Patent Abstract:
LED-integrated lens comprising a light-entering section ( 1 ) in the shape of a hole, a light-emitting section ( 2 ) in the shape of a cup, incorporating an optical lens ( 3 ) positioned between said light-entering and light-emitting sections ( 1, 2 ) wherein the external surfaces of the light-entering ( 1 ) and of the light-emitting ( 2 ) sections include portions having densely-distributed convex facets. This lens enhances light utilization efficiency, avoids creating spots with color aberration hence greatly improves color rendering.

Full Description:
FIELD OF THE INVENTION 
     The present invention relates to a new type of lens, in particular, but not exclusively, for use with an LED luminaire having an LED integrated light source. 
     BACKGROUND TO THE INVENTION 
     An LED integrated light source lens contributes to boosting the surface luminous efficiency of an LED integrated light source. An LED integrated light source lens of the known kind, comprising a light entering section in the shape of hole and of a light emitting section in the shape of a cup, has smooth surfaces on both the light entering and emitting sections. This has as a disadvantage that light utilisation efficiency of the LED integrated light source is very poor. A further disadvantage is that this arrangement creates luminous spots with obvious colour aberration, that is the colour rendering index is adversely affected. 
     SUMMARY OF THE INVENTION 
     According to the present invention an LED integrated light source lens comprising a light entering section in the shape of a hole, a light emitting section in the shape of a cup, is disclosed incorporating an optical lens positioned between the light entering section and the light emitting section, wherein the external surfaces of the light entering and emitting sections include portions having densely distributed convex facets. 
     Preferably, the optical lens has a spotted surface on one side. 
     Preferably, the optical lens has a curved surface on the other side. 
     Preferably, the curved surface is convex. 
     Preferably, the hole is provided with a non-spherical surface at its base 
     This construction has a number of advantages. The densely distributed convex facets on the external surfaces of the light entering and emitting sections, cause the LED integrated light source to emit multi-point lights, which enhances light utilisation efficiency, creates no spot lights with colour aberration, this in turn greatly improves the colour rendering index. The side of the optical lens having a spotted surface, creates multi-point lights. The other side of the optical lens, having a curved surface, changes the light beam angle. 
     A further advantage is that such a lens is relatively squat allowing for the use of LED light sources together with such a lens in new applications. 
     According to a second aspect of the present invention a lens is provided with a plurality of light entering sections, each in the shape of a hole, a light emitting section associated with each of the light entering sections, the light emitting section being in the shape of a cup, is disclosed incorporating an optical lens positioned between each light entering section and the associated light emitting section, wherein the external surfaces of the associated light entering and emitting sections include portions having densely distributed convex facets. 
     According to a third aspect of the present invention, a downlight comprises a casing, a light source, a lens according to the first or second aspects of the present invention, a lens holder and a heat sink. 
     Preferably, the downlight further comprises a glass and retaining means for the glass. 
     Preferably, the light source comprises one or more LEDs mounted on a circuit board. Preferably, the circuit board may be formed of a ceramic material. Alternatively, the circuit board may be formed of aluminium and a brass or copper disc located between the circuit board and the heat sink. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example only, in relation to the attached Figures, in which 
         FIG. 1  shows a schematic perspective view of a first embodiment of a lens according to the present invention; 
         FIG. 2  shows a view from below of the lens of  FIG. 1 ; 
         FIG. 3  shows a section along line A-A of  FIG. 2 ; 
         FIG. 4  shows a section similar to that of  FIG. 3  showing schematically the flow of light through the lens; 
         FIG. 5  shows a side view of a second embodiment of a lens according to the present invention; 
         FIG. 6  shows a section along line A-A of  FIG. 5 ; 
         FIG. 7  shows a view from below of  FIG. 5 ; 
         FIG. 8  shows a perspective view of the front of  FIG. 5 ; 
         FIG. 9  shows a side view of a third embodiment of a lens according to the present invention; 
         FIG. 10  shows a view from below of  FIG. 9 ; 
         FIG. 11  shows a side view of a forth embodiment of a lens according to the present invention; 
         FIG. 12  shows a view from below of  FIG. 11 ; 
         FIG. 13  shows a side view of a fifth embodiment of a lens according to the present invention; 
         FIG. 14  shows a view from below of  FIG. 13 ; 
         FIG. 15  shows a side view of a sixth embodiment of a lens according to the present invention; 
         FIG. 16  shows a view from below of  FIG. 15 ; 
         FIG. 17  shows a side view of a seventh embodiment of a lens according to the present invention; 
         FIG. 18  shows a view from below of  FIG. 17 ; 
         FIG. 19  is a sectional view of a first embodiment of a down light in accordance with a second aspect of the present invention; and 
         FIG. 20  is a sectional view of a second embodiment of a down light in accordance with a second aspect of the present invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring first to  FIGS. 1 to 3 , the lens can be seen to comprise a substantially solid body  10  having a generally conical or frusto-conical portion  4  provided with a flange  12  extending thereabout providing a circular periphery to the lens. The conical or frusto-conical portion  4  extends from the circular flange  12 . The side of the flange  12  from which the conical or frusto-conical portion  4  extends will be referred to as the bottom or rear side and reference to an ‘upper side’, a ‘front side’, ‘above’ or ‘below’ should be interpreted accordingly. 
     The lens has a central vertical axis. The lens is formed from a transparent material. In the case of a transparent plastics material, the lens is preferably formed by injection moulding. 
     An upper portion of the conical or frusto-conical portion  4  is provided with a recess or hole provided therein. The hole is in the form of a blind recess. As may be seen form the figures the recess is hexagonal in section, though other sections may be used. The side or sides of the recess are aligned with the central vertical axis. 
     The tip of the conical or frusto-conical portion  4  is provided with two cut away portions  14  extending along a portion of a circumference of the conical or frusto-conical portion  4  to create two tabs  16  extending inbetween. From  FIG. 2 , it can be seen that the lens is symmetric about a central plane. 
     In use, an LED is located at the opening of the hole in the conical or frusto-conical portion  4 , such that the hole forms a light entering section  1  of the lens. A base of the hole is provided with a refractive surface  18  for example a spotted surface. In this embodiment the refractive surface  18  is circular in shape. From  FIG. 2  it can be seen that this has taken the form of a hexagonal pattern of convex facets formed on the surface of the base of the hole. In use, the refractive surface  18  creates multi-point light beams. Preferably, the refractive surface  18  is a non-spherical refractive surface. In this embodiment the refractive surface  18  is located on a generally level plane. 
     The external surface of the conical or frusto-conical portion  4  is provided with a network of densely distributed convex facets  24 . In use, these facets  24  create multi-point light beams. The facets  24  of this embodiment can be seen to be generally triangular. 
     An external surface of the light entering section  1  can thus be seen to be provided with convex facets  24  on the conical or frusto-conical portion  4  and convex facets on the refractive surface  18 . 
     The front of the lens is provided with a shaped recess. The shaped recess is in the shape of a cup, being generally concave, comprising an inclined surface  20  extending inwardly from the front face of the lens, the inclined surface  20  meeting a generally circular base  22  of the cup shape, the base  22  being convex in shape. The curved convex shape is used to change the light beam angle. The generally circular base  22  is provided with a network of refractive surfaces in the form of densely distributed convex facets. The inclined surface is preferably concave. 
     In use, the shaped recess forms a light emitting section  2  of the lens. 
     The portion of the lens between the hole and the shaped recess forms an optical body or lens  3  positioned therebetween. 
     It will be understood that the light entering section  1 , the light emitting section  2  and the optical lens  3  are formed as a unitary or one piece body from the transparent material. 
       FIGS. 5 to 8  show a second embodiment of a lens in accordance with the present invention. It is noted that this embodiment (and those following) do not feature the cut out at the end of the conical or frusto-conical portion. Also, the hole or blind recess is circular in section. 
     This embodiment (and those following) is further distinguished by the pattern of the network of refractive surfaces. 
     Similar reference numerals are used to refer to similar aspects of the invention. Thus, a conical or frusto-conical portion of a lens is provided with a flange  112 . A light entering section  101  includes an outer surface of the conical or frusto-conical portion provided with a network of refractive surfaces  124  and a non-spherical base surface  118  provided at rear surface of the lens. The network of refractive surfaces  124  generally diamond shaped. A generally concave light emitting section  102  comprises an inclined surface  120  extending inwardly from the front face of the lens, the inclined surface  120  meeting a generally circular base, the base being provided with a network of refractive surfaces  128 . In this embodiment (and those following) the base is generally planer. An optic lens  103  is defined between the light entering section  101  and the light emitting section  102 . 
     The functioning of the lens is now described with reference to  FIG. 4 . Light is emitted from a light source, such as an LED (not shown) and may adopt a number of paths. Light passing through the sides of the light entering section  101  will having passed through the lens encounter the network of convex facets  124 . This causes the light at the surface to form multipoint full reflection lights directed back toward the light emitting surface section  102 . The creation of multipoint full reflection lights decreases the glare index and increases the colour rendering index. 
     Light encountering the refractive surface  118  on the base of the hole is focussed on the network of refractive surfaces  128  on the light emitting section  102  of the lens. This improves light efficiency. 
     Light passing to the network of refractive surfaces  128  on the light emitting section  102  of the lens forms multi point refraction emitting light which decreases the glare index and increases the colour rendering index. 
     The inclined surface  120  surrounding the network of refractive surfaces on the light emitting section  102  of the lens facilitates the injection moulding process and improves product consistency. 
       FIGS. 9 and 10  show a third embodiment of a lens in accordance with the present invention. The third embodiment is of similar section to the second embodiment and shows a further pattern of refractive surfaces  224 , the facets comprising a mix of diamond shaped facets and pentagonal facets. 
       FIGS. 11 and 12  show a fourth embodiment of a lens in accordance with the present invention. The fourth embodiment is of similar section to the second embodiment and shows a further pattern of refractive surfaces  324 , the facets comprising a mix of hexagonal facets and pentagonal facets. 
       FIGS. 13 and 14  show a fifth embodiment of a lens in accordance with the present invention. The fifth embodiment is of similar section to the second embodiment and shows a further pattern of refractive surfaces  424 , the facets comprising a mix of diamond shaped facets and octagonal facets. 
       FIGS. 15 and 16  show a sixth embodiment of a lens in accordance with the present invention. The sixth embodiment is of similar section to the second embodiment and shows a further pattern of refractive surfaces  524 , the facets comprising generally rectangular facets. 
       FIGS. 17 and 18  show an seventh embodiment of a lens in accordance with the present invention. The seventh embodiment is of similar section to the second embodiment and shows a further pattern of refractive surfaces  624 , the facets comprising a patterning of polygonal facets. 
     In each of the embodiments the refractive surfaces comprise convex facets. In a further embodiment shown in use in  FIG. 19 , a lens is provided having a plurality of light entering sections, each having an associated light emitting section and an optical lens positioned between each light entering section and the associated light emitting section. 
     Referring now to  FIG. 19 , there is shown a lighting unit is the form of a downlight unit  702  incorporating a terminal block, transformer unit or driver  704  provided on a mounting arm secured at one end to an upper end of the downlight unit  702 . 
     The downlight unit comprises a light source  706  in the form of a plurality of LEDs mounted to a circuit board  708 , for example an aluminium printed circuit board, the circuit board including control circuitry for the light source  706 , a heat sink  710  connected to a cylindrical casing, the heat sink  710  being provided to a rear side of the circuit board  708  and a lens arrangement located at a front side of the circuit board  708 . 
     A brass or copper disc  740  is provided between the circuit board  708  and the heat sink  710 . 
     The term “cylindrical casing” means conforming approximately to the shape of a hollow cylinder. It will be understood that a misshapen cylinder will work equally well. Similarly, while the embodiments show a generally circular cylindrical tubular body other sections may be used with amendment to the sectional shape of other components. 
     The heat sink  710  is formed from any suitable material, preferably cast aluminium. The heat sink  710  comprises at a lower end an outer annular portion for location against an upper portion of the cylindrical casing. The annular portion surrounds an end face. In the illustrated embodiment the end face is proud of the annular portion. 
     The cylindrical casing comprises a mounting ring  714 . The mounting ring  714  comprises a side wall having a lower peripheral annular flange extending outwardly from a bottom end of the side wall and an upper peripheral annular flange extending inwardly from an upper end of the side wall. The mounting ring  714  is formed from any suitable material, preferably steel. 
     The upper peripheral flange locates against the annular portion of the heat sink  710  and surrounds the end face of the heat sink. 
     A first ring or washer  716  of silicon is provided on the upper surface of the lower peripheral flange. In use, the ring or washer  716  butts up against a rim of an aperture into which the downlight is fitted. 
     A bracket  718  incorporating spring biased members or clips  720  is located about the heat sink  710 . The spring biased members or clips  720  are adapted to secure the lighting unit in a recess in a known manner. It can be seen that the driver  704  is secured a central upper region of the bracket  718 . The bracket  718  is secured to the upper peripheral flange of the mounting ring  714  in a suitable fashion, for example by screw fasteners  722 . 
     The lens arrangement comprises a lens holder  724  and a lens  726  in accordance with the second aspect of the present invention. The lens holder  726  may be of any suitable material, for example a polycarbonate. The lens  724  may be of any suitable material, for example polymethylmethacrylate. 
     The lens  726  is retained in position relative to the light source  706  by the lens holder  724 . The lens holder  724  comprises a ring or washer having a support structure for engaging and securing the lens  726  to the lens holder  724 , as well as an inwardly directed finger or fingers. The lens  726  is provided with cooperating features to engaging the lens holder  724  and becoming secured to it. The lens holder  724  is secured at its periphery to the upper peripheral flange of the mounting ring  714  in a suitable fashion, for example by utilising the screw fasteners  722  securing the bracket  718  to the mounting ring  714 . 
     A bezel  730  is fitted to an underside of the mounting ring  14 . The bezel  730  may be of any suitable material, for example cast aluminium. The bezel  730  comprises an inner wall having an inwardly directed shoulder toward a lower end and a radially outwardly directed annular flange at the lower end. The inner wall extends within the side wall of the mounting ring  714 . In use the inner wall of the bezel and the side wall of the mounting ring are provided with cooperating features, such as male and female parts of a bayonet fixing, to enable the bezel  730  to be secured to the mounting ring  714 . In use the inner shoulder supports a glass  732  located in front of the lens  726 . The glass  732  is of any suitable material to allow transmission of the light emitted from the lens  726 . 
     Preferably a second ring or washer  734  of silicon extends between the radially outwardly directed annular flange of the bezel  30  and the first peripheral flange of the mounting ring  14 . 
     The circuit board  708  is generally circular and provided with openings by which the circuit board may be located in position. In practice the brass or copper disc  740  is secured about its periphery to the mounting ring  714 . The end face of the heat sink  10  is in thermal contact with a rear face of the brass or copper disc  740 . The circuit board  708  is secured through the brass or copper disc  740  to the heat sink  710  by any suitable means such as fasteners. 
     A ring or washer  736  of a suitable fireproof material is preferably located between the edge of brass or copper disc  740  and the upper peripheral flange of the mounting ring  714 . 
     A second embodiment of a downlight unit  802  in accordance with the present invention is shown in  FIG. 20 . Similar parts will be referred to by similar reference numerals. The downlight unit  802  comprises a light source  806  mounted to a circuit board  808 , the circuit board including control circuitry for the light source  806 , a heat sink  810  provided to a rear side of the circuit board  808  and a lens arrangement located at a front side of the circuit board. The mounting ring  814  is of like configuration to that of the previous embodiment. 
     A bracket  818  having depending legs and a central portion is provided in which spring biased members or clips  820  are mounted on each of the legs. Feet at the free ends of the legs are secured to the mounting ring  814 . 
     A driver  804  is mounted within a driver box in turn located within a recess in the heat sink  810 . The driver box is provided with flanges by which the driver box may be secured to an upper part of the heat sink  810  by any suitable means. 
     The heat sink  810  is mounted on the mounting ring  814  with a front face of the heat sink  810  being located within an upper annular flange of the mounting ring  814 . 
     A first ring or washer  816  of silicon is provided on a lower peripheral flange of the mounting ring  814 . 
     The circuit board  808  is secured to the mounting ring  814  by fasteners  822 , such that the end face of the heat sink  810  is in thermal contact with a rear surface of the circuit board  808 . The fasteners  822  also serve to secure a lens holder in position. The lens holder is used to locate a lens  826  in position. 
     In this embodiment, the lens holder comprises two parts. A first part  824   a  of the lens holder is secured in place to the upper peripheral flange of the mounting ring  814 . A second part  824   b  of the lens holder retains a periphery of the lens  826  between itself and the first part  824   a  of the lens holder. 
     A glass  832  retained by a bezel  830 , itself located within and by the mounting ring  814 , is disposed in front of the lens  826  and lens holder. A second ring or washer  834  of silicon extends between the bezel  830  and the mounting ring  814 . A ring or washer  836  of fireproof material is preferably located between the circuit board  808  and the mounting ring  824 .

Technology Classification (CPC): 5