Abstract:
The present application generally relates to techniques and equipment for color correction of natural daylight. More particularly, the present application relates to color correction of daylight entering the interior of a structure to maintain a substantially constant color temperature over a period of time through deployment of an opto-luminescent material in a daylighting device. The color correction through deployment of an opto-luminescent material and/or color filter in a daylighting device preferably maintains high lumen intensity.

Description:
TECHNICAL FIELD 
       [0001]    The present subject matter generally relates to techniques and equipment for color correction of natural daylight. More particularly, the present application relates to color correction of daylight entering the interior of a structure having a daylighting device to maintain a substantially constant color temperature over a period of time through deployment of an opto-luminescent material. 
       BACKGROUND 
       [0002]    Conventional windows and skylights are inserted into walls or roofs of buildings to introduce natural light into the interior of a building to offset the need for artificial light. Existing windows and skylights allow for outside natural light to penetrate to the inside of a building during daylight hours. The color temperature of natural light penetrating through a window or skylight changes over the course of a day, season or due to changes in weather conditions (overcast vs. cloudless sky). Existing windows and skylights, however, do not have the ability to change a color temperature of the natural light entering the interior of a building to a more desired color temperature. 
         [0003]    As shown in  FIG. 1 , a typical building  10  includes a roof  11  exposed to the exterior of the building  10 . A ceiling  12  and a room  13  are present within the interior of the building  10 . A skylight  15  is positioned in the roof  11  and extends through the building  10  and ceiling  12  to the interior of room  13 . The exterior entrance  15 ′ of the skylight  15  is positioned to receive natural daylight  17  and pass the natural light to the interior of room  13  and thereby supply illumination  15 ″ the interior of room  13 . Similarly, a window  14  is positioned on a side of building  10  for passing natural light to the interior of room  13 . Structures of skylights are know. For example, the skylight can be substantially flush with the roofline with a vaulted ceiling. Other skylights extend downward into a room having a drop down ceiling and include a reflective surface to carry light into the room. These are but a few examples of conventional skylight structures. 
         [0004]    Consumers typically prefer the daylight of the morning or late afternoon hours, due to the presence of a “warmer” red coloration. A desirable color temperature during a time period in the morning or late afternoon hours is in the range of about 3,000 to 3,500° K depending on local weather conditions. Over the course of the day, the color temperature increases to around 5,600° K at midday depending on local weather conditions. This midday light is characterized as “cooler” light (despite actually having a higher color temperature than morning light) due to the presence of more blue and green colors present in the light. Thus, the higher color temperature of midday light is less preferred by consumers than the lower color temperature of morning light (e.g., near sunrise) or later afternoon (e.g., near sunset). 
         [0005]    Hence a need exists for techniques and equipment for color correction of day light that maintains a substantially constant color temperature over a period of time such as the course of a day or season or due to changes in weather conditions, and preferably maintains high lumen intensity at the same time. 
       SUMMARY 
       [0006]    The teachings herein alleviate one or more of the above noted problems of the prior art with improved daylighting devices. 
         [0007]    An exemplary daylighting device includes a passive optical element, that is at least substantially transmissive with respect to daylight. The passive optical element is configured to receive daylight from outside a structure and allow passage of light to an interior of the structure. An opto-luminescent material is associated with the passive optical element. The opto-luminescent material has excitation and emission spectra so as to convert a first portion of daylight in a first spectral region to light in a second spectral region. At least some of the light in the second spectral region produced by excitation of the opto-luminescent material is emitted into the interior of the structure in combination together with a second portion of daylight through the passive optical element. 
         [0008]    In other examples, a daylighting method is provided. The method includes receiving daylight from outside a structure, for transmission through a passive optical element that is at least substantially transmissive and color neutral with respect to daylight toward an interior of the structure. An opto-luminescent material is excited with a first portion of the received light in a first spectral region to convert the first portion of the light into light in a second spectral region. A combination of at least some of the light is supplied in the second spectral region produced by the excitation of the opto-luminescent material and a second portion of the received light, through the passive optical element, into the interior of the structure. The opto-luminescent material is of a type such that the light conversion and combination results in a reduced variation in color characteristic of light supplied through the device into the interior of the structure due to conditions or variations over time in the color characteristic of the daylight. 
         [0009]    In yet another example, a system which includes a daylighting device is provided. The daylighting device includes an optical collector for receiving daylight from outside a structure. An optical emitter element is configured to allow passage of light to an interior of the structure. An optical channel is coupled to and configured to carry light from the optical collector to the optical emitter element. An opto-luminescent material is in or coupled to the daylighting device. The opto-luminescent material has excitation and emission spectra so as to convert a first portion of daylight received by the system in a first spectral region to light in a second spectral region. The opto-luminescent material is positioned so that at least some of the light in the second spectral region produced by excitation of the opto-luminescent material is emitted into the interior of the structure in combination together with a second portion of the received daylight. 
         [0010]    In yet other examples, a color filter is present in conjunction with or, as an alternative to, the opto-luminescent material in the daylighting devices and systems described herein. 
         [0011]    Additional advantages and novel features will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by production or operation of the examples. The advantages of the present teachings may be realized and attained by practice or use of various aspects of the methodologies, instrumentalities and combinations set forth in the detailed examples discussed below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The drawing figures depict one or more implementations in accord with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements. 
           [0013]      FIG. 1  shows an illustration of a building with a conventional skylight and window. 
           [0014]      FIG. 2  shows an example of a daylighting device in a roof of a structure. 
           [0015]      FIG. 3A  shows an example of a daylighting device in a side of a structure. 
           [0016]      FIG. 3B  shows an example of a daylighting device in a roof of a structure. 
           [0017]      FIGS. 4A-4B  show examples using a tunnel-shaped daylighting device. 
           [0018]      FIG. 5  shows another example using a tunnel-shaped daylighting device 
           [0019]      FIGS. 6A and 6B  depict an example of a tunnel-shaped daylighting device in morning and afternoon natural light, respectively. 
           [0020]      FIGS. 7A and 7B  illustrate an example of a daylighting device in morning and afternoon natural light, respectively. 
           [0021]      FIG. 8  is a view of another example of a daylighting device in a roof of a structure. 
           [0022]      FIGS. 9A and 9B  represent an example of a material containing an opto-luminescent material. 
           [0023]      FIG. 10  shows another example of a daylighting device using fiber optics. 
           [0024]      FIGS. 11 and 12  are more detailed views of the daylighting device of  FIG. 10 . 
           [0025]      FIG. 13A-13C  show data from several tests of different opto-luminescent materials during different times of the day. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant teachings. However, it should be apparent to those skilled in the art that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings. 
         [0027]    Reference now is made in detail to the examples illustrated in the accompanying drawings and discussed below.  FIG. 2  illustrates an example of a daylighting device  25  positioned within a roof  21  (pitched or flat roof) of a structure  20  and extending through the ceiling  22  of the structure  20  and into interior room  23 . The daylighting device in  FIG. 2  can be one of any number of skylights in the structure  20 . 
         [0028]    The structure depicted in one or more of the examples includes a building. It should be understood that a building can be a commercial, agricultural (e.g., green house or a farming structure) or a residential structure. The structure can also include a motorized vehicle such as a boat, ship, recreational vehicle (RV), etc. For daylighting devices used for agricultural purposes, it may be desirable to color correct the daylight into a color light that is a preferred color for growing vegetation or crops or stimulating the production of milk in dairy cows. 
         [0029]    An exterior surface  25 ′ of the daylighting device  25  serves as the entrance to the light entering the daylighting device  25 . The exterior surface  25 ′ receives daylight  27  from outside the structure  20 , and the device  25  is configured to allow passage of light to the interior of structure  20  and provides illumination  25 ″ to interior room  23 . The daylighting device  25  is a passive optical system that is at least substantially transmissive and color neutral with respect to daylight received from outside the building for processing in and/or transport to the room  23  inside the building. For example, the optical element of the device  25  forming the surface  25 ′ and/or the optical element forming the light exist from the device  25  into the room  23  are relatively transparent, at least in this example. As a result, these elements and the overall device  25  would normally produce little or no color shift of light received by and passing through the device  25 . 
         [0030]    To this point in our discussion, the device  25  of this first example is fairly similar to the skylight  15  in  FIG. 1 . The daylighting device  25 , however, further includes a structure  28  that bears an opto-luminescent material  26  associated with the exterior surface  25 ′. The opto-luminescent material  26  has excitation and emission spectra so as to convert a first portion of light  27  through the exterior surface in a first spectral region to light in a second spectral region. The structure  28  is configured so that at least some of the light in the second spectral region produced by excitation of the opto-luminescent material  26  is emitted into the interior of the building in combination together with a second portion of the light passing  27  which passes through the exterior surface  25 ′ and the rest of the device  25 . 
         [0031]    In certain examples, the opto-luminescent material  26  that is present in the daylighting devices described herein is of a type such that the light conversion and combination results in a reduced variation in color characteristic of light supplied through the device into the interior of the building due to conditions (i.e. outside weather conditions) or variations over time in the color characteristic of the daylight. The opto-luminescent material is preferably colorless when it is in its non-excited/non-pumped state. 
         [0032]    In certain examples, the opto-luminescent phosphor is present such that afternoon light in a color temperature range of about 5,000 to 5,600° K is converted down to a more desirable temperature, e.g., in the 3,000 to 3,500° K range similar to a color temperature of a morning light near sunrise or late afternoon light near sunset. Again, depending on the desired range of color temperature, the phosphor(s) used in the daylighting devices described herein can be selected and mixed (if more than one phosphor is used) to achieve any desired color temperature. Several of the examples described herein convert the cooler blue and green light of the afternoon light into a warmer red coloration which is more typical of morning light. Again, any desired color temperature can be achieved with the present examples. 
         [0033]    An example of an opto-luminescent material for one or more of the daylighting systems and devices described herein is one or more phosphor materials. An opto-luminescent “phosphor,” as used in this and several other examples, may be any of a variety of optically excited luminescent materials. Phosphorescent, biophosphorescent or bioluminescent materials can also be used as opto-luminescent materials. Terms relating to opto-luminescent phosphor are intended to encompass a broad range of materials excited by optical energy of a first or ‘excitation’ region/band that re-generate light in a different second or ‘emission’ region/band that is at least somewhat different from the excitation band/region. Examples of phosphors that may be used in various applications discussed herein include a variety of conventional phosphors. Traditional phosphors such as rare-earth phosphors may be used. Recently developed quantum dot (Q-dot) phosphors or doped quantum dot (D-dot) phosphors may also be used. 
         [0034]    Phosphors absorb excitation energy then re-emit the energy as radiation of a different wavelength than the initial excitation energy. For example, some phosphors produce a down-conversion referred to as a “Stokes shift,” in which the emitted radiation has less quantum energy and thus a longer wavelength. Other phosphors produce an up-conversion or “Anti-Stokes shift,” in which the emitted radiation has greater quantum energy and thus a shorter wavelength. 
         [0035]    Quantum dots (Q-dots) provide similar shifts in wavelengths of light. Quantum dots are nano scale semiconductor particles, typically crystalline in nature, which absorb light of one wavelength and re-emit light at a different wavelength, much like conventional phosphors. However, unlike conventional phosphors, optical properties of the quantum dots can be more easily tailored, for example, as a function of the size of the dots. In this way, for example, it is possible to adjust the absorption spectrum and/or the emission spectrum of the quantum dots by controlling crystal formation during the manufacturing process so as to change the size of the quantum dots. Thus, quantum dots of the same material, but with different sizes, can absorb and/or emit light of different colors. For at least some exemplary quantum dot materials, the larger the dots, the redder the spectrum of re-emitted light; whereas smaller dots produce a bluer spectrum of re-emitted light. 
         [0036]    Doped quantum dot (D-dot) phosphors are similar to quantum dots but are also doped in a manner similar to doping of a semiconductor. Also, Colloidal Q-Dots are commercially available from NN Labs, LLC of Fayetteville, Ark. and are based upon cadmium selenide. Doped Q-dots are commercially available from NN Labs of Fayetteville, Ark. and are based upon manganese or copper-doped zinc selenide. Other commercially available phosphors that can be formed into a sheet are available from Intematix of Fremont, Calif. EMD Chemicals, of Gibbstown, N.J., manufactures powder phosphors that can be used in one or more examples described herein. 
         [0037]    As shown in  FIGS. 13A-13C , specific opto-luminescent phosphor materials were applied to a transparent material such as glass or plastic. A control glass or clear glass containing no opto-luminescent material was also tested. In particular, a rare earth phosphor (available from Intematix) and a nano-phosphor (available from NN Labs, LLC) were applied as to either a transparent plastic or glass sample. The rare earth phosphor was applied as a film to a transparent plastic sample. The nano-phosphor was combined with a binder and positioned between two glass plates.  FIG. 13A  represents a first test performed at 1:00 pm;  FIG. 13B  represents a second test performed at 2:00 pm; and  FIG. 13C  represents a third test performed at 4:00 pm. Tables 1-3 below represent data test results for the three tests performed at 1, 2 and 4:00 pm, respectively. Values for Correlated Color Temperature (CCT), Duv (the closest distance from the Plankian locus (the black body locus)), Color Rendering Index average (CRI Ra), and red rendering index (R9) for measuring a red balance were each measured. The spectral intensity was normalized to 550 nm for the testing. Visible light in the range of 400-700 nanometers is represented in  FIGS. 13A-13C . 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Test 1 
               
             
          
           
               
                   
                   
                 Rare 
                   
               
               
                   
                 Clear 
                 Earth 
                 Nano- 
               
               
                   
                 Glass 1 
                 Phosphor 1 
                 Phosphor 1 
               
               
                   
                   
               
             
          
           
               
                   
                 CCT: 
                 4583 
                 2756 
                 3962 
               
               
                   
                 Duv: 
                 0 
                 0.004 
                 0.002 
               
               
                   
                 CRI Ra: 
                 96 
                 92 
                 96 
               
               
                   
                 R9: 
                 91 
                 62 
                 97 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Test 2 
               
             
          
           
               
                   
                   
                 Rare 
                   
               
               
                   
                 Clear 
                 Earth 
                 Nano- 
               
               
                   
                 Glass 2 
                 Phosphor 2 
                 Phosphor 2 
               
               
                   
                   
               
             
          
           
               
                   
                 CCT: 
                 4832 
                 2826 
                 4143 
               
               
                   
                 Duv: 
                 −0.002 
                 0.001 
                 0 
               
               
                   
                 CRI Ra: 
                 95 
                 93 
                 95 
               
               
                   
                 R9: 
                 84 
                 68 
                 96 
               
               
                   
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Test 3 
               
             
          
           
               
                   
                   
                 Rare 
                   
               
               
                   
                 Clear 
                 Earth 
                 Nano- 
               
               
                   
                 Glass 3 
                 Phosphor 3 
                 Phosphor 3 
               
               
                   
                   
               
             
          
           
               
                   
                 CCT: 
                 4728 
                 2756 
                 3860 
               
               
                   
                 Duv: 
                 −0.004 
                 0.004 
                 −0.004 
               
               
                   
                 CRI Ra: 
                 93 
                 92 
                 93 
               
               
                   
                 R9: 
                 76 
                 62 
                 89 
               
               
                   
                   
               
             
          
         
       
     
         [0038]    The test data in the spectral charts of  FIGS. 13A-13C  reveal that both the rare earth and nano-phosphors are an effective way of changing the color temperature of daylight. In particular, both phosphors were able to convert some of the blue light (wavelength of about 475) content into a warmer red (about 650 nm) or orange (about 590 nm) throughout the afternoon. Although the clear glass control likely absorbed some blue light, this fact does not change the conclusions that opto-luminescent materials such as phosphors are an effective way of changing the color temperature of natural light entering a daylighting device for illumination of interior spaces in a structure such as a building. In the experiment, clear glass absorbed some of the blue light and changed some of the control quantities such as CCT. 
         [0039]    The opto-luminescent phosphor material is preferably colorless when it is in its non-excited state. In one example, the phosphor used in the daylighting device will be in a substantially non-excited state during the morning hours near sunrise or later afternoon hours near sunset when the content of the outside light has a “warmer” red coloration. As the day passes on, the red light that remains in the light will continue to pass through without exciting the phosphor, but the blue and green light that becomes more prevalent in the afternoon light will be converted into a more acceptable color temperature by the opto-luminescent phosphor. Similarly, conditions such as cloud cover (overcast conditions) will effect the amount of blue green light in the daylight and will need color correction accordingly. 
         [0040]    D-dots are examples of opto-luminescent phosphors that tend to be colorless when they are not in an excited state. When used in the daylighting device, D-dots mat be used that are primarily excited with ultraviolet (UV) or near UV light. Thus, outdoor light that enters the daylighting device contains UV and near UV light (including purple and blue hues) will pump or excite the D-dots so as to convert some of the UV and near UV light into a visible light of a more acceptable color temperature such as a reddish orange. The D-dots therefore will down convert the UV and near UV light into a more acceptable color temperature of visible light that illuminates the interior of the room. D-Dots may increase the apparent light throughput of the daylighting device by converting the UV light into light of a visible range. The D-dots will not interfere with other light in the visible range, which therefore and will pass through the daylighting device into the interior of the room. Similarly, other phosphors can be used to convert some infrared light into light in the visible spectrum with a more desirable color temperature. 
         [0041]    Opto-luminescent materials can be deployed in or around the daylighting device in a myriad of ways. Turning back to the example in  FIG. 2 , the opto-luminescent material  26  can be included in or on a film or sheet to form opto-luminescent structure  28 . The example of the daylighting device can be, for example, a conventional skylight structure as discussed above for  FIG. 1 . The film/sheet opto-luminescent structure  28  containing the opto-luminescent material  26  can be positioned inside the daylighting device between the roof  21  and ceiling  22  and except for the phosphor is transparent or translucent to daylight. Commercially available phosphors that can be formed into a sheet are available from Intematix of Fremont, Calif. The opto-luminescent structure could alternatively be a plate of transparent glass or acrylic coated with a phosphor(s). For example, a phosphor(s) powder can be electrostatically deposited on the glass or acrylic/plastic plate. Other techniques include doping the phosphor into a transparent substrate or applying a phosphor containing paint or powder coat on a transparent substrate. 
         [0042]    The position of the opto-luminescent structure  28  can be at other locations within the daylighting device  25 . For instance, if the film or sheet containing the opto-luminescent material is colorless, it can be positioned at the entrance  25 ′of the daylighting device or at the light exit of the device  25  into the room  23 . If however, the sheet or film has an orange coloration, as is common with some types of phosphors, it may be preferable to locate the opto-luminescent structure  28  within the daylighting device  25  at a less visible position due to aesthetic reasoning and/or local zoning regulations. 
         [0043]    In certain examples, a color filter  25 ′″ ( FIG. 2 ) can be used in conjunction with, or as an alternative to, the opto-luminescent material. Color filters are commercially available and are configured to filter, reflect or absorb light by wavelength range. For example, color absorption filters are made from colored filter glass or synthetic gels. If included, an optical grade filter having a uniform density and color over the surface of the filter is preferably used. Also, the thicker the material of the filter, the more wavelengths it will absorb. By absorbing certain wavelengths, only certain parts of the visible spectrum can be seen. If for example a filter that is meant to absorb all other wavelengths except yellow is used, only yellow light will come through and be seen inside the room  23 . Further, if it is desirable to remove a particular color(s) from the natural light entering the daylighting device, the color filter can be added to filter out such unwanted light and allow the remaining wavelengths of light to pass through. If a red colored filter is used, for example, unwanted blue or green colors can be filtered out of the light. In the examples of  FIGS. 2-10 , a color filter can be used in conjunction with the opto-luminescent material or as an alternative to the opto-luminescent material. As discuss in further detail below, the micro-louver material  78  in  FIGS. 7A ,  7 B, could include the color filter material without the opto-luminescent material present. For reflective filters, these type filters can be used to reflect UV and/or blue and green light back into the opto-luminescent material for further color correction. 
         [0044]    Returning again to the example in  FIG. 2 , the inner surfaces  29  of the daylighting device  25  may be reflective, e.g. specular, quasi-specular or diffusely reflective, to minimize loss of light due to absorption or back out of the entrance  25 ′ of the daylighting device  25 . The inner surfaces  29 , for example, can include a specular mirror surface such as mirrored silver. The mirrored surface will reflect the light and act as an optical channel to direct the received light through towards the interior room  23 . The daylighting device can optionally include a collector  25 ′ for enhancing collection of light  27 . The collector  25 ′″ can be flat or shaped. The collector illustrated in the example of  FIG. 2  is a dome shaped structure. 
         [0045]    In the example shown in  FIG. 3A , the window  34  includes a window dressing such as a shade  35  containing an opto-luminescent material. The opto-luminescent material can include one or more of the phosphors described above. The shade could be a transparent or semitransparent fabric with a phosphor coating on or embedded in the fabric; or the fabric can be stained with an opto-luminescent dye(s). Any conventional window dressing (blind, curtain, etc.) coated with one or more opto-luminescent materials is contemplated. As with the example in  FIG. 1 , the shade  35  will perform in substantially the same manner and, for example, down convert at least some of the bluish early afternoon light  37  entering window  34  into a warmer reddish light to illuminate interior room  33 . The roof  31  and ceiling  32  are depicted for reference points in building  30 . 
         [0046]    Alternatively, the daylighting device  35 ′ can be a roof  31 ′ for a sun-room  30 ′, as shown in  FIG. 3B . The roof  31 ′ for sun-room  30 ′ could essentially comprise a plurality of connected windows  34 ′ serving as a roof  31 ′ for the sunroom  30 ′, wherein each window  34 ′of the roof  32 ′ of the sun-room  30 ′ has an opto-luminescent material  36 ′ coated, impregnated or doped into each window  34 ′, or present in a film or sheet adjacent to or in contact with each window  34 ′comprising the sun-room roof  31 ′. As with the previous examples, the daylighting device  35 ′ containing the opto-luminescent material  36 ′ will perform in substantially the same manner and, for example, down convert at least some of the bluish early afternoon light  37 ′ entering at entrance  35 ″ of each window  34 ′ into a warmer reddish light to illuminate interior room  33 ′. 
         [0047]    Turning now to  FIG. 4A , an example of a building  40  containing another daylighting device  45  is depicted. In the example of  FIG. 4A , the daylighting device  45  is positioned between the roof  41  and the ceiling  42 . The entrance  45 ′ of the daylighting device  45  is positioned on a side of the building  40 . The daylighting device  45  in the example extends horizontally from the side of the building to a desired position in the ceiling  42 . Somewhat different or angled orientation of the device may be used. The tunnel shaped daylighting device  45  allows light  47  to enter the daylighting device and follow the path of the directional arrow into interior room  43 . The inner surfaces  49  of the daylighting device  45  may be reflective, e.g. specular, quasi-specular or diffusely reflective, to minimize losses as outlined earlier. The daylighting device  45  in this example includes prism or mirror members  45   a ′″ and  45   b ′″ at or near the interior end of the light channel formed within the device  45 . The daylighting device  45  allows for the light entering the daylighting device  45  to travel along a direction between the roof and ceiling until it reaches the prism or mirror members  45   a ′″ and  45   b ′″, which alter the direction of the light and direct it into the room  43  to illuminate  45 ″ the interior of room  43 . Such prism or mirror designed daylighting devices are commercially available and can often referred to as a “solar pipe”, “light pipe”, “light tube” or “tubular skylight.” These prism or mirror designed daylighting devices are designed to bring natural daylight and illumination horizontally into a building with a deep floor plan. 
         [0048]    The opto-luminescent material  46  performs in substantially the same manner as in the example in  FIG. 2 . The daylighting device  45  includes an opto-luminescent structure  48  for bearing an opto-luminescent material  46  associated with the exterior surface  45 ′. The opto-luminescent material  46  has excitation and emission spectra so as to convert a first portion of light  47  in a first spectral region to light in a second spectral region. Thus, at least some of the light transported to the left of the depicted opto-luminescent structure  48  will contain light in a second spectral region. The opto-luminescent structure  48  is configured so that at least some of the light in the second spectral region produced by excitation of the opto-luminescent material  46  is emitted into the interior of the building  40  in combination together with a second portion of the light (i.e., non-excited light) passing through the exterior surface entrance  45 ′. 
         [0049]    The window  44  in  FIG. 4A , can optionally include a window dressing (not shown) having an opto-luminescent material as discussed in the example of  FIG. 3A  and/or the opto-luminescent material  46  can be included in the material (glass, acrylic, plastic, etc.) of window  44 . In particular examples, the opto-luminescent material  46  can be a coating on the window  44 , impregnated or doped into the window  44 , or present as a gas  46 ′ between two sealed panels  44 ′,  44 ″ forming the window  44   a  (see enlarged view in  FIG. 4A ). 
         [0050]      FIG. 4B  is an example of a building  40 ′ containing another daylighting device  45   c ′ is depicted. The example of  FIG.4B  is substantially similar to that in  FIG. 4A , but no directional mirrors or prisms (or other optical devices) are included in this example. In the example of  FIG. 4B , the daylighting device  45   c ′ is positioned between the roof  41 ′ and the ceiling  42 ′. The entrance  45   c ″ of the daylighting device  45   c ′ is positioned on a side of the building  40 ′. The daylighting device  45   c ′ in the example extends horizontally from the side of the building  40 ′ to a desired position in the ceiling  42 ′. Somewhat different or angled orientation of the device may be used. The tunnel shaped daylighting device  45   c ′ allows light  47 ′ to enter the daylighting device  45   c ′ and follow the path of the directional arrow into interior room  43 ′. The inner surfaces  49 ′ of the daylighting device  45   c ′ may be reflective, e.g. specular, quasi-specular or diffusely reflective, to minimize losses as outlined earlier. The inner surfaces  49 ′ of this example are sufficiently reflective to pass light through the daylighting device from the entrance  45   c ″ to the exit into interior room  43 ′ to provide illumination  45   c ′″ to the room  43 ′. 
         [0051]    The example in  FIG. 5  is similar to that of  FIG. 4A , but for the design of the entrance  55 ′ of the daylighting device  55 . The entrance  55 ′ of the daylighting device  55  includes an additional prism or mirror member  55   c ′ which allows light  57  to enter the daylighting device  55  of building  50 . In the example of  FIG. 5 , the daylighting device  55  is positioned between the roof  51  and ceiling  52  with the entrance  55 ′ of the daylighting device positioned on a side of the building  50 . The daylighting device  55  extends horizontally from the side of the building to a desired position in the ceiling  52 . Such designed daylighting devices are commercially available and referred to as a “solar pipe”, “light pipe”, “light tube” and “tubular skylight”. Somewhat different or angled orientation of the device may be used. The tunnel shaped daylighting device  55  allows light  57  to enter the daylighting device at entrance  55 ′ and follow the path of the directional arrow into interior room  53 . The inner surfaces  59  of the daylighting device  55  may be reflective, e.g. specular, quasi-specular or diffusely reflective, to minimize losses as outlined earlier. The daylighting device  55  allows for the light entering the daylighting device and pass though a first prism or mirror member  55   c ′″ and travel along a direction between the roof  51  and ceiling  52  until it reaches the prism or mirror members  55   a ′″ and  55   b ′″ which alter the direction of the light into the interior room  53 . It should be noted that the prism or mirror members  55   a ′″,  55   b ′″ and  55   c ′″ are optional members and can be omitted in an alternative example similar to that described for  FIG. 4B . 
         [0052]    The opto-luminescent material  56  performs in substantially the same manner as the examples in  FIGS. 2 and 4 . The daylighting device  55  includes an opto-luminescent structure  58  for bearing an opto-luminescent material  56  associated with the exterior surface  55 ′. The opto-luminescent material  56  has excitation and emission spectra so as to convert a first portion of light  57  in a first spectral region to light in a second spectral region. Thus, at least some of the light transported to the left of the depicted opto-luminescent structure  58  will contain light in a second spectral region. The opto-luminescent structure  58  is configured so that at least some of the light in the second spectral region produced by excitation of the opto-luminescent material  56  is emitted into the interior of the building  50  in combination together with a second portion of the light passing through the entrance surface  55 ′. 
         [0053]    In the example of  FIG. 5 , the entrance  55 ′ of the daylighting device  55  protrudes outward from the side of the building  50  to better capture of the daylight  57 . Light  57  enters a substantially horizontal portion of the entrance and is reflected inward toward the interior of the building where light is reflected in towards the exit of the device  55  into the room  53 . Other more round shapes or orientations may be used to effectively capture or collect light  57  for use in the daylighting device  55 . Although not shown a color filter can be used in conjunction with or, as an alternative to the opto-luminescent material. 
         [0054]    The window  54  can optionally include a window dressing such as a shade or blind (not shown) having an opto-luminescent material included therein, as discussed above for the example of  FIG. 3A . Alternatively, or in combination with the window dressing, the opto-luminescent material  56  can be included in the material (glass, acrylic, etc.) of window  54 . 
         [0055]      FIGS. 6A and 6B  illustrate an alternative placement of the opto-luminescent material  66  in the daylighting device  65 , which is otherwise similar to the device of  FIG. 5 . FIG.  6 A shows morning light entering the daylighting device  65 , whereas  FIG. 6B  shows afternoon light entering the daylighting device  65 . 
         [0056]    In this example ( FIGS. 6A ,  6 B), the opto-luminescent material  66  is included on the opto-luminescent structure  68  adjacent to a side of the building  60 . The daylighting device  65  is positioned between the roof  61  and ceiling  62  with the entrance  65 ′ of the daylighting device positioned on a side of the building  60  to collect light  67 . The daylighting device  65  extends in the example horizontally from the side of the building  60  to a desired position in the ceiling  62 . The tunnel shaped daylighting device  65  allows light  67  to enter the daylighting device and follow the path of the directional arrow into interior room  63 . 
         [0057]    In the morning, the light  67  entering the daylighting device at the input of the opto-luminescent structure  68  is at an angle such that there is little or no excitation of the opto-luminescent material  66  by the light  67  ( FIG. 6A ). The color of light  67  is a warmer red in the morning; and therefore, there is no need to color correct the morning light entering the daylighting device  65 . Thus, due to the low position of the sun in the sky, the angle of light entering the daylighting device does tends not to substantially excite the opto-luminescent material  66 . The majority of the light  67  passes into the daylighting device  65  along the reflective tunnel shaped design and through prisms or mirrors  65   a, b, c ′″ and into room  63  to illuminate  65 ′ the interior of room  63 . The inner surfaces  69  of the daylighting device  65  may be reflective, e.g. specular, quasi-specular or diffusely reflective, to minimize loss of light back out of the entrance  65 ′ of the daylighting device  65 . 
         [0058]    In  FIG. 6B , as the day progresses and the sun continues to rise from the horizon to its peak in the sky, the light  67 ′ enters the daylighting device  65  at an angle sufficient to pump or excite the opto-luminescent material  66  positioned on the opto-luminescent structure  68 . The cooler blue and green colored light entering the daylighting device  65  will excite the opto-luminescent material  66  and the color corrected light of a warmer appearance will then enter the daylighting device and pass through mirrors or prisms  65   a, b, c ′″ before entering and illuminating  65 ″ the interior of room  63 . 
         [0059]      FIGS. 7A and 7B  depict another example of a daylighting device  75 , wherein the opto-luminescent material  76  is positioned at the entrance surface  75 ′ of the daylighting device  75 . The building  70  contains the daylighting device  75  that extends from the roof  71  into the ceiling  72  to provide illumination  75 ″ to interior room  73 . In this example, the device is vertical, although the device may be somewhat angled relative to vertical.  FIG. 7A  illustrates an example of morning light entering the daylighting device  75 , whereas  FIG. 7B  shows an example of afternoon light entering the daylighting device  75 . 
         [0060]    In this example, the device  75  includes a micro-channel plate  78 . The micro-channel plate  78  is a grating formed of a plurality of angled micro louver plates  78 ′. The material of the micro-channel plate is similar to that used in privacy filters for computer monitor screens. Commercially available micro louver control films are available. 3M manufactures Vikuiti™ Light Control Film which is a thin plastic film containing closely spaced micro louvers. The control film is cellulose acetate butyrate and is a transparent film. Instead of a black dye that is used in the Vikuiti™ Light Control Film to obscure or limit the viewing angle, it is replaced with a opto-luminescent dye. The opto-luminescent material  76  can be deployed as a dye or coating on, or embedded into, each angled micro louver plate  78 ′ of the grating  78 . Due to the angled micro louver plates  78 ′ in this example, the morning light  77  entering the daylighting device  75  will have minimal contact with the opto-luminescent material  76  contained within or on the angled micro louver plates  78 ′. Therefore, a substantial amount of light  77  will pass through the daylighting device  75  and illuminate room  73  with minimal excitation of the opto-luminescent material  76 . The opto-luminescent material  76 , for example, can be applied as a coating, impregnated or doped within the micro-channel plate  78 . 
         [0061]    Turning now to  FIG. 7B , as the day progresses and the sun continues to rise from the horizon to its peak in the sky, the light  77 ′ enters the daylighting device  75  at an angle sufficient to pump or excite the opto-luminescent material  76  positioned on or in the micro-channel plate  78 . The cooler blue and green colored light entering the daylighting device  75  will excite the opto-luminescent material  66  and the color corrected light will then enter the daylighting device before entering and illuminating  75 ″ the interior of room  73 . The remaining colors of light will pass through the micro-channel plate without exciting the opto-luminescent material  76 . 
         [0062]    In  FIG. 7B , as the day progresses and the sun continues to rise from the horizon to its peak in the sky, the light  77 ′ enters the daylighting device  75  at an angle sufficient to pump or excite the opto-luminescent material  66  positioned on or in the angled micro louver plates  78 ′. The cooler blue and green colored light entering the daylighting device  75  will excite the opto-luminescent material  76  and the color corrected light of a warmer appearance will then enter the daylighting device  75  and pass through the daylighting device before entering and illuminating  75 ″ the interior of room  73 . A color filter such as an absorption filter or reflective filter (not shown)n can be included in this example. 
         [0063]    The example of  FIG. 8  illustrates a shield  88  configured to retract over the opto-luminescent material  86 . The shield  88  has a specular or mirrored surface and is mechanically adjustable either by an automated controller/processor or by user adjustment. The user can also adjust the shield  88  through a wall switch or remote control device associated with the controller/processor, or some mechanical adjustment member can be operated by the user to manually adjust the position of the shield  88 . The daylighting device  85  in building  80  extends from the roof  81  and through the ceiling  82  to provide illumination  85 ″ in interior room  83 . The shield is adjustable throughout the day to help maintain a desired color temperature to illuminate room  83 . For example, during morning hours or later afternoon hours that approach sunset, the shield can be positioned over the opto-luminescent material  86  such that the morning or late afternoon light will pass through the daylighting device  85  and illuminate interior room  83  without pumping or exciting the opto-luminescent material  86  hidden behind the shield  88 . As the day progresses or weather conditions change (increase in cloud cover), the shield  88  can be adjusted (by user or automatically by a controller based on a preset color temperature selected by the user) such that the shield  88  can be retracted to expose the opto-luminescent material  86 . The now exposed opto-luminescent material  86  can convert or color correct the afternoon light to a predetermined color temperature. 
         [0064]    The concentration of the opto-luminescent material  86  can be varied to enable fine or course control of the desired color temperature while providing a large range of control. For example, a higher concentration of opto-luminescent material will color correct the natural light into a warmer colored light, typical of morning light or perhaps later afternoon light approaching sunset. Alternatively, the opto-luminescent density can be altered to provide a large range of control. In certain examples, different opto-luminescent material(s) can be used such that one or more different opto-luminescent materials are exposed by the shield  88  during different parts of the day or because of a change in weather conditions. For example one region of the structure bearing the opto-luminescent material could contain one or more opto-luminescent materials at one or more concentrations or density levels, whereas a second region of the structure could include other opto-luminescent material(s). It should be apparent that certain opto-luminescent materials may perform better at different times of the day or during certain weather conditions. 
         [0065]    It is desirable to improve performance of the daylighting device to maximize opto-luminescent emissions into an interior room of a building. It is also desirable to prevent opto-luminescent emissions back in other directions besides the interior room. Thus, a directional light guide deflector can be implemented to redirect trapped light in a desired direction. 
         [0066]    To this point, as shown in  FIGS. 9A and 9B , the opto-luminescent material  96 ,  96 ′ is contained in a film or sheet  97 ,  97 ′. The film or sheet  97 ,  97 ′ serves as a layer for containing the opto-luminescent material  96 ,  96 ′ therein. The film or sheet  97 ,  97 ′ contains indentations or divots  98 ,  98 ′ which serve as directional deflectors for pumped light  94 ,  94 ′ trapped in the film or sheet  97 ,  97 ′. Thus, in the daylighting device  95 , which is similar to that described above for  FIG. 2 , some of the pumped or excited light generated by the opto-luminescent material  96  can be trapped within the film or sheet  97  (or other container/structure housing the opto-luminescent material). The directional deflectors  98  redirect the trapped light  94  into the daylighting device, in the direction of the interior room, such as shown in one or more of the earlier examples. Thus, the emissions of the opto-luminescent material  96  can be maximized in the direction of the interior room. 
         [0067]    Similarly with  FIG. 9B , the daylighting device  95 ′ which is similar to that described above for  FIG. 8 , some of the pumped or excited light generated by the opto-luminescent material  96 ′ can be trapped within the film or sheet  97 ′ positioned between the mirrored surfaces  99  and the shield ( FIG. 8 ). The directional deflectors  98 ′ redirect the trapped light  94 ′ out of the film or sheet and into the daylighting device  95 ′. Thus, the emissions of the opto-luminescent material  96 ′ can be maximized into the interior room. In  FIG. 9B , any light  94 ″ that escapes the film or sheet  97 ′in the direction of the specular or mirror surface  99  of the daylighting device  95 ′, is redirected by the specular or mirror surfaces  99  towards into the daylighting device  95 ′. Accordingly, cooler blue and green colored light entering the daylighting device  95 ,  95 ′ will excite the opto-luminescent material  96 ,  96 ′ and the color corrected light of a warmer appearance will then enter the daylighting device  95 ,  95 ′ and pass through the daylighting device  95 ,  95 ′ before entering and illuminating an interior room of a building containing the daylighting device  95 ,  95 ′. 
         [0068]    Fiber optics can also be used for color correction of daylighting. Commercially available optical fibers of most any variety can be used. Optical fibers manufactured by Corning Inc., are but one example. Optical fibers that include an input links that are transmissive light of a variety of wavelengths, including but not limited to ultraviolet light, are advantageous. 
         [0069]    In the daylighting device  105  example shown in  FIG. 10 , one or more fiber optic cables  104  are associated with a solar collector  107  positioned on roof  101  of building  100 . The fiber optic cable(s)  104  extend from the solar collector  107  down through the ceiling  102  to provide illumination  105 ′ to interior room  103 . The solar collector  107  in this example is configured to track the position of the sun and concentrate the sun&#39;s light by rotation and/or pivoting motion. The solar collector  107  is positioned for optimal tracking of the sun during daylight hours. It can be mounted on the exterior side of the building  100  rather than on the roof  101 . The opto-luminescent material  106  which is concentrated in a container  106 ′ is excited by light provided from the solar collector  107  and passed into the optical cable(s)  104  to provide the interior room with illumination  105 ′. The opto-luminescent material  106  can optionally include a control mechanism for actively or passively changing the spectral content of daylight of a particular spectral range that is captured by the solar collector  107 . 
         [0070]    The daylighting device  105  can be adjusted to control the color temperature through a control mechanism associated with the daylighting device  105 . Examples of such control mechanisms  100  and  200  are illustrated in  FIGS. 11 and 12 , respectively. In  FIG. 11 , a first portion of the optical cable  104   a  coming from a solar collector  105  ( FIG. 10 ) has a fiber optic aperture  104   a ′ positioned adjacent to a surface of the junction container  106 ′ housing the opto-luminescent material  106 . The opto-luminescent material  106  contained in the junction container  106 ′ is more concentrated in region  106   a  than region  106   b.  The fiber optic aperture  104   a ′ can be movably adjusted between regions  106   a  and  106   b  to control the color temperature. More than one optical fiber can be used and provide light to the interior of the building at more than one location. The higher the concentration of opto-luminescent material, the warmer the light output is from the container  106 ′ along optical path  111   a  and into coupling lens  108 . Light from the coupling lens  108  exits into the optical fiber  104   b  via optical path  111   b  which then proceeds to the interior room  103  ( FIG. 10 ) along fiber optic cable  104 . 
         [0071]    The control mechanism  200  example in  FIG. 12  includes a reservoir  206 ′ (first reservoir) for dispensing an amount of opto-luminescent material  206  into a bladder capsule  206 ′″ (second reservoir) by way of a connection  206 ′″. In  FIG. 12 , a first portion of the optical cable  204   a  coming from a solar collector  105  ( FIG. 10 ) has a fiber optic aperture  204   a ′ positioned adjacent to a surface of the bladder capsule  206 ″ housing the opto-luminescent material  206 . The opto-luminescent material is added into the bladder capsule based on the desired color temperature. The more opto-luminescent material  206  that is added to the bladder capsule  206 ″, the warmer the light output from the bladder capsule  206 ″ along optical path  211   a  and into coupling lens  208 . Light from the coupling lens  208  exits into the optical fiber  204   b  via optical path  211   b  which then proceeds along into the interior room  103  ( FIG. 10 ). If a cooler colored light is desired the amount of opto-luminescent material  206  is reduced and returned to the reservoir  206 ′. 
         [0072]    With the control mechanisms  100  and  200  of  FIGS. 11 and 12 , respectively, the color temperature control can be adjusted by way of user control such as a wall switch or remote control in an interior room of the building ( FIG. 10 ). Alternatively, the control mechanism  100 ,  200  can be set to a predetermined color and the control mechanism  100 ,  200  is automatically adjusted by way of a processing device or controller with associated power supply. The processing device or controller could be hard-wired logic or a programmed microprocessor with associated memory devices. Typically, the processing device is a Micro-Control Unit (MCU), which controls operations of the respective mechanisms  100 ,  200 . The MCU may be a microchip device that incorporates a processor serving as the programmable central processing unit (CPU) of the MCU and thus of the control mechanisms  100 ,  200  of  FIGS. 11 and 12  as well as one or more memories accessible to the CPU. The memory or memories store executable programming for the CPU as well as data for processing by or resulting from processing of the CPU. The MCU may be thought of as a small computer or computer like device formed on a single chip. Such devices are often used as the configurable control elements embedded in special purpose devices rather than in a computer or other general purpose device. 
         [0073]    It will be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein. Relational terms such as first and second and the like may be used solely to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “includes,” “including,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “a” or “an” does not, without further constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. 
         [0074]    Unless otherwise stated, any and all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, including in the claims that follow, are approximate, not exact. They are intended to have a reasonable range that is consistent with the functions to which they relate and with what is customary in the art to which they pertain. 
         [0075]    While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that the teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings.