Light transmissive structures for redistribution of light, and lighting systems including the same

Abstract

To provide lighting systems that may be used to redistribute light emitted from a light source.SOLUTION: A light transmissive structure 30 includes a light transmissive substrate 32 having a first face 34 and a second face 36 opposing each other, and an array of microprism elements 38 on the first face 34. Each microprism element 38 includes a first inclined surface disposed at a first inclined angle relative to the second face 36, and a second inclined surface disposed at a second inclined angle relative to the second face 36. The first inclined angle is less than the second inclined angle, and a peak angle between the first inclined surface and second inclined surface is in the range of about 70 degrees to about 100 degrees. The second inclined surface has a convex curvature when viewed from angles perpendicular thereto. The light transmissive structure 30 is configured to receive light from a light source 20 facing the first face 34 in a first direction and redistribute light emerging from the second face 36 in a second direction different from the first direction.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 62 / 527,573, filed June 30, 2017, entitled "LIGHT TRANSMISSIVE STRUCTURES FOR REDISTRIBUTION OF LIGHT AND LIGHTING SYSTEMS INCLUDING SAME", the entire contents of which are hereby incorporated by reference.

[0002] The present invention relates to light - transmissive structures that can be used to redistribute light emitted from a light source and lighting systems including such light - transmissive structures.

Background Art

[0003] High - efficiency LED lighting is becoming increasingly adopted. A typical LED light source emits light such that it has a Lambertian distribution with a full - width at half - maximum ( "FWHM") of about 120 degrees. LEDs combined with elements of a lighting fixture (or lighting system) such as a housing, reflector, and lens can produce a number of light distributions, including those with an FWHM as low as 1 degree. Typically, many cost - effective LEDs sold for general lighting are of the 120 - degree Lambertian variant. Many lighting fixtures (both LED and traditional), such as those found in some downlights, task lights, and troffers, have a flat outer surface. In many of these installations, a simple flat diffuser, such as a microstructured diffuser, a holographic diffuser, or a three - dimensional diffuser, is used to diffuse the LED so as to hide the appearance of the LED from the viewer and smooth the surface appearance of the lighting fixture.

[0004] When a flat diffuser is used in a lighting fixture, the combination of elements in the lighting fixture such as the light source, lens, housing, reflector, baffle, etc. used inside the lighting fixture produces a light distribution incident on the light-receiving surface of the diffuser, which is referred to herein as the source distribution. Depending on the elements used, the source distribution can have a wide range of FWHM values, including 1°, 10°, 20°, 40°, 80°, 100°, 120°, or 140°. In some cases, a wide array of 120° LEDs incident on the diffuser without much interference from other elements exhibits a source distribution close to 120°. In many cases, lighting fixtures such as can-style downlights or linear wall wash lighting fixtures can include a generally reflective inner sidewall that limits the spread of the beam angle and produces an intermediate-width source distribution such as 60°, 85°, or 100°.

[0005] In many lighting systems, the area targeted to be illuminated is much larger than the emission area of the light source. The light distribution is generally measured using a method that uses an angular measurement device similar to that described in the Illuminating Engineering Society’s (“IES”) LM-79 standard. As explained therein, the luminous intensity is measured by a photodetector as a function of the angle from the principal axis of the light source. The photodetector and / or the light source are moved relative to each other such that the photodetector measures the emitted light at the desired angles.

[0006] FIG. 1 is a polar plot showing the luminous intensity distribution of light emitted from a downward-facing light source, which in this example is a light source having a Lambertian light distribution with a 120-degree full width at half maximum (FWHM). The luminous intensity is proportional to the cosine of the angle from the nadir, which is considered to be 0° on the plot (i.e., in the downward direction). When a flat surface such as a floor is illuminated by a Lambertian light distribution, the illuminance on the floor is greatest at the nadir (directly below the fixture) and decreases monotonically for points on the floor farther from the nadir. In the lighting industry, the term "Lambertian" is also frequently used to refer to light distributions having similar qualities but different widths. That is, distributions having a peak at the nadir and decreasing monotonically at higher angles are often referred to as Lambertian. In one example, a Gaussian distribution with an 80-degree FWHM is often referred to as "Lambertian" in the lighting industry.

[0007] In lighting and other fields, it may be desirable to bend the light emitted from a light source. In a lighting application, for example, it may be desirable to take the light distribution from a downlight having an 80-degree angle and a power centered directly below the main axis of the downlight and shift the distribution so that it has an asymmetric power distribution, i.e., a power centered on one side of the downlight. This may be desirable, among other uses, to increase illumination of a target area such as a wall, sign, or surgical patient, or to improve the visibility of a display or sign from non-vertical angles. Also, it may be desirable to change the orientation of the light source to an angle centered on an angle with respect to a straight downward direction (i.e., a perpendicular to the surface located directly below the light source), then further bend the light distribution, and / or give it an asymmetric distribution.

[0008] Parallel linear prisms disposed on a flat surface, such as those provided by the Direction Turning Film made by Luminit LLC of Torrance, California, and the Image Directing Film II made by 3M Optical Systems of St. Paul, Minnesota, can be used for this purpose. However, these known linear prism products can have an undesirable quality of light emitted in the wrong direction. For example, in lighting fixtures with a 120-degree Lambertian light source, it may be desirable to bend the light towards the wall to illuminate the wall. At the same time, when viewing the fixture starting at 0 degrees (looking directly below the lighting fixture), moving away from the light, and approaching a 90-degree viewing angle away from the bending direction (far from the wall and the lighting fixture), it may be desirable to smoothly and monotonically attenuate the light remaining in the undesirable direction (i.e., away from the wall).

[0009] Figures 2 and 3 are polar plots showing the distribution of light in the bending plane, measured using a Lambertian light source with a 120° source distribution, passing through the Direction Turning Film and the Image Directing Film II, respectively. The left portion of the light distribution curve (shown by the dashed oval) of the light distribution curve shows how the bent light does not monotonically and smoothly attenuate from 0 degrees to 90 degrees away from the bending direction. Figures 4 and 5 are polar plots showing the distribution of light in the bending plane, measured using a Lambertian light source with an 80° source distribution, passing through the Direction Turning Film and the Image Directing Film II, respectively. As shown, the light does not monotonically and smoothly attenuate from 0 degrees to 90 degrees away from the bending direction, as evidenced by the "bump" on the left side of the light distribution curve within the dashed oval.

[0010] Take the light distribution from a downlight having a source distribution with an FWHM between 1 degree and 140 degrees and a power centered directly below the main axis of the downlight, and shift the distribution in the bending direction so that the distribution has an asymmetric power distribution with a smooth monotonic decrease in light from 0 degrees to 90 degrees away from the bending direction. Also, take the light distribution from an inclined downlight having a source distribution with an FWHM between 1 degree and 140 degrees and a power at a tilt angle with respect to the axis directly below the location of the downlight, and further shift the distribution in the bending direction so that the distribution has a symmetric power distribution or an asymmetric power distribution with a smooth monotonic decrease in light from 0 degrees to 90 degrees away from the bending direction. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0011] According to one aspect of an embodiment of the present invention, there is provided an optically transmissive structure including an optically transmissive substrate having opposing first and second surfaces and an array of microprism elements on the first surface. Each microprism element includes a first inclined surface disposed at a first tilt angle with respect to the second surface and a second inclined surface disposed at a second tilt angle with respect to the second surface. The first tilt angle is smaller than the second tilt angle, and the peak angle between the first inclined surface and the second inclined surface is in the range of about 70 degrees to about 100 degrees. The second inclined surface has a convex curvature when viewed at an angle perpendicular thereto. The optically transmissive structure is configured to receive light emitted from a light source facing the first surface in a first direction and redistribute the light exiting from the second surface in a second direction different from the first direction.

[0012] In one embodiment, the light emitted from the second surface has an asymmetric distribution.

[0013] In one embodiment, the first tilt angle is in the range of about 10 degrees to about 40 degrees.

[0014] In one embodiment, the second tilt angle is in the range of about 40 degrees to about 100 degrees.

[0015] In one embodiment, each of the microprism elements has a length of about 100 μm and a width of about 40 μm.

[0016] In one embodiment, the microprism elements are arranged in a grid pattern along orthogonal rows and columns on a light-transmissive substrate.

[0017] In one embodiment, the microprism elements are alternately positioned at a half period in each column.

[0018] In one embodiment, the first inclined surface is substantially flat.

[0019] In one embodiment, the light-transmissive structure includes a waveform pattern on an array of microprism elements, and the waveform pattern has a plurality of peaks and a plurality of valleys. In one embodiment, the waveform pattern has a period of 20 μm in a third direction and a period of 60 μm in a fourth direction orthogonal to the third direction.

[0020] In one embodiment, at least some of the microprism elements are bent and nested so as to substantially fill a hexagonal shape. In one embodiment, the size of the hexagonal shape is about 270 μm.

[0021] In one embodiment, the light-transmissive structure includes a plurality of hexagonal shapes including the bent and nested microprism elements.

[0022] According to one aspect of the present invention, a lighting system is provided that includes a light source and a light transmissive structure spaced apart from the light source. The light transmissive structure includes a first surface facing the light source, a light transmissive substrate having a second surface on a side opposite the first surface, and an array of microprism elements on the first surface. Each microprism element includes a first inclined surface disposed at a first inclination angle with respect to the second surface and a second inclined surface disposed at a second inclination angle with respect to the second surface. The first inclination angle is smaller than the second inclination angle, and the peak angle between the first inclined surface and the second inclined surface is in the range of about 70 degrees to about 100 degrees. The second inclined surface has a convex curvature when viewed at an angle perpendicular thereto. The light transmissive structure is configured to receive light emitted from the light source in a first direction and redistribute the light exiting from the second surface in a second direction different from the first direction.

[0023] In one embodiment, the light source has a full width at half maximum light distribution between 10 degrees and 120 degrees.

[0024] In one embodiment, the light source and the light transmissive structure are oriented such that the principal axis of the light emitted from the light source is incident on the first surface of the light transmissive structure at an angle between the perpendicular and about 45 degrees from the perpendicular.

[0025] These and other aspects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of the structure, and the combinations of parts and economies of manufacture, all of which form a part of this specification, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings. However, it should be clearly understood that the drawings are for purposes of illustration and description only and are not intended as a definition of the limits of the present invention. As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0026] The components in the following figures are shown to emphasize the general principles of the present disclosure and are not necessarily drawn to scale, although at least one of the figures may be drawn to scale. Reference numerals designating corresponding components are repeated throughout the figures, where necessary, for consistency and clarity.

Brief Description of the Drawings

[0027]

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[0028] Figure 6 schematically shows a writing system 10 according to an embodiment of the present invention. As shown, the writing system 10 includes a light source 20 and a diffuser or light transmissive structure 30 spaced from the light source 20. The light source 20 can be any suitable light source, such as one LED or a plurality of LEDs. The light transmissive structure 30 includes a light transmissive substrate 32 having a first surface 34 and a second surface 36 on a side opposite the first surface 34. A plurality of microprism elements (or microprisms) 38 are on the first surface 32. Further details of embodiments of the microprisms 38 are described below.

[0029] The light transmissive structure 30 can be suspended under the light source 20 by any technique known in the art, such as using an enclosure such as a cable, a side or edge frame, or a housing. As shown, the light source 20 and the light transmissive structure 30 are attached to a housing 40. Although a single housing 40 is shown, it is contemplated that the light source 20 and / or the light transmissive structure 30 can be attached within a sub-housing that is attached to the housing 40. The housing 40 is configured to hold the light source 20 and the light transmissive structure 30 at a desired spacing and orientation relative to each other such that the maximum intensity of the light is incident on the first surface 34 of the light transmissive substrate 32 at a desired angle and the light source 20 emits light. As will be described in more detail below, the light transmissive structure 30 is configured to "bend" the light such that the light emerging from the second surface 36 has a major axis different from the major axis of the light emitted from the light source 20.

[0030] FIG. 7 shows an embodiment of the array 50 of microprisms 52 of the light transmissive structure 30 of FIG. 6. As shown, each microprism 52 includes a first surface 54 that is substantially flat and has an inclination angle 55 of about 40 degrees, and a second surface 56 that has an inclination angle 57 of about 70 degrees. The peak angle 59 between the first surface 54 and the second surface 56 is about 70 degrees. The second surface 56 has an inclination angle 57 that is greater than the inclination angle of the first surface 54 and a curvature that is convex when viewed from the outside of the light transmissive structure 30 in a direction N that is perpendicular thereto. In the embodiment shown in FIG. 7, the size of each microprism 52 can be approximately 100 μm (along the y-axis) × 40 μm (along the x-axis), and the plurality of microprisms 52 can be arranged on the substrate 32 along orthogonal rows and columns. These dimensions are intended to be given by way of example only, and it should be understood that the size of the microprisms 52 can be larger or smaller. Also, the inclination angles 55, 57 and the peak angle 59 can be larger or smaller. For example, the inclination angle 55 of the first surface 54 can be in the range of about 10 degrees to about 40 degrees, the inclination angle 57 of the second surface 56 can be in the range of about 40 degrees to about 100 degrees, and the peak angle 59 can be in the range of about 70 degrees to about 100 degrees.

[0031] FIG. 8 shows an embodiment of the array 60 of microprisms 62 of the light transmissive structure 30 of FIG. 6. As shown, each microprism 62 includes a first surface 64 that is substantially flat and has an inclination angle 65 of about 40 degrees, and a second surface 66 that has an inclination angle 67 of about 70 degrees. The peak angle 69 between the first surface 64 and the second surface 66 is about 70 degrees. The second surface 66 has an inclination angle 67 that is greater than the inclination angle of the first surface 64 and a curvature that is convex when viewed from the outside of the light transmissive structure 30 in the direction N that is perpendicular thereto. In the embodiment shown in FIG. 8, the size of each microprism 62 can be approximately 100 μm (along the y-axis) × 40 μm (along the x-axis), and the plurality of microprisms 62 can be arranged on the substrate 32 along orthogonal rows and columns, and the microprisms 62 are alternately positioned at a half period in each column, as shown. These dimensions are intended to be given by way of example only, and it should be understood that the size of the microprisms 62 can be larger or smaller. Also, the inclination angles 65, 67 and the peak angle 69 can be larger or smaller. For example, the inclination angle 65 of the first surface 64 can be within the range of about 10 degrees to about 40 degrees, the inclination angle 67 of the second surface 66 can be within the range of about 40 degrees to about 100 degrees, and the peak angle 69 can be within the range of about 70 degrees to about 100 degrees.

[0032] FIG. 9 shows an embodiment of an array 70 of microprisms 72 of the light transmissive structure 30 of FIG. 6. As shown, each microprism 72 includes a first surface 74 having an inclination angle 75 of about 40 degrees and a second surface 76 having an inclination angle 77 of about 70 degrees. The peak angle 79 between the first surface 74 and the second surface 76 is about 70 degrees. The second surface 76 has an inclination angle 77 greater than the inclination angle of the first surface 74 and a curvature that is convex when viewed from the outside of the light transmissive structure 30 in a direction N perpendicular thereto. In the embodiment shown in FIG. 9, the size of each microprism 72 can be approximately 100 μm (along the y-axis) × 40 μm (along the x-axis), and the plurality of microprisms 72 can be arranged on the substrate 32 along orthogonal rows and columns, and the microprisms 72 are alternately positioned at a half period in each column as shown. These dimensions are intended to be given by way of example only, and it should be understood that the size of the microprisms 72 can be larger or smaller. Also, the inclination angles 75, 77 and the peak angle 79 can be larger or smaller. For example, the inclination angle 75 of the first surface 74 can be in the range of about 10 degrees to about 40 degrees, the inclination angle 77 of the second surface 76 can be in the range of about 40 degrees to about 100 degrees, and the peak angle 79 can be in the range of about 70 degrees to about 100 degrees.

[0033] Also, as shown in FIG. 9, the array of microprisms 70 includes a waveform pattern 78 including a plurality of peaks 78a and a plurality of valleys 78b. The waveform pattern 78 can have a period of about 20 μm in a direction parallel to the y-axis and a period of about 60 μm in a direction parallel to the x-axis. The illustrated embodiment should in no way be considered limiting, and according to embodiments of the present invention, different waveform patterns or texture patterns having different sizes can be used.

[0034] FIG. 10 shows a top view of an embodiment of an array 80 of microprisms 82 of the light transmissive structure 30, and FIG. 11 shows the array 80 of microprisms 82 in the repeating pattern 90. As shown, the lighter the color, the higher the point on the surface of the microprism 82, and the darker the color, the lower the point on the surface of the microprism 82. The microprisms 82 are bent, different in size, and nested so as to substantially fill the hexagonal shape 83. Each of the microprisms 82 has a first surface 84 disposed at an inclination angle 85 of about 40 degrees and a second surface 86 disposed at an inclination angle 87 of about 70 degrees. The peak angle 89 between the first surface 84 and the second surface 86 is about 70 degrees. The second surface 86 has an inclination angle 87 greater than the inclination angle of the first surface 84 and a curvature that is convex when viewed from the outside of the light transmissive structure 30 in the direction N perpendicular thereto. The hexagonal shape 83 can have a size (between flat surfaces) of about 270 μm and can be repeated on the surface of the substrate 32 as partially shown in FIG. 10. This dimension is intended to be given by way of example only, and it should be understood that the size of the hexagonal shape 83 can be larger or smaller. In other embodiments, the nested and bent microprisms 82 can be configured to fill a shape other than the hexagon 83. For example, in other embodiments, the nested and bent microprisms 82 can be configured to fill a square, a rhombus, or any other desired shape that can be replicated in a repeating pattern.

[0035] The light transmissive structures according to any of the embodiments described herein can be created using many techniques known in the art. For example, in one embodiment, the prism shape can be cast onto a substrate using a suitable master mold and a thermosetting polymer or an ultraviolet (UV) light curable polymer, or the shape can be impressed into a thermoplastic substrate by compression molding or other molding, or can be created simultaneously with the substrate using extrusion embossing or injection molding. The microprisms can be manufactured by replicating a master. For example, a light diffuser can be manufactured by replicating a master that encloses the desired shape, as described in U.S. Patent No. 7,190,387B2 to Rinehart et al., entitled "Systems And Methods for Fabricating Optical Microstructures Using a Cylindrical Platform and a Rastered Radiation Beam", U.S. Patent No. 7,867,695B2 to Freese et al., entitled "Methods for Mastering Microstructures Through a Substrate Using Negative Photoresist", and / or U.S. Patent No. 7,192,692B2 to Wood et al., entitled "Methods for Fabricating Microstructures by Imaging a Radiation Sensitive Layer Sandwiched Between Outer Layers", the entire disclosures of all of which are incorporated herein by reference as if fully set forth herein. The master itself can be created using the laser scanning techniques described in these patents and can be replicated to provide a diffuser using the replication techniques described in these patents.

[0036] In one embodiment, laser holography, known in the art, may be used to create a holographic pattern that creates a desired microprism in the photosensitive material. In one embodiment, projection or contact photolithography, such as that used in semiconductor, display, circuit board, and other common technologies known in the art, may be used to expose the microprisms in the photosensitive material. In one embodiment, laser ablation may be used either by using a mask or by using focused and modulated laser beams to create microprisms that include indicia in the material. In one embodiment, micromachining (also known as diamond machining), known in the art, may be used to create a desired microprism from a solid material. In one embodiment, additive manufacturing (also known as 3D printing), known in the art, may be used to create a desired microprism in a solid material.

[0037] FIG. 12 shows the in-plane distribution of light measured using a Lambertian light source with a 120-degree FWHM source distribution through a light transmissive structure 30 having an array 60 of microprisms 62 shown in FIG. 8. FIG. 12 shows a smooth monotonic decrease in light from 0 degrees to 90 degrees away from the bending direction. Further, the light transmissive structure 30 appears to give a stronger or increased bend of light as compared to the prior art films described above.

[0038] FIG. 13 shows the in-plane distribution of light measured using a light source with an 80-degree FWHM source distribution through a light transmissive structure 30 having an array 60 of microprisms 62 shown in FIG. 8. FIG. 13 shows a monotonic decrease in light from 0 degrees to 90 degrees away from the bending direction. Further, the light transmissive structure 30 appears to give a stronger or increased bend of light as compared to the prior art films described above.

[0039] FIG. 14 shows the source distribution of light emitted from a light source having a 10-degree FWHM and tilted by 10 degrees with respect to the direction extending straight down from the light source (corresponding to 0°). As shown, the distribution is generally symmetric with respect to the tilt direction.

[0040] FIG. 15 shows the light distribution in the bending plane after the source distribution of FIG. 14 has passed through the Luminit Direction Turning Film. As shown, the Luminit Direction Turning Film not only generally redistributed the light in the bending direction which is about +20° from the tilt direction, but also generally produced an unwanted secondary distribution 100 directed at an angle of about -20° from the tilt direction.

[0041] FIG. 16 shows the light distribution in the bending plane after the source distribution of FIG. 14 has passed through the light transmissive structure 30 having the array 60 of the microprisms 62 of FIG. 8. As shown, the light transmissive structure 30 redistributed the light in the bending direction which is about +20° from the tilt direction and did not produce a secondary distribution.

[0042] FIG. 17 shows the source distribution of light emitted from a light source having a 10-degree FWHM and tilted by 30 degrees with respect to the direction extending straight down from the light source (corresponding to 0°). As shown, the distribution is generally symmetric with respect to the tilt direction.

[0043] FIG. 18 shows the light distribution in the bending plane after the source distribution of FIG. 17 has passed through the Luminit Direction Turning Film. As shown, the Luminit Direction Turning Film not only generally redistributed the light in the bending direction greater than +20° from the tilt direction, but also generally produced an unwanted secondary distribution 110 directed at an angle greater than -60° from the tilt direction.

[0044] FIG. 19 shows the light distribution in the bending plane after the source distribution of FIG. 17 has passed through the light transmissive structure 30 having the array 60 of microprisms 62 of FIG. 8. As shown, the light transmissive structure 30 redistributed the light in the bending direction greater than +20° from the tilt direction and did not produce a secondary distribution.

[0045] The embodiments described herein represent several possible implementations and examples and do not necessarily limit the present disclosure to any particular embodiment. Instead, various changes may be made to these embodiments, and different combinations of the various embodiments described herein may be used as part of the invention, even if not explicitly described, as would be understood by one of ordinary skill in the art. Any such changes are intended to be included within the spirit and scope of the present disclosure and are to be protected by the following claims.

Claims

1. 1. A light-transmitting structure comprising: a light-transmitting substrate having opposing first and second surfaces; an array of microprism elements on the first surface, each microprism element comprising a first inclined surface disposed at a first inclination angle relative to the second surface and a second inclined surface disposed at a second inclination angle relative to the second surface, the first inclination angle being less than the second inclination angle, a peak angle between the first inclined surface and the second inclined surface being in a range of about 70 degrees to about 100 degrees, and the second inclined surface having a convex curvature when viewed perpendicular thereto; The optically transparent structure is configured to receive light emitted from a light source facing the first surface in a first direction and redistribute light exiting the second surface in a second direction different from the first direction.

2. The light-transmitting structure of claim 1 , wherein the light emitted from the second surface has an asymmetric distribution.

3. 10. The light-transmitting structure of claim 1, wherein the first tilt angle is within a range of about 10 degrees to about 40 degrees.

4. 10. The light-transmitting structure of claim 1, wherein the second tilt angle is within a range of about 40 degrees to about 100 degrees.

5. 10. The light-transmitting structure of claim 1, wherein each of the microprism elements has a length of about 100 μm and a width of about 40 μm.

6. The light-transmitting structure of claim 1 , wherein the microprism elements are arranged in a grid on the light-transmitting substrate along orthogonal rows and columns.

7. 7. The light-transmitting structure of claim 6, wherein the microprism elements alternate at 1 / 2 period in each row.

8. The light-transmitting structure of claim 1 , wherein the first angled surface is substantially flat.

9. 10. The light-transmitting structure of claim 1, further comprising a wavy pattern on said array of microprism elements, said wavy pattern having a plurality of peaks and a plurality of valleys.

10. 10. The light-transmitting structure of claim 9, wherein the wavy pattern has a period of 20 μm in a third direction and a period of 60 μm in a fourth direction orthogonal to the third direction.

11. The light-transmitting structure of claim 1 , wherein at least some of the microprism elements are bent and nested.

12. 12. The light-transmitting structure of claim 11, wherein the nested, bent microprism elements approximately fill a hexagonal shape.

13. 13. The light-transmitting structure of claim 12, wherein the size of the hexagonal shapes is about 270 μm.

14. The light-transmitting structure of claim 12 , wherein the light-transmitting structure comprises a plurality of hexagonal shapes comprising the bent, nested microprism elements.

15. 1. A lighting system comprising: A light source; a light-transmitting structure spaced from the light source, the light-transmitting structure comprising: a light-transmitting substrate having a first surface facing the light source and a second surface opposite the first surface; an array of microprism elements on the first surface, each microprism element having a first inclined surface disposed at a first inclination angle with respect to the second surface and a second inclined surface disposed at a second inclination angle with respect to the second surface, the first inclination angle being less than the second inclination angle, a peak angle between the first inclined surface and the second inclined surface being in a range of about 70 degrees to about 100 degrees, and the second inclined surface having a convex curvature when viewed perpendicular thereto; The light-transmissive structure is configured to receive light emitted from the light source in a first direction and redistribute light exiting the second surface in a second direction different from the first direction.

16. 16. The lighting system of claim 15, wherein the light emitted from the second surface has an asymmetric distribution.

17. 16. The lighting system of claim 15, wherein the first tilt angle is within a range of about 10 degrees to about 40 degrees.

18. 16. The lighting system of claim 15, wherein the second tilt angle is within a range of about 40 degrees to about 100 degrees.

19. 16. The lighting system of claim 15, wherein each of the microprism elements has a length of about 100 μm and a width of about 40 μm.

20. 16. The lighting system of claim 15, wherein the microprism elements are arranged in a grid along orthogonal rows and columns on the optically transmissive substrate.

21. 21. The lighting system of claim 20, wherein the microprism elements alternate at 1 / 2 a period in each row.

22. 16. The lighting system of claim 15, wherein the first angled surface is substantially flat.

23. 16. The lighting system of claim 15, wherein the light-transmissive structure further comprises a wavy pattern on the array of microprism elements, the wavy pattern having a plurality of peaks and a plurality of valleys.

24. 24. The lighting system of claim 23, wherein the wavy pattern has a period of 20 μm in a third direction and a period of 60 μm in a fourth direction orthogonal to the third direction.

25. The lighting system of claim 15 , wherein at least some of the microprism elements are bent and nested.

26. 26. The lighting system of claim 25, wherein the nested bent microprism elements approximately fill a hexagonal shape.

27. 27. The lighting system of claim 26, wherein the hexagonal shape is about 270 [mu]m in size.

28. 27. The lighting system of claim 26, wherein the light-transmissive structure comprises a plurality of hexagonal shapes comprising the bent, nested microprism elements.

29. 16. The lighting system of claim 15, wherein the light source has a full width at half maximum light distribution between 10 degrees and 120 degrees.

30. 16. The lighting system of claim 15, wherein the light source and the light-transmissive structure are oriented such that a major axis of the light emitted from the light source is incident on the first surface of the light-transmissive structure at an angle between normal and about 45 degrees from normal.

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