Abstract:
A light distribution board having an improved light grating structure including 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 arciform (concave or convex) lenses and at least one lens with a non-arciform surface to form a light grating having at least two 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 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.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a light distribution board having an improved light grating structure including a plurality of light gratings each with multiple focuses; and especially to a light distribution board that can illuminate (by using the principles of optical reflection and refraction) 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 to be 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 being 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, they are mounted each 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 so 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 gratings. 
         [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  202 , and a top surface having a plurality of saw toothed gratings  203 ,  204 , the rhombic grating unit  201  is shaped from two straight bevel edges  205 ,  208  being oppositely disposed as mirror images for each other; several incident light beams  206  enter a bevel edge  205  of the saw toothed grating  203  in an identical incident angular direction to result a first time refraction, when the light beams  206  reach the plane surface  202 , they are once more refracted toward a district  207  to be illuminated; similarly, several incident light beams  209  enter a bevel edge  208  of the saw toothed grating  204  in an identical incident angular direction to result a first time refraction, when the light beams  209  reach the plane surface  202 , 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  202  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 with 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  302 , and a top surface having a plurality of convex lenses gratings  303 ,  304 . Several incident light beams  305  enter the convex lens grating  303  in an identical incident angular direction to result a first time refraction, when the light beams  305  reach the plane surface  302 , they are once more refracted toward a district  306  to be illuminated; similarly, several incident light beams  307  enter the convex lens grating  304  in an identical incident angular direction to result a first time refraction, when the light beams  307  reach the plane surface  302 , 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  303 ,  304  in an identical incident angular direction will create refractions in different angular directions, wherein the convex lens grating  304  of a smaller curvature has a longer focus, the light beams after being refracted from the convex lens grating  304  cross at the focus, they form a narrower illuminated range at the district  308 ; 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  306 . If the convex lens grating unit  301  is applied for light distribution, 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 distances of irradiation are 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. 
         [0009]    Referring to  FIG. 4  which shows a structure having a light distribution grating unit  401  having a plurality of saw tooth shaped gratings invented by the inventor of the present invention and having been filed as a Taiwan patent application with a filing no. 96140922; in which the light distribution grating unit  401  with multiple saw tooth shaped (gratings) has a plane bottom surface  402 , and a top surface having a plurality of saw tooth shaped (gratings)  403 ,  404 ,  405 ,  406  and  407  each being composed of an arciform surface and a straight inclined surface (non-arciform surface), summarily, here we see a kind of arciform surface and a kind of non-arciform surface of which the saw tooth shaped (grating)  403  is composed of a convex lens (arciform surface)  423  and a straight inclined surface (non-arciform surface)  409 .Several incident light beams  408  enter the straight inclined surface (non-arciform surface)  409  of the saw tooth shaped (grating)  403  to result a first time refraction, when the light beams  408  reach the plane surface  402 , they are once more refracted down and leftwards toward a district  410  to be illuminated, the saw tooth shaped (grating)  404  is composed of a convex lens (arciform surface)  424  and a straight inclined surface (non-arciform surface)  412 ; similarly; several incident light beams  411  enter the straight inclined surface  412  of the saw tooth shaped (grating)  404  to result a first time refraction, when the light beams  411  reach the plane surface  402 , they are once more refracted down and leftwards toward a district  413  to be illuminated; and more, several incident light beams  414  enter a convex lens (arciform surface)  415  of the saw tooth shaped (grating)  405  to result a first time refraction, when the light beams  415  reach the plane surface  402 , they are once more refracted down and rightwards toward a district  416  to be illuminated, the saw tooth shaped (grating)  406  is composed of a convex lens (arciform surface)  418  and a straight inclined surface (non-arciform surface)  426 ; and several incident light beams  417  enter an arciform surface  418  of the saw tooth shaped (grating)  406  to result a first time refraction, when the light beams  417  reach the plane surface  402 , they are once more refracted down and rightwards toward a district  419  to be illuminated, the saw tooth shaped (grating)  407  is composed of a convex lens (arciform surface)  421  and a straight inclined surface (non-arciform surface)  427 ; and several incident light beams  420  enter a convex lens (arciform surface)  421  of the saw tooth shaped (grating)  407  to result a first time refraction, when the light beams  420  reach the plane surface  402 , they are once more refracted down and rightwards toward a district  422  to be illuminated; We can see from the drawing that the light beams  411  after being irradiated to the straight inclined surface (non-arciform surface)  412  having larger inclination angles in an identical incident angular direction will create larger refraction angles, i.e., the district  422  to be illuminated is farther right below the lamp; on the contrary, the light beams  408  after being irradiated to the straight inclined surface  409  having smaller inclination angles in an identical incident angular direction will create smaller refraction angles, i.e., the district  422  to be illuminated is nearer right below the lamp; the above two groups of light beams  411 ,  408  respectively are all parallel without crossing and diffusion, the light beams  411 ,  408  reaching the district  422  to be illuminated are in partially concentrated forms; the incident light beams  414  in an identical incident angular direction entering the arciform surface  415  (having same curvature but larger inclination angle) will create larger refraction angles and crossing state, i.e., the district  416  to be illuminated is farther right below the lamp, and the range of illumination in it is wider; on the contrary, the light beams  417  in an identical incident angular direction entering the convex lens (arciform surface)  418  (having same curvature but smaller inclination angle) will create smaller refraction angles and crossing state, i.e., the district  419  to be illuminated is nearer right below the lamp, and the range of illumination in it is narrower; the convex lenses (arciform surfaces)  415 ,  418  are arciform surfaces with same inclination angle but different curvatures; the light beams  420  in an identical incident angular direction entering the convex lens (arciform surface)  421  (having a larger curvature) cross at a focus with a shorter distance after refraction to result a wider range of illumination; on the contrary, the light beams  417  in an identical incident angular direction entering the convex lens (arciform surface)  418  (having a smaller curvature) cross at a focus with a longer distance after refraction result a narrower range of illumination. 
         [0010]    Referring to  FIG. 5 , which shows a light distribution board structure having a plurality of gratings (each with multiple focuses) composed of at least two convex lenses also invented by the inventor of the present invention and having been filed as a US patent application with a filing Ser. No. 12/174,534; in which the light grating  501  with multiple focuses has a plane bottom surface  502 , and a top surface having a plurality of light gratings  503 ,  504  and  505  each with multiple focuses, wherein the light grating  503  with multiple focuses is composed of two convex lenses (arciform surfaces)  506 ,  507  of same curvature and size, the light grating  504  with multiple focuses is composed of two convex lenses (arciform surfaces)  508 ,  509  of same curvature but different sizes, the light grating  505  with multiple focuses is composed of three convex lenses (arciform surfaces)  510 ,  511  and  512  of different curvatures and different sizes; wherein curvature and size of each convex lens (arciform surface)are changed in pursuance of the angles of refraction of the light beams and the range being illuminated. 
       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 an improved light grating structure including 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 concave or convex lenses and at least one lens each with a non-arciform surface, to form a convex lens 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 or is formed thereon a plurality of normal convex lenses, 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 having an improved light grating structure 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 concave or convex lenses and at least one lens each with a non-arciform surface to form a light grating unit 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 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 having an improved light grating structure 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 concave or convex lenses and at least one lens each with a non-arciform surface to form a convex lens 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 or a surface formed thereon a plurality of normal convex lenses, and the bottom surface is an illuminating surface of the lamp. 
         [0014]    In a light distribution board having an improved light grating structure provided in the present invention, curvature and inclination angle of each concave or convex lens of a light grating having multiple focuses and inclination angle of the aforesaid at least one lens each with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the 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. 
         [0015]    The light distribution board having an improved light grating structure 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 normal convexes; 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 can be avoided, and the light beams become more tender under the condition that lose of brightness is minimum. 
         [0016]    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 
         [0017]      FIG. 1A  is a schematic sectional view of a conventional half covering type illumination lamp; 
           [0018]      FIG. 1B  is a schematic sectional view of a conventional fully covering type illumination lamp; 
           [0019]      FIG. 2  is a schematic view showing the light beam progressing of a conventional rhombic grating structure; 
           [0020]      FIG. 3  is a schematic view showing the light beam progressing of a conventional convex lens grating; 
           [0021]      FIG. 4  is a schematic view showing a light grating structure having a plurality of saw toothed lenses; 
           [0022]      FIG. 5  shows a light grating structure composed of at least two convex lenses (at least with two focuses); 
           [0023]      FIGS. 6 ,  6 A show a light grating having multiple focuses of the present invention being composed of two convex lenses and a non-arciform surface; 
           [0024]      FIGS. 7 ,  7 A show a light grating having multiple focuses of the present invention also being composed of two convex lenses and a non-arciform surface; 
           [0025]      FIGS. 8 ,  8 A show a light grating having multiple focuses of the present invention being composed of two convex lenses and two non-arciform surfaces; 
           [0026]      FIGS. 9 ,  9 A show a light grating having multiple focuses of the present invention also being composed of two convex lenses and two non-arciform surfaces; 
           [0027]      FIGS. 10 ,  10 A show a light grating having multiple focuses of the present invention being composed of three convex lenses and a non-arciform surfaces; 
           [0028]      FIGS. 11 ,  11 A show a light grating having multiple focuses of the present invention being composed of two convex lenses and three non-arciform surfaces; 
           [0029]      FIG. 12  is an enlarged schematic view showing a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0030]      FIGS. 13 ,  13 A and  13 B are plane views of a first embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0031]      FIGS. 14 ,  14 A and  14 B are plane views of a second embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0032]      FIGS. 15 ,  15 A and  15 B are plane views of a third embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0033]      FIGS. 16 ,  16 A and  16 B are plane views of a fourth embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0034]      FIGS. 17 ,  17 A and  17 B are plane views of a fifth embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0035]      FIGS. 18 and 18A  are plane views of a sixth embodiment of a light distribution board of the present invention; the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0036]      FIGS. 19 ,  19 A are plane views of a seventh embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0037]      FIGS. 20 ,  20 A and  20 B are plane views of a eighth embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0038]      FIGS. 21 ,  21 A and  21 B are plane views of a ninth embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0039]      FIGS. 22 ,  22 A and  22  B are plane views of a tenth embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0040]      FIGS. 23 ,  23 A and  23 B are plane views of a eleventh embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0041]      FIGS. 24 and 24A  are plane views of a twelfth embodiment of a light distribution board of the present invention having an improved light grating structure with a plurality of light gratings each having multiple focuses; 
           [0042]      FIG. 25  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; 
           [0043]      FIG. 26  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; 
           [0044]      FIGS. 27 ,  27 A show a light grating having multiple focuses of the present invention being composed of two concave lenses and a non-arciform surface; 
           [0045]      FIGS. 28 ,  28 A show another light grating having multiple focuses of the present invention being composed of two concave lenses and a non-arciform surface; 
           [0046]      FIGS. 29 ,  29 A show a light grating having multiple focuses of the present invention being composed of two concave lenses and two non-arciform surfaces; 
           [0047]      FIGS. 30 ,  30 A show a light grating having multiple focuses of the present invention being composed of a convex lens, a concave lens and a non-arciform surface; 
           [0048]      FIGS. 31 ,  31 A show another light grating having multiple focuses of the present invention being composed of t a convex lens, a concave lens and a non-arciform surface; 
           [0049]      FIGS. 32 ,  32 A show a light grating having multiple focuses of the present invention being composed of a convex lens, a concave lens and two non-arciform surfaces. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0050]    The present invention relates a light distribution board having an improved light grating structure 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 each having multiple focuses, each of the light gratings having multiple focuses is composed of two or more convex lenses and at least one lens each with a non-arciform surface to form a convex lens grating having two or more focuses, curvature and inclination angle of each convex lens and inclination angle of the aforesaid at least one lens each with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. 
         [0051]    The present invention is described with many embodiments below: 
         [0052]    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. 6 and 6A , in the drawings, a light grating  602  having multiple focuses is composed of two convex lenses  602  and  603  and a lens with a non-arciform surface  604 , and there are two surfaces  605 ,  606  which are vertical surfaces of the front and the rear sides respectively of the light grating  601  which is strip like, cloud shaped or annular, and a bottom surface  607  of the light grating  601  having multiple focuses is a plane surface.   2. Referring to  FIGS. 7 and 7A , in the drawings, a light grating  701  having multiple focuses is composed of two convex lenses  702 , and  703  and a lens with a non-arciform surface  704 , and there are two surfaces  705  and  706  which are vertical surfaces of the front and the rear sides respectively of the light grating  701  which is strip like, cloud shaped or annular, and a bottom surface  707  of the light grating  701  having multiple focuses is a plane surface.   3. Referring to  FIGS. 8 and 8A , in the drawings, a light grating  801  having multiple focuses is composed of two convex lenses  802  and  803  and two lenses each with a non-arciform surface  804 ,  805  and there are two surfaces  806 ,  807  which are vertical surfaces of the front and the rear sides respectively of the light grating  801  which is strip like, cloud shaped or annular, and a bottom surface  808  of the light grating  801  having multiple focuses is a plane surface.   4. Referring to  FIGS. 9 and 9A , in the drawings, a light grating  901  having multiple focuses is composed of two convex lenses  904  and  905  and two lenses each with a non-arciform surface  802 ,  803 , and there are two surfaces  906 ,  907  which are vertical surfaces of the front and the rear sides respectively of the light grating  901  which is strip like, cloud shaped or annular, and a bottom surface  908  of the light grating  901  having multiple focuses is a plane surface.   5. Referring to  FIGS. 10 and 10A , in the drawings, a light grating  1001  having multiple focuses is composed of three convex lenses  1002 ,  1003  and  1004  and a lens with a non-arciform surface  1005 , and there are two surfaces  1006 ,  1007  which are vertical surfaces of the front and the rear sides respectively of the light grating  1001  which is strip like, cloud shaped or annular, and a bottom surface  1008  of the light grating  1001  having multiple focuses is a plane surface.   6. Referring to  FIGS. 11 and 11A , in the drawings, a light grating  1101  having multiple focuses is composed of two convex lenses  1102 ,  1103  and three lenses each with a non-arciform surface  1104 ,  1105  and  1106 , and there are two surfaces  1107 ,  1108  which are vertical surfaces of the front and the rear sides respectively of the light grating  1101  which is strip like, cloud shaped or annular, and a bottom surface  1108  of the light grating  1101  having multiple focuses is a plane surface.       
 
         [0059]    By virtue that there are many kinds of light grating structures composed of convex lenses, here we summarily list the above six kinds of composed structures, generally speaking, a convex lens grating having two or more convex lenses and at least one lens each with a non-arciform surface, and being in strip, cloud, or annular shapes all fall in the scope of the light gratings with multiple focuses formed from the transparent boards of the present invention. 
         [0060]    Referring to  FIG. 12  which is an enlarged schematic view showing a light distribution board  1201  having an improved light grating structure with a plurality of light gratings each having multiple focuses and in strip, annular, cloud or granular shapes presented in partial sectional view of the present invention; in the drawing, a bottom surface  1202  of the light distribution board  1201  is a plane surface, and the top surface of the light distribution board  1201  is formed thereon a plurality of light gratings (having multiple focuses)  1203 ,  1204 ,  1205 ,  1206  and  1207 , wherein the light grating (having multiple focuses)  1203  is composed of two convex lenses  1208 ,  1210  and a non-arciform surface  1212 ; the convex lens  1208  having multiple focuses has a focus  1209 , the other convex lens  1210  has a focus  1211 ; the light gratings  1204  is composed of two convex lenses  1213 ,  1215  and a non-arciform surface  1217 ; the convex lens  1213  having multiple focuses has a focus  1214 , the other convex lens  1215  has a focus  1216 ; the convex lens  1205  having multiple focuses is composed of two convex lenses  1218 ,  1220  and two non-arciform surfaces  1222 ,  1223 , the convex lens  1220  has a focus  1221 , the convex lens  1206  having multiple focuses is composed of two convex lenses  1224 ,  1226  and two non-arciform surfaces  1228 ,  1229 , of which the convex lens  1224  has a focus  1225 , the other convex lens  1226  has a focus  1227 ; the convex lens  1207  having multiple focuses is composed of three convex lenses  1230 ,  1232 ,  1234  and a non-arciform surface  1236 , the convex lens  1230  has a focus  1231 , the convex lens  1232  has a focus  1233 , and the convex lens  1234  has a focus  1235 . 
         [0061]    Referring to  FIGS. 13 ,  13 A and  13 B which are plane views of a first embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses 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 strip like light gratings  1303  each having multiple focuses. The curvature and inclination angle of each convex lens of the strip like light gratings  1303  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. 
         [0062]    Referring to  FIGS. 14 ,  14 A and  14 B which are plane views of a second embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses 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 annular light gratings  1403  each having multiple focuses. The curvature and inclination angle of each convex lens of the annular light gratings  1403  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. 
         [0063]    Referring to  FIGS. 15 ,  15 A and  15 B which are plane views of a third embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses 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 cloud shaped light gratings  1503  each having multiple focuses. The curvature and inclination angle of each convex lens of the cloud shaped light gratings  1503  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. 
         [0064]    Referring to  FIGS. 16 ,  16 A and  16 B which are plane views of a fourth embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses of the present invention, in the drawings, a bottom surface  1602  of a transparent board  1601  is a plane surface, and a top surface of the transparent board  1601  is formed thereon a plurality of annular light gratings  1603  each having multiple focuses. These annular light gratings  1603  having multiple focuses are arranged in steps. The curvature and inclination angle of each convex lens of the annular light gratings  1603  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. 
         [0065]    Referring to  FIGS. 17 ,  17 A and  17 B which are plane views of a fifth embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses of the present invention, in the drawings, a bottom surface  1702  of a transparent board  1701  is an arciform surface, and a top surface of the transparent board  1701  is formed thereon a plurality of annular light gratings  1703  each having multiple focuses. These annular light gratings  1703  having multiple focuses are arranged in steps. The curvature and inclination angle of each convex lens of the annular light gratings  1703  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. 
         [0066]    Referring to  FIGS. 18 and 18A  which are plane views of a sixth embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses 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 thereon a plurality of non-concentric annular light gratings  1803 ,  1804  and  1805  all having multiple focuses and a plurality of partially annular light gratings  1806 ,  1807 ,  1808 ,  1809 ,  1810 ,  1811 ,  1812 ,  1813  and  1814  all having multiple focuses. The curvature and inclination angle of each convex lens of the annular light gratings  1803  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. 
         [0067]    Referring to  FIGS. 19 and 19A  which are plane views of a seventh embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses of the present invention, in the drawings, a bottom surface  1902  of a transparent board  1901  is a plane surface, and a top surface of the transparent board  1901  is thereon a plurality of non-concentric annular light gratings  1903 ,  1904 ,  1905  and  1906  all having multiple focuses. The curvature and inclination angle of each convex lens of the annular light gratings  1803  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. 
         [0068]    Referring to  FIGS. 20 ,  20 A and  20 B which are plane views of an eighth embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses of the present invention, in the drawings, a bottom surface 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 strip like light gratings  2003  each having multiple focuses. The curvature and inclination angle of each convex lens of the strip like light gratings  2003  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. The principle of designing the curvatures of the normal convex lenses  2002  is same as that stated for  FIG. 3 . 
         [0069]    Referring to  FIGS. 21 ,  21 A and  21 B which are plane views of a ninth embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses of the present invention, in the drawings, a bottom surface of a transparent board  2101  is formed thereon a plurality of normal convex lenses  2102 , and a top surface of the transparent board  2101  is formed thereon a plurality of annular light gratings  2103  each having multiple focuses. The curvature and inclination angle of each convex lens of the annular light gratings  2103  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. The principle of designing the curvatures of the normal convex lenses  2102  is same as that stated for  FIG. 3 . 
         [0070]    Referring to  FIGS. 22 ,  22 A and  22 B which are plane views of a tenth embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses of the present invention, in the drawings, a bottom surface of a transparent board  2201  is formed thereon a plurality of normal convex lenses  2202 , and a top surface of the transparent board  2201  is formed thereon a plurality of annular light gratings  2203  each having multiple focuses. These annular light gratings  2203  having multiple focuses are arranged in steps. The curvature and inclination angle of each convex lens of the annular light gratings  2203  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. The principle of designing the curvatures of the normal convex lenses  2202  is same as that stated for  FIG. 3 . 
         [0071]    Referring to  FIGS. 23 ,  23 A and  23 B which are plane views of an eleventh embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses of the present invention, in the drawings, a bottom surface of a transparent board  2301  is formed thereon a plurality of normal convex lenses  2302 , and a top surface of the transparent board  2301  is formed thereon a plurality of annular light gratings  2303  each having multiple focuses. These annular light gratings  2303  having multiple focuses are arranged in steps. The curvature and inclination angle of each convex lens of the annular light gratings  2303  having multiple focuses and the inclination angle of each of the aforesaid lenses with a non-arciform surface are changed in pursuance of the angles of refraction of the incident light beams through the lens surfaces. The principle of designing the curvatures of the normal convex lenses  2302  is same as that stated for  FIG. 3 . 
         [0072]    Referring to  FIGS. 24 , and  24 A which are plane views of a twelfth embodiment of light distribution board having an improved light grating structure with a plurality of light gratings each having multiple focuses of the present invention, in the drawings, there is a two-layer light distribution board  2401  composed of two transparent boards  2402 ,  2403  of which one overlaps the other, each of the two transparent boards  2402 ,  2403  can be as any of the above eleven kinds of embodiments of light distribution boards. In the drawings, the two transparent boards  2402 ,  2403  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. 
         [0073]    Referring to  FIG. 25  which shows an embodiment of the present invention, of which at least a side of at least a transparent board is used to form a light distribution board with a plurality of light gratings each having multiple focuses and is applied to a lamp, in which a light distribution board randomly chosen from any of the above first to eleventh 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  2501  as that of the second embodiment of the present invention is used for an example, a top surface of the light distribution board  2501  is formed thereon a plurality of annular light gratings each having multiple focuses and faces to a light source  102  being a light receiving surface, a bottom surface  2502  of the light distribution board  2501  is a plane surface as a light outputting surface. 
         [0074]    When a light beam  2506  enters a convex lens  2508  of the light distribution board  2507  to create a first time refraction, and when the light beam  2506  reaches the plane surface  2502 , it is once more refracted down and rightwards toward a district to be illuminated. A light beam  2509  enters a convex lens  2511  of a light grating  2510  of the light distribution board  2501  to create a first time refraction, and when the light beam  2509  reaches the plane surface  2502 , it is once more refracted down and leftwards and enters the district to be illuminated. A light beam  2503  enters a convex lens  2505  of a light grating  2504  of the light distribution board  2501  after being reflected by a reflective surface  103  to create a first time refraction, and when the light beam  2503  reaches the plane surface  2502 , it is once more refracted down and rightwards and enters the district to be illuminated. A light beam  2512  enters a convex lens  2514  of a light grating  2513  of the light distribution board  2501  after being reflected by the reflective surface  103  to create a first time refraction, and when the light beam  2512  reaches the plane surface  2502 , it is once more refracted down and leftwards and enters the district to be illuminated. The light distribution board  2501  definitely can control illumination of a specific district to be illuminated by most of the light beams from the 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, and an effect of saving energy can thus be achieved. 
         [0075]    Referring to  FIG. 26  which shows another embodiment of the present invention, of which at least a side of at least a transparent board is used to form a light distribution board with a plurality of light gratings each having multiple focuses and is applied to a lamp, in which a light distribution board  2601  chosen from the above twelfth 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  2601  is formed from two transparent boards  2602 ,  2603  of which one overlaps the other. 
         [0076]    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 above various structures:
       1. Referring to  FIGS. 27 and 27A , in the drawings, a light grating  2701  having multiple focuses is composed of two concave lenses  2702  and  2703  and a lens with a non-arciform surface  2704 , and there are two surfaces  2705 ,  2706  which are vertical surfaces of the front and the rear sides respectively of the light grating  2701  which is strip like, cloud shaped or annular, and a bottom surface  2707  of the light grating  2701  having multiple focuses is a plane surface.   2. Referring to  FIGS. 28 and 28A , in the drawings, a light grating  2801  having multiple focuses is composed of two concave lenses  2802 , and  2803  and a lens with a non-arciform surface  2804 , and there are two surfaces  2805  and  2806  which are vertical surfaces of the front and the rear sides respectively of the light grating  2801  which is strip like, cloud shaped or annular, and a bottom surface  2807  of the light grating  2801  having multiple focuses is a plane surface.   3. Referring to  FIGS. 29 and 29A , in the drawings, a light grating  2901  having multiple focuses is composed of two concave lenses  2902  and  2903  and two lenses each with a non-arciform surface  2904 ,  2905  and there are two surfaces  2906 ,  2907  which are vertical surfaces of the front and the rear sides respectively of the light grating  2901  which is strip like, cloud shaped or annular, and a bottom surface  2908  of the light grating  2901  having multiple focuses is a plane surface.   4. Referring to  FIGS. 30 and 30A , in the drawings, a light grating  3001  having multiple focuses is composed of a convex lens  3002 , a concave lens  3003  and a lens with a non-arciform surface  3004 , and there are two surfaces  3005 ,  3006  which are vertical surfaces of the front and the rear sides respectively of the light grating  3001  which is strip like, cloud shaped or annular, and a bottom surface  3007  of the light grating  3001  having multiple focuses is a plane surface.   5. Referring to  FIGS. 31 and 31A , in the drawings, a light grating  3101  having multiple focuses is composed of a convex lens  3102 , a concave lens  3103  and a lens with a non-arciform surface  3104 , and there are two surfaces  3105 ,  3106  which are vertical surfaces of the front and the rear sides respectively of the light grating  3101  which is strip like, cloud shaped or annular, and a bottom surface  3107  of the light grating  3101  having multiple focuses is a plane surface.   6. Referring to  FIGS. 32 and 32A , in the drawings, a light grating  3201  having multiple focuses is composed of a convex lens  3203 , a concave lens  3202  and two lenses each with a non-arciform surface  3204 ,  3205 , and there are two surfaces  3206 ,  3207  which are vertical surfaces of the front and the rear sides respectively of the light grating  3201  which is strip like, cloud shaped or annular, and a bottom surface  3208  of the light grating  3201  having multiple focuses is a plane surface.       
 
         [0083]    According to the above list many kinds of embodiments, the light distribution boards of the present invention can be used respectively for 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. 
         [0084]    In conclusion, by specifically designing on light gratings, the light distribution boards of the present invention can get the expected effects thereof.