Patent Publication Number: US-7217010-B2

Title: Reflector with negative focal length

Description:
FIELD OF THE INVENTION 
   The present invention relates to a reflector with negative focal length, and more particularly, to a reflector with negative focal length adapted for replacing the reflector with positive focal length arranged at the upper area of a common luminaire screen, by which rays emitting from the lamp of the luminaire are reflected and directed to a preferred discharging area so as to enable the rays to be discharge out of the luminaire by large angles for reducing glare, in addition, the height of the luminaire can be reduced. 
   BACKGROUND OF THE INVENTION 
   Before the invention of the light bulb, illuminating the world after the sun went down was a messy, arduous, hazardous task. It took a bunch of candles or torches to fully light up a good-sized room, and oil lamps, while fairly effective, tended to leave a residue of soot on anything in their general vicinity. With the invention of light bulb along and as the science of electricity really got going in the mid 1800s, the easy-to-use lighting technology was such an improvement over the old ways that the world never looked back. 
   Currently, the application of illuminating device can be categorized into two fields. One of which is the construction industry, that includes all sorts of lighting systems adapted for private housing units, commercial buildings, and public transportation systems like highway and railway, and so on, so as to achieve objects of comfort, beautification, and safety; another filed is the commercial goods, that includes all sorts of light source adapted for auto lamps, indoor lightings and consumer electronics, etc. As in the Year 2000, the largest demand for illuminating devices lays in the United State of American. Generally, the demand for illuminating devices is growing in a rapid path following the growth of global economy. Nevertheless, as the environmental awareness also grows with the global economy, it is in great demand to have green lighting systems for enhancing environmental protection and energy conservation. 
   Please refer to  FIG. 1 , which is a cross-section of a lighting system disclosed in U.S. Pat. No. 6,234,645, entitled “LED LIGHTING SYSTEM FOR PRODUCING WHIT LIGHT”. As seen in  FIG. 1 , the white lighting system  1  has at least three light-emitting diodes (LEDs)  11  for providing visible light at pre-selected wavelengths. In operation, the white lighting system  1  is provided with at least one fourth light-emitting diode  12  which, emits visible light in a further wavelength region, the maximum of the spectral emission of the fourth light-emitting diode  12  lying in the further wavelength region from 575 to 605 nm. Moreover, the screen  13  is provided on a side facing the LEDs  11 ,  12  with reflection means  14  which diffusely reflect white light so as to effectively blend the light of the LEDs  11 ,  12 . However, the luminaire structure as disclosed in the U.S. Pat. No. 6,234,645 has low luminaire efficacy since it can not guide and scatter the rays emitted from the light source such that the referring lighting system  1  can not control the distribution of luminous intensity, not to mention the enhancement of luminance efficacy of a source of light while glare still can not be avoid. 
   In view of the abovementioned shortcomings, it is require to have an improved illuminating device with high luminaire efficacy for the sake of environmental conservation and also capable of reducing glare. 
   SUMMARY OF THE INVENTION 
   It is the primary object of the invention to provide a reflector with negative focal length adapted for replacing the reflector with positive focal length arranged at the upper area of a common luminaire screen, by which rays emitting from the lamp of the luminaire are reflected and directed to a preferred discharging area so as to enable the rays to be discharge out of the luminaire by large angles for reducing glare, in addition, the height of the luminaire can be reduced. 
   It is another object of the invention to provide a luminaire screen with microstructures arranged thereon for light blending, by which LEDs can be employed as the light sources of a luminaire while the luminaire can have good luminous efficacy. 
   Yet, another object of the invention is to provide a plate having a plurality of microstructures disposed thereon, which is arranged at the lower portion of a luminaire under the light source thereof so as to better diffuse the rays discharging out of the luminaire and thus reducing glare. 
   To achieve the above objects, the present invention provides a luminaire with reflector of negative focal length which comprises a light source and a luminaire screen having a reflector of negative focal length, a side screen and a plate; wherein the rays emitting from the light source is divided by three area: a upward incident area including the rays incident to the reflector of negative focal length as seen in  FIG. 2 ; a sideward incident area including rays incident to the side screen as seen in  FIG. 3 ; and a downward incident area including rays incident to the plate as seen in  FIG. 4 ; and the reflector of negative focal length is capable of reflecting the rays of upward incident area; and the side screen is capable of reflecting the ray of the sideward incident area and the reflected rays of the reflector; and the plate being disposed at the lower portion of the luminaire screen beneath the light source has a plurality of microstructures arranged thereon and is capable of accepting the rays of the downward incident area along with both the reflected rays of the reflector and the side screen so as to diffuse the same for discharging. 
   These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-section of a lighting system disclosed in U.S. Pat. No. 6,234,645. 
       FIG. 2  is a schematic illustration showing a upward incident area of rays emitting from a light source of the present invention. 
       FIG. 3  is a schematic illustration showing a sideward incident area of rays emitting from a light source of the present invention. 
       FIG. 4  is a schematic illustration showing a downward incident area of rays emitting from a light source of the present invention. 
       FIG. 5  shows a luminaire with reflector of negative focal length according to a first embodiment of the invention. 
       FIG. 6  shows a luminaire with reflector of negative focal length according to a second embodiment of the invention. 
       FIG. 7  shows a luminaire with reflector of negative focal length according to a third embodiment of the invention. 
       FIG. 8  is a profile of light intensity generated by a luminaire with reflector of negative focal length of the invention for glare reduction. 
       FIG. 9  is a cross-section of a plate being disposed at the lower portion of the luminaire screen beneath the light source according to the present invention. 
       FIG. 10  is a cross-section showing a plurality of microstructures being arranged on the side screen of a luminaire with reflector of negative focal length according to the present invention. 
       FIG. 11  is a 3D diagram showing a plate with microstructures disposed thereon according to the present invention. 
       FIG. 12  is a 3D diagram showing the side screen with microstructures arranged thereon according to the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   For your esteemed members of reviewing committee to further understand and recognize the fulfilled functions and structural characteristics of the invention, several preferable embodiments cooperating with detailed description are presented as the follows. 
   The present invention improves structure of the screen of a common luminaire and the surface finishing thereof such that the transmission direction of the rays emitting by the luminaire can be changed. Further, the manufacturing cost of the improved luminaire is not aversely affected, but can provide better illumination for exterior lighting, wide-angle lighting and preferred anti-glare function with reduction of the height of the luminaire. 
   Please refer to  FIG. 5 , which shows a luminaire with reflector of negative focal length according to a first embodiment of the invention. In  FIG. 5 , the top of the luminaire screen  20  is a reflector of single negative focal length  51 , such that the cross section of the luminaire screen  20  is a concavity with a side screen  52  connecting to the edge of the reflector  51 . By the luminaire screen  20  of  FIG. 5 , the upward-incident rays emitting from a light source  53  are first reflected to the side screen  52  by the reflector  51 , and then are further reflected such that a plurality of discharging rays  54  are generated. It is noted that the discharging rays  54  are discharge out of the luminaire by large angles for reducing glare. In addition, the height of the luminaire can be reduced. However, the luminaire with reflector of single negative focal length can be further improved. 
   In  FIG. 6 , which is a luminaire with reflector of negative focal length according to a second embodiment of the invention, the top of the luminaire screen is a reflector of multiple negative focal lengths  61 . As seen in  FIG. 6 , the reflector  61  is a combination of a plurality of concentric concavities shrinking downwardly in diameter and the cross section thereof shows that a side screen  62  is connected to the edge of the reflector  61 . By the reflector of multiple negative focal lengths  61 , the upward-incident rays emitting from a light source  63  are reflected to the side screen  62  in a diverse manner. However, the manufacture of the luminaire of  FIG. 6  is costly and complicated such that it is not feasible in reality. 
   For the third embodiment of the invention shown in  FIG. 7 , the reflector with negative focal length  71  similar to that shown is  FIG. 2  is replaced by a planar reflector  72  while a side screen  73  is attached to the edge of the planar reflector  72  similar to that of  FIG. 2 . By using the luminaire screen of  FIG. 7 , the space occupied by the luminaire can be reduced since the volume of the luminaire screen is reduced. 
   For enabling the planar reflector  72  to have the same function as the reflector with negative focal length  71 , a Fresnel lens must be formed on the surface of the planar reflector  72  that is composed of a plurality of microstructures forming a regular formation like sawtooth or an irregular formation. Therefore, by the Fresnel lens formed on the planar reflector  72 , the upward-incident rays emitting from a light source  73  are reflected to the side screen  73  by the reflector  72 , and then are further reflected so as to generate a plurality of discharging rays  75  similar to those shown in  FIG. 5 . 
   Please refer to  FIG. 8 , which a profile of light intensity generated by a luminaire with reflector of negative focal length of the invention for glare reduction. As seen in  FIG. 8 , the outlook of the luminaire screen  70  with planar reflector is simple and compact, and the discharging angle of a luminaire with planar reflector defined by the two arrows  82  is larger than that of a luminaire without planar reflector, which is defined by the two arrows  81 . The luminaire with small discharging angle is pone to generate glare that causes eye-fatigue since the light intensity of the illuminating area of the luminaire directly under the luminaire screen is far larger than that of the off-center area of the luminaire screen. By virtue of this, the use of the planar reflector is intended to enable the light intensity of the illuminating area of the luminaire directly under the luminaire screen to be almost equal to that of the off-center area of the luminaire screen and is reduce to the range acceptable by human eye as illustrated by the profile of light intensity  84  seen in  FIG. 8  such that the phenomenon of eye-fatigue can be avoid after working for long hours under the illumination of the luminaire with planar reflector. 
     FIG. 9  shows a cross-section of a plate  94  being disposed at the lower portion of the luminaire screen beneath the light source  93 , the luminaire screen comprising a planar reflector  91  a side screen  92 . As seen in  FIG. 9 , a plurality of microstructures  941  are disposed on the plate whose formation can be of the shape of sawtooth, or each can be a diffuse point of a shape selected from the group consisting of diamond, sphere, column, and irregular shapes. Moreover, the plural microstructures disposed on the plate are formed by a manner selected from the group consisting of apart from one another by an equal interval and apart from one another by different intervals, so as to regulate the amount of rays discharging from the plate  94 . 
     FIG. 10  shows a cross-section of a plurality of microstructures  1021  being arranged on the side screen  102  of a luminaire with planar reflector  101  according to the present invention, the luminaire further comprising a light source  103  and a plate  104 . As seen in  FIG. 10 , a plurality of microstructures  1021  are disposed on the side screen  102  that each can be a diffuse point of a shape selected from the group consisting of diamond, sphere, column, and irregular shapes. Moreover, the plural microstructures  1021  disposed on the side screen  102  are formed by a manner selected from the group consisting of apart from one another by an equal interval and apart from one another by different intervals, so as to enable the discharging of evenly distributed discharging light  105  for preventing glare as well as reducing the volume of the luminaire. 
   Please refer to  FIG. 11 , which is a 3D diagram showing a plate  114  with microstructures  1141  disposed thereon according to the present invention, the plate  114  being arranged at the lower portion of a luminaire screen consisting of a planar reflector  111  and a side screen and being beneath a light source. As seen in  FIG. 11 , the plate  114  has a plurality of sawtooth-like microstructures disposed thereon and the planar reflector  111  has a plurality of bar-like microstructures  1111  disposed thereon. 
   Please refer to  FIG. 12 , which is a 3D diagram showing a luminaire screen with side screen  122  having a plurality of microstructures  1221  arranged thereon according to the present invention, the luminaire screen further comprising a planar reflector  121  and a plate  124 . As seen in  FIG. 12 , the side screen  122  has a plurality of sawtooth-like microstructures  1221  disposed thereon and the planar reflector  121  has a plurality of bar-like microstructures  1211  disposed thereon. 
   To sum up, the present invention provides a luminaire with reflector of negative focal length which comprises a light source and a luminaire screen having a reflector of negative focal length, a side screen and a plate. Wherein the rays emitting from the light source is divided by three area: a upward incident area including the rays incident to the reflector of negative focal length; a sideward incident area including rays incident to the side screen; and a downward incident area including rays incident to the plate; and the light source is a lighting means selected from the group consisting of a means of single light source, a means of multiple light sources. The reflector of negative focal length is capable of reflecting the rays of upward incident area which can be a planar lens of negative focal length and is selected from the group consisting of a reflector of multiple focal points and a reflector of signal focal point. The side screen is capable of reflecting the ray of the sideward incident area and the reflected rays of the reflector which has a plurality of microstructures arranged on the surface thereof, wherein each microstructures can be a diffuse point of a shape selected from the group consisting of diamond, sphere, column, and irregular shapes and is disposed by a manner selected from the group consisting of apart from one another by an equal interval and apart from one another by different intervals so as to regulate the amount of rays discharging from the side screen. The plate being disposed at the lower portion of the luminaire screen beneath the light source has optionally a plurality of microstructures arranged thereon and is capable of accepting the rays of the downward incident area along with both the reflected rays of the reflector and the side screen so as to diffuse the same for discharging, wherein each microstructures can be a diffuse point of a shape selected from the group consisting of diamond, sphere, column, and irregular shapes and is disposed by a manner selected from the group consisting of apart from one another by an equal interval and apart from one another by different intervals so as to regulate the amount of rays discharging from the plate. Moreover, in a preferred embodiment, a metal reflective surface with reflective index ranged between 0 and 1 is further attached onto the surfaces of both the reflector and the side screen and the plate is made of a material selected from the group consisting of Polycarbonate (PC), Polymethylmethacrylate (PMMA), and Polyethylene Terephthalate (PET). 
   In a preferred embodiment, the reflector of negative focal length of a luminaire screen, which can be a planar reflector, is used for reflecting the rays of the upward incident area and thus to increase the times of the same to be reflected inside the luminaire screen, and eventually, for enabling the luminaire to have larger discharging angle and better distribution of luminance. In addition, the disposition of a plate at the lower portion of the luminaire screen beneath the light source enables the luminaire to have more evenly distributed discharging light so that the phenomenon of glare can be reduced and the luminaire is ensured to have the light intensity profile as shown in  FIG. 8  while the height of the luminaire can be reduced. 
   While the preferred embodiment of the invention has been set forth for the purpose of disclosure, modifications of the disclosed embodiment of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.