Patent Description:
Point sources of light such as light emitting diodes (LEDs) introduce flexibility but also challenges in the design of architectural luminaires. In some design contexts it is desirable to have luminaires with very narrow channels from which light exits. One challenge in designing such narrow aperture luminaires is minimizing high angle glare while simultaneously outputting sufficient light from the narrow aperture to illuminate a work space. Glare is an effect of luminance at high angles that can cause visual discomfort to users. Another challenge is providing aesthetically pleasing homogenous light at the exit surface, that is, light that appears to be uniform and "clean" despite the fact that the light is coming from point sources of light. Narrow aperture luminaires that reduce or eliminate high angle glare and provide homogenous light are desirable.

<CIT> describes a light guide used in a luminaire used for workspace illumination comprising an elongated base comprising a light emitting surface and opposing major faces and a plurality of collimators, wherein each collimator comprises a light receiving surface and substantially all light received at the light receiving surfaces internally reflects through the collimators and the base and emits from the light emitting surfaces.

<CIT> describes a luminaire comprising a light guide, a plurality of light sources in optical communication with light receiving surfaces, a board onto which the plurality of light sources are mounted, and a housing comprising side walls extending beyond a plane defined by the light emitting surface and an upside down U-shaped cross-section with an open distal end.

The accompanying drawings illustrate non-limiting example embodiments of the invention.

Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.

The term "proximal" as used herein with respect to features of the light guide means a position relatively closer to a plane defined by a light source for the light guide, and the term "distal" as used herein means a position relatively farther away from the plane defined by the light source for the light guide. Arrow <NUM> in <FIG> illustrates the proximal direction, and arrow <NUM> in <FIG> illustrates the distal direction.

The term "longitudinal" or "longitudinally" as used herein with respect to features of the light guide means a direction or orientation parallel to the proximal/distal axis, and the term "lateral" or "laterally" as used herein with respect to features of the light guide means a direction or orientation normal to the proximal/distal axis.

Aspects of the invention relate to light guides having a plurality of collimators projecting from an elongated base. The collimators reduce the angle of light. The base has flutes which homogenize light. Additional features described herein also reduce the angle of light and homogenize light. Aspects of the invention define luminaires incorporating such light guides.

<FIG> show a light guide <NUM>. Light guide <NUM> has a plurality of collimators <NUM> and a laterally elongated base <NUM>. Collimator <NUM> has a light receiving surface <NUM> at its proximal end. Base <NUM> has a light emitting surface <NUM> at its distal end. As described herein, substantially all light received at light receiving surface <NUM> of collimators <NUM> internally reflects through collimators <NUM> and base <NUM> and is emitted from light emitting surface <NUM>. In some embodiments light emitting surface may comprise texture elements <NUM>, for example dimples, bumps , flutes (e.g. running parallel or perpendicular to the lateral extent of base <NUM>), or cross-hatched flutes, as shown for example in <FIG>.

Collimators <NUM> project from base <NUM> in a proximal direction <NUM>. Collimators <NUM> are arranged in a side-by-side immediately adjacent manner along base <NUM>. Collimators <NUM> and base <NUM> may be integrally formed and have a unitary structure.

Light guide <NUM> is shown with two collimators <NUM> to conveniently illustrate details. In most embodiments the light guide has a base that would be more elongated laterally (either linearly or in any other manner), and would comprise a correspondingly greater number of collimators, for example to provide sufficient length for the light guide to conform to a desired shape and size of the luminaire (e.g. the embodiments shown in <FIG>, <FIG> and <FIG>). Light guides of the present invention, viewed from above or below, may be linear, curved, circular, polygonal or any other open or closed shape. In some embodiments, the light guide may have at least <NUM>, or at least <NUM>, or at least <NUM> or at least <NUM>, or at least <NUM>, collimators. In some embodiments a plurality of identically-shaped and/or differently-shaped light guides may be combined to the desired shape and size of the luminaire.

Collimators <NUM> may be identical in size and shape. Collimator <NUM> has a rectangular frustum shape that expands laterally outwardly in a distal direction <NUM>. The four sides of collimator <NUM> comprise a pair of opposing first faces <NUM>, <NUM>' and a pair of second side faces <NUM>, <NUM>'.

<FIG> shows the angle <NUM> of second faces <NUM>, <NUM>' relative to a plane <NUM> defined by light receiving surface <NUM>. <FIG> shows the angle <NUM> of first faces <NUM>, <NUM>' relative to a plane <NUM> defined by light receiving surface <NUM>. Angles <NUM> and <NUM> may be affected by a number of factors including:.

According to the claimed invention, angles <NUM> and <NUM> are not equal. This is due to the path length difference between the two orientations caused by base <NUM>, that is, light affected by angle <NUM> experiences more reactions (interacting with first surfaces <NUM>, <NUM>' and major surfaces <NUM>, <NUM>') while light affected by angle <NUM> primarily only interacts with second surfaces <NUM>, <NUM>'.

According to the claimed invention, angle <NUM> ranges from <NUM> to <NUM> degrees, or from <NUM> to <NUM> degrees, or from <NUM> to <NUM> degrees. Angle <NUM> ranges from <NUM> to <NUM> degrees.

Base <NUM> is rectangular and laterally elongated, for example in a manner dictated by the desired shape of the luminaire, that is, linear, curved, circular, polygonal or any other open or closed shape. Base <NUM> has opposing major faces <NUM>, <NUM>' with longitudinally extending flutes <NUM>. Major faces <NUM>, <NUM>' of base <NUM> may be continuous with, and may be at least partially coplanar with, corresponding first faces <NUM>, <NUM>' of collimators <NUM>.

In operation, substantially all light received at light receiving surface <NUM> travels by total internal reflection through collimators <NUM> and base <NUM> before refracting out of light emitting surface <NUM>. Light internally reflects through collimators <NUM> at progressively lower angles. Higher angle light travelling through collimators <NUM> are reflected a greater number of times than lower angle light. Since each reflection bends light a small amount toward a lower angle, higher angle light experiencing more reflections will be bent more toward lower angles than light initially received at lower angles. Thus light reflecting through collimators <NUM> ends up at similar angles below the glare zone as the light refracts out of light emitting surface <NUM>. Some lower angle light may not experience any internal reflections within light guide <NUM>.

Flutes <NUM> on major faces <NUM>, <NUM>' of base <NUM> homogenize light, as described for example in <CIT>. Since flutes <NUM> are contoured in directions (e.g. for <FIG>, into and out of the page) which are perpendicular to the internal reflections by collimators <NUM>, the effect of flutes <NUM> does not significantly interfere with the glare control effect of collimators <NUM>. Texture elements <NUM> at light emitting surface <NUM> further homogenize light exiting light guide <NUM>, as well as homogenizes the appearance of light emitting surface <NUM>.

<FIG> show a light guide <NUM>. Light guide <NUM> extends laterally in a semicircular shape. In an example embodiment, two light guides <NUM> can be combined to form an annulus light guide for an annular luminaire. In some embodiments light guide <NUM> may extend laterally in any other length or shape.

Light guide <NUM> is similar to light guide <NUM> but is an example embodiment configured to emit a wide distribution. In some embodiments the wide distribution may be at least <NUM> degrees. In particular, light receiving surface <NUM> of light guide <NUM> has a plurality of V-shaped grooves <NUM>. The embodiment illustrated in <FIG> has <NUM> V-shaped grooves <NUM>. In other embodiments, light receiving surface <NUM> may have <NUM> or more V-shaped grooves <NUM>. V-shaped grooves <NUM> may span the entirety of light receiving surface <NUM>. V-shaped grooves <NUM> may run normal to the plane of first faces <NUM>, <NUM>' of collimator <NUM>. In other embodiments, V-shaped grooves <NUM> may run parallel to the plane of first faces <NUM>, <NUM>' of collimator <NUM>.

In some embodiments, as shown in Figure 5A, V-shaped grooves <NUM> may be provided with flutes <NUM> running perpendicular to the direction in which V-shaped grooves <NUM> run.

Light guide <NUM> also includes longitudinally extending flutes <NUM> on first faces <NUM>, <NUM>' of collimator <NUM>. Flutes <NUM> of collimators <NUM> may be continuous with corresponding flutes <NUM> of base <NUM>.

Second faces <NUM>, <NUM>' of collimator <NUM> expand laterally in a stepped manner at a plurality of opposing steps <NUM>. Steps <NUM> along each second face <NUM>, <NUM>' may be identical in shape and spaced equally apart. In some embodiments, angle <NUM> may be <NUM> to <NUM> degrees.

The inventors have determined that V-shaped grooves <NUM> split directional light from an light emitting diode (LED) into internally reflected batwing distributions parallel to light guide <NUM>'s lateral extent (e.g. circumference in the case of light guide <NUM>'s particular shape). Light from LEDs comprises various colours (i.e., wavelengths) depending on where it leaves the phosphor face of the LED. In particular, the colour transitions from cool to warm from the center to the edges of the phosphor face of the LED. Different sides of the "V" of V-shaped grooves <NUM> can operate on different areas of the phosphor face. For example, in the illustrated embodiment of a double "V", the two inner sides of the "VV" create a cooler batwing distribution flanked by the two outer sides of the "VV" which create a warmer batwing distribution. The cooler and warmer batwing distributions mix inside light guide <NUM> to homogenize the colours. Flutes <NUM> provide further homogenization of the colours.

The inventors have determined that, since the contours of flutes <NUM> of base <NUM> and flutes <NUM> of collimator <NUM> run perpendicular to the contours of V-shaped grooves <NUM>, flutes <NUM>, <NUM> provide additional homogenization of the optical distribution in a normal direction to V-shaped grooves <NUM>.

The inventors have determined that steps <NUM> of collimators <NUM> provide at least three functions: (i) to divide sections of light guide <NUM> into smaller, thin rectangular sections to eliminate the visual appearance of louver sections on light emitting surface <NUM> created by the imaging of individual collimators <NUM>; (ii) to allow angles of each such section to be independently specified to optimize the optical distribution which runs parallel to light guide <NUM>'s lateral extent; and (iii) to control light rays so that collimators <NUM> turn on and off similar angles through the entire extent of collimators <NUM>, minimizing intermittent "drop outs" along the lateral extent of light guide <NUM>.

<FIG> illustrate exemplary simulated ray traces of light of multiple ray reactions. Rays are shown to internally reflect down to lower angles in the proximal to distal direction. Lower angle rays typically reflect once while higher angle rays are reflected multiple times. Each reflection results in the rays bending to lower angles.

The optical distribution of these reactions is plotted in <FIG>, showing a desirable distribution with peak angles at approximately <NUM> to <NUM> degrees for a wide distribution.

<FIG> show exemplary simulated ray traces of light emitted from light guide <NUM> of a single ray reaction, where the ray enters light guide <NUM> from various angles from <NUM> to <NUM> degrees. From <NUM> to <NUM> degrees (<FIG>), the light ray is refracted at the light receiving surface at inner sides of the "VV" grooves and travels down the light guide until it refracts out of the light emitting surface. From <NUM> to <NUM> degrees (<FIG>), the light ray is refracted at the light receiving surface at outer sides of the "VV" grooves, causing the ray to enter light guide <NUM> at a higher angle. As this angle is higher, the ray internally reflects multiple times within the collimator, reducing its angle, and then refracts out of the light emitting surface.

<FIG> show a light guide <NUM>. Light guide <NUM> is similar to light guide <NUM> but is an example embodiment configured to emit a medium distribution. In some embodiments the medium distribution may be approximately <NUM> to <NUM> degrees.

In particular, light receiving surface <NUM> of light guide <NUM> has a flat surface. The inventors have determined that V-shaped grooves are not necessary for a medium distribution because a medium distribution does not require light to be redirected or spread at the light receiving surface. With a flat surface, light maintains a Lambertian distribution as it enters light receiving surface <NUM>.

Like light guide <NUM>, light guide <NUM> has a plurality of collimators <NUM> with first faces <NUM>, <NUM>', second faces <NUM>, <NUM>', collimator steps <NUM> and collimator flutes <NUM>. In some embodiments, angle <NUM> may be <NUM> to <NUM> degrees. Light guide <NUM> also has a base <NUM> with light emitting surface <NUM> and flutes <NUM>.

The optical distribution of these reactions is plotted in <FIG>, showing a desirable distribution with peak angles at approximately zero to <NUM> degrees for a medium distribution.

<FIG> show exemplary simulated ray traces of light emitted from light guide <NUM> of a single ray reaction, where the ray enters light guide <NUM> from various angles from <NUM> to <NUM> degrees. From <NUM> to <NUM> degrees (<FIG>), the light ray is refracted at the light receiving surface and travels down the light guide until it refracts out of the light emitting surface. From <NUM> to <NUM> degrees (<FIG>), the ray to enter light guide <NUM> at a higher angle such that it internally reflects within the collimator, reducing the angle, and then refracts out of the light emitting surface.

<FIG> show a light guide <NUM>. Light guide <NUM> is similar to light guides <NUM> and <NUM> but is an example embodiment configured to emit a narrow distribution of approximately <NUM> to <NUM> degrees.

Similar to light guide <NUM>, light receiving surface <NUM> of light guide <NUM> has a flat surface instead of V-shaped grooves. To ensure a narrow distribution and maximize collimation, collimator <NUM> lacks the flutes and steps of light guides <NUM> and <NUM>. Also unlike light guides <NUM>, <NUM> and <NUM>, collimators <NUM> are arranged not in a side-by-side immediately adjacent manner but rather a corner edge by corner edge immediately adjacent manner. In some embodiments, angle <NUM> may be <NUM> to <NUM> degrees. Longitudinal corners or edges <NUM> of collimator <NUM> are rounded to reduce distances between diagonal reflections in collimator <NUM>, creating more reflections and more collimation as a result. Major faces <NUM>, <NUM>' of base <NUM> have longitudinally extending flutes <NUM> to increase homogeneity of the exiting light.

The optical distribution of these reactions is plotted in <FIG>, showing a desirable distribution with an approximately zero degree peak angle for a narrow distribution.

<FIG> show exemplary simulated ray traces of light emitted from light guide <NUM> of a single ray reaction, where the ray enters light guide <NUM> from various angles from <NUM> to <NUM> degrees. For <NUM> and <NUM> degrees (<FIG>), the light ray is refracted at the light receiving surface and travels down the light guide until it refracts out of the light emitting surface. From <NUM> to <NUM> degrees (<FIG>), the ray to enter light guide <NUM> at a higher angle such that it internally reflects at least once within the collimator, reducing the angle, and then refracts out of the light emitting surface.

<FIG> shows a narrow aperture luminaire <NUM> according to an embodiment. Luminaire <NUM> has a housing <NUM> that houses a light guide <NUM>. Light guide <NUM> may be any light guide according to the present invention, including for example light guide <NUM>, <NUM>, <NUM> or <NUM>. Housing <NUM> has distal walls <NUM> that may act as baffle to absorb or otherwise block any high angle light leaving the light emitting surface of light guide <NUM>. In example embodiments, aperture <NUM> of housing <NUM> may have a width <NUM> ranging from <NUM> to <NUM>.

Point light sources <NUM> are mounted on board <NUM>. Point light sources <NUM> may be LEDs, and configured for optical communication with the light receiving surface of light guide <NUM>. Board <NUM> has an inner surface <NUM> that may be reflective to collect stray light from a proximal region <NUM> of light guide <NUM> and reflect it back into light guide <NUM>.

Baffle <NUM> is positioned to laterally surround proximal region <NUM> of light guide <NUM>. Baffle <NUM> has an inner surface <NUM> that may absorb stray light from proximal region <NUM>. For example, high angle light that would otherwise result in high angle glare may be blocked by baffle <NUM>. Baffle <NUM> may be configured to conform to the shape of, and when in position contact, the lateral sides of proximal region <NUM> of light guide <NUM>. In other embodiments there may be space between baffle <NUM> and proximal region <NUM>. Baffle <NUM> extends distally a distance <NUM> along proximal region <NUM> of light guide <NUM>. In some embodiments, the ratio of distance <NUM> to width <NUM> of light source <NUM> may range from <NUM>:<NUM> to <NUM>:<NUM>.

<FIG> show an integrally formed baffle board <NUM> shaped to correspond to light guides <NUM>, <NUM> and <NUM>. In other embodiments baffle board <NUM> may be any other shape that corresponds to a corresponding light guide. Baffle portion <NUM> has a plurality of hollow elements <NUM> for surrounding corresponding proximal regions of a plurality of collimators of the light guide. In some embodiments, hollow elements <NUM> may be shaped as hollow rectangular frustums.

Baffle portion <NUM> is made of a dark-coloured (e.g. black) material to absorb stray light from a proximal region of the light guide. Board portion <NUM> has a plurality of apertures <NUM> for mounting corresponding point light sources. Board portion <NUM> is made of a light-coloured (e.g. white) material to reflect stray light back into the light guide.

In some embodiments, such as that illustrated in the embodiments, the baffle may be integrally formed with the board. In other embodiments, the baffle and board may be distinct components.

Claim 1:
A luminaire (<NUM>) comprising:
at least one light guide (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprising:
an elongated base (<NUM>, <NUM>, <NUM>, <NUM>) comprising a light emitting surface (<NUM>) at a distal end, and opposing major faces (<NUM>, <NUM>'); and
a plurality of collimators (<NUM>, <NUM>, <NUM>, <NUM>) arranged in an adjacent manner and projecting in a proximal direction from the base, wherein
each collimator comprises a light receiving surface (<NUM>, <NUM>, <NUM>, <NUM>) at a proximal end, wherein each collimator expands laterally outwardly in a distal direction, and
whereby substantially all light received at the light receiving surfaces internally reflects through the collimators and the base and emits from the light emitting surface;
a plurality of light sources (<NUM>) in optical communication with the light receiving surfaces;
a board (<NUM>) onto which the plurality of light sources are mounted; and
a housing (<NUM>) for housing the light guide, the plurality of light sources, and the board, wherein the housing comprises opposing sidewalls that distally extend beyond a plane defined by the light emitting surface,
characterized in that a first angle (<NUM>) defined by the first faces of the collimators relative to a plane (<NUM>, <NUM>, <NUM>, <NUM>) defined by the light receiving surfaces of the collimators ranges from <NUM> to <NUM> degrees, or from <NUM> to <NUM> degrees, or from <NUM> to <NUM> degrees, and wherein a second angle (<NUM>, <NUM>, <NUM>, <NUM>) defined by the second faces of the collimators relative to a plane defined by the light receiving surfaces of the collimators ranges from <NUM> to <NUM> degrees, wherein the first angle and the second angle are different.