Abstract:
A light distribution board having a plurality of light gratings each with multiple focuses, the light distribution board is used on a light outputting surface of a lamp, in which at least a transparent board is provided on at least one of its surfaces with a plurality of light gratings each having multiple focuses, each light grating having multiple focuses is composed of two or more mutually integratedly juxtaposed arciform (concave or convex) lenses to form a convex lens grating having two or more focuses. With this structure, light beams can be uniformly distributed and can avoid the phenomenon of Gauss distribution that makes the area below the lamp especially bright, and can avoid the phenomenon of dazzling of eyes during looking at the light emitting member in the lamp; and except the light beams directly under the lamp, other light beams around the lamp are completely obscured, thus an effect of no optical pollution can be obtained.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a light distribution board having a plurality of light gratings each with multiple focuses; and especially to a light distribution board that can illuminate a district with uniform brightness, tender light beams which are non dazzling under the condition of minimum lose of brightness of a lamp; the light distribution board is suitable applied to a place such as a house, an office, a factory or a road requiring illumination, and can achieve an effect of saving energy as well as avoiding the phenomenon of optical pollution. 
         [0003]    2. Description of the Prior Art 
         [0004]    Illuminating lamps generally are divided in to two kinds including indoor and outdoor lamps; indoor lamps mainly are installed each with a half covering type obscured cover  101  (referring to  FIG. 1A ) having on an inner side thereof a reflective surface  103 ; the light beams of the lamp include, in addition to those directly irradiated from the lamp (light source), quite a large part of light beams being directly reflected from the reflective surface  103  and out of the lamp to a district to be illuminated. These lamps normally are treated by fogging process on the surface of the light source to avoid irradiating of light to eyes to result a phenomenon of making them feel dazzling and dizzy. 
         [0005]    The outdoor lamps are mainly fully covering type covers (referring to  FIG. 1B ) in considering the factor of environment, it is mounted therebeneath with a transparent hood  104 , the hood  104  is also treated by fogging process to avoid the phenomenon of dazzling of eyes during looking at the light source directly. The aforesaid two types have a common defect of losing much brightness by treatment by fogging process, these kinds of conventional lamps generally have the phenomenon of Gauss distribution that brightness of lamps are concentrated at an area exactly below each lamp. 
         [0006]    Light grating boards available presently we know include rhombic gratings and convex lens type gratings, these are shown respectively in  FIGS. 2 and 3 . 
         [0007]    Referring to  FIG. 2  depicting a conventional rhombic grating unit  201  of which the structure is more similar to that of the present invention, the rhombic grating unit  201  has a plane bottom surface  206 , and a top surface having a plurality of saw toothed gratings  202 ,  203 , the rhombic grating  201  is shaped from two straight bevel edges  205 ,  208  being oppositely disposed as mirror images for each other; several incident light beams  204  enter a bevel edge  205  of the saw toothed grating  202  in an identical incident angular direction to result a first time refraction, when the light beams  204  reach the plane surface  206 , they are once more refracted toward a district  209  to be illuminated; similarly, several incident light beams  207  enter a bevel edge  208  of the saw toothed grating  203  in an identical incident angular direction to result a first time refraction, when the light beams  207  reach the plane surface  206 , they are once more refracted toward a district  210  to be illuminated. We can see from the drawing that the light beams after being refracted from those incident light beams in an identical incident angular direction to the bevel edges  205 ,  208  or the plane surface  206  are always parallel to one another, i.e., there is no crossing and diffusing effect, the light beams arriving at the districts to be illuminated form partial gathering light beams, and they are unable to get an effect of uniformly distributing. 
         [0008]    Referring to  FIG. 3  which is depicted another conventional convex lens grating unit  301  of which the structure is also more similar to that of the present invention, the convex lens grating unit  301  has a plane bottom surface  305 , and a top surface having a plurality of convex lens gratings  302 ,  303 , the convex lens grating unit  301  is composed of the two convex lens gratings  302 ,  303  of different curvatures. Several incident light beams  304  enter the convex lens  302  in an identical incident angular direction to result a first time refraction, when the light beams  304  reach the plane surface  305 , they are once more refracted toward a district  307  to be illuminated; similarly, several incident light beams  306  enter the convex lens grating  303  in an identical incident angular direction to result a first time refraction, when the light beams  306  reach the plane surface  305 , they are once more refracted toward a district  308  to be illuminated. We can see from the drawing that the light beams after being irradiated to the two convex lens gratings  302 ,  303  in an identical incident angular direction will create refractions in different angular directions, wherein the convex lens grating  302  of a smaller curvature has a longer focus, the light beams after being refracted from the convex lens grating  302  cross at the focus, they form a narrower illuminated range at the district  307 ; the other convex lens grating  303  of a larger curvature has a shorter focus, the light beams after being refracted from the convex lens grating  303  cross at the focus, they form a wider illuminated range at the district  308 . 
         [0009]    If the convex lens grating unit  301  is applied to a place for light distribution, at least two defects as list below will be induced: firstly, all light beams will gather at an area exactly below the convex lens grating unit  301 , their distance of irradiation is short and they are unable to get an effect of having a wide illuminated range; and secondly, the light beams are highly overlapped with one another and are subjected to resulting the phenomenon of Gauss distribution, and are unable to get an effect of uniformly distributing. 
         [0010]    In view of the above, the transparent hood  104  is unable to get an effect of the desired light distribution by using a conventional light grating. 
       SUMMARY OF THE INVENTION 
       [0011]    In order to get rid of the defects of the conventional lamps, the present invention provided a light distribution board having a plurality of light gratings each with multiple focuses, the light distribution board can be mounted at a light outputting surface of a conventional lamp to control the refraction angular directions of most of the light beams of the lamp, so that the light beams can irradiate a predetermined district to be illuminated to get an effect of uniformly distributing. At least a transparent board is provided on its top surface with a plurality of light gratings each having multiple focuses, each light grating having multiple focuses is composed of two or more mutually integratedly juxtaposed arciform (concave or convex) lenses to form a light grating having two or more focuses; these light gratings with multiple focuses are strip like light gratings; the top surface is a light receiving surface of the lamp. The bottom surface of the transparent board can be a plane surface, an arciform surface or a surface formed thereon a plurality of normal convex lenses, and the bottom surface is an illuminating surface of the lamp. With such a structure, light beams can be uniformly distributed and can avoid the phenomenon of Gauss distribution that makes the area below the lamp especially bright, and can avoid the phenomenon of dazzling of eyes during looking at the light emitting member in the lamp, and the light beams become more tender under the condition that lose of brightness is minimum. 
         [0012]    Moreover, the light distribution board provided in the present invention can be formed on a top surface of a transparent board a plurality of light gratings each having multiple focuses, each light grating having multiple focuses is composed of two or more mutually integratedly juxtaposed arciform (concave or convex) lenses to form a light grating having two or more focuses; these light gratings with multiple focuses are annular light gratings; the top surface is a light receiving surface of the lamp. The bottom surface of the transparent board can be a plane surface, an arciform surface or a surface formed thereon a plurality of normal convex lenses, and the bottom surface is an illuminating surface of the lamp. 
         [0013]    Further, the light distribution board provided in the present invention can be formed on a top surface of a transparent board a plurality of light gratings each having multiple focuses, each light grating having multiple focuses is composed of two or more mutually integratedly juxtaposed convex lenses to form a light grating having two or more focuses; these light gratings with multiple focuses are light gratings in shapes of clouds; the top surface is a light receiving surface of the lamp. The bottom surface of the transparent board can be a plane surface, an arciform surface or a surface formed thereon a plurality of normal convex lenses, and the bottom surface is an illuminating surface of the lamp. 
         [0014]    And more, the light distribution board provided in the present invention can be formed on a top surface of a transparent board a plurality of light gratings each having multiple focuses, each light grating having multiple focuses is composed of two or more mutually integratedly juxtaposed arciform (concave or convex) lenses to form a light grating having two or more focuses; these light gratings with multiple focuses are light gratings are granular being arranged in lines; the top surface is a light receiving surface of the lamp. The bottom surface of the transparent board can be a plane surface, an arciform surface or a surface formed thereon a plurality of normal convex lenses, and the bottom surface is an illuminating surface of the lamp. 
         [0015]    And more, the light distribution board provided in the present invention can be formed on a top surface of a transparent board a plurality of light gratings each having multiple focuses, each light grating having multiple focuses is composed of two or more mutually integratedly juxtaposed arciform (concave or convex) lenses to form a light grating having two or more focuses; these light gratings with multiple focuses are light gratings in shapes of granules being arranged in annular shapes; the top surface is a light receiving surface of the lamp. The bottom surface of the transparent board can be a plane surface, an arciform surface or a surface formed thereon a plurality of normal convex lenses, and the bottom surface is an illuminating surface of the lamp. 
         [0016]    And further more, the light distribution board provided in the present invention can be formed on a top surface of a transparent board a plurality of light gratings each having multiple focuses, each light grating having multiple focuses is composed of two or more mutually integratedly juxtaposed arciform (concave or convex) lenses to form a light grating having two or more focuses; these light gratings with multiple focuses are light gratings in shapes of granules mutually overlapping, being arranged in lines or in annular shapes; the top surface is a light receiving surface of the lamp. The bottom surface of the transparent board can be a plane surface, an arciform surface or a surface formed thereon a plurality of normal convex lenses, and the bottom surface is an illuminating surface of the lamp. 
         [0017]    In a light distribution board provided in the present invention, curvature and inclination angle of each arciform (concave or convex) lens of a light grating having multiple focuses are changed in pursuance of the angles of refraction of the incident light beams through the arciform (concave or convex) lens surfaces. While curvature of every normal convex lens and the inter-lens distance between every two normal convex lenses are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. Thereby light beams in a lamp can be refracted toward a small area of the district to be illuminated, thus light beams can be uniformly distributed and can avoid the phenomenon of Gauss distribution that makes the area below the lamp especially bright. 
         [0018]    The light distribution board provided in the present invention can be further improved, namely, partial areas of the bottom surface of the transparent board can be formed a plurality of strip like or annularly arranged light gratings comprised of normal convex lenses; and partial areas can be formed a plurality of convex lens gratings with multiple focuses. With such a structure, a wider illuminated range can be provided, light beams can be uniformly distributed, the phenomenon of dazzling of eyes during looking at the light emitting member in the lamp and the phenomenon of optical pollution can be avoided. 
         [0019]    The present invention will be apparent in its structure and principle after reading the detailed description of the preferred embodiment thereof in reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1A  is a schematic sectional view of a conventional half covering type illumination lamp; 
           [0021]      FIG. 1B  is a schematic sectional view of a conventional fully covering type illumination lamp; 
           [0022]      FIG. 2  is a schematic view showing the light beam progressing of a conventional rhombic grating structure; 
           [0023]      FIG. 3  is a schematic view showing the light beam progressing of a conventional convex lens grating; 
           [0024]      FIG. 4  is a side view showing a light grating having multiple focuses and composed of two mutually integratedly juxtaposed convex lenses forming the structure of a strip like, cloud shaped or annular light grating having multiple focuses of the light distribution board of the present invention; 
           [0025]      FIG. 4A  is a top view of the light grating of  FIG. 4 ; 
           [0026]      FIG. 5  is a side view showing a light grating having multiple focuses and composed of three mutually integratedly juxtaposed convex lenses forming the structure of a strip like, cloud shaped or annular light grating having multiple focuses of the light distribution board of the present invention; 
           [0027]      FIG. 5A  is a top view of the light grating of  FIG. 5 ; 
           [0028]      FIG. 6  is a side view showing a light grating having multiple focuses and composed of four mutually integratedly juxtaposed convex lenses forming the structure of a strip like, cloud shaped or annular light grating having multiple focuses of the light distribution board of the present invention; 
           [0029]      FIG. 6A  is a top view of the light grating of  FIG. 6 ; 
           [0030]      FIG. 7  is a side view showing a light grating having multiple focuses and composed of two mutually integratedly juxtaposed convex lenses forming a light grating having two focuses which is a granule shaped light grating having multiple focuses on the light distribution board of the present invention; 
           [0031]      FIG. 7A  is a top view of the light grating of  FIG. 7 ; 
           [0032]      FIG. 8  is a side view showing a light grating having multiple focuses and composed of three mutually integratedly juxtaposed convex lenses forming a light grating having three focuses which is a granule shaped light grating having multiple focuses on the light distribution board of the present invention; 
           [0033]      FIG. 8A  is a top view of the light grating of  FIG. 8 ; 
           [0034]      FIG. 9  is a side view showing a light grating having multiple focuses and composed of four mutually integratedly juxtaposed convex lenses forming a light grating having four focuses which is a granule shaped light grating having multiple focuses on the light distribution board of the present invention; 
           [0035]      FIG. 9A  is a top view of the light grating of  FIG. 9 ; 
           [0036]      FIG. 10  is an enlarged schematic view showing the structure of a plurality of light gratings having multiple focuses and respectively pointing out the focuses of a plurality of mutually integratedly juxtaposed convex lenses in partial sectional view of a light distribution board of the present invention; 
           [0037]      FIG. 11  is a schematic view showing a design wherein a plurality of light gratings having multiple focuses of the structure of the present invention is to control irradiating of light beams to a predetermined district; 
           [0038]      FIGS. 12 ,  12 A and  12 B are plane views of a first embodiment of the present invention; 
           [0039]      FIGS. 13 ,  13 A and  13 B are plane views of a second embodiment of the present invention; 
           [0040]      FIGS. 14 ,  14 A and  14 B are plane views of a third embodiment of the present invention; 
           [0041]      FIGS. 15 ,  15 A and  15 B are plane views of a fourth embodiment of the present invention; 
           [0042]      FIGS. 16 ,  16 A and  16 B are plane views of a fifth embodiment of the present invention; 
           [0043]      FIGS. 17 and 17A  are plane views of a sixth embodiment of the present invention; 
           [0044]      FIGS. 18 and 18A  are plane views of a seventh embodiment of the present invention; 
           [0045]      FIGS. 19 ,  19 A and  19 B are plane views of an eighth embodiment of the present invention; 
           [0046]      FIGS. 20 ,  20 A and  20 B are plane views of a ninth embodiment of the present invention; 
           [0047]      FIGS. 21 and 21A  are plane views of a tenth embodiment of the present invention; 
           [0048]      FIGS. 22 and 22A  are plane views of an eleventh embodiment of the present invention; 
           [0049]      FIGS. 23 and 23A  are plane views of a twelfth embodiment of the present invention; 
           [0050]      FIGS. 24 and 24A  are plane views of a thirteenth embodiment of the present invention; 
           [0051]      FIGS. 25 and 25A  are plane views of a fourteenth embodiment of the present invention; 
           [0052]      FIGS. 26 and 26A  are plane views of a fifteenth embodiment of the present invention; 
           [0053]      FIGS. 27 and 27A  are plane views of a sixteenth embodiment of the present invention; 
           [0054]      FIG. 28  is a sectional view showing an embodiment of which at least a side of a transparent board of the present invention is used to form a light distribution board having a plurality of light gratings each with multiple focuses and is applied to a lamp; 
           [0055]      FIG. 29  is a sectional view showing another embodiment of which at least a side of a transparent board of the present invention is used to form a light distribution board having a plurality of light gratings each with multiple focuses and is applied to a lamp; 
           [0056]      FIG. 30  is a side view showing a light grating having multiple focuses and composed of two mutually integratedly juxtaposed concave lenses forming the structure of a strip like, cloud shaped or annular light grating having multiple focuses of the light distribution board of the present invention; 
           [0057]      FIG. 30A  is a top view of the light grating of  FIG. 30 ; 
           [0058]      FIG. 31  is a side view showing a light grating having multiple focuses and composed of three mutually integratedly juxtaposed concave lenses forming the structure of a strip like, cloud shaped or annular light grating having multiple focuses of the light distribution board of the present invention; 
           [0059]      FIG. 31A  is a top view of the light grating of  FIG. 31 ; 
           [0060]      FIG. 32  is a side view showing a light grating having multiple focuses and composed of four mutually integratedly juxtaposed concave lenses forming the structure of a strip like, cloud shaped or annular light grating having multiple focuses of the light distribution board of the present invention; 
           [0061]      FIG. 32A  is a top view of the light grating of  FIG. 32 ; 
           [0062]      FIG. 33  is a side view showing a light grating having multiple focuses and composed of two arciform (one convex and one convex concave) mutually integratedly juxtaposed lenses forming the structure of a strip like, cloud shaped or annular light grating having multiple focuses of the light distribution board of the present invention; 
           [0063]      FIG. 33A  is a top view of the light grating of  FIG. 33 ; 
           [0064]      FIG. 34  is a side view showing a light grating having multiple focuses and composed of three arciform (one convex and two concave) mutually integratedly juxtaposed lenses forming the structure of a strip like, cloud shaped or annular light grating having multiple focuses of the light distribution board of the present invention; 
           [0065]      FIG. 34A  is a top view of the light grating of  FIG. 34 ; 
           [0066]      FIG. 35  is a side view showing a light grating having multiple focuses and composed of four arciform (two convex and two concave) mutually integratedly juxtaposed lenses forming the structure of a strip like, cloud shaped or annular light grating having multiple focuses of the light distribution board of the present invention; 
           [0067]      FIG. 35A  is a top view of the light grating of  FIG. 35 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0068]    The present invention relates to a light distribution board having a plurality of light gratings each with multiple focuses, in which at least a transparent board is used to form the light distribution board as an illuminating cover for a lamp. The transparent board can be in the shape of rectangular, circle, elliptical or strange shape; the material for the transparent board can be transparent plastics, transparent glass or some other transparent material. The transparent board is formed on at least one side thereof a plurality of light gratings having multiple focuses in strip, annular, cloud or granular shape, each of the light gratings having multiple focuses is composed of two or more mutually integratedly juxtaposed arciform (concave or convex) lenses to form a convex lens grating having two or more focuses, curvature and inclination angle of each arciform (concave or convex) lens are changed in pursuance of the angles of refraction of the incident light beams through the convex lens surfaces. 
         [0069]    In the following embodiments, the light gratings having multiple focuses in strip, annular, cloud or granular shapes formed from the transparent boards of the present invention are chosen from the following various structures:
       1. Referring to  FIGS. 4 and 4A , in the drawings, a light grating  401  having multiple focuses is composed of two mutually integratedly juxtaposed convex lenses  402  and  403 , and there are two surfaces  404 ,  405  which are vertical surfaces of the front and the rear sides respectively of the light grating  401 , and a bottom surface  406  of the light grating  401  having multiple focuses is a plane surface.   2. Referring to  FIGS. 5 and 5A , in the drawings, a light grating  501  having multiple focuses is composed of three mutually integratedly juxtaposed convex lenses  502 ,  503  and  504 , and there are two surfaces  505  and  506  which are vertical surfaces of the front and the rear sides respectively of the light grating  501 , and a bottom surface  507  of the light grating  501  having multiple focuses is a plane surface.   3. Referring to  FIGS. 6 and 6A , in the drawings, a light grating  601  having multiple focuses is composed of four mutually integratedly juxtaposed convex lenses  602 ,  603 ,  604  and  605 , and there are two surfaces  606 ,  607  which are vertical surfaces of the front and the rear sides respectively of the light grating  601 , and a bottom surface  608  of the light grating  501  having multiple focuses is a plane surface.       
 
         [0073]    By virtue that there are many kinds of light grating structures composed of mutually integratedly juxtaposed convex lenses, here we summarily list the above three kinds of composed structures, generally speaking, a convex lens grating having two or more focuses and composed of two or more mutually integratedly juxtaposed arciform (concave or convex) lenses in strip, cloud, or annular shapes all fall in the range of the light gratings with multiple focuses formed from the transparent boards of the present invention. 
         [0074]    In the following embodiments, those structures of light gratings with multiple focuses formed from the transparent board of the present invention in shapes of granules are chosen from the followings:
       1. Referring to  FIGS. 7 and 7A , in the drawings, a light grating  701  having multiple focuses is composed of two mutually integratedly juxtaposed convex lenses  702  and  703  to form a convex lens grating having two focuses, and a bottom surface  704  of the light grating  701  having multiple focuses is a plane surface.   2. Referring to  FIGS. 8 and 8A , in the drawings, a light grating  801  having multiple focuses is composed of three mutually integratedly juxtaposed convex lenses  802 ,  803  and  804  to form a convex lens grating having three focuses, and a bottom surface  805  of the light grating  801  having multiple focuses is a plane surface.   3. Referring to  FIGS. 9 and 9A , in the drawings, a light grating  901  having multiple focuses is composed of four mutually integratedly juxtaposed convex lenses  902 ,  903 ,  904  and  905  to form a convex lens grating having four focuses, and a bottom surface  906  of the light grating  901  having multiple focuses is a plane surface.       
 
         [0078]    By virtue that there are many kinds of light grating structures composed of mutually integratedly juxtaposed convex lenses, here we summarily list the above three kinds of composed structures, generally speaking, a convex lens grating having two or more focuses and composed of two or more mutually integratedly juxtaposed convex lenses in granular shapes all fall in the range of the light gratings with multiple focuses formed from the transparent boards of the present invention. 
         [0079]    Referring to  FIG. 10  which is an enlarged schematic view (such as of the embodiment shown in  FIG. 13A  or  14 A) showing the structure of a plurality of light gratings having multiple focuses in partial sectional view of the present invention; in the drawings, the bottom surface  1002  of a transparent board  1001  is a plane surface, and the top surface of the transparent board  1001  is formed thereon a plurality of light gratings (having multiple focuses)  1003 ,  1004 ,  1005 ,  1006 ,  1007  and  1008 , wherein the two light gratings  1003 ,  1007  having multiple focuses are respectively composed of two mutually integratedly juxtaposed convex lenses of same curvature and inclination angle; one convex lens  1009  of the light grating  1003  having multiple focuses has a focus  1026 , the other convex lens  1010  of the light grating  1003  has a focus  1025 ; the light gratings  1004 ,  1006  are respectively composed of two mutually integratedly juxtaposed convex lenses of same curvature but different inclination angles; one convex lens  1011  of the light grating  1004  having multiple focuses has a focus  1019 , the other convex lens  1012  of the light grating  1004  has a focus  1018 ; one convex lens  1013  of the light grating  1006  having multiple focuses has a focus  1021 , the other convex lens  1014  of the light grating  1006  has a focus  1020 ; the light grating  1005  is composed of two mutually integratedly juxtaposed convex lenses of different curvatures, of which one convex lens  1016  has a focus  1024 , the other convex lens  1015  has a focus  1023 ; the remaining convex lens  1017  has a focus  1022 . 
         [0080]    Referring to  FIG. 11  which shows a design wherein a plurality of light gratings having multiple focuses of the structure of the present invention is in controlling irradiating of light beams to a predetermined district; in the drawings, the bottom surface  1102  of a transparent board  1101  is a plane surface, and the top surface of the transparent board  1101  is formed thereon a plurality of light gratings (having multiple focuses)  1103 ,  1108  and  1113 , wherein the light grating having multiple focuses  1103  is composed of two mutually integratedly juxtaposed convex lenses  1104 ,  1105  of same curvature and inclination angle; when several light beams  1106  enter the convex lens  1105  of the light grating  1103  in an identical angular direction and create a first time refraction, and when the light beams  1106  reach the plane surface  1102 , they are once more refracted down and rightwards toward a district  1107  to be illuminated; the light grating  1108  is composed of two mutually integratedly juxtaposed convex lenses  1109 ,  1110  of same curvature but different inclination angles; when several light beams  1111  enter the convex lens  1110  of the light grating  1108  in an identical angular direction and create a first time refraction, and when the light beams  1111  reach the plane surface  1102 , they are once more refracted down and rightwards toward a district  1112  to be illuminated; the light grating  1113  is composed of three mutually integratedly juxtaposed convex lenses  1114 ,  1115  and  1116  of different curvatures; when several light beams  1117  enter the convex lens  1114  of the light gratings  1113  in an identical angular direction and create a first time refraction, and when the light beams  1111  reach the plane surface  1102 , they are once more refracted down and leftwards toward a district  1118  to be illuminated; when several light beams  1119  enter the convex lens  1115  of the light gratings  1113  in an identical angular direction and create a first time refraction, and when the light beams  1119  reach the plane surface  1102 , they are once more refracted down and leftwards toward a district  1120  to be illuminated. 
         [0081]    We can see from the drawing that the light beams after being irradiated to the two convex lenses  1105 ,  1110  of same curvature but different inclination angles will create refractions in quite different angular directions; wherein the convex lens  1105  has a larger inclination angle, it will render the incident light beams to go in a larger angle of refraction down and rightwards of a lamp, and controls irradiating of the light beams to a district farer from and under the lamp, this creates an effect of having a wider range of illumination; the convex lens  1110  has a smaller inclination angle, it will render the incident light beams to go in a smaller angle of refraction down and rightwards of a lamp, and controls irradiating of the light beams to a district nearer from and under the lamp, this creates an effect of having a narrower range of illumination. 
         [0082]    We can also see from the drawing that the light beams after being irradiated to the two convex lenses  1114 ,  1115  of different curvatures will result quite different ranges of illumination; wherein the convex lens  1115  has a larger curvature, it will render the incident light beams to induce crossing effect at a focus with a shorter distance, and controls irradiating of the light beams to a district to create an effect of having a wider range of illumination; the convex lens  1114  has a smaller curvature as comparing with the convex lens  1115 , it will render the incident light beams to induce crossing effect at a focus with a longer distance, and controls irradiating of the light beams to a district to create an effect of having a narrower range of illumination. 
         [0083]    We can see from the above stated that, when the curvature and tilting angle of each convex lens of a plurality of light gratings having multiple focuses are suitably controlled, the effects of having a wider illuminated range and uniform distribution of light beams at the district to be illuminated can be obtained. And we can know thereby, the present invention can have better distribution of light beams than the conventional case using the rhombic grating unit  201  in  FIG. 2  and the convex lens grating unit  301  in  FIG. 3 . 
         [0084]    The followings are multiple examples for describing the light distribution boards of the present invention: 
         [0085]    Referring to  FIGS. 12 ,  12 A and  12 B which are plane views of a first embodiment of light distribution board of the present invention, in the drawings, a bottom surface  1202  of a transparent board  1201  is a plane surface, and a top surface of the transparent board  1201  is formed thereon a plurality of strip like light gratings  1203  each having multiple focuses. These strip like light gratings  1203  having multiple focuses form the light grating structure same as that shown in  FIG. 10 , the principle of designing the curvature and tilting angle of each convex lens of the light gratings having multiple focuses is same as that stated for  FIG. 11 . 
         [0086]    Referring to  FIGS. 13 ,  13 A and  13 B which are plane views of a second embodiment of light distribution board of the present invention, in the drawings, a bottom surface  1302  of a transparent board  1301  is a plane surface, and a top surface of the transparent board  1301  is formed thereon a plurality of annular light gratings  1303  having multiple focuses. These annular light gratings  1303  having multiple focuses form the light grating structure same as that shown in  FIG. 10 , the principle of designing the curvature and tilting angle of each convex lens of the light gratings having multiple focuses is same as that stated for  FIG. 11 . 
         [0087]    Referring to  FIGS. 14 ,  14 A and  14 B which are plane views of a third embodiment of light distribution board of the present invention, in the drawings, a bottom surface  1402  of a transparent board  1401  is a plane surface, and a top surface of the transparent board  1401  is formed thereon a plurality of cloud shaped light gratings  1403  having multiple focuses. These cloud shaped light gratings  1403  having multiple focuses form the light grating structure same as that shown in  FIG. 10 , the principle of designing the curvature and tilting angle of each convex lens of the light gratings having multiple focuses is same as that stated for  FIG. 11 . 
         [0088]    Referring to  FIGS. 15 ,  15 A and  15 B which are plane views of a fourth embodiment of light distribution board of the present invention, in the drawings, a bottom surface  1502  of a transparent board  1501  is a plane surface, and a top surface of the transparent board  1501  is formed thereon a plurality of annular light gratings  1503  having multiple focuses. These annular light gratings  1503  having multiple focuses are arranged in steps. And these annular light gratings  1503  having multiple focuses form the light grating structure same as that shown in  FIG. 10 , the principle of designing the curvature and tilting angle of each convex lens of the light gratings having multiple focuses is same as that stated for  FIG. 11 . 
         [0089]    Referring to  FIGS. 16 ,  16 A and  16 B which are plane views of a fifth embodiment of light distribution board of the present invention, in the drawings, a bottom surface  1602  of a transparent board  1601  is an arciform surface, and a top surface of the transparent board  1601  is formed thereon a plurality of annular light gratings  1603  having multiple focuses. These annular light gratings  1603  having multiple focuses are arranged in steps. And these annular light gratings  1603  having multiple focuses form the light grating structure same as that shown in  FIG. 10 , the principle of designing the curvature and tilting angle of each convex lens of the light gratings having multiple focuses is same as that stated for  FIG. 11 . 
         [0090]    Referring to  FIGS. 17 and 17A  which are plane views of a sixth embodiment of light distribution board of the present invention, in the drawings, a bottom surface  1702  of a transparent board  1701  is a plane surface, and a top surface of the transparent board  1701  is formed at a central area thereon a plurality of non-concentric annular light gratings  1703 ,  1704 ,  1705  and  1706  all having multiple focuses. These annular light gratings  1703 ,  1704 ,  1705  and  1706  having multiple focuses form the light grating structure same as that shown in  FIG. 10 , the principle of designing the curvature and tilting angle of each convex lens of the light gratings having multiple focuses is same as that stated for  FIG. 11 . 
         [0091]    Referring to  FIGS. 18 and 18A  which are plane views of a seventh embodiment of light distribution board of the present invention, in the drawings, a bottom surface  1802  of a transparent board  1801  is a plane surface, and a top surface of the transparent board  1801  is formed at a central area thereon a plurality of non-concentric annular light gratings  1812  and a plurality of partially annular light gratings  1803 ,  1804 ,  1805 ,  1806 ,  1807 ,  1808 ,  1809  and  1810  all having multiple focuses. These annular light gratings  1803 ,  1804 ,  1805 ,  1806 ,  1807 ,  1808 ,  1809  and  1810  having multiple focuses form the light grating structure same as that shown in  FIG. 10 , the principle of designing the curvature and tilting angle of each convex lens of the light gratings having multiple focuses is same as that stated for  FIG. 11 . 
         [0092]    Referring to  FIGS. 19 ,  19 A and  19 B which are plane views of a eighth embodiment of light distribution board of the present invention, in the drawings, a bottom surface of a transparent board  1901  is formed thereon a plurality of normal convex lenses  1902 , and a top surface of the transparent board  1901  is formed thereon a plurality of strip like light gratings  1903  having multiple focuses. These strip like light gratings  1903  having multiple focuses of the transparent board  1901  form the light grating structure same as that shown in  FIG. 10 , the principle of designing the curvature and tilting angle of each convex lens of the light gratings having multiple focuses is same as that stated for  FIG. 11 , the principle of designing the curvature of each of the convex lenses  1902  is same as that stated for  FIG. 3 . 
         [0093]    Referring to  FIGS. 20 ,  20 A and  20 B which are plane views of a ninth embodiment of light distribution board of the present invention, in the drawings, a bottom surface  1202  of a transparent board  2001  is formed thereon a plurality of normal convex lenses  2002 , and a top surface of the transparent board  2001  is formed thereon a plurality of annular light gratings  2003  having multiple focuses. These annular light gratings  2003  having multiple focuses of the transparent board  2001  form the light grating structure same as that shown in  FIG. 10 , the principle of designing the curvature and tilting angle of each convex lens of the light gratings having multiple focuses is same as that stated for  FIG. 11 , the principle of designing the curvature of each of the normal convex lenses  2002  is same as that stated for  FIG. 3 . 
         [0094]    Referring to  FIGS. 21 , and  21 A which are plane views of a tenth embodiment of light distribution board of the present invention, in the drawings, a bottom surface  2102  of a transparent board  2101  is a plane surface, and a top surface of the transparent board  2101  is formed thereon a plurality of light gratings  2103  respectively with multiple granules each including a plurality of convex lenses and each having multiple focuses. These light gratings  2103  with granules having multiple focuses in this drawing are composed each of a plurality of convex lens groups respectively with four mutually integratedly juxtaposed convex lenses that form a light grating having four focuses being arranged in lines. The principle of designing the curvature and tilting angle of each convex lens of the granular light gratings having multiple focuses of the transparent board  2101  is same as that stated for  FIG. 11 . 
         [0095]    Referring to  FIGS. 22 , and  22 A which are plane views of an eleventh embodiment of light distribution board of the present invention, in the drawings, a bottom surface  2202  of a transparent board  2201  is a plane surface, and a top surface of the transparent board  2201  is formed thereon a plurality of granular light gratings  2203  respectively with multiple granules each including a plurality of convex lenses and each having multiple focuses. These light gratings  2203  with granules having multiple focuses in this drawing are composed each of a plurality of convex lens groups respectively with four mutually integratedly juxtaposed convex lenses that form a light grating having four focuses being arranged in lines and overlapped with one another. The principle of designing the curvature and tilting angle of each convex lens of the granular light gratings having multiple focuses of the transparent board  2201  is same as that stated for  FIG. 11 . 
         [0096]    Referring to  FIGS. 23 , and  23 A which are plane views of a twelfth embodiment of light distribution board of the present invention, in the drawings, a bottom surface  2302  of a transparent board  2301  is a plane surface, and a top surface of the transparent board  2301  is formed thereon a plurality of granular light gratings  2303  respectively with multiple granules each including a plurality of convex lenses and each having multiple focuses. These light gratings  2303  with granules having multiple focuses in this drawing are composed each of a plurality of convex lens groups respectively with four mutually integratedly juxtaposed convex lenses that form a light grating having four focuses being arranged in annular shapes. The principle of designing the curvature and tilting angle of each convex lens of the granular light gratings having multiple focuses of the transparent board  2301  is same as that stated for  FIG. 11 . 
         [0097]    Referring to  FIGS. 24 , and  24 A which are plane views of a thirteenth embodiment of light distribution board of the present invention, in the drawings, a bottom surface  2402  of a transparent board  2401  is a plane surface, and a top surface of the transparent board  2401  is formed thereon a plurality of granular light gratings  2403  respectively with multiple granules each including a plurality of convex lenses and each having multiple focuses. These light gratings  2403  with granules having multiple focuses in this drawing are composed each of a plurality of convex lens groups respectively with four mutually integratedly juxtaposed convex lenses that form a light grating having four focuses being arranged in annular shapes and overlapped with one another. The principle of designing the curvature and tilting angle of each convex lens of the granular light gratings having multiple focuses of the transparent board  2401  is same as that stated for  FIG. 11 . 
         [0098]    Referring to  FIGS. 25 , and  25 A which are plane views of a fourteenth embodiment of light distribution board of the present invention, in the drawings, a top surface of the transparent board  2501  is formed thereon a plurality of granular light gratings  2503  respectively with multiple granules each including a plurality of convex lenses and each having multiple focuses. These light gratings  2503  with granules having multiple focuses in this drawing are composed each of a plurality of convex lens groups respectively with four mutually integratedly juxtaposed lenses that form a light grating having four focuses being arranged in lines; and a bottom surface of the transparent board  2501  is formed thereon a plurality of normal convex lenses. The principle of designing the curvature and tilting angle of each convex lens of the granular light gratings having multiple focuses of the transparent board  2501  is same as that stated for  FIG. 11 , the principle of designing the curvature of each of the normal convex lenses is same as that stated for  FIG. 3 . 
         [0099]    Referring to  FIGS. 26 , and  26 A which are plane views of a fifteenth embodiment of light distribution board of the present invention, in the drawings, a top surface of the transparent board  2601  is formed thereon a plurality of granular light gratings  2603  respectively with multiple granules each including a plurality of convex lenses and each having multiple focuses. These light gratings  2603  with granules having multiple focuses in this drawing are composed each of a plurality of convex lens groups respectively with four mutually integratedly juxtaposed convex lenses that form a light grating having four focuses being arranged in annular shapes; and a bottom surface of the transparent board  2601  is formed thereon a plurality of normal convex lenses. The principle of designing the curvature and tilting angle of each convex lens of the granular light gratings having multiple focuses of the transparent board  2601  is same as that stated for  FIG. 11 , the principle of designing the curvature of each of the normal convex lenses is same as that stated for  FIG. 3 . 
         [0100]    Referring to  FIGS. 27 , and  27 A which are plane views of a sixteenth embodiment of light distribution board of the present invention, in the drawings, a top surface of a double-layer light distribution board  2701  is composed of two transparent boards  2702 ,  2703 , each of the two transparent boards  2702 ,  2703  can belong to any of the above fifteen kinds of embodiments of light distribution boards and can be overlapped with each other. In the drawings, the two transparent boards as shown here are both the transparent boards for the annular light gratings having multiple focuses as stated in the second embodiment, with such a structure, light beams can get maximum angles of refraction after many times of refraction. 
         [0101]    Referring to  FIG. 28  which shows an embodiment of which at least a side of a transparent board of the present invention is used to form a light distribution board with a plurality of light gratings having multiple focuses and is applied to a lamp, in which a light distribution board randomly chosen from any of the above first to fifteenth embodiments is movably mounted at a district to be illuminated below the conventional half covering type obscured cover  101 ; in this drawing, a light distribution board  2801  as that of the second embodiment of the present invention is used for an example, a top surface of the light distribution board  2801  is formed thereon a plurality of annular light gratings having multiple focuses and faces to a light source  102  to be a light receiving surface, a bottom surface  2802  of the light distribution board  2801  is a plane surface as a light outputting surface. 
         [0102]    When light beams  2805  enter a convex lens  2806  of the light grating  2812  of the light distribution board  2801  to create a first time refraction, and when the light beams  2805  reach the plane surface  2802 , they are once more refracted down and rightwards toward a district to be illuminated. A light beam  2807  enters a convex lens  2808  of a light grating  2813  of the light distribution board  2801  to create a first time refraction, and when the light beam  2807  reaches the plane surface  2802 , it is once more refracted down and leftwards and enters the district to be illuminated. A light beam  2809  enters a convex lens  2810  of a light grating  2814  of the light distribution board  2801  after being reflected by a reflective surface  103  to create a first time refraction, and when the light beam  2809  reaches the plane surface  2802 , it is once more refracted down and leftwards and enters the district to be illuminated. A light beam  2803  enters a convex lens  2804  of a light grating  2811  of the light distribution board  2801  after being reflected by the reflective surface  103  to create a first time refraction, and when the light beam  2803  reaches the plane surface  2802 , it is once more refracted down and rightwards and enters the district to be illuminated. The light distribution board  2801  surely can control illumination of a specific district to be illuminated by most of the light beams from a lamp, and the effects of having a wider illuminated range and uniform distribution of brightness of light beams at the district to be illuminated can thus be obtained. 
         [0103]    Referring to  FIG. 29  which shows another embodiment of which at least a side of a transparent board of the present invention is used to form a light distribution board with a plurality of light gratings having multiple focuses and is applied to a lamp, in which a light distribution board  2901  of the above sixteenth embodiment is movably mounted at a district to be illuminated below the conventional half covering type obscured cover  101 ; in this drawing, the light distribution board  2901  is formed from two transparent boards  2902 ,  2903  having a plurality of light gratings each with multiple focuses. 
         [0104]    In the following embodiments, the light gratings having multiple focuses in strip, annular, cloud or granular shapes formed from the transparent boards of the present invention can also be chosen from the following various structures:
       1. Referring to  FIGS. 30 and 30A , in the drawings, a light grating  3001  having multiple focuses is composed of two mutually integratedly juxtaposed concace lenses  3002  and  3003 , and there are two surfaces  3004 ,  3005  which are vertical surfaces of the front and the rear sides respectively, and a bottom surface  3006  of the light grating  3001  having multiple focuses is a plane surface.   2. Referring to  FIGS. 31 and 31A , in the drawings, a light grating  3101  having multiple focuses is composed of three mutually integratedly juxtaposed concave lenses  3102 ,  3103  and  3104 , and there are two surfaces,  3105  and  3106  which are vertical surfaces of the front and the rear sides respectively, and a bottom surface  3107  of the light grating  3101  having multiple focuses is a plane surface.   3. Referring to  FIGS. 32 and 32A , in the drawings, a light grating  3201  having multiple focuses is composed of four mutually integratedly juxtaposed concave lenses  3202 ,  3203 ,  3204  and  3205 , and there are two surfaces  3206 ,  3207  which are vertical surfaces of the front and the rear sides respectively, and a bottom surface  3208  of the light grating  3201  having multiple focuses is a plane surface.   4. Referring to  FIGS. 33 and 33A , in the drawings, a light grating  3301  having multiple focuses is composed of two arciform (one convex and one convex concave) mutually integratedly juxtaposed concave lenses  3302  and  3303 , and there are two surfaces  3304 ,  3305  which are vertical surfaces of the front and the rear sides respectively, and a bottom surface  3307  of the light grating  3301  having multiple focuses is a plane surface.   5. Referring to  FIGS. 34 and 34A , in the drawings, a light grating  3401  having multiple focuses is composed of three arciform (one convex lenses  3402  and two concave lenses  3403 ,  3404 ) mutually integratedly juxtaposed, and there are two surfaces  3405 ,  3406  which are vertical surfaces of the front and the rear sides respectively, and a bottom surface  3407  of the light grating  3401  having multiple focuses is a plane surface.   6. Referring to  FIGS. 35 and 35A , in the drawings, a light grating  3501  having multiple focuses is composed of four arciform (two convex lenses  3502 ,  3505  and two concave lenses  3503 ,  3504 ) mutually integratedly juxtaposed, and there are two surfaces  3506 ,  3507  which are vertical surfaces of the front and the rear sides respectively, and a bottom surface  3508  of the light grating  3501  having multiple focuses is a plane surface.       
 
         [0111]    By virtue that there are many kinds of light grating structures composed of mutually integratedly juxtaposed convex lenses, here we summarily list the above six kinds of composed structures, generally speaking, a convex lens grating having two or more focuses and composed of two or more mutually integratedly juxtaposed arciform (concave or convex) lenses in strip, cloud, or annular shapes all fall in the range of the light gratings with multiple focuses formed from the transparent boards of the present invention. 
         [0112]    According to the above list many kinds of embodiments, a light distribution board of the present invention can be used on a light outputting surface of a conventional lamp in lieu of a conventional lamp shade, thus a lamp set with a light distribution board of the present invention can be formed. 
         [0113]    In conclusion, by specifically designing on light gratings, a light distribution board of the present invention can get the expected effects thereof.