Patent ID: 12204130

DETAILED DESCRIPTION OF THE INVENTION

Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the system generally shown in the preceding figures. It will be appreciated that the system may vary as to configuration and as to details of the parts without departing from the basic concepts as disclosed herein. Furthermore, elements represented in one embodiment as taught herein are applicable without limitation to other embodiments taught herein, and in combination with those embodiments and what is known in the art.

A wide range of applications exists for the present invention in relation to the collection and distribution of electromagnetic radiant energy, such as light, in a broad spectrum or any suitable spectral bands or domains. Therefore, for the sake of simplicity of expression, without limiting generality of this invention, the term “light” will be used herein although the general terms “electromagnetic energy”, “electromagnetic radiation”, “radiant energy” or exemplary terms like “visible light”, “infrared light”, or “ultraviolet light” would also be appropriate.

It is also noted that terms such as “top”, “bottom”, “side”, “front” and “back” and similar directional terms are used herein with reference to the orientation of the Figures being described and should not be regarded as limiting this invention in any way. It should be understood that different elements of embodiments of the present invention can be positioned in a number of different orientations without departing from the scope of the present invention.

Various embodiments of the invention are directed to shaped light guide illumination devices and systems that employ an edge-lit light guiding sheet which is curved about at least one axis. For example, such curved light guiding sheet may be formed into the shape of a partial cylindrical trough with an arc-shaped transversal cross-section. The trough may have a transversal cross-sectional profile that can be approximated by a portion of a conical section (e.g., a circle, an ellipse, a parabola, or a hyperbola). The trough may have a constant of variable radius of curvature across its surface and may further have planar sections.

The light guide may be formed by a rigid sheet or slab of an optically transmissive, dielectric material, such as glass, PMMA or polycarbonate, for example. The light guide may also be formed by a relative thin sheet of the transmissive material that is flexible. The term “flexible”, as applied to sheet-form structures (including flexible sheet-form substrates and/or layers), is generally directed to mean that such structures are capable of being noticeably flexed or bent with relative ease without breaking. It is noted that, while flexible sheet-form structures are in contrast to the ones that are rigid or unbending, the material of a sheet-form structure does not need to be soft or pliable in order to make such sheet-form structure flexible. Accordingly, the term “flexible” is directed to also include semi-rigid structures and structures that are formed by relatively hard, rigid materials such as metals, glass or rigid plastics, when such structures have sufficiently low thickness compared to at least one their major dimension (e.g., length or width) and allow for noticeable flexing without breaking.

The present invention will now be described by way of example with reference to the accompanying drawings.

FIG.1schematically shows an embodiment of a shaped edge-lit light guide illumination device900having a rectangular sheet-form configuration and at least one curvature about an axis. Shaped illumination device900includes a curved light guide4, an elongated, linear light source10, a concave back reflector30, and a plurality of light extraction elements6distributed over a wide area of light guide4.

Light guide4is formed by a flexible rectangular sheet of highly transmissive material. The flexible sheet is bent to a curved shape so it defines a concave broad-area surface20and an opposing convex broad-area surface40extending parallel to surface20. The flexible sheet further defines four edges12,14,16, and18connecting the opposing broad-area surfaces and flanking the solid, transparent body of the light guide. Concave broad-area surface20is configured for light output and may further be configured for light input. Opposing convex broad-area surface40extends parallel to surface20and is configured for both light input and output.

Edge12is configured for light input. Light guide4is configured to guide light from light input edge12to opposing edge14in response to optical transmission and reflection from opposing broad-area surfaces20and40by means of TIR. Light guide4is gently curved about an axis that is parallel to light input edge12and perpendicular to a direction of the intended light propagation in the light guide. Similarly, reflector30may be formed from a flexible sheet-form material and curved to the same shape as light guide4.

The curved shape of light guide4may be characterized by a radius of curvature Rcin the respective plane of the bend. On the other hand, it may also be characterized by a length L of a curved segment representing such curved shape in a transversal cross-section in a plane that is perpendicular to light input edge12.

Radius of curvature Rcmay be constant across the area of light guide4and may be measured at any point of surfaces20or40. It may also be made variable across the light guide's area and may be measured at the respective locations of surfaces20or40. Rcis preferably greater than 5 times the thickness of the light guide, more preferably greater than 10 times, and even more preferably greater than 20 times the thickness of light guide4at each point of surfaces20and40. On the other hand, at least a portion of light guide4has radius of curvature Rcthat is less than a certain maximum value. According to some embodiments, such maximum value may be defined by length L. According to one embodiment, radius Rcis less than 3 times length L. According to one embodiment, radius Rcis less than 2 times length L. According to one embodiment, radius Rcis less than 1.5 times length L. According to one embodiment, radius Rcis less than 1.3 times length L. According to one embodiment, radius Rcis less than length L.

Reflector30is formed by an opaque sheet of a flexible and highly reflective material. Reflector30is positioned adjacent to convex surface40of light guide4so that its concave reflective surface is facing the light guide and generally conforms to the curved shape of the light guide. According to one embodiment, reflector30may be of a specular type. For example, it may include a mirrored surface reflecting light by means of specular reflection. According to one embodiment, reflector30may be of a diffuse type. For example, it may include a diffuse high-reflectance coating, such as white paint or white-powder coating containing titanium dioxide. According to one embodiment, reflector30may be configured to reflect in both specular and diffuse regimes. For example, reflector30may have a mirrored surface which includes surface corrugations, waviness or microstructure that causes the reflected rays to spread over a limited angular range. For instance, reflector30may be configured to reflect an incident parallel beam of light into a cone of reflected light having a fixed angular spread (e.g., 10°, 20°, 30°, and so on).

The desired light-diffusing power of reflector30may also be defined based on a Full Width Half Maximum (FWHM) angle characterizing such diffusely reflected beam. According to one embodiment, the surface of reflector30is configured to reflect light at FWHM angle that is less than 60°. According to one embodiment, the FWHM angle is less than 30°. According to one embodiment, the FWHM angle is less than 20°. According to one embodiment, the FWHM angle is less than 10°.

The desired reflective characteristics of reflector30may also be defined based on proportions between secularly and diffusely reflected light. According to various embodiments, a ratio between the light energy reflected in a specular regime to the light energy reflected in a diffuse regime is any one of the following: 0.2, 0.4, 0.5, 0.6, 0.7, and 0.8.

While surface40is ordinarily transparent, it may also be mirrored or made diffusely reflective as an alternative to employing reflector30. Reflective surface40may be formed by depositing a layer or reflective material or film on top of it. The entire area of surface40or only its selected areas may be made reflective. A reflective layer formed on surface40may be provided with any of the properties described above for reflector30.

Linear light source10is positioned in a close proximity to light input edge12so that at least a 50% or more light emitted by the source can be input into light guide4through such light input edge. Linear light source10may be exemplified by a fluorescent tube or a strip of LEDs extending parallel to light input edge12. The LEDs may be incorporated in a linear, two-dimensional array which may include one, three or more rows and a number of columns. The LEDs may also be distributed over the surface of light input edge12according to a randomized two-dimensional pattern.

Light extraction elements6may be formed, for example, by dots of white paint or ink printed on either one or both surfaces20and40. Light extraction elements6may also be formed by interruptions or protrusions in otherwise smooth broad-area surfaces of light guide4. Light extraction elements6may be formed by light-deflecting surface relief features including but not limited to grooves, cavities, microprisms, microlenses, holes, protrusions, or roughened portions of the light guide surface. Such surface relief features may be formed in either one or both of surfaces20and40.

Light extraction elements6may also be formed by light deflecting particles distributed throughout the volume of the body of light guide4. By way of example, such light deflecting particles may include sub-micron size light-scattering particles embedded into the material of light guide4. In a further example, such light deflecting particles may be formed by macroscopic inclusions of a dielectric material having a different refractive index than the material of light guide4.

According to further embodiments, light extraction elements6may be formed by forward-scattering particles or relatively shallow surface relief structures configured to incrementally deflect light rays from the original propagation path by relatively small angles upon each interaction. Examples particularly include shallow surface corrugations and volumetrically distributed forward-scattering particles. Such light deflecting structures and elements are disclosed in U.S. Patent Applications Publication No. 2014/0140091, the disclosure of which is incorporated herein by reference in its entirety.

In the context of at least a preferred embodiment of the present invention, the term “forward scattering” is directed to mean the scattering of light involving a change of direction of less than 90 degrees. When applied to the propagation of a light ray through a forward-scattering medium, the light ray can be considered forward scattered when it is randomly deflected by the medium from the original propagation path towards a direction that makes an angle with the original propagation direction of less than 90 degrees. Similarly, the term “forward deflection” with respect to a light ray is directed to mean the deflection of such light ray at an angle of less than 90 degrees with respect to the original propagation path.

It is noted that, according to at least some embodiments, the forward-scattering operation of forward-scattering medium does not preclude backscattering (scattering in a generally backward direction) in which a portion of the incident light is scattered at angles of 90 degrees or more with respect to the incidence direction. Furthermore, according to at least some embodiments, it may be desired that backscattering accompanies the forward scattering. The proportions between the forward scattered and backscattered light energy may vary in a broad range. According to one embodiment, more than 50% of the incident light can be forward scattered and less than 50% of the incident light can be backscattered. According to one embodiment, more than 50% of the incident light can be backscattered and less than 50% of the incident light can be forward scattered. According to one embodiment, no less than 20% of the incident light energy is forward scattered and no less than 20% of the incident light energy is backscattered. According to one embodiment, no less than 30% of the incident light energy is forward scattered and no less than 30% of the incident light energy is backscattered. According to one embodiment, no less than 40% of the incident light energy is forward scattered and no less than 40% of the incident light energy is backscattered. According to one embodiment, the proportions between the forward scattered and backscattered portions of the light energy (after the subtraction of the absorbed light, if any) can be either one of 60%/40%, 70%/30%, 80%/20%, 20%/80%, 30%/70%, and 40%/60%. Furthermore, according to at least one embodiment, the forward-scattering angle can be much less than 90 degrees, for example, 60 degrees, 45 degrees, or 30 degrees. According to one embodiment, the forward-scattering angle is one of the following ranges: less than 60 degrees, less than 45 degrees and less than 30 degrees.

FIG.2schematically illustrates shaped illumination device900in a cross-section that is perpendicular to light input edge and parallel to a plane of a prevailing curvature of the device. Illumination device900ofFIG.2has the shape of an arc of a circle in such cross-section. It has a constant radius of curvature Rcbeing less than 1.2 times a width of the sheet that forms light guide4(as measured in the illustrated cross-section).

Linear light source10is exemplified by an LED2enclosed into an extruded structural channel50. It should be understood that light source10may include any suitable number of LEDs2distributed along the length of light input edge12(and channel50) according to any suitable pattern. Each LED2may be of an inorganic type and may include one or more LED chips or dies incorporated into an LED package. Such LED chips or dies may be arranged in one-dimensional or two-dimensional array within the LED package and may be encapsulated by a layer of optically transmissive encapsulation material. The encapsulation material may include phosphors for wavelength conversion of light emitted by the LED chips or dies.

The light input portion of light guide4that encompasses light input edge12and adjacent areas of surfaces20and40may further include light-coupling optics that enhances light injection into light input edge12. Yet further, a layer of a transparent, index-matched dielectric material (such as silicone or UV-curable acrylic, for example) may be provided between LED2and light input edge12to fill the air gap and enhance light coupling from the LED to the light guide. Various examples of LEDs and light coupling optical elements suitable for enhanced light input into sheet-form light guides are disclosed in a co-pending U.S. Patent Applications Publication No. 20170045666, the disclosure of which is incorporated herein by reference in its entirety, and U.S. Patent Applications Publication No. 20140226361, the disclosure of which is incorporated herein by reference in its entirety. When such light coupling optics is used, a light emitting aperture of LED2may have a size that is greater than a thickness of sheet-form light guide4at light input edge12. Otherwise, it is preferred that the light emitting aperture of LED2is approximately equal to or less than the light guide thickness at light input edge12.

Light input edge12may be specially shaped to facilitate light coupling into light guide4. Edge12may include cavities, protrusions, extensions and thicker or thinner areas or portions. Light input edge12may also include a tapered portion. Opposing edge14may also be configured for light input and shaped or configured according to the same principles described above for light input edge12.

Light may also be input into light guide4through either one or both broad-area surfaces20and40. Examples of such light input through broad-area surfaces (faces) of planar waveguides are disclosed in detail in U.S. Patent Applications Publications Nos. 20170045666 and 20140226361. In various implementations of shaped illumination device900, LEDs2may also be embedded into the body of light guide4.

Channel50is configured to provide structural support for light source10and may at least partially enclose the light source. Referring to the embodiment ofFIG.2, extruded channel50may be designed to hold LED2in a prescribed place and orientation with respect to light input edge12. It is preferred that channel50is made from a material that has high thermal conductivity and structural strength. Conventionally, channel50can be made from aluminum extrusion and configured to provide enhanced heat dissipation from LED2. Channel50may optionally include heat dissipating fins (not shown) extending parallel or perpendicular to a longitudinal axis of the channel and configured to remove heat from LED2. Each LED2may be attached/bonded to channel50with a good mechanical and thermal contact.

According to one embodiment, at least some light extraction elements6are configured to extract light from light guide4and cause light emission from at least concave broad-area light input/output surface20. Furthermore, it is preferred that at least a substantial portion of light exits from surface20at relatively high emergence and is directed generally towards edge14of light guide4. According to one embodiment, at least some light extraction elements6are configured to extract light from light guide4and cause light emission from at least convex broad-area light input/output surface40. According to one embodiment, at least one of light extraction elements6is configured to extract light from light guide4through both surfaces20and40.

A cone of light290schematically illustrates a directional light beam emitted from a particular area of surface20. Such light beam may have a sharply asymmetric angular distribution such that most of the extracted light rays form a relatively low angle with respect to their original propagation direction in light guide4and a relatively high angle with respect to a surface normal. For example, at a given light emitting location of surface20, an angle between a prevailing direction of light propagation and a normal to surface20may be greater than 30°, greater than 45°, greater than 60°, and greater than 70°. The prevailing propagation direction of the emergent light beam should also generally be pointing away from light input edge12. The emission angles and the size and curvature of light guide4are preferably selected such that at least one different area of concave surface20is positioned in energy receiving relationship with respect to the extracted/emitted light and is configured to intercept at least a portion of such extracted/emitted light. For example, as illustrated inFIG.2, an area of surface20adjacent to edge14may be positioned in energy receiving relationship with respect to a light emitting area of surface20that is located in a proximity to light input edge12.

It is noted that cone of light290is shown for illustrative purposes only. It is also shown to indicate a sharply asymmetric angular distribution of the beam emitted from concave surface20. However, it is further noted that the operation of shaped illumination device900does not preclude emitting light from surface20at angles outside of such cone of light290. It should be understood that portions of light energy may be emitted from surface20at any angle within the full ±90° angular range (with respect to a normal to surface20at the corresponding emission point). More particularly, a significant fraction of light can be emitted toward a normal direction with respect to surface20. According to one embodiment, a substantial fraction of light may also be emitted generally towards a source direction.

A luminance of surface20at any given location and at a particular emission angle may be measured using a luminance meter, such as, for example, LS-100/110 or LS-150/160 spot luminance meters commercially available from Konica Minolta, Inc. The angular asymmetry of the light beam emitted from a particular area of light-emitting surface20may be assessed by measuring surface luminance at different angles with respect to a surface normal. The angular luminance distribution of the entire light-emitting surface20may be measured using a goniophotometer such as those used for evaluating lighting fixtures.

Let's define an on-axis luminance Eon-axisof light-emitting surface20at a given point of the surface as a luminance measured within an angular range from 0° and 45° with respect to a surface normal at such point. Let's further define an off-axis luminance Eoff-axisof light-emitting surface20at the same point as a luminance measured within an angular range between 45° and 90° with respect to the surface normal. According to different embodiments, it is preferred that a maximum off-axis luminance Eoff-axisat a mid-point of surface20is greater than a maximum on-axis luminance Eon-axisat least by a factor of 1.2, 1.3, 1.4, and 1.5. It may further be preferred that off-axis luminance Eoff-axismeasured from a direction82(e.g., using a luminance meter86which light receiving aperture88is generally facing light input edge12) is substantially greater (e.g., by a factor of 1.5, 2, 3, or more) than off-axis luminance Eoff-axismeasured from a direction84(e.g., with light receiving aperture88of luminance meter86generally facing away from light input edge12).

It may be appreciated that the embodiments of shaped illumination device900employing reflector30of a diffuse type may exhibit a reduced asymmetry of the emitted light beam compared to the cases where reflector30is of a specular type or where the device is used without any reflector. This is primarily due to the fact that diffuse reflector30introduces random light propagation directions to the total light beam emitted by the device and may therefore partially or completely mask the asymmetric angular distribution produced by light guide4alone. Yet, it is noted that, according to at least some embodiments, Illumination device900may be configured to emit light with a measurable asymmetrical angular distribution of the emitted beam even in the presence of diffuse reflector30.

Different modes of operation of shaped illumination device900are further illustrated by example of light rays22,24, and26emanated by LED2and schematically depicted by solid, dashed and dotted lines, respectively.

Ray22(solid line) enters light guide4via light input edge12and propagates in the body of the light guide towards opposing edge14in response to optical transmission and TIR until it encounters one of the plurality of light extraction elements6. The respective light extraction element6deflects ray22away from a surface plane and out of light guide4. According to one embodiment, it is preferred that light extraction element6deflects ray22by means of a forward deflection or forward scattering. As a result, ray22exits from light guide4through concave light-output surface20. The emergence angle is such that ray22propagates generally away from light input edge12and towards opposing edge14, forming a relatively low propagation angle (significantly less than 90°) with respect to surface20.

Ray24(dashed line) is likewise emitted by LED2and coupled to light guide4through its light input edge12. Ray24initially propagates in a waveguide mode until it strikes one of the forward-deflecting or forward-scattering light extraction elements6relatively near light input edge12. Ray24is deflected away from its original propagation path and emitted from surface20at a location52. Upon the exit from light guide4, ray24forms a relatively high emergence angle θEwith respect to a surface normal44and further travels through air along surface20and towards opposing edge14of waveguide4. The area of illumination device900near edge14is curved appropriately and configured to intercept such light rays propagating at near-grazing angles with respect to surface20. As a result, ray24that travels a considerable distance outside of light guide4enters the light guide for the second time at a location54. Upon the re-entry, ray24propagates transversely through light guide4, undergoing double refraction at surfaces20and40, exits from surface40and strikes reflector30beneath light guide4. Reflector30reflects ray24with some forward scattering and causes at least a substantial portion of light energy of ray24to be emitted from surface20in the form of a divergent light beam, as schematically illustrated inFIG.2. Such divergent light beam further propagates away from surface20and contributes to the total light beam produced by illumination device900.

Accordingly, ray24initially emerging from light guide4relatively close to light input edge12(at location52) and at a relatively high emergence angle θEis trapped by illumination device900, recycled and re-emitted from a different area of the light guide (at location54). The final propagation direction of ray24may be different from its initial propagation direction. Such difference may constitute, for example 45°, 60°, or 90°. The final propagation directions and the emission cone may be controlled by the slope of reflector30and its reflective properties (e.g., a diffusion angle). It may be appreciated that such controlled recycling of light rays may be advantageously used to spatially and angularly redistribute the light beam and provide various prescribed emission patterns. For instance, shaped illumination device900may be configured to emit a relatively narrow (collimated) light beam with relatively uniform light intensity.

According to an aspect, illumination device distributes light emitted by LED2by means of light propagation though light guide4and also by means of propagation of a portion of light outside light guide4through the volume formed by the curved shape of flexible sheet that forms the light guide.

According to different embodiments, shaped illumination device900is configured for asymmetric light outcoupling from light guide4such that at least a substantial portion of light emerging from the light guide has exit angles (emergence angles) below 40°, below 30°, below 20°, or below 10°. Furthermore, reintroducing light initially emitted at a first location of light guide4(e.g., near light input edge12) at a different second location (e.g., near opposing edge14), as illustrated by ray24, may be advantageously used to increase the luminance of device900at the second location. For example, portions of shaped illumination device900near edge14may otherwise receive insufficient amount of light due to the depletion of light energy in light guide4as the light travels from light input edge12to the opposing edge14. This may particularly be the case in embodiments of shaped illumination device900in which light extraction elements6are identical and also spaced identically across the area of light guide4. In such embodiments, light extraction elements6may progressively extract fewer and fewer light from light guide4as the distance for light input edge12increases. Without light recycling, a light emitting area of shaped illumination device900near opposing edge14may appear considerably darker than a similar area near light input edge12or at a mid-section of the device. Thus, recapturing and re-emitting some of the high-emergence-angle by the areas of device900near edge14may at least partially compensate such light depletion and enhance the brightness uniformity across the light emitting surface of the device.

Ray26(dotted line) initially propagates within light guide4in a waveguide mode in response to optical transmission and bouncing from surfaces20and40by means of TIR until it strikes one of light extraction elements6. Unlike rays22and24, ray26is deflected towards convex surface40of light guide4, as a result of forward-deflecting or forward-scattering operation of the respective light extraction element6. Accordingly, ray26emerges from light guide4towards reflector30. Reflector30reflects ray26with some scattering and causes at least a substantial portion of the light energy of ray26to be emitted from surface20away from illumination device900in the form of a diffuse light beam. The diffusion angle may be controlled by the reflective properties of the surface of reflector30and/or the forward-scattering properties of light deflecting element6. According to one embodiment, shaped illumination device900is configured to emit light from the entire exposed surface20into prescribed directions such that the apparent brightness of the surface is relatively uniform when viewed from at least one of those directions.

Since surfaces20and40are curved, light propagating in light guide4may receive additional angular bias compared to the case of a planar light guide having the same dimensions and structure. It may be appreciated that at least some of the outermost out-of-plane light rays initially propagating in light guide by TIR may eventually escape from curved light guide4even without encountering light extraction elements6. It may further be appreciated that such escaping light rays may emerge at near-grazing angles with respect to the light emitting surface. Since both surfaces20and40are transparent and permeable to light propagating at below-TIR angles, light may escape at near-grazing angles from either one or both sides of light guide4. According to one embodiment, the curvature of light guide4may be selected so that the emergence angles of the escaping light rays are generally above 60° with respect to a surface normal (or below 30° with respect to the light-emitting surface) at the respective escape location. According to one embodiment, the curvature of light guide4may be selected so that light primarily emerges at angles generally above 70° with respect to a surface normal (or below 20° with respect to the light-emitting surface). Light rays emerging form light guide4at such angles may be recycled, angularly redistributed and re-emitted from shaped illumination device900at according to the mechanisms described above by example of rays22,24and26.

According to one embodiment, shaped illumination device900may be implemented without curved reflector30in which case light exiting from surface40will leave the device and can be used for two-sides emission (e.g., light can be emitted from both opposing surfaces20and40). According to one embodiment, reflector30may be provided on the side of concave broad-area surface20in which case nearly all of the light emitted by device900can be emanated from convex broad-area surface40. According to some embodiments, shaped illumination device900may be implemented without light extraction elements6and the light trapped in light guide4may be extracted by other means, for example, by appropriately curving and/or tapering the light guide along its length from light input edge12to opposing edge14.

It may be appreciated that edge-lit systems typically require a variable density or variable sizing of light extraction features to provide a relatively uniform light output from the light-emitting surface of a light guide. At one-sided light input, the density or sizes of light extracting features typically increase from a light input edge towards the opposing edge. In contrast, light recycling described above allows more light to be emitted from a portion of light guide4opposing to light input edge12than it would have otherwise been possible with a planar light guide of the same dimensions and internal structure. In view of this, according to one embodiment, shaped illumination device900may include light extraction elements6that are identical and have a generally uniform distribution density over the light emitting area of light guide4(e.g., constant spacing and sizes). By using the light recycling principles described above, such illumination device may be configured to provide a relatively uniform apparent brightness of its light-emitting surface at least at some viewing angles. According to an alternative embodiment, shaped illumination device900may include light extraction elements6distributed over the area of light guide4according to a varying pattern but such pattern may be different from the one which would be required for a planar configuration of light guide4to provide the same level of luminance uniformity. For example, the density of light extraction elements6may increase from light input edge12to opposing edge14. In a further example, the size or light extraction elements6may increase from light input edge12to opposing edge14while the density may be kept constant.

According to one embodiment, at least some of the light propagated in light guide4may also be emitted from edge14towards directions that are different from the original propagation direction of light emitted by LED2. An angle between the original propagation direction and the prevailing direction of light emergence from edge14may be approximately equal to an effective bend angle of light guide4.

FIG.3schematically shows, in a transversal cross-section that is perpendicular to surfaces20and40and light input edge12, an embodiment of shaped illumination device900which is identical to that ofFIG.2except that light extraction elements6are also formed in surface20. A reference line200is parallel to an optical axis of LED2and perpendicular to light input edge12. The optical axis of LED2may be defined as an axis that crosses the center of a light emitting aperture of LED2and is perpendicular to such light emitting aperture. Alternatively, the optical axis may also be defined as an axis that crosses the center of a light emitting aperture of LED2and is parallel to a direction of the maximum intensity of light emitted by LED2. In the illustrated case, reference line200is perpendicular to the planar surface of light input edge12and parallel to portions of surfaces20and40adjacent to light input edge12. Reference line200also indicates a tangent plane to surface20near light input edge12. Referring further toFIG.3, a reference line202indicates a tangent plane to surface20at opposing edge14.

Let's define a bend angle β of shaped illumination device900as an angle between the tangent planes at light input edge12and opposing edge14. According to one embodiment, bend angle β is equal to or greater than 20°. According to one embodiment, bend angle β is greater than 20° and less than 90°. According to one embodiment, bend angle β is greater than 30° and less than 90°. According to one embodiment, bend angle β is greater than 45° and less than 90°. According to one embodiment, bend angle β is about 90°. According to one embodiment, bend angle β is greater than 90° and less than 180°.

In view of the discussion presented in reference toFIG.2, it may be appreciated that a beam of light emitted by shaped illumination device900may be advantageously limited to generally exclude light propagation along directions that make relatively small angles with respect to reference line200. A critical cutoff angle α of light emission may be defined as an angle between reference line200and a reference line204that connects opposing edges12and14of light guide4. According to one embodiment, less than 10% of the total light energy emitted by shaped illumination device900propagates at angles below angular cutoff angle α. According to one embodiment, less than 5% of the total light energy emitted by shaped illumination device900propagates at angles below angular cutoff angle α. Shaped illumination device900may also be configured such that virtually no light is emitted below such angular cutoff. Accordingly, substantially all of the light emission may be directed to a relatively narrow, prescribed angular range. Such arrangements may basically preclude a direct view of the light input edge at viewing angles below cutoff angle α. They may also be advantageously employed for designing lighting luminaires that emit at least partially collimated light and provide masking of the light source (such as high-brightness LEDs) to prevent or minimize glare that may be caused by such light source. According to different embodiments, shaped illumination device900is configured to provide cutoff angle α of at least 10°, at least 20°, at least 30°, at least 40°, and at least 45°. According to different embodiments, the total emission angle of shaped illumination device900may be less than 140°, less than 120°, less than 90°, less than 60° and less than 45°. A FWHM emission angle of shaped illumination device900may be less than 100°, less than 90°, less than 45°, and less than 35°.

While LED2is shown being coupled to light input edge12by positioning a light emitting aperture of the LED in a close proximity to the light input edge, other forms of LED2coupling to light guide4may be used. For example, light can be coupled to light guide4partially or entirely through one or both of its surfaces20and40, or through a combination of light input edge12and surfaces20and/or40. Furthermore, according to one embodiment, a refractive index matching layer of an optically transmissive material may be provided between LED2and light input edge12of light guide4to eliminate the respective air gap and suppress Fresnel reflections within the material of LED2. Examples of such different forms of light coupling into light guide4may be found, for example, in U.S. Patent Application Publications Ser. No. 20170045666 and 20140226361, the disclosures of which are incorporated herein by reference by their entirety.

FIG.4schematically depicts an embodiment of shaped illumination device900in which curved light guide4has a tapered configuration. Such light guide4has a larger thickness at light input edge12and a substantially smaller thickness at opposing edge14. Broad-area surfaces20and40gradually converge towards each other at edge14so that the body of light guide4has the form of a thin, curved wedge.

In operation, a light ray112coupled to light guide4through its wider light input edge12is propagated towards opposing narrower edge14undergoing multiple TIRs from surfaces20and40. Since surfaces20and40are not exactly parallel to each other and are further curved, a propagation angle of ray112with respect to such surfaces progressively increases with each bounce until it becomes less than a critical angle of TIR characterizing the material of light guide4.

At this point, ray112exits from light guide4, undergoing refraction at surface20, and further propagates along surface20at near-grazing angle. Subsequently, ray112strikes a curved portion of light guide4at another location (e.g., near opposing edge14) where at least a substantial portion of its energy is reflected by means of a Fresnel reflection, contributing to the total collimated light beam emitted by device900.

It is noted that such secondary Fresnel reflection from surface20is illustrated by way of non-limiting example only and as one of the possible scenarios of light propagation. For example, depending on the emergence angle and the geometry of shaped illumination device900, ray112may also undergo refraction at the secondary interaction with surface20and can be recycled and re-emitted, similarly to ray24ofFIG.2. Furthermore, when an emergence angle of ray112is sufficiently low (with respect to a surface normal), it may completely avoid the secondary interaction with surface20and may thus continue its propagation along the original emission direction. Considering various possible scenarios of light propagation, it may be appreciated that the light guide4having a tapered configuration may be configured to emit a highly asymmetric light beam with relatively high emergence angles, as illustrated by cone of light290.

While the embodiment of shaped illumination device900may be configured to redistribute and emit light from its entire surface even without light extraction elements6, such light extraction elements may still be provided to enhance the light extraction rate and/or enhance the uniformity of light emission. In other words, the wedge-shaped configuration of light guide4, its curved shape and the plurality of light extraction elements6may act cooperatively to extract light from light guide4and contribute to the total emission flux of device900.

FIG.5schematically illustrates an embodiment of illumination device900in which light extraction elements6are exemplified by forward-scattering surface relief features that are formed in both surfaces20and40and represent discrete bulges of light scattering material protruding from the respective surfaces. According to one embodiment, each of these bulges may have a rounded hemispherical shape in a cross-section.

Several examples of different shapes of the bulges are illustrated inFIG.6throughFIG.10. The top surface of the bulge may be curved so that the bulge has a variable thickness gradually decreasing from its center to the periphery (FIG.6andFIG.7). According to one embodiment, each of the bulges may have a rounded “hat”-type shape in a cross-section (FIG.8). According to one embodiment, each of the bulges may have a relatively low thickness and flat or nearly flat top surface that extends about parallel to the respective surface (FIG.9). According to one embodiment, the top surface of each bulge may be irregular (FIG.10) or microstructured and the respective irregularities or microstructures may be configured to enhance scattering of the extracted light.

According to one embodiment, an average thickness of each bulge is between 2 micrometers and 15 micrometers. For example, an individual bulge may have a thickness of 6 micrometers, 8 micrometers, 10 micrometers or 15 micrometers at a highest point and a reduced thickness of only 2, 3, 4 or 5 micrometers at peripheral areas. The outermost peripheral areas of the bulges may have thicknesses that are below 1 micrometer (e.g., 0.1 or 0.5 micrometers).

According to one embodiment, the thickness of the light-extracting surface relief features and the load of forward-scattering particles are selected such that each light extraction element6is semi-opaque. According to one embodiment, each light extraction element6is configured to partially transmit light, with some forward scattering, and partially reflect light back toward the source, with some backscattering, when illuminated.

The forward-scattering and backscattering properties of the material forming semi-opaque, back-scattering light extraction element6may be evaluated, for example, by measuring a bidirectional scattering distribution function (BSDF) for a uniform layer of the same material deposited to a surface of a glass or acrylic plate. Such plate or film should preferably be made from the same or similar material as light guide4and may also have a similar thickness. The coating should preferably have a uniform thickness approximating the average thickness of the bulges forming forward-scattering light extraction elements6. For such measurements, the coated plate or film can be illuminated by a collimated light source from a perpendicular direction. As a practical consideration, the BSDF function may also be customarily obtained by separately measuring BRDF (bidirectional reflectance distribution function) and BTDF (bidirectional transmittance distribution function). A ratio between the forward-scattered and backscattered light can be estimated by dividing the total transmitted light energy by the total reflected light energy. In a variation of the technique, the measurements may be adapted to employ illuminating the sample from a direction that makes an angle of about 45 degrees with respect to a surface normal.

According to one embodiment, the material of semi-opaque, forward-scattering light extraction elements6may be selected such that an energy ratio between the forward-scattered (diffusely transmitted) light and the backscattered (diffusely reflected) light measured according to the above-described technique falls into one of the following ranges: 0.2 to 0.3, 0.3 to 0.4, 0.4 to 0.5, 0.5 to 0.6, 0.6 to 0.7, and 0.7 to 0.8. According to one embodiment, no less than 20% of the incident light energy is forward scattered and no less than 20% of the incident light energy is backscattered. According to one embodiment, no less than 30% of the incident light energy is forward scattered and no less than 30% of the incident light energy is backscattered. According to one embodiment, no less than 40% of the incident light energy is forward scattered and no less than 40% of the incident light energy is backscattered. The specific ratios between the forward-scattered and backscattered light exemplified above can be achieved, for example, by properly selecting the sizes and volumetric load of the light scattering particles in a clear binder or resin that is used to produce the forward-scattering material of light extraction elements6.

According to one embodiment, the volume of each bulge may be between 10000 cubic micrometers and 100000 cubic micrometers. According to one embodiment, the volume of each bulge may be between 10000 cubic micrometers and 500000 cubic micrometers. According to one embodiment, the sizes and volumes of the bulges may vary across surfaces20and/or40from 1000 cubic micrometers to 500000 cubic micrometers. For example, some individual bulges may have volumes of around 10000 cubic micrometers or less and some individual bulges may have volumes of around 30000 cubic micrometers, 40000 cubic micrometers, 60000 cubic micrometers, 100000 cubic micrometers or more.

According to one embodiment, the size (e.g., a diameter of the contact area of the bulge with surface20or40) of individual bulges can be within one of the following ranges: 20 to 200 micrometers, 10 to 20 micrometers, 20 to 60 micrometers, 60 to 100 micrometers, 100 to 200 micrometers, and 200 to 500 micrometers. The sizes may also vary from one bulge to another. For example, a first group of bulges may have sizes between 10 and 50 micrometers and a second group of bulges may have sizes between 100 and 150 micrometers. The bulges of different sizes, volumes, thicknesses and shapes may be mixed to cover an individual area of light guide4, according to a randomized pattern, where bulges of one size can be alternated with bulges of another size or sizes. The shapes may be regular (e.g., round, elliptical, square/rectangular, rectangular with rounded corners) or irregular (e.g., dumb-bell shaped, comma-shapes, having complex geometries or multiple curvatures of the respective outline).

Forward-scattering light extraction elements6that are formed in or on surface20may be distributed over the area of light guide4according to a first two-dimensional pattern and forward-scattering light extraction elements6that are formed in surface40may be distributed over the area of light guide4according to a second two-dimensional pattern which may be the same or different from the first pattern. Either one or both patterns may be ordered or random and may have constant or variable distribution densities over the respective surfaces. For example, the density may increase with the distance from LED2.

Each of forward-scattering surface relief features that form light extraction elements6is disposed with a good optical contact with the surfaces on which it is formed and includes forward-scattering particles9distributed throughout its volume. According to one embodiment, the forward-scattering particles include non-light-absorbing white pigment which may include, for example, nanoparticles of titanium dioxide having sizes from 200 to 400 nanometers and configured to deflect light by means of a diffraction and optionally by a refraction. According to an aspect, forward-scattering light extraction elements6formed in surface40and the light-scattering particles9that they contain represent an area-distributed forward-scattering layer disposed between surface40and reflector30and optically coupled to light guide4.

The respective surface relief features may be formed by depositing small drops of white ink or paint on surface40in a liquid form with the subsequent curing, e.g., by UV light. Such ink or paint may include a uniform suspension of forward-scattering particles9in a clear resin or binder. Individual drops of the white ink or paint may be deposited to surface40by means of piezo-actuated ink jet printing and cured by a UV LED lamp, for example. A hollow spacing layer31between surface40and reflector30should be sufficient to accommodate the height of surface-protruding light extraction elements6.

In operation, referring toFIG.5, a light ray121emanated by LED source12(not shown) and propagating in light guide4in response to TIR and optical transmission strikes one of forward-scattering light extraction elements6where it is split into two or more rays. A portion of ray121is deflected by forward-scattering particles9towards reflector30, as indicated by a light ray122. Ray122is subsequently reflected from reflector30and exits from light guide4through surface20.

A light ray123illustrates a portion of light ray121that is reflected by the material of light extraction element6directly toward surface20, similarly with some forward scattering. Both rays122and123are emitted at relatively high angles with respect to normal44. Accordingly, considering multiple light rays propagating in light guide4at different angles with respect to surfaces20and40, each relatively small portion of surface20may be configured to emit light in a forward direction (away from LED2) and within a narrow angular range, as illustrated by cone of light290.

A light ray126illustrates light that is extracted from light guide4by individual light extraction element6that is formed on surface20. Ray126enters the respective surface relief feature (e.g., a bulge formed by a cured drop of a light scattering while-pigmented ink) and is forward scattered away from the extraction location and out of light guide4. Similarly, multiple rays propagating in light guide4and striking the respective light extraction element6can be forward scattered, forming a cone of light291.

FIG.11schematically illustrates light extraction elements6exemplified by shallow (having low-angle reflective/refractive facets) prismatic surface relief features that provide forward-deflecting function with respect to light rays propagating in light guide4. More specifically, the prismatic surface relief features are represented by micro-prismatic grooves formed in surfaces20and40. The micro-prismatic grooves have a triangular cross-section and sloped surfaces configured to extract light from light guide4using refraction and/or TIR and to provide relatively high emergence angles of light rays, as illustrated by emission cone290.FIG.12illustrates a different mode of light extraction using such prismatic surface relief features and reflector30, also resulting in a low-angle off-axis emission.

FIG.13schematically illustrates an embodiment of shaped illumination device900having enhanced optical coupling between LED2and light guide4. It also schematically illustrates a yet further mode of light extraction from light guide4at high emergence angles. A layer32of index-matched optical material is provided between LED2and light input edge12such that the material completely fills the air gap between the light emitting surface of LED2and the light-receiving surface of light input edge12. The material of layer32should have a refractive index substantially greater than that of air (nair≈1). A preferable range of the refractive index is 1.4-1.8. According to one embodiment, layer32may have a refractive index approximating that of light guide4. According to one embodiment, layer32may have a refractive index approximating that of an encapsulation layer that may be employed in LED2.

In operation, light rays emitted by LED2at low off-axis angles are trapped within light guide4and propagate in a waveguide mode. Light rays emitted by LED2at relatively high off-axis angles may exit from surface20in a vicinity of light input edge12and form relatively high emergence angles. Accordingly, some of the emergent rays, at least those having the highest emergence angles (with respect to a surface normal), may be intercepted by other portions of shaped illumination device900and recycled and re-emitted from such other portions at different emergence angles, according to the principles discussed above.

It may be appreciated that the refractive index matching may be also be advantageously used to enhance the efficiency of light extraction from LED2by providing a gapless light transfer from the respective LED chips to light guide4for light rays that could otherwise be trapped and lost within the LED package. Thus, the illustrated configuration of shaped illumination device900may allow emitting more light from the respective LEDs compared to the bare LED packages that are not coupled to light guide4using the refractive index matching.

FIG.14depicts a schematic exemplary dependence of surface luminance of light guide4from the emission angle in a plane parallel to a prevailing direction of light propagation in light guide4. The emission angle is measured with respect to a surface normal. The negative emission angles correspond to angles measured from a surface normal towards light input edge12and the positive emission angles correspond to angles measured from a surface normal towards opposing edge14. Since each of surfaces20and40of light guide4may be configured to emit light, each of such surfaces may be characterized by its own angular dependence of surface luminance which may resemble that ofFIG.14.

When measuring a localized surface luminance representing a particular area of light guide4or shaped illumination device900, it is preferred that the shape and size of a sampling area approximates the shape and size of the area to be evaluated. For a spot measurement of the surface luminance, the sampling area should preferably be much smaller than the total area of the light emitting surface. Spot measurements may also be conventionally done employing a round or quasi-round sampling area. For example, for spot measuring of the surface luminance of surface20that has a characteristic dimension of 20 cm or more, the size of the sampling area may be from several millimeters to a couple of centimeters.

The angular dependence of surface luminance may be characterized by a peak luminance Lpand an angle αpcorresponding to such peak luminance. According to different embodiments, the angular distribution of a spot surface luminance of light guide4and/or the respective light-emitting surface of shaped illumination device900may be bounded by specific relationships between peak emission angle αpand bend angle β, e.g., in order to achieve optimal regimes of recycling light emitted from light guide4through secondary interactions of the emitted light with the light guide according to the principles discussed above. Such spot peak emission may be measured at an area of surface20relatively near light input edge12or at a mid-point of surface20, for example.

According to one embodiment, 90°−αp<1.5β. According to one embodiment, 90°−αp<2β. According to one embodiment, 90°−αp<β. According to one embodiment, 1.5(90°−αp)<β. According to one embodiment, 2(90°−αp)<β. In other words, the shape and curvature of light guide4may be selected such that at least a substantial part of light emitted in a vicinity of light input edge12or at a mid-point of the light emitting surface could be intercepted and recycled by an edge portion of shaped illumination device900.

One portion of shaped illumination device900(e.g., one half of the light emitting area of light guide4adjacent to edge14) may be configured to intercept and recycle a certain percentage of light energy emitted from another portion of the shaped illumination device900(e.g., the other half of the light emitting area of light guide4that is adjacent to edge12). According to different embodiments, such percentage may be 20%, 30%, 50%, 60% and 75%.

The location of the light beam recapture and recycling may be at a considerable distance from the location of the initial emission. For example, light may initially be emitted from a vicinity of light input edge12or a mid-point of surface20and then intercepted and recycled in a vicinity of opposing edge14. According to one embodiment, the distance between the location of initial emission and the location of light re-entry into light guide4is substantially greater than a thickness of light guide4. For example, such distance may be at least 2 times, 5 times, 10 times, 20 times, and 50 times greater than the light guide thickness. According to some embodiments, the distance between the location of initial emission and the location of light re-entry into light guide4is greater than 10%, 20%, 30%, 40%, or 50% of the size of the light emitting area of surface20or a width of light guide4.

FIG.15schematically illustrates an embodiment of shaped illumination device900that includes a second linear LED source101that is optically coupled to opposing edge14of light guide4. LED source101may have an identical structure to that of light source10and may include one or multiple LEDs102and opaque housing150encasing LED(s)102from three sides, as illustrated inFIG.15. Accordingly, the structure ofFIG.15has a symmetrical configuration in which light can travel in either direction and can be propagated, extracted and recycled symmetrically, in accordance with the principles described above for asymmetrical configurations of device900.

FIG.16schematically illustrates an embodiment of shaped illumination device900in which both light guide4and reflector30have a greater curvature compared to those ofFIG.2and which is characterized by bend angle β of about 90° (the tangent planes at opposing edges12and14being perpendicular to each other).FIG.17schematically illustrates an embodiment in which light guide4and reflector30have a variable curvature in a transversal cross-section that is perpendicular to light input edge12.FIG.18schematically illustrates an embodiment of shaped illumination device900in which light guide4and reflector30both have a substantially planar section adjacent to light input edge12.

FIG.19schematically illustrates an embodiment of shaped illumination device900which is formed by two symmetrical sections, such as those ofFIG.17, for example. Each section is formed by its own linear light source10, curved light guide4and similarly curved concave reflector30. The resulting configuration may have the shape of a symmetrical linear trough which emits light from its concave surface. Such light-emitting trough may be configured to emit light substantially from its entire concave area (except a relatively narrow spacing area between the symmetrical sections and may be characterized by a full emission angle Ω which is less than 180°. According to different embodiments, angle Ω can be approximately 160°, 140°, 120°, 105°, and 90°. According to one embodiment, angle Ω is between 90° and 160°. According to one embodiment, angle Ω is between 105° and 140°.

According to one embodiment, light guides4of symmetrical device900ofFIG.19may be detached from each other and separated by a spacing distance. Such distance may be selected to accommodate respective linear light sources10and any accompanying structural members. According to one embodiment, a single central structural support member58is provided. Each linear light source10is represented by an LED strip attached to the respective side of central structural support member58.

Two or more linear light sources10may also be replaced by a single linear light source configured to emit light into opposing directions (e.g., a fluorescent tube or linear LED strip with side-emitting optics). According to one embodiment, light guides4may joined together at their edges and form a single sheet-form light-guiding body. Portions of light input edges12of the respective light guides4may be curved or otherwise shaped to facilitate light coupling from one or more linear light sources10.

Shaped illumination device900may further include various additional light shaping layers or films. According to one embodiment, shaped illumination device900may include a light diffusing sheet of a transmissive type. Such light diffusing sheet may be curved to the same shape as light guide4and positioned adjacent to concave light output surface20. The light diffusing sheet may also be planar or curved to a different shape than light guide4. A transmissive light diffusing sheet may also be provided on the side of convex surface40.

In one embodiment, shaped illumination device900includes a brightness enhancement film disposed on top of surface20of light guide4. Such brightness enhancement film may be formed, for example, by a microprismatic film having isosceles right-angle linear microprisms distributed over its surface and facing away from light guide4. The brightness enhancement film may be configured to trap and recycle light emerging from curved light guide4and result in a more collimated light output from the device.

Either symmetrical or asymmetrical configurations of shaped illumination device900may be used for making various types of lighting fixtures. An exemplary embodiment of one such type of lighting fixture employing a symmetrical configuration of the device is schematically illustrated inFIG.20, which shows a suspended downlight1200having an inverted trough configuration.FIG.21,FIG.22andFIG.23schematically depict a section view, a top view and a bottom view of downlight1200, respectively.

Downlight1200includes two independently operating arms (sections) of shaped illumination device900each having its own light guide4, reflector30, and linear source10. Each of the linear light sources10is formed by a strip of LEDs2extending parallel to the respective light input edge12. Light sources10and respective edges12of light guides4are enclosed into a housing800that is preferably opaque and may be configured to block stray light emerging from the light input areas. Light sources10may also be mounted to one or more rigid structural bars or profiles. By way of example, an extruded profile similar to profile50shown inFIG.2. Profile50may also be modified to support and/or encase both of light sources10of downlight1200. It may further include ribs or fins to increase its surface area and promote heat dissipation from LEDs2.

Housing800may have any suitable color, such as, for example, black, white, gray, bronze, etc. A dark color, including black, may be used, for example to enhance the effect of stray light blocking. According to one embodiment, housing800is painted in white color or otherwise made highly reflective, e.g., by mirroring or white powder coating. Such housing800may be configured to assist in recycling light within the cavity formed by the trough-shaped downlight (e.g., by reflecting light exiting from edges12back to light guide4) and/or mask the appearance of the housing.

Downlight1200further has one or more pendant suspension elements302used to attach the lighting fixture to an overhead structure, such as a ceiling. Each suspension element302may be exemplified by a pipe, which may also be configured to carry wiring within its hollow body, or one or more cables, chains, etc.

Reflector30may be formed from a sheet metal material. It may be bent to the prescribed curved shape and mirrored or coated with a diffuse or semi-specular light reflecting material (e.g., white paint or powder coat). Light guide4may be formed from a highly transmissive plastic material, such as, for example, acrylic or polycarbonate. Light guide4may be formed from an optically transmissive sheet that may be originally planar. Such optically transmissive sheet may be formed to the prescribed curved shape using heat, for example. Alternatively, the optically transmissive sheet may be made sufficiently thin and flexible such that it can be elastically bent to conform to the shape of more rigid reflector30. In a yet further alternative, either one or both reflector30and light guide4may be formed in an elastic deformation regime by applying a flexing stress and fixing a prescribed shape by stiffening ribs or other suitable means. The prescribed curved shape may also be obtained by providing a sufficiently low thickness for light guide4and reflector30such that the light guide4and reflector4could bend under their own weight (gravity-assisted bending). Such exemplary configurations of downlight1200may be operated while light guide4and/or reflector30are in an elastically bent, strained state.

A method of making shaped edge-lit illumination device900may include providing elongated light source10(i.e., a fluorescent tube or a strip of LEDS2), providing light guide4in the form of a flexible sheet of an optically transmissive material (such as glass, PMMA, polycarbonate, or the like), providing reflector30in the form of a sheet of a reflective material, a step of forming light extracting features in the flexible sheet, a step of bending the flexible sheet to a predefined curved shape (e.g., at a bend angle sufficient to effectuate light recycling), a step of bending the sheet of a reflective material to the same curved shape, a step of positioning the curved reflective sheet adjacent to a convex surface of the curved light guide4, and a step of optical coupling the elongated light source10to a straight edge of curved light guide4. The method may optionally include a step of partially enclosing the elongated light source10into an opaque housing (e.g., such as housing800).

According to one embodiment, downlight1200may include light guide4only and no reflector30. In this case, downlight1200may be configured for direct and indirect lighting by emitting light both downwards and upwards. Such configuration may be advantageously selected, for example, when downlight1200is suspended below a high-reflectance ceiling. According to different embodiments, proportions between light energy emitted downwards and upwards or vice versa may be 50%/50%, 60%/40%, 70%/30%, 80%/20%, and 90%/10%.

It may be appreciated that the embodiments of downlight1200described above may allow for maximizing the light emitting area while maintaining a relatively low profile of the light fixture and eliminating additional components which may be unwanted in some applications. For instance, the interior of the trough-shaped body of downlight1200may be made substantially free from any bulky parts/components or major protrusions. In one embodiment, housing800protrudes into the trough cavity above surface20by no more than 30% of a depth of the trough, more preferably by no more than 20%, even more preferably by no more than 15%, and still even more preferably by no more than 10%. According to different embodiments, the interior of the trough-shaped body of downlight1200is substantially free from any objects that protrude by more than 10% of a depth of the respective trough and have a transversal size (in a plane perpendicular to a longitudinal axis of the trough) that is greater than 20%, 15%, 10%, and 5% of a width of the trough.

FIG.24schematically depicts an embodiment of a wall-mounted lighting fixture1210employing shaped illumination device900in an asymmetric configuration. Lighting fixture1210is mounted to a wall370and is configured to emit a soft, divergent light beam from the entire concave broad-area surface (surface20) while limiting the angular spread of the emitted light to only functional directions (e.g., downward only and/or generally away from wall24) and hiding the light source from the direct view. Lighting fixture1210may optionally include a wall reflector372configured to receive and reflect stray light emitted towards wall370.

Further details of a structure and different modes of operation of shaped edge-lit illumination devices shown in the drawing figures as well as their possible variations and uses will be apparent from the foregoing description of preferred embodiments. Although the description above contains many details, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Therefore, it will be appreciated that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.”

Any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of 1 to 10 is intended to include all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10, such as, for example, 3 to 6 or 2.5 to 8.5. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed therein and any minimum numerical limitation recited in this specification is intended to include all higher numerical limitations subsumed therein. Accordingly, Applicant reserves the right to amend this specification, including the claims, to expressly recite any sub-range subsumed within the ranges expressly recited herein. All such ranges are intended to be inherently described in this specification such that amending to expressly recite any such subranges would comply with the requirements of 35 U.S.C. § 1 12, first paragraph, and 35 U.S.C. § 132(a). Also, unless otherwise indicated, all numerical parameters are to be understood as being prefaced and modified in all instances by the term “about”, in which the numerical parameters possess the inherent variability characteristic of the underlying measurement techniques used to determine the numerical value of the parameter.

All structural, chemical, and functional equivalents to the elements of the above-described preferred embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”

Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. It is noted that, where a definition or use of a term in a reference, which is incorporated by reference herein is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls.