LED circuit boards and light emitting modules

Abstract

A circuit board for a light emitting module comprises a plurality of mounting locations for LEDs, the mounting locations being distributed in a regular two-dimensional pattern on a first surface of the circuit board. The circuit board is characterized by (i) a plurality of transparent regions, each of which extends around one of the plurality of mounting locations, and (ii) a plurality of thermally conductive regions, each of which is thermally and electrically connected to at least one of the mounting locations. An average area of ​​the thermally conductive regions is equal to or greater than 2% of an average area of ​​the transparent regions. Each of the plurality of thermally conductive regions comprises at least a portion that extends as a two-dimensional region on the surface of the circuit board.

Description

[Technical field]

[0001] The present disclosure relates generally to light emitting devices, and more particularly to light emitting devices based on an array arrangement of LEDs. Additionally, the present disclosure relates generally to a modular configuration of a lighting system that may be implemented as a simulated sun and sky lighting system to simulate sunlight and sky. [Background technology]

[0002] Sun and sky simulated lighting systems have been disclosed in several patent applications by the present applicant, in particular, lighting in such systems is based on directional light (representing sunlight-like lighting) that can be generated in a variety of ways, with a focus on compact, energy-efficient light sources.

[0003] SUMMARY OF THE DISCLOSURE Accordingly, it is an object of the present disclosure to, at least in part, improve upon or overcome one or more aspects of conventional systems. Summary of the Invention

[0004] In one aspect, the present disclosure relates to a circuit board for a light emitting module, the circuit board comprising a plurality of mounting locations for LEDs, the mounting locations being distributed in a regular two-dimensional pattern on a first surface of the circuit board. The circuit board has the following characteristics: (i) The circuit board includes a plurality of transparent regions (transparent domains), each of which extends around one of the plurality of mounting locations. (ii) the circuit board comprises a plurality of thermally conductive regions (thermally conductive domains), each of which is thermally and electrically connected to at least one mounting location, and wherein an average area of ​​the thermally conductive regions is at least 2%, at least 4%, or at least 8% of an average area of ​​the transparent regions, and each of the plurality of thermally conductive regions comprises at least a portion that extends as a two-dimensional area on a surface of the circuit board.

[0005] In the present specification and in the appended claims, the expression "two-dimensional area" refers to an area that exhibits an extension in a first spatial coordinate that is substantially unsubjected to a second spatial coordinate. For example, the extension in the first spatial coordinate is less than 15 times the extension in the second spatial coordinate, preferably less than 10 times the extension in the second spatial coordinate, more preferably less than 5 times the extension in the second spatial coordinate. Alternatively, the expression "two-dimensional area" may refer to an area having a significant size, in particular a surface that is at least 3 times, possibly 30 times, more preferably 300 times the size of the light emitting surface (LES) of an LED that is configured to be attached to a mounting location on a circuit board.

[0006] In another aspect, the present disclosure relates to a circuit board for a light emitting module, the circuit board comprising a plurality of mounting locations for LEDs, the mounting locations being distributed in a regular two-dimensional pattern on a first surface of the circuit board. The circuit board has the following characteristics: (i) The circuit board includes a plurality of transparent regions (transparent domains), each of which extends around one of the plurality of mounting locations. (ii) the circuit board comprises a plurality of conductive regions (conductive domains), each of which is electrically connected to two mounting locations, and the average area of ​​the conductive regions is at least 2%, at least 4%, or at least 8% of the average area of ​​the transparent regions; Each conductive region of the plurality of conductive regions includes at least a portion that extends as a two-dimensional area on the first surface of the circuit board.

[0007] In another aspect, the present disclosure is directed to a light emitting module comprising a reflective panel having an inner surface subdivided into a two-dimensional array of surface sections, e.g., surface sections having shapes (e.g., square or hexagonal shapes) that can be combined to cover a generally continuous surface, each surface section including a concave reflective surface area and a thermal contact area outside the concave reflective surface area. The light emitting module further comprises a transparent circuit board having a first surface facing the inner surface of the reflective panel and mounted on the reflective panel, and LEDs distributed (distributed) in a two-dimensional array on the first surface of the transparent circuit board, each LED being associated with one of the concave reflective surface areas. Furthermore, the light emitting module comprises a plurality of thermal conductors that thermally connect one of the LEDs to one of the thermal contact areas, respectively. In particular, during operation of the light emitting module, light emitted from one of the LEDs is reflected by one of the concave reflective surface areas to pass through the transparent circuit board, and heat generated by the LED is diffused by being transferred via the thermal conductor and the thermal contact area to, e.g., the reflective panel. Alternatively, if the light emitting module is equipped with a dedicated heat sink, the heat generated by the LEDs is transferred to the heat sink via the thermal conductor and the thermal contact area.

[0008] In a second aspect, the present disclosure relates to a light emitting module comprising a reflective panel having an inner surface subdivided into a two-dimensional array of surface sections, such as surface sections having a square or hexagonal shape (generally shapes that allow combination to cover a continuous surface), each surface section comprising a concave reflective surface area. The light emitting module further comprises a transparent circuit board having a first surface facing the inner surface of the reflective panel and mounted on the reflective panel, and LEDs distributed in a two-dimensional array on the first surface of the transparent circuit board, each LED being associated with one of the concave reflective surface areas. Furthermore, the light emitting module comprises a lens arrangement spaced from the transparent circuit board at a distance of at least three times the longest dimension in one direction (e.g. the length of one side of a square surface section) (in particular, so as to limit color effects due to refraction, as will also be explained below), and the lens arrangement comprises a plurality of lenses adjacent to each other, each associated with one of the surface sections. In particular, during operation of the light emitting module, light emitted from one of the LEDs is reflected by one of the corresponding concave reflective surface areas to pass through the transparent circuit board and is collimated by one of the lenses of the lens arrangement.

[0009] In another embodiment, a light emitting module comprises a reflective panel, in particular rectangular (e.g. square) in shape, including a regular two-dimensional array of concave mirrors, a transparent circuit board, in particular rectangular (e.g. square) in shape, including at least partially transparent areas, and a regular two-dimensional array of LEDs, in particular arranged on the transparent circuit board according to a square basic array cell, arranged to illuminate the reflective panel and associated with the regular two-dimensional array of concave mirrors, each concave mirror being configured to reflect at least a portion of the light emitted from one of the LEDs through said at least partially transparent area. The reflective panel is thermally connected to the transparent circuit board in areas where the reflected light does not pass through.

[0010] In another embodiment, a circuit board for a light emitting module comprises an (electrically insulating) (e.g. transparent) support substrate, a plurality of LEDs distributed in a regular two-dimensional pattern on a first surface of the support substrate, and a thermal circuit structure, each LED having a heat sink centrally located on a first surface area of ​​the support substrate, the first surface area forming a light-transmitting area of ​​the support substrate extending around the LED. The thermal circuit structure comprises a thermally conductive layer formed on the first surface at a plurality of second surface areas of the support substrate, and a plurality of thermal connections respectively connecting one of the heat sinks and the thermally conductive layer at one of the second surface areas. The circuit board further comprises an electrical circuit structure having a plurality of electrical connections formed on the first surface of the support substrate for supplying power to the plurality of LEDs.

[0011] In another aspect, a circuit board for a light emitting module comprises an (electrically insulated) support substrate, a plurality of LEDs distributed in a regular two-dimensional pattern on a first surface of the support substrate, and an electrical circuit structure for powering the plurality of LEDs, each LED being located in a central region of a first surface region of the support substrate, the first surface region forming a light-transmitting region of the support substrate extending around the LEDs. The electrical circuit structure comprises, at the first surface of the support substrate, a plurality of planar electrical connection sections formed on a second surface region of the support substrate and a plurality of linear electrical connection sections. The plurality of planar electrical connection sections are formed between the first surface regions and define heat removal regions of the support substrate extending outside the light-transmitting region. The plurality of linear electrical connection sections extend across the first surface region to electrically and thermally connect the planar electrical connection and the LEDs.

[0012] In another aspect, the linear electrical connection section has a first thickness in a dimension perpendicular to a surface of the circuit board, and the planar electrical connection section has a second thickness in a dimension perpendicular to the surface of the circuit board, the first thickness being greater than the second thickness, e.g., 1.5 times, 2 times, or 4 times greater.

[0013] In another aspect, the LED-based optical system (light-emitting module) comprises a support substrate having a plurality of mounting positions. The mounting positions are distributed in a regular two-dimensional pattern on a first surface of the support substrate, and the support substrate is transparent to visible light at least in a plurality of transmission regions (light transmission regions), each of which extends around the plurality of mounting positions. The regular two-dimensional pattern is formed such that the distance between adjacent mounting positions in a predetermined direction (e.g., two directions, particularly two orthogonal directions) is equal (uniform). The light-emitting module further comprises a plurality of light sources mounted on the plurality of mounting positions of the support substrate, each light source including at least one LED and a reflecting panel having a three-dimensionally shaped surface mounted on the support substrate. The three-dimensionally shaped surface faces the first surface of the support substrate and includes a plurality of connecting surface sections (thermal contact areas) and a plurality of reflecting surface sections (concave reflecting surface areas). The connecting surface sections extend in a connecting plane and contact the first surface of the support substrate, and each reflecting surface section faces a corresponding transmitting area in the support substrate. A plurality of conductive paths (conductive tracks) (thermal conductors) extend on the first surface and are configured to dissipate heat from the light source and / or provide power to the light source, with at least one of the plurality of conductive paths extending from one of the plurality of mounting locations to at least one of the plurality of connection surface sections.

[0014] [Optical cell] Functionally, the LED and its associated surface section (specifically, the concave reflective surface region) may be considered to form an optical cell, in which the LED is disposed in or near a focal region of the concave reflective surface region and configured to emit light into the concave reflective surface region, which is configured to reflect the light through a transmissive region of the transparent circuit board.

[0015] Multiple optical cells can be considered as a pre-collimated LED self-contained unit (system), particularly suited for lighting applications requiring a directional light beam.

[0016] [Basic shape] Generally, a light emitting module may have a basic shape formed by an array of optical cells, each optical cell comprising an LED and a corresponding "surface" section. Generally, a shape may be selected that allows the combination of "surface" sections to cover a continuous surface. An example of a basic shape is a rectangular basic shape generated by a number of optical cells associated with square surface sections. Another basic shape is obtained, for example, from optical cells associated with hexagonal surface sections that are combined in a honeycomb-like structure.

[0017] As can be appreciated, the various concepts and advantages described above are applicable to various shapes of surface sections. However, for the sake of simplicity, most of the drawings describe the concepts based on an illustrated square, which should not be understood as limiting the range of possible shapes unless certain characteristics of a square shape are advantageous. For example, a square shape of the surface section may be advantageous in implementing the modularity concepts disclosed herein, as it allows for simple tile-like assembly of desired shapes.

[0018] In some embodiments, the shape of the light emitting module is defined by the number and size of, for example, square or hexagonal surface sections of the reflector panel. An exemplary rectangular basic shape comprises m=3 rows of square optical cells, each row comprising, for example, n=3 cells, resulting in a square basic shape of the light emitting module. The number of rows and / or the number of cells per row may be in the range of 3 to 20 (for example, 5 or 10).

[0019] Exemplary dimensions of a light emitting module including secondary collimation by a lens arrangement (lens array) may be, for example, a square base shape with dimensions of 100 mm x 100 mm and a height of approximately 60 mm, or a square base shape with dimensions of 30 mm x 30 mm and a height of approximately 60 mm.

[0020] In some embodiments, multiple optical cells may be combined to form a complete output aperture of the lighting system, as there may be configurations that do not require the modular concepts disclosed herein, e.g., due to specific material selection, efficient thermal management, etc. However, it will be appreciated that the modular concepts disclosed herein may simplify thermal management.

[0021] [Size of the sun and sky simulation lighting system] In particular, when the light emitting module is used in a sun and sky simulated lighting system, the longest dimension of the square surface section (e.g. the length of one side of the square surface section) and thus the lateral dimension of the optical cell may for example be in the range of 1 mm to 50 mm, preferably in the range of 3 mm to 20 mm, e.g. 10 mm. In general, the size of the sun and sky simulated lighting system is determined by the available light output of the LEDs required to provide sufficient luminous flux to the relevant output area corresponding to the respective part of the sky to be simulated.

[0022] [Primary collimation layer (reflective panel)] The inner surface of the reflective panel is subdivided into a two-dimensional array of surface sections. Each surface section comprises a concave reflective surface area and a thermal contact area outside the concave reflective surface area. The concave reflective surface area may be configured as a paraboloid of revolution that focuses the LED positions to emit orthogonal light. The offset of the LEDs relative to the focal positions may be used to tilt the output light beam to a particular angle given by the construction considerations described herein, among others.

[0023] In some embodiments, the concave reflective surface area may be configured as a faceted reflector, which allows for controlled repositioning of rays contributing to a particular location in the secondary collimation layer and homogenization within the channel. The faceted reflector comprises a number of substantially planar (or curved) small reflective facets, each of which has an area substantially smaller than the area of ​​the concave reflective surface, for example 100 times, 1000 times, or 10000 times smaller. In particular, for mini-LEDs, the dimensions of the concave reflective surface area allow for a faceted structure.

[0024] In particular, for lighting that simulates a sky, a perfectly flush plane with uniform luminous flux (brightness) may be desirable. For example, a homogenous sky may be achieved using a flat-topped profile that may be created with a faceted reflector that constitutes a concave reflective surface area.

[0025] The reflective panel may be a metal plate having the required three-dimensional surface shape. It will be understood that if the thermal contact area is used to supply power to the LEDs, an electrical insulator (e.g., a dielectric layer) may be required between the reflective panel and the thermal contact area. The circuit board and / or the reflective panel may be provided with an insulating layer.

[0026] Alternatively, the reflective panel may be a molded plastic panel having a metal coating (e.g., an aluminum coating, or a protective aluminum coating (e.g., SiO2 coated)) covering at least the concave reflective surface area to provide the required reflectivity (e.g., produced by localized metal deposition).

[0027] At the location of the thermal contact area, the panel is thicker (e.g., 1 cm) and a specially provided metal insert may increase the heat transfer from the circuit board to the back side or surroundings of the reflective panel. In the case of a metallic reflective panel, the insulating layer may be part of the circuit board (e.g., applied locally or globally to the first surface). Additionally or alternatively, the insulating layer may form the thermal contact area of ​​the metal insert.

[0028] In some embodiments, the metal insert may be configured as an array of pins for positioning and fixing the reflector panel (or multiple reflector panels) onto the metal frame. The metal frame may thereby ensure a robust mounting of the light emitting module. Additionally or alternatively, the frame may act as a heat sink to transfer heat received from the LEDs to the outside surroundings. The rear surface of the frame may have a grid metal structure, for example an aluminum grid.

[0029] [Thermal Conductor] Generally, the thermal conductor may have a plurality of thermal conductive paths (thermal conductive tracks) extending on the first surface, the thermal conductive paths being configured to assist in dissipating heat from the LED. The thermal conductive paths may also be used to power the LED. Generally, at least one of the thermal conductive paths may extend from the LED to at least one of the plurality of connection surface sections.

[0030] The thermal management disclosed herein addresses the situation where heat generated by the LED during operation is transferred across the light-transmitting area of ​​the support substrate. Obviously, the blocking of the transmitted light needs to be reduced to an acceptable amount. The support substrate in the circuit board may be made of, for example, glass, sapphire, PET, or a transparent polymer (e.g., PMMA, polycarbonate). The support substrate is essentially electrically and thermally non-conductive. Thus, the circuit board may include one or more heat conductors provided on the support substrate. The heat conductor may extend from the mounting position of the LED on the surface of the transparent substrate to an area outside the light-transmitting area. The projected width of the heat conductor (here, the thickness of the heat conductor projected onto the plane of the support substrate) determines the area that blocks light (especially light reflected from the concave reflective surface area) from passing through the light-transmitting area. It will be understood that this area needs to be kept small. Depending on the current passed through the thermal conductor, the length of the thermal conductor and the cross-sectional area required to transfer the heat, the projected width may be, for example, 0.5 mm or less, for example, several hundred micrometers. As mentioned above, the light-transmitting area may be blocked by a light-absorbing structure applied to a support substrate, for example, a thermal conductor, an electrical conductor or an LED (LED mounting device). The ratio of the light-blocking area to the size of the light beam passing through the circuit board (light-transmitting area) is preferably less than 15%, and may be, for example, less than 10%. Depending on the overall configuration of the LED circuit, the ratio of the light-blocking area to the light-transmitting area may be 2% to 5%.

[0031] The origin of the thermal conductor may be, for example, the heat sink of the LED, or an electrical lead supplying power to the LED, etc. Preferably, the shortest path from the LED to the outside (for example, the radial path of the thermal conductor) may be used.

[0032] As described below, the cross-sectional area that blocks light is a parameter that determines transmittance, so the thermal conductor may extend, for example perpendicular to the substrate, to maintain a small projected width while still providing sufficient cross-sectional area for heat flow.

[0033] An alternative electrical and / or thermal connection may be based on an ITO layer (indium tin oxide layer). The ITO layer may be applied to essentially cover the entire first surface of the support substrate (e.g. 95% or 92% of the first surface) or to act as a local conductive connector. It should be noted that if the light transmitting area is completely covered, losses in the range of 20% to 10% or less may occur, especially if only limited areas are covered with the ITO layer.

[0034] [Main light source panel (PCB with multiple LEDs)] In some embodiments, the transparent circuit board may be a printed circuit board (PCB) based on a support substrate. Generally, the support substrate may be made of a transparent material. The transparent material is a material (e.g., glass, sapphire, PET, or a transparent polymer (e.g., PMMA, polycarbonate, etc.)) that is transparent to LED light (generally visible light). The transparent material has a transparency of, for example, 75% or more (e.g., 85% or more, or 95% or more), and preferably has a transparency of more than 98% in the case of glass or sapphire (without a light-shielding structure on the surface). The support substrate may be printed with electrical connections for electrically connecting to the leads of the LEDs, thereby forming a number of specific LED mounting positions. The LED mounting positions may be equally spaced as a first two-dimensional array (e.g., square or hexagonal) ("first matrix"). The LED mounting positions may be provided as LED holders that electrically contact the easily mounted LEDs to the electrical connections. Alternatively, solder contacts may be provided to connect the LED to its electrical connections. The electrical connections (leads) of the LED may also act as thermal conductors.

[0035] [LED] The lateral dimensions of the light-emitting area of ​​the LED may be in the range of several hundred micrometers (e.g., 100 micrometers to 800 micrometers, or 200 micrometers to 600 micrometers), for example 400 micrometers (often called "mini LEDs" in contrast to micro LEDs or conventional larger LEDs).

[0036] For uniform light output, substantially identical (mini) LEDs can be used within substantially identical optical cells (e.g., substantially identical geometric shapes of concave reflective surface areas and lenses).

[0037] The LEDs of the pre-collimated LED built-in unit are arranged on the transparent circuit board with a pitch D that is significantly larger than the "average" size d of the mini LEDs (e.g., 5 times, 10 times, 15 times, preferably 20 times larger). With respect to the distance between the primary collimation layer (first collimation layer) and the secondary collimation layer (second collimation layer), the pitch between the LED mounting positions may be 3 or 4 times smaller than the distance. For example, the pitch between the LED mounting positions may be 3 mm to 15 mm, e.g., 10 mm.

[0038] A pitch within the range specified above allows the optical system to be properly adjusted within a predetermined tolerance.

[0039] For example, starting from a required light output of 10000lm-25000lm per square meter in a sun-sky simulated lighting system, with an efficiency of 30%, a light emitting module containing 100 optical cells and having a side length of 10 cm will require 300lm-800lm, and the required light output of one optical cell will be 3lm-8lm. Such light output can be provided by a mini-LED (e.g. 0.4mm x 0.4mm light emitting area) powered at, e.g. 0.1W and with an efficiency of 50-100lm / W at standard operating temperature. Thus, even with high LED efficiency (e.g. 90%), a large amount of heat needs to be removed from a very small area (LED) and typically from a large skylight. In addition, the heating of the components due to the absorption of a large amount of light needs to be taken into account. In the present disclosure, a thermal management approach is proposed to ensure the operating temperature and long-term operation of mini-LEDs. The thermal management proposed in this disclosure takes into account the thermal resistance of the heat conductor (e.g., determined by the cross-sectional area and length of the wires), the impact on the light output uniformity (affected by losses due to the presence of the wiring), thermal expansion, etc.

[0040] The lateral dimensions of the light-emitting areas are in the range of several hundred micrometers, and in combination with an optical layer with a fairly large pitch (e.g., 10 mm), this allows beam divergence angles (FWHM: full width at half maximum) in the range of 3° to 20° (e.g., 10°). This allows the desired optical setup to produce uniform illuminance at distances as short as 100 mm to 200 mm. Such a combination of parameters (distance and divergence) is said to be suitable for sun-sky simulated lighting systems, but may not be suitable for uniform backlighting applications in screens, where much thinner systems would usually be required.

[0041] The inventors further realized in this context that LEDs with large emitting areas may require a larger pitch and / or distance between the LEDs to achieve uniform illumination. On the other hand, LEDs with small emitting areas require more costly technology due to the need for greater precision during assembly and operation. Furthermore, the overall efficiency may be reduced, power consumption may increase, and heat dissipation may be difficult. Based on the above considerations, a range of sizes of emitting areas in configurations particularly suited for sun and sky simulated lighting systems may be optimized with respect to geometric, power, and cost parameters.

[0042] [Consideration of thermal expansion] There may be limitations on the thermal expansion of the components of the light emitting module. For example, in some embodiments, the linear thermal expansion coefficient of the transparent circuit board and the linear thermal expansion coefficient of the reflective panel may differ by less than 10 times (preferably less than 5 times, or less than 2 times, e.g., 1.5 times), e.g., to ensure optical alignment. Assuming that the intended location of the LED is at the focal point of the concave reflective surface area, it will be recognized that a misalignment of the LED relative to the focal point may affect the light passing through the optical cell. This misalignment may cause a tilt in the output direction, affecting the uniformity of the output light beam by partially passing through non-corresponding light transmitting areas and / or non-corresponding lenses in the secondary collimation layer.

[0043] In some embodiments, the product of (i) the difference in linear thermal expansion coefficient between the transparent circuit board and the reflective panel and (ii) the linear dimension of the light emitting module that determines the difference in thermal expansion between the board and the reflective panel may be set to be smaller than the dimension of the light emitting area of ​​the LED in one direction. For example, the product may be preferably less than 1 / 2, more preferably less than 1 / 3, even more preferably less than 1 / 5, or in the range of 1 / 10, with respect to a temperature change of 20° C., more preferably 30° C., and most preferably 50° C.

[0044] For example, in the case of an aluminum reflector with a linear thermal expansion coefficient α = 22 (μm / m / C) and an acrylic support substrate with a linear thermal expansion coefficient α = 70 (μm / m / C), the linear dimension of the module needs to be less than 100 mm so that the relative LED light-emitting area shifts less than 1 / 3 for a 0.4 mm × 0.4 mm LED light-emitting area for a temperature change of 30°C.

[0045] As another example, for a sapphire support substrate (thermal expansion coefficient α=5), a module up to 300 mm wide may be acceptable for the same LED. Of course, if the temperature change is large, a smaller module may be required. For example, for a temperature change of 50°C, a 60 mm wide acrylic support substrate or a 180 mm wide sapphire support substrate may be mounted on top of an aluminum reflector panel.

[0046] In some embodiments, the product of (i) the linear thermal expansion coefficient of the secondary collimation layer and (ii) the linear dimension of the light emitting module that determines the thermal expansion of the collimation layer can be kept small to avoid damage due to stress. For example, said product can be selected to be less than 10%, preferably less than 5%, more preferably less than 2%, such as about 1%, of the (linear) dimension of the optical cell when the temperature change of the secondary collimation layer is 20° C., more preferably 30° C., most preferably 50° C.

[0047] For example, for an acrylic secondary collimation layer, ensuring less than 5% thermal expansion (e.g., less than 0.5 mm expansion) of the linear dimensions of an optical cell with a side length of 10 mm may limit the size of the light emitting module to 240 mm for a target specification that allows for a thermal change of 30° C. Assuming a maximum thermal expansion of only 2% of the linear dimensions of the optical cell to ensure optimal uniformity of the luminance (illuminance) profile between adjacent modules, the size of the light emitting module may be limited to 100 mm.

[0048] [Heat sink] In addition to a (first) e.g. square / hexagonal two-dimensional array ("first matrix") of equally spaced LED mounting locations (e.g. LED holders), the transparent circuit board may also include a second e.g. square / hexagonal two-dimensional array ("second matrix") of equally spaced heat sinks (heat sinks) at the locations of the thermal contact areas. The second two-dimensional array is identical to the equally spaced two-dimensional array of LED mounting locations, but is offset laterally or diagonally relative to the equally spaced two-dimensional array of LED mounting locations, such that, e.g., there is always one heat sink between two adjacent LEDs along a row or diagonal line, respectively. Each LED mounting location (e.g. LED holder) may be thermally connected (e.g., via a metal wire) to at least one heat sink.

[0049] The heat sink may be located where the local luminous flux is minimal or zero. The heat sink may therefore have a significant size, specifically a surface size at least 3 times, possibly 30 times, more preferably 300 times larger than the size of the LED (or, relative to the optical cell, more than 5%, 10%, 20% of the projected area of ​​the optical cell), which facilitates efficient heat transfer to the reflector panel. In a configuration where the second two-dimensional array is offset diagonally, a larger heat sink may be used since the heat sink may be located at a greater distance from the LED than when the second two-dimensional array is offset laterally.

[0050] There are various options for transferring heat from the heat sink to the reflector panel.

[0051] In one example configuration that is particularly suited to the aforementioned oblique offset, the heat sink is placed in contact with the reflector panel at the thermal contact area, which may specifically be the corner or side of the surface of the surface section. It is believed that in order to efficiently transfer heat to the final heat sink (e.g., the flat bottom surface of the reflector panel), at least the heat transfer "channel" of the heat sink needs to be metallic. Therefore, electrical connection between the heat transfer "channel" (the reflector panel) and the electrical circuit for powering the LEDs needs to be prevented. For example, the heat sink covers the thermal contact area and is made of a suitable electrically insulating thermal pad (e.g., a thin layer of aluminum nitride or other material with high thermal conductivity and low electrical conductivity). Especially considering that the electrical connection between the electrical circuit and the heat transfer "channel" needs to be cut at some point, the place where this can be done is the thermal contact area, which allows a larger surface area compared to other connection points (e.g., the location of the LEDs).

[0052] Another exemplary configuration, particularly suitable for lateral offset, provides thermal contact at some distance from the reflector panel. For example, the entire space between the circuit board and the reflector panel may be filled with a transparent filler. This also allows to minimize losses due to Fresnel reflection at the interface. The filler also fills the gap between the heat sink and the reflector panel. Even if the filler is not a highly thermally conductive material, the thickness of the filler is made thin enough and the surface of the heat sink is made large enough to ensure adequate heat transfer to the reflector panel.

[0053] In another exemplary configuration suitable for diagonal offset, the LED traces are straight, but each point on the trace between two LEDs is still thermally connected to a heat sink.

[0054] In all exemplary configurations, the LEDs are wired in series from the on (positive) side to the opposite (negative) side of the light emitting module, with each pole maintained at a fixed potential, and a series connection may be made between LED groups, ensuring more uniform light extraction.

[0055] [Electrical connection] The electrical connections may provide a series connection between lines (groups) of LEDs that extend from one side of the transparent circuit board to the other side of the transparent circuit board. If the second two-dimensional array is offset laterally, the electrical connections may be provided by linear connections connecting the LEDs of adjacent optical cells through centers along the sides of the optical cells. If the second two-dimensional array is offset diagonally, the electrical connections may follow a zigzag path to connect the LEDs of adjacent optical cells through corners of the optical cells.

[0056] Groups of serially connected LEDs may include multiple rows or lines to increase the total number of LEDs per group, which may improve the uniformity of light extraction between different groups.

[0057] [Separate heat dissipation paths (heat dissipation tracks)] Additionally or alternatively, the transparent circuit board may be provided with specific heat dissipation paths (heat dissipation tracks), which may also be printed, but which may be electrically isolated from the electrical paths (electrical tracks) that supply power.

[0058] [Pillar-like structure] Generally, the transparent circuit board can be supported by the thermal contact area. Furthermore, for example in the case of a rectangular basic shape, the light emitting module may comprise pillar-like structures at the four corners, especially if a secondary collimation layer (see below) needs to be attached. Preferably, the pillar-like structures extend to the outer area of ​​the incident and reflected light. For example, at the height of the printed circuit board (PCB), the pillar-like structures may have their (for example triangular) cross-sectional dimensions associated with a range of a few millimeters (for example, 3 mm). As the emitted light beam spreads, the cross-section of the pillar-like structures narrows, for example at the height of the secondary collimation layer, the cross-sectional dimensions may taper down to, for example, 1 mm.

[0059] [Secondary collimation layer (lens panel)] The secondary collimation layer may be structurally coupled (rigidly connected) to the primary collimation layer to ensure consistent desired optical alignment. For example, in addition to supporting a transparent circuit board, the pillar-like structure may further support an output lens arrangement (lens array / lens panel) (e.g., including one lens on top of each optical cell or one lens associated with each optical cell). To achieve a fully flushed output aperture in the light-emitting module, the lenses are shaped (e.g., square / hexagonal) with the length of one side of the optical cell and are adjacent to each other. Furthermore, the lens panels of adjacent light-emitting modules may be configured to ensure an extended, fully flushed output aperture in the multiple light-emitting modules.

[0060] Preferably, the lenses are mechanically attached with high precision to form a kind of "monoblock", i.e. the light emitting module can be constructed as a rigid unit with a pre-set (fixed) optical alignment.

[0061] It should be noted that the output light of the light emitting module is only slightly, if at all, chromatically affected. Thus, primary collimation of the light emitted by the LEDs is achieved by the associated reflective surface areas. Final collimation is achieved only through the associated lenses. As a result, the lenses are spaced apart at a distance of at least 3 times the length of the optical cell and less than 10 or 20 times (e.g. 5 or 8 times). In such a configuration, the diameter of the e.g. circular reflective surface areas may be smaller than the length of the optical cell. Thus, the pillar-like structures may be tapered with a cross-sectional area decreasing with the distance to the reflective panel.

[0062] For orthogonal output beams, the output lens may receive and collimate light reflected from a concave reflective surface area located directly beneath the lens.

[0063] It should be noted that, assuming additional pillar-like structures are introduced into the cross-section of the light-emitting module, openings may be required in the transparent circuit substrate.

[0064] Furthermore, when multiple light emitting modules are assembled in combination, the pillar-like structures may be shared between adjacent light emitting modules. In the case of a square or rectangular shaped light emitting module, up to four light emitting modules may share a pillar-like structure, and multiple pillar-like structures composed of up to four light emitting modules may be fixedly attached to each other. Thus, the cross section of the pillar-like structure in a single light emitting module may be triangular, but the cross section of the pillar-like structure shared or composed in common by four light emitting modules may be square.

[0065] In particular, with respect to configurations using mini-LEDs, the optical configurations disclosed herein may be based on a three-stage collimation concept, including (a) a concave shape of the reflective surface area, (b) a facet concept implemented on the reflective surface area, and (c) a secondary collimation layer. The first two stages are insensitive to the chromaticity of the light, while the secondary collimation layer only contributes slightly to the final collimation within a certain allowable chromaticity distortion. Therefore, the system (optical system) is essentially free of chromatic aberration.

[0066] Tilt Alternatively, for a tilted output beam, the concave reflective surface area reflects the LED's light at an oblique angle rather than orthogonally, and the reflected light is received and collimated, for example, from a single lens associated with an adjacent or further away optical cell. In this way, the tilt of the output beam can be structurally limited to a discrete set of tilt angles depending on the size of the optical cell.

[0067] It should be noted that based on this concept, multiple output beams with different tilt angles can be generated.

[0068] [Lighting system] In another aspect, a lighting system based on an arrangement of multiple light emitting modules arranged in a line or according to a two-dimensional arrangement (2D array), or any shape that can be formed by multiple modules, is disclosed. The size of the light emitting modules is selected so that thermal effects (e.g. deformations) do not affect the arrangement of the optically active elements (LEDs, concave reflective surface areas, lenses) beyond acceptable limits. Thus, adjacent light emitting modules can be mounted with a certain distance between them, at least in the area of ​​the transparent circuit board and the reflector. For this reason, the outer optical cells are slightly reduced in size on the connecting side, resulting in a "tapered" light emitting module that allows for larger thermal fluctuations in the area of ​​the heat source "LEDs".

[0069] To ensure proper mounting, the lighting system may include a frame for mounting the multiple light emitting modules at correct distances from each other.

[0070] For an inclined output beam, the arrangement of the light emitting modules may be such that light emitted from one of the light emitting modules passes through a secondary collimation layer of another light emitting module.

[0071] Additionally, a fly's eye homogenizer based on two regular microlens arrays (i.e., lens arrays with many lenslet pairs per optical cell) in a tandem configuration may be used to homogenize the light output.

[0072] In some embodiments, the optical cell has a substantially polygonal cross-section, for example, where at least one thermal contact area is located at a vertex of the polygonal cross-section.

[0073] In some embodiments, the concave reflective surface area substantially conforms to the shape of a paraboloid of revolution associated with a focal point at the location of the associated (corresponding) LED.

[0074] In some embodiments, the transparent circuit substrate is configured to transfer heat generated by the LED to the at least one thermal contact area.

[0075] In some embodiments, the transparent circuit board is configured to connect an external power circuit to a first lead of the LED at a first potential and to connect an external power circuit to a second lead of the LED at a second potential.

[0076] In some embodiments, the electrical connections are implemented as tracks or wires that also transfer heat to associated (corresponding) thermal contact areas that are electrically insulated from the electrical connections.

[0077] In some embodiments, the electrical connections are made from an optically transparent material.

[0078] In some embodiments, the electrical connections are made from a transparent film.

[0079] In some embodiments of the circuit board, the average area of ​​the second surface region associated with an LED is at least 2%, e.g., at least 4%, or at least 8% of the average area of ​​the first surface region associated with an LED.

[0080] In some embodiments of the circuit board, a plurality of LEDs are mounted to the support substrate at a plurality of mounting locations, respectively.

[0081] In some embodiments of the circuit board, the electrical resistivity (Ω·m) of the conductive region is 10 times, preferably 10 times, more preferably 10 times less than the electrical resistivity of the transparent region, and / or the transparency of the transparent region is at least 10 times greater than the transparency of the conductive region.

[0082] In some embodiments, the circuit board further comprises a thin, opaque electrical connector extending across the transparent region, for example configured as a substantially planar connector with a larger surface oriented at an angle, particularly perpendicular, to the first surface of the support substrate.

[0083] In some embodiments of the circuit board, the conductive area is at least partially covered by an insulating layer. In some embodiments of the circuit board, the conductive area is made of a single material or two different materials. In some embodiments of the circuit board, the conductive area covers at least 90% of the area of ​​the support substrate that is not associated with a transparent area.

[0084] Other features and aspects of the present disclosure will become apparent from the following description and the accompanying drawings. [Brief description of the drawings]

[0085] The following accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0086] [Figure 1A] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 1B] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 1C] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 1D] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 2A] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 2B] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 2C] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 2D]1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 3A] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 3B] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 3C] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 3D] 1 is a schematic diagram of an exemplary light emitting module and its components. [Figure 4A] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 4B] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 5A] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 5B] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 5C] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 6A] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 6B] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 7A] FIG. 1 is a schematic diagram of LED bonding to thermal contacts. [Figure 7B] FIG. 1 is a schematic diagram of LED bonding to thermal contacts. [Figure 8A] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 8B] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 8C] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 8D] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 9A] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 9B] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 9C] 2 is a schematic diagram of a reflective panel and respective light emitting modules. FIG. [Figure 9D]2 is a schematic diagram of a reflective panel and respective light emitting modules. FIG. [Figure 10A] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 10B] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 10C] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 11A] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 11B] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 12A] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 12B] 1 is a schematic diagram of an exemplary circuit board configuration. [Figure 13A] 1 is a schematic diagram of an exemplary arrangement and configuration of light emitting modules. [Figure 13B] 1 is a schematic diagram of an exemplary arrangement and configuration of light emitting modules. [Figure 13C] 1 is a schematic diagram of an exemplary arrangement and configuration of light emitting modules. [Figure 14] 1 is a schematic diagram of an exemplary arrangement and configuration of light emitting modules. [Figure 15] FIG. 13 is a schematic diagram of another circuit board configuration. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0087] Hereinafter, exemplary embodiments of the present disclosure will be described in detail. The exemplary embodiments described herein and shown in the drawings are intended to teach the principles of the present disclosure, and those skilled in the art may implement and use the present disclosure in many different environments and applications. That is, the following exemplary embodiments are not intended to be, and should not be considered as, descriptions limiting the scope of patent protection. Rather, the scope of patent protection is defined by the appended claims.

[0088] The present disclosure is based in part on the realization that a modular concept based on a plurality of light-emitting modules may enable lighting systems of various shapes (e.g. square, rectangular, various sizes and lengths, L- or T-shaped, honeycomb structure, etc.). It has further been found that the modular concept allows a desired precision in the mutual alignment of the LED channels despite temperature variations. In particular in a sun and sky simulation lighting system intended to simulate the appearance of an uninterrupted sky, it has been found that limiting the size of the light-emitting modules may result in imperceptibly small gaps at the boundaries. It has further been found that the modular concept allows a desired tolerance in the spatial separation between adjacent light-emitting modules, in particular between the secondary collimation layers of adjacent light-emitting modules. Said tolerance may be set in such a way that the brightness / illuminance profile generated does not have any visible gaps, for example at the height (level) of a fully flushed plane. (A fully flushed plane with uniform luminous flux / brightness may be used to generate the appearance of a uniform sky, for example based on Rayleigh scattering.)

[0089] As a result of the modular concept, it has further been found that all optical layers (e.g. reflector, transparent circuit board with multiple LEDs, and collimation layer) are preferably firmly connected within one module with precision. Furthermore, the use of multiple essentially identical modules allows adjacent identical modules to be arranged in a seamless configuration.

[0090] Furthermore, the present disclosure is based in part on the recognition that LED-based devices may require thermal management for long-term operation. Thermal management may be implemented especially in configurations using transparent carrier boards (e.g., transparent circuit boards or printed circuit boards (PCBs)) that often have poor thermal conductivity. This aspect may also have an impact on configurations where a high level of optical alignment needs to be maintained. That is, thermal management aspects may be considered for the modular concept of a combination reflector panel and transparent circuit board configuration, both in combination and separately.

[0091] In particular, it has been found that electrical and / or thermal connections to the reflector panel can be used to dissipate heat from the LEDs. In a sky-reproducing lighting system, the appearance of the optical cells should be as similar as possible to adjacent cells in the same module (or the entire lighting system, if it is composed of a single large "module"). Coupled with the importance of such uniformity, it has been found that heat is preferably "vertically" flowing within the module, i.e., from each LED to each "base" of the reflector panel, and then essentially dissipated on the face of the reflector panel opposite the reflective surface area. In contrast, current can flow horizontally, i.e., in the plane of the transparent circuit board, to power, for example, a string of serially connected LEDs. As a concept for heat dissipation, the inventors have identified several geometric considerations and aspects. (i) Because transparent circuit boards are less efficient at conducting heat, thermal conductors (limited areas of thermally conductive material) can be selectively provided in areas of the circuit board through which light passes, especially when opaque thermal wiring is used. (ii) the reflected light may not pass through all areas of the circuit board: if a larger surface area is involved to transfer heat, these areas need to be located away from the LEDs, preferably outside the areas of the circuit board through which light passes; (iii) The materials used and the circuit layout must be configured to reduce the risk of electrical shorts, for example between LEDs at different electrical potentials. (iv) To ensure that all LEDs have the same or similar operating conditions (e.g., as close as possible to a common current), the LEDs should be connected in series, e.g., in groups of equal numbers of LEDs. For example, each group of LEDs should be arranged in a row, with an odd number of rows ensuring equal potentials for connections on the same side of the module. (In the case of multiple rows, the total number of rows per module may be any suitable multiple of such rows.) (v) It has been found that a convenient approach is to remove heat from the LED via electrical wiring (eg, copper wire), thereby minimizing the footprint near the LED. (vi) It has been found that the wiring near the LED does not necessarily have to have a circular cross section and does not necessarily have to be applied flat on the circuit board. Instead, flat wires can be arranged vertically, for example with the largest surface side of the wire arranged parallel to the light beam. This can minimize "shadows" on the transparent circuit board or on transparent circuit board areas through which light passes along a light transmission direction that is essentially perpendicular to the plane of the circuit board. (vii) Farther away from the LEDs, the wiring can expand the area on the circuit board, especially when passing by material from the reflector panel. This can significantly expand the surface area of ​​the wiring for effective heat exchange. This is feasible because the shadowing problem is not so great in the outer areas. The heat transfer to the reflector panel may be done via a heat sink (part), which is for example a non-conductive layer on the thermal contact area. Note that the heat sink may be made of metal (for example aluminum) to make it cheap, so that the electrical connection between the LED and the heat sink "reflector panel" may be interrupted, and therefore there is a risk of an electrical short circuit between the optical cells. It has been found that for sufficiently large surfaces (for example flat areas with a diameter of 2-3 mm, corners of squares or hexagons, etc.), a sufficiently low thermal resistance (high resistivity but low resistance due to the large area) can be achieved by a thin layer of electrically insulating material. For example, a suitable thermal pad or a thin connector of aluminum nitride can be used as a connection between the electrically conductive spot and the metal body of the reflector panel. In some embodiments, even a thin dielectric (e.g., a thin polymer insulating film) may be adequate to provide the desired electrical insulation and the desired thermal conduction due to the relatively low voltages at which the LEDs are operated. (viii) Various configurations are proposed herein for electrically connecting multiple LEDs, in which, for example, a conductor passes between two LEDs across the thermal contact area while remaining electrically isolated. For embodiments intended for heat dissipation at the corners of the optical cell (where, as mentioned above, there is more space for thermal contact areas outside the light-transmitting area at the corners of the square surface section), the electrical connections of the LEDs may follow a zigzag path. For a linear path of the electrical connections of the LEDs, passing through corners may not be feasible if the length of the wiring needs to be kept as short as possible. In some cases, there may be enough space for thermal contact areas on the side of the optical cell (depending on the shape and extent of the concave reflective surface area), even though the area available for unshaded heat dissipation on the side may be smaller. (ix) In general, the interface between the electrical connection and the reflective panel can be filled with an insulating material that provides thermal conduction. If the gap is small, a transparent resin can be selected as the filler, taking into account the balance between cost and thermal conductivity. (x) Finally, the entire well formed in the reflective panel between the transparent circuit board and the reflective panel may be filled with insulating resin, which may further minimize reflection losses. It should be noted that in some alternative embodiments, the insulating resin may be considered as a kind of transparent circuit board supporting the LEDs instead of a solid transparent circuit board, and precise positioning of the LEDs may be required.

[0092] Furthermore, the present disclosure is based in part on the recognition that, when configured to functionally cooperate with a reflective panel, a transparent circuit board (e.g., a transparent PCB) may already provide thermal management based on the underlying circuitry. Specifically, the inventors propose a basic concept of an inventive topology of the spatial layout of thermal / electrical domains of the circuit board, which makes it suitable for combination with various types of reflective panels.

[0093] From a general perspective, a circuit board for a light emitting module comprises a plurality of mounting locations for LEDs, which are distributed in a regular two-dimensional pattern on a first surface of the circuit board.

[0094] The two-dimensional pattern forms a plurality of surface sections on the first surface.

[0095] The surface sections have essentially the same shape and are each associated with one mounting location and one LED as a heat source.

[0096] With respect to an optical use / configuration of the circuit board (e.g., an optical configuration in which LED light is collimated and redirected through the circuit board), the circuit board is characterized by a plurality of transparent regions, each of which is part of a respective surface section and extends around a mounting location of the respective surface section. When the circuit board is mounted on a reflector panel for optical use, the transparent regions ensure that light generated from the LEDs and reflected by an associated collimated portion of the reflector panel is able to pass through the circuit board.

[0097] With regard to thermal management, the circuit board may be further characterized by a plurality of thermal conduction regions. Each thermal conduction region is a portion of a respective surface section, but is arranged such that the thermal conduction regions are located outside the transparent regions. When the circuit board is mounted on the reflector panel for optical use, the thermal conduction regions allow heat generated by the LEDs during operation to be transferred to the reflector panel via the thermal conduction regions. For example, the reflector panel and the circuit board are in surface contact at the thermal conduction regions.

[0098] For efficient heat transfer, the average area of ​​the thermally conductive regions is, for example, at least 2%, such as at least 4%, or at least 8% of the average area of ​​the transparent regions.

[0099] It can be seen that the heat generated by the LEDs needs to flow through the transparent region to the thermally conductive region. However, allowing this heat flow should mitigate the impact on the transparency of the transparent region. Thus, the heat source, i.e., the thermal conductor that thermally connects the LED to the thermally conductive region, may be configured to be transparent or nearly transparent, or may have a "small" size projected onto the first surface and block only an acceptable amount of light.

[0100] Generally, the thermally conductive region may comprise a thermally conductive material / layer of thermally conductive material that may be transparent or opaque as it is disposed outside the transparent region.

[0101] The thermally conductive area may also be used to provide power to the LEDs, i.e., be part of the power circuit of the LEDs. In this case, the thermally conductive area may be electrically connected to the leads of the LEDs via an electrical and thermal conductor. A group of LEDs connected in series may also include a thermally conductive area.

[0102] Hereinafter, light emitting modules according to various embodiments will be described with reference to FIGS.

[0103] 1A to 1D are schematic diagrams of a light-emitting module 1 according to an example. Specifically, FIG. 1A is a schematic diagram of a cross section of the light-emitting module 1, FIG. 1B is a schematic diagram of the top surface of the reflective panel 3, FIG. 1C is a schematic diagram of the bottom surface of the transparent circuit board 5, and FIG. 1D is a diagram of the lens panel 7. As shown in FIG. 1A, the components of the light-emitting module 1 are attached together by four pillars 9. As an example, the light-emitting module 1 is based on a two-dimensional 10 row by 10 column array of optical cells having, for example, a square basic shape. The reflective panel 3 has an inner surface 3A (see FIG. 1A). The inner surface 3A is subdivided into a two-dimensional array of a plurality of square surface sections 11, which correspond to the square basic shape. Note that the square surface sections 11 are shown separated by dashed lines. Each square surface section 11 comprises a concave reflective surface area 11A (indicated by dashed lines on each of the two square surface sections 11) and a thermal contact area 11B located outside the concave reflective surface area 11A. The shape of the thermal contact area 11B is determined by the shape of the concave reflective surface area 11A. The body of the reflective panel 3 acts as a heat sink for heat generated during operation of the light emitting module 1. In particular, the lower surface 3B of the reflective panel 3 (see FIG. 1A) can be used to remove heat from the light emitting module 1.

[0104] 1B, the concave reflective surface area 11A forms the primary collimation layer and is shown as a circle, such that the perimeter of the concave reflective surface area 11A at the thermal contact area 11B is configured to be larger at the corners of the square surface section 11 than along the sides of the square surface section 11.

[0105] FIG. 1B further shows, at the four corners of the reflective panel 3, pillars 9, for example with a triangular cross section, which form the corners of the light emitting module 1.

[0106] In general, the secondary collimation layer (lens panel 7) can be suspended by suitable "poles" (pillars). A robust configuration for achieving the smallest pole size can be, for example, four poles with a tapered contour with a triangular base arranged at the four corners. The triangular cross section allows a square cross section to be formed when the four poles of four adjacent light emitting modules are connected. The tapered structure ensures a large base for the reflective surface, which is easy to extrude. In this case, the light spot (diameter of the light beam reflected from the concave reflective surface area) is smaller and the space between the optical "channels" is increased. This is especially true at the corners of the cells. The tapered structure allows a smaller cross section to be formed in the secondary collimation layer, increasing the diameter of the light beam to preferably completely fill the adjacent lenses, which reduces the space left for the poles.

[0107] FIG. 1C shows the transparent circuit board 5 in isolation in square surface areas 13 corresponding to the square surface sections 11. Each square surface area 13 has an LED 15 at its central location. Note that no circuitry is shown in FIG. 1C, which will be explained in more detail later with respect to electrical and thermal conductors. As shown in FIG. 1B, pillars 9 with triangular cross sections are identified at the four corners.

[0108] Figure 1D shows a secondary collimation layer formed by a respective two-dimensional array of lenses 17 that essentially fill the associated square surface section 11. As in Figure 1B, pillars 9 with triangular cross-sections can be seen at the four corners, but considering the tapered basic shape, it can be seen that the cross-section of the pillars 9 has been reduced.

[0109] 2A-2D and 3A-3D are schematic diagrams of another exemplary light emitting module 1',1" based on a two-dimensional 5 row by 5 column array of optical cells having a square basic shape. FIGS. 2A and 3A show a cross section of a secondary collimation layer 7',7", respectively. FIGS. 2B and 3B are schematic cross sections taken along the section line where LEDs 15',15" are located to show a transparent circuit board 5',5" mounted on a reflective panel 3',3". As shown, LEDs 15',15" are centrally mounted relative to a cup-shaped recess in the reflective panel 3',3". As can be seen in FIG. 2B, reflective surface area 11A' transitions partially from one square basic shape to the next along the length of a side of the square basic shape. That is, FIG. In FIG. 2B, the diameter of the circular concave reflective surface area 11A' is smaller than the side length of the square surface section 11' (see FIG. 2C) (FIG. 2C is similar to the appearance of the reflective panel 3 shown in FIG. 1B). On the other hand, the imaginary diameter assumed for the concave reflective surface area 11A" in FIG. 3B is extended larger than the side length of the square surface section 11" (see FIG. 3C). This minimizes the thermal contact area 11B" between the four concave reflective surface areas 11A" so that it has a star-shaped shape (see FIG. 3C).

[0110] Figures 2D and 3D show, in a perspective view of the light emitting module 1', 1", a schematic representation of a secondary collimation layer 7', 7'' positioned at a distance several times the side length of the square surface section 11', 11'' from the reflective panel 3', 3'' / transparent circuit board 5', 5''.

[0111] 4 and 5 show typical example arrangements of the thermal contact areas relative to the mounting location of the LED (the focal location of the reflective surface area).

[0112] Figure 4A (lateral displacement of LEDs and square basic shape) and Figure 5A (diagonal displacement of LEDs and square basic shape) respectively show possible locations of thermal contact areas 21', 21" on a transparent circuit board used in a reflective panel as shown in Figures 2B and 3B. Specifically, Figure 4A shows one thermal contact area 21' between a pair of LEDs 15'. This configuration creates a line of alternating LEDs 15' and thermal contact areas 21'. The thermal contact area 21' is located along the side of the square surface section and is specifically thermally connected to a thermal contact area of ​​the reflective panel between a pair of adjacent concave reflective surface areas.

[0113] 4B shows how a line of LEDs 15' can be thermally connected in a linear fashion by passing a linear thermal conductor 23' (which can also be used, for example, as an electrical conductor) through the thermal contact area 21' between two LEDs 15'. As shown, multiple linear connections, for example of the same number of LEDs 15', can form a group of LEDs 15' that are powered in series.

[0114] Referring to FIG. 5A, thermal contact areas 21" are provided at the corners of the square surface section, thereby forming alternating rows of LEDs 15" and thermal contact areas 21". As shown in FIG. 5B, a thermal conductor 23" (which may also be used as an electrical conductor, for example) may thermally connect the line of LEDs 15" along a zigzag path. Alternatively, as shown in FIG. 5C, from a linear thermal conductor (thermal connector) 23' extending along the line of LEDs 15", additional thermal conductor segments (thermal connector segments) 23''' may thermally connect the linear thermal conductor 23' between the LEDs 15" to the thermal contact areas 21".

[0115] The following description of Figures 6-12 illustrates example configurations of thermal and / or electrical contact between the mounting locations of the LEDs and the thermal contact areas.

[0116] 6A and 6B show an example of a zigzag path thermal connection on the circuit board of the reflective panel shown in FIG. 3B. FIG. 6A shows star-shaped thermal contact areas 11B″ (these “diamonds” are the “flat tips” of the surface of the reflective panel) at the corners of a square surface section and an LED 15″ located in the center of the star-shaped thermal contact area 11B″. It can be seen that the thermal contact area 21″ (dotted part shown in FIG. 6B) of the circuit board is located on the star-shaped thermal contact area 11B″. Thus, the thermal conductor 23″ thermally connects each thermal contact area 21″ (and thus each star-shaped thermal contact area 11B″) to two LEDs 15″ by a zigzag path.

[0117] 7A and 7B show how LEDs are attached to the support substrate 23 of a transparent circuit board at their mounting positions. FIG. 7A shows LEDs 25 with a heat sink 27 attached to the support substrate 23 via a thermal conductor (in this case a thermally conductive layer 29). The large area thermal contact between the heat sink 27 and the thermally conductive layer 29 allows the removal of heat generated by the LEDs 25 during operation and the transfer of the heat to the thermal contacts to the reflective panel (not shown) via the thermally conductive layer 29. As shown in the following examples, the thermally conductive layer 29 may be configured as a thermal conductor (thin in lateral dimensions to block as little light as possible) or as an optically transparent diffusing layer, for example based on an ITO layer (indium tin oxide layer). Note that in FIG. 7A electrical connections are not shown, but are usually insulated from the thermally conductive layer 29.

[0118] 7B shows an embodiment in which an electrical circuit is also used to remove heat. Specifically, LEDs 31 are attached to the support substrate 23 at their respective mounting positions. The leads 33 of the LEDs 31 are connected to electrical conductors 35, so that heat generated by the LEDs 31 during operation is extracted and transferred to the electrical conductors 35 and then into thermal contact with the reflector panel. It will be understood that electrical insulation may be required between the electrical conductors 37 and the reflector panel (usually at ground potential), respectively.

[0119] 8A-8D show various configurations of circuits provided on the circuit board for thermally and optionally electrically contacting each LED 15. In the schematic bottom view, a circular light-transmitting area 41 surrounding the LED 15 and a thermal conductor 43 extending linearly through the light-transmitting area 41 can be seen. The thermal conductor 43 starts from the LED 15 and extends radially to ensure a minimum light blocking area. The thermal conductor 43 is connected to a thermal contact area 45. The thermal contact area 45 extends as a two-dimensional area to provide a large surface area for contacting the reflective panel. The illustrated configuration may be used only for heat removal (in which case additional electrical contacts must be provided to the LED 15) or the thermal conductor 43 may also be used to supply power to the LED 15. For ease of explanation, the light-transmitting area 41 is illustrated in white (non-colored) to distinguish it from the thermal contact area 45 (illustrated as a pattern) and the remaining area 47 (illustrated in gray). The remaining areas 47 may be left uncoated or may be specially used, for example, to implement additional power supply circuitry for the LEDs 15. Furthermore, the underlying reflective panel must provide a respective corresponding thermal contact area to ensure proper thermal contact with the thermal contact area 45 of the circuit board.

[0120] Returning to FIG. 8A, linear thermal (and, if necessary, electrical) connections of three LEDs 15 each forming three rows of LEDs are shown. In FIG. 8B, two rows of LEDs 15 are connected in one thermal (and, if necessary, electrical) connection. In the configurations of FIGS. 8C and 8D, the thermal contact areas 45 are offset from the linear arrangement of the LEDs so that a zigzag path of the thermal (and, if necessary, electrical) connections is implemented. The configuration of FIG. 8C relates to an embodiment in which the diameter of the light-transmitting areas 41 is smaller than the side length of the square surface section. In contrast, FIG. 8B relates to an embodiment in which the diameter of the light-transmitting areas 41 is slightly larger than the side length of the square surface section, resulting in the formation of star-shaped thermal contact areas 45 (see also FIGS. 6A and 6B).

[0121] FIG. 9 shows an approach for improving electrical contact of LEDs 15 (FIGS. 9A and 9B) mounted on a circuit board 49 and heat removal through a reflective panel 50, which can also be used for precision mounting of the reflective panel 50.

[0122] It should be noted that the thermal contact areas 45 are made as large as possible. To separate the different potentials of the thermal contact areas 45, FIG. 9B shows the remaining uncoated lines 51. The shaded areas in FIG. 9B may be conductive, so short circuits must be avoided. Transparent areas of the circuit board, such as the light-transmitting areas 41, are essentially electrically insulating. If the thermal contact areas 45 are used for power supply, adjacent thermal contact areas 45 are electrically connected only through the LEDs 15 surrounded by the insulating light-transmitting areas 41.

[0123] When using a circuit board 49 with an electrically conductive reflective panel, a thin insulating layer may be implemented, for example, to cover the circuitry. In another embodiment, the electrically insulating reflective panel may have metal coated areas, for example, to form concave reflective surface areas. As described further herein, the materials used for the reflective panel, circuit board, and secondary collimation layer may be specifically selected taking into consideration, for example, thermal expansion, alignment stability, use environment, shipping environment, etc.

[0124] Furthermore, Fig. 9A shows the circular reflective surface area (shown as a dashed circle) of the associated reflective panel. Fig. 9B shows the large area thermal (electrical) contact area 45, the thermal conductor 43, and the electrical circuit with the LED 15. In Fig. 9B, "+" indicates the function as an anode for the LED 15, and "-" indicates the function as a cathode for the LED 15.

[0125] 9C is a top view of an exemplary reflective panel 50 with a (e.g., metal coated) circular reflective surface area 53 (illustrated in white (non-colored)). The reflective panel 50 is used, for example, with the circuit board of FIG. 9A, which is in thermal contact with the reflective panel 50 at the peripheral thermal contact (surface) area 56. As an exemplary additional feature, FIG. 9C illustrates metal inserts 55 (illustratively shown only at the four corners of the square surface section) to increase the thermal conductivity of the reflective panel 50. It will be appreciated that electrical insulation is required for either the reflective panel 50 or the circuit board.

[0126] 9D shows how a reflective panel can be mounted within a light emitting module 61 using a metal insert 55. In this case, the metal insert 55 extends from a metal bottom portion 57, which acts as a heat sink for the light emitting module 61, to a predetermined location that ensures proper alignment of the reflective panel 50 with the light emitting module 61.

[0127] FIG. 10 shows a circuit board 63 that uses an ITO layer (indium tin oxide layer) to electrically connect the LEDs 15. As can be seen particularly in the enlarged view of FIG. 10B, alternating sections 65A, 65B of the ITO layer are in electrical contact with the LEDs and are therefore electrically insulated from each other via uncoated lines 51. Adjacent ITO layers are connected only through the LEDs. The ITO layer is optically transparent and can distribute the heat generated by the LEDs 15 over a large area so that it can be removed via a thermally connected reflective panel.

[0128] With regard to electrically insulating the circuit board 63 from the thermally connected reflective panel, FIG. 10C shows a thin dielectric insulating layer 67 applied (sprayed) on the outside of the light transmissive areas of the circuit board 63, over the thermal contact areas (here the ITO layer).

[0129] FIG. 11 shows a combination of thermal conductors and electrical conductors in a configuration of a circuit board 71 similar to that of FIG. 9A. As shown in FIG. 9A, the thermal connection of the LED 15 is realized laterally using the thermal conductor 73 and the thermal contact area 75. Furthermore, an electrical connection is realized orthogonal to the thermal connection (see the dashed line in FIG. 11A that runs along the non-coated area 77 of the circuit board 71 from one light-transmitting area to another light-transmitting area). In the enlarged view of FIG. 11B, an exemplary electrical conductor 79 is explicitly shown. For example, the thermal connector (thermal conductor 73) is configured to receive heat from the heat sink of the LED 15 (see the previous description regarding FIG. 7A), and the electrical conductor 79 is connected to the lead of the LED for power supply.

[0130] FIG. 12 shows another combination of thermal conductors and electrical conductors in a circuit board 81 configuration similar to that of FIG. 6A.

[0131] The embodiment of Figure 12A shows a zigzag path of thermal connection 82 of LED 15 with thermal contact area 83 of the circuit board and star-shaped thermal contact area 85 at the corner of a square surface section of a reflective panel (not shown). Additionally, LED 15 is linearly electrically connected through the light transmitting area (indicated by dashed line 87 in Figure 12A and electrical connector 89 in the enlarged view).

[0132] In the embodiment of FIG. 12B, the four thermal contact areas 83 of the circuit board are connected to the heat sink of the LED 15 with a cross-shaped arrangement of thermal conductors (thermal connections 82), while the power supply is realized along a linear electrical connection (dotted line 87 in FIG. 12B).

[0133] The light emitting modules disclosed herein can be combined in a suitable manner to expand the light emitting surface of the directional light beam in a modular device. For example, Fig. 13A shows a schematic arrangement of three light emitting modules 91, and Fig. 14 shows an arrangement of six reflective panels 90A-90F arranged, for example, in a U-shape.

[0134] Referring to the embodiment shown in FIG. 13A, a frame 93 maintains multiple light emitting modules 91 precisely positioned relative to one another.

[0135] As already mentioned in the context of Fig. 9D, the thermally conductive insert 95 may penetrate the reflective panel to reach the circuit board, thereby improving heat removal from the transparent substrate through the reflective panel to the bottom surface. In the embodiment of Fig. 13A, the thermally conductive insert 95 is connected to the frame 93 (or part thereof). The thermally conductive insert 95 may further improve the mounting position of the light emitting modules 91 on the frame 93, in particular their positioning relative to each other.

[0136] 13B (modular device with orthogonal light emission) shows that in the case of a retroreflective configuration of the reflective panel, a ray of light reflected by one of the concave reflective surface areas passes through a single lens of the secondary collimation layer associated with the same (e.g. square or hexagonal) surface section. Thus, the output light 97 is directed orthogonally with respect to the reflective panel.

[0137] Alternatively, as shown in FIG. 13C (modular device with tilted light emission), the light ray reflected by one of the concave reflective surface areas may pass through a single lens of the secondary collimation layer associated with another (e.g. square or hexagonal) surface section. In the example of FIG. 13C, the light ray passes through the lens of the adjacent surface section. It can be seen that the tilt angle of the output light 99 depends on the position of the "pass lens" and the distance between the primary collimation layer (e.g. the reflector panel) and the secondary collimation layer (e.g. the lens panel). The tilt can be achieved, for example, by a mounting position of the LEDs that is laterally shifted with respect to the mounting position for the orthogonal light emission. It should be noted that several LED arrays may be arranged together on one circuit board, allowing the light emission direction to be changed by switching between the different LED arrays (or several LED arrays may be operated simultaneously to emit several light rays in different directions). The shift between the LED arrays depends on the pitch of the optical cells and / or the distance to the secondary collimation layer. Alternative configurations may be based on specially designed shapes such as inclined reflecting surfaces, which may be inclined with respect to the direction of the orthogonal light emission area shape. It will be understood that the modular approach imposes constraints on the inclination angle if it is intended to emit the output light at a certain angle. As mentioned above, the inclination angle is not arbitrarily selectable, but may be selected from a set of discrete inclination angles that allow the LED of one optical cell to illuminate the collimating lens from an adjacent optical cell (first inclination angle) or another optical cell further away. It should be noted that for optical cells at the boundary of light emitting modules, the LED of one light emitting module illuminates the collimating lens of another light emitting module.

[0138] Specifically, regarding the modular approach, a suitable approach for LED electrical wiring may be set, which may prevent contact points of different potentials from being close to each other. Specifically, the LEDs connected in series may be supplied with the same current, which allows each LED to emit the same light, improving the desired uniformity across the output aperture of the light-emitting module. Furthermore, the greater the number of LEDs, the smaller the effect of random resistance variations of different LEDs, so that each row may generate the same light emission individually. In some embodiments, adjacent light-emitting modules have the same potential on the connection side. For example, on one connection side, the two light-emitting modules on the left and right of the connection side are given a ground potential, and the other respective sides are maintained at an operating potential.

[0139] 15 is a schematic top view of a light emitting module 101 based on an arrangement of hexagonal optical cells, which are mounted on a reflector panel and a transparent circuit board, respectively. Hexagonal optical cells are found at the four corners, resulting in a basic shape of the light emitting module 101 being a parallelogram. Specifically, the heat transfer area 103 is shown as a vertical line, the circular reflective surface area 105 of the reflector panel is shown in black, and the transparent area 107 in the transparent circuit board extends over an area that includes at least the circular reflective surface area 105 shown in black and the surrounding ring (larger than the circular reflective surface area 105 considering the divergence and / or inclined output direction of the reflected light beam) shown in diagonal lines.

[0140] Although preferred embodiments of the present invention are described herein, improvements and modifications may be incorporated without departing from the scope of the appended claims.

Claims

1. A circuit board for a light emitting module, the circuit board includes a plurality of mounting locations for LEDs; the plurality of mounting locations are distributed on a first surface of the circuit board in a regular two-dimensional pattern; The circuit board includes: a plurality of transparent regions each extending around one of the plurality of mounting positions; a plurality of heat transfer areas each thermally and electrically connected to at least one of the mounting locations; an average area of ​​the plurality of heat conduction regions is 2% or more of an average area of ​​the plurality of transparent regions; each of the plurality of thermally conductive regions having at least a portion extending as a two-dimensional region on a surface of the circuit board; Circuit board.

2. The electrical resistivity (Ω·m) of the heat conduction region is 10 10 times smaller than the electrical resistivity of the transparent region. The circuit board according to claim 1 .

3. the heat conducting region is at least partially covered by an electrically insulating layer; The circuit board according to claim 1 or 2.

4. the thermally conductive region comprises a thermal connection extending across the transparent region; The circuit board according to claim 1 or 2.

5. The thermal connection part is made of an opaque material, and / or made of ITO material, and / or a substantially planar connector having a larger surface oriented at an angle relative to the first surface of the circuit board; The circuit board according to claim 4 .

6. the thermally conductive area covers at least 90% of the area of ​​the circuit board not associated with the transparent area; The circuit board according to claim 1 or 2.

7. The transparent region has a transparency of 75% or more relative to visible light. The circuit board according to claim 1 or 2.

8. The transparency of the transparent region is at least 10 times greater than the transparency of the heat conduction region. The circuit board according to claim 1 or 2.

9. further comprising a plurality of LEDs mounted on the circuit board at the plurality of mounting positions, the plurality of LEDs are configured to project light within a hemisphere bounded by the first surface; The circuit board according to claim 1 or 2.

10. each LED of the plurality of LEDs has a heat sink disposed in a central region of the respective transparent region of the plurality of transparent regions; the plurality of thermal conduction regions include a thermal conduction layer and a plurality of thermal connections each connecting one of the heat sinks to the thermal conduction layer in one of the thermal conduction regions; The circuit board according to claim 9.

11. the heat transfer area comprises a plurality of planar electrical connection sections defining a heat removal area of ​​the circuit board; The circuit board according to claim 1 or 2.

12. the planar electrical connection section extends outside the transparent area; the thermally conductive region further comprises a plurality of linear electrical connection sections extending across the transparent region to electrically and thermally connect the LEDs to the planar electrical connection sections; The circuit board according to claim 11.

13. the linear electrical connection section has a first thickness in a dimension perpendicular to a surface of the circuit board; the planar electrical connection section has a second thickness in a dimension perpendicular to the surface of the circuit board; The first thickness is greater than the second thickness. The circuit board according to claim 12.

14. A light emitting module comprising a reflective panel, a transparent circuit board, a plurality of LEDs, and a plurality of heat conductors, the reflective panel has an inner surface subdivided into a two-dimensional array of surface sections each having a shape that allows them to be combined to cover a continuous surface, each surface section having a concave reflective surface area and a thermal contact area outside the concave reflective surface area; the transparent circuit board is attached to the reflective panel such that a first surface of the transparent circuit board faces the inner surface of the reflective panel; the plurality of LEDs are distributed in a two-dimensional array on the first surface of the transparent circuit substrate such that each LED is associated with one of the concave reflective surface regions; each of the plurality of thermal conductors connects one of the LEDs to one of the thermal contact areas; During operation of the light emitting module, light emitted from one of the LEDs is reflected by the associated concave reflective surface area so as to pass through the transparent circuit board; The heat generated by the LED is dissipated through the thermal conductor and the thermal contact area. Light-emitting module.

15. Further comprising a lens arrangement spaced from the transparent circuit board at a distance of at least three times the length of one side of the surface section. The light emitting module according to claim 14.

16. In operation, light emitted from one of the LEDs is reflected by an associated one of the concave reflective surface areas to pass through the transparent circuit board and is collimated by one of the lenses of the lens arrangement. The light emitting module according to claim 15.

17. 1. An LED-based optical system comprising: a support substrate having a plurality of mounting locations; a plurality of light sources attached to the support substrate at the plurality of mounting positions; a reflective panel having a three-dimensional surface and attached to the support substrate; a plurality of conductive paths extending along a first surface of the support substrate; the plurality of mounting locations are distributed in a regular two-dimensional pattern on the first surface of the support substrate; the support substrate is transparent to visible light in at least a plurality of transmissive regions, each of the transmissive regions extending around one of the plurality of mounting locations; the regular two-dimensional pattern is formed so that the distance between adjacent mounting positions in a predetermined direction is equidistant, Each of the light sources includes at least one LED; the three-dimensionally shaped surface of the reflective panel faces the first surface of the support substrate and includes a plurality of contact surface sections and a plurality of reflective surface sections; the plurality of contact surface sections extend within a connecting surface and contact the first surface of the support substrate; each of the reflective surface sections faces a corresponding one of the transmissive regions of the support substrate; the plurality of conductive paths are configured to dissipate heat from the light source and / or provide power to the light source; At least one of the conductive paths extends from one of the mounting locations to at least one of the contact surface sections. optical system.

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