Abstract:
A lamp structure of an adaptive streetlight includes a housing, a plurality of light sources, and a surface-structured diffusion plate. The surface-structured diffusion plate enables the lamp structure to provide a light pattern conforming to the curvature of the road to be illuminated or other sites of application, thus reducing not only the number of lamps or streetlights required for a curvy road section, but also the associated installation cost and power consumption. The lamp structure can enhance road users&#39; safety and the safety of our daily lives by increasing the illuminance on a curvy road and other sites of application that have special requirements.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a lamp structure and more particularly to a lamp structure which is applicable to an adaptive streetlight and which has a surface-structured diffusion plate in order to provide a particular light pattern that matches the curvature of the road section to be illuminated. 
     2. Description of Related Art 
     Nowadays, with the expansion of transportation networks, the quality of road lighting determines to a large extent whether the roads being illuminated are safe. Road lighting, therefore, plays an important role in the safety of life and property of all road users. 
     The conventional streetlights, be they equipped with the traditional light bulbs or the more energy-saving LEDs, cannot change their light patterns according to road curvatures. While the resulting problem of insufficient lighting can be solved by installing more streetlights, a significant increase in cost and energy consumption ensues. 
       FIG. 7A  is a schematic top view of a road illuminated by a plurality of conventional streetlights  500  or commercially available streetlights. Typically, the light pattern  510  of the light projected on the ground by a conventional streetlight  500  is localized and lies only around the streetlight such that the road surface is poorly lit. Aside from an uneven distribution of illuminance over the road surface, part of the optical energy is cast outside the road. If the road has a steep slope, the light may even strike the road users&#39; eyes, which causes glare and a considerable waste of energy. 
     To achieve the road surface illuminance required by law, it is common practice to increase the working power or number of the conventional streetlights  500 , leading, however, to excessive power consumption or a wasteful use of resources. 
     Moreover, some conventional streetlights  500  or commercially available streetlights have a conventional diffusion plate, which is generally made by incorporating micro particles into a substrate, coating a substrate with micro particles, or providing a substrate with a diffusive surface structure. 
     Mixing micro particles into a substrate does increase diffusivity effectively but reduces permeability of light. Coating a substrate with micro particles tends to have a low yield, and the coated substrate is prone to damage and diffuses light in directions that cannot be controlled. 
     A diffusive surface structure, on the other hand, is typically made by grinding a substrate&#39;s surface with micro particles so that the surface has an irregular roughened texture. A notable example of products with a diffusive surface structure is ground glass. While such surface structures are diffusive to a certain degree, the directions of light diffusion remain uncontrollable. 
     In view of the above, it is an important issue for the lighting industry or even the entire transportation industry to overcome the aforesaid drawbacks of the conventional streetlights  500  and to provide a lamp structure which meets the requirements of highly uniform light distribution, high diffusivity, and high permeability of light, and which therefore contributes to enhancing the quality of life of the general public. To this end, it is most desirable that a highly efficient refractive optical element (ROE), or more particularly a surface-structured diffusion plate, can be made by forming a micro lens array (i.e., surface structure) on the surface of a substrate. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention relates to a lamp structure of an adaptive streetlight, wherein the lamp structure includes a housing, a plurality of light sources, and a surface-structured diffusion plate. The surface-structured diffusion plate, or called surface-structured diffuser (SSD), enables the lamp structure to provide a light pattern conforming to the curvature of the road to be illuminated or other sites of application, thus reducing not only the number of lamps or streetlights required for a curvy road section, but also the associated installation cost and power consumption. More importantly, the present invention enhances road users&#39; safety and the safety of our daily lives by increasing the illuminance on a curvy road and other sites of application that have special requirements. 
     More specifically, the present invention provides a lamp structure of an adaptive streetlight, wherein the lamp structure includes: a housing with a bottom surface and an opening; a plurality of light sources fixedly provided on the bottom surface of the housing; and a surface-structured diffusion plate, which is a light-permeable plate connected to the opening and provided with a plurality of microstructures, each microstructure having a curved or parabolic surface as a light-receiving surface. 
     Implementation of the present invention at least produces the following advantageous effects: 
     1. The cost of implementation is low because no complicated manufacturing process or equipment is required. 
     2. The number of lamps or streetlights required for a curvy road section can be reduced to cut installation cost and power consumption. 
     3. The illumination of a curvy road section can be enhanced to increase drivers&#39; and other road users&#39; safety. 
     4. Different light patterns can be produced by only replacing different surface-structured diffusion plates according to practical needs. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view of the lamp structure of an adaptive streetlight in an embodiment of the present invention; 
         FIG. 2  is a schematic sectional view of the lamp structure of an adaptive streetlight in another embodiment of the present invention, wherein the lamp structure has light-condensing devices; 
         FIG. 3A  is a schematic view of an embodiment of the present invention, wherein the light-condensing devices are condenser lenses; 
         FIG. 3B  is a schematic view of an embodiment of the present invention, wherein the light-condensing devices are reflectors; 
         FIG. 4  schematically shows the surface-structured diffusion plate in an embodiment of the present invention; 
         FIG. 5A  is a schematic perspective view of the surface-structured diffusion plate in an embodiment of the present invention; 
         FIG. 5B  schematically shows the particular light pattern produced by the surface-structured diffusion plate in  FIG. 5A ; 
         FIG. 6A  is a schematic perspective view of the surface-structured diffusion plate in another embodiment of the present invention; 
         FIG. 6B  schematically shows the particular light pattern produced by the surface-structured diffusion plate in  FIG. 6A ; 
         FIG. 7A  schematically shows the light patterns projected on a curvy road by conventional streetlights; 
         FIG. 7B  schematically shows the particular light patterns projected on a curvy road by lamp structures in an embodiment of the present invention; 
         FIG. 8A  shows the dimensions of a microstructure in an embodiment of the present invention; 
         FIG. 8B  schematically shows a surface-structured diffusion plate composed of a plurality of microstructures as depicted in  FIG. 8A ; 
         FIG. 8C  is a schematic perspective view of the microstructure in  FIG. 8A ; 
         FIG. 8D  schematically shows the particular light pattern produced by the surface-structured diffusion plate in  FIG. 8B ; 
         FIG. 9A  schematically shows a microstructure in another embodiment of the present invention; 
         FIG. 9B  schematically shows a surface-structured diffusion plate composed of a plurality of microstructures as depicted in  FIG. 9A ; 
         FIG. 9C  is a schematic perspective view of the microstructure in  FIG. 9A ; 
         FIG. 9D  schematically shows the particular light pattern produced by the surface-structured diffusion plate in  FIG. 9B ; 
         FIG. 10A  schematically shows a microstructure in yet another embodiment of the present invention; 
         FIG. 10B  schematically shows a surface-structured diffusion plate composed of a plurality of microstructures as depicted in  FIG. 10A ; 
         FIG. 10C  is a schematic perspective view of the microstructure in  FIG. 10A ; 
         FIG. 10D  schematically shows the particular light pattern produced by the surface-structured diffusion plate in  FIG. 10B ; 
         FIG. 11A  schematically shows how the particular light pattern produced by a surface-structured diffusion plate composed of a plurality of microstructures as depicted in  FIG. 10A  changes with the width of each microstructure; 
         FIG. 11B  schematically shows how the particular light pattern produced by a surface-structured diffusion plate composed of a plurality of microstructures as depicted in  FIG. 10A  changes with the depth of each microstructure; 
         FIG. 12A  is a side sectional view of the surface-structured diffusion plate in an embodiment of the present invention; 
         FIG. 12B  schematically shows the particular light pattern produced by the surface-structured diffusion plate in  FIG. 12A ; 
         FIG. 13A  is a side sectional view of the surface-structured diffusion plate in another embodiment of the present invention; 
         FIG. 13B  schematically shows the particular light pattern produced by the surface-structured diffusion plate in  FIG. 13A ; and 
         FIG. 14  schematically shows an adaptive streetlight with the lamp structure of the present invention and a lighting support. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , the lamp structure  100  of an adaptive streetlight in an embodiment of the present invention includes a housing  10 , a plurality of light sources  20 , and a surface-structured diffusion plate  30 . The surface-structured diffusion plate  30  has a light-receiving surface provided with a plurality of microstructures  40 . 
     As shown in  FIG. 1 , the housing  10  serves as the lampshade of the lamp structure  100  and has a bottom surface  11  and an opening  12  located opposite the bottom surface  11 . There is no limitation on the material of the housing  10 . Generally speaking, the housing  10  is made of a lightweight, sturdy, and heat-resistant material. 
     The inner wall of the housing  10  can be formed of a high-reflectivity material for reflecting light, or more particularly for reflecting backward light, generated by the surface-structured diffusion plate  30  reflecting light toward the inner wall of the housing  10 , via a photon recycling mechanism so that the backward light is projected back toward the surface-structured diffusion plate  30  and becomes forward light. The goal is to increase light output and enhance the optical efficiency of the entire lamp structure  100 . 
     As shown in  FIG. 1 , the light sources  20  are fixedly provided on the bottom surface  11  of the housing  10 . Each light source  20  can be an LED (light-emitting diode) light source  20  composed of at least one LED, or an OLED (organic light-emitting diode) light source  20  composed of at least one OLED. 
     With continued reference to  FIG. 1 , the surface-structured diffusion plate  30  is connected to the opening  12  of the housing  10  and is a light-permeable plate. As previously mentioned, the surface-structured diffusion plate  30  has a light-receiving surface provided with a plurality of microstructures  40 . Each microstructure  40  is a curved surface or a parabolic surface. The microstructures  40  are provided on the surface-structured diffusion plate  30  in a concave manner, in a protruding manner, or partly in a concave manner and partly in a protruding manner. 
     Referring to  FIG. 4  in conjunction with  FIG. 1 , each curved- or parabolic-surface microstructure  40  has a length L, a width W, and a depth H. 
     The surface-structured diffusion plate  30  may also be composed of a plurality of micro lenses arranged in an array, as shown in  FIG. 5A  and  FIG. 6A . 
     Referring to  FIG. 1 ,  FIG. 4 ,  FIG. 5A , and  FIG. 6A , whether the microstructures  40  of the surface-structured diffusion plate  30  are curved surfaces, parabolic surfaces, or micro lenses, a dimension (the length L or the width W) of each microstructure  40  can be so chosen that it is greater than ten times the wavelength of the light emitted by each light source  20 . 
     Referring now to  FIG. 2 , each light source  20  of the lamp structure  100  may be further connected with a light-condensing device  50 . Each light-condensing device  50  has a projection opening  51  corresponding to the opening  12  of the housing  10 . 
     Each light-condensing device  50  serves mainly to collect the light emitted by the corresponding light source  20  and project the light through the projection opening  51  of the light-condensing device  50  toward the opening  12  of the housing  10 . After light pattern modulation by the surface-structured diffusion plate  30 , the light is eventually output from the opening  12  of the housing  10 . 
     As shown in  FIG. 3A  and  FIG. 3B , the light-condensing devices  50  can be condenser lenses  60  (e.g., total internal reflection lenses, or TIR lenses) or reflectors  70 , provided that the light-condensing devices  50  can each reflect and collect the light emitted by the corresponding light source  20  and project the light out of the projection opening  51  of the light-condensing device  50 . 
       FIG. 5A  schematically shows the surface-structured diffusion plate  30  in an embodiment of the present invention in perspective view. A lamp structure  100  with the surface-structured diffusion plate  30  in  FIG. 5A  produces a rectangular light pattern as shown in  FIG. 5B . 
       FIG. 6A  shows the surface-structured diffusion plate  30  in another embodiment of the present invention. A lamp structure  100  with the surface-structured diffusion plate  30  in  FIG. 6A  produces a curved light pattern as shown in  FIG. 6B . 
     As shown in  FIG. 1  through  FIG. 6B  and  FIG. 7B , the light emitted by each light source  20  on the bottom surface  11  of the housing  10  is modulated by the corresponding light-condensing device  50  in terms of light propagation direction so that the light projected from the projection opening  51  of the light-condensing device  50  propagates at a small angle of divergence. This light with a small divergence angle passes through the surface-structured diffusion plate  30 , is modulated by and subjected to the beam shaping effect of the specially designed microstructures  40  on the surface of the surface-structured diffusion plate  30 , and thus forms a particular light pattern  200  conforming to the shape of the road to be illuminated. The user may replace an existing surface-structured diffusion plate  30  with one of a different configuration in order to obtain the desired light pattern  200  and serve the adaptive function of an adaptive streetlight. 
     In other words, when used to illuminate a curvy road section, as shown FIG.  7 B, the lamp structure  100  of an adaptive streetlight can produce a light pattern  200  that suits the curvature of the road section to enhance illuminance on the road surface and consequently road users&#39; safety while saving both resources and power. 
       FIG. 8A  through  FIG. 8D ,  FIG. 9A  through  FIG. 9D , and  FIG. 10A  through  FIG. 10D  show another three different microstructures  40  and the square light pattern, rectangular light pattern, and curved light pattern produced by surface-structured diffusion plates  30  having those different microstructures  40  respectively. 
     In the embodiment shown in  FIG. 10A  to  FIG. 10D , and  FIG. 11A  to  FIG. 11B , wherein the light pattern  200  is a curved light pattern, increasing the width W of each microstructure  40  (indicated by the arrow in  FIG. 11A ) shortens and thickens the curved light pattern, and increasing the depth H of each microstructure  40  (indicated by the arrow in  FIG. 11B ) elongates and thickens the curved light pattern. This also helps to show that different light patterns can be produced by only replacing different surface-structured diffusion plates  30  according to practical needs. 
     This further demonstrates that the light pattern  200  of the lamp structure  100  of an adaptive streetlight can be modified by choosing the desired microstructures  40  for the surface-structured diffusion plate  30 . By changing the shape of the microstructures  40 , a light pattern suitable for the intended application can be obtained. Thus, not only can the lamp structure  100  of an adaptive streetlight effectively concentrate, confine, and evenly project the light of the streetlight to the target area, but also the microstructures  40  can be modified to effectively control the light output angle according to the shape of the road to be illuminated, in order to produce a particular light pattern  200  that conforms to the shape of the road. 
       FIG. 12A  and  FIG. 12B  respectively show a side sectional view of the surface-structured diffusion plate  30  in an embodiment of the present invention and the light pattern produced through the surface-structured diffusion plate. The surface-structured diffusion plate  30  in  FIG. 12A  is composed of microstructures  40  of the same shape, and the resulting light pattern features a uniform distribution of brightness. 
     In  FIG. 13A , at least one of the microstructures  40  is different in shape from the rest of the microstructures  40 . Accordingly, referring to  FIG. 13B , the light pattern produced through the surface-structured diffusion plate  30  composed of the microstructures  40  in  FIG. 13A  is less uniform in brightness than that in  FIG. 12B . Further, by using microstructures  40  of different structural dimensions to control energy distribution, the modulated light pattern is rendered dimmer in the two end regions than in the middle to facilitate the joining of two different light patterns at adjacent road sections. 
     Referring to  FIG. 14 , the lamp structure  100  is fixedly provided on a lighting support  80 . The lighting support  80  can be a lighting support configured to stand directly on the ground or to be fixedly provided on the surface of an object. The lighting support  80  also delivers electricity to the lamp structure  100  and allows the light emitted by the lamp structure  100  to be projected in the intended direction.