Systems and methods for bright field illumination sheet-based variable illumination output

Abstract

To provide a high efficiency lighting system that is suppressed in glare, is flexible, delivers light to a place where the light is needed, has a suitable spectral distribution, and can provide effective light intensity levels.SOLUTION: A dynamic directional LEDs (or other kinds of solid-state light sources) sheet is positioned under each lenslet of a microlens array. Individual LED beam pointing direction depends on off-axis position relative to an optical axis of the lenslet. Individual beams from independent LEDs form illumination pixels at the illumination plane or within a volume space and can be modulated in intensity. Illumination pixels partially overlap in far-field illumination plane and illumination volume. Over a large illumination space, many illumination pixels are partially superimposed on neighboring illumination pixels, the amount of overlap being smaller than the size of a pixel. The LEDs can be digitally turned on or off and / or pulse width or amplitude modulated. Thus, far-field illumination patterns or light field distributions with spectral efficiency and efficacious intensity can be produced.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE INVENTION This application relates generally to illumination, and more particularly to systems and methods for bright field illumination sheet-based variable illumination output. [Background technology]

[0002] Electric lighting is the most common form of artificial lighting in industrial societies and is essential for enabling activities after sunset and in environments where natural light is insufficient. As such, it accounts for a large portion of electricity consumption. According to one estimate, lighting will account for 12% of electricity consumption in the commercial sector in 2020. When considering electricity consumption, the efficiency, convenience, and cost of lighting systems are particularly important. Therefore, lighting application efficiency is a key focus for promoting future energy conservation in lighting.

[0003] However, currently, electric lighting, especially commercial electric lighting, is rather inefficient. For example, commercial lighting is non-adjustable and provides floodlighting, which covers areas where lighting is not needed, wasting electricity.

[0004] Current solutions for improving the luminaire application efficacy (LAE) of lighting systems, especially commercial lighting systems, have proven inadequate due to insufficient efficiency, difficulty in directing light in desired directions and avoiding unwanted areas, failure to provide the most effective spectral distribution for human vision, failure to provide effective light intensity for a particular environment, or price. For example, commercial lighting sources typically utilize solid-state (SSL) light sources, i.e., semiconductor light-emitting diodes (LEDs), polymer light-emitting diodes (PLEDs), or organic light-emitting diode (OLED) light sources. However, conventional solid-state (SSL) light sources are thick and heavy, require expensive insulation and drilling holes in the ceiling where they are installed, are not customizable (limited to protruding placements), and are not bendable due to significant thermal cooling requirements. Therefore, the placement of these lighting systems is limited.

[0005] Thin lighting sheets (thin, flexible sheets with LEDs or OLEDs attached) eliminate the placement and maintenance issues of some conventional SSL light sources. However, existing thin lighting sheets are not adjustable—that is, they can only provide the same amount of light in the same direction unless moved. They also have other problems. For example, when organic light-emitting diodes (OLEDs) are used in thin lighting sheets, the lighting sheets tend to be expensive, less efficient and reliable, and lack the ability to incorporate sensors (or other electronic devices) and to customize the shape inexpensively. Similarly, thin lighting sheets sold by NthDegree Technologies Worldwide, Inc. of Tampa, Arizona, USA, do not fully utilize the LED lighting within the sheet. Furthermore, they are likely to produce light spots or bright spots, which are unsightly.

[0006] Additionally, Edge-Lit™ light guides sold by Fusion® Optics attempt to address the inefficiencies of lighting systems, but the guides are bulky, offer limited spatial control, and cannot accommodate sensors or other electronic devices.

[0007] Finally, the Hero™ luminaire, sold by Glint Photonics, Inc. of Burlingame, California, USA, offers a fixed position and orientation while allowing the light direction to be adjusted with a joystick. However, such luminaires suffer from high glare and require moving mechanical parts to redirect the light. Variable projection light sources sold by Lumileds Holding BV of Schiphol, The Netherlands, also suffer from high glare.

[0008] Therefore, there is a need for a highly efficient lighting system that reduces glare, is flexible, directs light where it is needed, has a favorable spectral distribution, provides effective light intensity levels, and is easily customizable. Summary of the Invention

[0009] A digitally controlled LED lighting sheet is provided that generates a far-field illumination pattern or bright-field distribution and improves light utilization. This variable-directivity solid-state lighting sheet utilizes LEDs (or other types of solid-state light sources) positioned under each lenslet in a microlens array. The light beam direction of each LED depends on the off-axis position of the lenslet relative to the optical axis. Individual light beams from each LED form illumination pixels at the illumination surface or within the volume, with variable intensity. The illumination pixels overlap at the far-field illumination surface and illumination volume. Over a large illumination volume, many illumination pixels overlap adjacent illumination pixels. The amount of overlap is much smaller than the size of the illumination pixel. The LEDs are digitally turned on or off and / or pulse-width or amplitude modulated. This allows for the creation of digitally controlled far-field illumination patterns or bright-field distributions. The LEDs and lenslets are closely spaced so that, at normal viewing distances, the illumination appears as a diffuse, continuous pattern rather than a pattern of individual bright spots. This characteristic contributes to glare suppression. The LEDs can also have different spectral characteristics from each other. Therefore, turning on specific LEDs at different levels of intensity allows for tuning of the spectral power distribution of the illumination.

[0010] In one embodiment, a light-emitting diode illumination sheet assembly is provided, the sheeting comprising: a microlens array including a plurality of lenslets; an array of light-emitting diodes (LEDs) aligned with each of the lenslets, wherein at least some of the LEDs in each array are positioned relative to an optical axis of the lenslet with which the array is aligned and at a different position relative to the optical axis of the lenslet with which at least one of the remaining LEDs in the array is aligned; and a computer including at least one processor controlling each of the LED light sources, the computer configured to: obtain at least one of a desired far-field illumination pattern and a desired bright-field distribution; identify, based on angles relative to the LED light sources, which LED light sources need to be turned on to generate at least one of the desired far-field illumination pattern and the desired bright-field distribution; and control the identified LED light sources to generate at least one of the desired far-field illumination pattern and the desired bright-field distribution.

[0011] In a further embodiment, a method for controlling a light-emitting diode illumination sheet assembly is provided. Data related to the light-emitting sheet assembly is obtained. The light-emitting sheet assembly includes a plurality of lenslets, and the light-emitting sheet assembly further includes a microlens array of light-emitting diodes (LEDs) aligned with each of the lenslets, wherein at least a portion of the LEDs in one or more of the arrays are positioned off-axis with respect to the optical axis of the lenslet with which the array is aligned and at a position relative to the optical axis different from a position at which at least one of the remaining LEDs in the array is positioned. At least one of a desired far-field illumination pattern and a desired bright-field distribution is obtained. Based on angles associated with the LED light sources, LED light sources that need to be turned on to generate at least one of the desired far-field illumination pattern and the desired bright-field distribution are identified. The identified LED light sources are controlled to generate at least one of the desired far-field illumination pattern and the desired bright-field distribution.

[0012] Still other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description, which describes embodiments of the present invention by illustrating the best mode contemplated for carrying out the invention. As will be realized, the present invention is capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature, and not restrictive. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 illustrates a system 10 for bright field illumination sheet-based variable illumination output, according to one embodiment. [Figure 2A] FIG. 1 shows two groups of arrays according to two embodiments. [Figure 2B] FIG. 1 shows two groups of arrays according to two embodiments. [Figure 3A] FIG. 2 shows a front view (side facing lenslets) and a back view (side facing LEDs) of a conical reflective honeycomb-shaped spacer 25, according to one embodiment. [Figure 3B] FIG. 2 shows a front view (side facing lenslets) and a back view (side facing LEDs) of a conical reflective honeycomb-shaped spacer 25, according to one embodiment. [Figure 4] FIG. 10 is a diagram showing a directivity angle and a divergence angle. [Figure 5A] 10 illustrates several different illumination patterns that are generated with overlapping illumination pixels. [Figure 5B] 10 illustrates several different illumination patterns that are generated with overlapping illumination pixels. [Figure 5C] 10 illustrates several different illumination patterns that are generated with overlapping illumination pixels. [Figure 5D] 10 illustrates several different illumination patterns that are generated with overlapping illumination pixels. [Figure 5E]10 illustrates several different illumination patterns that are generated with overlapping illumination pixels. [Figure 5F] 10 illustrates several different illumination patterns that are generated with overlapping illumination pixels. [Figure 6A] FIG. 10 shows the ray paths generated in a small section of a sheet when all LEDs in that section are turned on. [Figure 6B] FIG. 10 shows the ray paths generated when only the on-axis LED is on in a small area of ​​the sheet. [Figure 6C] FIG. 10 shows the ray paths generated in a small area of ​​the sheet when only the off-axis LEDs in that area are on. [Figure 6D] FIG. 10 shows the ray paths generated in a small area of ​​the sheet when only the off-axis LEDs in that area are on. [Figure 6E] FIG. 10 shows the far-field ray paths produced when all LEDs are on in a small section of the sheet. [Figure 6F] FIG. 10 shows the far-field ray paths produced when all LEDs are on in a small section of the sheet. [Figure 6H] FIG. 10 shows the far-field ray paths generated by off-axis LEDs in a small area of ​​a sheet. [Figure 6I] FIG. 10 is a diagram of a ray path with the presence of a low level of artifacts created by small areas of the sheet. [Figure 7] 1 shows an example of conventional light control (prior art) that has high glare and requires the use of moving mechanical parts. [Figure 8] 1 shows an example of light shifting (prior art) which has high glare and requires the use of moving mechanical parts. [Figure 9] 9 is a diagram of a variable lighting sheet that can be achieved using the system with improved light application efficiency (LAE) compared to the techniques illustrated in Figures 7 and 8. No moving parts are involved and glare is suppressed. [Figure 10] 1 shows a close-up view of an illumination sheet including spacers and a rear reflector, with LEDs integrated into the LED plane, according to one embodiment. [Figure 11] 11 shows the illumination sheet of FIG. 10 with the LEDs emitting light. [Figure 12A] 10 shows a simulated illumination pattern achieved using three illumination sheet tiles containing conical reflective honeycomb-shaped spacers. [Figure 12B] 10 shows a simulated illumination pattern achieved using three illumination sheet tiles containing conical reflective honeycomb-shaped spacers. [Figure 13A] 1 shows a simulated pattern tuned for human visual luminance perception achieved using three illumination sheet tiles including conical reflective honeycomb-shaped spacers and a rear reflector. [Figure 13B] 1 shows a simulated pattern tuned for human visual luminance perception achieved using three illumination sheet tiles including conical reflective honeycomb-shaped spacers and a rear reflector. [Figure 14] FIG. 1 is a flow diagram illustrating a method for bright field illumination sheet-based variable illumination control, according to one embodiment. [Figure 15A] FIG. 10 illustrates details of a particular lighting sheet tile used in the lighting simulation. [Figure 15B] FIG. 10 illustrates details of a particular lighting sheet tile used in the lighting simulation. [Figure 16A] 15A and 15B show simulated lighting patterns achievable with the three lighting sheet tiles of FIGS. 15A and 15B. [Figure 16B] 15A and 15B show simulated lighting patterns achievable with the three lighting sheet tiles of FIGS. 15A and 15B. [Figure 17A] Figure 17A shows simulated patterns adjusted to human visual brightness perception achieved when all light sources on the sheet are turned on, and when only a subset of the light sources required to generate the checkerboard pattern are turned on (Figure 17B). [Figure 17B]Figure 17A shows simulated patterns adjusted to human visual brightness perception achieved when all light sources on the sheet are turned on, and when only a subset of the light sources required to generate the checkerboard pattern are turned on (Figure 17B). [Figure 18] FIG. 10 illustrates light rays from a light source pointing towards an off-axis lenslet, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Improved control over light distribution can be achieved by combining a microlens array with a computer-controlled LED array. FIG. 1 illustrates a system 10 for brightfield sheet-based variable illumination output, according to one embodiment. The system 10 includes a brightfield sheet 30 (also referred to below as an illumination sheet 30 and an illumination sheet-based illumination tile 30). The sheet includes a microlens array 11 that includes a plurality of microlenses 12 (also referred to below as lenslets 12). The microlens array 11 can include different types of lenslets 12 or a combination of different types of lenslets 12. The lenslets 12 can be refractive elements, Fresnel elements, off-axis elements, holographic optical elements, diffractive optical elements, and reflective optical elements. However, other types of lenslets 12 can also be used.

[0015] An array 13 of solid-state light sources 14 is aligned with each of the lenslets 12. Each of the solid-state light source arrays 13 is positioned below one of the lenslets 12, with respect to the orientation shown with reference to FIG. 1 . In the following description, the solid-state light source array 13 is referred to as an LED array 13. In further embodiments, solid-state light sources 13 other than LEDs, such as PLEDs or OLEDs, can be used in the array 13. In yet other embodiments, different types of solid-state light sources 14 can be incorporated into the same array 13. In yet other embodiments, arrays 13 with different types of solid-state light sources 14 can be aligned with different lenslets 12 in the microlens array 11. In one embodiment, the lenslets 12 can be approximately hemispherical, but can also be other shapes. For example, the lenslets 12 can be spherical, aspherical, cylindrical, non-cylindrical, annular, aspherical annular, or freeform surface. However, the lenslets 12 can have other shapes. The light sources 14 can each have different spectral characteristics. The spectral characteristic differences may include differences in spectral radiation bandwidth, spectral peak wavelength, and spectral power distribution, although other spectral characteristics may also be present. In one embodiment, light sources 14 within the same array 13 may have the same spectral characteristics. Thus, spectral characteristic differences may exist only between light sources 14 in different arrays. In a further embodiment, light sources 14 within the same array 13 may also have the spectral characteristic differences. In yet a further embodiment, while spectral characteristic differences exist between light sources 14 within the same array 13, each array 13 may include light sources 14 with the same spectral characteristics as those in another array 13. The spectral characteristic differences between light sources 14 allow the spectral intensity distribution of illumination by system 10 to be digitally controlled by turning on particular lights at different levels of intensity, thereby improving lighting application efficiency.

[0016] The LEDs 14 are positioned under the microlens array 11 and can be individually digitally turned on or off, thereby generating digitally controlled far-field illumination patterns. FIGS. 2A and 2B illustrate two groups 23 of an array 13 according to two embodiments. Each group 23 is aligned with a single microlens array 11. While the groups 23 and individual arrays 11 are both shaped as squares in FIGS. 2A and 2B, other shapes are possible. The number of light sources 14 in each array 13 shown in FIGS. 2A and 2B varies from one to four. However, the number of light sources 14 within each array 13 may vary. Using a single light source 14 within an array can cover a specific angle where illumination is required. Due to thermal management and other considerations, light sources 14 may not be positioned adjacent to and touching each other. Depending on the LED layout pattern, one LED may need to cover a specific angle that another LED under another lenslet 12 in the array 13 cannot cover. Furthermore, although FIGS. 2A and 2B show particular dimensions of groups 23 of array 13 and particular distances between light sources 14 within the same array, other distances and dimensions are possible.

[0017] The LED array 13 and microlens array 12 form part of a brightfield-illuminated sheet 30. The LEDs 14 in each array 13 are positioned so that their light rays are directed in various directions (angles) by the lenslet 12 aligned with that array 13. The direction of the light rays from each light source 14 in each array ultimately depends on the off-axis position of the light source 14 relative to the optical axis of the lenslet 12 to which the array 13 is aligned. The direction of light from the LED 14 is always perpendicular to the LED 14's emitting surface. The direction of light from the LED 14 refracted by the lenslet 12 is determined by the position of the LED 14 relative to the optical axis of the lenslet 12 and the focal length of the lenslet 12 under which the LED 14 is positioned. The further off-axis the light source 14 is relative to the lenslet 12 (if the optical axis of the light source 14 does not coincide with the mechanical center of the lenslet 12, the light source 14 is off-axis relative to the lenslet 12), the greater the directional angle behind the lenslet 12. By providing different light sources 14 in different locations, various illumination patterns can be generated.

[0018] Each light source 14 in each array 13 is individually controlled by a light source controller 15 executed by at least a computing device 16 interfaced to the array 13. In one embodiment, the light sources 14 are individually addressed via a central backplane, such as a matrix-addressable backplane, although other arrangements are possible. In one embodiment, the at least one computing device 16 may be connected to each of the light sources 14 via a wired connection. In further embodiments, each of the light sources 14 may be interfaced to a wireless transceiver that receives commands wirelessly from the at least one computing device 16 (either directly from a wireless transceiver interfaced to the server 16 or via an internet connection such as the internet or a cellular network).

[0019] In still further embodiments, the interfacing between the computing device 16 and each of the light sources 14 may be achieved via a combination of wired and wireless connections. Additionally, each of the light sources 14 may be powered via a backplane (either wired from a power source such as an AC power source (e.g., a wall outlet) or from a DC power source (e.g., batteries included in the lighting sheet 30), although the lighting sheet 30 may be powered in other ways as well. In one embodiment, the wires supplying power to the lighting sheet 30 may be routed adjacent to the wires through which commands from the at least one computing device 16 are received. In one embodiment, power may be supplied through the computing device 16 (the computing device is interfaced to a power source such as a wall outlet). Still other connection topologies are possible.

[0020] 1 as a server, in further embodiments other types of computing devices 16 may be used, such as laptops, desktop computers, mobile phones, tablets, etc. Still other types of computing devices may be used.

[0021] The lighting controller 15 controls when each light source 14 turns on and off, the pulse width (indicating the time the light source 14 is on), and the amplitude of light emitted by each light source 14, thus controlling the intensity of the light generated by each LED 14. Individual light beams from each LED form lighting pixels on the lighting surface or within a volumetric space. By controlling the lighting 14 that generates each light beam, the lighting controller 15 can adjust their intensity. Furthermore, many lighting pixels partially overlap with neighboring lighting pixels throughout a large lighting space. The amount of overlap is much smaller than the size of the lighting, and by controlling which light sources 14 are turned on at a particular time, the lighting controller 15 can control where such overlap occurs. This can improve the overall quality of the generated lighting pattern (similar to using high-addressability printing with low-resolution spots to achieve a concentrated light distribution for improved tonal expression, which can improve image quality by eliminating ragged edges). Furthermore, by controlling which LEDs 14 are turned on and the parameters of their use, the lighting controller 14 can achieve better lighting utilization, improving lighting application efficiency.

[0022] Computing device 16 is interfaced to storage device 17, which may be within computing device 16 (e.g., internal memory of a laptop computer) or external to computing device 16. Storage device 17 stores data 32 describing characteristics of light sheet 30, including data 18 describing parameters of microlens array 11, such as data describing the number of lenslets 12 in each of microlens array 11, the size and shape of each lenslet 12, and the type of each lenslet 12 in array 11. Other types of data 18 are possible. Light sheet data 32 further includes data 19 indicative of the light source arrays 13 aligned with each of the lenslets 13, including the type of light sources 14 in each array, the number of light sources 14 in each array 13, and the positioning of each of the light sources 14 relative to the lenslets 12 aligned with array 13 (e.g., the off-axis position of the light sources 14 relative to the lenslets 12). Still other types of data 19 are possible. If other components are present in the light sheet 30 , such as spacers 25 , a back reflector 24 , and a light diffuser 26 , the properties of such additional components are included as part of the light sheet data 32 .

[0023] The computing device 16 also executes a light source identifier 21, which acquires data 20 regarding a desired lighting pattern and records it in the recording device 17. The data 20 can be a far-field lighting pattern or a bright-field distribution (other types of lighting patterns are possible). The desired lighting pattern data 20 can indicate the amount and intensity of light emitted by the sheet at a particular location in the lighting space and where the lighting pixels overlap. The data 20 can indicate a lighting pattern for a single time unit, a fixed lighting pattern over a period of time, or a desired variable lighting pattern that changes over a period of time. Additional information can be included in the desired lighting pattern. The light source identifier 21 uses the desired lighting pattern 22 and the lighting sheet data 32 (including the orientations of the light sources 14 as determined by the corresponding lenslets 14) to identify which light sources 14 in the array need to be turned on to create the desired lighting pattern. Figures 5A-5F illustrate several different lighting patterns 22 generated with overlapping lighting pixels. The thick dashed lines in Figures 5A-5F represent the intensity or irradiance level at the lighting plane. As shown with reference to Figures 6A through 6F, the illumination pattern can be far-field. Figure 6A shows light ray paths 22 generated in a small area of ​​sheeting 30 when all LEDs 14 in that area are turned on. Figure 6B shows light ray paths 22 generated in a small area of ​​sheeting 30 when only on-axis LEDs 14 in that area are turned on. Figures 6C and 6D show light ray paths 22 generated in a small area of ​​sheeting 30 when only off-axis LEDs 14 in that area are turned on. The light sources 14 in Figure 6C are oriented differently than the light sources 14 in Figure 6D. Figures 6E and 6F show far-field light ray paths 22 generated in a small area of ​​sheeting 30 when all LEDs 14 in that area are turned on. Figure 6H shows far-field light ray paths 22 generated by off-axis LEDs in sheeting 30. 6A through 6F show that there are multiple ways to spatially illuminate the same object, and the illumination angle can vary depending on which LED 14 is used in combination with which lenslet 12. For example, if a vertical surface such as a person's face needs to be illuminated, light at a more vertical angle will create shadows, while light at a more horizontal angle will create less shadow and make the face look better.

[0024] A large portion of the light emitted by the LEDs is likely reflected back to them by the surrounding environment. This reduces the efficiency of the LEDs (because the reflected light cannot be used for its primary purpose of providing illumination) and heats them. The sheeting includes several components to increase light extraction. One such component is a spacer 25 disposed between the microlens array 11 and the light source array 13. In one embodiment, the spacer 25 may be a triangular pyramidal, reflective honeycomb-shaped spacer 25, as shown with reference to FIGS. 3A and 3B, although the spacer 25 may also have other shapes. FIGS. 3A and 3B show front and back views (side facing the lenslets 12 and LEDs 14, respectively) of a conical, reflective honeycomb-shaped spacer 25 according to one embodiment. Similarly, on the opposite side of the light source array 13, facing the microlens array 11, is a rear reflector 24 that reflects light emitted by the LEDs 14 back toward the microlens array 11. In one embodiment, the spacers 25 and rear reflector 24 may be coated with aluminum or silver. In a further embodiment, the spacers 25 and rear reflector 24 may be coated with a broadband reflective coating. Additional coatings are possible. In one embodiment, the spacers 25 and rear reflector 24 may be similarly coated, and in a further embodiment, the spacers 25 and rear reflector 24 may be differently coated. FIG. 10 shows an expanded view of an illumination sheet 30 including spacers 25 and a rear reflector 24, with LEDs 14 integrated into the LED plane 31, according to one embodiment. FIG. 11 shows the illumination sheet 30 of FIG. 10 with the LEDs 14 emitting light. FIGS. 12A and 12B show simulated illumination patterns achieved using three illumination sheet 30 tiles including conically reflective honeycomb-shaped spacers 25 and a rear reflector 24. The entire illumination sheet includes many illumination sheet tiles 30. FIG. 12A shows a pattern with all light sources 14 in the sheet 30 turned on. The checkerboard pattern shown in FIG. 12B is produced by turning on only some of the light sources 14.FIGS. 13A and 13B show simulated patterns tuned for human visual luminance perception achieved using three lighting sheet tiles 30 including conical reflective honeycomb-shaped spacers 25 and rear reflectors 24. FIGS. 12A and 12B show illumination based on intensity or illuminance, which relates to a physical quantity such as energy or power per unit area. FIGS. 13A and 13B show a logarithmic scale that simulates how the human visual system perceives luminance. Similar to FIGS. 12A and 12B, FIG. 13A shows a pattern in which all light sources 14 in the sheet 30 are turned on. The checkerboard pattern shown in FIG. 13B is created by turning on only a portion of the light sources 14. Note that the spacers 25 can be hollow or solid (i.e., without cavities) and can also have a CPC (compound parabolic concentrator) or rectangular CPC shape. They can be made reflective by using reflective coatings such as aluminum, silver, dielectric multilayer broadband coatings, or by utilizing TIR (total internal reflection) if the spacer is solid, depending on the design.

[0025] Adding spacers and a rear reflector increases the optical efficiency of sheeting 30 by extracting more diffuse light. The exact amount of increase depends on the details of spacers 25 and rear reflector 24. For example, when absorbing honeycomb-shaped spacers 25 and an absorbing rear reflector are used, the optical efficiency of sheeting 30 has been observed to increase by approximately 29%. Similarly, when reflective honeycomb-shaped spacers 25 and a reflective rear reflector are used, the optical efficiency of sheeting 30 has been observed to increase by approximately 52%. The overall optical efficiency achieved by applying an aluminum coating on the honeycomb-shaped spacers 25 and rear reflector 24 and a broadband anti-reflective coating on the honeycomb-shaped spacers 25 is approximately 73.5%. Full coatings on the spacers 25 and rear reflector 24 (fully reflective coating that reflects 100% of the light, fully anti-reflective coating that transmits 100% of the light) increase the optical efficiency to 90%.

[0026] As noted above, the exact improvement in optical efficiency depends on the details of the spacer 25 and lenslet 12. Common glass and plastic optics have a refractive index of n~1.5. The honeycomb-shaped spacer 25 is needed to eliminate stray light, with the focal length of a hemispherical lens of radius R being f~R / (n-1)~2R. For f~2R, f#~1, and NA~0.5, the optical efficiency is ~0.25. For an LED 14 placed at the front focus of the lenslet 12 and positioned off-axis by a distance d, the directivity angle of the exit beam is θ pointing For an LED of diameter D placed at the front focus of a lens, the total divergence of the exit rays is θ divergence ~arctan(D / f). Figure 4 illustrates the directivity and divergence angles. Off-axis lenslet 12 portions can also be used to increase the range of angles that can be generated by the lighting sheet 30, as shown in Figure 18. Figure 18 illustrates light rays from a light source 14 pointing towards an off-axis lenslet 12, according to one embodiment. Off-axis lenslet 12 portions can also be used to vary the addressable angular range across the lighting sheet surface.

[0027] Depending on the exact lighting pattern desired, the light emitted by the light sources 14 may need to be diffused to achieve the desired quality. In a further embodiment, in addition to the rear reflector 24 and honeycomb spacer 25, the sheeting 20 may include a light diffuser 26 positioned over the microlens array 11 (relative to the orientation shown in FIG. 1 ) and facing the side of the microlens array 11 opposite the side facing the LED array 13. The light diffuser 26 diffuses the light that passes through the lenslets 12, thus contributing to achieving complete diffusion of the LED spots (LED spots are bright spots that are too bright to be comfortably seen with the naked eye. In addition to being able to see objects illuminated by the light, the luminaire may be in the field of view, which is generally what is meant by glare). To achieve substantially complete diffusion of the LED spots, the thickness of the diffuser 26 needs to be substantially equal to the LED spacing (the distance between pixels created by the LEDs 14 in the array 13). In practice, if the thickness of the diffuser 26 is 1.5 to 2 times the LED spacing, the individual LED spots begin to disappear, but the brightness of the spots is reduced by about 25 times.

[0028] As described above, lighting achieved using system 10 can be variable, setting it apart from what is possible with existing lighting technologies. Figure 7 shows an example of traditional light control (prior art), which produces high glare and requires moving parts. Figure 8 shows an example of light shifting (prior art), published in the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy's 2019 Lighting R&D opportunities, January 2020, the disclosure of which is incorporated herein by reference. According to this, glare remains far from optimal (high glare) and requires moving parts. Figure 9 is a diagram of a variable lighting sheet that can be achieved using system 10, which has improved light application efficacy (LAE) compared to the technology illustrated in Figures 7 and 8. No moving parts are involved, and glare is suppressed. Variable lighting sheets can provide lighting with spectral content effective for human vision by illuminating only where needed, and digitally improve light application efficacy (LAE) by adjusting light intensity at effective levels.

[0029] Referring again to FIG. 1 , the at least one computing device 16 may also be interfaced to one or more sensors 51. The sensors 51 may be located proximate to the lighting sheet 30 or directly on the lighting sheet 30. The sensors 51 may detect one or more objects that block the desired lighting pattern and that the desired lighting pattern has been incompletely realized. Thus, the sensors 51 may provide additional feedback regarding the lighting created by the system 10 and obstacles that block the lighting generated by the system 10. Such sensors 51 may include motion sensors, light sensors, and motion detectors, although other types of sensors 51 may also be used. The sensors 51 may also be other types of environmental sensors. For example, the sensors 51 may sense the light level around the lighting sheet 30 (such as the room in which the sheet 30 is placed). The sensors 51 may also be temperature sensors that can sense the temperature of either the surrounding environment (if located proximate to the lighting sheet 30) or the lighting sheet 30 (if located on the lighting sheet 30). Similarly, the sensors 51 may be humidity sensors that sense humidity in the environment surrounding the lighting sheet 30. Still other types of environmental sensors are possible.

[0030] The sensor 51 may be interfaced to the at least one computing device 16 via a wired connection, a wireless connection, or a combination of wired and wireless connections (including the use of a network such as the Internet or an internetwork such as a cellular network). For example, if the sensor 51 is disposed on the illumination sheet 30, the sensor 51 may be interfaced to the at least one computing device 16 via a wire routed in close proximity to the wire through which the illumination sheet 30 receives power, commands, or both. Similarly, the sensor 51 may be interfaced to a wireless transceiver that transmits data 52 from the sensor to a wireless transceiver interfaced to the at least one computing device 16. Still other types of interface connections between the sensor 51 and the wireless transceiver are possible.

[0031] The data 52 provided by the sensors 51 may be used by the light source identification unit 21 for any light sources 14 that are turned on either to initially create the desired lighting pattern 20 (if the data is received before the light sources 14 are first turned on), or to resolve problems in generating the desired lighting pattern 20 after the light sources 14 are first turned on if the data 52 indicates that the pattern 20 was not achieved (such as by misidentifying a light source that needed to be turned on) or if the pattern 20 was disrupted (such as by an obstacle blocking the lighting). The light source controller 15 may turn on the light sources 14 identified based on the data 51.

[0032] Data 52 from sensors 51, such as environmental sensors, can also be used by at least one computing device 16 to adjust the intensity of light emitted by identified LEDs 14 and the duration the light source is on. For example, if the room in which the lighting sheet is placed has strong natural light, the intensity level to create the desired lighting 20 may be higher than in a dark room. Similarly, because temperature can affect the light output of the LEDs 14, the intensity of the emitted light can be modulated based on the sensed temperature. Furthermore, if the temperature of the lighting sheet 30 exceeds a predetermined threshold, all light sources 14 in that lighting sheet 30 can be turned off to avoid the risk of fire. Similarly, because the creation of the lighting pattern 20 can be affected by humidity (including foggy conditions), the intensity of the emitted light 16 can be modulated based on the sensed humidity. Thus, by having a feedback mechanism, the system 10 can function programmatically and autonomously, maintaining the desired lighting pattern without continuous human input.

[0033] While one or more computing devices 16 are illustrated as servers as described above, other types of computer devices are possible. The computing device 16 may include one or more modules for carrying out the embodiments disclosed herein. The modules may be implemented as computer programs or procedures written as source code in a conventional programming language and presented for execution by a processor as object or bytecode. Alternatively, the modules may also be implemented in hardware, such as integrated circuits or burned into read-only memory components, such that each computing device 16 can function as a specialized computer. For example, if the modules are implemented as hardware, that specific hardware is specialized to perform the above-described calculations and communications, and other computers cannot use it. Furthermore, when the modules are burned into read-only memory components, the computer storing the read-only memory is specialized to perform the above-described operations that other computers cannot. Various implementations of the source code, object code, and bytecode may be maintained on computer-readable storage media, such as floppy disks, hard drives, digital video disks (DVDs), random access memory (RAM), read-only memory (ROM), and similar storage media. Other types of modules and module functions, as well as other physical hardware components, are possible. For example, computing device 16 may include other components found in programmable computing devices, such as input / output ports, network interfaces, and non-volatile storage, although other components are possible. In embodiments in which computing device 16 is a server, the server may also be cloud-based or a dedicated server.

[0034] Digital control of individual LEDs 14 allows for customization of the illumination provided for the particular environment in which the illumination is provided. FIG. 14 is a flow diagram illustrating a method 40 for brightfield light sheet-based variable illumination control, according to one embodiment. Method 40 can be implemented using system 10 of FIG. 1. Initially, light sheet data 32, including microlens array data 18 and light source array data, is obtained (step 41). A desired light pattern 20 is obtained (step 42), such as through receipt from a user. As described above with reference to FIG. 1, the light sheet data 32, the desired light pattern 20, and optionally data 52 from one or more sensors 51 are used to determine which light sources 14 should be turned on, for how long, and when (step 43). The light sources 14 are turned on and off based on the determination (step 44). Optionally, data 52 from one or more sensors 51 is received by one or more computing devices 16 (step 45), and based on the data, it is determined that which light sources 14 are turned on need to be adjusted (step 46), and method 40 returns to step 43. If no adjustment is needed (step 46), method 40 ends.

[0035] The system 10 and method 40 enable improved lighting application efficiency and control for lights such as those shown in FIGS. 15A-15B and 16A-16B, which illustrate simulations of lighting achievable using specific lighting sheet tiles 30. FIGS. 15A and 15B provide details of the specific lighting sheet tiles used in the lighting simulations. FIGS. 16A and 16B illustrate simulated lighting patterns achievable with the three lighting sheet tiles 30 of FIGS. 15A and 15B. The sheet 30 shown with reference to FIGS. 15A and 15B includes light-absorbing spacers 25. Using reflective spacers 25 helps extract more light, but can also introduce undesirable artifacts. FIGS. 17A and 17B illustrate simulated patterns tailored to human visual brightness when all light sources 14 of the sheet 30 are turned on ( FIG. 17A ) and when only a portion of the light sources 14 required to generate the checkerboard pattern are turned on ( FIG. 17B ). The simulated sheet 30 shown in Figures 17A and 17B includes reflective spacers 25. The reflective spacers 25 extract more light but create artifacts. However, because the illumination sheet 30 creates diffuse illumination (as opposed to an image), the artifacts are buried and are tolerable. Figure 6I is a diagram of ray paths with a low level of artifacts created by small areas of the sheet. As shown in Figure 6I, the artifacts are relatively imperceptible.

[0036] The simulations shown with reference to Figures 12A, 12B, 13A, 13B, 16A, 16B, 17A, and 17B use three tiles 30, which demonstrate the basic performance of the tiles 30 and allow the simulation to be computationally tracked. However, the spaces and areas between and around the tiles 30 can be filled with other tiles 30, thus creating a continuous sheet of large area. This allows for much smoother and more gently varying illumination patterns, angular and spectral components, and more intensity levels.

[0037] While the present invention has been particularly shown and described with reference to embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims

1. 1. A system for bright field illumination sheet type variable illumination output, comprising: a microlens array including a plurality of lenslets; an array of LED (light emitting diode) light sources aligned with each of the lenslets, wherein at least some of the LED light sources in one or more of the arrays are positioned off-axis with respect to the optical axis of the lenslets with which the array is aligned, at a position different from a position with respect to the optical axis at which at least one of the remaining LED light sources in the array is positioned; and a computer controlling each of the LED light sources, the computer comprising at least one processor, wherein: obtaining a desired illumination pattern comprising at least one of a desired far-field illumination pattern and a desired bright-field distribution; Identifying which of the LED light sources need to be turned on to generate the desired lighting pattern based on angles associated with the LED light sources; and controlling the identified LED light sources to generate the desired lighting pattern.

2. the lenslet comprises one or more of a refractive element, an off-axis element, a Fresnel element, a holographic optical element, and a diffractive optical element; 10. The light-emitting diode illumination sheet assembly of claim 1, wherein at least some of the LED light sources have spectral characteristics that differ from other LED light sources.

3. 10. The light-emitting diode illumination sheet assembly of claim 1, further comprising a conical reflective honeycomb spacer disposed between said microlens array and said array of LED light sources.

4. 4. The light-emitting diode lighting sheet assembly of claim 3, wherein the spacers are coated with a coating comprising at least one of aluminum and silver.

5. 10. The light-emitting diode illumination sheet assembly of claim 1, further comprising: a back reflector disposed on a side of the array of LED light sources opposite the side facing the microlens array.

6. 6. The light-emitting diode illumination sheet assembly of claim 5, wherein the reflector is coated with a coating comprising at least one of aluminum and silver.

7. 10. The light-emitting diode illumination sheet assembly of claim 1, further comprising a light diffuser sheet disposed on a side of the microlens array opposite that facing the array of LED light sources.

8. 8. The light-emitting diode illumination sheet assembly of claim 7, wherein a thickness of the light diffuser sheet is substantially equal to the spacing of the identified LED light sources.

9. 10. The light-emitting diode illumination sheet assembly of claim 1, wherein the lenslets are generally hemispherical.

10. at least one sensor interfaced with the computer, the sensor configured to acquire data regarding at least one of one or more objects obstructing the desired lighting pattern, incompleteness of the desired lighting pattern, and ambient conditions of the sensor; 10. The light-emitting diode illumination sheet assembly of claim 1, further comprising the computer configured to perform at least one of: modifying the identified LED light sources; and controlling operation of the identified LED light sources based on the data.

11. 1. A method for bright field illumination sheet type variable illumination output, comprising: acquiring data related to a luminous sheet assembly, the luminous sheet assembly comprising a microlens array including a plurality of lenslets, the luminous sheet assembly further comprising an array of LED (light emitting diode) light sources aligned with each of the lenslets, wherein at least some of the LED light sources in one or more of the arrays are positioned off-axis at an angle to an optical axis of the lenslet with which the array is aligned, and at a different position relative to the optical axis than at least one of the remaining LED light sources in the array is positioned; obtaining a desired illumination pattern comprising at least one of a desired far-field illumination pattern and a desired bright-field distribution; Identifying which of the LED light sources need to be turned on to generate the desired lighting pattern based on angles associated with the LED light sources; and controlling the identified LED light sources to generate the desired lighting pattern; A method wherein said steps are performed by a suitably programmed computer.

12. the lenslet comprises one or more of a refractive element, an off-axis element, a Fresnel element, a holographic optical element, and a diffractive optical element; The method of claim 11 , wherein at least some of the LED light sources have different spectral characteristics than other LED light sources.

13. The method of claim 11 , wherein the luminescent sheet assembly further comprises a conical reflective honeycomb spacer disposed between the microlens array and the array of LED light sources.

14. The method of claim 13 , wherein the spacer is coated with a coating comprising at least one of aluminum and silver.

15. The method of claim 11 , wherein the luminescent sheet assembly further comprises a rear reflector disposed on a side of the array of LED light sources opposite the side facing the microlens array.

16. The method of claim 15 , wherein the reflector is coated with a coating comprising at least one of aluminum and silver.

17. The method of claim 11 , wherein the light emitting sheet assembly further comprises a light diffuser sheet disposed on the side opposite the one side of the microlens array facing the array of LED light sources.

18. 20. The method of claim 17, wherein the thickness of the light diffuser sheet is substantially equal to the spacing of the identified LED light sources.

19. The method of claim 17 , wherein the lenslet is generally hemispherical.

20. detecting, with at least one sensor interfaced to the computer, other data relating to at least one of one or more objects interfering with the desired lighting pattern, incompleteness of the desired lighting pattern, and ambient conditions of the sensor; 12. The method of claim 11, further comprising: modifying the identified LED light source based on the other data; and controlling operation of the identified LED light source based on the other data.

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