Patent Publication Number: US-9416926-B2

Title: Lens with inner-cavity surface shaped for controlled light refraction

Description:
RELATED APPLICATION 
     This application is a continuation-in-part of patent application Ser. No. 12/431,308, filed Apr. 28, 2009, and is a continuation-in-part of U.S. application Ser. No. 13/843,649, filed Mar. 15, 2013. The entirety of the contents of both such patent applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to lighting fixtures and, more particularly, to optics designed for desired LED light distribution. This invention also relates to the field of LED optics. 
     BACKGROUND OF THE INVENTION 
     In recent years, the use of light-emitting diodes (LEDs) for various common lighting purposes has increased, and this trend has accelerated as advances have been made in LEDs and in LED-array bearing devices, often referred to as “LED modules.” Indeed, lighting needs which have primarily been served by fixtures using high-intensity discharge (HID) lamps, halogen lamps, compact florescent light (CFL) and other light sources are now increasingly beginning to be served by LEDs. Creative work continues in the field of LED development, and also in the field of effectively utilizing as much of the light emitted from LEDs as possible. 
     Some efforts have been made to develop small lenses for directing light emitted by small LED packages, and utilizing lenses intended to redirect some amount of emitted light to form a desired illumination pattern. However, such lenses have tended to fall short of the most highly desirable performance in that some of the LED-emitted light is often lost. 
     Typically, some of the LED-emitted light rays are oriented at angles that previously would result in illumination of undesirable areas and thus produce less than fully efficient illumination patterns. Prior lenses would typically be arranged to either prevent these undesirable light rays from exiting the lens or to block these rays immediately upon their exiting the lens. Even though these steps were deemed necessary to achieve desired illumination patterns and to prevent so-called lighting “trespass,” they resulted in lost light and decreased efficiency of LED illuminators. It would be highly desirable to improve efficiency of output of light emitted by LEDs. 
     Typical LED illuminators emit light at a wide range of angles such that light rays reach the same area of the output surface of a lens at different angles. This has made it very difficult to control refraction of such light. As a result, only a portion of light being refracted is refracted in a desired direction, while the reminded exited the lens with very little control. It would be desirable to provide improved control of the direction of light exiting a lens. 
     Trespass lighting can be evaluated by more than just the amount of light emitted toward an undesirable direction; also to be considered is how far from the desired direction such light is directed. It would be highly beneficial to provide a lighting apparatus which produces a desired illumination pattern with a maximum amount of light emitted toward an area intended to be illuminated. 
     OBJECTS OF THE INVENTION 
     It is an object of the invention to provide improved LED optics (lenses) to overcome some of the problems and shortcomings of the prior art, including those referred to above. 
     Another object of the invention is to provide an LED lens with improved light-output efficiency. 
     Another object of the invention is to provide an LED lens with improved control of the direction of light exiting the optic. 
     How these and other objects are accomplished will become apparent from the following descriptions and the drawings. 
     SUMMARY OF THE INVENTION 
     This invention is a lens with improved efficiency of output of light from a light emitter which has an emitter axis and defines an emitter plane. It is preferred that the light emitter is an LED package which is free of a surrounding reflective surface. Such improved efficiency of light output from a light emitter is achieved with the inventive lens positioned over the emitter and specifically designed for controlled refraction of light at a lens output surface. The inventive lens provides useful output of almost all of the emitted light, including light emitted at angles which previously resulted in the loss of such light. 
     The inventive lens includes an emitter-adjacent base end forming an opening to an inner cavity surrounding the emitter. An inner-cavity surface preferably includes an axis-adjacent first inner region, a second inner region spaced from the first inner region, and a middle inner region which joins the first and second regions. The axis-adjacent first inner region is configured for refracting emitter light rays away from the axis. The second inner region is configured for refracting emitter light rays toward the axis. The middle inner region is substantially cross-sectionally asymptotical to the axis-adjacent and base-adjacent regions. It is preferred that the middle inner region is positioned with respect to the emitter to refract light away from the axis by progressively lesser amounts at positions progressively closer to the base-adjacent inner region. 
     The lens further has an outer surface which includes output regions each configured for refracting the light from a corresponding one of the inner regions such that at the outer surface light from each inner region is refracted substantially without overlapping light rays from the other inner regions. 
     In preferred embodiments, the outer surface output regions include an axis-adjacent first output region, a second output region spaced from the first output region, and a middle output region joining the first and second output regions. The axis-adjacent first output region is configured for receiving emitter light rays from the axis-adjacent first inner region and preferably refracting them away from the axis. The second output region is configured for receiving emitter light rays from the second inner region and preferably refracting them substantially away from the axis. The middle output region is configured for receiving emitter light rays from the middle inner region and preferably refracting them substantially away from the axis. 
     It is preferred that the outer surface further includes a base-adjacent outer-surface region which extends from the second output region and is substantially free from receiving any emitter light. The base-adjacent outer-surface region is preferably substantially orthogonal to the emitter plane. 
     In some preferred embodiments, the second inner region terminates before reaching the emitter plane. In such embodiments, the inner-cavity surface further preferably includes a base-adjacent inner region extending from the second inner region. The base-adjacent inner region is preferably substantially orthogonal to the emitter plane. The light rays emitted between the second inner region and the emitter plane preferably pass through the base-adjacent inner region substantially free of refraction. 
     In the embodiments just described, the lens preferably further includes a peripheral inner surface receiving light from the base-adjacent inner region. It is highly preferred that the peripheral inner surface is configured for total internal reflection (TIR) of such light toward the emitter axis. The peripheral inner surface is preferably formed by a peripheral cavity extending from the base end. It is preferred that the peripheral inner surface is configured for TIR of the light rays before they enter the peripheral cavity. 
     In preferred embodiments of the present invention, the axis-adjacent first inner region is substantially cross-sectionally concave and the second inner region is substantially cross-sectionally convex. It is further preferred that the middle inner region is substantially cross-sectionally linear. In other words, the middle inner region is preferably of substantially truncated conical shape. 
     The inner-cavity surface may be substantially rotationally symmetrical. The outer surface may also be substantially rotationally symmetrical such that the lens has a substantially annular cross-section made substantially parallel to the emitter plane. 
     Another aspect of this invention is an optical member having a plurality of lenses of the type described above. Each lens is for distribution of light from a corresponding one of spaced light emitters. 
     In certain embodiments, each of the lenses has at least one layer of a polymeric material extending into the lens flange of such material and is spaced from the lens flanges that surround adjacent lenses. The optical member may be a one-piece member which includes a polymeric carrier portion surrounding the lenses, overlapping with and molded onto the lens flanges across such overlapping, and extending laterally therefrom. 
     In some embodiments, the at least one lens layer is of a first polymeric material and the carrier is of a second polymeric material. In some of such embodiments, the first polymeric material is an acrylic and the second polymeric material is a polycarbonate. 
     In some other embodiments, the at least one lens layer and the carrier are of the same polymeric material. 
     Another aspect of this invention is an LED light fixture including a heat-sink structure having a mounting surface, a plurality of spaced LED light sources at the mounting surface, and a plurality of the lenses described above, each lens in alignment with a corresponding one of the light sources. In some embodiments, the LED light fixture includes the optical member as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an enlarged perspective cross-sectional view of the inventive lens. 
         FIG. 2  is a greatly enlarged fragmentary cross-sectional side view of the lens of  FIG. 1  showing refraction of the emitter light by inner-cavity surface regions and a peripheral inner cavity surface. 
         FIG. 3  is an enlarged fragmentary cross-sectional side view of the lens of  FIG. 1  showing refraction of light emitted by the emitter at about the emitter axis and including a primary lens. 
         FIG. 4  is an enlarged fragmentary cross-sectional side view of the lens of  FIG. 1  showing refraction of light emitted at the emitter axis. 
         FIG. 5  is an enlarged fragmentary cross-sectional side view showing non-refracted light direction of light emitted as in  FIG. 3 . 
         FIG. 6  is an enlarged fragmentary cross-sectional view of the lens of  FIG. 1  showing refraction of light emitted from one site of the emitter axis. 
         FIG. 7  is an enlarged fragmentary cross-sectional view of the lens of  FIG. 1  showing refraction of light emitted from another side of the emitter axis. 
         FIG. 8  is a perspective view of an LED light fixture having two optical members with a plurality of lenses in accordance with this invention. 
         FIG. 9  is a perspective view of the optical member of the LED lighting fixture of  FIG. 8 . 
         FIG. 10  is an enlarged cross-sectional perspective view of one portion of the one-piece optical member of  FIG. 9 , illustrating one of the lenses. 
         FIG. 11  is a perspective view illustrating the plurality of the lenses. 
         FIG. 12  is a perspective view of another embodiment of an optical member according to the present invention, shown from the light-output side. 
         FIG. 13  is a perspective view of the optical member of  FIG. 12 , but showing its light-input side. 
         FIG. 14  is a plan view of the optical member of  FIG. 12 . 
         FIG. 15  is a side sectional view taken along section  15 - 15  as indicated in  FIG. 14 . 
         FIG. 16  is an end sectional view taken along section  16 - 16  as indicated in  FIG. 14 . 
         FIG. 17  is an enlarged perspective view of the lenses arranged as in the optical member of  FIG. 12  showing its light-input side. 
         FIG. 18  is a side elevation of yet another embodiment of a lens according to the present invention, schematically shown with rays representing the direction of light by the lens surfaces seen in a front-to-back plane extending through the emitter axis. 
         FIG. 19  is a side elevation of still another embodiment of the lens according to the present invention. 
         FIG. 20  is another side elevation of the lens of  FIG. 19  schematically showing rays representing the direction of light by the lens surfaces seen in a side-to-side plane extending through the emitter axis. 
         FIG. 21  is a side elevation of yet another embodiment of the lens according to the present invention. 
         FIGS. 22 and 22B  are another side elevation of the lens of  FIG. 21  schematically showing rays representing the direction of light by the lens surfaces seen in a side-to-side plane extending through the emitter axis. 
         FIG. 22A  is a fragment of the side elevation of  FIG. 22  schematically showing rays representing the direction of axis-adjacent light by the lens surfaces. 
         FIG. 23  is a side elevation of another embodiment of the lens according to the present invention. 
         FIGS. 24 and 25  are another side elevation of the lens of  FIG. 23  schematically showing rays representing the direction of light by the lens surfaces seen in a side-to-side plane extending through the emitter axis. 
         FIG. 26  is a perspective view from light output side of the lens of  FIG. 23  illustrating an outer-surface feature receiving axial light from the inner surface and further directing such light away from the axis to facilitate diffusion of high-intensity axial light. 
         FIG. 27  is a plan view of the lens of  FIG. 23  showing its light-output side. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIGS. 1-7  illustrate lens  10  which is a preferred embodiment of the invention. Lens  10  is for directing light from a light emitter  1  which has an emitter axis  2  and defines an emitter plane  3 . Lens  10  includes an emitter-adjacent base end  12  forming an opening to an inner cavity  14  surrounding emitter  1 . Cavity  14  defines a space between emitter  1  and an inner-cavity surface  20  such that emitter light goes through air to enter lens material at inner-cavity surface  20 . Because air and the lens material, which may be acrylic or other suitable material, have different refraction indexes resulting in bending of the light at inner-cavity surface  20 . 
       FIG. 2  best shows configuration of inner-cavity surface  20  which includes an axis-adjacent first inner region  21 , a second inner region  22  spaced from first inner region  21 , and a middle inner region  23  which joins first and second regions  21  and  22  and is substantially asymptotical to first and second inner regions  21  and  22 . 
       FIGS. 1 and 3  best show that lens  10  further has an outer surface  30  which includes an axis-adjacent first output region  31 , a second output region  32  spaced from axis-adjacent first output region  31 , and a middle output region  33  joining first and second output regions  31  and  32 . Each of output regions  31 ,  32  and  33  is configured for refracting the light from a corresponding one of inner regions  21 ,  22  and  23 . Therefore, at outer surface  30  light from each inner region  21 ,  22  or  23  is refracted substantially without overlapping light rays from the other inner regions. 
     As also seen in  FIG. 3 , outer surface  30  further includes a base-adjacent outer-surface region  34  which extends from second output region  32  and is substantially free from receiving any emitter light. Base-adjacent outer-surface region  34  is substantially orthogonal to emitter plane  3 . It should be appreciated that, since the base-adjacent outer-surface substantially does not participate in distribution of emitter light, it may have any configuration dictated by positioning and mounting of the lens or other factors such as material or space conservation. 
       FIG. 2  best illustrates that axis-adjacent first inner region  21  is configured for refracting emitter light rays  210  which pass through axis-adjacent first inner region  21  away from axis  2 . This provides a broader distribution of the light emitted about axis and allows to enlarge the size of first output region  31  to achieve better refraction of light  210  outside lens  10 . Light  210  received by the axis-adjacent first inner region  21  has the highest intensity. This is because typically the highest illumination intensity of the emitter light is concentrated about axis  2 . By refracting light  210  away from axis  2 , axis-adjacent inner region  21  allows for dispersion of such light  210  over a larger area. This improves uniformity of illumination intensity and substantially decreases a so-called “hot-spot” effect in a plot of illumination intensity distribution.  FIG. 2  further illustrates that axis-adjacent first inner region  21  is substantially cross-sectionally concave. 
     As further seen in  FIG. 2 , second inner region  22  is configured for refracting emitter light rays toward the axis. It is seen in  FIG. 2  that second inner region  22  is substantially cross-sectionally convex. Second inner region moves light  220 , which mostly includes light emitted within about 30° from emitter plane  3 , away from base-adjacent outer-surface region  34 . As can be seen in  FIG. 1 , base-adjacent outer-surface region  34  is surrounded by structures  50  which may serve to secure lens  10  with respect to emitter  1  or to be a shield blocking emitter light from going in an undesirable direction. As a result, any light that would arrive at the base-adjacent region  34  would be blocked by such structures  50  and would be eventually lost. In prior lenses, because some of the light was lost, to meet goals of desired polar candela plots, the outer surface had to be designed to bend some of the axis-adjacent light to the sides to provide required illumination. By refracting light  220  toward emitter axis  2 , this light is received by outer surface  30  at output region  32  which not only transmits light  220  out of lens  10  but also further refracts light  220  in a desired direction, i.e., away from emitter axis  2 , as shown in  FIG. 3 . Therefore, since light  220  provides desired illumination at the sides of desired illumination patterns, there is no need for bending axis adjacent light  210  for such purpose. 
     In prior lenses the space between the emitter and inner lens surface was filled with an optical gel such that the emitter light passed therethrough without refraction and arrived to the outer surface at the same angle as emitted. In such prior lenses, the outer surface was the only vehicle for light refraction. When compared to such prior lenses, the configuration of outer surface  30  of lens  10  is unexpectedly substantially simpler then of those prior lenses. In the prior lenses, light arrived at the outer surface at substantially broad range of angles. Thus, almost all these angles had to be taken into account in forming that prior outer surface for refraction of light in a desirable direction. In lens  10 , the direction of the majority of emitter light is initially substantially controlled by inner surface  20  and light from one of inner regions is received substantially by only a corresponding one output region of outer surface  30 . As a result, each one output region of outer surface  30  receives light which arrives at substantially narrow sector of angles. This, coupled with improved efficiency which eliminates the need for bending axis-adjacent light for side illumination, simplifies the configuration of that output region of outer surface  30  for refraction of such light in a desired direction and, therefore, decreases a probability of an irregularity impact on the light-output direction. 
     It can be seen in  FIG. 2  that middle inner region  23  is positioned with respect to emitter  1  to refract light away from axis  2  by progressively lesser amounts at positions progressively closer to the base-adjacent inner region. In some cases, middle region  23  may be configured and positioned to allow emitter light to pass therethrough with substantially no refraction. As best shown in  FIG. 2 , middle inner region  23  is substantially cross-sectionally linear. In other words, middle inner region  23  is of substantially truncated conical shape. 
     As best seen in  FIG. 3 , axis-adjacent first output region  31  is configured for receiving emitter light rays  210  from axis-adjacent first inner region  21  and further refracting them away from axis  2 . Second output region  32  is configured for receiving emitter light rays  220  from second inner region  22  and refracting them substantially away from axis  22 . Middle output region  33  is configured for receiving emitter light rays  230  from middle inner region  23  and refracting them substantially away from axis  2 . 
     It should be understood that shown configuration of outer surface  30  is just an exemplary configuration. Outer surface  30  can have other configurations which would be dictated by an intended illumination pattern. 
     As further seen in  FIGS. 1-7  second inner region  22  terminates before reaching emitter plane  3 . Inner-cavity surface  20  further includes a base-adjacent inner region  24  extending from second inner region  22 . Base-adjacent inner region  24  is substantially orthogonal to emitter plane  3  and is oriented for substantially non-refracted passing through of light  240  emitted between second inner region  22  and emitter plane  3 . 
     Lens  10  further includes a peripheral inner surface  40  which receives light  240  from base-adjacent inner region  24 . Peripheral inner surface  40  is configured for total internal reflection (TIR) of light  240  toward emitter axis  2 . Thus, light  240  is retrieved from lens  10  for useful illumination rather than being lost. Peripheral inner surface  40  is formed by a peripheral cavity  41  extending from base end  12 . As best seen in  FIG. 2 , peripheral inner surface  41  is configured for TIR of light rays  240  before they enter peripheral cavity  41 . 
       FIG. 1  shows inner-cavity surface  20  substantially rotationally symmetrical. Peripheral cavity  41  and peripheral inner surface  40  are also substantially rotationally symmetrical. The embodiment illustrated in  FIG. 1  further shows outer surface  30  as substantially rotationally symmetrical such that lens  10  has a substantially annular cross-section in a plane substantially parallel to emitter plane  3 . Alternatively, the inner and outer surfaces can have shapes that result in substantially oval or ovoid cross-section made in a plane substantially parallel to the emitter plane. In other words, these surfaces may have symmetries other than rotational. It should be further appreciated that, depending on the intended illumination pattern, the inventive lens may be shaped without a symmetry and have asymmetrical surfaces. 
       FIGS. 8-17  illustrate an LED lighting fixture  110  in accordance with the present invention. LED light fixture  110  includes a heat-sink structure  112  that has a mounting surface  112 A on which a circuit board  114  is mounted. Circuit board  114  has a plurality of LED light sources  114 A spaced thereon. A one-piece optical member  116  is positioned over circuit board  114  and has a plurality of secondary lenses  120  thereon, each in alignment with a corresponding one of light sources  114 A. 
       FIG. 10  best illustrates that each of lenses  120  of one-piece optical member  116  has a layer  122  of polymeric material which extends into a lens flange  124  of such material and is spaced from lens flanges  124  that surround adjacent lenses  120 .  FIG. 9  shows that one-piece optical member  116  also has a polymeric carrier portion  126  surrounding lenses  120 . As also seen in  FIG. 10 , carrier portion  126  overlaps with and is molded onto to lens flanges  124  across such overlapping, and carrier portion  126  extends laterally therefrom to a peripheral edge portion  128 . 
     The polymeric material of lens  120 , i.e., the material of layer  122  and flange  124 , is an acrylic, while the polymeric material of carrier portion  126  is a polycarbonate. A wide variety of optical-grade acrylics can be used, and are available from various sources, including: Mitsubishi Rayon America, Inc.; Arkema Group; and Evonik Cyro LLC. Likewise, a wide variety of polycarbonate materials can be used, and are available from various sources, such as Bayer and Sabic. 
       FIG. 11  illustrates the positioning of secondary lenses  120  as placed in injection-molding apparatus (not shown). After such placement, carrier portion  126  is injection molded onto lens flanges  124  to form one-piece optical member  116 . As already indicated, carrier portion  126  surrounds lenses  120  and overlaps and is molded onto to lens flanges  124 . 
       FIGS. 12-17  illustrate aspects of an alternative one-piece optical member  116 A which has three lenses  120  and a carrier portion  126 A. The only significant difference between one-piece optical members  116  and  116 A is the number of lenses. 
       FIG. 17 , like  FIG. 11 , illustrates the positioning of secondary lenses  120  as placed in injection-molding apparatus. Accurate placement into the injection-molding apparatus is facilitated by indexing features in the form of posts  130  (see  FIGS. 12, 14 and 15 ) which extend from lens flange  124  and mate with corresponding recesses in the mold. ( FIGS. 9 and 10  also show such indexing feature.) 
       FIGS. 18-24  shows lenses  120 A,  120 B,  120 C and  120 D which are exemplary embodiments of the lens according to the present invention. Each of these lenses has inner surface  20 A-D which defines inner cavity  14 A-D and includes a substantially cross-sectionally convex inner region  22 A-D along an open end of inner cavity  14 A-D. As seen in each of  FIGS. 18, 20   22  and  24 , convex region  22 A-D is configured for refracting emitter light rays toward emitter axis  2 .  FIGS. 18-24  also show a lens flange  60 A-D surrounding lens  120 A-D and having an outer flange surface  61 A-D extending radially outwardly from lens outer surface  30 A-D at positions axially spaced from light emitter  1 . It is seen in  FIGS. 18, 20, 22 and 24  that convex inner region  22 A-D is configured to refract emitter light to the outer surface such that outer flange surface  61 A-D is substantially free from receiving any emitter light. 
       FIGS. 18-24  also show that inner surface  20 A-D has a substantially cross-sectionally linear inner region  23 A-D which joins substantially cross-sectionally convex inner region  22 A-D and extends therefrom toward emitter axis  1 . 
       FIGS. 23 and 24  show that, in lens  120 D, substantially cross-sectionally linear inner region  23 D forms a cone-shaped inner surface portion at the closed end of inner cavity  14 D. It is further seen in  FIG. 24  that such cone-shaped inner surface portion serves to refract axis-adjacent emitter light away from the axis. 
     While the principles of the invention have been shown and described in connection with specific embodiments, it is to be understood that such embodiments are by way of example and are not limiting.