Abstract:
A light fixture with an optical reflection structure, comprising a lamp housing having at least one open accommodating space for light beam to be emitted outward therefrom; a plurality of connectors for coupling a light tube to the light fixture, the connectors being located at both opposite ends in a longitudinal direction of the accommodating space; a reflector having a curved surface affixed with a composite mirror film for light reflection, the reflector being located in the accommodating space and substantially covering at least a part of a surface of the accommodating space, wherein the curved surface is determined based on law of reflection by optimizing a luminous flux of primary reflection light reflected off the reflector to the extent of 90% or more compared with a naked light source from the light tube. The light fixture of the invention provides sufficient illumination and prolongs the lifespan of the light tube in a cost-economic way, thus directly saving energy and reducing the production of carbon.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    a) Field of the Invention 
         [0002]    The invention relates generally to a lighting structure, and more particularly, to a light fixture with an optical reflection structure for efficient illumination. 
         [0003]    b) Description of the Related Art 
         [0004]    The invention of lamps contributes a lot to the modern society. Realistically speaking, lighting apparatus (luminaire) has become essential to our daily lives today. In general, the conventional lighting apparatus  10  as shown in  FIG. 1  includes a lamp housing  11  having an accommodating space  111 , at least one light tube  12 , and a reflex louver  13 , in which the light tube  12  and the reflex louver  13  are disposed within the accommodating space  111  of the lamp housing  11 , with the light tube  12  located between the lamp housing  11  and the reflex louver  13 . However, according to optical reflection principle, conventional design of the lighting apparatus needs to be improved significantly in terms of the following points. 
         [0005]    First, in the interior of the lamp housing  11 , ineffective diffused light condenses due to the reflex louver  13 , resulting in the so-called green house effect of the lamp housing  11  because of the temperature rise therein. Also, the temperature rise will inevitably ruin the structure of the luminaire so that the light tube and the internal circuits deteriorate acceleratively. The lighting apparatus therefore has an increased replacement rate of the light tube and the circuits. 
         [0006]    Second, due to the reflex louver  13  as well, most of the light emitted from the light tube  12  cannot be reflected out of the lamp housing efficiently, leading to an insufficient light output for a desired illumination. In other words, the conventional lighting apparatus fails to achieve highest reflection efficiency. Accordingly, a relatively large percentage of light energy goes to waste when using the conventional lighting apparatus, which is diametrically opposed to the worldwide trend towards energy-saving and carbon-reduction policies. 
         [0007]    In view of the above, the present inventor has been devoted to developing a light fixture with an efficiency-optimized optical reflection arrangement that provides more effective illumination to the surroundings. 
       SUMMARY OF THE INVENTION 
       [0008]    An object of the invention is to provide efficiency-optimized illumination at a minimized power consumption and energy costs. Another object of the invention is to prolong the lifespan of a lighting apparatus by providing an optimal output of reflective light, thereby reducing the level of greenhouse effect on the light space. Still another object of the invention is to provide a uniform output of reflective light by rapid focus adjustment. 
         [0009]    In order to achieve the above objects, the invention provides a light fixture with a lamp housing having at least one open accommodating space for light beam to be emitted outward therefrom; a plurality of connectors for coupling a light tube to the light fixture, the connectors being located at opposite ends in a longitudinal direction of the accommodating space; a reflector with a curved surface to which a composite mirror film is affixed for light reflection, the reflector being located in the accommodating space and substantially covering at least a part of a surface of the accommodating space, wherein the curved surface is determined based on law of reflection by optimizing a luminous flux of primary reflection light reflected off the reflector to the extent of 90% or more compared with a naked light source from the light tube. 
         [0010]    In one aspect of the invention, the composite mirror film is composed of five layers comprising a supporting layer; a principal reflection layer formed on the supporting layer; a transparent protection layer made from a non-metal based anti-reflection film and formed on the principal reflection layer; a thickening layer for a flexible adjustment in an overall thickness of the composite mirror film, the thickening layer being a bottom layer of the composite mirror layer; and an anaerobic hardening adhesive layer for bonding the supporting layer to the thickening layer. In another aspect of the invention, the composite mirror film is free of the supporting layer and thus composed of four layers. 
         [0011]    In one aspect of the invention, there is provided the light fixture, in which the curved surface of the reflector possesses an approximately parabolic profile, an approximately semicircular profile, an approximately semi-elliptical profile, or a combination thereof. In another aspect of the invention, a light blocking sheet with a curved surface of an approximately semicircular profile is disposed adjacently to the connector. 
         [0012]    Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The above and other objects, advantages and features of the invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings, in which: 
           [0014]      FIG. 1  is a two-dimensional view schematically illustrating the configuration of a conventional lighting apparatus as well as the light path therewithin. 
           [0015]      FIG. 2  is a three-dimensional view illustrating the structure of the lighting apparatus according to the invention. 
           [0016]      FIGS. 3A-3E  are cross-section views each illustrating the position relationship between the light tube and the reflector, and the resultant reflective light paths. 
           [0017]      FIGS. 4A-4B  are cross-section views illustrating the constituent layers in sequence in two different types of the composite mirror films according to the invention. 
           [0018]      FIGS. 5A-5C  are cross-section views each illustrating the position relationship between the light tube and the reflector according to some representative aspects of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    The invention will be described with reference to illustrative examples in the following. However, it should be understood by one of ordinary skill in the art that the invention may be practiced without some or all of these specific details. In other instance, well known process operations have not been depicted in detail in order not to unnecessarily obscure the invention. 
         [0020]    For example,  FIG. 2  shows the lighting apparatus  20  of one aspect of the invention, which includes a lamp housing  30 , four connectors  40 , and two reflectors  50  each having a curved surface  51 , wherein two light tubes  60  can be received in two open accommodating spaces  31  respectively by the connectors  40 . The word “open” means that the accommodating space  31  provides a region for the light emitted from the light tube to “interact” with the surroundings and this should not be interpreted as a limiting condition. The lamp housing  30  may be made from, for example, aluminum or iron, or any other suitable materials. However, the number of the open accommodating spaces  31  in one lighting apparatus  20  may be determined as the case may be. For the convenience of illustration, two accommodating spaces  31  are distributed in parallel inside the lamp housing  30  in this example. It goes without saying that the other accommodating space  31  also has to be configured following the same way as mentioned above. 
         [0021]    The lamp housing  30  may be integrally manufactured into one-piece by an injection molding technique, or it can be assembled by individually putting all the parts together or by any other suitable ways as long as a similar configuration can be acquired. By the way, the manufactured lamp housing  30  according to the invention preferably complies with the UL-94V0 standard. 
         [0022]    Connectors  40  are paired off and spaced apart from each other by a specified distance at the opposite ends in a longitudinal direction of the accommodating space  31 . In  FIG. 2 , there are two connectors for one accommodating space for example. However, the number of the connectors  40  can be specified as desired. For a common light tube  60 , there is a connecting part  61  as shown in  FIG. 2  formed at both sides thereof. Therefore, each connector  40  is provided with one or more conjunction sites  41  for facilitating the coupling of the common light tube  60 . The shapes and the locations of the conjunction sites  41  on the connector  40  may be designed appropriately matching with the shape of the connecting part  61  so that the vertical separation between the light tube  60  and the reflector  50  (or the composite mirror film  52 ) can be adjusted easily. Varying such a vertical separation can desirably manipulate the outward illumination area, as can be seen from  FIGS. 3A and 3B  described below. 
         [0023]    It is well known that the reflector always plays a critical role in the design of a light fixture. The reflector  50  of the invention is housed in the accommodating space  31  as well and is configured to have a curved surface  51  possessing an approximately parabolic profile ( FIGS. 3A and 3B ), an approximately semi-circular profile ( FIG. 3C ), an approximately semi-elliptical profile ( FIG. 3D ), or a combination thereof (a “blend type” profile,  FIG. 3E ) or the like. Among others,  FIG. 3A and 3B  respectively show the schematic results for two different vertical separations between the light tube  60  and the reflector  50 . To be specific, the reflector  50  of the invention is characterized by the aforementioned curved surface  51  affixed at least partly with a composite mirror film  52 . 
         [0024]    The profile of the curved surface  51  of the reflector  50  is determined based on law of reflection by optimizing a luminous flux of primary reflection light reflected off the reflector to the extent of 90% or more compared with a naked light source from the light tube. In detail, the total luminous flux of the light tube (surface source) to the surrounding is calculated by summing up the individual one of the numerous “point sources”. Then the curvature of the curve surface  51  is “trimmed” experimentally and empirically according to law of reflection (i.e. an angle of incidence is equal to an angle of reflection) to optimize the total luminous flux of primary reflection light. Specifically, part of the primary reflection light blocked by the light tube  60  itself should be reasonably excluded from the calculation of the luminous flux. On the contrary, the direct light from the light tube  60  should be taken into consideration. In summary, by using the light fixture according to the invention, the light output ratio defined as dividing the luminous flux of the reflected light from the curved surface  51  of the reflector  50  by the overall luminous flux of a naked light source can be optimized to be more than 90% that is hardly achieved by the conventional technology. 
         [0025]    The composite mirror film  52  consists of four or five sequential layers.  FIG. 4A  is a cross-section view of the stacking order of the composite mirror film  52  comprising five layers. These five layers are in sequence the transparent protection layer (referred to as “the first layer” hereinafter)  5 - 1 , the principal reflection layer (referred to as “the third layer” hereinafter)  5 - 3 , the supporting layer (referred to as “the second layer” hereinafter)  5 - 2 , the adhesive layer (referred to as “the fourth layer” hereinafter)  5 - 4 , and the thickening layer (referred to as “the fifth layer” hereinafter)  5 - 5 , as  FIG. 4A  shows. 
         [0026]    The first layer  5 - 1  is formed by vacuum-evaporating a non-metal based anti-reflection film, laminating the anti-reflection film with polymethyl methacrylate (PMMA) or polyurethane (PU) preferably to a thickness of about 2-3 μm, then curing the laminated film via ultraviolet (UV) light. The vacuum evaporation process should be well known to a person of ordinary skill in the technology of manufacturing optical devices. In addition, a person of ordinary skill in this art understands that the anti-reflection film may be selected from the low-refractive material such as glass, an optical plastic, SiOx like SiO2 or SiO, titanium dioxide (TiO2), alkali metal fluoride like lithium fluoride (LiF), or alkali earth metal fluoride like magnesium fluoride (MgF2) or calcium fluoride (CaF2). In brief, the first layer  5 - 1  acts as a transparent shield protecting the composite mirror film  52  without causing any negative effect on light transmission. 
         [0027]    The second layer serves as a supporting substrate and is formed by subjecting the film made from a suitable plastic material having a turbidity of 0.01 or less to a coiling process. The inventor found that an optical plastic with turbidity of 0.01 or less can meet the requirement of the invention as a good substrate candidate. The suitable optical plastic may be polyethylene terephthalate (PET), polycarbonate (PC) or polymethyl methacrylate (PMMA). More preferably, the thickness of the second layer may be controlled at about 20 μm. Among them, PMMA is preferred in terms of optical properties. It is to be noted that in another aspect of the invention, the composite mirror film  52  doesn&#39;t include the second layer (i.e. the supporting layer)  5 - 2 , as shown in  FIG. 4B . 
         [0028]    The third layer, which is formed on the second layer, is made from pure metal (e.g., 99.99%) with a high reflectivity, such as aluminum, gold, silver, platinum or rhodium, using a vacuum evaporation process. Also, the third layer may be made from a nonmetal—TiO2, which has a high reflectivity within the visible region. However, a person of ordinary skill knows that a multi-layered film is formed when selecting TiO2 as the material of the third layer. Obviously, the third layer substantially serves as a reflective film. By the way, although there is no special bound to the thickness of the third layer, it is preferably in the range of several nanometers. 
         [0029]    Referring to  FIG. 4A , the second layer  5 - 2  is bond to the bottom layer (i.e. the fifth layer as will be described later)  5 - 5  via a thin anaerobic hardening adhesive  5 - 4  preferably with a thickness of 1-3 μm, 2 μm more preferably. This adhesive layer may be considered as the fourth layer contained in the composite mirror film  52 . However, referring back to  FIG. 4B , since the supporting layer  5 - 2  may be omitted in one aspect of the invention, the anaerobic hardening adhesive  5 - 4  is used to bond the third layer  5 - 3  rather than the second layer  5 - 2  to the bottom layer  5 - 5 . 
         [0030]    The integral thickness of the composite mirror film  52  is also a key factor in the illumination performance. The bottom layer of the composite mirror film  52 , the fifth layer  5 - 5 , is made from an optical plastic such as polyethylene terephthalate (PET), polycarbonate (PC) or polymethyl methacrylate (PMMA). It functions as a thickening film used for adjusting the integral thickness of the composite mirror film  52  to a desired level. In other words, the thickness of the composite mirror film  52  can reach a desired level by manipulating the thickness of the fifth layer. It is noted that attaching the fifth layer  5 - 5  to the second layer  5 - 2  or the third layer  5 - 3  via the fourth layer  5 - 4  will be the final step of preparing the composite mirror film  52 . 
         [0031]    As stated above, the vertical separation between the light tube  60  and the reflector  50  (or the curved surface  51 ) may be adjusted by engaging the connecting part of the light tube with different conjunction sites  41  of the connector  40 . It is appreciated that a plurality of connectors  40  may be provided to the lamp housing  30  beforehand, and they may be positioned side by side, in a staggered manner, or in any other suitable form as needed. 
         [0032]    Similarly to  FIGS. 3A-3E ,  FIGS. 5A-5C  are cross-section views illustrating the position relationships between the lamp housing  30  and the reflector  50  of different curved surfaces and the resultant light reflections, except that a light blocking sheet  70  having a curved surface on the side facing the light tube  60  is provided to the lamp housing  30  at both sides thereof under the connector  40 . The functions of the light blocking sheet  70  are, on one hand, making the user feel comfortable if directly viewing the light tube  60  unintentionally; on the other hand, primarily reflecting the direct light emitted from the light tube  60  so as to increase the total luminous flux. Accordingly, onto the curved surface of the light blocking sheet  70  facing the light tube  60 , the composite mirror film  52  also has to be affixed. At the same time, the light blocking sheet  70  has a width equal to or slightly larger than the diameter of the light tube  60  in order to elaborate its functions. 
         [0033]    For the light fixture of the invention, since the temperature around the accommodating space  31  can be maintained below 50° C. in practice, it is unnecessary to limit the material of the light blocking sheet  70  to a heat resistant one. For example, the material may be the same as that of the lamp housing. As well, there is no special limitation to either the profile of the curved surface of the light blocking sheet  70  or the vertical separation between the light tube  60  and the light blocking sheet  70 . However, it is noted that the light blocking sheet  70  should have an upwardly convex profile for the surface facing the light tube  60  as shown in  FIGS. 3A-3E , taking the effect of the primary reflection into consideration. Preferably, the light blocking sheet  70  may have the curved surface of an approximately parabolic profile, an approximately semicircular profile, an approximately semi-elliptical profile, or a combination thereof, similarly to the reflector  50  mentioned above. 
         [0034]    Although the embodiments of the invention have been illustrated in the above, the invention is not limited to the aforementioned embodiments. Various equivalent changes and modifications can be made from the above embodiments without departing from the scope of the invention. All such changes and modifications as would be obvious to one of ordinary skill in the art are intended for inclusion within the scope of the invention.