CN110785606A

CN110785606A - Optical coupler

Info

Publication number: CN110785606A
Application number: CN201880041257.8A
Authority: CN
Inventors: A·博斯科维奇; S·A·库奇斯基; 李沈平
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2017-04-21
Filing date: 2018-04-16
Publication date: 2020-02-11
Also published as: WO2018194973A1; TW201903444A; KR20190138685A; JP2020518098A

Abstract

The backlight unit may include a light guide plate and an optical coupler including a plurality of concentric waveguides. Each of the plurality of concentric waveguides may include an inner surface and an outer surface extending from a first edge of the waveguide to a second edge of the waveguide along an arcuate path defining a radius of the waveguide. The first edge of each of the plurality of concentric waveguides may face an outer edge of the light guide plate. The backlight unit may include a light source facing the second edge of each of the plurality of concentric waveguides. The backlight unit may further include a second light coupler between the light source and the first light coupler. An optical coupler comprising a plurality of concentric waveguides may also be provided.

Description

Optical coupler

Cross Reference to Related Applications

Priority of U.S. provisional application serial No.62/488,368, filed 2017 on 21/4/2017, which is based on its content and the content of which is incorporated herein by reference in its entirety, is claimed in this application according to 35u.s.c. § 119.

Technical Field

The present disclosure relates generally to optical couplers and, more particularly, to optical couplers that include a plurality of concentric waveguides.

Background

Display panels are known which utilize a backlight unit to illuminate an electronic display. It is also known to illuminate light guide plates and waveguides with light sources.

Disclosure of Invention

The following presents a simplified summary of the disclosure in order to provide a basic understanding of some example embodiments described in the detailed description.

In some embodiments, the optical coupler may include a plurality of concentric waveguides. Each of the plurality of concentric waveguides may include an inner surface and an outer surface extending from a first edge of the waveguide to a second edge of the waveguide along an arcuate path defining a radius of the waveguide.

In some embodiments, the backlight unit may include an optical coupler, and the first edge of each of the plurality of concentric waveguides may face an outer edge of the light guide plate.

In some embodiments, a backlight unit may include a light guide plate and a light coupler including a plurality of concentric waveguides. Each of the plurality of concentric waveguides may include an inner surface and an outer surface extending from a first edge of the waveguide to a second edge of the waveguide along an arcuate path defining a radius of the waveguide. The first edge of each of the plurality of concentric waveguides may face an outer edge of the light guide plate. The backlight unit may include a light source facing the second edge of each of the plurality of concentric waveguides.

In some embodiments, the inner and outer surfaces of each of the plurality of concentric waveguides extend equidistant from each other along an arcuate path without diverging or converging.

In some embodiments, the radius of each of the plurality of concentric waveguides may be constant.

In some embodiments, the optical coupler may further include a gap defining a distance between adjacent waveguides.

In some embodiments, the gap comprises at least one of air and a material having a refractive index that is less than a refractive index of a material of an adjacent waveguide by about 0.2.

In some embodiments, the gap may extend along the entire arcuate path between adjacent waveguides.

In some embodiments, the distance may be from about 1 micron to about 10 microns.

In some embodiments, the distance may be constant.

In some embodiments, each of the plurality of concentric waveguides may include a rectangular cross-sectional profile taken perpendicular to the arcuate path.

In some embodiments, the rectangular cross-sectional profile is constant along the entire arcuate path.

In some embodiments, a central angle defining an arc length between the first edge and the second edge of each of the plurality of concentric waveguides may be from about 90 ° to about 180 °.

In some embodiments, the central angle may be about 180 °.

In some embodiments, each of the plurality of concentric waveguides defined between the inner surface and the outer surface may have a thickness from 0.2mm to about 2.0 mm.

In some embodiments, the innermost waveguide of the plurality of concentric waveguides may have a radius from about 1mm to about 10 mm.

In some embodiments, the innermost waveguide may have a radius of about 1 mm.

In some embodiments, a backlight unit may include a light guide plate including a first major surface and a second major surface, and a first light coupler including a plurality of concentric waveguides. Each of the plurality of concentric waveguides may include an inner surface and an outer surface extending from a first edge of the waveguide to a second edge of the waveguide along an arcuate path defining a radius of the waveguide. The first edge of each of the plurality of concentric waveguides may face an outer edge of the light guide plate. The backlight unit may include a second light coupler including a first surface coupled to the second edge of each of the plurality of concentric waveguides and a second surface coupled to the light source. The height of the light emitting region of the light source may be greater than a thickness of the light guide plate defined between the first major surface of the light guide plate and the second major surface of the light guide plate.

In some embodiments, a thickness of the first optical coupler defined between an inner surface of an innermost waveguide of the plurality of concentric waveguides and an outer surface of an outermost waveguide of the plurality of concentric waveguides may be less than a height of the light emitting region of the light source.

In some embodiments, the thickness of the first optical coupler may be approximately equal to the thickness of the light guide plate.

In some embodiments, an electronic display may include a backlight unit oriented to face a major surface of a display panel.

The embodiments described above are exemplary and may be provided alone or in any combination with any one or more of the embodiments provided herein without departing from the scope of the present disclosure. Furthermore, it is to be understood that both the foregoing general description and the following detailed description present embodiments of the disclosure, and are intended to provide an overview or framework for understanding the nature and character of the embodiments as they are described and claimed. The accompanying drawings are included to provide a further understanding of the embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure and, together with the description, serve to explain the principles and operations thereof.

Drawings

These and other features, embodiments and advantages of the present disclosure may be further understood when read in conjunction with the appended drawings:

fig. 1 shows a schematic plan view of an exemplary electronic display according to an embodiment of the present disclosure;

fig. 2 illustrates a cross-sectional view of an exemplary electronic display along line 2-2 of fig. 1 including an exemplary backlight unit, according to an embodiment of the disclosure.

FIG. 3 shows an enlarged view of a region of the backlight unit identified by numeral 3 of FIG. 2 including a first optical coupler comprising a plurality of concentric waveguides, according to an embodiment of the present disclosure;

FIG. 4 illustrates a cross-sectional view of a first optical coupler along line 4-4 of FIG. 3, in accordance with an embodiment of the present disclosure;

FIG. 5 illustrates an exemplary embodiment of an area of the backlight unit of FIG. 3 including a second light coupler positioned between the first light coupler and the light source, according to an embodiment of the present disclosure;

FIG. 6 illustrates another exemplary embodiment of a region of the backlight unit of FIG. 3 including an alternate second light coupler positioned between the first light coupler and the light source in accordance with embodiments of the present disclosure;

FIG. 7 shows a plan view of an alternative second optical coupler along line 7-7 of FIG. 6;

fig. 8 illustrates an exemplary graph including waveguides of different thicknesses, where the vertical or "Y" axis represents optical loss in decibels (dB) and the horizontal or "X" axis represents waveguide radius in millimeters (mm), according to embodiments of the present disclosure; and

fig. 9 shows an exemplary graph including waveguides of different thicknesses, where the vertical or "Y" axis represents light transmission in percent (%) and the horizontal or "X" axis represents waveguide radius in millimeters (mm), according to embodiments of the present disclosure.

Detailed Description

Features will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Fig. 1 shows a plan view of an exemplary electronic display 100, according to an embodiment of the present disclosure. In some embodiments, electronic display 100 may include a display panel 110 positioned within housing 105. In some embodiments, housing 105 may protect display panel 110 and provide a structure by which electronic display 100 may be mounted, held, touched, contacted by a user and/or the environment in which electronic display 100 may be employed. In some embodiments, the housing 105 may include a bezel 115 defining an opening 116, the opening 116 laterally circumscribing at least a portion of the first major surface 111 of the display panel 110. Bezel 115 may include a bezel width "W" defined between opening 116 of housing 105 and outer surface 106. In some embodiments, as discussed more fully below, features of the present disclosure may provide, for example, a bezel width "W" that is reduced (e.g., narrower) than the bezel width of other electronic displays. Additionally, in some embodiments, features of the present disclosure may eliminate bezel width "W" and provide, for example, a bezel-less electronic display 100. Also, as discussed more fully below, features of the present disclosure may provide, for example, a housing dimension "D" (e.g., depth, thickness) that is reduced (e.g., thinner) from housing dimensions (e.g., depth, thickness) of other electronic displays. In some embodiments, consumer and market demand may desire an electronic display 100 that includes a bezel 115 that includes a narrow bezel width "W" for one or more reasons in aesthetic, mechanical, and functional terms; a frameless electronic display 100; and/or a housing 105 including a thin housing dimension "D".

Additionally, although the opening 116 is shown as rectangular, it should be understood that in some embodiments, the opening 116 may include a circular, oval, polygonal, etc. profile without departing from the scope of the present disclosure. Similarly, while bezel 115 and outer surface 106 of housing 105 are shown as planar, it should be understood that in some embodiments, at least one of bezel 115 and outer surface 106 may include non-planar features and/or non-planar profiles without departing from the scope of the present disclosure. Moreover, although display panel 110 is shown as planar, it should be understood that in some embodiments, display panel 110 may include non-planar features and/or non-planar (e.g., meandering) contours without departing from the scope of the present disclosure. In some embodiments, the bezel width "W" can be constant, and the bezel 115 can extend around the entire perimeter of at least a portion of the first major surface 111 of the display panel 110. Alternatively, in some embodiments, bezel width "W" may vary, and thus may include relatively narrower and wider portions. In some embodiments, the bezel 115 can extend around a portion of the perimeter of at least a portion of the first major surface 111. Also, in some embodiments, the housing dimension "D" may be constant for the entire electronic display 100. Alternatively, in some embodiments, housing dimension "D" may vary, and thus may include thicker and thinner portions at one or more locations of electronic display 100.

FIG. 2 shows a cross-sectional view of the electronic display 100 along line 2-2 of FIG. 1. In some embodiments, the electronic display 100 may include a backlight unit 200 oriented to face, for example, the second major surface 112 of the display panel 110. In some embodiments, the first major surface 111 of the display panel 110 may face away from the backlight unit 200, and the backlight unit 200 may illuminate the display panel 110 by providing light from the backlight unit 200 to the second major surface 112 of the display panel 110. In some embodiments, the electronic display 100 may be used as a computer monitor, a television monitor, a portable display for a cellular telephone, a tablet computer, or the like, wherein the display panel 110 may provide an electronic image (e.g., text, pictures, video, etc.), and the backlight unit 200 may illuminate the display panel 110 including the electronic image disposed on the display panel 110. For example, in some embodiments, the display panel 110 may include an LCD panel oriented to produce an electronic image that, when illuminated from behind by the backlight unit 200, may be viewed by a user facing the first major surface 111 of the display panel 110.

In some embodiments, the backlight unit 200 may include a light guide plate 210, the light guide plate 210 including a first major surface 211 and a second major surface 212. Light guide plate 210 may include an outer edge 213 extending from first major surface 211 to second major surface 212 and circumscribing first major surface 211 and second major surface 212. As discussed more fully below, in some embodiments, the backlight unit 200 may include first

light couplers

220, 221 and

light sources

225, 226. In some embodiments, the first optical coupler 220, 221 (including one or more features of the first optical coupler 220, 221) may be provided separately and thus may be considered complete. Alternatively, in some embodiments, the first

optical coupler

220, 221 may be provided in combination with one or more features of the present disclosure, and may be incorporated as an assembly, for example, of the backlight unit 200 and the electronic display 100. Additionally, in some embodiments, one first optical coupler (e.g., first optical coupler 220) and one light source (e.g., light source 225) may be provided; however, in some embodiments, more than one first optical coupler and more than one light source may be provided without departing from the scope of the present disclosure.

For example, in some embodiments, a single first optical coupler 220 may be provided along one side of the outer edge 213 of the light guide plate 210 without providing an additional optical coupler. In some embodiments, employing a single first light coupler 220 may reduce the number of components of the backlight unit 200, thereby simplifying the cost and time associated with manufacturing the backlight unit 200 and reducing the size of the backlight unit 200. For example, in some embodiments, employing a single first optical coupler 220 can reduce at least one of bezel width "W" and housing dimension "D" by allowing housing dimension "D" to be reduced (e.g., as opposed to the location of first optical coupler 220) because no optical coupler is accommodated at that location when a single first optical coupler 220 is employed. Thus, it should be understood that the features described with respect to the first optical coupler 220 and the light source 225 may be applied to the first optical coupler 221 and the light source 226, as well as other first optical couplers and other light sources not explicitly disclosed, alone or in combination and in the same or similar manner, without departing from the scope of the present disclosure.

Additionally, in some embodiments, electronic display 100 may include one or more optical components (not shown), including but not limited to reflectors, filters, films, diffusers, and the like. Also, in some embodiments, electronic display 100 may include one or more additional electronic components (shown generally as component 230), including but not limited to transducers, circuits, receivers, transmitters, power sources, batteries, memories, sensors, heat sinks, and the like, that are integrated with electronic display 100 and that are mechanically and/or electrically connected with electronic display 100. For example, in some embodiments, one or more of the components 230 may provide functionality that enables a user to interact with and control one or more features of the electronic display 100. Accordingly, it should be understood that, unless otherwise specified, the features of electronic display 100 may be used in a variety of applications, including, but not limited to, the particular applications provided as exemplary embodiments of the present disclosure as well as other applications not specifically disclosed, without departing from the scope of the present disclosure.

Fig. 3 shows an enlarged view of the area of the backlight unit 200 identified by numeral 3 of fig. 2, with features of the housing 105 and the cross-sectional line pattern removed for clarity. In some embodiments, the first optical coupler 220 may include a plurality of

concentric waveguides

300a, 300b, 300 c. Although three

concentric waveguides

300a, 300b, 300c are shown, it should be understood that in some embodiments, two, four, five, or more concentric waveguides may be provided without departing from the scope of the present disclosure. Additionally, in some embodiments, the first optical coupler 220 may include a single waveguide. In some embodiments, each

waveguide

300a, 300b, 300c (i.e., each

waveguide

300a, 300b, 300c of the plurality of concentric waveguides, i.e., each of the plurality of

concentric waveguides

300a, 300b, 300c) may include an

inner surface

301a, 301b, 301c and an

outer surface

302a, 302b, 302 c. The

inner surface

301a, 301b, 301c and the

outer surface

302a, 302b, 302c may extend from a

first edge

303a, 303b, 303c of the

waveguide

300a, 300b, 300c to a

second edge

304a, 304b, 304c of the

waveguide

300a, 300b, 300c along an

arcuate path

305a, 305b, 305c defining a radius Ra, Rb, Rc of the

waveguide

300a, 300b, 300 c. For example, the term "concentric waveguide" is intended to mean that each

waveguide

300a, 300b, 300c of the plurality of concentric waveguides can share the same center 311 (e.g., center point, central axis) defined relative to the curved (e.g., meandering, circular, partially circular, elliptical, partially elliptical) profile of each waveguide 300a, 300b, 300 c.

In some embodiments, the radii Ra, Rb, Rc may correspond to radial dimensions from the center 311 to locations on the

inner surface

301a, 301b, 301c of the

waveguide

300a, 300b, 300 c. Likewise, in some embodiments, the radii Ra, Rb, Rc may correspond to radial dimensions from the center 311 to locations on the

outer surfaces

302a, 302b, 302c of the

waveguides

300a, 300b, 300 c. Further, in some embodiments, the radii Ra, Rb, Rc may correspond to radial dimensions from the center 311 to radial locations defined between the

inner surfaces

302a, 301b, 301c and the

outer surfaces

302a, 302b, 302 c. For purposes of this disclosure, unless otherwise noted, radii Ra, Rb, Rc are intended to represent radial dimensions from center 311 to a radial midpoint location defined equidistant between

inner surface

302a, 301b, 301c and

outer surface

302a, 302b, 302c, as shown, for example, in fig. 3, 5, and 6.

In some embodiments, the

inner surfaces

301a, 301b, 301c and the

outer surfaces

302a, 302b, 302c may extend in the same direction (e.g., along

arcuate paths

305a, 305b, 305c) without diverging or converging. For example, in some embodiments, the

inner surfaces

301a, 301b, 301c and the

outer surfaces

302a, 302b, 302c may extend equidistant from one another along the

arcuate paths

305a, 305b, 305c without diverging or converging. Additionally, in some embodiments, the

inner surfaces

301a, 301b, 301c and the

outer surfaces

302a, 302b, 302c may be equidistant from each other at all points (e.g., relative to radial positions along radii Ra, Rb, Rc) along the

arcuate paths

305a, 305b, 305c and thus throughout the center angle 310. Additionally, in some embodiments, the

inner surfaces

301a, 301b, 301c and the

outer surfaces

302a, 302b, 302c may be equidistant from each other at all points (e.g., relative to radial positions along radii Ra, Rb, Rc) throughout the center angle 310 on all cross-sections parallel to section 2-2 of fig. 1. Further, in some embodiments, the radius Ra, Rb, Rc of each waveguide 300a, 300b, 300c of the plurality of concentric waveguides may be constant. For example, in some embodiments, the central angle 310 defining the arc length between the

first edge

303a, 303b, 303c and the

second edge

304a, 304b, 304c of each waveguide 300a, 300b, 300c may be about 90 ° to about 180 °. In some embodiments, the radii Ra, Rb, Rc may be constant throughout the center angle 310, wherein the radii Ra, Rb, Rc are the same value throughout the center angle 310. In some embodiments, the radii Ra, Rb, Rc may optionally be constant (e.g., the same value) throughout the center angle 310 at all cross-sections parallel to section 2-2 of fig. 1. Alternatively, in some embodiments, one or more of the radii Ra, Rb, Rc may vary at one or more locations on the central angle 310 and/or may vary at one or more locations at one or more cross-sections parallel to section 2-2 of fig. 1. In some embodiments, the central angle 310 may be about 180 °, and each

waveguide

300a, 300b, 300c may thus define a semi-circular profile (e.g., corresponding to a constant radius Ra, Rb, Rc) or a semi-elliptical profile (e.g., corresponding to a varying radius Ra, Rb, Rc). Accordingly, unless otherwise noted, it should be understood that although shown as a plurality of semi-circular

concentric waveguides

300a, 300b, 300c, in some embodiments, first optical coupler 220 may include a plurality of

concentric waveguides

300a, 300b, 300c defining various profiles in accordance with embodiments of the present disclosure without departing from the scope of the present disclosure.

As described above, in some embodiments, the first optical coupler 220 can include a constant cross-sectional profile, for example, as seen along line 2-2 of FIG. 1. In further embodiments, as described above, the cross-sectional profile of the first light coupler 220 may vary with respect to a defined position along at least one of the width and the length of the light guide plate 210. In some embodiments, if the cross-sectional profile of the first optical coupler 220 as seen along line 2-2 of fig. 1 is constant, the first optical coupler 220 including the plurality of

concentric waveguides

300a, 300b, 300c may be represented as a projection of the cross-sectional profile, such as shown in fig. 3, projected in a direction along an axis perpendicular to the plane defining the cross-section. For example, in some embodiments, the axis may be linear, and the first optical coupler 220 may be represented as a constant cross-sectional profile of the first optical coupler 220 projected along the linear axis. Alternatively, in some embodiments, the axis may be non-linear, and the first optical coupler 220 may be represented as a constant cross-sectional profile of the first optical coupler 220 projected along the non-linear axis.

In some embodiments, the

first edge

303a, 303b, 303c of each waveguide 300a, 300b, 300c of the plurality of concentric waveguides may face the outer edge 213 of the light guide plate 210. Additionally, in some embodiments, the light source 225 may face the

second edge

304a, 304b, 304c of each waveguide 300a, 300b, 300c of the plurality of concentric waveguides. The light source 225 may be oriented to provide light from the light source 225 to the

second edges

304a, 304b, 304 c. For example, in some embodiments, light source 225 may provide light from light emitting region 224 of light source 225. In some embodiments, light source 225 may include one or more Light Emitting Diodes (LEDs), a light bar, a light pole, a light array, one or more light bulbs, and/or one or more optical fibers that define at least a portion of light emitting area 224. Thus, in some embodiments, each of the plurality of

concentric waveguides

300a, 300b, 300c may guide light waves (e.g., light from the light emitting region 224 of the light source 225) from the

second edge

304a, 304b, 304c along an

arcuate path

305a, 305b, 305c through each

waveguide

300a, 300b, 300c to the

first edge

303a, 303b, 303c and into the outer edge 213 of the light guide plate 210 based at least in part on total internal reflection of the light waves within each

waveguide

300a, 300b, 300 c.

In some embodiments, the

first edge

303a, 303b, 303c of each waveguide 300a, 300b, 300c of the plurality of concentric waveguides may be coupled to the outer edge 213 of the light guide plate 210. For example, in some embodiments, the

first edge

303a, 303b, 303c of each waveguide 300a, 300b, 300c may be at least one of optically and mechanically coupled to the outer edge 213 of the light guide plate 210. Similarly, in some embodiments, the

second edge

304a, 304b, 304c of each waveguide 300a, 300b, 300c of the plurality of concentric waveguides may be coupled to the light emitting region 224 of the light source 225. For example, in some embodiments, the

second edge

304a, 304b, 304c of each waveguide 304a, 300b, 300c may be at least one of optically and mechanically coupled to the light emitting region 224 of the light source 225. In some embodiments,

first edges

303a, 303b, 303c may be optically coupled to outer edge 213 by being positioned in physical contact with (e.g., abutting) outer edge 213. Similarly, in some embodiments, the

second edges

304a, 304b, 304c may be optically coupled to the light emitting region 224 of the light source 225 by being positioned in physical contact with (e.g., abutting) the light emitting region 224.

Alternatively, in some embodiments, the

first edges

303a, 303b, 303c may be spaced a distance from the outer edge 213 and/or the

second edges

304a, 304b, 304c may be spaced a distance from the light emitting area 224. Additionally, in some embodiments, an optical medium (e.g., a transparent adhesive, an optical filter, an optical coupler, etc.) may be positioned at least one of between the light-emitting area 224 and the

second edges

304a, 304b, 304c and between the outer edge 213 and the

first edges

303a, 303b, 303c to optically couple the light-emitting area 224 to the

second edges

304a, 304b, 304c and the outer edge 213 to the

first edges

303a, 303b, 303 c. For example, in some embodiments, the backlight unit 200 may include an optically clear adhesive (not shown) that optically and mechanically couples the

first edges

303a, 303b, 303c to the outer edge 213 and the

second edges

304a, 304b, 304c to the light-emitting regions 224. In some embodiments, the optically clear adhesive may include an index of refraction matching an index of refraction of at least one of the

waveguides

300a, 300b, 300c and the light guide plate 210. In some embodiments, the

waveguides

300a, 300b, 300c may be optically coupled to at least one of the light emitting region 224 of the light source 225 and the outer edge 213 of the light guide plate 210 by providing an optically clear adhesive comprising a matched index of refraction, thereby reducing or eliminating reflection of light waves (e.g., light) into and out of the

waveguides

300a, 300b, 300c, the outer edge 213 of the light guide plate 210, and the light emitting region 224 of the light source 225. For purposes of this disclosure, "light" is considered visible light having a wavelength from 400 to 700 nanometers, unless otherwise specified. Likewise, an element (e.g., an adhesive) is considered "transparent" if greater than or equal to 85% of visible light can pass through the element.

Optically coupling the light emitting region 224 of the light source 225 to the

second edges

304a, 304b, 304c of the

waveguides

300a, 300b, 300c and optically coupling the outer edge 213 of the light guide plate 210 to the

first edges

303a, 303b, 303c of the

waveguides

300a, 300b, 300c may illuminate the

waveguides

300a, 300b, 300c based on coupled light from the light source 225 provided to the

second edges

304a, 304b, 304c and may also illuminate the light guide plate 210 based on coupled light from the

waveguides

300a, 300b, 300 c. In some embodiments, illuminating an object (e.g., waveguides 300a, 300b, 300c, and light guide plate 210) based on light provided (e.g., from light source 225) to the edge of the object (e.g.,

first edge

303a, 303b, 303c and

second edge

304a, 304b, 304c of

waveguides

300a, 300b, 300c, and outer edge 213 of light guide plate 210) may be referred to as "edge-illumination. For example, in some embodiments, based on "edge-lighting," light provided from light emitting region 224 of light source 225 may propagate through first light coupler 220 and into light guide plate 210 in a direction away from outer edge 213 to be transmitted through light guide plate 210 between first major surface 211 and second major surface 212, thereby illuminating light guide plate 210.

In some embodiments, "edge-illumination" of the light guide plate 210 may provide a backlight unit 200 having a smaller size (e.g., a thinner profile) and a lighter weight backlight unit 200 than, for example, a backlight unit positioned behind (not shown) the backlight unit and oriented to direct light onto the second major surface 212 of the light guide plate 210 for illumination by a light source (this is referred to as "backlighting"). For example, a light source located at the rear (e.g., facing the second major surface 212 of the light guide plate 210) may illuminate the backlight unit 200. However, in some embodiments, illuminating the backlight unit 200 with light sources facing the second major surface 212 of the light guide plate 210 may require more light sources to provide the same or similar illumination to the backlight unit 200 than the number of light sources provided when the backlight unit 200 is illuminated by the "edge-lit" of the light guide plate 210. Similarly, in some embodiments, illuminating the backlight unit 200 with a light source facing the second major surface 212 of the light guide plate 210 may provide a backlight unit 200 that is relatively thick relative to the thickness of the backlight unit 200 illuminated by the "edge-lit" of the light guide plate 210. Thus, in some embodiments, as a trend toward smaller, lighter, and thinner electronic displays 100 may be pursued, the "edge-lit" backlight unit 200 of the present disclosure may provide a number of advantages over, for example, backlight units that are illuminated by light sources positioned behind the light guide plate 210 and facing the second major surface 212 of the light guide plate 210, including a reduction in the housing size "D" shown in fig. 2.

Further, in some embodiments, "edge-illuminating" the light guide plate 210 with the first light coupler 220 comprising a curved or meandering profile (e.g., defined by

arcuate paths

305a, 305b, 305c) may provide a backlight unit 200 having smaller dimensions (e.g., the narrower bezel 115 shown in fig. 1 and 2) and a lighter weight backlight unit 200 than, for example, a backlight unit illuminated with light sources positioned laterally adjacent to the unit (not shown) and oriented to direct light from the light sources along linear paths into the outer edge 213 of the light guide plate 210. For example, light sources positioned laterally adjacent to the outer edge 213 of the light guide plate 210 (e.g., facing the outer edge 213 of the light guide plate 210) and outside the outer edge 213 of the light guide plate 210 may illuminate the backlight unit 200. However, in some embodiments, illuminating the backlight unit 200 with a light source facing the outer edge 213 of the light guide plate 210 may require a larger housing 105 including a wider bezel 115 to accommodate the light source. Thus, in some embodiments, by positioning the light source 225 according to embodiments of the present disclosure inside the outer edge 213 of the light guide plate 210 (e.g., below the light guide plate 210 and within the housing 105) and directing the light along the

arcuate paths

305a, 305b, 305c with the first light coupler 220 comprising a curved or meandering profile, the width "W" of the bezel 115 may be reduced or eliminated, and the light guide plate 210 may be illuminated based at least in part on the "edge illumination" of the light guide plate 210.

Thus, in some embodiments, features of the present disclosure including a first light coupler 220 comprising a curved or tortuous profile (e.g., defined by

arcuate paths

305a, 305b, 305c) may provide a backlight unit 200 and an electronic display 100 that may be one or more of the following, as compared to illumination achieved by "backlighting" with light sources facing the second major surface 212 of the light guide plate 210 and/or illumination achieved by "edge-illumination" with light sources positioned laterally adjacent to the outer edge 213 of the light guide plate 210 and outside of the outer edge 213 of the light guide plate 210: smaller, lighter, narrower and thinner than other backlight units and electronic displays. Thus, in some embodiments, as a trend toward smaller, lighter, narrower, and thinner electronic displays 100 may be pursued, the "edge-lit" backlight units 200 of the present disclosure that include a curved or tortuous profile (e.g., defined by

arcuate paths

305a, 305b, 305c) may provide several advantages over other backlight units, including reducing the housing dimension "D" shown in fig. 2, and reducing or eliminating the bezel width "W" shown in fig. 1 and 2.

Additionally, in some embodiments, the first optical coupler 220 can include

gaps

307, 308 between respective ones of the

inner surfaces

301b, 301c and respective ones of the

outer surfaces

302a, 302b of adjacent waveguides (e.g.,

adjacent waveguides

300a, 300b, and

adjacent waveguides

300b, 300 c). In some embodiments, the

gaps

307, 308 may extend along the entire arcuate path (e.g., one or more of the

arcuate paths

305a, 305b, 305c) between a respective one of the

inner surfaces

301b, 301c and a respective one of the

outer surfaces

302a, 302b of adjacent waveguides. In some embodiments, providing the

gaps

307, 308 along the entire

arcuate paths

305a, 305b, 305c may enable an increased number of

waveguides

300a, 300b, 300c to be employed and may make the bend radii Ra, Rb, Rc tighter (e.g., smaller) than, for example, providing the

gaps

307, 308 along only a portion of the

arcuate paths

305a, 305b, 305 c.

In some embodiments, the

gaps

307, 308 may include at least one of air and a material having a refractive index that is less than about 0.2 of a refractive index of a material of an adjacent waveguide (e.g.,

adjacent waveguides

300a, 300b and

adjacent waveguides

300b, 300 c). Additionally, in some embodiments, the at least one of air and a material having a refractive index that is less than a refractive index of a material of an adjacent waveguide by about 0.2 may be provided at the inner surface 301a of the waveguide 300a and the outer surface 302c of the waveguide 300 c. For example, in some embodiments, the

waveguides

300a, 300b, 300c may be made of one or more of glass (e.g., aluminosilicate, alkali aluminosilicate, borosilicate, alkali borosilicate, aluminoborosilicate, alkali aluminoborosilicate, chemically strengthened glass, thermally tempered glass, etc.), polymer (e.g., polymethylmethacrylate), or other material oriented to guide light waves (e.g., light) based, at least in part, on total internal reflection of the light waves within each

waveguide

300a, 300b, 300 c. By providing the at least one of air and a material having a refractive index that is less than the refractive index of the material of the adjacent waveguide by about 0.2, light waves within the

waveguide

300a, 300b, 300c are more likely to remain within the

waveguide

300a, 300b, 300c and less likely to diffuse out of the

waveguide

300a, 300b, 300c than, for example, if the

gap

307, 308 comprises a material having a refractive index that is about 0.2 greater than the refractive index of the material of the adjacent waveguide. Accordingly, in some embodiments, based at least in part on the total internal reflection of the light waves within each

waveguide

300a, 300b, 300c, features of the present disclosure may include improved optical transmission characteristics of the

waveguides

300a, 300b, 300c, which provide a more efficient backlight unit 200 and/or an optically brighter (e.g., illuminated) display panel 110.

Additionally, as shown in FIG. 4, which illustrates a cross-sectional view of the first optical coupler 220 along line 4-4 taken perpendicular to the

arcuate paths

305a, 305b, 305c of FIG. 3, in some embodiments, each

waveguide

300a, 300b, 300c of the plurality of concentric waveguides may comprise a rectangular cross-sectional profile. Also, in some embodiments, the rectangular cross-sectional profile of each waveguide 300a, 300b, 300c may be constant along the entire

arcuate path

305a, 305b, 305 c. For example, in some embodiments, a view of the

waveguide

300a, 300b, 300c that a rectangular profile may project along the

arcuate path

305a, 305b, 305c and taken perpendicular to the

arcuate path

305a, 305b, 305c at any location on the center corner 310 of fig. 3 may have the same (e.g., identical) features as those of the rectangular (e.g., flat panel (slab))

waveguide

300a, 300b, 300c shown in fig. 4. In some embodiments, one or

more waveguides

300a, 300b, 300c of the plurality of concentric waveguides may include a polygonal profile and/or a profile that varies at one or more locations along the

arcuate path

305a, 305b, 305c without departing from the scope of the present disclosure. Additionally, the

waveguides

300a, 300b, 300c may include a length "L" along which the

waveguides

300a, 300b, 300c extend. In some embodiments, the length "L" of the

waveguides

300a, 300b, 300c may correspond to, for example, the length or width of the outer edge 213 of the light guide plate 210. For example, in some embodiments, the length "L" of the

waveguides

300a, 300b, 300c may be selected such that the

first edges

303a, 303b, 303c of the

waveguides

300a, 300b, 300c may be optically and mechanically coupled to the outer edge 213 of the light guide plate 210 along at least one of a corresponding length or width (e.g., the entire length or width) of the light guide plate 210.

Additionally, in some embodiments, the

gaps

307, 308 may define a distance d1, d2 between a respective one of the

inner surfaces

301b, 301c and a respective one of the

outer surfaces

302a, 302b of

adjacent waveguides

300a, 300b and 300b, 300 c. That is, in some embodiments, the gap 307 may define a distance d1 between the inner surface 301b of the waveguide 300b and the outer surface 302a of the waveguide 300 a. Also, in some embodiments, the gap 308 may define a distance d2 between the inner surface 301c of the waveguide 300c and the outer surface 302b of the waveguide 300 b. In some embodiments, the

waveguides

300a, 300b, 300c may be positioned relative to each other supported by a frame (not shown) or an adhesive (not shown). In some embodiments, the distances d1, d2 may be from about 1 micron to about 10 microns; however, in some embodiments, the distances d1, d2 may be less than about 1 micron or greater than about 10 microns without departing from the scope of the present disclosure. In some embodiments, the distances d1, d2 may be constant. For example, in some embodiments, the distances d1, d2 may be constant throughout the center angle 310 relative to the radii Ra, Rb, Rc. Alternatively, in some embodiments, the distances d1, d2 may vary over the center angle 310 relative to the radii Ra, Rb, Rc, and may thus include relatively smaller and relatively larger distances at one or more locations defining the

gaps

307, 308.

Providing a plurality of

concentric waveguides

300a, 300b, 300c to the first optical coupler 220 may provide several mechanical advantages. For example, in some embodiments, a plurality of relatively thin concentric waveguides (which may have an effective thickness equal to the thickness of a relatively thick single waveguide) may include relatively less induced stress based at least in part on the bend or meander profile bend of the waveguide at an equivalent bend radius as compared to a relatively thick single waveguide. Considering a relatively thick single waveguide including a predetermined bend radius, compressive stress at the inner surface of the waveguide and tensile stress at the outer surface of the waveguide may be induced based at least in part on the bending stiffness of the waveguide and the applied bending force (e.g., moment) that bends the waveguide to assume a desired curved or meandering profile. Thus, for a predetermined bend radius, the tensile stress at the outer surface of a relatively thicker single waveguide may be greater than a comparable tensile stress at the outer surface of a relatively thinner waveguide having the same bend radius. Thus, in some embodiments, a relatively thin waveguide may be bent to include a relatively small radius while inducing equivalent tensile stress at the outer surface of the waveguide induced in a relatively thick single waveguide. Thus, providing a plurality of

concentric waveguides

300a, 300b, 300c to the first optical coupler 220 may enable the use of

waveguides

300a, 300b, 300c that include tighter (e.g., smaller) radii Ra, Rb, Rc. Thus, in some embodiments, the

waveguides

300a, 300b, 300c of the present disclosure may provide a reduced or eliminated bezel width "W" as compared to a corresponding bezel width that accommodates a single curved waveguide. Similarly, therefore, in some embodiments, the

waveguides

300a, 300b, 300c of the present disclosure may provide a reduced housing size "D" as compared to a corresponding housing size that accommodates a single curved waveguide.

Furthermore, providing a plurality of

concentric waveguides

300a, 300b, 300c to the first optical coupler 220 may provide several mechanical advantages in some embodiments. In some embodiments, while a typical convention may imply that more light may propagate through a relatively larger waveguide than the amount of light propagating through a relatively smaller waveguide, the convention may not apply when the waveguide includes a curved or meandering profile. For example, in some embodiments, a plurality of relatively thin concentric waveguides (whose effective thickness may be equal to the thickness of a relatively thick single waveguide) may propagate relatively more efficiently (e.g., with less diffusion or loss) within the curved or meandering profile of the waveguide for an equivalent bend radius (e.g., guiding light within the waveguide based on total internal reflection) than a relatively thick single waveguide. Considering a relatively thick single waveguide including a predetermined bending radius, the amount of light from the light emitting region 224 of the light source 225 may be provided to and guided within the waveguide. Because the thickness of the relatively thicker waveguide is greater than the respective thickness of each of the plurality of

concentric waveguides

300a, 300b, 300c, light may be less confined within the relatively thicker single waveguide and more confined within each of the relatively

thinner waveguides

300a, 300b, 300 c. By more effectively confining light within the plurality of relatively

thin waveguides

300a, 300b, 300c, there may be provided less loss of light (e.g., light diffusing out of the

waveguides

300a, 300b, 300c) when coupling light with the plurality of relatively thin

concentric waveguides

300a, 300b, 300c than when coupling light with a single relatively thick waveguide. Thus, in some embodiments, by providing a plurality of

concentric waveguides

300a, 300b, 300c to a first optical coupler 220 comprising a curved or meandering profile (e.g., defined by

arcuate paths

305a, 305b, 305c), improved optical coupling and guiding efficiency may be achieved as compared to a single waveguide comprising a comparable curved or meandering profile.

Thus, providing a plurality of

concentric waveguides

300a, 300b, 300c to the first optical coupler 220 may enable the use of

waveguides

300a, 300b, 300c that include tighter (e.g., smaller) radii Ra, Rb, Rc than the radius of a single waveguide in providing the same, similar, or better optical illumination of the light guide plate 210 as that provided by the single waveguide. Alternatively or additionally, providing a plurality of

concentric waveguides

300a, 300b, 300c comprising improved optical coupling and guiding efficiency compared to a single waveguide to the first optical coupler 220 may provide a relatively bright display panel 110 and may allow fewer light sources to be employed, thereby reducing cost, weight, and heat generation of the backlight unit 200. In some embodiments, based at least on improved optical coupling and guiding efficiency, the size of the

waveguides

300a, 300b, 300c of the present disclosure may be reduced relative to the size of a single relatively thick waveguide, while still providing the same, similar, or better illumination characteristics as a single relatively thick waveguide. Thus, in some embodiments, a first optical coupler 220 including multiple

concentric waveguides

300a, 300b, 300c may provide a reduced or eliminated bezel width "W" as compared to a corresponding bezel width that accommodates a single curved waveguide. Similarly, therefore, in some embodiments, the plurality of

concentric waveguides

As shown in fig. 4, in some embodiments, the thickness "ta", "tb", "tc" of each waveguide 300a, 300b, 300c defined between the

inner surface

301a, 301b, 301c and the

outer surface

302a, 302b, 302c can be from about 0.2mm to about 2.0 mm. In some embodiments, the radius (e.g., Ra) of the innermost waveguide (e.g., waveguide 300a) of the plurality of concentric waveguides may be from about 1mm to about 10 mm. In some embodiments, the radius Ra of the innermost waveguide 300a may be about 1 mm. Additionally, in some embodiments, a thickness "T" of the first optical coupler 220 may be defined between an inner surface 301a of an innermost waveguide 300a of the plurality of concentric waveguides and an outer surface 302c of an outermost waveguide 300c of the plurality of concentric waveguides. Returning to fig. 3, in some embodiments, a thickness "t" of light guide plate 210 may be defined between first major surface 211 of light guide plate 210 and second major surface 212 of light guide plate 210. In some embodiments, the thickness "t" may be from about 1mm to about 4 mm; however, in some embodiments, the thickness "t" may be less than about 1mm or greater than about 4mm without departing from the scope of the present disclosure. Further, in some embodiments, the light emitting region 224 of the light source 225 may include a height "h 1". In some embodiments, the thickness "T" of the light guide plate 210 may be equal to the thickness "T" of the first light coupler 220, and in some embodiments, the thickness "T" of the first light coupler 220 may be equal to the height "h 1" of the light emitting region 224 of the light source 225.

As shown in fig. 5, in some embodiments, the backlight unit 200 may include a second light coupler 520, the second light coupler 520 including a first surface 521 coupled to the

second edge

304a, 304b, 304c of each of the plurality of

concentric waveguides

300a, 300b, 300c, and a second surface 522 coupled to the light source 525. In some embodiments, the first surface 521 can be at least one of optically and mechanically coupled to the

second edges

304a, 304b, 304 c. In some embodiments, the light source 525 may be oriented to provide light from the light source 525 to the second surface 522. For example, in some embodiments, second surface 522 may be a light emitting region 524 that is at least one of optically and mechanically coupled to a light source 525. In some embodiments, the height "h 2" of the light emitting region 524 of the light source 525 may be greater than the thickness "t" of the light guide plate 210 defined between the first major surface 211 of the light guide plate 210 and the second major surface 212 of the light guide plate 210. In some embodiments, the height "h 2" of light emitting region 524 may correspond to the size of second surface 522 of second optical coupler 520. In some embodiments, the thickness "T" of the first optical coupler 220 defined between the inner surface 301a of the innermost waveguide 300a of the plurality of concentric waveguides and the outer surface 302c of the outermost waveguide 300c of the plurality of concentric waveguides may be less than the height "h 2" of the light emitting region 524 of the light source 525. In some embodiments, the thickness "T" of the first optical coupler 220 may correspond to the size of the first surface 521 of the second optical coupler 520. Additionally, in some embodiments, the thickness "T" of the first light coupler 220 may be approximately equal to the thickness "T" of the light guide plate 210.

Thus, in some embodiments, a relatively large light source 525 including a relatively large light-emitting region 524 may be employed, for example, as compared to the light source 225 in fig. 3, and may thus provide light from the light-emitting region 524 through the second optical coupler 520, through the first optical coupler 220, and to the light guide plate 210. In some embodiments, a relatively larger light source 525 including a relatively larger light-emitting region 524 including a height "h 2" may provide (e.g., emit) at least one of more light and brighter light than, for example, a relatively smaller light-emitting region (e.g., light source 225) including a relatively smaller light-emitting region (e.g., light-emitting region 224) including a height "h 1" that may be less than height "h 2". Thus, in some embodiments, providing the second light coupler 520 to the backlight unit 200 may provide a backlight unit 200 that is relatively brighter and more efficiently illuminated, according to embodiments of the present disclosure.

Similarly, as shown in fig. 6, the backlight unit 200 may include a second light coupler 620. For example, FIG. 7 shows a view of the second optical coupler 620 along line 7-7 of FIG. 6. In some embodiments, the second optical coupler 620 may include a first surface 621a, 621b, 621c coupled to the

second edge

304a, 304b, 304c of each waveguide 300a, 300b, 300c of the plurality of concentric waveguides (see fig. 7), and a

second surface

622a, 622b, 622c coupled to the light source 625 (see fig. 6). In some embodiments, the first surfaces 621a, 621b, 621c may be at least one of optically and mechanically coupled to the

second edges

304a, 304b, 304 c. In some embodiments, the light source 625 may be oriented to provide light from the light source 625 to the

second surfaces

622a, 622b, 622 c. For example, in some embodiments, the

second surfaces

622a, 622b, 622c may be light emitting regions 624 that are at least one of optically and mechanically coupled to the light source 625. In some embodiments, the height "h 3" of light emitting region 624 of light source 625 may be greater than the thickness "t" of light guide plate 210 defined between first major surface 211 of light guide plate 210 and second major surface 212 of light guide plate 210. In some embodiments, the height "h 3" of light emitting region 624 may correspond to the size of

second surfaces

622a, 622b, 622c of second optical coupler 620. In some embodiments, the thickness "T" of the first optical coupler 220 defined between the inner surface 301a of the innermost waveguide 300a of the plurality of concentric waveguides and the outer surface 302c of the outermost waveguide 300c of the plurality of concentric waveguides may be less than the height "h 3" of the light emitting region 624 of the light source 625. In some embodiments, the thickness "T" of the first optical coupler 220 may correspond to the size of the first surfaces 621a, 621b, 621c of the second optical coupler 620. Additionally, in some embodiments, the thickness "T" of the first light coupler 220 may be approximately equal to the thickness "T" of the light guide plate 210.

Thus, in some embodiments, as compared to the light source 225 in fig. 3, for example, a relatively large light source 625 including a relatively large light-emitting region 624 may be employed, and thus may provide light from the light-emitting region 624 through the second light coupler 620, through the first light coupler 220, and to the light guide plate 210. In some embodiments, a relatively larger light source 625 including a relatively larger light-emitting region 624 including a height "h 3" may provide (e.g., emit) at least one of more light and brighter light than, for example, a relatively smaller light source (e.g., light source 225) including a relatively smaller light-emitting region (e.g., light-emitting region 224) including a height "h 1" that may be less than height "h 3". Thus, in some embodiments, providing the second light coupler 620 to the backlight unit 200 may provide a backlight unit 200 that is relatively brighter and more efficiently illuminated, according to embodiments of the present disclosure.

Fig. 8 illustrates an exemplary graph of waveguides (e.g., one or more of

waveguides

300a, 300b, 300c) including

different thicknesses

801, 802, 803. The graph is generated for an exemplary waveguide 801 comprising a thickness of 0.2mm, an exemplary waveguide 802 comprising a thickness of 0.7mm, and an exemplary waveguide 803 comprising a thickness of 2.0mm using computer modeling and analysis techniques, in accordance with embodiments of the present disclosure. The vertical or "Y" axis represents optical loss in decibels (dB), and the horizontal or "X" axis represents the radius of the waveguide (e.g., Ra, Rb, Rc) in millimeters (mm). Thus, line 811 represents the relationship between the optical loss of waveguide 801 and the waveguide radius, line 812 represents the relationship between the optical loss of waveguide 802 and the waveguide radius, and line 813 represents the relationship between the optical loss of waveguide 803 and the waveguide radius. In some embodiments, the optical loss may be defined as a measured, perceived, or calculated difference (e.g., ratio) between the reference power and the actual power. For example, referring to fig. 3, the light emitting regions 224 of the light source 225 may provide light comprising a reference power (e.g., lumens) to the

second edges

304a, 304b, 304c of the

waveguides

300a, 300b, 300 c. Light may propagate through the

waveguides

300a, 300b, 300c and exit the

first edges

303a, 303b, 303c of the

waveguides

300a, 300b, 300c optically coupled to the outer edge 213 of the light guide plate 210 with substantial power. Thus, a measured, perceived, or calculated difference between the reference power and the actual power may define the optical loss. Thus, for example, an optical loss of zero corresponds to no difference between the reference power and the actual power, and an optical loss value greater than zero corresponds to a decrease in the actual power relative to the reference power. The closer the optical loss is to zero, the more efficient the

waveguides

300a, 300b, 300c are at guiding light.

Thus, as shown in FIG. 8, based on computer modeling and analysis techniques, near zero optical loss can be obtained at a bend radius of about 1mm for waveguide 801 (including a thickness of 0.2 mm) as shown by line 811. Also, as shown by line 812, for waveguide 802 (including a thickness of 0.7 mm), near zero optical loss can be obtained at a bend radius of about 3.5 mm. In addition, as shown by line 813, near zero optical loss can be obtained at a bend radius of about 10mm for waveguide 803 (including a thickness of 2.0 mm). Thus, based on the graph of fig. 8, the thickness, bend radius, and number of waveguides may be selected to achieve a plurality of waveguides that achieve desired optical characteristics, depending on, for example, the acceptable or desired optical loss and the desired thickness "T" of the first optical coupler 220.

Fig. 9 shows exemplary graphs of waveguides (e.g., one or more of

waveguides

300a, 300b, 300c) including

different thicknesses

901, 902, 903. In accordance with embodiments of the present disclosure, the graph is generated for an exemplary waveguide 901 comprising a thickness of 0.2mm, an exemplary waveguide 902 comprising a thickness of 0.7mm, and an exemplary waveguide 903 comprising a thickness of 2.0mm using computer modeling and analysis techniques. The vertical or "Y" axis represents light transmission in percent (%) and the horizontal or "X" axis represents the radius of the waveguide (e.g., Ra, Rb, Rc) in millimeters (mm). Thus, line 911 represents the relationship between the light transmission of waveguide 901 and the waveguide radius, line 912 represents the relationship between the light transmission of waveguide 902 and the waveguide radius, and line 913 represents the relationship between the light transmission of waveguide 903 and the waveguide radius. In some embodiments, the percentage of light transmission may be defined as a percentage of measured, sensed, or calculated actual power relative to a reference power. For example, referring to fig. 3, the light emitting regions 224 of the light source 225 may provide light comprising a reference power (e.g., lumens) to the

second edges

304a, 304b, 304c of the

waveguides

300a, 300b, 300 c. Light may propagate through the

waveguides

300a, 300b, 300c and exit the

first edges

303a, 303b, 303c of the

waveguides

300a, 300b, 300c optically coupled to the outer edge 213 of the light guide plate 210 with substantial power. Thus, the percentage of measured, sensed or calculated actual power relative to the reference power may define the percentage of light transmission. Thus, for example, a light transmission percentage of 100% corresponds to no difference between the reference power and the actual power, while a light transmission percentage value less than 100% corresponds to a reduction of the actual power relative to the reference power. The closer the percent light transmission is to 100%, the more efficient the

waveguides

300a, 300b, 300c are at guiding light.

Thus, as shown in FIG. 9, based on computer modeling and analysis techniques, a percent light transmission approaching 100% can be obtained at a bend radius of about 1mm for a waveguide 901 (including a thickness of 0.2 mm), as shown by line 911. Also, as shown by line 912, for waveguide 902 (including a thickness of 0.7 mm), a light transmission percentage of approximately 100% can be obtained at a bend radius of about 3.5 mm. In addition, as shown by line 913, for waveguide 903 (including a thickness of 2.0 mm), a light transmission percentage of approximately 100% can be obtained at a bend radius of about 10 mm. Thus, based on the graph of fig. 9, the thickness, bend radius, and number of waveguides may be selected to achieve a plurality of waveguides that achieve desired optical characteristics, depending on, for example, the acceptable or desired percentage of light transmission and the desired thickness "T" of the first optical coupler 220.

It will be understood that each disclosed embodiment may be directed to a particular feature, element, or step described in connection with the particular embodiment. It will also be understood that, although a particular feature, element, or step is described in connection with one particular embodiment, it may be interchanged or combined with alternate embodiments in various combinations or permutations that are not shown.

It is also to be understood that the terms "the", "a", or "an" as used herein mean "at least one" and should not be limited to "only one" unless specifically indicated to the contrary. Thus, for example, reference to "a component" includes embodiments having two or more such components, unless the context clearly indicates otherwise.

Ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, embodiments include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

Unless explicitly stated otherwise, any method set forth herein is in no way to be construed as requiring that its steps be performed in a specific order. Thus, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise stated in the claims or descriptions that the steps are to be limited to a specific order, it is not intended that any particular order be inferred.

Although the transitional phrase "comprising" may be used to disclose various features, elements or steps of a particular embodiment, it should be understood that alternate embodiments are implied, including those embodiments that may be described using the transitional phrase "consisting of or" consisting essentially of. Thus, for example, implied alternative embodiments to a device comprising a + B + C include embodiments in which the device consists of a + B + C, and embodiments in which the device consists essentially of a + B + C.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.

Claims

1. A backlight unit, comprising:

a light guide plate;

an optical coupler comprising a plurality of concentric waveguides, each of the plurality of concentric waveguides comprising an inner surface and an outer surface extending along an arcuate path defining a radius of the waveguide from a first edge of the waveguide to a second edge of the waveguide, the first edge of each of the plurality of concentric waveguides facing an outer edge of the light guide plate; and

a light source facing the second edge of each of the plurality of concentric waveguides.

2. The backlight unit of claim 1, wherein the inner surface and the outer surface of each of the plurality of concentric waveguides extend equidistant from each other along the arcuate path without diverging or converging.

3. The backlight unit of claim 1 or claim 2, wherein the radius of each of the plurality of concentric waveguides is constant.

4. The backlight unit according to any of claims 1-3, wherein the light coupler further comprises a gap defining a distance between adjacent waveguides.

5. The backlight unit of claim 4, wherein the gap comprises at least one of air and a material having a refractive index that is less than a refractive index of a material of the adjacent waveguide by about 0.2.

6. The backlight unit of claim 4 or claim 5, wherein the gap extends along the entire arcuate path between adjacent waveguides.

7. The backlight unit of any of claims 4-6, wherein the distance is from about 1 micron to about 10 microns.

8. The backlight unit according to any one of claims 4-7, wherein the distance is constant.

9. The backlight unit of any of claims 1-8, wherein each of the plurality of concentric waveguides comprises a rectangular cross-sectional profile taken perpendicular to the arcuate path.

10. The backlight unit of claim 9, wherein the rectangular cross-sectional profile is constant along the entire arcuate path.

11. The backlight unit according to any one of claims 1-10, wherein a central angle defining an arc length between the first edge and the second edge of each of the plurality of concentric waveguides is from about 90 ° to about 180 °.

12. The backlight unit of claim 11, wherein the central angle is about 180 °.

13. The backlight unit according to any one of claims 1-12, wherein each of the plurality of concentric waveguides defined between the inner surface and the outer surface has a thickness from about 0.2mm to about 2.0 mm.

14. The backlight unit according to any of claims 1-12, wherein an innermost waveguide of the plurality of concentric waveguides has a radius from about 1mm to about 10 mm.

15. The backlight unit of claim 14, wherein the innermost waveguide has a radius of about 1 mm.

16. An electronic display comprising the backlight unit of any one of claims 1-15, wherein the backlight unit is oriented to face a major surface of a display panel.

17. A backlight unit, comprising:

a light guide plate including a first main surface and a second main surface;

a first optical coupler comprising a plurality of concentric waveguides, each of the plurality of concentric waveguides comprising an inner surface and an outer surface extending along an arcuate path defining a radius of the waveguide from a first edge of the waveguide to a second edge of the waveguide, the first edge of each of the plurality of concentric waveguides facing an outer edge of the light guide plate; and

a second optical coupler comprising a first surface coupled to the second edge of each of the plurality of concentric waveguides and a second surface coupled to a light source, wherein a height of a light emitting region of the light source is greater than a thickness of the light guide plate defined between the first major surface of the light guide plate and the second major surface of the light guide plate.

18. The backlight unit of claim 17, wherein the inner surface and the outer surface of each of the plurality of concentric waveguides extend equidistant from each other along the arcuate path without diverging or converging.

19. The backlight unit according to claim 17 or claim 18, wherein a thickness of the first light coupler defined between the inner surface of an innermost waveguide of the plurality of concentric waveguides and the outer surface of an outermost waveguide of the plurality of concentric waveguides is less than the height of the light emitting region of the light source.

20. The backlight unit of claim 19, wherein the thickness of the first light coupler is approximately equal to the thickness of the light guide plate.

21. An electronic display comprising the backlight unit of any one of claims 17-20, wherein the backlight unit is oriented to face a major surface of a display panel.

22. An optical coupler, comprising:

a plurality of concentric waveguides, each of the plurality of concentric waveguides including an inner surface and an outer surface extending from a first edge of the waveguide to a second edge of the waveguide along an arcuate path defining a radius of the waveguide.

23. The optical coupler of claim 22, wherein the inner surface and the outer surface of each of the plurality of concentric waveguides extend equidistant from each other along the arcuate path without diverging or converging.

24. The optical coupler of claim 22 or claim 23, wherein the radius of each of the plurality of concentric waveguides is constant.

25. The optical coupler of any of claims 22-24, wherein the optical coupler further comprises a gap defining a distance between adjacent waveguides.

26. The optical coupler of claim 25 wherein the gap comprises at least one of air and a material having a refractive index that is less than a refractive index of a material of the adjacent waveguide by about 0.2.

27. An optical coupler according to claim 25 or claim 26 wherein the gap extends along the entire arcuate path between adjacent waveguides.

28. The light coupler according to any of claims 25-27, wherein the distance is from about 1 micron to about 10 microns.

29. The optical coupler of any one of claims 25-28, wherein the distance is constant.

30. The optical coupler of any one of claims 22-29, wherein each of the plurality of concentric waveguides includes a rectangular cross-sectional profile taken perpendicular to the arcuate path.

31. The optical coupler of claim 30 wherein the rectangular cross-sectional profile is constant along the entire arcuate path.

32. The light coupler of any of claims 22-31, wherein a central angle defining an arc length between the first edge and the second edge of each of the plurality of concentric waveguides is from about 90 ° to about 180 °.

33. The optical coupler of claim 32 wherein the central angle is about 180 °.

34. The light coupler according to any one of claims 22-33, wherein each of the plurality of concentric waveguides defined between the inner surface and the outer surface has a thickness from about 0.2mm to about 2.0 mm.

35. The light coupler according to any of claims 22-34, wherein an innermost waveguide of the plurality of concentric waveguides has a radius from about 1mm to about 10 mm.

36. The optical coupler of claim 35, wherein the innermost waveguide has a radius of about 1 mm.

37. A backlight unit comprising the light coupler of any of claims 22-36, wherein the first edge of each of the plurality of concentric waveguides faces an outer edge of a light guide plate.

38. An electronic display comprising the backlight unit of claim 37, wherein the backlight unit is oriented to face a major surface of a display panel.