A troffer luminaire including (i) a light guide luminaire module having an optical extractor, and (ii) a reflector, where the reflector is configured to reflect light output by the optical extractor in a backward angular range toward a target surface in a forward angular range, and where a combination of the optical extractor and the first reflector is configured such that a ratio of maximum luminance to minimum luminance across the first reflector is less than a first predetermined ratio.

TECHNICAL FIELD

The present disclosure relates generally to luminaire modules for illuminating target surfaces, for example to troffer luminaires including solid state-based light guide illumination devices.

BACKGROUND

Light sources are used in a variety of applications, such as providing general illumination and providing light for electronic displays (e.g., LCDs). Historically, incandescent light sources have been widely used for general illumination purposes. Incandescent light sources produce light by heating a filament wire to a high temperature until it glows. The hot filament is protected from oxidation in the air with a glass enclosure that is filled with inert gas or evacuated. Incandescent light sources are gradually being replaced in many applications by other types of electric lights, such as fluorescent lamps, compact fluorescent lamps (CFL), cold cathode fluorescent lamps (CCFL), high-intensity discharge lamps, and solid state light sources, such as light-emitting diodes (LEDs).

SUMMARY

Troffer luminaires are disclosed that include a solid state-based light guide illumination device and one or two tertiary reflectors. Components of some of the disclosed troffer luminaires are configured such that the one or two tertiary reflectors appear to be uniformly lit when viewed by an observer, for example from directly underneath the illumination device. Moreover, components of some of the disclosed troffer luminaires are configured such that the illumination device blends together with the one or two tertiary reflectors as they appear to be uniformly lit when viewed by an observer, for example from directly underneath the illumination device. The foregoing uniformity of luminance across the one or two tertiary reflectors is quantified in terms of a ratio of maximum luminance to minimum luminance across the one or two tertiary reflectors.

In general, innovative aspects of the technologies described herein can be implemented in an illumination device that includes one or more of the following aspects:

In a first aspect, an illumination device includes a plurality of light-emitting elements (LEEs) arranged to emit light in a forward direction, the LEEs distributed along a transverse direction orthogonal to the forward direction; a light guide comprising a pair of opposing side surfaces arranged in parallel along the transverse direction and extending from a receiving end of the light guide to an opposing end of the light guide, the light guide configured to guide light received at the receiving end from the LEEs in the forward direction to the opposing end; an optical extractor elongated along the transverse direction and located at the opposing end of the light guide to redirect at least some of the guided light and to output at least some of the redirected light in an ambient environment as first output light in a first backward angular range along a first one of the pair of opposing side surfaces of the light guide; and a first reflector adjacent the first one of the pair of opposing side surfaces of the light guide and spaced apart from the optical extractor to reflect the light in the first backward angular range in a first forward angular range toward a target surface. Further, a first combination of the optical extractor and the first reflector is configured such that a ratio of maximum luminance to minimum luminance across the first reflector is less than a first predetermined ratio.

The foregoing and other embodiments can each optionally include one or more of the following features, alone or in combination. In some implementations, the first predetermined ratio can be less than 5:1. In some cases, the first predetermined ratio is less than 3:1.

In some implementations, the optical extractor can include a solid optic including: an input surface to receive the guided light, a first forward output surface that is flat, the first forward output surface to transmit at least a portion of the guided light to the ambient environment in a third forward angular range, a first backward output surface that is convex and extends between the input surface and the first forward output surface, and a first redirecting surface that extends between the input surface and the first forward output surface, the first redirecting surface to reflect another portion of the guided light toward first backward output surface, the first backward output surface to transmit the reflected light to the ambient environment in the first backward angular range. In some cases, the first backward output surface can be a diffuse-transmissive surface. In some cases, the first redirecting surface can be convex over a portion adjacent to the input surface and can be flat over a portion adjacent the first forward output surface. Here, the first redirecting surface and the first forward output surface can intersect at a vertex.

In some implementations, the first reflector can include a diffuse-reflective surface. In some implementations, the illumination device can include one or more optical couplers. Here, the light provided by the LEEs is in a first angular range, the optical couplers are arranged to receive the light provided by the LEEs and redirect it to the receiving end of the light guide in a second angular range, and a numerical aperture of the light guide is such that the light received from the optical couplers in the second angular range can be guided by the light guide through TIR off the pair of opposing side surfaces. In some implementations, the LEEs are LEDs that emit white light. In some implementations, a distance from an edge of the first reflector adjacent the light guide to an edge of the optical extractor remote from the light guide can be less than 3″. In some implementations, the first reflector can be concave and has a sag that is less than 3″.

In some implementations, the optical extractor can be configured to output some other of the redirected light in the ambient environment as second output light in a second backward angular range along a second one of the pair of opposing side surfaces of the light guide. Here, the illumination device can further include a second reflector adjacent the second one of the pair of opposing side surfaces of the light guide and spaced apart from the optical extractor to reflect the light in the second backward angular range in a second forward angular range toward the target surface. Here, a second combination of the optical extractor and the second reflector is configured such that a ratio of maximum luminance to minimum luminance across the second reflector is less than a second predetermined ratio. In some cases, the second predetermined ratio is equal to the first predetermined ratio. In some cases, a third combination of the optical extractor, the first reflector and the second reflector can be configured such that a ratio of maximum luminance to minimum luminance across the optical extractor, the first reflector and the second reflector is less than a third predetermined ratio. For example, the third predetermined ratio can be less than 20:1.

In some implementations, the optical extractor includes a solid optic including: an input surface to receive the guided light, a first forward output surface that is flat and a second forward output surface that is flat, the first and second forward output surfaces arranged to be mirror symmetric relative to the light guide and configured to transmit a portion of the guided light to the ambient environment in a third forward angular range, a first backward output surface that is convex and extends between the input surface and the first forward output surface, and a second backward output surface that is convex and extends between the input surface and the second forward output surface, the first and second backward output surfaces arranged to be mirror symmetric relative to the light guide, a third forward output surface configured to transmit another portion of the guided light to the ambient environment in the third forward angular range, and a first redirecting surface that extends between the first forward output surface and the third forward output surface, and a second redirecting surface that extends between the second forward output surface and the third forward output surface, the first and second redirecting surfaces arranged to be mirror symmetric relative to the light guide, the first redirecting surface to reflect yet another portion of the guided light toward the first backward output surface, the first backward output surface to transmit the light reflected by the first redirecting surface to the ambient environment in the first backward angular range, and the second redirecting surface to reflect the remaining guided light toward the second backward output surface, the second backward output surface to transmit the light reflected by the second redirecting surface to the ambient environment in the second backward angular range. In some cases, the third forward output surface can be concave. In some cases the first and second reflectors are arranged to be mirror symmetric relative to the light guide. In some cases, the first and second reflectors can include diffuse-reflective surfaces.

In some implementations, a troffer luminaire can include the foregoing illumination device and a housing configured to support the illumination device. In some cases, a dimension of the housing along the forward direction can be less than 3″.

The illumination devices described in this specification may be configured to use light flux originating from one or more primary solid state light sources of known dimensional, geometric, brightness and uniformity characteristics, and a secondary reflector/refractor/combination optic to output a specified radiation pattern. The secondary optic can redistribute the source flux's “phase-space” to a new phase-space of prescribed dimensional extent and angular divergence (e.g., directional cosines) while maintaining a substantially uniform intensity from the secondary optic. The disclosed illumination devices can provide uniform illumination of a target surface, efficient energy conversion from the primary solid state light sources of the illumination devices to the target surface, and uniform and/or glare-free intensity from the fixture itself when viewed from the target surface. Additionally, the disclosed illumination devices can provide glare-free intensity characteristics while maintaining efficiency and directionality in flux redirection.

The details of one or more implementations of the technologies described herein are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the disclosed technologies will become apparent from the description, the drawings, and the claims.

Reference numbers and designations in the various drawings indicate exemplary aspects, implementations of particular features of the present disclosure.

DETAILED DESCRIPTION

FIG. 1shows an example of a troffer luminaire100for providing illumination to a target surface. The troffer luminaire100includes (i) a light guide luminaire module101, also referred to as an illumination device, having solid state light sources, and (ii) at least a first tertiary reflector170′. In some implementations, the troffer luminaire100includes a second tertiary reflector170″, in addition to the first tertiary reflector170′. Note that the tertiary reflectors170′,170″ also are referred to, simply, as reflectors170′,170″. In this example, the troffer luminaire100further includes a housing102that supports the light guide luminaire module101and the one or two tertiary reflectors170′,170″. As such, the troffer luminaire100can efficiently guide, distribute and redirect light emitted by solid-state light sources of the light guide luminaire module101towards target surfaces, e.g., towards a floor, one or more workbenches, etc. For example, light emitted by the solid-state light sources is coupled into an end of a light guide of the light guide luminaire module101and guided in a forward direction (e.g., along the z-axis) to an opposing end thereof where an optical extractor140of the light guide luminaire module redirects at least a portion of the guided light in a first backward angular range145′ towards the first tertiary reflector170′. And, when the second tertiary reflector also is included in the troffer luminaire100, another portion of the guided light in a second backward angular range145″ towards the second tertiary reflector170″. The first tertiary reflector170′ reflects the light redirected in the first backward angular range145′ in a first forward angular range155′ toward the target surface. And, when the second tertiary reflector also is included in the troffer luminaire100, the light redirected in the second backward angular range145″ in a second forward angular range155″ toward the target surface.

As used herein, providing light in an “angular range” refers to providing light that propagates in one or more prevalent directions in which each has a divergence with respect to the corresponding prevalent direction. In this context, the term “prevalent direction of propagation” refers to a direction along which a portion of an intensity distribution of the propagating light has a maximum. For example, the prevalent direction of propagation associated with the angular range can be an orientation of a lobe of the (angular) intensity distribution. (See, e.g.,FIG. 2C.) Also in this context, the term “divergence” refers to a solid angle outside of which the intensity distribution of the propagating light drops below a predefined fraction of a maximum of the intensity distribution. For example, the divergence associated with the angular range can be the width of the lobe of the intensity distribution. The predefined fraction can be 50%, 10%, 5%, 1%, or other values, depending on the lighting application.

In some implementations, an output surface of the optical extractor140is a Fresnel-transmissive surface (i.e., most of light that transmits through such a surface undergoes refraction, and no more than 4% of it undergoes back reflection) and a corresponding reflective surface of each of the tertiary reflectors170′,170″ is a diffuse-reflective surface (i.e., light reflected off such a surface undergoes diffusive scattering). In other implementations, the output surface of the optical extractor140is a diffuse-transmissive surface (i.e., most of light that transmits through such a surface undergoes diffusive scattering) and a corresponding reflective surface of each of the tertiary reflectors170′,170″ is a specular-reflective surface (i.e., light reflected off such a surface undergoes specular reflection). In some other implementations, each of the output surface of the optical extractor140and a corresponding reflective surface of each of the tertiary reflectors170′,170″ includes a diffuse-reflective surface. As such, an intensity profile of the light provided by the troffer luminaire100in the first forward angular range155′ is a Lambertian profile (represented inFIG. 1by a first “uniform” lobe). And, when the second tertiary reflector also is included in the troffer luminaire100, an intensity profile of the light provided by the troffer luminaire in the second forward angular range155″ also is a Lambertian profile (represented inFIG. 1by a second “uniform” lobe). The light issued by the troffer luminaire100in the first and second forward angular ranges155′,155″ is said to provide indirect illumination to the target surface.

Additionally, a remaining portion of the guided light is output by the optical extractor140of the light guide luminaire module101in a third forward angular range145′″. In the example implementation illustrated inFIG. 1, an exit surface of the optical extractor140is a Fresnel-transmissive surface, such that an intensity profile of the light issued by the troffer luminaire100in the third forward angular range145′″ is a “batwing” profile (represented inFIG. 1by a batwing-shaped lobe). In other implementations, the exit surface of the optical extractor140is a diffusive-transmissive surface, such that the intensity profile of the light issued by the troffer luminaire100in the third forward angular range145′″ is a Lambertian profile similar to the Lambertian profiles of the light in the first and second forward angular ranges155′,155″. The light issued by the troffer luminaire100in the third forward angular ranges145′″ is said to provide direct illumination to the target surface.

Microstructure characteristics that determine reflectivity and/or diffusivity of (i) the output surface(s) and the exit surface of the optical extractor140, and (ii) the corresponding reflective surfaces of the tertiary reflectors170′,170″ can be configured such that the direct illumination represents a predetermined fraction of the illumination provided by the troffer luminaire100to the target surface, and the indirect illumination represents the inverse of the predetermined fraction. For example, the foregoing reflectivity and/or diffusivity characteristics can be implemented such that the illumination provided by the troffer luminaire100is between 40-90% indirect illumination and between 60-10% direct illumination.

In addition, (i) the output surface(s) of the optical extractor140, and (ii) the corresponding reflective surfaces of the tertiary reflectors170′,170″ can be shaped and arranged such that each of the tertiary reflectors170′,170″ appears to be uniformly lit when viewed by an observer of the troffer luminaire100from directly underneath the optical extractor. The foregoing uniformity of luminance across each of the tertiary reflectors170′,170″ is quantified in terms of a ratio of maximum luminance to minimum luminance across each of the tertiary reflectors. For example, a ratio of maximum luminance to minimum luminance across each of the tertiary reflectors170′,170″ can be lower than 5:1, 4:1 or 3:1. In this manner, the observer can view a fully lit surface of each of the tertiary reflectors170′,170″ free of dark regions and/or hot spots.

In some cases, both the microstructure and the shape/arrangement (i) the output surface(s) of the optical extractor140, and (ii) the corresponding reflective surfaces of the tertiary reflectors170′,170″ can be configured such that a bottom portion of the optical extractor140blends together with the one or two tertiary reflectors as they (i.e., the bottom portion of the optical extractor and the one or two tertiary reflectors) appear to be uniformly lit when viewed by an observer of the troffer luminaire100from directly underneath the optical extractor. The foregoing uniformity of luminance across the bottom portion of the optical extractor140and the one or two tertiary reflectors170′,170″ is quantified in terms of a ratio of maximum luminance to minimum luminance across the bottom portion of the optical extractor and the one or two tertiary reflectors. For example, a ratio of maximum luminance to minimum luminance across the bottom portion of the optical extractor140and the one or two tertiary reflectors170′,170″ can be lower than 25:1, 20:1 or 15:1.

The troffer luminaire100can be suspended adjacent to, or can be disposed in a recession of, a ceiling above a target surface. Efficiency of the troffer luminaire100, defined as the fraction of the light emitted by the solid-state light sources of the light guide luminaire module101that is provided to the target surface, can reach 90%.

Prior to describing details of various embodiments of the optical extractor140of the light guide luminaire module101and of the two tertiary reflectors170′,170″ of the troffer luminaire100, components of a similar light guide luminaire module are generally described, and another troffer luminaire is described for which the indirect illumination is non-Lambertian.

Light Guide Luminaire Module

Referring toFIG. 2A, a light guide luminaire module201, simply referred to as a luminaire module201, includes a substrate205having a plurality of LEEs210distributed along a first surface of the substrate205. The mount with the LEEs210is disposed at a first (e.g., upper) edge231of a light guide230. Once again, the positive z-direction is referred to as the “forward” direction and the negative z-direction is the “backward” direction. Sections through the luminaire module201parallel to the x-z plane are referred to as the “cross-section” or “cross-sectional plane” of the luminaire module. Also, luminaire module201extends along the y-direction, so this direction is referred to as the “longitudinal” direction of the luminaire module. Implementations of luminaire modules can have a plane of symmetry parallel to the y-z plane, be curved or otherwise shaped. This is referred to as the “symmetry plane” of the luminaire module.

Multiple LEEs210are disposed on the first surface of the substrate205, although only one of the multiple LEEs210is shown inFIG. 2A. For example, the plurality of LEEs210can include multiple white LEDs. The LEEs210are optically coupled with one or more optical couplers220(only one of which is shown inFIG. 2A). An optical extractor240is disposed at second (e.g., lower) edge232of light guide230.

Substrate205, light guide230, and optical extractor240extend a length L along the y-direction, so that the luminaire module is an elongated luminaire module with an elongation of L that may be about parallel to a wall of a room (e.g., a ceiling of the room). Generally, L can vary as desired. Typically, L is in a range from about 1 cm to about 200 cm (e.g., 20 cm or more, 30 cm or more, 40 cm or more, 50 cm or more, 60 cm or more, 70 cm or more, 80 cm or more, 100 cm or more, 125 cm or more, or, 150 cm or more).

The number of LEEs210on the substrate205will generally depend, inter alia, on the length L, where more LEEs are used for longer luminaire modules. In some implementations, the plurality of LEEs210can include between 10 and 1,000 LEEs (e.g., about 50 LEEs, about 100 LEEs, about 200 LEEs, about 500 LEEs). Generally, the density of LEEs (e.g., number of LEEs per unit length) will also depend on the nominal power of the LEEs and illuminance desired from the luminaire module. For example, a relatively high density of LEEs can be used in applications where high illuminance is desired or where low power LEEs are used. In some implementations, the luminaire module201has LEE density along its length of 0.1 LEE per centimeter or more (e.g., 0.2 per centimeter or more, 0.5 per centimeter or more, 1 per centimeter or more, 2 per centimeter or more). The density of LEEs may also be based on a desired amount of mixing of light emitted by the multiple LEEs. In implementations, LEEs can be evenly spaced along the length, L, of the luminaire module. In some implementations, the substrate205can be attached to a housing202configured as a heat-sink to extract heat emitted by the plurality of LEEs210. A surface of the substrate205that contacts the housing202opposes the side of the substrate205on which the LEEs210are disposed. The luminaire module201can include one or multiple types of LEEs, for example one or more subsets of LEEs in which each subset can have different color or color temperature.

Optical coupler220includes one or more solid pieces of transparent optical material (e.g., a glass material or a transparent plastic, such as polycarbonate or acrylic) having surfaces221and222positioned to reflect light from the LEEs210towards the light guide230. In general, surfaces221and222are shaped to collect and at least partially collimate light emitted from the LEEs. In the x-z cross-sectional plane, surfaces221and222can be straight or curved. Examples of curved surfaces include surfaces having a constant radius of curvature, parabolic or hyperbolic shapes. In some implementations, surfaces221and222are coated with a highly reflective material (e.g., a reflective metal, such as aluminum or silver), to provide a highly reflective optical interface. The cross-sectional profile of optical coupler220can be uniform along the length L of luminaire module201. Alternatively, the cross-sectional profile can vary. For example, surfaces221and/or222can be curved out of the x-z plane.

The exit aperture of the optical coupler220adjacent upper edge of light guide231is optically coupled to edge231to facilitate efficient coupling of light from the optical coupler220into light guide230. For example, the surfaces of a solid coupler and a solid light guide can be attached using a material that substantially matches the refractive index of the material forming the optical coupler220or light guide230or both (e.g., refractive indices across the interface are different by 2% or less.) The optical coupler220can be affixed to light guide230using an index matching fluid, grease, or adhesive. In some implementations, optical coupler220is fused to light guide230or they are integrally formed from a single piece of material (e.g., coupler and light guide may be monolithic and may be made of a solid transparent optical material).

Light guide230is formed from a piece of transparent material (e.g., glass material such as BK7, fused silica or quartz glass, or a transparent plastic, such as polycarbonate or acrylic) that can be the same or different from the material forming optical couplers220. Light guide230extends length L in the y-direction, has a uniform thickness T in the x-direction, and a uniform depth D in the z-direction. The dimensions D and T are generally selected based on the desired optical properties of the light guide (e.g., which spatial modes are supported) and/or the direct/indirect intensity distribution. During operation, light coupled into the light guide230from optical coupler220(with an angular range125) reflects off the planar surfaces of the light guide by TIR and spatially mixes within the light guide. The mixing can help achieve illuminance and/or color uniformity, along the x-axis, at the distal portion of the light guide232at optical extractor240. The depth, D, of light guide230can be selected to achieve adequate uniformity at the exit aperture (i.e., at end232) of the light guide. In some implementations, D is in a range from about 1 cm to about 20 cm (e.g., 2 cm or more, 4 cm or more, 6 cm or more, 8 cm or more, 10 cm or more, 12 cm or more).

In general, optical couplers220are designed to restrict the angular range of light entering the light guide230(e.g., to within +/−40 degrees) so that at least a substantial amount of the light (e.g., 95% or more of the light) is optically coupled into spatial modes in the light guide230that undergoes TIR at the planar surfaces. Light guide230can have a uniform thickness T, which is the distance separating two planar opposing surfaces of the light guide. Generally, T is sufficiently large so the light guide has an aperture at first (e.g., upper) surface231sufficiently large to approximately match (or exceed) the exit aperture of optical coupler220. In some implementations, T is in a range from about 0.05 cm to about 2 cm (e.g., about 0.1 cm or more, about 0.2 cm or more, about 0.5 cm or more, about 0.8 cm or more, about 1 cm or more, about 1.5 cm or more). Depending on the implementation, the narrower the light guide the better it may spatially mix light. A narrow light guide also provides a narrow exit aperture. As such light emitted from the light guide can be considered to resemble the light emitted from a one-dimensional linear light source, also referred to as an elongate virtual filament.

While optical coupler220and light guide230are formed from solid pieces of transparent optical material, hollow structures are also possible. For example, the optical coupler220or the light guide230or both may be hollow with reflective inner surfaces rather than being solid. As such material cost can be reduced and absorption in the light guide can be mitigated. A number of specular reflective materials may be suitable for this purpose including materials such as 3M Vikuiti™ or Miro IV™ sheet from Alanod Corporation where greater than 90% of the incident light can be efficiently guided to the optical extractor.

Optical extractor240is also composed of a solid piece of transparent optical material (e.g., a glass material or a transparent plastic, such as polycarbonate or acrylic) that can be the same as or different from the material forming light guide230. In the example implementation shown inFIG. 2A, the optical extractor240includes redirecting (e.g., flat) surfaces242and244and curved surfaces246and248. The flat surfaces242and244represent first and second portions of a redirecting surface243, while the curved surfaces246and248represent first and second output surfaces of the luminaire module201.

Surfaces242and244are coated with a reflective material (e.g., a highly reflective metal such as aluminum or silver) over which a protective coating may be disposed. For example, the material forming such a coating may reflect about 95% or more of light incident thereon at appropriate (e.g., visible) wavelengths. Here, surfaces242and244provide a highly reflective optical interface for light having the angular range125entering an input end of the optical extractor232′ from light guide230. As another example, the surfaces242and244include portions that are transparent to the light entering at the input end232′ of the optical extractor240. Here, these portions can be uncoated regions (e.g., partially silvered regions) or discontinuities (e.g., slots, slits, apertures) of the surfaces242and244. As such, some light is transmitted in the forward direction (along the z-axis) through surfaces242and244of the optical extractor240in a third forward angular range145′″. In some cases, the light transmitted in the third forward angular range145′″ is refracted. In this way, the redirecting surface243acts as a beam splitter rather than a mirror, and transmits in the third forward angular range145′″ a desired portion of incident light, while reflecting the remaining light in angular ranges138and138′.

In the x-z cross-sectional plane, the lines corresponding to surfaces242and244have the same length and form an apex or vertex241, e.g. a v-shape that meets at the apex241. In general, an included angle (e.g., the smallest included angle between the surfaces244and242) of the redirecting surfaces242,244can vary as desired. For example, in some implementations, the included angle can be relatively small (e.g., from 30° to 60°). In certain implementations, the included angle is in a range from 60° to 120° (e.g., about 90°). The included angle can also be relatively large (e.g., in a range from 120° to 150° or more). In the example implementation shown inFIG. 2A, the output surfaces246,248of the optical extractor240are curved with a constant radius of curvature that is the same for both. In an aspect, the output surfaces246,248may have optical power (e.g., may focus or defocus light.) Accordingly, luminaire module201has a plane of symmetry intersecting apex241parallel to the y-z plane.

The surface of optical extractor240adjacent to the lower edge232of light guide230is optically coupled to edge232. For example, optical extractor240can be affixed to light guide230using an index matching fluid, grease, or adhesive. In some implementations, optical extractor240is fused to light guide230or they are integrally formed from a single piece of material.

The emission spectrum of the luminaire module201corresponds to the emission spectrum of the LEEs210. However, in some implementations, a wavelength-conversion material may be positioned in the luminaire module, for example remote from the LEEs, so that the wavelength spectrum of the luminaire module is dependent both on the emission spectrum of the LEEs and the composition of the wavelength-conversion material. In general, a wavelength-conversion material can be placed in a variety of different locations in luminaire module201. For example, a wavelength-conversion material may be disposed proximate the LEEs210, adjacent surfaces242and244of optical extractor240, on the exit surfaces246and248of optical extractor240, and/or at other locations.

The layer of wavelength-conversion material (e.g., phosphor) may be attached to light guide230held in place via a suitable support structure (not illustrated), disposed within the extractor (also not illustrated) or otherwise arranged, for example. Wavelength-conversion material that is disposed within the extractor may be configured as a shell or other object and disposed within a notional area that is circumscribed between R/n and R*(1+n2)(−1/2), where R is the radius of curvature of the light-exit surfaces (246and248inFIG. 2A) of the extractor240and n is the index of refraction of the portion of the extractor that is opposite of the wavelength-conversion material as viewed from the reflective surfaces (242and244inFIG. 2A). The support structure may be a transparent self-supporting structure. The wavelength-conversion material diffuses light as it converts the wavelengths, provides mixing of the light and can help uniformly illuminate a surface of the ambient environment.

During operation, light exiting light guide230through end232impinges on the reflective interfaces at portions of the redirecting surface242and244and is reflected outwardly towards output surfaces246and248, respectively, away from the symmetry plane of the luminaire module. The first portion of the redirecting surface242provides light having an angular distribution138towards the output surface246, the second portion of the redirecting surface244provides light having an angular distribution138′ towards the output surface246. The light exits optical extractor through output surfaces246and248. In general, the output surfaces246and248have optical power, to redirect the light exiting the optical extractor240in first and second backward angular ranges145′,145″, respectively. For example, optical extractor240may be configured to emit light upwards (i.e., towards the plane intersecting the LEEs and parallel to the x-y plane), downwards (i.e., away from that plane) or both upwards and downwards. In general, the direction of light exiting the luminaire module through surfaces246and248depends on the divergence of the light exiting light guide230and the orientation of surfaces242and244.

Surfaces242and244may be oriented so that little or no light from light guide230is output by optical extractor240in certain directions. In implementations where the luminaire module201is attached to a ceiling of a room (e.g., the forward direction is towards the floor) such configurations can help avoid glare and an appearance of non-uniform illuminance.

In general, the light intensity distribution provided by luminaire module201reflects the symmetry of the luminaire module's structure about the y-z plane. For example, referring toFIG. 2C, light output in first backward angular range145′ corresponds to the first output lobe145aof the far-field light intensity distribution290, light output in second backward angular range145″ corresponds to the second output lobe145bof the far-field light intensity distribution290and light output (leaked) in third forward angular range145′″ corresponds to the third output lobe145cof the far-field light intensity distribution290. In general, an intensity profile of luminaire module201will depend on the configuration of the optical coupler220, the light guide230and the optical extractor240. For instance, the interplay between the shape of the optical coupler220, the shape of the redirecting surface243of the optical extractor240and the shapes of the output surfaces246,248of the optical extractor240can be used to control the angular width and prevalent direction (orientation) of the output first145aand second145blobes in the far-field light intensity profile101. Additionally, a ratio of an amount of light in the combination of first145aand second145boutput lobes and light in the third output lobe145cis controlled by reflectivity and transmissivity of the redirecting surfaces242and244. For example, for a reflectivity of 90% and transmissivity of 10% of the redirecting surfaces242,244, 45% of light can be output in the first backward angular range145′ corresponding to the first output lobe145a,45% light can be output in the second backward angular range145″ corresponding to the second output lobe145b, and 10% of light can be output in the third forward angular range145′″ corresponding to the third output lobe145c.

In some implementations, the orientation of the output lobes145a,145bcan be adjusted based on the included angle of the v-shaped groove241formed by the portions of the redirecting surface242and244. For example, a first included angle results in a far-field light intensity distribution101with output lobes145a,145blocated at relatively smaller angles compared to output lobes145a,145bof the far-field light intensity distribution101that results for a second included angle larger than the first angle. In this manner, light can be extracted from the luminaire module201in a more forward direction for the smaller of two included angles formed by the portions242,244of the redirecting surface243.

Furthermore, while surfaces242and244are depicted as planar surfaces, other shapes are also possible. For example, these surfaces can be curved or faceted. Curved redirecting surfaces242and244can be used to narrow or widen the output lobes145a,145b. Depending of the divergence of the angular range125of the light that is received at the input end of the optical extractor232′, concave reflective surfaces242,244can narrow the lobes145a,145boutput by the optical extractor240(and illustrated inFIG. 2C), while convex reflective surfaces242,244can widen the lobes145a,145boutput by the optical extractor240. As such, suitably configured redirecting surfaces242,244may introduce convergence or divergence into the light. Such surfaces can have a constant radius of curvature, can be parabolic, hyperbolic, or have some other curvature.

In general, the geometry of the elements can be established using a variety of methods. For example, the geometry can be established empirically. Alternatively, or additionally, the geometry can be established using optical simulation software, such as Lighttools™, Tracepro™, FRED™ or Zemax™, for example.

In general, luminaire module201can be designed to output light into different first and second backward angular ranges145′,145″ from those shown inFIG. 2A. In some implementations, illumination devices can output light into lobes145a,145bthat have a different divergence or propagation direction than those shown inFIG. 2C. For example, in general, the output lobes145a,145bcan have a width of up to about 90° (e.g., 80° or less, 70° or less, 60° or less, 50° or less, 40° or less, 30° or less, 20° or less). In general, the direction in which the output lobes145a,145bare oriented can also differ from the directions shown inFIG. 2C. The “direction” refers to the direction at which a lobe is brightest. InFIG. 2C, for example, the output lobes145a,145bare oriented at approx. −130° and approximately +130°. In general, output lobes145a,145bcan be directed more towards the horizontal (e.g., at an angle in the ranges from −90° to −135°, such as at approx. −90°, approx. −100°, approx. −110°, approx. −120°, approx. −130°, and from +90° to +135°, such as at approx. +90°, approx. +100°, approx. +110°, approx. +120°, approx. +130°.

The luminaire modules can include other features useful for tailoring the intensity profile. For example, in some implementations, luminaire modules can include an optically diffuse material that can diffuse light in a controlled manner to aid homogenizing the luminaire module's intensity profile. For example, surfaces242and244can be roughened or a diffusely reflecting material, rather than a specular reflective material, can be coated on these surfaces. Accordingly, the optical interfaces at surfaces242and244can diffusely reflect light, scattering light into broader lobes than would be provided by similar structures utilizing specular reflection at these interfaces. In some implementations these surfaces can include structure that facilitates various intensity distributions. For example, surfaces242and244can each have multiple planar facets at differing orientations. Accordingly, each facet will reflect light into different directions. In some implementations, surfaces242and244can have structure thereon (e.g., structural features that scatter or diffract light).

Surfaces246and248need not be surfaces having a constant radius of curvature. For example, surfaces246and248can include portions having differing curvature and/or can have structure thereon (e.g., structural features that scatter or diffract light). In certain implementations, a light scattering material can be disposed on surfaces246and248of optical extractor240.

In some implementations, optical extractor240is structured so that a negligible amount (e.g., less than 1%) of the light propagating within at least one plane (e.g., the x-z cross-sectional plane) that is reflected by surface242or244experiences TIR at light-exit surface246or248. For certain spherical or cylindrical structures, a so-called Weierstrass condition can avoid TIR. A Weierstrass condition is illustrated for a circular structure (i.e., a cross section through a cylinder or sphere) having a surface of radius R and a concentric notional circle having a radius R/n, where n is the refractive index of the structure. Any light ray that passes through the notional circle within the cross-sectional plane is incident on the surface of the circular structure and has an angle of incidence less than the critical angle and will exit the circular structure without experiencing TIR. Light rays propagating within the spherical structure in the plane but not emanating from within notional surface can impinge on the surface of radius R at the critical angle or greater angles of incidence. Accordingly, such light may be subject to TIR and won't exit the circular structure. Furthermore, rays of p-polarized light that pass through a notional space circumscribed by an area with a radius of curvature that is smaller than R/(1+n2)(−1/2), which is smaller than R/n, will be subject to small Fresnel reflection at the surface of radius R when exiting the circular structure. This condition may be referred to as Brewster geometry. Implementations may be configured accordingly.

Referring again toFIG. 2A, in some implementations, all or part of surfaces242and244may be located within a notional Weierstrass surface defined by surfaces246and248. For example, the portions of surfaces242and244that receive light exiting light guide230through end232can reside within this surface so that light within the x-z plane reflected from surfaces242and244exits through surfaces246and248, respectively, without experiencing TIR.

In the example implementations described above in connection withFIG. 2A, the luminaire module201is configured to output light into first and second backward angular ranges145′ and145″ and in third forward angular range145′″. In other implementations, the light guide-based luminaire module201is modified to output light into a single backward angular range145′.FIG. 2Bshows such light guide-based luminaire module201* configured to output light on a single side of the light guide is referred to as a single-sided luminaire module. The single-sided luminaire module201* is elongated along the x-axis like the luminaire module201shown inFIG. 2A. Also like the luminaire module201, the single-sided luminaire module201* includes a substrate205and LEEs210disposed on a surface of the substrate205along the x-axis to emit light in a first angular range. The single-sided luminaire module201* further includes optical couplers220arranged and configured to redirect the light emitted by the LEEs210in the first angular range into a second angular range125that has a divergence smaller than the divergence of the first angular range at least in the x-z cross-section. Also, the single-sided luminaire module201* includes a light guide230to guide the light redirected by the optical couplers220in the second angular range125from a first end231of the light guide to a second end232of the light guide. Additionally, the single-sided luminaire module201* includes a single-sided extractor (denoted240*) to receive the light guided by the light guide230. The single-sided extractor240* includes a redirecting surface244to redirect some of the light received from the light guide230into a third angular range138′, like described for luminaire module201with reference toFIG. 2A, and an output surface248to output the light redirected by the redirecting surface244in the third angular range138′ into a first backward angular range145′. Also as described inFIG. 2A, the redirecting surface244is configured to leak some the light received from the light guide230into a third forward angular range145′″.

A light intensity profile of the single-sided luminaire module201* is represented inFIG. 2Cas the first output lobe145aand the third output lobe145c. The output lobe145acorresponds to light output by the single-sided luminaire module201* in the first backward angular range145′ and the output lobe145ccorresponds to light output by the single-sided luminaire module201* in the third forward angular range145′″.

In general, the light guide luminaire module200* can be combined with a single tertiary reflector to provide (i) indirect illumination to a first portion of a target surface from light output by the light guide luminaire module200* in the first backward angular range145′ and redirected by the tertiary reflector to a first forward angular range155′, and (ii) direct illumination to a second, different portion of the target surface from light output by the light guide luminaire module200* in the third forward angular range145′″. Further, the light guide luminaire module200can be combined with a pair of tertiary reflectors to provide (i) indirect illumination to first and second different portions of a target surface from light output by the light guide luminaire module200in the respective first and second backward angular ranges145′,145″ and respectively redirected by the tertiary reflectors to first and second forward angular ranges155′,155″, and (ii) direct illumination to a third portion of the target surface, different from the first and second portions, from light output by the light guide luminaire module200in the third forward angular range145′″. An example of the latter combination is described below.

First Embodiment of Troffer Luminaire Including Light Guide Luminaire Module and Tertiary Reflectors

FIG. 3Ashows a troffer luminaire300that includes a light guide luminaire module301and tertiary reflectors370′,370″. The light guide luminaire module301can be implemented as the light guide luminaire module201described above in connection withFIG. 2A. The troffer luminaire300also includes a housing302that supports the light guide luminaire module301and the tertiary reflectors370′,370″. While a plurality of LEEs and the optical couplers of the light guide luminaire module301are housed within the housing302(and not visible inFIG. 3A), a light guide330of light guide luminaire module protrudes from the housing to lower an optical extractor340of light guide luminaire module by a distance D along the z-axis comparable to a sag of the tertiary reflectors370′,370″ in the (y,z) plane. The housing302and the tertiary reflectors370′,370″ can be formed of extruded aluminum. In this example, the tertiary reflectors370′,370″ are closed off at two ends by walls375. InFIG. 3A, one of walls375is illustrated in cut away to better show a portion of light guide330and optical extractor340.

In some embodiments, the troffer luminaire300includes a transparent plate positioned, for example, to form, together with the tertiary reflectors370′,370″, an enclosure to protect the light guide luminaire module301from dust or other environmental effects. In some cases, the troffer luminaire300can have a 2′×2′ or 2′×4′ footprint (e.g., in the x-y plane), corresponding to the size of conventional fluorescent light luminaires.

A surface of the first tertiary reflector370′ is treated to specularly reflect light output by the light guide luminaire module301in a first backward angular range145′ towards a first portion of a target surface in a first forward angular range155′. And, a surface of the second tertiary reflector370″ is treated to specularly reflect light output by the light guide luminaire module301in a second backward angular range145″ towards a second portion of the target surface in a second forward angular range155″. Moreover, a redirecting surface of the optical extractor340is semitransparent to transmit part of the guided light in a third forward angular range145′″ towards a third portion of the target surface, where the third portion is sandwiched between the first and second portions.FIG. 3Bshows an example distribution390of intensity of light provided by the troffer luminaire300to a target. The light intensity distribution390includes a first output lobe155a′ corresponding to light issued by the troffer luminaire300in the first forward angular range155′, a second output lobe155b′ corresponding to light issued by the troffer luminaire in the second forward angular range155″, and a third output lobe145c′ corresponding to light issued by the troffer luminaire in the third forward angular range145′″.

As described above, composition and geometry of components of the light guide luminaire module301determine the shape, angular orientation and magnitude of the output lobes155a′,155b′ and145c′ of the light intensity distribution390associated with the troffer luminaire300. For example, in some embodiments, the optical extractor340and the tertiary reflectors370′,370″ can be configured to direct substantially all of the light into a range of angles between 315° and 45° in a cross-sectional plane of the luminaire300, where 0° corresponds to the forward direction. The forward direction is parallel to the light guide330, and can be toward the floor for a troffer luminaire300mounted on a ceiling. The first and second output lobes155a′ and155b′ have respective maxima at about 330° and 30° and a width of less than 10° each. The third output lobe145c′ has a batwing profile and fills a polar space between the first and second output lobes155a′ and155b′. The troffer luminaire300is configured to direct little or no illumination into certain angular ranges, e.g., close to the plane of the ceiling to avoid glare. For example, in the present example, the troffer luminaire300directs almost no illumination in ranges from 55° to 90° and from 270° to 305° relative to the forward direction. This may be advantageous because illumination propagating from a troffer luminaire at such shallow angles can be perceived as glare in certain applications (e.g., in office lighting).

Referring again toFIG. 3A, note while a combination of shapes and relative orientations of the optical extractor340of the light guide luminaire module301and the tertiary reflectors370′,370″ have been configured to obtain a specified intensity distribution (e.g.,390) of the light output by the troffer luminaire300, the foregoing combination does not necessarily ensure that luminance across each of the tertiary reflectors satisfies a certain specified luminance uniformity. Example troffer luminaires that satisfy the latter specification are described below.

Second Embodiment of Troffer Luminaire Including Light Guide Luminaire Module and Tertiary Reflectors

FIGS. 4A-4Bshow a side view and a perspective view, respectively, of a troffer luminaire400that includes a light guide luminaire module401and tertiary reflectors470′,470″. Solid state light sources, optical couplers and a light guide of the light guide luminaire module401can be implemented like the corresponding components of the light guide luminaire module201described above in connection withFIG. 2A. An optical extractor440of the light guide luminaire module401is mirror symmetric relative to the z-axis (which coincides with the optical axis of the light guide luminaire module401) and can be implemented as described below in connection withFIGS. 5A-5F. Respective “front faces” (referred to as reflective surfaces) of the tertiary reflectors470′,470″, that face the light guide luminaire module401, can be implemented as described below in connection withFIG. 5G, while “rear faces” can be implemented as a solid block or can have other forms/shapes. Note that while the plurality of solid state light sources and the optical couplers of the light guide luminaire module401are housed within the housing402(and not visible inFIGS. 4A-4B), the light guide of light guide luminaire module protrudes from the housing to lower the optical extractor440of light guide luminaire module by a distance D along the z-axis comparable to a sag of the tertiary reflectors470′,470″ in the (y,z) plane. The light guide luminaire module401and the tertiary reflectors470′,470″ are elongated along the x-axis and can have a length L of about 2′ or 4′, corresponding to the size of conventional fluorescent light luminaires.

In this implementation, output surfaces of the optical extractor440of the light guide luminaire module401, and corresponding reflective surfaces of the tertiary reflectors470′,470″ are shaped and arranged with respect to one another such that each of the tertiary reflectors470′,470″ appears to be uniformly lit when viewed by an observer of the troffer luminaire400from directly underneath the optical extractor. For example, a ratio of maximum luminance to minimum luminance across each of the tertiary reflectors470′,470″ can be lower than 5:1, 4:1 or 3:1. In this manner, the observer can view a fully lit surface of each of the tertiary reflectors470′,470″ free of dark regions and/or hot spots.

FIG. 5Ais a cross-section in the (y-z) plane of an example implementation of the optical extractor440of the light guide luminaire module401. The optical extractor440is formed from a solid material (with refractive index n>1). For example, the material can be glass with a refractive index of about 1.5. As another example, the material can be plastic with a refractive index of about 1.5-1.6. In this implementation, the optical extractor440includes an input surface441centered on the optical axis of the light guide (here, the z-axis); a first backward output surface442aand a second backward output surface442barranged to mirror each other relative to the z-axis; a first forward output surface443aand a second forward output surface443barranged to mirror each other relative to the z-axis; a first redirecting surface444aand a second redirecting surface444barranged to mirror each other relative to the z-axis; and a third forward output surface445centered on the z-axis and opposing the input surface. Note that the first/second backward output surface442a/442bintersects the first/second forward output surface443a/443bat edge446a/446b. Additionally, the first/second redirecting surface444a/444bintersects the first/second forward output surface443a/443bat vertex447a/447b.

The input surface441is formed from a first input interface441a(also referred to as the 1stinterface), which is represented above the z-axis in this example, and a second input interface441b(also referred to as the 2ndinterface), which is represented below the z-axis in this example.FIG. 5Bis a cross-section in the (y-z) plane of the 1stinterface441a—the z and y axes have different scaling. Coordinates of a polyline corresponding to the 1stinterface441aare given in Table 1. Coordinates of another polyline corresponding to the 2ndinterface441bhave sign-opposite y-values and same z-values as the coordinates given in Table 1.

The input surface441of the optical extractor440can be bonded to an output end of the light guide of the light guide luminaire module401(e.g., as described above in connection withFIG. 2A). In such case, an anti-reflective coating may be disposed between the output end of the light guide and optical extractor440. If the material of the optical extractor440is different from the material from which the light guide is formed, for example an index matching layer may be disposed between the output end of the light guide and optical extractor440. In other cases, the light guide and the optical extractor440can be integrally formed.

FIG. 5Cis a cross-section in the (y-z) plane of the 1stbackward output surface442a. Coordinates of nodes for a fitted curve, e.g., a spline, corresponding to the first backward output surface442aare given in Table 2. Coordinates of another spline corresponding to the 2ndbackward output surface442bhave sign-opposite y-values and same z-values as the coordinates given in Table 2.

Here, the first/second backward output surface442a/442bof the optical extractor440is convex and, along with the first/second redirecting surface444a/444band a reflective surface of the first/second tertiary reflector470′/470″, plays a major role in determining the luminance uniformity across the first/second tertiary reflector. Note that point 31 of the first/second backward output surface442a/442bcorresponds to the edge446a/446bwhere the first/second backward output surface intersects the first/second forward output surface443a/443b. In some implementations, the first/second backward output surface442a/442bis uncoated. In other implementations, an anti-reflective coating may be provided on the first/second backward output surface442a/442bsuch that light reflected by the first/second redirecting surface444a/444bcan transmit with minimal back reflection. In other implementations, the first/second backward output surface442a/442bis coated with a diffusive coating (e.g., BrightView M PR05™ or BrightView M PR10™). In such cases, the light reflected by the first/second redirecting surface444a/444bcan diffuse upon transmission through the first/second backward output surface442a/442b.

FIG. 5Dis a cross-section in the (y-z) plane of the 1stforward output surface443a. Coordinates of a polyline corresponding to the first forward output surface443aare given in Table 3. Coordinates of another polyline corresponding to the 2ndforward output surface443ahave sign-opposite y-values and same z-values as the coordinates given in Table 3.

Here, the first/second forward output surface443a/443bof the optical extractor440is flat (or has a curvature that varies around zero). Note that point 1 of the first/second forward output surface443a/443bcorresponds to the edge446a/446bwhere the first/second forward output surface intersects the first/second backward output surface442a/442b; point 2 of the first/second forward output surface443a/443bcorresponds to the vertex447a/447bwhere the first/second forward output surface intersects the first/second redirecting surface444a/444b. In some implementations, the first/second forward output surface443a/443bis uncoated. In other implementations, an anti-reflective coating may be provided on the first/second forward output surface443a/443bsuch that guided light provided through the input surface441that reaches the first/second forward output surface can transmit there through with minimal back reflection. In other implementations, the first/second forward output surface443a/443bis coated with a diffusive coating (e.g., BrightView M PR05™ or BrightView M PR10™). In such cases, guided light provided through the input surface441that reaches the first/second forward output surface443a/443bcan diffuse upon transmission there through.

FIG. 5Eis a cross-section in the (y-z) plane of the 1stredirecting surface444a. Coordinates of nodes for a fitted curve, e.g., a spline, corresponding to the first redirecting surface444aare given in Table 4. Coordinates of another spline corresponding to the 2ndredirecting surface444bhave sign-opposite y-values and same z-values as the coordinates given in Table 4.

Here, the first/second redirecting surface444a/444bof the optical extractor440is flat (i.e., has a curvature that varies around zero) or it is concave and, along with the first/second backward output surface442a/442band a reflective surface of the first/second tertiary reflector470′/470″, plays a major role in determining the luminance uniformity across the first/second tertiary reflector. Note that point 1 of the first/second redirecting surface444a/444bcorresponds to the vertex447a/447bwhere the first/second redirecting surface intersects the first/second forward output surface443a/443b. In some implementations, the first/second redirecting surface444a/444bis uncoated. In such cases, guided light from the input surface441that impinges on the first/second redirecting surface444a/444bat angles beyond a critical angle θ=arcsine(1/n) relative to the respective surface normal reflects off the first/second redirecting surface via total internal reflection (TIR) towards the first/second backward output surface442a/442b. In other implementations, the first/second redirecting surface444a/444bis coated with a reflective coating. In such cases, guided light from the input surface441that impinges on the first/second redirecting surface444a/444breflects off via specular reflection or diffuse reflection or a combination thereof towards the first/second backward output surface442a/442b.

FIG. 5Fis a cross-section in the (y-z) plane of a portion445aof the third forward output surface445. Coordinates of nodes for a fitted curve, e.g., a spline, corresponding to the portion445aof the third forward output surface445are given in Table 5. Coordinates of another spline corresponding to portion445bof the third forward output surface445have sign-opposite y-values and same z-values as the coordinates given in Table 5.

TABLE 5portion 445a of third forward output surface 445Pointz (mm)y (mm)16.600.8126.560.7436.510.6646.460.5856.420.5066.370.4276.330.3486.300.2696.270.17106.260.09116.250

Here, the third forward output surface445of the optical extractor440is concave. Note that slope448a(and448b—not shown inFIG. 5A or 5F) is continuous at the intersection of the portion445a/445bof third forward output surface445with the first/second redirecting surface444a/444b. In this manner, there are no vertices between the third forward output surface445and the adjacent first and second redirecting surfaces444a,444b. Also note that the third forward output surface445intersects the z-axis with a slope parallel to the y-axis. In some implementations, the third forward output surface445is uncoated. In other implementations, an anti-reflective coating may be provided on the third forward output surface445such that guided light provided through the input surface441that reaches the third forward output surface can transmit there through with minimal back reflection. In other implementations, the third forward output surface445is coated with a diffusive coating (e.g., BrightView M PR05™ or BrightView M PR10™). In such cases, guided light provided through the input surface441that reaches the third forward output surface445can diffuse upon transmission there through.

Note that a total depth of the optical extractor440in the forward direction (e.g., along the z-axis) is less than 14 mm (or about 0.5″), and a total width of the optical extractor in an orthogonal direction (e.g., along the y-axis) is about 24 mm (or less than 1″).

FIG. 5Gis a cross-section in the (y-z) plane of the reflective surface of the second tertiary reflector470″. Coordinates of nodes for a fitted curve, e.g., a spline, corresponding to the reflective surface of the second tertiary reflector470″ are given in Table 6. Coordinates of another spline corresponding to the reflective surface of the first tertiary reflector470′ have sign-opposite y-values and same z-values as the coordinates given in Table 6.

TABLE 6reflective surface of second tertiary reflector 470″Pointy (mm)z (mm)10029.50319.00428.50538.00647.50757.00866.50976.001085.501195.0012104.5013114.0014123.5015133.0016142.5017152.0−0.0118161.50.4119171.01.1920180.52.4921190.04.4222199.57.0323209.010.3324218.514.2725228.018.7826237.523.7727247.029.1028256.534.6729266.040.4030275.546.2831285.052.39

Here, the reflective surface of the first/second tertiary reflector470′/470″ is concave and, along with the first/second redirecting surface444a/444band the first/second backward output surface442a/442bof the optical extractor440, plays a major role in determining the luminance uniformity across the first/second tertiary reflector. In this embodiment of the first/second tertiary reflector470′/470″ a portion of the reflective surface adjacent to the housing402is flat and a remaining portion of the reflective surface that is remote from the housing402is concave. The reflective surface of the first/second tertiary reflector470′/470″ is coated with a reflective coating. In such cases, light from the first/second backward output surface442a/442bof the optical extractor440that impinges on the reflective surface of the first/second tertiary reflector470′/470″ reflects off via specular reflection or diffuse reflection or a combination thereof towards the first/second backward output surface442a/442b. An example of diffusive coatings that can be used to cover the reflective surface of the first/second tertiary reflector470′/470″ is WhiteOptics White 98 F16™ (high angle diffusive film).

Note that a sag in the forward direction (e.g., along the z-axis) of the first/second tertiary reflector470′/470″ is less than 55 mm (or about 2″), and a span in an orthogonal direction (e.g., along the y-axis) of the first/second tertiary reflector is 285 mm (or about than 11″). The latter dimension of the first/second tertiary reflector470′/470″ and a thickness (along the y-axis) of order less than 1″ for the housing402that supports the light guide luminaire module401and the first and second tertiary reflectors causes the troffer luminaire400to have a total span (along the y-axis) of 23-24″. The forward output surfaces443a/bof the extractor in this example are located at about 90% of the sag that is at z˜47 mm. The forward output surfaces443a/bof the extractor may be located between 70% to 95% of the sag, that is between about z˜36 mm to z˜50 mm with varying effects on the uniform appearance of respective troffer luminaires.

The above-described combination of shapes and relative orientations of the first/second redirecting surface444a/444band the first/second backward output surface442a/442bof the optical extractor440and of the reflective surface of the first/second tertiary reflector470′/470″ was used to design the troffer luminaire400for which a ratio of maximum luminance to minimum luminance across each of the tertiary reflectors470′,470″ is lower than 3:1, as shown below in connection withFIG. 10.

Moreover, (i) a choice of diffusive coatings applied on the transmissive first/second backward output surface442a/442bof the optical extractor440of the light guide luminaire module401and reflective surface of the first/second tertiary reflector470′/470″—which influences, at least in part, a total amount of indirect light visible by an observer underneath the troffer luminaire400—and (ii) another choice of diffusive coatings applied on the transmissive first/second forward output surface443a/443band third forward output surface445of the optical extractor—which influences, at least in part, a total amount of direct light visible by the observer underneath the troffer luminaire—were made to design the troffer luminaire400for which another ratio of maximum luminance to minimum luminance across each of the tertiary reflectors470′,470″ and the bottom side of the optical extractor is lower than 15:1, as shown below in connection withFIG. 10.

Other troffer luminaires that use a light guide luminaire module and only a single tertiary reflector also can be designed to satisfy specified luminance uniformities, as described below.

Third Embodiment of Troffer Luminaire Including Light Guide Luminaire Module and a Tertiary Reflector

FIG. 6Ashows a side view of a troffer luminaire600that includes a light guide luminaire module601and a single tertiary reflector670. Solid state light sources, optical couplers and a light guide of the light guide luminaire module601can be implemented like the corresponding components of the light guide luminaire module201* described above in connection withFIG. 2B. An optical extractor640of the light guide luminaire module601lacks mirror symmetry relative to the optical axis of the light guide luminaire module601(parallel to the z axis) and can be implemented as described below in connection withFIG. 6B. A “front face” (referred to as a reflective surface) of the tertiary reflector670, that faces the light guide luminaire module601, can be implemented in a manner similar to the one described above in connection withFIGS. 1 and 5G, while a “rear face” can be implemented as a solid block or can have other forms/shapes. Note that while the plurality of solid state light sources and the optical couplers of the light guide luminaire module601are housed within the housing602(and not visible inFIG. 6A), the light guide of light guide luminaire module protrudes from the housing to lower the optical extractor640of light guide luminaire module by a distance D along the z-axis comparable to a sag of the tertiary reflector670in the (y,z) plane. The light guide luminaire module601and the tertiary reflector670are elongated along the x-axis (e.g., as shown inFIG. 2B) and can have a length L of about 2′ or 4′, corresponding to the size of conventional fluorescent light luminaires.

In this implementation, output surfaces of the optical extractor640of the light guide luminaire module601, and the reflective surface of the tertiary reflector670are shaped and arranged with respect to one other such that the tertiary reflector670appears to be uniformly lit when viewed by an observer of the troffer luminaire600from directly underneath the optical extractor. For example, a ratio of maximum luminance to minimum luminance across the tertiary reflector670can be lower than 5:1, 4:1 or 3:1. In this manner, the observer can view a fully lit surface of the tertiary reflector670free of dark regions and/or hot spots.

FIG. 6Bis a cross-section in the (y-z) plane of an example implementation of the optical extractor640of the light guide luminaire module601. Note that the optical extractor640is a single-sided optical extractor like the optical extractor240* described above in connection withFIG. 2B. The optical extractor640is formed from a solid material (with refractive index n>1). For example, the material can be glass with a refractive index of about 1.5. As another example, the material can be plastic with a refractive index of about 1.5-1.6. In this implementation, the optical extractor640includes an input surface641centered on the optical axis of the light guide (here, the z-axis); a forward output surface643opposing the input surface641; a backward output surface642extending from the input surface641to the forward output surface643; and a redirecting surface644extending from the input surface641to the forward output surface643and opposing the backward output surface642. Note that the backward output surface642intersects the forward output surface643at edge646. Additionally, redirecting surface644intersects the forward output surface643at vertex647.

The input surface641of the optical extractor640can be bonded to an output end of the light guide of the light guide luminaire module601(e.g., as described above in connection withFIG. 2B). In such case, an anti-reflective coating may be disposed between the output end of the light guide and optical extractor640. If the material of the optical extractor640is different from the material from which the light guide is formed, for example an index matching layer may be disposed between the output end of the light guide and optical extractor640. In other cases, the light guide and the optical extractor640can be integrally formed.

The backward output surface642of the optical extractor640is convex and, along with the redirecting surface644and the reflective surface of the tertiary reflector670, plays a major role in determining the luminance uniformity across the tertiary reflector. In some implementations, the backward output surface642is uncoated. In other implementations, an anti-reflective coating may be provided on the backward output surface642such that light reflected by the redirecting surface644can transmit with minimal back reflection. In other implementations, the backward output surface642is coated with a diffusive coating (e.g., BrightView M PR05™ or BrightView M PR10™). In such cases, the light reflected by the redirecting surface644can diffuse upon transmission through the backward output surface642.

The forward output surface643of the optical extractor640is flat (or has a curvature that varies around zero). In some implementations, the forward output surface643is uncoated. In other implementations, an anti-reflective coating may be provided on the forward output surface643such that guided light provided through the input surface641that reaches the forward output surface can transmit there through with minimal back reflection. In other implementations, the forward output surface643is coated with a diffusive coating (e.g., BrightView M PR05™ or BrightView M PR10™). In such cases, guided light provided through the input surface641that reaches the forward output surface643can diffuse upon transmission there through.

The redirecting surface644of the optical extractor640has a complex shape and, along with the backward output surface642and the reflective surface of the tertiary reflector670, plays a major role in determining the luminance uniformity across the tertiary reflector. For example, the redirecting surface644is flat (i.e., has a curvature that varies around zero) over a portion adjacent the forward output surface643and convex over another portion adjacent the input surface641. As another example, the redirecting surface644has an inflection point, i.e., is concave over a portion adjacent the forward output surface643and convex over another portion adjacent the input surface641. In some implementations, the redirecting surface644is uncoated. In such cases, guided light from the input surface641that impinges on the redirecting surface644at angles beyond a critical angle θ=arcsine(1/n) relative to the respective surface normal reflects off the first/second redirecting surface via total internal reflection (TIR) towards the backward output surface642. In other implementations, the redirecting surface644is coated with a reflective coating. In such cases, guided light from the input surface641that impinges on the redirecting surface644reflects off via specular reflection or diffuse reflection or a combination thereof towards the backward output surface642.

Referring again toFIG. 6A, the reflective surface of the tertiary reflector670is concave and, along with the redirecting surface644and the backward output surface642of the optical extractor640, plays a major role in determining the luminance uniformity across the tertiary reflector. The reflective surface of the tertiary reflector670is coated with a reflective coating. In such cases, light from the backward output surface642of the optical extractor640that impinges on the reflective surface of the tertiary reflector670reflects off via specular reflection or diffuse reflection or a combination thereof towards the first/second backward output surface442a/442b. An example of diffusive coating that can be used to cover the reflective surface of the tertiary reflector670is WhiteOptics White 98 F16™ (high angle diffusive film).

The above-described combination of shapes and relative orientations of the redirecting surface644and the backward output surface642of the optical extractor640and of the reflective surface of the tertiary reflector670can be used to design the troffer luminaire600for which a ratio of maximum luminance to minimum luminance across the tertiary reflector670is lower than a first specified uniformity ratio, e.g., 3:1.

Moreover, (i) a choice of diffusive coatings applied on the transmissive backward output surface642of the optical extractor640of the light guide luminaire module601and the reflective surface of the tertiary reflector670—which influences, at least in part, a total amount of indirect light visible by an observer underneath the troffer luminaire600—and (ii) another choice of diffusive coatings applied on the transmissive forward output surface642of the optical extractor which influences, at least in part, a total amount of direct light visible by the observer underneath the troffer luminaire—can be made to design the troffer luminaire600for which another ratio of maximum luminance to minimum luminance across the tertiary reflector670and the bottom side of the optical extractor is lower than a second specified uniformity ratio, e.g., 15:1.

Samples of the troffer luminaire400, described above in connection withFIGS. 4A-4B and 5A-5G, have been fabricated and experiments have been conducted to evaluate their respective performance. Some of these experiments are summarized below.

Experimental Results for the Second Embodiment of Troffer Luminaire

To carry out the following experiments, the solid state light sources of the light guide luminaire module401used in the troffer luminaire400were implemented as either Luxeon Z ES (with one LED per channel of the optical couplers320) or Luxeon Z (with two LEDs per channel of the optical couplers). For either of the foregoing implementations, the LEDs were modeled using ray data sets supplied by Lumileds™. The first and second backward output surfaces442a,442bof the optical extractor440were left uncovered or were covered with a diffuse film implemented as either Brightview MPR05™ or Brightview MPR10™. For either of the foregoing implementations, characteristics of the diffusive surfaces were modeled using BSDF data files supplied by Brightview™. Moreover, the reflective surface of the tertiary reflectors470′,470″ was covered with a diffuse film implemented as WhiteOptics White 98 F16™ (high angle diffusive film). Additionally, a width (along the x-axis) of the light guide luminaire module401and the tertiary reflectors470′,470″ included in the troffer luminaire400is L=0.578 m.

Some experimental results for the troffer luminaire400that includes (i) the light guide luminaire module401with the optical extractor440and (ii) the tertiary reflectors470′,470″ are summarized in Table 7. Here, the light source of the light guide luminaire module401is based on Luxeon Z (i.e., with two LEDs per channel of the optical couplers: 2×42 lm=48 lm per channel). As the light guide luminaire module401has 48 channels, the total power emitted by the light source of the light guide luminaire module is 4032 lm. The foregoing light source is simulated using 2e+6 rays. Unless otherwise specified, the diffusive film applied on the first and second backward output surfaces442a,442bof the optical extractor440is Brightview MPR10™. All power levels in Table 7 are in lumens and are measured using a far-field detector.

TABLE 7ResultValuePower measured in far field (w/o diffusive film on backward output3709surfaces 442a, 442b)Overall Total efficiency (w/o diffusive film on backward output92%surfaces 442a, 442b)Power measured in far field3356Overall Total efficiency83%Power corresponding to direct illumination (due to light683provided from forward output surfaces 443a, 443b, 445)Power corresponding to indirect illumination (due to light2673output through backward output surfaces 442a, 442b and thenprovided from tertiary reflectors 470′, 470″)Ratio direct to indirect26%

Additional experiments were performed on the troffer luminaire400using an experimental setup shown inFIG. 7. Here, the troffer luminaire400is arranged with the light guide of its light guide luminaire module401parallel to the z-axis and has its elongated dimension aligned with the x-axis. To characterize illumination of a wall of a room in which the troffer luminaire400is installed, illuminance (in Lux) is measured for light provided by the troffer luminaire to a first planar detector701disposed parallel to the (x,z) plane and spaced apart by a distance d701from the extractor440of the light guide luminaire module401. Further, to characterize illumination of the floor underneath the troffer luminaire400, illuminance (in Lux) is measured for light provided by the troffer luminaire to a second planar detector702disposed parallel to the (x,y) plane and spaced apart by a distance d702from the extractor440of the light guide luminaire module401. Furthermore, to determine whether each of the tertiary reflectors470′,470″ and the bottom side of the optical extractor440of the light guide luminaire module401appear to be uniformly lit when observed from directly underneath the optical extractor, luminance (in Nits) is measured across each of the tertiary reflectors and the bottom side of the optical extractor by “looking through” a third aperture detector703disposed parallel to the (x,y) plane and spaced apart by a distance d703below the optical extractor. Table 8 summarizes configurations of the detectors used in this study.

Results of the additional experiments performed on the troffer luminaire400using the experimental setup shown inFIG. 7are described below.

FIG. 8shows an illuminance (x,z)-contour plot802measured by the first planar detector701(see Table 8) for light output by the troffer luminaire400.FIG. 8also shows a z-axis cross-section804that represents vertical variation of the illuminance for light output by the troffer luminaire400at the center of the first planar detector701, and an x-axis cross-section806that represents horizontal variation of the illuminance for light output by the troffer luminaire at half height of the first planar detector. Theses experimental results indicate vertical and horizontal uniformity of illumination provided by the light output by the troffer luminaire400to a “lateral wall” disposed parallel to the side surfaces of the light guide of the light guide luminaire module401included in the troffer luminaire.

FIG. 9shows an illuminance (x,y)-contour plot902measured by the second planar detector702(see Table 8) for light output by the troffer luminaire400.FIG. 9also shows a y-axis cross-section904that represents first variation of the “floor illuminance” along a first direction orthogonal to the elongation of the light guide luminaire module401included in the troffer luminaire400. Additionally,FIG. 9shows an x-axis cross-section906that represents second variation of the floor illuminance along a second direction parallel to the elongation of the light guide luminaire module401included in the troffer luminaire400.

FIG. 10shows a luminance (x,y)-contour plot1002measured looking through the third aperture detector703(see Table 8) at light output by the troffer luminaire400. The dotted-line rectangle overlaid onto the luminance (x,y)-contour plot1002indicates a footprint of the tertiary reflectors470′,470″ of the troffer luminaire400.FIG. 10also shows a y-axis cross-section1004that represents first variation of the luminance of the troffer luminaire400across the first tertiary reflector470′, the bottom of the extractor440of the light guide luminaire module401and the second tertiary reflector470″ of the troffer luminaire. The dotted lines overlaid onto the y-axis cross-section1004indicate edges of the tertiary reflectors470′,470″ of the troffer luminaire400. Additionally,FIG. 10shows an x-axis cross-section1006that represents second variation of the luminance of the troffer luminaire400along the bottom of the extractor440of the light guide luminaire module401of the troffer luminaire. The dotted lines overlaid onto the x-axis cross-section1006indicate edges of the tertiary reflectors470′,470″ of the troffer luminaire400.

The results summarized in plots1002,1004and1006ofFIG. 10indicate that the choice of shapes and relative orientations of the first/second redirecting surface444a/444band the first/second backward output surface442a/442bof the optical extractor440and of the reflective surface of the first/second tertiary reflector470′/470″ that was made for designing the troffer luminaire400led to a ratio of maximum luminance to minimum luminance across each of the tertiary reflectors470′,470″ that is lower than 3:1. In this manner, each of the tertiary reflectors170′,170″ appears to be uniformly lit, free of dark regions and/or hot spots, when viewed by an observer of the troffer luminaire400from directly underneath the optical extractor.

Additionally, the results summarized in plots1002,1004and1006ofFIG. 10further indicate that (i) the choice of diffusive coatings applied on the transmissive first/second backward output surface442a/442bof the optical extractor440of the light guide luminaire module401and reflective surface of the first/second tertiary reflector470′/470″—which influences, at least in part, a total amount of indirect light visible by an observer underneath the troffer luminaire400—and (ii) the other choice of diffusive coatings applied on the transmissive first/second forward output surface442a/442band third forward output surface445of the optical extractor—which influences, at least in part, a total amount of direct light visible by the observer underneath the troffer luminaire that were made for designing the troffer luminaire400led to another ratio of maximum luminance to minimum luminance across each of the tertiary reflectors470′,470″ and the bottom side of the optical extractor that is lower than 15:1.

The preceding figures and accompanying description illustrate example methods, systems and devices for illumination. It will be understood that these methods, systems, and devices are for illustration purposes only and that the described or similar techniques may be performed at any appropriate time, including concurrently, individually, or in combination. In addition, many of the steps in these processes may take place simultaneously, concurrently, and/or in different orders than as shown. Moreover, the described methods/devices may use additional steps/parts, fewer steps/parts, and/or different steps/parts, as long as the methods/devices remain appropriate.

In other words, although this disclosure has been described in terms of certain aspects or implementations and generally associated methods, alterations and permutations of these aspects or implementations will be apparent to those skilled in the art. Accordingly, the above description of example implementations does not define or constrain this disclosure. Further implementations are described in the following claims.