Manufacturing an optical element

Abstract

A method of manufacturing an optical element, the method comprising: providing a substrate; providing a tool comprising a section defining a surface structure of the optical element on a first side; aligning the tool and the substrate relative to each other and bringing the first sides of the tool and the substrate together with material between the tool and the substrate; positioning a transparent mask structure adjacent to the substrate to which the material has adhered, the mask structure comprising a mask layer; emitting light through the mask structure to impinge on a portion of the material to cure said portion of the material, wherein the mask layer prevents light from impinging on a remaining portion of the material such that the remaining portion of the material is not cured; and removing the uncured remaining portion of the material.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to manufacturing optical elements. BACKGROUND

[0002] Small optoelectronic modules, such as imaging devices and light projectors, employ lenses or other optical elements to achieve desired optical performance. Optical elements include transparent diffractive and / or refractive optical elements for affecting a light beam. Optical elements can be produced by replication. In some applications, replicating an optical element includes forming a portion of a liquid material, such as an epoxy, into a desired shape using, for example, a portion of a tool, and subsequently curing the material. In some cases, the replicated optical element is formed together with a courtyard formed in the vicinity of the replicated optical element. The courtyard contains material that is included beyond that which is required to form the optical element, with excess material included to ensure full coverage of the portion of the tool. SUMMARY

[0003] The present disclosure relates to manufacturing optical elements without a courtyard.

[0004] According to an aspect of the present disclosure, there is provided a method of manufacturing an optical element, the method comprising: providing a substrate; providing a tool comprising a section defining a surface structure of the optical element on a first side; aligning the tool and the substrate relative to each other and bringing the first sides of the tool and the substrate together with a material between the tool and the substrate; positioning a transparent mask structure adjacent to the substrate to which the material has adhered, the mask structure comprising a mask layer; emitting light through the mask structure to be incident on a portion of the material to cure said portion of the material, wherein the mask layer prevents light from being incident on a remaining portion of the material such that the remaining portion of the material is uncured; and removing the uncured remaining portion of the material.

[0005] Embodiments of the present disclosure advantageously enable a higher density of optical elements to be manufactured on a single substrate, which would otherwise be limited by the area of the courtyard on the substrate. This results in a more efficient manufacturing process, as the number of optical elements that can be manufactured at any one time is increased.

[0006] Furthermore, the manufacturing process can be greatly simplified, as the courtyard does not need to be removed prior to installing the optical element in a module.

[0007] As removal of the courtyard is not required, optical elements manufactured according to embodiments of the disclosure without a courtyard can exhibit improved reliability over optical elements with a courtyard, for which removal of the courtyard (e.g. using a laser cutter or by mechanically cutting or detaching the courtyard from the optical element) can result in the optical element being left with a rough edge and / or unintended portions of the courtyard being left attached, and / or portions of the optical element being inadvertently removed. Such improved reliability is advantageous as the optical performance of small optical elements is highly sensitive to changes in size and / or shape. The improved reliability is also advantageous in cases where the application of the small optical element requires high precision positioning, for example in a small optoelectronic module.

[0008] Furthermore, optical elements without a courtyard can further exhibit improved optical performance over optical elements with a courtyard as, during use, unwanted light that would otherwise be collected by the courtyard (or any remaining portions of the courtyard in cases where the courtyard has been removed) is not collected, and / or light collected by the optical element will not be redirected along unintended paths, for example due to transmission, reflection and / or refraction at the interface between the courtyard (or courtyard portions) and air and / or the interface between the optical element and the courtyard (or courtyard portions).

[0009] Providing a transparent mask structure adjacent to a substrate to which material is adhered is advantageous as the transparent mask structure can be reused with several different substrates and / or tools, thereby providing a simplified and more efficient manufacturing process.

[0010] In some embodiments, the mask structure is positioned below the substrate such that the light is incident on a second side of the substrate opposite the first side before being incident on the portion of the material. Such an arrangement can be advantageous as the light only passes through the thin mask structure and the substrate, thereby minimising the risk of inadvertently curing remaining portions of the material due to divergence and / or scattering of the light. Alternatively, the tool is made of a transparent material and the mask structure is positioned above the tool such that the light passes through the tool before being incident on the portion of the material.

[0011] In some embodiments, removing the uncured remaining portion of material comprises washing away the uncured remaining portion of material with a solvent. Alternatively or additionally, removing the uncured remaining portion of material can comprise extracting the uncured remaining portion of material via one or more channels. Extracting the uncured remaining portion can be advantageous as it can further increase the density of the replicated optical element as additional tool volume or substrate area is not required for the remaining portion. In some embodiments, the tool comprises one or more channels. In some embodiments, the tool comprises a first portion made of a first material and a second portion made of a second material, and the one or more channels extend through both the first portion and the second portion. Alternatively, the one or more channels can extend through the second portion and extend along the interface between the first portion and the second portion of the tool. In other embodiments, the substrate comprises one or more channels.

[0012] In some embodiments, the mask layer is made of metal.

[0013] In some embodiments, the light is collimated light. This can be advantageous as it further minimises the risk of unintentionally curing a remaining portion of material, which can occur if the light is not collimated.

[0014] In some embodiments, the light is ultraviolet light.

[0015] In some embodiments, the transparent mask structure is made of glass. BRIEF DESCRIPTION OF DRAWINGS

[0016] Some embodiments of the disclosure will now be described, by way of example only, and with reference to the accompanying drawings in which:

[0017] Figure 1 a and 1b a known replication process for manufacturing optical elements is shown;

[0018] Figure 2 a process for manufacturing optical elements according to the disclosure is shown;

[0019] Figures 3a to 3c various examples of a process for manufacturing optical elements according to the disclosure are shown;

[0020] Figures 4a to 4c various examples of a process for manufacturing optical elements according to the disclosure are shown, wherein uncured material is removed via one or more channels; and

[0021] Figure 5a and 5b a comparison between an optical element produced by a known replication process and an optical element produced by a process for manufacturing optical elements according to the disclosure is shown. DETAILED DESCRIPTION

[0022] Embodiments will now be described, by way of example only, with reference to the accompanying drawings.

[0023] Figure 1 a and 1b A known replication process for manufacturing optical elements is shown.

[0024] In Figure 1 a , steps 1 to 9 of the replication process are shown. In step 1 a metal pin is shown, having a portion shaped to correspond to an optical element (in this case a lens) and a courtyard.

[0025] In Figure 1 a steps 2 and 3, the metal pin is employed in the formation of a reco-tool. The reco-tool comprises a replication surface comprising a (negative) copy of the metal pin surface.

[0026] In Figure 1 a steps 4 and 5, a reco-process is performed. Material (e.g. epoxy resin) is applied to the reco-tool and / or a substrate. The reco-tool is subsequently brought into contact with the substrate, and the material fills the portion of the reco-tool corresponding to the optical element shaping. Excess material fills at least some of the portion of the tool corresponding to the courtyard shaping. The material is then cured and the reco-tool is removed. The cured material on the substrate provides a master. The reco-process can be repeated across the substrate, such that the master comprises a plurality of identical optical elements each having an associated courtyard. Alternatively, the master can comprise a single optical element having a courtyard.

[0027] The master is subsequently employed in the formation of a tool (steps 6 and 7 of Figure 1 a ) by a process similar to that in which the metal pin is employed in the formation of a reco-tool. The tool comprises a replication surface comprising a (negative) copy of the master surface.

[0028] Figure 1 a Steps 8 and 9 of show the replication process. Material (e.g. epoxy resin) is applied to the tool and / or a substrate, and the tool is subsequently brought into contact with the substrate. The material fills one or more portions of the tool corresponding to the optical element shaping. Excess material fills at least some of the one or more portions of the tool corresponding to the courtyard shaping. The material is subsequently cured and the tool is removed. Left is a replica comprising one or more optical elements having a courtyard on a substrate.

[0029] In the present disclosure, the terms“optical element” and“courtyard” can describe features of a master or a replica, and the methods described herein are applicable to both recombination and replication processes. Thus, as used herein, the terms“replication” and“replication process” can describe the formation of a master in a recombination process, or equivalently the formation of a replica in a replication process. Tools referred to herein can be replication tools or recombination tools.

[0030] Figure 1 b A known replication process for manufacturing optical elements is shown in more detail, showing a cross-section through a tool 102 and a substrate 106. The preferred material for the tool 102 is polydimethylsiloxane (PDMS), but other materials can also be used. The tool 102 comprises a replication surface comprising one or more replication segments, the surface of each replication segment being a (negative) copy of the surface shape of the optical element to be manufactured. The replication segments can be convex and thus define a concave optical element surface, or concave and define a convex optical element surface.

[0031] The substrate 106 has a first upper side and a second lower side, and can be of any suitable material, for example glass. Figure 1 b An optical element 110 is shown being formed extending from the first upper side of the substrate 106. As Figure 1 b shown, the substrate 106 has an optical element 108 extending from the second lower side of the substrate 106.

[0032] To replicate the replication surface of the tool 102, replication material 104 (for example, epoxy) is applied to the substrate 106, or to the tool 102, or to both the tool 102 and the substrate 106.

[0033] After the replication material 104 is applied, the substrate 106 and the tool 102 are aligned relative to each other. After alignment, the substrate 106 and the tool 102 are brought together. Once the replication material 104 has hardened, the tool 102 is removed.

[0034] During replication, when the tool 102 and the substrate 106 (for example, glass) are in contact, the excess material or epoxy applied during the shot typically spills over the area of interest and forms a courtyard 112. The courtyard 112 is typically a circular shape. This circular courtyard 112 does not perform any optical function, it is created by the epoxy 104 added during the replication process being more than what is needed for each structure, resulting in spillage. The additional epoxy 104 ensures that the full volume of replication material needed for a particular structure is available (as the tolerance on epoxy volume is not zero), and the additional fluid collects to form the courtyard 112. As Figure 1 b shown, the courtyard 112 has an epoxy meniscus 114. Typically, the courtyard 112 has a height h yand a width w of 200-400μm y .

[0035] The courtyard 112 results in a reduced density of optical elements 108 that can be fabricated on a single substrate 106. Since the courtyard 112 comprises the same material 104 as the optical element 108, it can also cause unwanted light to be collected when the optical element 108 is in use (e.g., as a component in an optoelectronic module). Alternatively or additionally, the courtyard 112 can cause light to follow an unintended path due to reflection, transmission, refraction, or any other light interaction process, for example, at the interface between the courtyard and its surrounding environment (e.g., air) and / or at the interface between the courtyard and the optical element.

[0036] Now for reference Figure 2 Figures 3 and 4 illustrate a process 200 for manufacturing an optical element according to an embodiment of the present disclosure.

[0037] The optical elements mentioned in this article may be lenses. It should be understood that this is merely an example, and optical elements may be any element that affects the light illuminating it, including but not limited to lenses, collimators, pattern generators, deflectors, mirrors, beam splitters, diffraction prisms, diffusers, microlens arrays, elements for decomposing radiation into its spectral components, and combinations thereof.

[0038] like Figure 2 As shown, as an initial step S202, a substrate 302 is provided.

[0039] In the second step S204, tools 315 and 335 are provided, each tool 315 and 335 including a segment on a first side that defines the surface structure of the optical element 304. However, the segment of the tool may have a circular shape, which is merely an example, and embodiments are extended to other shaped optical elements (e.g., some lenses are square).

[0040] In the third step S206, tools 315, 335 and a first side of substrate 302 are placed together, with material (e.g., epoxy resin) between tools 315, 335 and substrate 302. Material can be applied to substrate 302 or tools, or both. When material is applied to the tools, it is transferred to the first side of substrate 302 when the tools and substrate 302 are placed together. Epoxy resin, acrylate, ormocer materials, photoresist, and mixed materials are examples of materials that can be used in embodiments of this disclosure to form optical elements.

[0041] In the fourth step S208, the transparent mask structure 318 is positioned adjacent to the substrate 302.

[0042] In the fifth step S210, light 314 is emitted through the mask structure 318 to strike the portion 304 of the material to solidify that portion of the material.

[0043] In the sixth step S212, the uncured remaining portion 306 of the material is removed.

[0044] Now, referring to Figures 3 and 4, a more detailed description will be given. Figure 2 Steps S202 to S212.

[0045] Figure 3a Example 300a of process 200 is illustrated schematically. Figure 3a A cross-section is shown through the substrate 302 and tool 315 provided in steps S202 and S204 of process 200. The substrate can be any suitable material, such as glass. The preferred material for tool 315 is polydimethylsiloxane (PDMS), but other materials may also be used. In addition to the softer material portion 330 (e.g., PDMS), tool 315 may be provided with a rigid backing plate 320, whereby the softer material portion 330 will contact the material forming the optical element. Tool 315 has sections defining the (negative) surface structure of the optical element. For example, in the case where the optical element to be manufactured has a concave surface profile, the section of tool 315 has a convex profile. In another example, in the case where the optical element to be manufactured has a convex surface profile, the section of tool 315 has a concave profile.

[0046] The tool 315 is then brought into contact with the first side of the substrate 302, with material between the tool 315 and the substrate 302 (step S206 of process 200). Material can be applied, for example, to the first side of the substrate 302, the tool 315, or both. In example 300a, material can be specifically applied to the softer material portion 330 of the tool 315. Material can be applied immediately before the tool 315 and the first side of the substrate 302 are placed together. Material can be applied, for example, by ejecting or spraying one or more drops, using a dispensing tool that can operate, for example, in a manner similar to an inkjet printer. Alternatively or additionally, material can be applied between the tool 315 and the first side of the substrate 302 after the tool 315 and the first side of the substrate 302 have been placed together. In the case where material is applied after the tool 315 and the first side of the substrate 302 have been placed together, material can be supplied (e.g., by injection) into the gap formed between the tool 315 and the first side of the substrate 302. The material can be epoxy resin or any suitable curable material.

[0047] When the tool 315 and the first side of the substrate 302 are brought together, material is between the tool 315 and the first side of the substrate 302. A portion 304 of the material fills a segment of the tool 315 that defines the (negative) surface structure of the optical element. A remaining excess portion 306 of the material is squeezed out of this segment of the tool.

[0048] The transparent mask structure 318 is then positioned adjacent to the substrate (step S208 of process 200). The mask structure 318 comprises a suitably transparent material (e.g. glass) through which light can pass, on which a mask layer 313 is provided. The mask layer can be made of a metal (e.g. chromium), black ink or paint, or any other suitable non-transparent material. In Figure 3a In the illustrated example 300a, the mask structure 318 is positioned below the substrate 302. In another example 300b, as Figure 3b illustrated, the mask structure 318 is positioned above the tool 315. The light source is positioned such that the emitted light 314 then impinges on the mask structure 318 (step S210 of process 200). The light 314 has a wavelength that is capable of curing the optical element material and is capable of being transmitted by the mask structure 318 and is capable of being absorbed, reflected and / or otherwise blocked by the mask layer 313. For example, the light 314 can be ultraviolet (UV) light. Embodiments are not limited to the light 314 being UV light, and other light having other wavelengths can be used. For example, visible light curing is also possible. When using visible light, the same materials (to be cured) can be used as with UV light, but a different photo-initiator is used.

[0049] In this disclosure, the term “transparent” describes a material that transmits the light 314, and the term “non-transparent” describes a material that does not transmit the light 314.

[0050] The light 314 can be collimated. This can prevent the light 314 from diverging after being transmitted by the mask structure, which otherwise can cause unintended portions or all of the non-cured portion 306 of the material to cure.

[0051] In the case where the mask structure 318 is positioned below the substrate 302, as Figure 3a illustrated, the substrate 302 comprises a transparent material, and the light 314 is transmitted by the substrate 302. In the case where the mask structure 318 is positioned above the tool 315, as Figure 3b illustrated, both the rigid backplate 320 and the softer material portion 330 of the tool 315 comprise a transparent material, and the light 314 is transmitted by the rigid backplate 320 and the softer material portion 330 of the tool 315.

[0052] Transmitted light 314 is incident on a portion 304 of the material that fills a segment of the tool 315 that defines a (negative) surface structure of an optical element, and the portion 304 is subsequently cured by the light incident thereon. The mask layer 313 prevents light from reaching a remaining portion 306 of the material, and the remaining portion 306 is not cured by the light.

[0053] Another example 300c of the process 200 is shown in Figure 3c , in which an opaque tool 335 is provided in step S204. The opaque tool 335 can comprise a metal. The example 300c can correspond to a reconstitution process. In the example 300c, the mask structure 318 is positioned beneath the substrate 302, and the light 314 is transmitted through the mask structure 318 and the substrate 302.

[0054] The light 314 can be transmitted through the mask structure 318 (step S210 of the process 200) when the tool 315 is in contact with the substrate 302. Alternatively, the light 314 can be transmitted through the mask structure 318 (step S210 of the process 200) when the tool 315 is in an elevated position above the substrate 302 (not in contact with the substrate 302).

[0055] When the portion 304 of the material has been cured, the remaining uncured portion 306 of the material is removed (step S212 of the process 200).

[0056] The remaining uncured portion 306 of the material can be removed by, for example, washing the material away with a solvent. Alternatively or additionally, the remaining uncured portion 306 of the material can be removed via one or more channels 402, 404, 406.

[0057] An example of the process 200 is shown in Figures 4a to 4c , in which the remaining uncured portion 306 of the material is removed via one or more channels 402, 404, 406 in step S212.

[0058] Figure 4a An example 400a is shown in which one or more channels 402 extend upwardly through the tool 315. The channels in the example 400a extend through the soft material portion 330 and the rigid backing plate 320 of the tool 315. In alternative examples, the tool can comprise a single piece of material, such as the opaque tool 335 shown in Figure 3c , and the channels can extend through the entire thickness of the tool material. In the example 400a, the uncured portion 306 of the material is removed by being vertically upwardly through the channels 402. The removed uncured portion 306 of the material can be extracted from one or more channel openings of the tool 315.

[0059] Figure 4bAnother example 400b is shown in which one or more channels extend vertically upward through the soft material portion 330 of the tool 315 and along the interface between the soft material portion 330 and the rigid backplate 320. The uncured portion 306 of the material is removed by portions of the vertically upward extending through the soft material portion 330 of the tool 315 vertically upward through the channels 404 and subsequently horizontally through the channels 404 along the interface between the soft material portion 330 and the rigid backplate 320. The removed uncured portion 306 of the material can be extracted from the one or more channel openings of the tool 315.

[0060] In the examples 400a and 400b shown, the mask structure 318 is positioned below the substrate 302 and the light 314 is transmitted through the substrate 302, where the substrate 302 is transparent. This prevents the light 314 from otherwise impinging on the uncured material 306 in the channels 402, 404 and curing the material in the channels 402, 404. Any cured material in the channels 402, 404 would block the channels 402, 404 and make it impossible to extract the uncured portion 306 of the material. Figure 4a and Figure 4b In the examples 400a and 400b shown, the mask structure 318 is positioned below the substrate 302 and the light 314 is transmitted through the substrate 302, where the substrate 302 is transparent. This prevents the light 314 from otherwise impinging on the uncured material 306 in the channels 402, 404 and curing the material in the channels 402, 404. Any cured material in the channels 402, 404 would block the channels 402, 404 and make it impossible to extract the uncured portion 306 of the material.

[0061] Figure 4c An alternative example 400c is shown in which one or more channels 406 extend vertically downward through the substrate 302. The uncured portion 306 of the material is removed by vertically downward through the channels 406. The removed uncured portion 306 of the material can be extracted from the one or more channel openings of the substrate 302.

[0062] In the example 400c shown, the mask structure 318 is positioned above the tool 315 and the light 314 is transmitted by the tool 315, where the tool 315 is transparent (where the tool includes the rigid backplate 320 and the soft material portion 330, where the rigid backplate 320 and the soft material portion 330 are transparent). This prevents the light 314 from otherwise impinging on the uncured material 306 in the channels 406 and curing the material in the channels 406. Figure 4c The uncured portion 306 of the material can be removed through the channels 402, 404, 406 by suction (e.g., with a vacuum pump). Alternatively, the uncured portion 306 can be forced through the channels 402, 404, 406 by the action of bringing the tool 315 and the substrate 302 together.

[0063] The uncured portion 306 of the material can be removed through the channels 402, 404, 406 by suction (e.g., with a vacuum pump). Alternatively, the uncured portion 306 can be forced through the channels 402, 404, 406 by the action of bringing the tool 315 and the substrate 302 together.

[0064] Removal of the uncured portion 306 of material via one or more channels 402, 404, 406 can reduce or eliminate the need for any additional sections or volumes of the tool 315 into which excess material 306 would otherwise overflow from sections of the tool corresponding to the optical elements. Where the tool 315 includes multiple sections corresponding to multiple optical elements, this can enable a higher density of those sections on the tool 315, resulting in the production of more optical elements in a single replication process.

[0065] Figure 5a and Figure 5b A comparison between optical elements 504 produced by a prior art replication process and the process 200 described in the present disclosure is shown.

[0066] Figure 5a An arrangement 500 of optical elements 504 produced on a substrate after a prior art replication process is shown. As previously described, excess epoxy or other replication material that overflows sections of the tool corresponding to the optical elements 504 forms a courtyard 502. The minimum distance between the optical elements 504 on the substrate is defined by the width dl of the spacer or singulation region 506 through which the substrate is cut or otherwise separated when the optical elements 504 are singulated into individual components before they are installed in optoelectronic modules. In the presence of the courtyard 502, the minimum distance between the spacer or singulation region 506 and the optical elements 504 has the width d2 of the courtyard. As previously described, d2 is typically 200-400 pm. Thus, the optical elements 504 with the courtyard 502 are separated on the substrate by a total minimum distance d3, where d3 = dl + (2 x d2). Overflow of material forming the courtyard 502 is typically uncontrollable. Thus, in some cases, the courtyard 502 can extend into the spacer or singulation region 506. This can result in cutting through portions of the courtyard during the singulation process, resulting in unintended defects in the courtyard 502 and / or the optical elements 504, which can reduce the reliability of the optical elements 504.

[0067] Figure 5b An arrangement 550 of optical elements 504 produced on a substrate after a replication process according to the present disclosure is shown. Since there is no courtyard 502, the minimum distance between the optical elements 504 is defined only by the width dl of the spacer or singulation region 506. Thus, the arrangement 550 allows for an increased area density of the optical elements 504 on the substrate compared to the prior art arrangement 500. In addition, the formation of the optical elements 504 is controlled by the tool during the replication process. Thus, the risk of material extending into the spacer or singulation region 506 is minimized, such that the singulation process results in fewer defects being formed in the optical elements 504.

[0068] While the present disclosure has been described in terms of the preferred embodiments, it is to be understood that those skilled in the art will be able to alter and modify the preferred embodiments without departing from the scope of the claims. It is the claims, therefore, that define the scope of the protection to be given to the present disclosure. Each feature disclosed in this specification, unless otherwise indicated, can be incorporated in any embodiment of the application, alone or in combination with any other feature disclosed, in any appropriate embodiment of the application.

Claims

1. A method of manufacturing an optical element, characterized by, The method comprises: providing a substrate (302); providing a tool (315, 335) comprising a section defining a surface structure of the optical element on a first side; aligning the tool and the substrate relative to each other and bringing the first sides of the tool and the substrate together with material between the tool and the substrate; positioning a transparent mask structure (318) adjacent to the substrate to which the material has adhered, the mask structure comprising a mask layer (313); emitting light (314) through the mask structure to impinge on a portion (304) of the material to cure the portion of the material, wherein the mask layer prevents light from impinging on a remaining portion (306) of the material such that the remaining portion of the material is uncured; and removing the uncured remaining portion of the material; wherein the removing comprises extracting the uncured remaining portion of the material via one or more channels (402, 404, 406) extending in a vertical direction.

2. The method of claim 1, wherein, wherein the mask structure is positioned below the substrate such that the light impinges on the second side of the substrate opposite the first side before impinging on the portion (304) of the material.

3. The method of claim 1, wherein, wherein the tool is made of a transparent material and the mask structure is positioned above the tool such that the light passes through the tool before impinging on the portion (304) of the material.

4. The method of claim 1, wherein, wherein the tool comprises the one or more channels (402, 404).

5. The method of claim 4, wherein, wherein the tool comprises a first portion (320) made of a first material and a second portion (330) made of a second material, and the one or more channels (402) extend through both the first portion and the second portion.

6. The method of claim 5, wherein, wherein the tool comprises a first portion (320) made of a first material and a second portion (330) made of a second material, and the one or more channels (404) extend through the second portion and along an interface between the first portion and the second portion of the tool.

7. The method of claim 1, wherein, wherein the substrate comprises the one or more channels (406).

8. The method of claim 1, wherein, wherein the mask layer is made of a metal.

9. The method of claim 1, wherein, wherein the light is collimated light.

10. The method of claim 1, wherein, wherein the light is ultraviolet light.

11. The method of claim 1, wherein, wherein the transparent mask structure is made of glass.

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