnects 214. The mounting means 215 may be designed in any suitable form and the number of mounting means 215 required may strongly depend on the design of the lighting device 1 and the design of the lens assembly 20. In the example shown in Fig.2, the mounting means 215 are circular holes integrated into several of the subassemblies 21 at different positions within the respective subassembly 21. Some subassemblies 21 may comprise one or more mounting means 215 while other (adjacent) subassemblies 21 may not comprise any mounting means 215.

Fig. 3 schematically depicts an example of a matrix assembly of interconnected lenses 20. The 3D printed matrix assembly of interconnected lenses 20 comprises a plurality of subassemblies of interconnected lenses 21, each comprising a subset of the plurality of lenses 22 interconnected in the first direction 11. The plurality of subassemblies of interconnected lenses 21 are interconnected in the second direction 12 in at least one position. This second direction interconnection 216 may preferably be located such that the proximate ends 212 of the subassemblies 21 are interconnected, or such that the distal ends 213 of the subassemblies are interconnected. In the example of Fig. 3 A both the proximate ends 212 and the distal ends 213 are respectively interconnected in the second direction 12. The vertically oriented subassemblies of interconnected lenses21 may thus be connected together with horizontal bars 216 at the bottom 213 and/or at the top 212. A second direction interconnect 216 at the proximate end 212 and/or the distal end 213 may be beneficial during the manufacturing process using 3D printing. The interconnect 216 may serve as a connection of the matrix assembly of interconnected lenses 20 to the carrier platform of the 3D printer, ensuring a good adhesion of the object during the printing process. The second direction interconnect 216 may be bar-shaped having a width W2 which may be smaller than 15 mm, smaller than 10 mm, such as in the range of 2 mm < W2

< 5 mm. The second direction interconnect 216 may additionally comprise means for slightly adjusting its length. The length of the second direction interconnect 216 may be adjusted for aligning with the light emitting elements and/or for aligning the mounting means with the mating mounting structures on the matrix lighting panel. To this end the second direction interconnect 216 may for example comprise one or more gaps, or one or more structures which are extensible and/or contractable in the second direction 12.

The subset of the plurality of lenses 22 may be interconnected by one or more first direction interconnects 214 interconnecting adjacent lenses 22 of the subset of the plurality of lenses 22 in the first direction 11. These may be bar-shaped interconnects 214 having a width W1 measured in the second direction 12 which may be in the range of 1 mm

< W1 < 5 mm. The interconnects 214 may have a surface having an increased surface roughness, such as a surface roughness which is larger than 5-30 micrometers. Additionally or alternatively, the interconnects 214 may comprise geometrical open structures comprising repeating units having open cell structures (not shown). Such open cell structures may be repeating units having a geometrical grid pattern.

The 3D printed matrix assembly of interconnected lenses 20 comprises one or more open spaces 23 located in between the plurality of subassemblies of interconnected lenses 21. The surface area 231 of the one or more open spaces 23 is at least 30%, such as 40%, preferably at least 50% of the total surface area 201 of the 3D printed matrix assembly of interconnected lenses 20. The surface area 231 of the one or more open spaces 23 is measured based on the perimeter of the one or more open spaces 23. The total surface area 201 of the 3D printed matrix assembly of interconnected lenses 20 is measured based on its outer perimeter.

In an example, the one or more open spaces 23 may extend to at least 90% of the surface area 201 of the 3D printed matrix assembly of interconnected lenses 20 not being covered by the plurality of subassemblies of interconnected lenses 21. In other words, on the matrix assembly of interconnected lenses 20, the areas around the plurality of lenses 22 is removed (almost) completely, so that only the lenses 22 having an optical lens function are present with minimal connection between them (such as in the form of the bar-shaped interconnects 214).

In an example, each lens 22 of the plurality of lenses 22 may have a substantially elliptical shape so that every lens has a major axis describing the broadest direction, and a minor axis describing the narrower direction. The major axis of the ellipse may be oriented in the first direction 11. Hence, the broadest direction of the lens 22 may be oriented in the direction perpendicular to the surface of build platform 530.

Fig. 3B shows the cross-section of the matrix assembly of interconnected lenses 20 as indicated with A- A in Fig. 3 A. Each of the plurality of lenses 22 comprises a light input surface 221 and a light output surface 222. The light output surface 222 is at least partly convex, and the light input surface 221 is at least partly concave. Fig. 3B shows that the matrix assembly of interconnected lenses 20 comprises a plurality of lenses 22 which are shaped on both the light input surface 221 and the light output surface 222.

Figs. 4A to 4E show examples of matrix assemblies of interconnected lenses 20 comprising different interconnections 214,216 in the first direction 11 and the second direction 12. Fig. 4A and Fig. 4B show examples of different interconnections 216 in the second direction. The plurality of subassemblies of interconnected lenses 21 are interconnected in the second direction 12 in at least one position. As described above, this position may be the proximate ends or the distal ends of the subassemblies of interconnected lenses 21. However, the interconnection 216 in the second direction 12 may be located at any position in between the proximal ends or distal ends. In the example shown in Fig. 4A, the subassemblies of interconnected lenses 21 are interconnected in the second direction 21 by an interconnect 216 in the middle of the lens assembly 20. While the lens assembly shown in this example may have additional manufacturing challenges, it may provide additional flexibility of the lens assembly and may still be mounted to the matrix lighting panel in one single assembly step.

Fig. 4B shows an example of a lens assembly in which the subassemblies of interconnected lenses 21 are interconnected in the second direction 12 in more than one position. The subassemblies of interconnected lenses 21 may be interconnected in the second direction 12 in additional locations. In this example, one or more of the plurality of lenses 22 in each subassembly of interconnected lenses 21 is connected to one of the plurality of lenses 22 in an adjacent subassembly of interconnected lenses 21. A lens assembly 22 according to this example may provide additional stability and durability.

It should be noted that these are mere examples of different aspects of interconnecting the subassemblies of interconnected lenses 21 in the second direction 12, and that the skilled person is able to design alternatives without departing from the scope of the appended claims.

Fig. 4C shows an example in which the subset of lenses of the subassemblies of interconnected lenses 21 are each arranged in a zig zag pattern, such that different rows or columns of the matrix assembly of interconnected lenses 20 is staggered with respect to each other.

Fig. 4D shows an example in which the interconnects 214 and the second direction 216 are printed in a zig zag pattern. Such a configuration of the matrix assembly 20 may show a certain amount of flexibility so as to be stretched or compressed in the first direction 11 and/or the second direction 12.

Fig. 4E shows an example in which the subset of lenses in a subassembly 21 is interconnected by interconnects 214 having a diamond or rhombus shape.

Fig. 5 schematically shows a cross section of a single lens 22 as may be comprised by the matrix assembly of interconnected lenses 20. As described above, each lens 22 of the plurality of lenses 22 comprises a stack of layers 223 having a stacking direction extending in parallel to the first direction 11. The stack of layers 223 may be created using 3D printing. The stack of layers 223 may aid in the optical performance of the lens 22 by improving the light distribution.

The example shown in Fig. 5 shows a 3D printed matrix assembly of interconnected lenses 20 comprises a coating 224 covering at least part of a surface of the 3D printed matrix assembly of interconnected lenses 20. The stack of layers 223 as such may be beneficial for the light distribution but the fine printing lines on the light input surface 221 and/or the light output surface 222 of the lens 22 may not be desired. These fine printing lines may be smoothed by adding a coating to those surfaces of the lens 22. This may be achieved by adding extra resin to the surfaces of the lens 22 after the 3D printing process has been completed. A coating 224 may also be applied to the lens assembly as a whole, for example by immersing the 3D printed lens assembly 20 in a second material such that a layer of second material covers the surface of the lens assembly 20. The second material may be a material suitable for photopolymerization at a curing wavelength but may also be polymerizable by other means. The second material may be the same material as the 3D printable material used to print the matrix assembly of interconnected lenses, or it may be a different material.

Figs. 6 A and 6B schematically depicts a single lens 22 of the plurality of lenses 22, wherein Fig. 6B shows the cross-section A of the lens depicted in Fig. 6A. Each of the plurality of lenses 22 may comprise an optically active area 225 and an optically inactive area 226 together forming a total area of each of the plurality of lenses 22. The optically inactive area 226 may form less than 40% of the total area of each of the plurality of lenses. The optically active area 225 contributes to the lensing function of the lens, whereas the optically inactive area 226 is not designed to contribute to the optical function of the lens. The optically inactive area 226 is for example required for mechanical or stability reasons or for reasons inherent to the production method of the matrix assembly of interconnected lenses 20.

The optically active area 225 of the lens may be at least partially surrounded by the optically inactive area 226. In a conventional, solid lens plate these optically inactive areas fill up the complete space in between the lenses. In the lens assembly 20 described above, the optically inactive areas 226 around the optically active area 225 may be minimized and made to follow the contours of the optically active areas 225 of the lenses 22.

Figs. 7A to 7C show different schematic examples of lenses having an optically active area 225 surrounded by an optically inactive area 226. The optically inactive areas 226 may comprise round edges as shown in Fig. 7A or straight edges and comers as shown in Fig. 7B and 7C. The optically inactive areas 226 may form preferably less than 40%, more preferably less than 30%, and most preferably less than 20% of the total area of the plurality of lenses 22.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined.

Claims

CLAIMS:

1. A method for manufacturing a matrix assembly of interconnected lenses (20) comprising a plurality of lenses (22) arranged in a first direction (11) and a second direction (12) perpendicular to the first direction (11), by means of 3D printing using a 3D printer (500), wherein the matrix assembly of interconnected lenses (20) comprises a plurality of subassemblies of interconnected lenses (21), each subassembly of interconnected lenses (21) comprising a subset of the plurality of lenses (22) interconnected in the first direction (11), the plurality of subassemblies of interconnected lenses (21) being interconnected in the second direction (12) in at least one position, wherein each lens of the plurality of lenses (22) comprises a light input surface (221) and a light output surface (222), wherein the light output surface is at least partly convex, and the light input surface is at least partly concave, wherein the matrix assembly of interconnected lenses (20) comprises one or more open spaces (23), each open space (23) being located in between two subassemblies of interconnected lenses (21) of the plurality of subassemblies of interconnected lenses (21), a surface area (231) of the one or more open spaces (23) being at least 30% of a surface area (201) of the matrix assembly of interconnected lenses (20), and wherein the 3D printer (500) comprises: a vessel (510) for holding a 3D printable material (511) being polymerizable at a curing wavelength, a light emitting element (520) and a light modulating element (522) for exposing the 3D printable material (511) to patterned light comprising the curing wavelength, and a carrier platform (530) using an elevator mechanism (540) to advance a distance between the carrier platform (530) and the light emitting element (520) to form successive layers of 3D printed material (223) by exposing each layer of 3D printable material (511) to the patterned light, the method comprising printing the matrix assembly of interconnected lenses (20) by printing a stack of layers (223) having a stacking direction extending in parallel to the first direction (11) such that successive layers (223) of 3D printed material are oriented in the second direction (12).

2. The method according to claim 1, wherein the 3D printable material (511) comprises a material having an acrylate group and a photo initiator activated by the curing wavelength selected from a range of 100 nm - 450 nm.

3. The method according to any one of the preceding claims, wherein each layer (233) of the stack of layers (223) has a layer height being in the range of 10 - 100 micrometers.

4. The method according to any one of the preceding claims, wherein a surface of the matrix assembly of interconnected lenses (20) comprises an excess 3D printable material (511), and wherein the method subsequently further comprises one or more of: removing at least part of the excess 3D printable material (511), distributing at least part of the excess 3D printable material (511) across the surface of the matrix assembly of interconnected lenses (20), and exposing the matrix assembly of interconnected lenses (20) to light comprising the curing wavelength.

5. A lighting device (1) comprising: a matrix lighting panel (100) comprising a plurality of light sources (110) arranged in a matrix configuration on a carrier (120); and a 3D printed matrix assembly of interconnected lenses (20) comprising a crosslinked polymer, the matrix assembly of interconnected lenses being mounted over the matrix lighting panel (100); wherein the 3D printed matrix assembly of interconnected lenses (20) comprises a plurality of lenses (22) distributed in a first direction (11) and in a second direction (12), the 3D printed matrix assembly of interconnected lenses (20) comprising a plurality of subassemblies of interconnected lenses (21), each subassembly of interconnected lenses (21) comprising a subset of the plurality of lenses (22) interconnected in the first direction (11), wherein the plurality of subassemblies of interconnected lenses (21) are interconnected in the second direction (12) in at least one position, wherein each of the plurality of lenses (22) comprises a light input surface (221) and a light output surface (222), the light output surface (222) being at least partly convex, and the light input surface (221) being at least partly concave, wherein the 3D printed matrix assembly of interconnected lenses (20) comprises one or more open spaces (23) located in between the plurality of subassemblies of interconnected lenses (21), and wherein a surface area (231) of the one or more open spaces (23) is at least 30% of a surface area (201) of the 3D printed matrix assembly of interconnected lenses (20).

6. The lighting device (1) according to claim 5, wherein each of the plurality of lenses (22) corresponds to one of the plurality of light sources (110) comprised by the matrix lighting panel (100).

7. The lighting device (1) according to any one of claims 5-6, wherein each subassembly of interconnected lenses (21) comprises one or more interconnects (214) interconnecting adjacent lenses (22) of the subset of the plurality of lenses (22), and wherein the one or more interconnects (214) have a bar shape having a width W1 measured in the second direction (12) which is in the range of 1 mm < W1 < 5 mm.

8. The lighting device (1) according to claim 7, wherein the interconnects (214) have a surface having a surface roughness which is larger than 5 micrometers, and/or wherein the interconnects (214) comprise geometrical open structures.

9. The lighting device (1) according to any one the preceding claims, wherein at least one subassembly of interconnected lenses (21) comprises mounting means (215) for mounting the matrix lighting assembly of interconnected lenses (20) over the matrix lighting panel (100).

10. The lighting device (1) according to any one of the preceding claims, wherein each of the plurality of lenses (22) comprises an optically active area (225) and an optically inactive area (226) together forming a total area of each of the plurality of lenses, and wherein the optically inactive area (226) forms less than 40% of the total area of each of the plurality of lenses (22).

11. The lighting device (1) according to any one of the preceding claims, wherein the one or more open spaces (23) extend to at least 90% of the surface area (201) of the 3D printed matrix assembly of interconnected lenses (20) not being covered by the plurality of subassemblies of interconnected lenses (21).

12. The lighting device (1) according to any one of the preceding claims, wherein each lens (22) of the plurality of lenses (22) has a substantially elliptical shape, and wherein the major axis of the ellipse is oriented in the first direction (11).

13. The lighting device (1) according to any one of the preceding claims, wherein each lens (22) of the plurality of lenses (22) is a peanut-shaped lens.

14. The lighting device (1) according to any one of the preceding claims, wherein each lens (22) of the plurality of lenses (22) comprises a stack of layers (223) having a stacking direction extending in parallel to the first direction (11), and wherein the stack of layers (223) is created using 3D printing.

15. The lighting device (1) according to any one of the preceding claims, wherein the 3D printed matrix assembly of interconnected lenses (20) comprises a coating (224) covering at least part of a surface of the 3D printed matrix assembly of interconnected lenses (20).