Optical element and method of forming an optical element

Abstract

According to one aspect, an optical waveguide comprises a waveguide body exhibiting total internal reflection, a substrate, and a plurality of light extraction features disposed on a surface of the substrate. The light extraction features are non-adhesively bonded to the waveguide body or may be disposed on opposing sides of the substrate. A method of forming an optical element is also disclosed.

Description

REFERENCE REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

SEQUENTIAL LISTING

Not applicable

FIELD OF DISCLOSURE

The present subject matter relates to the manufacture of optical devices, and more particularly, to a method of forming an optical element.

BACKGROUND

An optical waveguide mixes and directs light emitted by one or more light sources, such as one or more light emitting diodes (LEDs). A typical optical waveguide includes three main components: one or more coupling surfaces or elements, one or more distribution elements, and one or more extraction elements. The coupling component(s) direct light into the distribution element(s), and condition the light to interact with the subsequent components. The one or more distribution elements control how light flows through the waveguide and such control is dependent on the waveguide geometry and material. The extraction element(s) determine how light is removed by controlling where and in what direction the light exits the waveguide.

When designing a coupling element, the primary considerations are: maximizing the efficiency of light transfer from the source into the waveguide; controlling the location of light injected into the waveguide; and controlling the angular distribution of the light in the waveguide. The coupling element of a waveguide may be comprised of one or more of a number of optical elements, including a primary source optic (such as the lens on an LED component package), one or more intermediate optical elements (such as a lens or array of lenses) interposed between the source(s) and the waveguide coupling surface or surfaces, one or more reflective or scattering surfaces surrounding the sources, and specific optical geometries formed in the waveguide coupling surfaces themselves. Proper design of the elements that comprise the coupling element can provide control over the spatial and angular spread of light within the waveguide (and thus how the light interacts with the extraction elements), maximize the coupling efficiency of light into the waveguide, and improve the mixing of light from various sources within the waveguide (which is particularly important when the color from the sources varies—either by design or due to normal bin-to-bin variation in lighting components). The elements of the waveguide coupling system can use refraction, reflection, total internal reflection, and surface or volume scattering to control the distribution of light injected into the waveguide.

It is desirable to maximize the number of light rays emitted by the source(s) that impinge directly upon the coupling surface in order to increase the coupling of light from a light source into a waveguide. Light rays that are not directly incident on the waveguide from the source must undergo one or more reflections or scattering events prior to reaching the waveguide coupling surface. Each such ray is subject to absorption at each reflection or scattering event, leading to light loss and inefficiencies. Further, each ray that is incident on the coupling surface has a portion that is reflected (Fresnel reflection) and a portion that is transmitted into the waveguide. The percentage that is reflected is smallest when the ray strikes the coupling surface at an angle of incidence relative to the surface normal close to zero (i.e., approximately normal to the surface). The percentage that is reflected is largest when the ray is incident at a large angle relative to the surface normal of the coupling surface (i.e., approximately parallel to the surface).

In one type of coupling, a light source that emits a Lambertian distribution of light is positioned adjacent to the edge of a planar waveguide element. The amount of light that directly strikes the coupling surface of the waveguide in this case is limited due to the wide angular distribution of the source and the relatively small solid angle represented by the adjacent planar surface. To increase the amount of light that directly strikes the coupling surface, a flat package component such as the Cree ML-series or MK-series (manufactured and sold by Cree, Inc. of Durham, N.C., the assignee of the present application) may be used. A flat package component does not include a primary optic or lens formed about an LED chip. A flat emitting surface of the flat package component may be placed in close proximity to the coupling surface of the waveguide. This arrangement helps ensure a large portion of the emitted light is directly incident on the waveguide.

After light has been coupled into the waveguide, it must be guided and conditioned to the locations of extraction. In accordance with well-known principles of total internal reflection light traveling through a waveguide is reflected back into the waveguide from an outer surface thereof, provided that the incident light does not strike the outer surface at an angle less than a critical angle with respect to the surface. Specifically, the light rays continue to travel through the waveguide until such rays strike an index interface surface at a particular angle less than an angle measured with respect to a line normal to the surface point at which the light rays are incident (or, equivalently, until the light rays exceed an angle measured with respect to a line tangent to the surface point at which the light rays are incident) and the light rays escape.

In order for an extraction element to remove light from the waveguide, the light must first contact the feature comprising the element. By appropriately shaping the waveguide surfaces, one can control the flow of light across the extraction feature(s) and thus influence both the position from which light is emitted and the angular distribution of the emitted light. Specifically, the design of the coupling and distribution surfaces, in combination with the spacing (distribution), shape, and other characteristic(s) of the extraction features provide control over the appearance of the waveguide (luminance), its resulting light distribution (illuminance), and system optical efficiency.

Light extracting elements have been designed that can be applied to a waveguide element to obtain a desired illuminance distribution. Such elements are disclosed in U.S. patent application Ser. Nos. 14/472,078 and 14/472,064, owned by the assignee of the present application and the disclosures of which are hereby incorporated by reference herein. Such light extracting elements are disposed on one or more sheets of transparent material that are, in turn, secured by a transparent adhesive to a waveguide element. While a waveguide manufactured using such a process is effective to produce a desired illumination distribution, use of an adhesive reduces efficiency and imposes an extra step and expense into the production resulting in decreased throughput and increased cost.

SUMMARY

According to one aspect, an optical waveguide comprises a waveguide body exhibiting total internal reflection, a substrate, and a plurality of light extraction features disposed on a surface of the substrate. The light extraction features are non-adhesively bonded to the waveguide body.

According to yet another aspect, an optical element comprises an optically transparent substrate and a plurality of light extracting features of optically transparent material that exhibit total internal reflection. The light extracting features are disposed on opposing sides of the substrate. The optical element further includes a waveguide body wherein light extraction features on one of the sides of the substrate are secured to the waveguide body.

According to a still further aspect, a method of forming an optical element comprises the steps of providing a first body of material, forming the first body of material into a first feature having a first size, and reducing the first feature to a second size less than the first size to form a second feature comprising a scaled version of the first feature. The second feature is used as a master in a forming process.

Other aspects and advantages will become apparent upon consideration of the following detailed description and the attached drawings wherein like numerals designate like structures throughout the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary enlarged cross sectional view of an optical waveguide;

FIG. 1A is an top isometric exploded view of the waveguide of FIG. 1 in conjunction with a light source;

FIG. 1B is a bottom isometric view of the waveguide of FIG. 1 with a portion of the substrate broken away and the light source omitted therefrom;

FIG. 1C is a fragmentary side elevational view of one of the light extraction features disposed on the substrate of FIG. 1;

FIG. 1D is an isometric view of a luminaire incorporating the optical waveguide of FIG. 1;

FIGS. 2-5 are enlarged isometric views of alternative light extraction features that may be disposed on the substrate of FIG. 1;

FIGS. 6-22 are fragmentary enlarged cross sectional views of a manufacturing process for producing the optical waveguide of FIG. 1;

FIGS. 23 and 24 are plan views of a sample increase in packing density achievable using the manufacturing process of FIGS. 6-22;

FIG. 25 is a diagrammatic plan view illustrating how replication is used in the process of FIGS. 6-22;

FIGS. 26 and 27 are plan and isometric views, respectively, of working stamps that may be used to create one or more sub-masters or masters in the process of FIGS. 6-22;

FIG. 28 is a plan view of a sample substrate with light extraction features thereon that may be produced by the process of FIGS. 6-22;

FIGS. 29 and 31 are fragmentary enlarged cross sectional views illustrating manufacture of a further waveguide utilizing a substrate with light extraction features on multiple surfaces thereof;

FIGS. 30 and 30A are fragmentary enlarged cross-sectional views of alternative chucks that may be used to fabricate the substrate of FIGS. 29 and 31;

FIGS. 32-34 are fragmentary enlarged cross sectional views illustrating an alternative manufacturing process for the waveguide of FIGS. 29-31.

FIGS. 35 and 36 are fragmentary enlarged cross sectional views of a further manufacturing process for forming an optical element; and

FIGS. 37-43 are fragmentary enlarged cross sectional views of a yet another manufacturing process for forming an optical element.

DETAILED DESCRIPTION

Referring to FIG. 1, a waveguide 100 includes a waveguide element or body 102 typically, although not necessarily, comprising a planar element section 104 having major faces 106, 108 terminating at side edges 110a, 110b, 110c, and 110d. The waveguide 100 further includes an optical element 112 comprising a plurality of light extraction features 113 disposed on and/or in a substrate 114. In the illustrated embodiments, the light extraction features 113 comprise microfeature bodies 116 disposed on a substrate. However, the light extraction features 113 may comprise one or more bodies disposed on and/or in the substrate 114 (i.e., one or more bodies may be on and fully outside the substrate 114, fully disposed within the substrate, or partially inside and partially outside the substrate 114), one or more fully encapsulated or partially encapsulated cavities or voids 115 disposed in the substrate 114, or a combination of such bodies 116 and cavities 115. In the case of bodies 116, such bodies 116 may have the same or a different index of refraction as the index of refraction of the substrate 114. In the case of cavities 115, one or more of such cavities 115 may be fully or partially evacuated, and/or fully or partially filled with air or another material, again, with the same or a different index of refraction. The substrate 114 may be a single layer of optically transparent material or may comprise multiple layers of the same or different materials. In the latter case, one or more of the aforementioned cavities 115 may be formed in the substrate 114 by an absence of material in one or more of the layers.

The waveguide body 102 may be of any suitable shape. In the illustrated embodiment, the waveguide body 102 is planar, although the body 102 may alternatively have any other shape. Further, the substrate 114 may comprise a film, a plate, a block of material, or any other material having a surface and/or a shape that conforms or is conformable to a surface of a waveguide body.

As seen in FIG. 1C, each of the light extraction microfeature bodies 116 has a first end 120 at which a tip portion 122 is disposed, a second end 124 opposite the first end 120 at which a base portion 126 is disposed, and an intermediate portion 128 disposed between the first and second ends 120, 124. The intermediate portion 128 includes a side surface 130. In general, the side surface 130 is preferably (although not necessarily) curved, linear, or a combination of curved and linear portions and is symmetric about a longitudinal axis L and has a cross sectional dimension that decreases from the second end 124 to the first end 120. In the illustrated embodiment, the side surface 130 comprises a rounded shouldered portion 131a disposed adjacent the first end 120 having a substantially constant radius of curvature and a frustoconical or right circular cylindrical portion 131b disposed between the shouldered portion 131a and the second end 124. Further, as noted in greater detail hereinafter, the tip portion 122 is preferably, but not necessarily, planar and non-adhesively bonded to the face 108 of the waveguide body 102, and the base portion 126 is preferably (although not necessarily) non-adhesively bonded to a surface 132 of the substrate 114. Such an arrangement results in the light extraction features 113 being undercut relative to the direction of light extraction.

As seen in FIG. 1A, the waveguide 100 may receive light developed by one or more LED elements or modules 140 disposed on a printed circuit board 142 or other light source disposed adjacent, for example, one of the side edges 110, such as the edge 110a. Each LED element or module 140 may be a single white or other color LED chip or other bare component, or each may comprise multiple LEDs either mounted separately or together on a single substrate or package to form a module including, for example, at least one phosphor-coated LED either alone or in combination with at least one color LED, such as a green LED, a yellow LED, a red LED, etc. In those cases where a soft white illumination with improved color rendering is to be produced, each LED element or module 140 or a plurality of such elements or modules may include one or more blue shifted yellow LEDs and one or more red LEDs. The LEDs may be disposed in different configurations and/or layouts as desired. Different color temperatures and appearances could be produced using other LED combinations, as is known in the art. The luminaire may include LEDs elements or modules 140 of the same type of phosphor-converted white LED, or any combination of the same or different types of LED elements or modules 140 discussed herein. In some embodiments, a luminaire may include a plurality of groups of LED elements or modules 140, where each group may include LED elements or modules 140 having different colors and/or color temperatures. Further, in one embodiment, each LED element or module 140 comprises any LED, for example, an MT-G LED incorporating TrueWhite® LED technology or as disclosed in U.S. patent application Ser. No. 13/649,067, filed Oct. 10, 2012, entitled “LED Package with Multiple Element Light Source and Encapsulant Having Planar Surfaces” by Lowes et al., the disclosure of which is hereby incorporated by reference herein, as developed and manufactured by Cree, Inc., the assignee of the present application. If desirable, a side emitting LED disclosed in U.S. Pat. No. 8,541,795, the disclosure of which is incorporated by reference herein, may be utilized inside the waveguide body. In some embodiments, each LED element or module 140 may comprise plural LEDs that are disposed vertically (i.e., arranged relative to one another in a direction extending between the faces 106, 108 of the waveguide body 102). In any of the embodiments disclosed herein the LED element(s) or module(s) 140 preferably have a Lambertian or near-Lambertian light distribution, although each may have a directional emission distribution (e.g., a side emitting distribution), as necessary or desirable. More generally, any lambertian, symmetric, wide angle, preferential-sided, or asymmetric beam pattern LED(s) may be used.

Any of the embodiments disclosed herein may include a power circuit having a buck regulator, a boost regulator, a buck-boost regulator, a SEPIC power supply, or the like, and may comprise a driver circuit as disclosed in U.S. patent application Ser. No. 14/291,829, filed May 30, 2014, entitled “High Efficiency Driver Circuit with Fast Response” by Hu et al. or U.S. patent application Ser. No. 14/292,001, filed May 30, 2014, entitled “SEPIC Driver Circuit with Low Input Current Ripple” by Hu et al. incorporated by reference herein. The circuit may further be used with light control circuitry that controls color temperature of any of the embodiments disclosed herein in accordance with user input such as disclosed in U.S. patent application Ser. No. 14/292,286, filed May 30, 2014, entitled “Lighting Fixture Providing Variable CCT” by Pope et al. incorporated by reference herein.

Further, any of the embodiments disclosed herein may include one or more communication components forming a part of the light control circuitry, such as an RF antenna that senses RF energy. The communication components may be included, for example, to allow the luminaire to communicate with other luminaires and/or with an external wireless controller, such as disclosed in U.S. patent application Ser. No. 13/782,040, filed Mar. 1, 2013, entitled “Lighting Fixture for Distributed Control” or U.S. Provisional Application Ser. No. 61/932,058, filed Jan. 27, 2014, entitled “Enhanced Network Lighting” both owned by the assignee of the present application and the disclosures of which are incorporated by reference herein. More generally, the control circuitry includes at least one of a network component, an RF component, a control component, and a sensor. The sensor may provide an indication of ambient lighting levels thereto and/or occupancy within the room or illuminated area. Such sensor may be integrated into the light control circuitry.

The components described above may be disposed in a frame or other enclosure 143 (FIG. 1D) to obtain a luminaire 144 suitable for general lighting applications. Light developed by the LED elements or modules 140 is injected into the waveguide body 102 and travels by total internal reflection between the faces 106, 108 of the waveguide body 102. The extraction features 113 extract light out of the face 108 in a desired illumination distribution.

The light extraction bodies 116 may be arranged in a non-random and/or random pattern on the surface 132 of the substrate 114 and positioned between the surface 132 and the surface 108 of the waveguide body 102 when joined to the waveguide body 102. Alternately, the shape, size, or density of extraction elements 113 may be varied across the surface of the substrate 114 in order to produce a desired luminance distribution—for example, to provide a uniform luminance appearance across the light emitting region of the luminaire.

The extraction features 113 of the present disclosure control stray light and provide for high efficiency extraction, highly directional light distributions (i.e., a high proportion of light emitted from one side of the waveguide body 102), and a wide range of illuminance distributions. Various types of lamps or luminaires, including those requiring dispersed or Lambertian illuminance distributions (e.g., typical troffers for general lighting, such as seen in FIG. 1D), collimating distributions (e.g., downlights or spotlights), and light sources requiring specific illuminance patterns (e.g., streetlights, architectural lighting) can be realized using the optical waveguide body 102 and extraction features 113 disclosed herein.

FIGS. 2-5 illustrate further examples of light extraction features 113 that may be disposed on the substrate 114. FIGS. 2 and 3 illustrate light extraction features 116a, 116b, respectively, that have simple curved intermediate portions 128a, 128b each having a side surface 130a, 130b each comprising a section of a circle (i.e., a constant radius of curvature) in cross section. The side surface 130a is convex in cross section whereas the side surface 130b is concave in cross section. The embodiment of FIG. 4 comprises a light extraction feature 116c having a side surface 130c defining a frustoconical portion 150 adjacent a second end 124c and a curved portion 152 having a constant radius of curvature in cross-section disposed between the frustoconical portion 150 and a first end 120c. FIG. 5 illustrates a light extraction feature 116d having a parabolic side surface 130d. The light extraction features 113 may alternatively have a truncated hemispherical shape (FIG. 1) or any other shape(s) (such as prismatic) necessary to produce a desired light distribution.

Referring to FIGS. 1-1C, the extraction features 113, substrate 114, and/or optical waveguide body 102 may be made of the same or different optical grade materials including acrylic, such as an acrylic UV-curable resin, molded silicone, air, polycarbonate, glass, cyclic olefin copolymers, or other suitable material(s) and combinations thereof, possibly, although not necessarily, in a layered arrangement to achieve a desired effect. In one example embodiment shown in FIG. 1, the substrate 114 and the extraction bodies 116 disposed on the surface 132 of the substrate 114 comprise a hot embossed or electroformed acrylic lenticular film 154, as described in greater detail hereinafter. Alternately, the substrate 114 and extraction bodies 116 may be fabricated using one of a variety of techniques typically used in the formation of micro-optical films including nano-imprint lithography, gray-scale lithography, micro-replication, injection/compression molding, reactive ion etching, chemical embossing, drum roll transfer, and the like. Other methods of fabrication include dispensing an acrylic-based UV resin or silicone material on a carrier film that is subsequently cured to form extraction features 113. Further, the film 154 could be fabricated directly on the face 108 of the waveguide body 102 by means of a sacrificial intermediate layer similar or identical to that described in U.S. Pat. No. 8,564,004, the disclosure of which is hereby incorporated by reference herein. Further, additional embodiments may utilize geometries, spacings, methods of manufacture, and any other details related to the extraction features as described in U.S. patent application Ser. No. 14/472,078, entitled “Waveguide Having Unidirectional Illuminance”, filed Aug. 28, 2014, the disclosure of which is incorporated by reference herein. Still further, regions between the extraction bodies 116 after attachment to the waveguide body 102 may partially or wholly comprise a material other than air—for example, a material (including, but not limited to, a solid and/or a fluid) having an index of refraction that is the same as or different than that of the waveguide body 102 and the substrate 114, a vacuum, water, a gas, etc.

FIG. 25 diagrammatically illustrates a process by which the film 154 is formed, irrespective of which light extraction features 113 are used and the pattern of the light extraction features 113 on the substrate 114. The process comprises a replication of elements in successive steps that ultimately results in the formation of a master that can be used to produce a film 154 of a desired size. Specifically, a first element or set of elements 155 is formed that is then used in a first step and repeat process to create a first sub-master 156. The first sub-master 156 is thereafter used in a further step and repeat process to create a further sub-master 157. The steps are repeated until the master 158 is produced. If necessary, the master 158 is converted to a positive embossing master, which is then used in a hot embossing or electroforming process to create film sections. If necessary, the film sections are separated from one another. The film sections are secured by non-adhesive bonding, such as by a hot embossing or thermocompression process, to waveguide bodies to produce waveguides.

Referring next to FIGS. 6-22, the process begins with the fabrication of a microfeature pin 160, which may be made of any suitable material, such as multiple layers of Kapton® by DuPont, or another suitable polyimide or any other suitable rigid material such as metal, plastic, or polymer. The pin 160 is precision laser machined to include an array of microfeatures 162 including a main feature 164 and process features 166. Because in a specific embodiment the present process comprehends exposure of materials to be formed to ultraviolet light, and because the material of the pin 160 is opaque to UV light, a duplicate of the pin 160 must be made of a material that is transparent to UV light. Accordingly, as seen in FIG. 7, the pin 160 is next brought into contact with a first body of uncured material 168 disposed on a UV-transparent substrate 170 and the material 168 is exposed to UV light to harden the material 168. The pin 160 is withdrawn and the resulting body is precision laser machined to obtain a sub-pin 172 disposed on the substrate 170 as seen in FIG. 9. The sub-pin may be made of a cyclic olefin polymer, cyclic olefin copolymer, or another suitable polymer or plastic.

As shown in FIG. 10, the sub-pin 172 as disposed on the substrate 170 is thereafter inverted and brought into contact with a further body of uncured material 174, which is then exposed to UV light to cure the second body 174. The sub-pin 172 is withdrawn and the further body is processed, preferably by precision laser machining, to produce a step and repeat sub-pin 180 shown in FIG. 11.

Referring next to FIGS. 12-15, the step and repeat sub-pin 180 is repeatedly brought into contact with successive bodies 184a, 184b, . . . , 184N of uncured material disposed on a substrate 190. Specifically, the step and repeat sub-pin 180 is brought into contact with the first body 184a (FIGS. 12 and 13), thereafter withdrawn, moved to a position above or adjacent the second body 184b, moved into contact with the second body 184b (FIG. 14), and thereafter withdrawn. The process repeats until all of the bodies 184 have been formed (FIG. 15). Although not shown, each body 184 is exposed to UV light when the sub-pin 180 is in contact therewith to cure the material of the body 184. Also, the bodies 184 may be machined, again by precision laser machining or another suitable process, to obtain a sub-master element 192. The bodies of the sub-master element 192 may be made of a cyclic olefin polymer, cyclic olefin copolymer, or another suitable polymer or plastic. The bodies 184 of the sub-master element 192 are arranged in a desired pattern on the substrate 190, for example a random pattern, a pseudorandom pattern, a regular hexagonal pattern in which centers of the bodies 184 are disposed on vertices of adjacent and contiguous hexagons, a regular rectangular pattern in which centers of the bodies 184 are disposed on vertices of adjacent and contiguous rectangles or squares, etc.

FIGS. 16-18 illustrate fabrication of a master 200 at a desired ultimate film size from the sub-master element 192. Similar to the process used to create the sub-master element 192, the master is produced using the sub-master element 192 in a step and repeat process. Specifically, the sub-master element 192 is mounted on a movable platen 202 (FIG. 16), inverted and brought into contact with a body of moldable material 204 disposed on a stationary platen 206 wherein the material 204 is suitable for mastering in a hot embossing or thermocompression process. The moldable material 204 may be a cyclic olefin polymer, cyclic olefin copolymer, or another suitable polymer or plastic. The platen 202 is thereafter withdrawn leaving the material 204 formed in a positive profile (FIG. 17), moved laterally, and again brought into contact with the material 204. This process is repeated until the entire surface of the material 204 is formed (FIG. 18), thereby obtaining the master 200.

Alternatively, as seen in FIG. 26 the master 200 may be produced using a silicon processing methodology or the master 200 may be produced using a nano-imprint methodology seen in FIG. 27. The former methodology uses a nano-imprinted sub-master 207 to form the master 200 using a step and repeat process.

Referring next to FIGS. 19-21, production of films 154 may thereafter commence using the master 200. In a hot embossing process the master 200 is moved by the platen 202 or another movable element adjacent or above a body of formable material 210 (FIG. 19). The master 200 is then moved into contact with the material 210 as seen in FIG. 20. The temperature and pressure applied to the material 210 and the duration that the temperature and pressure are applied to the material 210 by the master 200 are controlled to obtain a properly formed film 154 (FIG. 21). It should be noted that the film 154 may be manufactured in pre-cut sheet form, or may be produced serially on a web of material that is thereafter cut into individual sheets.

FIG. 23 illustrates film sections 220 that are produced using a conventional film production process whereas FIG. 24 illustrates film sections 154 producible using the forming process described herein. The film sections of FIG. 24 may be separated and trimmed to produce the film 154 shown in FIG. 28. (The extraction features 113 are shown with different scaling in FIGS. 24 and 28.) As should be evident, an increased density of extraction features 113 can be achieved using the present method. The size of the film can be made quite large, e.g., up to 12 in² or larger.

The film sections 154 are bonded to waveguide bodies 102 in a non-adhesive fashion. Specifically, a film section 154 may be accurately brought into position atop a waveguide body face 108 with the light extraction bodies 116 in contact with the face 108 by a heated movable platen 222 (FIG. 21A). Heat and pressure are applied to the substrate 114 (and, optionally, the waveguide body 102) by the platen 222, and, optionally a further platen 224, for a period of time and at a pressure sufficient to bond the microfeature extraction bodies 116 of the film section to the face 108 without adversely affecting the shapes of the extraction bodies 116 and the face 108. The same steps are undertaken when bonding the film 154 to the waveguide body 102 using a thermocompression process, with the applied temperature level, the applied pressure, and the compression duration being modified as appropriate. A finished optical waveguide 100 is illustrated in FIG. 22.

FIGS. 29-34 illustrate the structure and fabrication of an embodiment of a waveguide 300 comprising a waveguide body 302 and an optical element 304 secured to the waveguide body 302. The optical element 304 comprises a substrate 306 having first and second pluralities or sets of optical micro extraction features 308, 310 disposed on opposing faces 312, 314 of the substrate 306. The waveguide body 302 may be identical to or different than the body 102, and the extraction features of the first plurality 308 may be the same or different than the extraction features of the second plurality 310 and the extraction features of one or both pluralities 308, 310 may be of the shapes described hereinabove or may have another shape. The substrate 306 may be identical to or different than the substrate 114. Preferably, the light extraction features 308, 310 and the substrate 306 are formed as described hereinabove, with the exception that the micro extraction features 308, 310 may be simultaneously formed on both faces 312, 314 using first and second masters 316, 318 that are produced using the step and repeat process as described hereinabove and shown in FIGS. 35 and 36. The masters 316, 318 may be brought into contact with the faces 312, 314 of the substrate 306 at the same time by relatively movable platens 317, 319, respectively. Alternatively, the light extraction features 308 and 310 may be formed at different times, if desired.

Once the optical element 304 is formed, the element 304 may be non-adhesively bonded to the waveguide body 302. However, because it is desired to accomplish such bonding using hot embossing or thermocompression without damaging the micro extraction features 310 on the face 314, a chuck 320 (FIG. 30) that partially or completely surrounds the extraction features 310 is used to apply the required pressure and heat to portions of the substrate 306 to effectuate the bonding process. Alternatively, a chuck 320a may be used comprising a plate having relief holes/recesses 321 (FIG. 30A) that align with the extraction features 310 and thereby facilitate application of pressure and/or heat to portions of the substrate 306 without damaging the extraction features 310.

An alternative process seen in FIGS. 32-34 comprehends the use of a further substrate or layer 322 preferably (but not necessarily) non-adhesively bonded in the fashion described hereinabove to the extraction features 310 during manufacture (as seen in FIGS. 32 and 33). The further substrate 322 protects the extraction features 310 during non-adhesive bonding of the substrate 306 and extraction features 308, 310 to the waveguide body 302 as described previously. The further substrate 322 is stripped away as seen in FIG. 34 from the extraction features 310 after the bonding process is complete.

Further processes for creating a master or sub-master for hot embossing, thermocompression, or other methods of forming light extraction features 113 on a substrate 114 as described hereinabove involve the production of a sub-master element having relatively large features and employing a process to reduce the size of the features to obtain a master having microfeatures. For example, as seen in FIG. 35, a sub-master 400 is produced by embossing, patterning, or one or more other production processes by forming features in a shrinkable material (e.g., polystyrene film). The features 404 that are produced have a larger size, but are identically proportioned as compared to the microfeatures that are to be produced at a subsequent point in the overall production process. Once the sub-master is 400 produced the sub-master 400 is heated in a manner to cause the film to shrink to a smaller but proportionally identical three-dimensional shape to obtain a master 402 (FIG. 36) suitable for formation of the optical element 112. This three-dimensional isotropic scaling allows standard manufacturing techniques to be used for formation of features 404 that are thereafter shrunk down in size to microfeatures 406 using controlled heating and the specific material properties of a film. Very precise microfeatures 406 for optical materials, waveguides, mixed materials, and active optical products, such as optical films can be produced. Further, this process could be used to directly manufacture an optical film or to manufacture a master to be used for hot embossing or imprinting of optical films, as noted.

A further process involving the production of a sub-master 410 element having relatively large features 412 and using a process to reduce the size of the features 412 to obtain a master 416 having microfeatures 414 for extracting light from a waveguide is shown in FIGS. 37-43. As seen in FIG. 37, a sub-master 410 is produced by embossing, patterning, and/or one or more other production processes to form features in a polymeric or other material that is suitable for use in a metallic electroforming process. The features 412 that are produced have a larger size but are identically proportioned as compared to the microfeatures 414 that are to be produced at a subsequent point in the overall production process with the exception of the edge-to-edge spacing between the features 412. As should be evident from the discussion below, the manner in which the subsequent reduction in size of the features 412 is undertaken changes such spacing thereby requiring that the initial layout be arranged to compensate therefor.

After the embossing and/or patterning and/or other process(es) are complete, the sub-master 410 is used to produce a master 416 in a metallic electroforming or electroplating process (FIGS. 38 and 39). The electroforming or electroplating is accomplished by electrodeposition on a base comprising the sub-master 410 and is undertaken to a defined thickness that reduces feature sizes to the desired sizes of the microfeatures 414 but maintains the proper proportions thereof. The microfeatures produced by electroforming or electroplating are then replicated directly (FIGS. 40 and 41) to produce an element 418 having a reduced size and shape of microfeatures 419. The resulting element 418 is thereafter used as an insert for hot embossing desired microfeatures 420 in a negative master 422 (FIG. 42) that can thereafter be used to form final microfeatures 423 in a hot embossed substrate 424 (FIG. 43). This process allows for standard manufacturing techniques to be used to form features 423 that are reduced in size using metallic electroforming and hot embossing.

INDUSTRIAL APPLICABILITY

The present disclosure comprehends the use of a bonding process that is adhesive-free to bond two structures permanently preferably using heat and pressure. Other non-adhesive bonding processes may be alternatively or additionally used. Such processes comprehend the use of layers made of materials that can be bonded using light or other electromagnetic radiation, such as UV-curable resins, or layers that are secured together by a bonding agent that does not use adhesives, bonding layers through the use of mechanical motion (e.g., ultrasonic vibration welding), heat welding (e.g., hot gas welding, hot plate welding, laser welding), induction welding, encapsulating materials in one layer with materials of another layer, chemically combining materials at an interface between layers, solvent welding (e.g., acetone, cyclohexane, 1,2-dichloroethane, methyl ethyl ketone, tetrahydrofuran), microscopically and/or macroscopically physically interspersing particles of one layer in another layer, providing a friction-fit, interference-fit, and/or suction fit between layers, securing layers together using one or more mechanical fasteners (e.g., staples, brads, rivets, structural members), or the like.

The process allows careful control of environments inside of optical components and optical materials and may allow for hermetic bonding of materials.

The processes for creating a master or sub-master for hot embossing, thermocompression, or other methods of forming light extraction features on a substrate as well as the electroforming or electroplating processes described hereinabove may be used in conjunction with or separately from the non-adhesive bonding processes contemplated by the present disclosure.

The processes disclosed herein are not limited to manufacturing of optical elements for luminaires. At least some of the disclosed embodiments may be used to form microstructures on or in plastic or polymeric materials generally, to form movable structures in optical materials, and/or to bond mixed optical materials. A still further application is the use of such a forming process to integrate optical MEMS into products.

At least some of the luminaires having optical elements as disclosed herein are particularly adapted for use in installations, such as, outdoor products and indoor products (e.g., downlights, troffers, a lay-in or drop-in application, a surface mount application onto a wall or ceiling, etc., and street lighting) preferably requiring a total luminaire output of at least about 100 lumens or greater, and, in some embodiments, a total luminaire output of at least about 1,000 lumens, and in other embodiments, a total lumen output of about 10,000 lumens to about 100,000 lumens. Further, the luminaires disclosed herein preferably have a color temperature of between about 2500 degrees Kelvin and about 6200 degrees Kelvin, and, in some embodiments, between about 2500 degrees Kelvin and about 5000 degrees Kelvin, and, in other embodiments, about 2700 or 3500 degrees Kelvin. Also, at least some of the luminaires disclosed herein preferably exhibit an efficacy of at least about 80 lumens per watt, more preferably at least about 100, and most preferably at least 120 lumens per watt. Additionally, at least some of the luminaires disclosed herein preferably exhibit an overall efficiency (i.e., light extracted out of the waveguide divided by light injected into the waveguide) of at least about 70 percent, preferably, at least about 80 percent, and most preferably, at least about 90 percent. A color rendition index (CRI) of at least about 80 is preferably attained by at least some of the luminaires disclosed herein, with a CRI of at least about 88 being more preferable, and at least about 90 being most preferable. Some luminaires exhibit a CRI of at least about 90 while maintaining a relatively high efficiency. Any desired particular output light distribution, such as a butterfly light distribution, could be achieved, including up and down light distributions or up only or down only distributions, etc.

When one uses a relatively small light source that emits into a broad (e.g., Lambertian) angular distribution (common for LED-based light sources), the conservation of etendue, as generally understood in the art, requires an optical system having a large emission area to achieve a narrow (collimated) angular light distribution. In the case of parabolic reflectors, a large optic is thus generally required to achieve high levels of collimation. In order to achieve a large emission area in a more compact design, the prior art has relied on the use of Fresnel lenses, which utilize refractive optical surfaces to direct and collimate the light. Fresnel lenses, however, are generally planar in nature, and are therefore not well suited to re-directing high-angle light emitted by the source, leading to a loss in optical efficiency. In contrast, in the present luminaire using the optical elements disclosed herein, light is coupled into the optic, where primarily TIR is used for re-direction and collimation. This coupling allows the full range of angular emission from the source, including high-angle light, to be re-directed and collimated, resulting in higher optical efficiency in a more compact form factor.

In at least some of the present embodiments incorporating the optical elements disclosed herein, the distribution and direction of light within the optical member is better known, and hence, light is controlled and extracted in a more controlled fashion.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and similar references in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the disclosure and does not pose a limitation on the scope of the disclosure unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosure.

Numerous modifications to the present disclosure will be apparent to those skilled in the art in view of the foregoing description. It should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the disclosure.

Claims

1. An optical element, comprising: an optically transparent substrate;first and second pluralities of light extraction features of optically transparent material that exhibit total internal reflection respectively disposed on opposing first and second sides of the substrate; anda waveguide body wherein the light extraction features of one of the first and second pluralities secure the substrate to the waveguide body;wherein the first and second pluralities of light extraction features are non-adhesively bonded to the optically transparent substrate;wherein the light extraction features of one of the first and second pluralities are non-adhesively bonded to the waveguide body; andwherein the optical element comprises non-adhesive bonds on at least three surfaces thereof.

2. The optical element of claim 1, wherein the light extracting features are disposed in one of a non-random arrangement and a random arrangement on each of the opposing sides of the substrate.

3. The optical element of claim 1, wherein the light extraction features are bonded to the sides of the substrate using thermal compression.

4. The optical element of claim 1, wherein the light extraction features are hot embossed to the sides of the substrate.

5. The optical element of claim 1, wherein the light extraction features are formed on the sides of the substrate using a process comprising the steps of producing a sub-master element comprising features that are larger than microfeatures disposed on a master and reducing sizes of the features to obtain the master comprising the microfeatures.

6. The optical element of claim 5, wherein the sizes of the features are reduced by exposing the sub-master element to heat.

7. The optical element of claim 6, wherein the sizes of the features are reduced by electroforming the sub-master.

8. The optical element of claim 1, wherein a bonding chuck at least partially surrounds a portion of the light extraction features during securing of the optical element to a waveguide body.

9. The optical element of claim 1, wherein ends of a first portion of light extraction features are initially disposed on a surface of a further substrate and the further substrate is removed from the ends of the first portion of light extraction features after a second portion of light extraction features are bonded to the waveguide body.