Patent Publication Number: US-2022214493-A1

Title: Low z-height led arrays with controllable light beams

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/584,641 filed Sep. 26, 2019, which claims benefit of priority to U.S. Provisional Patent Application No. 62/738,607 filed Sep. 28, 2018 and to European Patent Application No. 18211515.4 filed Dec. 11, 2018. Each of the applications identified in this paragraph is incorporated herein by reference in its entirety. 
     This application is also related to U.S. patent application Ser. No. 16/584,628 filed Sep. 26, 2019 and to U.S. patent application Ser. No. 16/584,635 filed Sep. 26, 2019. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to LED lighting systems. In certain embodiments, flexible low Z-height LED arrays having multiple light beam capability are described. 
     BACKGROUND 
     Ceiling or surface mounted area light panels suitable for home, retail, office, or architectural installation are widely available. Such systems often include large fluorescent tubes or multiple halogen lights positioned several centimeters distant from a light diffuser panel. While suitable for many applications, such lighting systems require a substantial Z-height, are ill suited for providing beam lighting that can specifically highlight a selected area, and are not able to easily limit light intensity provided to a selected area. 
     To alleviate such deficiencies, multiple LED directed lighting systems capable of providing multiple beams of a light can be used. Unfortunately, such directed lighting systems do not provide a relatively uniform appearance, with multiple LEDs and optics can provide an unsatisfactory cluttered appearance. Typically, the LED package appearance and projected light of such LED systems is not uniform, with bright spots and shadowing being present in the LED package, and individual projected beams being recognizable in illuminated areas. Further, due to separated light beams, illuminated objects will appear to have multiple shadows in response to direct illumination. LED systems that have a low Z-height, present a uniform visual appearance, and minimize shadowing or other visual artifacts of multiple beams are needed. 
     SUMMARY 
     In one embodiment, a light source useful for architectural lighting, general lighting, street lighting, or other lighting applications includes a plurality of light emitting diodes. A least some light emitting diodes can be sized between 30 microns and 500 microns. A plurality of micro-optics sized less than 1 millimeter are positioned over at least some of the plurality of light emitting diodes. At least some of the plurality of micro-optics are grouped to provide at least two directional light beams and a controller is connected to selectively power groups of the plurality of light emitting diodes to provide different light beam patterns. 
     In one embodiment a flexible substrate is positioned to support the plurality of light emitting diodes and the plurality of micro-optics, with the flexible substrate bendable to allow differing directionality of light beams. In an alternative embodiment a flexible light guide plate defines the plurality of micro-optics and is positionable over at least some of the plurality of light emitting diodes. 
     In one embodiment, a plurality of light emitting diodes are attached or positioned near a light guide plate. At least some light emitting diodes are sized between 30 microns and 500 microns and can be attached to a printed circuit board or other suitable substrate. A plurality of micro-optics can be associated with a light guide plate and are sized less than 1 millimeter, with each micro-optic positioned over at least one of the plurality of light emitting diodes. The combined height of each of the plurality of light emitting diodes, their supporting substrate, and associated micro-optics is less than 1 centimeter. In some embodiments, at least some of the combinations of light emitting diodes and micro-optics associated with the light guide plate are positioned within a distance to each other sufficient to provide at least one substantially uniform light beam. 
     Optical structures can include a plurality of micro-optics defined or attached to the light guide plate and sized less than 1 millimeter. The micro-optics can be positioned over at least one of the plurality of light emitting diodes. Typically, the micro-optics are sized to be similar or larger in size than the light emitting diodes. In some embodiments, each combination of light emitting diode and associated micro-optic can be positioned within a distance to each other sufficient to both present a substantially uniform visual appearance and provide a substantially uniform light beam. This distance can be selected so the combined light emitting diode and associated micro-optic are positioned to be separated by no more than a Rayleigh limit distance calculated for a user at a normal distance from the light source. In some embodiments, each of the plurality of light emitting diodes are positioned at least 1 millimeter apart. 
     In some embodiments a controller is connected to selectively power groups of the plurality of light emitting diodes to provide different light beam patterns. 
     In some embodiments the height of the light emitting diodes, their supporting substrate and electrical traces, and associated micro-optics is less than 5 millimeters. 
     In some embodiments light emitting diodes can be embedded in a solid or a flexible substrate, which can be at least in part transparent. For example, the light emitting diodes can be at least partially embedded in glass, ceramic, or polymeric materials. At least some of the plurality of light emitting diodes can be individually controlled through connected electrical traces. In other embodiments, groups or sub-groups of light emitting diodes can be controlled together. 
     In some embodiments the plurality of light emitting diodes can have distinct non-white colors. For example, at least four of the plurality of light emitting diodes can be RGBY groupings of light emitting diodes. 
     In another embodiment, at least two of the plurality of light emitting diodes are positionable under a single micro-optic. Alternatively, each light emitting diodes can be positioned under a single micro-optic. Some of the plurality of light emitting diodes can be positioned under a single on-axis micro-optic, while others can be positioned under a single off-axis micro-optic. In some embodiments the micro-optics are defined in an optical sheet positionable over at least some of the plurality of light emitting diodes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a diagram illustrating a LED illumination system with multiple millimeter-scale spaced apart LEDs and micro-optics supported by a substrate; 
         FIG. 1B  is a diagram illustrating a Rayleigh distance separation of millimeter-scale spaced apart LEDs and micro-optics; 
         FIG. 1C  is a diagram illustrating a low Z-height LED illumination system with multiple millimeter-scale spaced apart LEDs and micro-optics supported by a substrate; 
         FIG. 2  illustrates a light guide plate with attached multiple millimeter-scale spaced apart LEDs and various micro-optics; 
         FIG. 3  illustrates a light guide plate with surface or cavity attached multiple millimeter-scale spaced apart LEDs; and 
         FIGS. 4A and 4B  illustrates in respective side and top view a LED illumination system with multiple millimeter-scale spaced apart LEDs and an overlaying glare shield. 
         FIG. 5  illustrates multiple millimeter-scale spaced apart LEDs and micro-optics with both on-axis and off-axis associated micro-optics; 
         FIG. 6  illustrates multiple millimeter-scale spaced apart LEDs with associated micro-optics, arranged to have non-symmetric, irregular spacing; 
         FIG. 7  illustrates multiple millimeter-scale spaced apart LEDs embedded in a substrate, with an overlaying continuous optical plate including aspheric optics; 
         FIG. 8  illustrates multiple millimeter-scale spaced apart LEDs embedded in a flexible substrate; 
         FIG. 9  is a top view illustrating two dimensional LED layout with filled areas, linear features, and regular and irregular curves; and 
         FIG. 10  illustrates a process for manufacture and calibration of multiple millimeter-scale spaced apart LEDs with associated micro-optics. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  is a diagram illustrating a LED illumination system  100  with multiple millimeter-scale spaced-apart LEDs  120  that form a sparse array and associated micro-optics  130  supported by a substrate  110 . LED activation and light intensity can be controlled by controller  140 . Light emitted from LEDs  120  follow light beam paths  150 . The light beam paths can be substantially distinct or at least partially overlapping as indicated in  FIG. 1 . In some embodiments, the light beams can be used to illuminate a light diffuser panel. In other embodiments to be discussed with respect to  FIG. 5 , the LEDs  120  can be used to direct light into a light guide plate. 
     In some embodiments, at least some LEDs  120  are sized between 30 microns and 500 microns in length, width, and height. The micro-optics  130  are sized to be less than 1 millimeter in length, width, and height and are positioned over at least some of the LEDs  120 . Typically, the micro-optics are sized to be similar or larger in size than the LEDs  120 . In some embodiments the height of the LEDs  120 , their supporting substrate and any electrical traces, and associated micro-optics  130  is less than 5 millimeters in combination. 
     The controller  140  is connected to selectively power groups LEDS  120  to provide different light beam patterns  150 . The controller  140  can be mounted on, beneath, or adjacent to substrate  110 . Alternatively, the controller can be mounted separately from the substrate  110  and use wired connections, board connected electrical traces, or another suitable interconnect mechanism. The LED controller  140  can include necessary circuitry so as to enable the operation of the plurality of LEDs  120 . The LED controller can be unitary or be composed of multiple distinct modules in wired or wireless interconnection. For example, the LED controller  140  can include a separate power supply, a wireless interconnect, and remote logic on a dedicated light interface device or app supported by a smartphone. 
     The substrate  110  can include a laminated printed circuit board, a ceramic board, glass board, or plastic board. The substrate can be rigid or flexible. Furthermore, the substrate  110  can include the necessary traces and circuitry to enable individual or grouped operation of the LEDs  120 . Electrical connection between controller  140  and LEDs  120  can be formed by direct wiring, electrical trace layout, side or bottom vias, or suitable combinations thereof. In certain embodiments, transparent conductors such as indium tin oxide (ITO) can be used to form top or side contacts. 
     In some embodiments, each LED can be separately controlled by controller  140 , while in other embodiments groups of LEDs can be controlled as a block. In still other embodiments, both single LEDs and groups of LEDs can be controlled. To reduce overall data management requirements, the controller  140  can be limited to on/off functionality or switching between relatively few light intensity levels. In other embodiments, continuous changes in lighting intensity are supported. Both individual and group level control of light intensity is contemplated. In one embodiment, overlapping or dynamically selected zones of control are also possible, with for example, overlapping groups of LEDs  120  being separately controllable despite having common LEDs depending on lighting requirements. In one embodiment, intensity can be separately controlled and adjusted by setting appropriate ramp times and pulse width for each LED using a pulse width modulation module within controller  140 . This allows staging of LED activation to reduce power fluctuations, and to provide superior luminous intensity control. 
     The LEDs  120  can include but are not limited to LEDs formed of sapphire or silicon carbide. The LEDs  120  can be formed from an epitaxially grown or deposited semiconductor n-layer. A semiconductor p-layer can then be sequentially grown or deposited on the n-layer, forming an active region at the junction between layers. Semiconductor materials capable of forming high-brightness light emitting devices can include, but are not limited to, Group III-V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials. In certain embodiment, laser light emitting elements can be used. 
     Color of emitted light from the LEDs  120  can be modified using a phosphor contained in glass, or as a pre-formed sintered ceramic phosphor, which can include one or more wavelength converting materials able to create white light or monochromatic light of other colors. All or only a portion of the light emitted by the LEDs  120  may be converted by the wavelength converting material of the phosphor. Unconverted light may be part of the final spectrum of light, though it need not be. Examples of common devices include a blue-emitting LED segment combined with a yellow-emitting phosphor, a blue-emitting LED segment combined with green- and red-emitting phosphors, a UV-emitting LED segment combined with blue- and yellow-emitting phosphors, and a UV-emitting LED segment combined with blue-, green-, and red-emitting phosphors. In some embodiments, individually controllable RGB (three LEDs) or RGBY (four LEDs) can be positioned under a single micro-optic. This allows for precise color control of emitted light. Typically, such RGB LEDs are spaced sufficiently far apart that color mixing will occur in the far field. 
     Direction, beam width, and beam shape of light emitted from each LED  120  can be modified by micro-optics  130 . Micro-optics  130  can be a single optical element or a multiple optic elements. Optical elements can include converging or diverging lenses, aspherical lens, Fresnel lens, or graded index lens, for example. Other optical elements such as mirrors, beam diffusers, filters, masks, apertures, collimators, or light waveguides are also included. Micro-optics  130  can be positioned at a distance from the LEDs that allows receipt and redirection of light from multiple LEDs  120 . Alternatively, micro-optics  130  can be set atop each LED  120  to individually guide, focus, or defocus emitted LED  120  light. Micro-optics  130  can be directly attached to the LEDs  120 , attached to LEDs  120  via a transparent interposer or plate, or held at a fixed distance from LEDs  120  by surrounding substrate attachments (not shown). 
     In one embodiment, LEDS are situated no further apart from each other than is necessary to present a substantially uniform visual appearance and provide a substantially uniform light beam. This requires that point-like sources be separated by distance that defines an angle smaller than the resolvable angular resolution for a user viewing at a normal distance (e.g. the distance from a standing or sitting user to light in a ceiling).  FIG. 1B  illustrates this with a graphic  160  illustrating a Rayleigh distance separation of millimeter-scale spaced apart LEDs and micro-optics. As seen in graph  160 , pairs of LEDs  162 ,  164 , and  166  are separated by an increasingly smaller distance. LEDs  162  are separated from each other by a distance and corresponding viewable angular separation at a distance (e.g. typically 1-2 meters) sufficient to distinguish each LED as a separate light source. A user looking at the LEDs would clearly see two distinct bright spots  182  having distinct dual light intensity peaks  172 . 
     Placing the LEDs closer together can eliminate the perception of distinct bright spots. LEDs  166  are so closely spaced that the individual light intensity peaks from each LED beam are combined into a single peak  176  that presents a generally uniform visual impression, with some slight brightening  186  in the center. 
     Placing the LEDs  164  at an intermediate distance determined to be a Rayleigh distance separation or smaller can provide light intensity peaks  174  that are basically indistinguishable, giving a generally uniform visual impression  184 . Rayleigh distance can be determined by considering diffraction through a circular aperture, which is: 
     
       
         
           
             θ 
             = 
             
               1.220 
               ⁢ 
               
                 λ 
                 D 
               
             
           
         
       
     
     where θ is the angular resolution (radians), λ is the wavelength of light, and D is the pupil diameter of a user viewing the separated LEDs. Determining the Rayleigh distance allows a further determination of LED spacing for a user viewing the LEDs at a distance typically between 1-2 meters distant. Typically, this LED separation distance will be 1 millimeter or less for sub-millimeter sized LEDs with associated micro-optics. In some embodiments, this distance can be increased by providing diffuser layers, wide beam optics, or mirror systems. Unfortunately, this reduces ease of manufacture and increases both the Z-height and expense of the LED systems. 
       FIG. 1C  is a diagram illustrating a low Z-height LED illumination system  190  with multiple millimeter-scale spaced apart LED units  192  formed from a combination of LEDs  194  and sheet embedded micro-optics  195 . The LEDs  194  are supported by a substrate  196  (e.g. a printed circuit board or ceramic substrate that supports electrical traces or vias) that has attached heat spreader fins  198 . The total Z-height  199  of the system is minimized, with a Z-height typically being less than 1 centimeter for millimeter or less sized LED sources. In some embodiments, Z-height for the LED illumination system  190  is set to be no greater than five (5) times the height of the LEDs  194 . 
     Low Z-height systems can support various light beam orientations. For example,  FIG. 2  illustrates an illumination system  200  with multiple millimeter-scale spaced apart LEDs  210  supported on a substrate  220 . The multiple millimeter-scale spaced apart LEDs can be symmetrically arranged in lines or arrays. Alternatively, they can be arranged to have non-symmetric, irregular spacing. Every LED  210 , or selected subgroups of LEDs  210 , can be spaced at a Rayleigh distance separation or smaller. One-dimensional, two-dimensional, and three-dimensional non-symmetric or irregular layouts of LEDs with associated micro-optics is contemplated. Two-dimensional layouts can be constructed from adjacent or contiguous positioning of one-dimensional substrates. Three-dimensional layouts can be constructed from multiple stacked layers of two-dimensional substrates. Stacked substrates can be transparent, or include defined apertures offset from supported LEDs to permit exit of light from lower layers. In other embodiments, symmetrical one-dimensional, two-dimensional, and/or three-dimensional arrays of LEDs can be used, as well as combinations of symmetrical and non-symmetrical layouts. 
       FIG. 2  also illustrates a light guide plate  230  formed to include optics or other light modification structures positioned near or adjacent to each of the LEDs  210 . Optical structures can be defined by embossing, etching, or additive emplacement on one or both sides of the light guide plate. For example, circular cavities  232  or pyramidal cavities  234  can be defined on one side, with additively manufactured lens provided on the opposing side. Additionally, dots can be printed, lines scratched, or cavities etched to affect light exit from the light guide plate  230 . 
       FIG. 3  illustrates another embodiment of a low Z-height light guide plate system  300  in which LEDS  310  are attached directly to a light guide plate surface ( 336 ) or attached wholly ( 332 ) or partially ( 334 ) within a defined cavity in a light guide plate  330 . Every LED  310 , or selected subgroups of LEDs  310 , can be spaced at a Rayleigh distance separation or smaller. In some embodiments, the light guide plate has a thickness from 50 to 100 microns, 100 to 500 microns, 0.5 to 1 mm, 1 mm to 5 mm, or 5 mm to 10 mm. In certain embodiments, LEDs  310  have a width from 30 microns to 500 microns. In other embodiments, LEDs  310  have a width and/or length from 5 to 10 μm, 10 to 50 μm, or 50 to 500 μm. In certain embodiments, each of the LEDs  310  has with a height from 2 to 10 μm, 10 to 200 μm, or 200 to 500 μm. 
     Attachment methods may include adhesive attachment. In some embodiments, pick and place machines can be used to individually position LEDs  310 . In other embodiments, transfer forms or tacky sheets can be used to transfer multiple LEDs at the same time. In those embodiments including cavity attachment sites, numbers of LEDs can be placed and mechanically shaken on the light guide plate until the LEDs drop into suitable cavities. As other examples, elastomer stamps or electrostatic stamp (or other transfer device), can be used for pick-up and transport to a light guide plate. In some embodiments this process can be performed in in parallel, with dozens to hundreds LEDs transferred in a single pick-up-and-print operation. 
     LED power and control can be provided by applied conductive traces that are connected to suitable control and power circuitry. The conductive traces can be formed from conductive inks, conductive polymers, solder, conducting graphene, or other suitable material that can be lithographically or directly printed, or applied by stamping, or other suitable application method. 
       FIGS. 4A and 4B  respectively illustrate in side ( FIG. 4A ) and top view ( FIG. 4B ) another embodiment  400 . A low profile glare reduction structure  450  is situated over LEDs  410  that are attached to a substrate  420 . Shields can be formed from a light blocking or reflective material the limits glare by reducing off-axis light beams. Every LED  210 , or selected subgroups of LEDs  210 , can be spaced at a Rayleigh distance separation or smaller. 
       FIG. 5  illustrates an illumination system  500  with multiple millimeter-scale spaced apart LEDs  520  and micro-optics  530  with both on-axis (e.g. micro-optic  532 ) and off-axis (e.g. micro-optic  532 ) associated micro-optics. 
       FIG. 6  illustrates an illumination system  600  with multiple millimeter-scale spaced apart LEDs  320  with associated micro-optics  330 , arranged to have non-symmetric, irregular spacing. One-dimensional, two-dimensional, and three-dimensional non-symmetric or irregular layouts of LEDs  620  with associated micro-optics  630  is contemplated. Two-dimensional layouts can be constructed from adjacent or contiguous positioning of one-dimensional substrates. Three-dimensional layouts can be constructed from multiple stacked layers of two-dimensional substrates. Stacked substrates can be transparent, or include defined apertures offset from supported LEDs  620  to permit exit of light from lower layers. In other embodiments, symmetrical one-dimensional, two-dimensional, and/or three-dimensional arrays of LEDs  320  can be used, as well as combinations of symmetrical and non-symmetrical layouts. 
       FIG. 7  illustrates an illumination system  700  with multiple millimeter-scale spaced apart LEDs  720  embedded in a substrate  710 , with an overlaying continuous optical plate  720  including aspheric optics. LEDs  720  can be positioned by a pick and place machine or other suitable carrier in multiple holes defined in substrate  410 , Alternatively, epoxy, thermoset plastics, plastic molds, or similar substrates can be defined around LEDs  420  held in position. The plate  720  can be adhesively attached to the substrate  710 . The plate can include on or off-axis micro-optics, or irregular aspheric micro-optics as shown. In certain embodiments, spherical optics can be used. 
       FIG. 8  illustrates an illumination system  800  with multiple millimeter-scale spaced apart LEDs  520  embedded in a transparent, flexible substrate  810 . Micro-optics  830  can be attached to the substrate  810 . This design is of particular use for architectural applications that require corner or curved surface mounting. 
       FIG. 9  is a top view illustrating two dimensional LED layout with filled areas, linear features, and regular and irregular curves. For example, feature  960  is a narrow linear structure supporting a one-dimensional array of LEDs, while feature  962  supports a curved one-dimensional array of LEDs. Feature  964  is a two-dimensional array (which can be radially symmetric as shown). Alternatively, rectangular, clumped, spiral, or other layouts are supported. Feature  966  can be an irregular shaped curve. 
       FIG. 10  illustrates a process  1000  for manufacture and calibration of multiple millimeter-scale spaced apart LEDs with associated micro-optics. In a first step  1010  are positioned with respect to a supporting substrate. A pick and place machine or other suitable device for holding and positioning hundreds or thousands of LEDs can be used. In step  1020 , connecting traces are attached to the LEDs to allow later attachment to a controller. In step  1030 , micro-optics are attached. In step  1040 , calibration of intensity and light beam width/direction is conducted to correct for non-operating LEDs or misaligned micro-optics. 
     The disclosed low Z-height systems can be used in various lighting applications. For example, downlights able to provide 1,500 lumens can be constructed with 300 mini LEDs of 0.2×0.2 mm and further being 25 d with 1.1 mm optic height. The specific light pattern can take any shape including line, square, or open circle. In another application, spotlights that are track mounted or ceiling recessed can be constructed to provide 1,500 lm with 300 mini LEDs of 0.2×0.2 mm and further being 15 d with 2.0 mm optic height. An optional 2 mm high glare shield can also be used. Such lights can be embedded in the track system or can become part of a suspended light system. In still another embodiment, high intensity stadium lights able to provide 10,000 lm units can be constructed from 1,250 LEDs/unit. Even such powerful lighting systems will only require a 2.0 mm optic height. Mobile lighting applications are also supported. For example, a camera flash system can be designed to use 100 LEDs sized from 0.1 to 0.2 mm. The LEDs can be of one or more colors, and can be arranged to be selectively activated to provide a required flash light intensity at a desired color temperature. 
     Programmable light emitting arrays such as disclosed herein may also support a wide range of applications that benefit from fine-grained intensity, spatial, and temporal control of light distribution. This may include, but is not limited to, precise spatial patterning of emitted light from blocks or individual LEDs. Depending on the application, emitted light may be spectrally distinct, adaptive over time, and/or environmentally responsive. In some embodiments, the light emitting arrays may provide pre-programmed light distribution in various intensity, spatial, or temporal patterns. The emitted light may be based at least in part on received sensor data and may be used for optical wireless communications. Associated optics may be distinct at single or multiple LED level. An example light emitting array may include a device having a commonly controlled central block of high intensity LEDS with an associated common optic, whereas edge positioned LEDs may have individual optics. Common applications supported by light emitting LED arrays include camera or video lighting, architectural and area illumination, and street lighting. 
     Programmable light emitting arrays may be used to selectively and adaptively illuminate buildings or areas for improved visual display or to reduce lighting costs. In addition, light emitting arrays may be used to project media facades for decorative motion or video effects. In conjunction with tracking sensors and/or cameras, selective illumination of areas around pedestrians may be possible. Spectrally distinct LEDs may be used to adjust the color temperature of lighting, as well as support wavelength specific horticultural illumination. 
     Street lighting is an important application that may greatly benefit from use of programmable light emitting arrays. A single type of light emitting array may be used to mimic various street light types, allowing, for example, switching between a Type I linear street light and a Type IV semicircular street light by appropriate activation or deactivation of selected LEDs. In addition, street lighting costs may be lowered by adjusting light beam intensity or distribution according to environmental conditions or time of use. For example, light intensity and area of distribution may be reduced when pedestrians are not present. If LEDs are spectrally distinct, the color temperature of the light may be adjusted according to respective daylight, twilight, or night conditions. 
     Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims. It is also understood that other embodiments of this invention may be practiced in the absence of an element/step not specifically disclosed herein.