发明内容：
[0009]Light transmissive structures according to various embodiments described herein include a light transmissive substrate having first and second opposing faces and array of microprism elements on the first face, with a respective microprism element comprising a plurality of concentric microprisms. The light transmissive structure is configured to receive light from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution.
[0010]In some embodiments, the array of microprism elements extends over substantially the entire first face of the substrate.
[0011]In some embodiments, a respective microprism element includes a plurality of concentric circular microprisms. At least some of the microprisms may have a generally triangular cross section with a peak, with the cross section taken in a plane perpendicular to the first face of the substrate, and may have a prism internal angle defined by the peak that varies as a function of a prism orientation angle that is measured relative to an edge of the substrate. In some embodiments, portions of the microprisms having prism orientation angles of about 45 degrees and 135 degrees have a prism internal angle that is less than a prism internal angle of portions of the microprisms having prism orientation angles of about 0 degrees and 90 degrees.
[0012]In some embodiments, a respective microprism element includes a plurality of concentric elliptical microprisms.
[0013]In some embodiments, a respective microprism element includes a plurality of concentric rounded square microprisms. A respective rounded square microprism may have a shape that fits between a square and its inscribed circle. At least some of the microprisms may have a generally triangular cross section with a peak, with the cross section taken in a plane perpendicular to the first face of the substrate, and may have a prism internal angle defined by the peak that varies as a function of a prism orientation angle that is measured relative to an edge of the substrate. In some embodiments, portions of the microprisms having prism orientation angles of about 45 degrees and 135 degrees have a prism internal angle that is less than a prism internal angle of portions of the microprisms having prism orientation angles of about 0 degrees and 90 degrees.
[0014]In some embodiments, a respective microprism element is generally hexagonal. In some embodiments, a respective microprism element is generally square.
[0015]In some embodiments, a respective microprism element includes a plurality of concentric rounded rhombus microprisms. A respective rounded rhombus microprism may have a shape that fits between a rhombus and its inscribed ellipse. At least some of the microprisms may have a generally triangular cross section with a peak, with the cross section taken in a plane perpendicular to the first face of the substrate, and may have a prism internal angle defined by the peak that varies as a function of a prism orientation angle that is measured relative to an edge of the substrate.
[0016]A respective microprism element may include concentric microprisms of random or pseudorandom size and/or shape. A respective microprism element may be longer in a first direction along the substrate than in a second, orthogonal direction along the substrate.
[0017]In some embodiments, a respective microprism element has an area of less than about 1 square centimeter on the second face of the substrate. In some embodiments, a respective microprism element has an area of about 0.1 square centimeters or less on the second face of the substrate. In some embodiments, a respective microprism is substantially undetectable by the naked eye.
[0018]In some embodiments, at least some of the microprisms have a generally triangular cross section with a peak, with the cross section taken in a plane perpendicular to the first face of the substrate. The peak may be generally parallel to the first face of the substrate. The peak may be a sharp peak. The peak may be a rounded peak. In some embodiments, (i) a respective microprism has an internal angle defined by the peak of between about 60 and 100 degrees; and/or (ii) a respective microprism has a pitch of between about 10 microns and 3 mm. In some embodiments, (i) a respective microprism has an internal angle of between about 70 and 90 degrees; and/or (ii) a respective microprism has a pitch of between about 10 microns and 1 mm.
[0019]In some embodiments, substantially all of the microprism elements include a plurality of concentric microprisms.
[0020]In some embodiments, adjacent microprism elements are in contact with one another. In some embodiments, the array of microprism elements includes gaps between at least some of the microprism elements, and the light transmissive structure further includes gap-filling microstructures in at least some of the gaps.
[0021]In some embodiments, at least some of the microprisms have a generally triangular cross section with a peak, with the cross section taken in a plane perpendicular to the first face of the substrate, and with the peak having a height relative to the first face of the substrate that varies as a function of a prism orientation angle that is measured relative to an edge of the substrate.
[0022]In some embodiments, the light transmissive structure is configured to receive light having a Lambertian distribution from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution. In some embodiments, the light transmissive structure is configured to receive light having a light distribution having a Full Width at Half Maximum (FWHM) of at least about 30 degrees from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution. In some embodiments, the light transmissive structure is configured to receive light having a light distribution having a Full Width at Half Maximum (FWHM) of at least about 40 degrees from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution. In some embodiments, the light transmissive structure is configured to receive light having a light distribution having a Full Width at Half Maximum (FWHM) of at least about 60 degrees from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution. In some embodiments, the light transmissive structure is configured to receive light having a light distribution having a Full Width at Half Maximum (FWHM) of at least about 80 degrees from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution.
[0023]In some embodiments, the light transmissive structure includes at least one diffusion feature, and the light transmissive structure is configured to receive collimated and/or near-collimated light from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution. The diffusion feature may include surface roughness on at least some of the microprisms. The diffusion feature may include a diffuser on the second face of the substrate. The diffusion feature may include a light scattering agent in at least some of the microprisms and/or in the substrate. The diffusion feature may include a diffusive coating on at least some of the microprisms.
[0024]In some embodiments, a respective microprism follows a prism path along the first face of the substrate. The microprism may have a generally triangular cross section with a peak and a pitch, with the cross section taken in a plane perpendicular to the first face of the substrate. The peak may have a height relative to the first face of the substrate that varies along the prism path and/or the pitch may vary along the prism path.
[0025]In some embodiments, the light transmissive structure is in combination with at least one light source and a housing that is configured to hold the at least one light source and the light transmissive substrate so that light from the light source impinges on the first face of the substrate and emerges from the second face of the substrate in a 2D batwing distribution. The housing may define a light exit surface area where the substrate is held. In various embodiments, a respective microprism element has an area on the first face of the substrate that is at least one order or magnitude, at least two orders of magnitude, and/or at least four orders of magnitude smaller than the light exit surface area. In some embodiments, the array of microprism elements on the first face of the substrate extends over substantially the entire light exit surface area.
[0026]In some embodiments, the light transmissive structure is in combination with at least one light source wherein the light transmissive substrate is suspended under the light source so that light from the light source impinges on the first face of the substrate and emerges from the second face of the substrate in a 2D batwing distribution.
[0027]Light transmissive structures may be fabricated according to various embodiments described herein by imaging onto a photoimageable material an image of a plurality of microprisms having a geometric feature that is configured to distribute light transmitted through the microprisms in a 2D batwing distribution. The photoimageable material that was imaged is then used to replicate an image of a plurality of microprisms in and/or on a substrate, the plurality of microprisms also having a geometric feature that is configured to distribute light transmitted through the microprisms in a 2D batwing distribution. The imaging may be performed by scanning a laser across the photoimageable material, the laser defining the image of a plurality of microprisms having the geometric feature that is configured to distribute light transmitted through the microprisms in a 2D batwing distribution.
[0028]Light transmissive structures according to various embodiments described herein include a light transmissive substrate having first and second opposing faces. A plurality of microprisms are on the first face, with the microprisms having a generally triangular cross section in a plane that is perpendicular to the first face, and the microprisms are distributed on the first face of the substrate in a plurality of different prism orientation angles measured from an edge of the substrate. The light transmissive structure is configured to receive light having a Full Width at Half Maximum (FWHM) of at least about 30 degrees and/or Lambertian light at the first face and distribute the light emerging from the second face in a 2D batwing distribution. In some embodiments, the light transmissive structure is configured to receive light having a Full Width at Half Maximum (FWHM) of at least about 40 degrees and/or Lambertian light at the first face and distribute the light emerging from the second face in a 2D batwing distribution.
[0029]In some embodiments, the microprisms are distributed on the first face of the substrate generally equally in each of the plurality prism orientation angles. In some embodiments, microprisms having a prism orientation angle of about 45 and 135 degrees are distributed on a greater area of the first face of the substrate than microprisms having a prism orientation angle of about 0 and 90 degrees. In some embodiments, the microprisms have an internal angle that varies as a function of prism orientation angle. In some embodiments, the plurality of microprisms and/or interspersed microstructures substantially cover the first face of the substrate.
[0030]Light transmissive structures according to various embodiments described herein include a light transmissive substrate having first and second opposing faces. An array of microprism elements is on the first face, with a respective microprism element including a plurality of concentric microprism patterns, and with a respective microprism pattern including a plurality of pyramids arranged in a generally elliptical configuration. The light transmissive structure is configured to receive light from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution.
[0031]Light transmissive structures according to various embodiments described herein include a light transmissive substrate having first and second opposing faces. An array of microprism elements is on the first face, with a respective microprism element including at least one ring including a plurality of microstructure pyramids that is rotated randomly and/or pseudorandomly on the first face about an axis that is orthogonal to the substrate relative to at least one other microprism element. The light transmissive structure is configured to receive light from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution.
[0032]In some embodiments, a respective microprism element includes first and second concentric rings each comprising a plurality of microstructure pyramids, and the first and second rings are each rotated randomly and/or pseudorandomly on the first face relative to one another. The second ring may surround the first ring and may include a first microstructure pyramid including a face that faces a center of the first and second concentric rings and a second microstructure pyramid that is adjacent the first pyramid and including a face that faces away from the center of the first and second concentric rings.
[0033]In some embodiments, a respective microprism element includes a plurality of concentric rings, with a respective ring including a plurality of microstructure pyramids. A respective ring may be rotated randomly and/or pseudorandomly on the first face relative to the other rings in a respective microprism element. The plurality of concentric rings may include a central ring and a plurality of surrounding rings. A respective surrounding ring may include a first microstructure pyramid including a face that faces a center of the plurality of concentric rings and a second microstructure pyramid that is adjacent the first pyramid and including a face that faces away from the center of the plurality of concentric rings.
[0034]In some embodiments, a majority of the microstructure pyramids in a respective ring include a face that faces away from a center of the plurality of concentric rings. In some embodiments, substantially all of the microstructure pyramids in a respective ring include a face that faces away from the center of the plurality of concentric rings.
[0035]In some embodiments, a majority of the microstructure pyramids in a respective ring include a face that is oriented at a specific angle relative to a center of the plurality of concentric rings. In some embodiments, substantially all of the microstructure pyramids in a respective ring include a face that is oriented at a specific angle relative to the center of the plurality of concentric rings.
[0036]In various embodiments, the plurality of concentric rings includes at least 5 rings and at least 10 rings.
[0037]In some embodiments, a respective microstructure pyramid is a triangular pyramid.
[0038]In some embodiments, the array of microprism elements extends over substantially the entire first face of the substrate. In some embodiments, adjacent microprism elements are in contact with one another. In some embodiments, the array of microprism elements includes gaps between at least some of the microprism elements, and the light transmissive structure includes gap-filling microstructures in at least some of the gaps.
[0039]In some embodiments, the second face of the substrate is substantially smooth. In some embodiments, the light transmissive structure is configured to produce a visible pattern to a viewer of the light transmissive structure at a viewing distance of about three feet, with the visible pattern corresponding to the array of microprism elements on the first face.
[0040]A respective microstructure pyramid and/or ring may be undetectable or substantially undetectable by the naked eye at a viewing distance of about three feet or more.
[0041]The light transmissive structure may be configured to receive light having a Lambertian distribution from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution. The light transmissive structure may be configured to receive light having a light distribution having a Full Width at Half Maximum (FWHM) of at least about 30 degrees, at least about 40 degrees, at least about 60 degrees and/or at least about 80 degrees from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution.
[0042]In some embodiments, the light transmissive structure includes at least one diffusion feature. The at least one diffusion feature may include: surface roughness on at least some of the microstructure pyramids; a diffuser on the second face of the substrate; a light scattering agent in at least some of the microstructure pyramids and/or in the substrate; and/or a diffusive coating on at least some of the microstructure pyramids. The light transmissive structure may be configured to receive collimated and/or near collimated light from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution.
[0043]In some embodiments, the light transmissive structure is in combination with at least one light source and a housing that is configured to hold the at least one light source and the light transmissive substrate so that light from the light source impinges on the first face of the substrate and emerges from the second face of the substrate in a 2D batwing distribution. The housing may define a light exit surface area where the substrate is held. In various embodiments, a respective microprism element has an area on the first face of the substrate that is at least one order or magnitude, at least two orders of magnitude, and/or at least four orders of magnitude smaller than the light exit surface area. In some embodiments, the array of microprism elements on the first face of the substrate extends over substantially the entire light exit surface area.
[0044]In some embodiments, the light transmissive structure is in combination with at least one light source wherein the light transmissive substrate is suspended under the light source so that light from the light source impinges on the first face of the substrate and emerges from the second face of the substrate in a 2D batwing distribution.
[0045]Light transmissive structures may be fabricated according to various embodiments described herein by imaging onto a photoimageable material an image of a plurality of microstructure pyramids having a geometric feature that is configured to distribute light transmitted through the microstructure pyramids in a 2D batwing distribution. The photoimageable material that was imaged is then used to replicate an image of a plurality of microstructure pyramids in and/or on a substrate, the plurality of microstructure pyramids also having a geometric feature that is configured to distribute light transmitted through the microstructure pyramids in a 2D batwing distribution. The imaging may be performed by scanning a laser across the photoimageable material, the laser defining the image of a plurality of microstructure pyramids having the geometric feature that is configured to distribute light transmitted through the microstructure pyramids in a 2D batwing distribution.
[0046]Light transmissive structures according to various embodiments described herein include a light transmissive substrate having first and second opposing faces, with a plurality of pyramid microprisms on the first face. The microprisms are distributed on the first face of the substrate with a plurality of different pyramid face orientation angles measured from an edge of the substrate. The light transmissive structure is configured to receive light from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution.
[0047]In some embodiments, the microprisms are distributed on the first face of the substrate in generally equal measure for each of the plurality of pyramid face orientation angles. In some embodiments, a respective pyramid microprism is rotated randomly and/or pseudorandomly on the first face relative to at least one other pyramid microprism.
[0048]Light transmissive structures according to various embodiments described herein include a light transmissive substrate having first and second opposing faces. An array of microprism elements is on the first face, with a respective microprism element including a plurality of concentric microprism patterns, and with a respective microprism pattern including a plurality of triangular pyramids arranged in a generally elliptical configuration. The light transmissive structure is configured to receive light from a light source facing the first face and distribute the light emerging from the second face in a 2D batwing distribution.
[0049]In some embodiments, a respective pyramid includes a face that is oriented at a specific angle relative to a center of the plurality of concentric microprism patterns. In some embodiments, a respective microprism element includes a microprism pattern that is rotated randomly and/or pseudorandomly on the first face relative to at least one other microprism element.
[0050]It is noted that any one or more aspects or features described with respect to one embodiment may be incorporated in a different embodiment although not specifically described relative thereto. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination. Applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to be able to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. These and other objects and/or aspects of the present invention are explained in detail in the specification set forth below.
具体实施方式：
[0117]For collimated light, beam shaping is well known in the art. Refractive and diffractive elements exist that can form a (collimated) laser beam into a specific shape. Such elements are available commercially, for example, from Jenoptik, Jena, Germany (http://www.jenoptik.com/en-microoptics-refractive-optical-elements-ROEs). These elements can shape a laser beam into a line, crosshair, square, circle, and even images (such as corporate logos) to project on a surface, and are commonly used in machine-vision applications. Beam shapers generally require substantially collimated light. As is shown by the review of prior art herein, a shaper does not appear to currently exist that can convert a Lambertian distribution into a 2D batwing distribution, despite the value the lighting industry would place on having such a product.
[0118]A 90-degree linear prism optic has one smooth surface and the other one is textured by an array of linear prisms with 45-degree sidewalls, as shown in U.S. Pat. Nos. 3,288,990 and 4,542,449, in which one or two layers of prism optics are used to increase brightness directly under a luminaire, and reduce high-angle brightness. A film with the same properties is described in U.S. Pat. No. 4,906,070. A common application of such a prism film is for brightness enhancement of the back light unit inside a display system. In both lighting and displays, a brightness-enhancing prism is used with the light entering smooth surface of the optic, and thus the prisms facing away from the light source. Rays incident perpendicular to the surface of the film will encounter total internal reflections (TIR) from the prisms. Those light rays are generally reflected back into the backlight, which is generally configured with high reflectivity to recirculate those rays back toward the prism film (sometimes repeatedly), until they enter the prism film at larger incident angle and are allowed to pass to the viewer of display. Rays incident at larger angles are at least in part refracted through the prisms, and on average over all angles, the average exit angles are smaller than the average entrance angles, when measured relative to the normal to the prism optic. The angle bending and recirculation process creates a narrower FWHM light distribution (approx 70-95 degrees) than the incident Lambertian distribution (approx 120 degrees), and on-axis brightness enhancement. Said another way, a prism illuminated by Lambertian light in this orientation and with appropriate recirculation will increase intensity at the nadir, while reducing the FWHM. Thus, a prism used in this manner does not create a batwing distribution.
[0119]In contrast, it is known that if the light enters the prism side (rather than the smooth side) of a linear prism film or optic, it will exit in two lobes, similar to a 1D batwing shape (as mentioned in U.S. Pat. No. 4,300,185 or 4,233,651). FIG. 3A illustrates how collimated light will be divided (refracted) into two branches by prism structures. The angular deviation of this refraction is determined by the refractive index of the material, and the sidewall angle of the prisms. Typical refractive indices for prism films are in the range of 1.45 to 1.6. Smaller prism internal angle or greater refractive index will result in larger refraction angles. Even Lambertian light impinging onto the prism side of a linear prism film will exit that film in a 1D split distribution, in which light is approximately a batwing shape. This use of a linear prism is referenced on the Fusion Optix website at http://fusionoptix.com/lighting/components/light-shapers.htm (as of May 17, 2013), a diagram adapted from which is shown in FIG. 3B. The reduction of light intensity at theta (θ)=0 degrees (straight down in the image) is called “nadir suppression.”
Measurement
[0120]Light distributions are typically measured using goniometric apparatus similar to that described in the IES LM-79 standard, as illustrated in FIG. 4. In the figure, a luminaire or illuminated optical device is depicted (labeled SSL product) emitting light in a downward dimension. The two circles with dots on their perimeters represent planes at two different azimuthal angles φ (phi). In each of these planes, the polar angle θ (theta, ranging from −180 to 180 degrees) is defined as indicated. Example measurement points in the phi=0 degree and phi=90 degree planes are depicted as dots. At each of these points, luminous intensity is measured as a function of the theta angle from the principle axis of the light source. This luminous intensity is measure by an optical detector, the optical detector and/or light source moved relative to each other so that the optical detector measures light at the desired angles. In practice a light source can be measured at any group of phi and theta points desired. Many lights emit generally in one hemisphere, and thus theta will often be measured from −90 to 90 degrees.
[0121]Confirming the data presented in FIG. 3B, FIG. 5 shows the light intensity distribution measured by the applicant by illuminating a flat prism film with a Lambertian LED light source, with the prism side facing the light. The solid line represents the measurement made in a plane designated phi=90 degrees that is perpendicular to the orientation of the linear prisms on the prism film. The dashed line shows the phi=0 degree plane parallel to the prism orientation, and shows the output distribution is Lambertian.
[0122]It is often unsatisfactory, however, to utilize only a linear prism film directly in a lighting application. One skilled in the art will recognize that the distribution shown in FIG. 5 is not advantageous for uniform lighting of a planar surface due to excessive suppression of nadir intensity, which will manifest as a dark spot on the illuminated surface. Many lighting designers will find that Illuminance at nadir is simply too low to achieve desirable illumination uniformity in many applications.
[0123]To achieve a desirable 1D batwing distribution from a 90-degree linear prism, extra diffusion of the light is usually needed due to over-suppression of the nadir with linear prisms alone. FIGS. 6A and 6B plot the measured light intensity distributions at phi=90 degrees, perpendicular to the prism orientation, of a luminaire employing a prism film followed by an additional diffuser layer, with gentle and strong diffusing strength respectively. In the phi=0 degree plane, parallel to the prism orientation, these distributions are not batwing; they are approximately Lambertian, and thus the distribution is a 1D batwing distribution. The data suggest that an added diffuser modifies the 1D batwing distribution from a prism film and the outcome is much more suitable for general lighting applications than prism films alone.
[0124]Many 1D and 2D batwing distributions exist in the art.
[0125]Batwing distributions are known in the art, and are usually created using specific focusing optics (e.g. lenses and/or reflectors), and/or specific features in the geometry of a light source, such as lamp placement, and placement of internal or external baffles, louvers, openings, and placement of ordinary diffusers. Examples include US Patent Application Publication 20050201103 A1, US Patent Application Publication 20130044476 A1, U.S. Pat. Nos. 4,218,727 A, 5,105,345 A, 6,698,908 B2, 3,329,812, EP Publication 1925878 A1, U.S. Pat. Nos. 3,725,697, 7,273,299, 5,149,191, EP Publication 2112426 A2. In many cases the focusing optics, baffles, etc., increase the cost of a luminaire. These designs are generally strongly dependent on the placement of the light source, and generally require alignment of the reflectors, baffles, etc. with the light source. Designing these luminaires with 1D or 2D circular or rectangular batwing distributions is generally difficult and slow, requiring either advanced computer modeling or trial-and-error testing, which can be too costly for some smaller lighting manufacturers. In particular, rectangular and square batwing distributions are the most difficult to create, due to the lack of a radial symmetry.
[0126]In U.S. Pat. No. 3,721,818, Stahlhut describes an article capable of controlling light distributions, such as reducing glare and creating 1D and 2D batwing distributions. The article involves shaped surfaces on one or both sides of a substrate, with additional “light reducing areas” (e.g. paint) which can be opaque, reflective or absorbing. Undesirably, the need for these light reducing areas may both increase cost and decrease efficiency of the light fixture. In some embodiments, the need to create structures on both sides of the surface that are aligned to each other may also add expense and complexity.
[0127]In U.S. Pat. No. 3,866,036, Taltavull describes a prism-like structure including prisms or linear lenses with truncated tips upon which thick opaque structures are formed. These may create effective batwing light distributions but may be expensive and difficult to create, and the opaque structures may incur additional losses of light, reducing overall fixture efficiency. In addition, the lack of diffusion in these structures means that from certain viewing angles, the light source(s) may be visible as undesirable bright spots on the surface of the luminaire.
[0128]In U.S. Pat. No. 3,978,332, Taltavull describes a ring-shaped structure including concentric prisms or linear lenses with truncated tips upon which are created opaque structures. These can create effective 2D batwing light distributions but may be expensive and difficult to create, and the opaque structures may incur additional losses of light, reducing overall fixture efficiency. Taltavull additionally uses the exact placement of lenses and a carefully designed reflector, all of which elements together combine to create the desired 2D batwing light distribution, which may add further expense.
[0129]In U.S. Pat. No. 4,161,015, Dey et. al., describe a luminaire with batwing distribution created by selective reflectivity from a multilayer interference filter with reflectivity and transmissivity that vary with angle of incidence. Unfortunately such an interference filter may be expensive to create, and may generally be wavelength-sensitive. In addition, when viewed from certain angles, there is undesirably no obscuring of the light sources.
[0130]In US Patent Application Publication 20090296401 A1 Gutierrez describes a system that uses a moving resonant mirror to create a desired light distribution, including batwing distribution. Such a system may suffer from excess power consumption, noise created by the mechanical motion, flicker, and possibly reliability issues associated with moving parts.
[0131]In U.S. Pat. No. 4,059,755 A, Brabson describes the use of three different prism optics in two layers to create a 1D batwing distribution. This system may undesirably need to be aligned to a linear source. Undesirably, the two layers of custom prism optics may be expensive, and may incur a reduction of efficiency associated with reflections from multiple optical interfaces.
[0132]In many other examples, including US Patent Application Publication 20090225543, US Patent Application Publication 20120275150, PCT Publication WO2012109141 A1, U.S. Pat. No. 7,658,513, US Patent Application Publication 20130042510, U.S. Pat. No. 8,339,716 B2, US Patent Application Publication 20130039090 A1, U.S. Pat. No. 7,273,299 B2, U.S. Pat. No. 7,731,395 B2, US Patent Application Publication 2009096685 A2, US Patent Application Publication 20110141734 A1, U.S. Pat. No. 7,942,559 B2, U.S. Pat. No. 7,993,036 B2, individual light sources (typically LEDs or collections of LEDs) are modified using lenses, reflectors, light pipes, or the LED package, in close proximity to light sources. Many light distributions can be created this way (as known in the art), including 1D and 2D batwing distributions. In many general lighting applications, large numbers of LEDs (typically tens or hundreds) are used over the area of the luminaire, and the use of lensed LEDs with non-Lambertian distributions can be costly. Also, individual LEDs can be piercingly bright when unobscured, even if focused using localized lenses. To achieve desirable smooth appearance of a luminaire and obscure the light sources, additional diffusers may be required, incurring higher costs. Further, such diffusers may in some cases not be able to sufficiently homogenize the surface appearance of the luminaire without degrading the distribution created by the LEDs.
[0133]In U.S. Pat. No. 2,394,992, Franck describes a luminaire with 2D elliptical batwing light distribution employing a lamp (substantially a point source) illuminating a compound lens with Fresnel-lens-like prisms on both surfaces. One surface is a radial compound Fresnel lens including a central spreading region and a peripheral focusing region to form a 2D circular batwing distribution. The other surface is a linear Fresnel lens which is the regressed optical equivalent of a negative or divergent cylindrical lens surface and provides additional spreading of the batwing distribution along one axis, transforming the circular batwing to an elliptical batwing distribution. This solution may depend on a light source that is substantially a point-source, and thus may not work with extended Lambertian sources. In addition the optic undesirably is custom designed for the luminaire (e.g. the distance from the light source and total illuminated diameter), and may need to be aligned to the light source.
[0134]In U.S. Pat. No. 5,997,156 A, Perlo et. al. describe creating rectangular or square light distributions using rippled lenticular lenses or TIR prism lenses in conjunction with a collimated light source (in the example provided, using a parabolic reflector). However, the techniques mentioned may not work with Lambertian light sources.
[0135]In U.S. Pat. No. 3,829,680, Jones describes a lighting panel with a continuous pattern of triangle projections, each triangle having three mutually perpendicular smooth faces (in today's nomenclature, such a pattern is often called “corner cube”). This lighting panel can provide a 2D batwing distribution from Lambertian light input. The distribution created by this type of structure has a hexagonal rosette pattern when viewed on a flat floor (due to having refraction through repeated flat planes at only six geometric orientations), and is a rough approximation to a 2D circular batwing distribution. In some cases, these hexagonal artifacts will be undesirable to lighting designers. In addition, due to the small number of geometric orientations of the faces, light sources are not sufficiently obscured for many lighting purposes. Jones discloses the use of a diffuser in conjunction with the corner cube sheet, which successfully obscures the light sources but incurs extra expense and loss of efficiency associated with reflections from the extra optical interfaces involved in using two separate optical elements.
[0136]In U.S. Pat. No. 586,211, Basquin describes a window composed of prisms that are designed to spread sunlight into a room. Basquin arranges the prisms in unit cells (e.g. hexagons or squares), with prisms within each unit cell having a desired orientation, the net effect of the prisms in all oriented cells having a desired effect on the light. Basquin is designed to work with sunlight, which will be recognized by those skilled in the art as a collimated light source relative to a window. Basquin does not create a 2D batwing light distribution.
[0137]In U.S. Pat. No. 4,984,144, a light fixture is provided in which a high aspect ratio fixture (such as a thin sign) is illuminated from the side, and in which prisms are used in total internal reflection (TIR) mode to direct light outside the fixture, maximizing light exiting at an angle normal to the surface of the fixture (and thus not in a batwing distribution). Because of the internal side illumination, the light source is strongly directional, and thus not Lambertian. This fixture does not produce a batwing distribution.
[0138]In U.S. Pat. No. 5,193,899, a prism is used in conjunction with a diffuser to increase the uniformity of brightness on the surface of a sign to hide “lamp images” (i.e, provide a smooth appearance on the surface of the sign) that obscures the location and visibility of the underlying lamps. Because of the strong diffusers used to make the surface of the sign highly uniform, the fixture does not emit light in a batwing distribution.
[0139]In U.S. Pat. No. 5,243,506 A, a light-pipe architecture illuminated by a single source at the end of the light pipe uses prisms to couple light out of the light pipe at a point and in a direction substantially perpendicular to the surface of the light pipe at that point. By using metal masking in selective locations to determine where light can strike the prisms and escape the light pipe, 1D light distributions including 1D batwing distributions can be sculpted.
[0140]CN 202532218 U discloses a lamp structure with batwing light intensity distribution. The lamp structure comprises at least two light-emitting diode (LED) groups, a light guide plate, a reflecting part and a prism sheet, and is characterized in that: the light guide plate is provided with a first surface and a second surface; and the first surface is provided with a micro structure. Distribution in a way that both sides are sparse while middle is dense is adopted, so that the refraction angle of light rays is changed, and the light rays are refracted out of the light guide plate. Light rays are uniformly scattered effectively through the geometric structure on the prism sheet facing the light guide plate, so that batwing light intensity distribution is achieved.
[0141]Investigation
[0142]In trying to design an optical film or plate with 2D circular batwing distribution, the present inventors considered surface features including close-packed arrays of cones, which is the 2D analog of a 1D linear prism. As mentioned earlier, it is known that when a prism optic is illuminated with Lambertian light impinging upon the smooth side (i.e., used in a brightness-enhancing orientation, rather than a batwing-generating orientation), the intensity is amplified at the nadir, while the FWHM is reduced. Analogously, when a close-packed cone array optic is illuminated by Lambertian light upon the smooth side, the intensity is amplified at the nadir, while the FWHM is reduced, as one skilled in the art would expect, and as the 1D prism-2D cone analogy would imply. Also as expected, this light distribution substantially has radial symmetry around the theta=0 axis.
[0143]In the opposite orientation, as mentioned earlier, Lambertian light entering the prism side of a prism sheet (i.e., used in the batwing-generating orientation) provides an approximate 1D (linear) batwing distribution. Expecting Lambertian light entering the cone side of a cone sheet to analogously form a 2D circular batwing distribution, the present inventors tested a commercially-available sheet comprising an array of cones protruding from one side, with a smooth surface on the opposite side. The cones were arranged in a hexagonal grid on a 2 mm repeat length, with 100 degree internal angle at the tip. Surprisingly, upon testing, the cones did not create a batwing distribution at all, as shown in FIG. 7, measured using an incoming 120 degree Lambertian distribution. When measured with an 80 degree Lambertian incoming light distribution, the cones again did not create a batwing distribution, as shown in FIG. 8. The same cone array was then tested with collimated light illuminating the cone side, and as expected, created a circle of light. The slice measured at phi=0 is shown in FIG. 9, with slices measured at any other azimuthal angle substantially the same. Similarly, the same cone array was measured with a near-collimated 20-degree light into the cone side, and created the batwing-like distribution of FIG. 10. Thus a cone array can create batwing distributions for collimated and narrow near-collimated distributions, while surprisingly failing to do so for wide (Lambertian) distributions.
ADDITIONAL REFERENCES
[0144]In US Patent Application Publication 20120275185, Edamitsu discloses an illuminator that creates 2D batwing distributions using prisms facing the light source. In this publication, no detail is given as to the incoming light distribution produced by the light source (it is not stated whether the light source is collimated or Lambertian). However, the light distribution of the light source can be deduced from the data provided. In the embodiment of FIG. 5 of that '185 publication, it is stated that a cone array, with flat spaces in between, can produce a batwing distribution shown in FIG. 6 of the '185 publication. In consideration of the data provided on cone arrays by the present inventors, one can determine that the data of FIG. 6 of the '185 publication only makes sense if the source is substantially collimated. This is similarly true for the other embodiments in the '185 publication. The addition of and need for flat areas, as described to fill in extra light at nadir, also implies a collimated light source. Such flat areas generally are necessary in part because of the collimated light—without the flat areas, upon illumination by collimated light there would be substantially no illumination at nadir, providing insufficient illumination at nadir to evenly illuminate a flat surface. Substantial flat areas are disadvantageous when used with Lambertian light sources, however, because too much Lambertian light is passed through said flat areas, reducing or preventing batwing distributions from being formed. In addition, flat areas in a lighting optic are particularly disadvantageous because they allow a direct view of the light sources (lamps), whereas hiding or obscuring lamps in lighting is generally preferred.
[0145]Similar to the '185 publication, US Patent Application Publication 20130070478, Edamitsu discloses an approximate cone including a hexagonal prism, interspersed with triangular corner-cube elements. As in the '185 publication, the '478 publication does not disclose the light distribution of the light source used in testing, but it can be deduced to be substantially collimated following the same argument above. This approximate cone can be reasonably expected by one skilled in the art to have performance similar to a cone, which as shown by the present inventors' data above has limitations on its ability to form batwing distributions from Lambertian light. In addition, the complex structure is difficult to manufacture, generally requiring precision diamond cutting of a master form or tool. As with Jones' U.S. Pat. No. 3,829,680, discussed above, the '489 publication describes planar surfaces oriented in only six directions. Due to this small number of geometric orientations of the faces, light sources are not sufficiently obscured for many lighting purposes.
[0146]Although in some cases the patterns of Edamitsu's '185 and '478 publications, and Jones' '680 patent may achieve 2D batwing distribution that are acceptable to some lighting designers and specifiers, the patterns of various embodiments described herein may be particularly advantageous due to their ability to work with Lambertian sources, increased obscuration of light sources, ease of manufacture, smoothness of light distribution, flexibility and controllability of the light distribution and its shape (such as making square or rectangular distributions), and/or capability of creating visually pleasing surface patterns.
[0147]In U.S. Pat. No. 7,660,039, Santoro et al. disclose kinoform diffusers that (a) reduce luminance at high viewing angles (known as glare), and/or (b) when disposed on either side of transparent or curved “centrally located regions” directly beneath light sources produces a 1D or 2D batwing luminous intensity distribution. Undesirably, this “centrally located region” appears to be required to form a batwing distribution. Of the embodiments employing a contiguous or monolithic diffuser (and thus having no curved or transparent “centrally located region”), none provide a batwing luminous distribution (although many of them reduce glare). When a “centrally located region” is included and located directly below the light source as taught, then rays emitted downward and near-downward by the light source toward said region do not strike the kinoform diffuser, which is located at the sides. Thus the kinoform diffuser itself is not creating a batwing distribution from a Lambertian light source. Rather two spatially-separated kinoform diffusers (neither of which is directly beneath the light source) cooperate to create a batwing distribution (creating one half of the distribution each) from collections of rays that are directional (each having a strong sideways component) and contain substantially no directly-downward component to their direction, and thus are not Lambertian. The need for a “centrally located region” may increase expense, and, in the embodiments for which said region is transparent, there is undesirably no obscuration or hiding of the lamps. Additionally, the diffuser may need to include multiple light scattering elements, “on each of which are one or more sub-elements.” In practice these sub-elements may be very difficult to create and control. Advantageously, various embodiments described herein do not require kinoform or holographic diffusers, do not require such sub-elements, and can be used in contiguous spans without the need for transparent or curved “centrally located regions.”
[0148]In U.S. Pat. No. 7,837,361, Santoro et al. disclose a light control device implemented with a diffuser that creates batwing light intensity distributions. As with the Santoro '039 patent, a “centrally located region” appears to be required to form a batwing distribution, resulting in the same disadvantages explained above for the '039 patent.
[0149]In U.S. Pat. No. 8,047,673, Santoro describes a light control device implemented with multiple diffusers. The light control devices and luminaires disclosed create 1D batwing light distributions by means of a central lamp, multiple diffusers, and openings with carefully designed placement. As described above, the placement of the diffusers separated by a central element means that each diffuser receives light from a non-Lambertian collection of rays and does not create a batwing light distribution from a Lambertian light distribution. The luminaire described does create 1D batwing distributions, but does so using the diffusers, lamp, openings, and internal reflections working collectively, and thus is distinct from various embodiments described herein, which can create 2D batwing distributions from Lambertian light.
Potential Advantages
[0150]Various embodiments described herein can provide a 2D batwing diffuser that can form light into useful 2D batwing distributions, including but not limited to elliptical, circular, rectangular, and square distributions.
[0151]Various embodiments described herein can provide a 2D batwing diffuser that can, when used in a luminaire, provide substantially uniform illumination over a flat surface of a defined shape, including but not limited to elliptical, circular, rectangular, and square shapes.
[0152]Various embodiments described herein can provide a 2D batwing diffuser that can form light from Lambertian-distributed sources, including LED point sources and LED arrays, into useful 2D batwing or flat-field distributions.
[0153]Various embodiments described herein can provide a 2D batwing diffuser that can form light from approximately-Lambertian sources into useful 2D batwing or flat-field distributions.
[0154]Various embodiments described herein can provide a 2D batwing diffuser that can form light from substantially collimated or near-collimated sources into useful 2D batwing or flat-field distributions.
[0155]Various embodiments described herein can provide a contiguous or monolithic 2D batwing diffuser that can form 2D batwing distributions without requiring cooperation from other light emitting region(s) such as a centrally located transparent region.
[0156]Various embodiments described herein can provide a 2D batwing diffuser optic for a luminaire that does not require specific alignment relative to the luminaire's light sources.
[0157]Various embodiments described herein can provide a 2D batwing diffuser that is shift-invariant, and thus can be manufactured in large areas such that a diffuser suitable for a given luminaire can be cut from an arbitrary location of the large area without the need to align the cut to specific optical features (such as a central point) of the optical structure.
[0158]Various embodiments described herein can provide a 2D batwing diffuser with high optical transmission, having substantially no light-absorbing materials.
[0159]Various embodiments described herein can provide a 2D batwing diffuser that obscures or helps obscure light sources, including but not limited to LEDs and fluorescent lamps.
[0160]Various embodiments described herein can provide a 2D batwing diffuser that increases the luminance uniformity on the surface of a luminaire.
[0161]Various embodiments described herein can provide a 2D batwing diffuser that has a visible surface pattern that may be aesthetically pleasing to a viewer. Further, various embodiments described herein can provide a 2D batwing diffuser optic that has a visible surface pattern that visually obscures light sources such as LEDs, or distracts the eye to reduce their visibility.
[0162]Various embodiments described herein can provide a 2D batwing diffuser than can be efficiently and inexpensively mass-produced in areas large enough to be suitable for use in general lighting.
[0163]Various embodiments described herein can provide a 2D batwing diffuser that reduces luminance at high viewing angles relative to a Lambertian source.
[0164]Various embodiments described herein can provide a substantially flat or slightly curved 2D batwing diffuser optic that can form light into useful 2D batwing distributions.
[0165]Various embodiments described herein can provide 2D batwing diffuser that when used with an appropriately configured specular reflector will create a one-sided distribution suitable for applications including wall-wash and/or cove lighting.
[0166]Various embodiments described herein can provide a luminaire employing a 2D batwing diffuser, the luminaire emitting light into a 2D batwing distribution.
[0167]Various embodiments described herein can provide a luminaire employing a 2D batwing diffuser optic, the luminaire emitting light into a one-sided distribution suitable for wall-wash and/or cove lighting applications.
General Description
[0168]Various embodiments described herein can provide a 2D batwing diffuser comprising a substrate having a first and second surface, the first surface having pattern elements comprising a plurality of substantially parallel, approximately linear prismatic microstructures, or prisms, said prisms having multiple orientations within the array, configured to modify the light distribution of a typical artificial light source into a 2D batwing distribution. The prisms are substantially isosceles triangular in cross-section, and may include other features such as a rounded tip and/or valley, or surface roughness. In many embodiments, the prisms are curved, and in many embodiments, some or most of the prisms form closed, concentric geometric shapes.
[0169]Various embodiments described herein are based on the insight, after the surprising failure of cone array optics to form batwing distributions, that arrays of parallel prisms having the indicated characteristics can form 2D batwing distributions from Lambertian light. In many embodiments disclosed herein, the 2D batwing diffuser does not require alignment to the light source, and can be manufactured in large areas, with parts cut to size in substantially any layout.
DETAILED DESCRIPTION OF EMBODIMENTS
[0170]Prism-like structures can be arranged on a substrate S as illustrated in FIG. 11. The prisms are created on the surface of a substrate that defines the x-y axis, and thus the line defined by their peak is always parallel to the x-y plane as defined in the figure. We choose to define the orientation of a prism to be in the x-y plane and parallel to the line making the crest of the prism. The prism orientation angle