Direct and indirect light diffusing devices and methods

Some embodiments provide a daylighting apparatus comprising an internally reflective tube configured to direct daylight from a first end of the tube to a second end of the tube opposite the first end. A diffuser can be positioned at the second end of the tube. The diffuser can comprise a first optical structure configured such that, when the daylighting apparatus is installed with the first end positioned outside a room and the second end positioned to provide light to the room, a reflected portion of the daylight is directed towards at least one upper region (e.g., a ceiling or upper wall surface) of the room and a transmitted portion of the daylight is directed towards at least one lower region (e.g., a floor surface) of the room.

BACKGROUND

This disclosure relates generally to daylighting systems and methods and more particularly to light diffusing devices and methods.

2. Description of Related Art

Daylighting systems typically include windows, openings, and/or surfaces that provide natural light to the interior of a structure. Examples of daylighting systems include skylight and tubular daylighting device (TDD) installations. In a TDD installation, a transparent cover can be mounted on a roof of a building or in another suitable location. An internally reflective tube can connect the cover to a diffuser mounted in a room or area to be illuminated. The diffuser can be installed in a ceiling of the room or in another suitable location. Natural light entering the cover on the roof can propagate through the tube and reach the diffuser, which disperses the natural light throughout the interior of the structure. Certain currently known devices and methods for diffusing light suffer from various drawbacks.

SUMMARY

Example embodiments described herein have several features, no single one of which is indispensable or solely responsible for their desirable attributes. Without limiting the scope of the claims, some of the advantageous features will now be summarized.

Some embodiments provide a daylighting apparatus comprising an internally reflective tube configured to direct daylight from a first end of the tube to a second end of the tube opposite the first end. A diffuser can be positioned at the second end of the tube. The diffuser can comprise a first optical structure configured such that, when the daylighting apparatus is installed with the first end positioned outside a room and the second end positioned to provide light to the room, a reflected portion of the daylight is directed towards at least one upper region (e.g., a ceiling or upper wall surface) of the room and a transmitted portion of the daylight is directed towards at least one lower region (e.g., a floor surface) of the room.

The first optical structure can comprise a reflective surface shaped and positioned to change the direction of propagation of the reflected portion of the daylight. The reflective surface can comprise at least a first face configured to reflect collimated daylight at a first incident angle. The reflective surface can comprise at least a second face configured to reflect the collimated daylight at a second incident angle different from the first incident angle. The reflective surface can comprise a plurality of additional faces.

The reflective surface can comprise at least a first curved face configured to reflect collimated daylight at a plurality of incident angles. The reflective surface can comprise a lower reflective face region, a middle reflective face region, and an upper reflective face region. Each of the lower reflective face region, the middle reflective face region, and the upper reflective face region can be a conical frustum. The first optical structure can comprise a reflective element with many different shapes, such as the general shape of a frustum of a hyperboloid.

The first optical structure can comprise at least one aperture shaped and positioned to permit at least some of the transmitted portion of the daylight to pass through the first optical structure. The first optical structure can comprise at least one reflective surface interrupted by a plurality of openings configured to permit at least some of the transmitted portion of the daylight to pass through the first optical structure.

The diffuser can comprise a second optical structure configured to receive light exiting the first optical structure. The second optical structure can be configured to spread the reflected portion of the daylight. The second optical structure can also be configured to spread the transmitted portion of the daylight.

Certain embodiments provide a method of providing light inside of a structure. The method can comprise the steps of positioning an internally reflective tube between a first location outside the structure and a second location in a room of the structure in a manner that permits daylight to be directed along the tube from the first location to the second location and positioning a diffuser at an end of the tube in the room such that the diffuser reflects a first substantial portion of the daylight exiting the tube towards at least one upper region (e.g., a ceiling and wall surface) of the room and permits a second substantial portion of the daylight exiting the tube to pass through the diffuser towards at least one lower region (e.g., a floor surface) of the room.

Positioning a diffuser can comprise positioning a first optical element configured to reflect at least some of the daylight and positioning a second optical element around the first optical element. The second optical element can be configured to spread the daylight exiting the tube. Positioning a diffuser at an end of the tube can comprise positioning an optical element such that it extends at least partially into the tube.

Some embodiments provide a method of manufacturing a daylighting device. The method can comprise the steps of disposing a reflective material on each side of a substrate to form at least one sheet having two reflective surfaces; cutting or otherwise forming the sheet to include a plurality of openings in the sheet; shaping the at least one sheet to form an optical element having at least one reflective face region with a generally circular cross-section and an aperture extending through the at least one reflective face region; and placing the optical element at one end of an internally reflective tube. The tube can be configured to receive daylight and to direct the daylight towards the optical element. Shaping the at least one sheet can comprise shaping at least a first sheet and a second sheet and joining the first sheet and the second sheet to form the optical element.

The method can comprise the step of placing a second optical element over the first optical element, the second optical element configured to spread light exiting the tube. The optical element can be configured such that, when the daylighting apparatus is installed with the first end positioned outside a room and the second end positioned to provide light to the room, a reflected portion of the daylight is directed towards at least one ceiling or wall surface of the room and a transmitted portion of the daylight is directed towards at least one floor surface of the room.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In some embodiments, a TDD installation transports sunlight from the roof of a building to the interior via a tube with a reflective surface on the tube interior. A TDD installation can sometimes also be referred to as a “tubular skylight.” A TDD installation can include a transparent cover installed on the roof of a building or in another suitable location. A tube with a reflective surface on the tube interior extends between the cover and a diffuser installed at the base of the tube. The transparent cover can be dome-shaped or can have another suitable shape and can be configured to capture sunlight. In certain embodiments, the cover keeps environmental moisture and other material from entering the tube. The diffuser spreads light from the tube into the room or area in which the diffuser is situated.

The cover can allow exterior light, such as daylight, to enter the system. In some embodiments, the cover includes a light collection system configured to enhance or increase the daylight entering the tube. In certain embodiments, a TDD installation includes a light mixing system. For example, the light mixing system can be positioned in the tube or integrated with the tube and can be configured to transfer light in the direction of the diffuser. The diffuser can be configured to distribute or disperse the light generally throughout a room or area inside the building. Various diffuser designs are possible. An auxiliary lighting system can be installed in a TDD to provide light from the tube to the targeted area when daylight is not available in sufficient quantity to provide a desired level of interior lighting.

The direction of light reflecting through the tube can be affected by various light propagation factors. Light propagation factors include the angle at which the light enters the TDD, which can sometimes be called the “entrance angle.” The entrance angle can be affected by, among other things, the solar elevation, optics in the transparent cover, and the angle of the cover with respect to the ground. Other light propagation factors include the slope of one or more portions of a tube sidewall and the specularity of the sidewall's internal reflective surface. The large number of possible combinations of light propagation factors throughout a single day can result in light exiting the TDD at a wide and continuously varying range of angles.

FIG. 1shows a cutaway view of an example of a TDD10installed in a building16for illuminating, with natural light, an interior room12of the building16. The TDD10includes a transparent cover20mounted on a roof18of the building16that allows natural light to enter a tube24. The cover20can be mounted to the roof18using a flashing. The flashing can include a flange22athat is attached to the roof18, and a curb22bthat rises upwardly from the flange22aand is angled as appropriate for the cant of the roof18to engage and hold the cover20in a generally vertically upright orientation. Other orientations are also possible.

The tube24can be connected to the flashing22and can extend from the roof18through a ceiling14of the interior room12. The tube24can direct light LDthat enters the tube24downwardly to a light diffuser26, which disperses the light in the room12. The interior surface25of the tube24can be reflective. In some embodiments, the tube24has at least a section with substantially parallel sidewalls (e.g., a generally cylindrical surface). Many other tube shapes and configurations are possible. The tube24can be made of metal, fiber, plastic, a rigid material, an alloy, another appropriate material, or a combination of materials. For example, the body the tube24can be constructed from type 1150 alloy aluminum. The shape, position, configuration, and materials of the tube24can be selected to increase or maximize the portion of daylight LDor other types of light entering the tube24that propagates into the room12.

The tube24can terminate at or be functionally coupled to a light diffuser26. The light diffuser26can include one or more devices that spread out or scatter light in a suitable manner across a larger area than would result without the diffuser26or devices thereof. In some embodiments, the diffuser26permits most or substantially all visible light traveling down the tube24to propagate into the room12. The diffuser can include one or more lenses, ground glass, holographic diffusers, other diffusive materials, or a combination of materials. The diffuser26can be connected to the tube24using any suitable connection technique. For example, a seal ring28can be surroundingly engaged with the tube24and connected to the light diffuser26in order to hold the diffuser26onto the end of the tube24. In some embodiments, the diffuser26is located in the same general plane as the ceiling14, generally parallel to the plane of the ceiling, or near the plane of the ceiling14.

In certain embodiments, the diameter of the diffuser26is substantially equal to the diameter of the tube24, slightly greater than the diameter of the tube24, slightly less than the diameter of the tube24, or substantially greater than the diameter of the tube24. The diffuser26can distribute light incident on the diffuser toward a lower surface (e.g., the floor11) below the diffuser and, in some room configurations, toward an upper surface (e.g., at least one wall13or ceiling surface15) of the room12. The diffuser26can spread the light such that, for example, light from a diffuser area of at least about 1 square foot and/or less than or equal to about 4 square feet can be distributed over a floor and/or wall area of at least about 60 square feet and/or less than or equal to about 200 square feet in a typical room configuration.

Diffusers that employ principally direct diffusion, such as downward directing diffusers, distribute light in certain ways that can be undesirable. Some direct diffusers distribute light such that the intensity of light on the floor11when measured on a horizontal plane is highest directly under the diffuser26and decreases with distance away from the location directly under the diffuser26. In some instances, the distribution of light on the floor is characterized by a cosine effect. For example, the intensity of the light can be directly related to the cosine of the incident angle of the light to the floor and inversely related to the distance between the diffuser26and the floor. Accordingly, non-uniform floor light levels are typically observed when certain types of diffusers are used in a TDD10. Further, certain types of direct diffusers are characterized by intense light exiting the diffuser26from ceiling levels less than 15 feet at angles of 45 to 60 degrees (measured from vertical). Intense light at those angles can create visibility problems in an area, including glare and computer screen washout. The contrast of the bright diffuser area and the dark non-illuminated ceiling can also increase the perceived glare and reduce the view of the ceiling area. These are some common undesirable characteristics related to downward directing diffusers.

Diffusers that employ principally indirect diffusion typically distribute light principally to the ceiling and/or walls of an area. Indirect diffusers can also distribute light in ways that are undesirable. For example, indirect diffusers typically distribute a smaller portion of light to the floor11or working areas than direct diffusers. Thus, there may be a substantially dark or dimly-lit area on the floor11directly under the TDD10.

In some embodiments, a diffuser26provides substantial amounts of both direct diffusion and indirect diffusion. In certain embodiments, a diffuser26redirects a portion of the light LDthat exits the tube26at the ceiling level onto a surrounding supper region (e.g., a ceiling surface15) and distributes the remainder to a lower region (e.g., the floor11and walls13). Such a diffuser26can illuminate the floor11more uniformly. Light LDthat is projected onto the painted ceiling surface15and walls13will reflect off of these surfaces13,15in a diffuse, widespread pattern that will mix the light considerably before reaching the floor level11. Allowing a portion or fraction of the light LDto pass directly to the floor11through a diffuser26or light spreading device can mitigate or eliminate the occurrence of a dark area under the TDD10.

In some embodiments, a diffuser26reduces the light intensity in a region greater than or equal to about 45° and/or less than or equal to about 60° azimuthally away from the axis of the tube24by distributing more light LDupward to the ceiling surface15, thereby eliminating or reducing the incidence of glare and display washout. Further, light that passes through the hollow interior of the diffuser26can be directed or controlled such that it has an exit angle of less than about 45° from vertical. When at least the areas of the ceiling surface15near the TDD10or other areas generally in the upper portion of the room12are illuminated, the contrast ratio between the diffuser26and the surrounding ceiling surface15can be reduced, and a brighter overall room appearance can be created.

In the embodiments illustrated inFIGS. 2A-2B, an optical element110is suspended below the level of the ceiling14in order to direct light onto the ceiling surface15. The distance z that the optical element110extends below the ceiling14can be selected such that the optical element110directs adequate light towards the ceiling surface15while not substantially intruding into the available space of the room12. Factors that may affect the selection of the distance z can include ceiling height, other room dimensions, aesthetics, other functional or architectural factors, or a combination of factors. For example, a shorter distance z may be selected when the TDD10is installed in a room12with low ceiling height. In some embodiments, the distance z is less than the height of the diffuser26.

As shown inFIG. 2A, the diffuser26can include a curved optical element110placed directly below and partially inside the base of the tube24. In the example embodiment illustrated inFIG. 2A, the shape of the optical element110can generally conform to a right circular, outwardly concave frusto-hyperbolic section. Many other variations in the shape of the optical element110are possible. In some embodiments, the optical element110is shaped to reflect light incident over the area of the element110at a plurality of incident angles such that light turned by the optical element110is dispersed over a relatively large angular range (for example, at least about 180° or at least about 200°). In certain embodiments, the light incident on the optical element110is substantially collimated while the light exiting the optical element110is substantially distributed throughout the room12in which the TDD10is installed. In some embodiments, the distribution of light exiting the optical element110includes a substantial portion of light dispersed across each of the upper and lower regions (e.g., the ceiling surface15, walls13, and floor11) of the room12.

The optical element110can be constructed from a material system including, for example, metal, plastic, paper, glass, ceramic, a coating, a film, another suitable material, or a combination of materials. In some embodiments, the optical element110includes an aluminum substrate with a reflective coating on each face. The optical element110illustrated inFIG. 2Ahas a reflective, concave outer face116that extends circumferentially about an axis. The outer face116faces away from the axis, while a reflective, convex inner face117opposite the outer face116faces towards the axis, toward the hollow interior of the optical element110. In certain embodiments, the central axis of the optical element110is substantially collinear with a central axis of the tube24.

The surfaces of the outer face116and the inner face117can be made reflective by any suitable technique, including, for example, electroplating, anodizing, coating, or covering the surfaces116,117with a reflective film. Reflective films can be highly reflective in at least the visible spectrum and include metallic films, metalized plastic films, multi-layer reflective films, or any other structure that substantially reflects light in the visible spectrum. The material from which the optical element110is constructed may also be inherently reflective. In some embodiments, at least a portion of the surfaces of the outer face116and the inner face117are generally specular.

A top plane112of the optical element110is generally open so that light traveling down the tube24can pass into the hollow interior of the element110. A bottom plane114of the element110is also generally open such that light propagating through the interior of the element110can exit the element110and enter the room12below in the general direction of the floor11. The aperture of the top plane112and the aperture of the bottom plane114can be substantially circular or any other suitable shape. In some embodiments, one or more of the apertures are the same shape as the shape of a cross-section of the tube24. In certain embodiments, the diameter of the bottom plane114aperture is substantially equal to the diameter of the tube24, slightly greater than the diameter of the tube24, slightly less than the diameter of the tube24, or substantially greater than the diameter of the tube24. The diameter of the top plane112aperture can be smaller than the diameter of the bottom plane114aperture, less than or equal to about half the diameter of the bottom plane114aperture, less than or equal to about 75% of the diameter of the bottom plane114aperture, or another suitable diameter. In some embodiments, the diameter of the top plane112aperture is selected to achieve a desired ratio of direct diffusion to indirect diffusion. For example, if a higher ratio of direct diffusion to indirect diffusion is desired, then the diameter of the aperture of the top plane112can be increased.

In some embodiments, the typical incident angle of substantially collimated light propagating down the tube24and incident on the optical element110depends on whether the light is incident on one of the reflective faces116,117at a position near the top plane112or whether the light is incident at a position near the bottom plane114of the optical element110. In the example illustrated embodiment, the shape of the faces116,117permits the angle of incidence for collimated incoming light to be larger at positions closer to the top plane112and comparatively smaller at positions closer to the bottom plane112of the optical element110. WhileFIG. 2Ashows an optical element110with reflective faces116,117having a particular curvature, it is understood that faces116,117having other curvature or shapes can be used. For example, in some embodiments, the vertical cross-section of the faces116,117(for example, the cross-section shown inFIG. 2A) can have a generally elliptical shape, a generally hyperbolic shape, a generally parabolic shape, a generally negative intrinsic curvature, a generally positive intrinsic curvature, another geometry, or a combination of differently-shaped regions. The shape of the faces116,117can be selected such that a substantial amount of light is directed towards the floor11, wall13, and ceiling surfaces15of the room12when the optical element110is positioned below the tube24in a TDD10installation.

The example diffuser26illustrated inFIG. 2Bincludes an optical element210having a shape generally conforming to a plurality (e.g., three) contiguous right circular frustoconical sections. Many other variations in the shape of the optical element210are possible. The illustrated optical element210has a hollow interior and can be placed below and partially inside the tube24. In some embodiments, the optical element210has a plurality of faces216a-c,217a-coriented at various angles to reflect light incident over the area of the element210at a plurality of incident angles such that light turned by the optical element210is dispersed over a relatively large angular range (for example, at least about 180° or at least about 200°). In certain embodiments, the light incident on the optical element210is substantially collimated while the light exiting the optical element210is substantially distributed throughout the room12in which the TDD10is installed. In some embodiments, the distribution of light exiting the optical element210includes a substantial portion of light dispersed across each of the upper and lower regions (e.g., the ceiling surface15, walls13, and floor11) of the room12.

The optical element210can be constructed from a variety of materials, including the materials discussed with respect to the optical element110described previously. The optical element210illustrated inFIG. 2Bhas a plurality of reflective outer faces216a-cthat extend generally circumferentially about an axis. The outer faces216a-cface away from the axis, while a plurality of reflective inner faces217a-cgenerally opposite the outer faces216a-cface toward the hollow interior of the optical element210. In certain embodiments, the central axis of the optical element210is substantially collinear with a central axis of the tube24.

A top plane212of the optical element210is generally open so that light traveling down the tube24can pass into the hollow interior of the element210. A bottom plane214of the element210is also open such that light propagating through the interior of the element210can exit the element210and enter the room12below in the general direction of the floor11. The shapes and sizes of the top plane212aperture and the bottom plane214aperture can be selected in at least the same ways as the shapes and sizes of the apertures of the optical element110described previously.

In some embodiments, the incident angle of substantially collimated light propagating down the tube24and incident on the optical element210is different when the light is incident on a surface near the top plane212than when the light is incident on a surface near the bottom plane214of the optical element210. In the example illustrated embodiment, the arrangement of the plurality of faces216a-c,217a-cpermits the angle of incidence for collimated incoming light to be larger at the faces216a,217acloser to the top plane212(“top faces”) of the optical element210and comparatively smaller at the faces216c,217ccloser to the bottom plane212(“bottom faces”) of the optical element210. The arrangement of the faces216b,217bbetween the top faces216a,217aand the bottom faces216c,217c(“middle faces”) can permit the incident angle of the collimated light at the middle faces216b,217bto be between the incident angle at the top faces216a,217aand the incident angle at the bottom faces216c,217cin magnitude. While the illustrated embodiment has three regions of reflective faces, it is understood that any number of reflective face regions can be employed, including, for example, one region, two regions, four regions, more than four regions, two or more regions, between two and four regions, and so forth.

The number and configuration of exterior faces116a-cand interior faces117a-ccan be selected such that a substantial amount of light is directed towards the floor11, wall13, and ceiling surfaces15of the room12when the optical element210is positioned below the tube24in a TDD10installation, or such that light is distributed generally uniformly around both upper and lower regions of a room at the same time. For example, in some embodiments light can be distributed by the diffuser26generally continuously across a region extending from a plane generally parallel with the base214of the optical element210to a plane generally perpendicular to the to the diffuser26and generally parallel to the axis of the tube24. In certain embodiments, light can be distributed by the diffuser26generally continuously through an angle sweeping from an upper region of the room12generally adjacent to or near the TDD10to a lower region of the room12generally below the TDD10. For example, the diffuser26can direct portions of incoming daylight upwards, to the left, to the right, and/or downwards.

The optical element210can include transition regions218a-bdisposed between reflective faces having differing geometry. For example, a first transition region218acan be disposed between the top faces216a,217aand the middle faces216b,217b, and a second transition region218bcan be disposed between the middle faces216b,217band the bottom faces216c,217c. In some embodiments, the number of transition regions218a-bis equal to one less than the number of reflective face regions having differing geometry. For example, the example embodiment illustrated inFIG. 2Bhas three frustoconical face regions having different slant angles and two transition regions218a-b. The transition regions218a-bcan include creases, rounded corners, or other transitional elements between reflective face regions. In some embodiments, the transition regions218a-bform a sharp transition between reflective face regions. Alternatively, the transition regions218a-bcan form a more gradual transition between reflective face regions.

The optical element210can control and distribute light exiting the tube24according to various optical element design properties and their associated principles. In the example embodiment illustrated inFIG. 3, the reflective surfaces216a-c,217a-cof the optical element210are designed to accommodate a specific range of angles of light to maintain a constant, a nearly constant, or a substantially evened illumination on the ceiling surfaces15and walls (not shown) of the room12. Light reflects down the tube24at the same elevation angle from horizontal at which the light entered the tube24. Therefore, for most inhabited locations on the planet, in many embodiments, the elevation angle from horizontal of light entering the tube24will range from about 20 to 70 degrees. The elevation angle depends on the sun angle, which varies throughout the course of a day and also throughout the course of a year.

The propagation of light through the tube24and the interaction of light with the optical element210vary with the elevation angle of the light. For example, in some embodiments, light A entering at lower sun angles will reflect once off a sloped surface216bof the optical element210, as shown inFIG. 3. In certain such embodiments, light B entering the tube24at higher sun angles will reflect multiple times off surfaces216a,216cof the optical element210. Accordingly, both the low-angle light A and the high-angle light B are directed towards the ceiling surface15at exit angles that are considerably closer than the elevation angles of the light when it entered the tube24. By reflecting light differently depending on the elevation angle of the light, the optical element210can provide similar exit angles and illumination on the ceiling surface15and walls of the room12for high elevation angle light and low elevation angle light.

The top plane212of the optical element210can be open, substantially open, or at least partially open to allow light C to transmit down to the area below the tube24(for example, towards the floor of the room12). In the example embodiment illustrated inFIG. 4, light C passes through the top plane212and reflects off an interior face217aof the optical element210. The interior face217aturns the light C such that the exit angle of the light C from the TDD10is closer to vertical than the entrance angle of the light C. In some embodiments, the optical element210increases the elevation angle from horizontal of at least a portion of the light propagating through the interior of the optical element210such that the at least a portion of the light exits the TDD10at a more vertical angle, as illustrated. The degree to which the light C is turned can depend on the orientation and position of the portion of the interior face217on which the light C is incident.

In certain embodiments, the optical element210is designed to ensure that light passing through the optical element210will exit the bottom plane214of the optical element210at an exit angle of less than about 45 degrees from vertical or at a nearly vertical orientation in order to reduce or prevent the light C from exiting the TDD10at a 45 to 60 degree angle from vertical. In this manner, the optical element210can reduce or eliminate the glare and visibility issues that light exiting a fixture at those angles can cause.

In the example embodiment illustrated inFIGS. 5 and 8, an optical element310is shown that can resemble the optical elements110,210described previously in many ways, but differs in manners such as those discussed hereafter. The optical element310has exterior faces316a-cand interior faces317a-cthat are at least partially reflective and at least partially transmissive. In some embodiments, the optical element310is constructed from a material332that is perforated, cut, molded, or otherwise constructed such that the material is interrupted by a plurality of openings334that extend through the material. The openings334can be sized and positioned in order to allow a substantial amount of light D2to transmit downward and a substantial amount of light D1to be reflected towards the ceiling surfaces15or walls of the room12. Incident light D is turned when it is incident on the reflective material332but transmits through the openings334. In some embodiments, the openings334are generally evenly distributed over the surface of the optical element310. Alternatively, the openings334can be distributed according to a pattern that is configured to produce any desired effect.

In some embodiments, the openings334,434are not true physical openings, but merely optical openings formed of translucent or transparent material surrounded by or adjacent to opaque or reflective material. Other structures or configurations can also be used to permit a portion of the light to be directed generally perpendicularly to the diffuser26and a portion of the light to be directed generally in the direction of the periphery of the diffuser26.

In certain embodiments, the openings334are configured such that the total area encompassed by the openings is about 50% of the surface area of the optical element310. Alternatively, the openings can be configured such that the openings334cover less than or equal to about 60% of the surface, more than or equal to about 40% of the surface, or another portion that can be selected to give the optical element310any desired optical characteristics. By adjusting the size and arrangements of openings334in the optical element310, a TDD manufacturer can tailor the reflection and transmission characteristics of the optical element310to account for the relative amount of illumination needed on the ceiling surface15, walls, and/or floor of the room12. In certain embodiments, the illumination on the ceiling surface15, walls, and/or floor of the room12emanating from a TDD installation can be adjusted without increasing or decreasing the size of the tube.

One or more optical elements in addition to the optical elements210,310described above can be used to further control the distribution of light as it exits the TDD10. In the example embodiment illustrated inFIGS. 6,8and9, a second optical element410is disposed between the optical element210and the room12. The second optical element410is a light diffusing structure configured to interact with light E, F reflected by and/or light G passing through the optical element210. In the embodiment illustrated inFIG. 6, light E propagating along a first path reflects off the interior surface25of the tube24and is incident on the optical element210at a middle exterior face216b. The middle exterior face216breflects and turns the light E toward the ceiling surface15. The light E propagates to the second optical element410, which spreads the light. Light E1exiting the second optical element410is spread in a diffused pattern generally toward the ceiling surfaces15and walls13of the room12. Light F propagating along a second path is incident on the optical element at an upper exterior face216a. The upper exterior face216areflects and turns the light F toward a lower exterior face216cof the optical element210. The lower exterior face216creflects and turns the light F generally toward the ceiling surface15. The light F propagates to the second optical element410, which spreads the light. Light F1exiting the second optical element410is spread in a diffused pattern generally toward the ceiling surfaces15and walls13of the room12. Light G propagating along a third path reflects off the interior surface25of the tube24and passes through the optical element210. The light G propagates to the second optical element410, which spreads the light. Light G1exiting the second optical element410is spread in a diffused pattern generally toward the floor11of the room12.

Many variations in the shape, position, and construction of the second optical element410are possible. The second optical element410can include a first diffusing surface420extending from the ceiling14to the base of the optical element210. A second diffusing surface426can refract light exiting the base214of the optical element210. The diffusing surfaces420,426can be made from any suitable material such as, for example, transparent plastic, translucent plastic, glass, one or more lenses, ground glass, holographic diffusers, another diffusing material, or a combination of materials.

In some embodiments, at least one of the diffusing surfaces420,426comprises a substantially continuous diffusing material432, a diffusing material432interspersed with openings434, another material, or a combination of materials. The second optical element410can reduce the contrast between the TDD10and the ceiling surfaces15and/or walls13surrounding the TDD10by further diffusing light E1, F1, G1exiting the TDD10. In certain embodiments, the first optical element210turns at least a portion of incident light E, F using a shaped reflective surface while the second optical element410spreads incident light E, F, G using refraction or photon diffusion. In some embodiments, the diffusing surfaces420,426are held in place or supported by supporting structures. The supporting structures can be constructed from any suitable material and can include rings424,426, rods428, other structural elements, or a combination of elements.

Example dimensions and proportions of the TDD will now be discussed with reference to the embodiment shown inFIG. 7. In some embodiments, the design of the TDD10is compact. For example, the width or diameter W2(width dimension) of the base214of the optical element210may be approximately equal to the width dimension W1of the tube24. In some embodiments, the width dimension W2of the base214is less than or equal to the sum of the width dimension W1of the tube24and a relative short distance (e.g., about one inch). In an example embodiment, the diameter W2of the base214is 21.25″ when the diameter W1of the tube24is 21″. Other suitable tube24and optical element210dimensions can be selected as appropriate to provide desired lighting and diffusion characteristics to the room12.

In certain embodiments, the optical element210extends a short distance L2from the ceiling14into the room12. For example, the distance L2between the ceiling14and the base214of the optical element210can be at least about six inches and/or less than or equal to about twelve inches, less than or equal to about twelve inches, or less than or equal to about nine inches. In some embodiments, the optical element210extends at least partially into the tube24. For example, if the height L1of the optical element210is 8.85″ and the distance L2between the base214of the optical element210and the ceiling14is 6.5″, then the optical element210will extend 2.35″ into the tube. By positioning the optical element210at least partially into the tube24, the distance between the base214of the optical element210and the ceiling14can be decreased.

At least some of the embodiments disclosed herein may provide one or more advantages over existing daylighting systems. For example, certain embodiments effectively allow a TDD to distribute light exiting the TDD onto the upper and lower regions of a room (e.g., the ceiling, walls, and/or floor). As another example, some embodiments provide techniques for allowing substantially light transmission directly beneath a TDD and to the sides of the TDD. As another example, certain embodiments provide an indirect diffuser that also allows a portion of incident light to transmit directly through the diffuser. As another example, some embodiments provide an indirect diffuser that provides substantial illumination directly below the diffuser and has reduced contrast between the base of the diffuser and an illuminated ceiling.

Discussion of the various embodiments disclosed herein has generally followed the embodiments illustrated in the figures. However, it is contemplated that the particular features, structures, or characteristics of any embodiments discussed herein may be combined in any suitable manner in one or more separate embodiments not expressly illustrated or described. For example, it is understood that a diffuser can include multiple optical elements, reflective surfaces, and/or diffusing surfaces. In many cases, structures that are described or illustrated as unitary or contiguous can be separated while still performing the function(s) of the unitary structure. In many instances, structures that are described or illustrated as separate can be joined or combined while still performing the function(s) of the separated structures. It is further understood that the diffusers disclosed herein may be used in at least some daylighting systems and/or other lighting installations besides TDDs.