Patent Description:
Backlights suffer from problems of non-uniform lighting. The non-uniform lighting can be caused by insufficient light incident on a light guide panel (LGP) of the backlight, or hot (very bright) and dark spots caused, at least partially, by an angle at which the light is incident on the LGP. These problems cause display devices to provide images with an unintended bright or dark spot. A related prior art has been described in <CIT>, <CIT>, and <CIT>.

The figures show various views of an apparatus, including a lens that can shape light emerging from one or more light emitting diodes (LEDs), in accordance with some embodiments. In the views presented herein, it is assumed that light emerges from a front of the lens, such that the LED or LEDs can be positioned toward a rear of the lens. The terms "front," "rear," "top," "bottom, "side," are to be understood relative to one another with "front" and "rear" opposing each other, "top" and "bottom" opposing each other, and "side" between "top" and "bottom. " Other directional terms are used merely for convenience in describing the lens and other elements and should not be construed as limiting in any way.

Corresponding reference characters indicate corresponding parts throughout the several views. Elements in the drawings are not necessarily drawn to scale. The configurations shown in the drawings are merely examples and should not be construed as limiting the scope of the disclosed subject matter in any manner.

<FIG> shows a backlight unit <NUM> comprising a planar light guide <NUM> disposed over a protection plate <NUM>, and a light emitting element <NUM> disposed on a side of the light guide <NUM>. Some light <NUM> entering the light guide <NUM> from the light emitting element <NUM> is reflected towards a top surface <NUM> of the light guide <NUM> by a patterned bottom surface <NUM> and another optional reflection sheet positioned between the light guide <NUM> and backplate <NUM> and exits from the light guide <NUM>. Light <NUM> that exits provides backlight to a display <NUM> (e.g., a liquid crystal display (LCD)) on an opposite side of the light guide <NUM> as the reflection sheet <NUM>. The reflection sheet <NUM> is separated from the bottom surface <NUM> by a an air gap <NUM>. The reflection sheet <NUM> can include a polarization maintaining surface, such as a mirror. The reflection sheet <NUM> can include a scattering surface (e.g., a white painted surface). The pattern can be printed or molded on the surface <NUM>, for example.

<FIG> shows a backlight unit <NUM> comprising a planar light guide <NUM> disposed over a protection plate <NUM>. The planar light guide <NUM> is similar to the light guide <NUM> of <FIG> with a patterned top surface <NUM> instead of a patterned bottom surface <NUM>.

In some embodiments, the light emitting element <NUM> can be a rectangular single line array or multiple line array. In other embodiments, the light emitting element <NUM> can be formed or otherwise fabricated in a shape approximating a nonrectangular (e.g., circular or oval) shape. Light emitting elements, such as light emitting diodes (LEDs) can be of a single or multiple colors, or in some embodiments red, green, blue (RGB) arrays. Different color pixels can be interleaved, or in other embodiments, the different color pixels can have other groupings in which groups of one color are disposed together in one or both orthogonal directions. In other embodiments at least some of the sets of light emitting elements can provide different wavelengths of light for color tuning. For example, one set of light emitting elements can provide white light while the other set of light emitting elements may provide red light. The light emitting elements can be formed from a II-VI, III-V, or other compound semiconductor that may be a binary, ternary, quaternary, or other compound. For example, gallium nitride (GaN) is used for blue LEDs, gallium arsenide (GaAs) for infrared (IR) LEDs, and indium gallium phosphide (InGaP), indium gallium aluminum phosphide (InGaAlP), or indium gallium arsenic phosphide (InGaAsP) for visible LEDs, among others. Alternatively, a wavelength converting structure may be disposed in the path of light extracted from the LED. The wavelength converting structure includes one or more wavelength converting materials which may be, for example, conventional phosphors, organic phosphors, quantum dots, organic semiconductors, II-VI or III-V semiconductors, II-VI or III-V semiconductor quantum dots or nanocrystals, dyes, polymers, or other materials that luminesce. The wavelength converting material includes light scattering or light diffusing elements, such as titanium dioxide (TiO2), absorbs light emitted by the LED, and emits light of one or more different wavelengths. The light provided by the light source may be white, polychromatic, or monochromatic.

<FIG> shows a cross-section of a display device <NUM> that includes a backlight. The display device <NUM> includes the display <NUM>, the light guide <NUM>, and the light emitting element <NUM>. The display <NUM> can include an LCD screen in accordance with some embodiments. The LCD screen can be part of a television, a computer monitor, a smartphone screen, a watch screen, calculator screen, or other screen.

The light emitting element <NUM> transmits light towards the light guide <NUM>. The light emitting element <NUM> can include a light emitting diode (LED), a cold-cathode fluorescent lamp (CCFL), or the like. Theoretically, the light emitting element <NUM> can produce light with a Lambertian or near Lambertian distribution. The light emitting element <NUM> can generate light of generally any practical wavelength or color.

The display device <NUM> further includes a backplate <NUM>, reflector sheets <NUM>, <NUM>, a top coating <NUM>, a side coating <NUM>, and a substrate <NUM>. The backplate <NUM> provides protection from an external environment for the reflector sheets <NUM>, <NUM>, the light emitting element <NUM>, the substrate <NUM>, the light guide <NUM>, and a surface <NUM> of the display <NUM> facing the light guide <NUM>. The backplate <NUM> can be made of metal, ceramic, polymer, or the like. An extent that the backplate <NUM> extends over the top surface <NUM> of the light guide <NUM> is sometimes called a bezel. The top coating <NUM>, the side coating <NUM>, and the light emitting element <NUM> can be parts of an LED.

The reflector sheet <NUM>, <NUM> can be made of a light scattering material, highly reflective material, or a material that is both light scattering and highly reflective. The reflective material can reflect <NUM>%, <NUM>%, <NUM>%, more or less light, or some value therebetween, of the light incident thereon.

The top surface <NUM> (surface of the light guide <NUM> facing the display <NUM>) or bottom surface <NUM> (surface of the light guide <NUM> facing away from the display <NUM>) can be patterned to help scatter the light or reflect the light to a specified location.

The top coating <NUM> can alter a color of the light from the light emitting element <NUM>. For example, if the top coating <NUM> is phosphor, the light emitted from the light emitting element <NUM> can appear whiter to the human eye. This is because phosphor absorbs some of the blue light emitted from the light emitting element <NUM>.

The side coating <NUM> can be made of a wide scattering, highly reflective material (e.g., above <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or some percentage therebetween of reflection at the wavelength of the light emitting element <NUM>). The side coating <NUM> helps the light emitting element <NUM> avoid producing hot spots. The side coating <NUM> helps reduce ingress of light to the light emitting element <NUM>. The side coating <NUM> can also help ensure that more light is transmitted through the top coating <NUM> or towards the light guide <NUM>. Examples of side coating materials include filled silicon, acrylic, a white plastic, or other dielectric coating.

The substrate <NUM> can provide power and circuit routing for the light emitting element <NUM>. The light emitting element <NUM> can be electrically and mechanically connected to electrical power through a trace or other electrical interconnect on or in the substrate <NUM>. The substrate can include a flex or rigid printed circuitry board (PCB). A flex PCB can be made of polyimide, polydimethylsiloxane, or the like. A rigid PCB can be made of FR-<NUM>, prepreg, or the like.

The light guide <NUM> is designed to spread the light from the light emitting element <NUM> as uniformly as possible across the display <NUM>. However, the backlight unit <NUM> of <FIG>, backlight unit <NUM> of <FIG>, and the display device <NUM> of <FIG> are known from the prior art to suffer from issues of diffraction inefficiencies. The diffraction pattern on the light guide surface <NUM> has a higher diffraction efficiency with more efficient at providing light with input light provided at a higher angle. The coupling of light from the light guide <NUM> to the display <NUM> is based on the reflective to transmissive diffraction pattern on the input surface <NUM> and transmission surface <NUM>, respectively. Higher in-coupling angles from the surface <NUM> provide more efficient outcoupling from the light guide <NUM> at the transmission surface <NUM>. Example embodiments provide a solution to increase the angle of incidence of a majority of the light entering the light guide <NUM>.

<FIG> illustrates, by way of example, a diagram of an embodiment of the inventive backlight apparatus <NUM> or "display device" that does not suffer from the same issues as the prior art display devices <NUM>, <NUM>, <NUM>. Here, the terms "backlight apparatus" and "display device" are used interchangeably. The display device <NUM> has some similarities to the display device <NUM>, but has been modified to include a lens <NUM>.

The lens <NUM> focuses light incident thereon. The light incident on the lens <NUM> can include light (a) directly from the light emitting element <NUM> and/or (b) reflected from the coating <NUM> to the lens <NUM>. The focus provided by the lens <NUM> directs light into two at least partially collimated beams, such as collimated or semi-collimated beams, represented by arrows <NUM>, <NUM>. The lens <NUM> can be symmetric about a plane of symmetry <NUM>. The directing of the light is provided by a contour of a receiving surface <NUM> and a contour of an opposing transmission surface <NUM> of the lens <NUM>. The receiving surface <NUM> is a surface of the lens <NUM> facing the light emitting element <NUM>. The transmission surface <NUM> of the lens <NUM> faces the light guide panel <NUM>. The transmission surface <NUM> opposes the receiving surface <NUM>. Light from the light emitting element <NUM> enters the lens <NUM> through the receiving surface <NUM> and exits the lens <NUM> through the transmission surface <NUM>.

According to the invention, an angle of a center axis of the first collimated light beam <NUM> is greater than <NUM>° from the plane of symmetry <NUM> of the lens <NUM>, and an angle of a center axis of the second collimated light beam <NUM> is greater than negative <NUM>° from the plane of symmetry <NUM> of the lens <NUM>. In other words, the center axes of the first and second collimated light beams <NUM>, <NUM> subtend an angle of at least <NUM>°, and the first and second collimated light beams <NUM>, <NUM> are symmetrical about the plane of symmetry <NUM> of the lens <NUM>.

The receiving surface <NUM>, as illustrated, is generally symmetric about the plane of symmetry <NUM>. The plane of symmetry <NUM> bisects the receiving surface <NUM> at point <NUM>. Each of the symmetric portions of the lens <NUM> include a concave portion <NUM>. Convex and concave are to be understood to be relative to the component emitting light to the lens <NUM>. In this case, concave and convex are relative to the transmission surface of the light emitting element <NUM>.

The concave portion <NUM> redirects light towards the plane of symmetry <NUM> of the lens <NUM>. The concave portion <NUM> redirects light incident thereon further from the plane of symmetry <NUM> more than it redirects light incident thereon closer to the plane of symmetry. This is due to an angle of curvature of the concave portion <NUM> being smaller closer to the plane of symmetry <NUM> than when it is farther from the plane of symmetry <NUM>. In other words, an angle of curvature of the concave portion <NUM> increases farther from the plane of symmetry <NUM>. The concave portion <NUM> redirects light to be part of the beams represented by the arrows <NUM>, <NUM>.

In example embodiments, the lens <NUM> transmits light within a first range of transmission angles [-<NUM>°, <NUM>°] out of the lens <NUM> without becoming part of the beams represented by arrows <NUM>, <NUM>. The transmission angles are relative to the plane of symmetry <NUM>. A majority of the light transmitted within a second range of transmission angles of [<NUM>°, <NUM>°] can be collimated into the beam corresponding to arrow <NUM>. The angle of the beam can be at about <NUM>° - <NUM>° from the plane of symmetry <NUM> of the lens <NUM>. A majority of the light transmitted within a third range of transmission angles [-<NUM>°, -<NUM>°] can be collimated into the beam corresponding to arrow <NUM>. The angle of the beam can be at about -<NUM>° to - <NUM>° from the plane of symmetry <NUM>. The angles are illustrated in intensity diagrams of <FIG>, which will be discussed in more detail below.

The shape of the light emitted from the lens <NUM> can include a batwing intensity profile in a vertical intensity slice perpendicular to the plane of symmetry <NUM> (see <FIG>). The shape of the light emitted from the lens <NUM> can include a collimated beam in a horizontal intensity slice (see <FIG>). The intensity profiles can be from a generally Lambertian source.

<FIG> illustrate, by way of example, perspective-view diagrams of the lens <NUM>. The perspective of <FIG> is looking straight down at the transmission surface <NUM>. The perspective view of <FIG> is looking at the lens <NUM> from the arrow labelled "<NUM>" in <FIG>. The perspective view of <FIG> is looking at the lens <NUM> from the arrow labelled "<NUM>" in <FIG>. The perspective view of <FIG> is looking at the lens <NUM> from the arrow labelled "<NUM>" in <FIG>. Items in dashed lines are normally occluded in the perspective of the corresponding FIG.

The lens <NUM>, as illustrated, includes the receiving surface <NUM> and the transmission surface <NUM>. The lens <NUM> can include two feet <NUM>. The feet <NUM> can be rectangular in perimeter. The feet <NUM> can provide a flat surface that provides stability to the lens <NUM>. The feet <NUM> can form the base of the lens <NUM> (e.g., a surface on which the lens <NUM> is meant to sit). The feet <NUM> can be in contact with or attached to a structure around the lens <NUM>, such as a portion of the light emitting element <NUM>. The lens <NUM> can be symmetric about a plane of symmetry <NUM>.

The lens <NUM> includes sides <NUM> and <NUM> extending between the transmission surface <NUM> (the transmission surface <NUM> is occluded in the view of <FIG>) and the receiving surface <NUM> and between the transmission surface <NUM> and the feet <NUM>. The sides 446A, 448A and 446B, 448B, when situated in the backplate <NUM> and over the light emitting element <NUM>, are situated on top and bottom of each other. The sides 446A, 448A, when situated in the backplate <NUM> are more proximate to the reflector sheet <NUM> or the top surface <NUM> of the light guide <NUM> than the sides 446B, 448B. The sides 446B, 448B, when situated in the backplate <NUM> are more proximate to the reflector sheet <NUM> or the bottom surface (the surface opposing the top surface <NUM>) of the light guide <NUM> than the sides 446A, 448A.

The sides 446A, 448A include a lowercase "r" shaped profile and the sides 446B, 448B include backwards lowercase "r" shaped profile (see <FIG>, for example). The forward and backwards lower case "r" shapes meet at the plane of symmetry <NUM>. The sides 446A, 446B and 448A, 448B meet to form an inner surface that includes a parabolic perimeter.

Top edges 774A, 774B, of the sides 446A, 446B, 448A, 448B, can include respective, symmetric concave shapes (relative to the light emitting element <NUM> and about the plane of symmetry <NUM>). The top edge 774A, 774B forms a contour of the transmission surface <NUM>. The top edge 774A, 774B can include a greater angle of curvature closer to the plane of symmetry <NUM> and a lesser angle of curvature farther form the plane of symmetry <NUM>. The angle of curvature can gradually change from the plane of symmetry <NUM> to an outer edge 770A, 770B.

The outer edge 770A, 770B of the sides 446A, 446B, 448A, 448B can include a concave shape relative to the plane of symmetry <NUM>. The outer edge 770A, 770B can include an angle of curvature that is greater at the feet <NUM> than at the top edge 774A, 774B. The angle of curvature can gradually change from the feet <NUM> to the outer edge 770A, 770B.

The sides 446A, 4446B, 448A, 448B can be tilted from the top edge 774A, 774B towards a center <NUM> of the lens <NUM>. The top edges 774A, 774B can combine to form a portion of the perimeter of the transmission surface <NUM>.

Sides 450A, 450B can extend between an edge of the top surface <NUM> to the feet <NUM>. The sides 450A, 450B can further extend between the sides 446A, 448A and the sides 446B, 448B, respectively. The sides 450A, 450B can be tilted from the top edge 774A, 774B towards a center <NUM> of the lens <NUM>.

<FIG> illustrates, by way of example, a diagram of an embodiment of the lens <NUM> that includes a perimeter <NUM> of the transmission surface <NUM> and a perimeter <NUM> of the opposing surface that includes an exposed outer surface of the feet <NUM>. The perimeter <NUM> can be rectangular and smaller than the perimeter <NUM>. The perimeter <NUM> can include opposing linear edges 884A, 884B that extend between opposing edges 886A, 886B. The perimeters <NUM> and <NUM> encompass what are sometimes called major surfaces of the lens <NUM>. The perimeters <NUM> and <NUM> encompass opposing major surfaces of the lens <NUM>.

The sides <NUM>, <NUM> (see <FIG>) can extend from an edge 886A, 886B of the perimeter <NUM> to an edge 888A, 888B of the perimeter <NUM>. The sides <NUM>, <NUM> can thus tilt away from the center <NUM> as they extend from the edge 888A, 888B towards the edge 886A, 886B.

The sides 450A, 450B (see <FIG>) can extend from an edge 884A, 884B of the perimeter <NUM> to an edge 890A, 890B of the perimeter <NUM>. The sides 450A, 450B can thus tilt away from the center <NUM> as they extend from the edge 884A, 884B towards the edge 890A, 890B.

<FIG> illustrates, by way of example, a perspective-view diagram of an embodiment of a portion of the display device <NUM> of <FIG>. The portion illustrated in <FIG> includes the lens <NUM> mounted on a housing <NUM> around the light emitting element <NUM>. The housing <NUM> can protect the light emitting element <NUM> from an external environment, such as debris or other light external to the housing <NUM>. The housing <NUM> can include an aperture <NUM> through which light can be transmitted from the light emitting element <NUM> to the lens <NUM> (e.g., a receiving surface <NUM> of the lens <NUM>). The housing <NUM> can include the coating <NUM> on internal surfaces (e.g., surfaces facing the light emitting element <NUM>) thereof.

The lens <NUM> can be adhered to the housing <NUM>, such as by an adhesive. In some embodiments, the lens <NUM> is integrally formed with the housing <NUM>, such as by injection molding, three-dimensional (3D) printing, or the like.

The light-emitting element <NUM> can be oriented to emit the visible light in an angular distribution. Light directly from the light-emitting element <NUM> and light from the light emitting element <NUM> reflected off the coating <NUM> can be incident on the receiving surface <NUM> of the lens <NUM>. The lens <NUM> can receive the light directly from the light emitting element <NUM> and reflected from the coating <NUM>, and emit light (represented by arrows <NUM>, <NUM>) in a batwing configuration.

<FIG> illustrates, by way of example, a plot of intensity versus angle for light emitted through the lens <NUM>. In the plot of <FIG>, the light emitting element <NUM> produces light at about a <NUM>° angle (same as -<NUM>°) towards an origin of the plot. The light from the transmission surface <NUM> is emitted in a batwing configuration with collimated beams at about between [<NUM>°, <NUM>°] and [-<NUM>°, -<NUM>°] degrees.

<FIG> illustrates, by way of example, another plot of intensity versus angle for light emitted through the lens <NUM>. In the plot of <FIG>, the light emitting element <NUM> produces light at the same spot as in the plot of <FIG>, with the view of <FIG> being from the direction directly opposing the arrow <NUM>, <NUM>. <FIG> is a slice intensity profile on a plane perpendicular to one of the peaks in <FIG>. The plot in <FIG> shows that the beams emitted by the lens <NUM> are collimated.

As used herein, the phrase generally planar is intended to mean planar to within typical manufacturing tolerance and/or typical alignment tolerances. For the purposes of this document, the use of the term visible light can be generalized to light having a first range of wavelengths.

The circuit board <NUM> can be at least partially coated with a coating that is reflective for visible light. The coated portion of the circuit board <NUM> can reflect visible light to the lens <NUM>.

<FIG> illustrates, by way of example, a flow diagram of an embodiment of a method <NUM> for forming an improved backlight. The method <NUM> can be used to form any of the apparatuses of <FIG>, among other apparatuses. The method <NUM> is but one method for forming a light-emitting apparatus; other suitable methods can also be used.

The method <NUM> as illustrated includes obtaining a lens, such as the lens <NUM>, at operation <NUM>; mechanically coupling the lens to a housing that contains a light emitting element, such as the light emitting element <NUM>, at operation <NUM>; and coupling the light emitting element to a circuit board, such as the substrate <NUM>, at operation <NUM>. The method <NUM> can include situating a light guide panel <NUM> to receive light emitted by the lens and to distribute the light towards a liquid crystal display screen.

While embodiments of the present disclosed subject matter have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art, upon reading and understanding the material provided herein.

Claim 1:
A backlight apparatus (<NUM>), comprising:
a planar light guide panel (<NUM>) configured to distribute light to a surface (<NUM>) of the planar light guide panel (<NUM>) facing a liquid crystal display screen (<NUM>);
a backplate (<NUM>);
a light emitting element (<NUM>) located within the backplate (<NUM>) and configured to emit visible light; a lens (<NUM>) located within the backplate (<NUM>) and configured to angularly redirect the visible light into a batwing configuration of first and second collimated light beams (<NUM>, <NUM>), the lens (<NUM>) including a concave receiving surface (<NUM>) facing the light emitting element and a transmission surface (<NUM>) opposing the receiving surface (<NUM>), the transmission surface (<NUM>) including an angle of curvature that increases closer to a plane of symmetry (<NUM>) of the lens, such that an angle of a center axis of the first collimated light beam (<NUM>) is greater than <NUM>° from the plane of symmetry (<NUM>) of the lens (<NUM>), and an angle of a center axis of the second collimated light beam (<NUM>) is greater than negative <NUM>° from the plane of symmetry (<NUM>) of the lens (<NUM>); and
wherein the planar light guide panel (<NUM>) is configured to distribute light from the first and second collimated light beams (<NUM>, <NUM>) to the surface (<NUM>) of the planar light guide panel (<NUM>).