Patent Publication Number: US-9845937-B2

Title: Field light control system for LED luminaires

Description:
FIELD 
     The present disclosure is related to an LED light system, and more particularly, to an optical assembly to control a light pattern of a light beam for a spot or narrow flood LED-type light system. 
     BACKGROUND 
     Traditional light sources include incandescent, high-intensity discharge (HID), and compact-fluorescent (CFL) light sources, all of which emit light in all directions (i.e., non-directional light beam). To direct the non-directional light beam down from and out of a recessed fixture, lighting manufacturers have traditionally designed reflectors using a parabolic shape, which is intended to focus the non-directional light beam toward an illuminated target (e.g., a floor or wall surface). Rapid advancements in light-emitting diode (“LED”) technology have caused manufacturers to replace the traditional light sources with LED light sources, which are inherently directional light sources. The manufacturers have continued using traditional reflectors (e.g., parabolic-shaped reflectors) to minimize glare; however, LED light sources are inherently less diffuse emitters than these traditional light sources resulting in additional lighting designs concerns. For example, the combination of LED light sources with a traditional reflector may produce a light beam with a light pattern having a harsh edge between a center beam light area and a peripheral light area (surrounding the center beam light area) of the light beam, which is aesthetically unappealing in spot or narrow flood light applications. 
     SUMMARY 
     In an LED light system of the spot or narrow flood variety, and especially for the interior lighting variety, it is desirable that the LED light system produces a light beam with a light pattern that provides a smooth or smoother transition, without harsh edges, between a center beam light area and a peripheral light area (surrounding the center beam light area) of the light beam. It is also desirable that the peripheral light area of the light beam is softened and blended into a surrounding darkness, while maintaining a center beam light area with a high Center Beam Candlepower. It is further desirable that this smooth transition be accomplished in a cost-efficient manner and preferably results in a broader area of illumination. To address these and other issues, an improved and cost-efficient optical assembly is provided for a LED light system, in which a light diffuser with a central opening is suspended inside of the reflector to redistribute light received from the LED light source. The light diffuser redistributes light to soften and broaden out the peripheral light area, thereby providing a smooth or smoother transition between the center beam and peripheral light areas of the light beam. At the same time, the central opening of the light diffuser allows light from the LED light source to pass directly therethrough to provide the center beam light area with a sufficiently high light intensity (e.g., a bright center beam with a high Center Beam Candlepower). 
     In accordance with an embodiment, the LED light system includes an LED light source, an optical assembly and an optic housing (e.g., a housing or mounting frame) to house the LED light source and the optical assembly. The optical assembly includes a conical reflector with a narrow open top and a wide open bottom, a light diffuser, an optic holder to suspend the light diffuser inside of the conical reflector, and an optical medium. The optic holder is mounted to the narrow open top of the reflector, and the optical medium is positioned over or across the wide open bottom of the reflector. The light diffuser has an annular shape with a central opening, and is formed of a light diffusing material to diffuse light received from the LED light source. The optic holder can be designed with a shape and a light-transmissive material (e.g., a light transmitting material) to maximize an overall light output efficiency of the LED light system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description of the various exemplary embodiments is explained in conjunction with the appended drawings, in which: 
         FIG. 1  illustrates a sectional view of an LED light system with an optical assembly which produces a light beam with a light pattern having a smooth transition, without harsh edges, between a center beam light area and a peripheral light area surrounding the center beam light area, in accordance with an exemplary embodiment of the present disclosure. 
         FIG. 2  illustrates an exploded view of the optical assembly of  FIG. 1 . 
         FIG. 3  illustrates a portion of the LED light system of  FIG. 1 , showing an enlarged sectional view of the LED light source, the optical assembly and the media cartridge when assembled into an optic housing of the LED light system. 
         FIG. 4  illustrates another sectional view of the optical assembly, which shows an exemplary relationship between an LED light source and optical components, such as a light diffuser and a reflector, of the LED light system of  FIG. 1 . 
         FIG. 5A  illustrates an example of a simulated light pattern distribution and intensity plot for a light beam produced with an optical assembly having only a primary optic, such as a reflector. 
         FIG. 5B  illustrates an example of a simulated light pattern distribution and intensity plot for a light beam produced with an optical assembly having only a primary optic (such as a reflector) with an optical medium. 
         FIG. 5C  illustrates an example of a simulated light pattern distribution and intensity plot for a light beam produced with an optical assembly having a primary optic (such as a reflector), secondary optic (such as a light diffuser) and an optical medium, as in the example LED light system of  FIG. 1 . 
         FIG. 6A  illustrates an example of a light pattern distribution for a light beam produced with an optical assembly having only a primary optic, such as a reflector. 
         FIG. 6B  illustrates an example of a light pattern distribution for a light beam produced with an optical assembly having only a primary optic (such as a reflector), and an optical medium. 
         FIG. 6C  illustrates an example of a light pattern distribution for a light beam produced with an optical assembly having a primary optic (such as a reflector), a secondary optic (such as a light diffuser), and an optical medium, as in the example LED light system of  FIG. 1 . 
         FIG. 7  illustrates another sectional view of the optical assembly of  FIG. 1 , which shows the various exemplary light rays passing through or acted upon by the optical components of the optical assembly, such as the reflector and the light diffuser. 
     
    
    
     DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS 
     As an initial matter, it will be appreciated that the development of an actual, real commercial application incorporating aspects of the disclosed embodiments will require many implementation specific decisions to achieve the developer&#39;s ultimate goal for the commercial embodiment. Such implementation specific decisions may include, and likely are not limited to, compliance with system related, business related, government related and other constraints, which may vary by specific implementation, location and from time to time. While a developer&#39;s efforts might be complex and time consuming in an absolute sense, such efforts would nevertheless be a routine undertaking for those of skill in this art having the benefit of this disclosure. 
     It should also be understood that the embodiments disclosed and taught herein are susceptible to numerous and various modifications and alternative forms. Thus, the use of a singular term, such as, but not limited to, “a” and the like, is not intended as limiting of the number of items. Similarly, any relational terms, such as, but not limited to, “top,” “bottom,” “left,” “right,” “upper,” “lower,” “down,” “up,” “side,” and the like, used in the written description are for clarity in specific reference to the drawings and are not intended to limit the scope of the invention. 
     Before describing the various exemplary embodiments in the present disclosure, a few terms are also discussed below for the explanatory purposes. 
     A “beam angle” defines the light pattern around the light beam&#39;s center out to the angle where the light (luminous) intensity is half that of the maximum luminous intensity. 
     A “Center Beam Candlepower” is the light intensity at the center of the light beam such as for a reflector-type light system. 
     A “field angle” is the angular dimension of a cone of light from a light system, which encompasses the central part of the light beam out to the angle where the light intensity is 10% of maximum. The field angle is useful in describing a light output of a light system, particularly where the light output begins to fade into the surrounding environment (e.g., darkness). 
     A “field light” is the light output of a light system over or across the field angle, or in other words, up until the light output has fallen to 10% of maximum light intensity. 
     Turning to the figures,  FIG. 1  illustrates an LED light system  10  including an LED light source  30  (e.g., an LED light engine on a PCB) and an optical assembly  100 , which are both housed in a cavity  22  of an optic housing  20  through an open end  26 . The optical assembly  100  is supported and connected to the optic housing  20 , using a media cartridge  50 . The LED light system  10  produces a light beam with a light pattern having a center beam light area and a peripheral light beam area surrounding the center beam light area. The LED light system  10  can be a downlight of a spot or narrow flood variety. 
     The optical assembly  100  includes a reflector  110  (also referred to as “primary optic”), a light diffuser  130  (also referred to as “secondary optic”) and an optical medium  160 . The light diffuser  130  is suspended inside of the reflector  110  by an optic holder  140 , and is configured with a predetermined size and shape and at a predetermined distance from the LED light source  30  to redistribute light, such as the field light. Specifically, the light diffuser  130  redistributes light to soften and broaden out the peripheral light area, and thus, to smooth out a transition between the center beam light area and the peripheral light area of the light beam. The use of the light diffuser  110  provides a simple, cost-efficient optical assembly, which does not require costly and complex optical components, such as additional reflectors, to provide a light beam with a light pattern having a smooth or smoother transition between the center beam light area and the peripheral light area. A detailed description of the various components of the optical assembly  100  will be described in greater detail below with reference to both  FIGS. 2 and 3 , which show an exploded view and an enlarged assembled view of the optical assembly  100 , respectively. 
     As shown in  FIGS. 2 and 3 , the reflector  110  is a conical or cone-shaped reflector (e.g., a cone reflector) having a narrow open top  112  and a wide open bottom  114 . The reflector  110  also includes a wall  116  which extends continuously from a top to a bottom of the reflector  110  and has a continuous interior reflective surface  118 . The narrow open top  112  has a top opening  120 , and the wide open bottom  114  has a bottom opening  122 . The narrow open top  112  includes twist-on tabs  124 , which extend into the top opening  120 . The twist-on tabs  124  are part of a twist-on assembly, (e.g., a tab and slot assembly), to detachably connect or mount the optic holder  140  to the reflector  110 . The reflector  110  can, for example, be an aluminum reflector (e.g., an Alzac processed aluminum reflector) or a prismatic reflector (e.g., an acrylic prismatic reflector). 
     The light diffuser  130  has an annular shape with a central opening  132  and a disk-shaped portion  134 . The disk-shaped portion  134  is formed of a light diffusing material to diffuse light. The light diffusing material can include polycarbonate (e.g., polycarbonate film or lens), blasted glass, textured acrylic, volumetric diffuser, or any suitable material with light diffusing properties. The light diffuser  130  is suspended inside of the reflector  110  by the optic holder  140 , which aligns the light diffuser  130  along an optical axis, in this example, a centerline of the optical assembly  100 . The light diffuser  130  is used to control light distribution, such as of the field light, to reduce a harsh edge, and thus, to smoothen a transition between the center beam light area and the peripheral light area bordering and surrounding the center beam light area of the light beam produced by the LED light system  10 . At the same time, the central opening  132  of the light diffuser  130  allows light from the LED light source  30  to pass directly therethrough to produce a light beam with the center beam light area having a sufficiently high light intensity (e.g., a bright center beam with a high Center Beam Candlepower). 
     The optic holder  140  includes an upper ring  142  with a central upper opening  150 , a lower ring  144  with a central lower opening  152 , and a plurality of spaced-apart supports  146  (e.g., vertical supports) connected between the upper and lower rings  142 ,  144 . The optical holder  140  also includes a plurality of spaced-apart windows  154  (e.g., openings) to allow light, such as from a light source (e.g., the LED light source  30  in  FIG. 1 ), to pass directly therethrough. The supports  146  are designed with a height to establish a desired focal length for the optic diffuser  130 . The components of the optic holder  140  are formed of a light-transmissive material, e.g., a light transmitting material, to allow light to be transmitted therethrough. The light-transmissive material can include polycarbonate, acrylic, silicone or other materials which are preferably resilient and able to allow light transmission therethrough (e.g., optically transparent). The optical holder  140  can be designed with a structure (e.g., windows) and materials (e.g., light-transmissive materials) to avoid blocking the light from the reflector  110 , and to maximize an overall light output efficiency of the LED light system  10 , e.g., greater than 70% efficient or preferably between 80% to 85% efficient. 
     As further shown in  FIGS. 2 and 3 , the optic holder  140  further includes a snap-fit assembly on the lower ring  144  to detachably connect and support the light diffuser  130 . In this example, the snap-fit assembly comprises a plurality of resilient spaced-apart hooks  148 , which are configured to support the light diffuser  130  from below and to detachably engage a periphery of the light diffuser  130 . The upper ring  142  has a diameter, which is larger than the opening  120  of the narrow open top  112  of the reflector  110 . The upper ring  142  also includes a plurality of spaced-apart slots  156  (e.g., slots or grooves) proximate a bottom side of the upper ring  142 . 
     To assemble the light diffuser  130  into the reflector  110 , the light diffuser  130  is connected to the lower ring  144  of the optic holder  140  via the hooks  148 . The lower ring  144  of the optic holder  140  is then inserted along with the light diffuser  130  through the top opening  120  of the narrow open top  112  of the reflector  110  until the upper ring  142  abuts against the narrow open top  120 . Thereafter, the optic holder  140  is twisted until the tabs  124  of the reflector  110  engage corresponding slots  156  of the optic holder  140 . 
     The optical medium  160  is arranged over or across the bottom opening  122  of the wide open bottom  114  of the reflector  110 . In this example, the optical medium  160  has a circular shape, and has plurality of spaced-apart notches  162  along an edge of the medium. The optical medium  160  can be formed of a light diffusing material, such as glass or polycarbonate (e.g., a polycarbonate lens) which can have a light diffusing surface. The optical medium  160  can be used to further soften and enhance a continuity of the light pattern of the light beam produced by the LED light system  10 . 
     The media cartridge  50  is provided to support and secure the components of the optical assembly  100  inside the cavity  22  of the optic housing  20 . In this example, the media cartridge  50  has a body  270  with a cylindrical shape. The body  270  of the media cartridge  50  includes a top  272  and an opposite bottom  276 . The top  272  includes a top opening  274  to receive the optical assembly  100 . The bottom  276  includes a bottom opening  278  through which light is outputted. The media cartridge  50  also includes an interior rim  280  (e.g., a rim, lip or flange), a plurality of spaced-apart interior stops  282  and one or more exterior grooves  284 . The interior rim  280  is used to support the optical medium  160  and the other components of the optical assembly  100 . The interior stops  282  are parallel spaced-apart vertical protrusions, which are configured to engage respective notches  162  of the optical medium  160  and act as a guide when assembling the optical medium  160  into the media cartridge  50 . The interior stops  282  prevent horizontal or lateral movement of the optical medium  160 , when assembled onto the media cartridge  50 . The interior stops  282  can also be used to receive spring clips (not shown), which can be connected to the optic housing  20  and help to guide and align the optical assembly  100  in the optic housing  20 . 
     Once the optical assembly  100  is assembled onto the media cartridge  50 , the media cartridge  50  can be inserted through an open end  26  (e.g., an open bottom) of the optic housing  20 . The groove(s)  284  of the media cartridge  50  are aligned and engaged with corresponding tab(s)  24  of the optic housing  20  to secure the media cartridge  50 , along with the optical assembly  100 , to the optic housing  20  of the LED light system  10 . As shown in  FIG. 3 , the LED light source  30  and the optical components of the optical assembly  100  are arranged along an optical axis, which in this example is a centerline axis of the optical assembly  100  and the LED light system  10 . 
       FIG. 4  illustrates another sectional view of an example of the optical assembly  100 , which shows an exemplary relationship between the LED light source  30  and optical components, such as the reflector  110  and the light diffuser  130  of the optical assembly  100 . As shown, in this example, the light emitting surface of the LED light source  30  is substantially parallel to the light diffusing surface of the light diffuser  130 . For the purposes of explanation, various lines and angles are drawn (see e.g., right-angled triangles) to specify the relationship between the LED light source  30 , the reflector  110  and the light diffuser  130 . For example, to reduce the harsh edge and to provide a smooth transition between the center beam light area and the peripheral area of the light beam, the LED light source  30 , the reflector  110  and the light diffuser  130  can be configured in size, shape and distance to satisfy the following requirements as set forth in equations &lt;1&gt; and &lt;2&gt; below:
 
 d 1= H *tan(θ), and  &lt;1&gt;
 
 d 2= H *tan(β),  &lt;2&gt;
 
where d1 is a radius of the central opening of the light diffuser  130 ,
 
     d2 is a radius of the light diffuser  110 , 
     H is a height (e.g., distance or focal length) from the LED light source  30  to the light diffuser  130 , 
     θ is an angle between a centerline from the LED light source  30  to the light diffuser and a line from a center of the LED light source  30  to a perimeter of the central opening  134 , and 
     β is an angle between the centerline from the LED light source  30  to the light diffuser  130  and a line from a center of the LED light source  30  to a perimeter of the light diffuser  130 . 
     The above-note relationship is provided as an example. It should be understood that the size, shape and position of the light diffuser  110  can be configured according to the characteristics of the LED light source and the reflector, such as the type, size, shape, position and output characteristics. 
     To evaluate the design of the optical assembly, such as in  FIGS. 1-4 , data was collected based on simulations and actual experiments of different optical configurations for a variety of optical assemblies (for an LED light system), which include (1) only a primary optic (e.g., in  FIGS. 5A and 6A ), (2) only a primary optic and an optical medium (e.g., in  FIGS. 5B and 6B ), and (3) a primary optic, secondary optic and an optical medium (e.g., in  FIGS. 5C and 6C ). In the simulated and experimented optical assemblies, the primary optic was a conical reflector, and the secondary optic was an annular disk-shaped light diffuser that was suspended inside of the reflector along the optical axis. Based on these simulations and experiments, it was shown that the use of a secondary optic, such as an annular disk-shaped light diffuser, inside of a reflector provided substantial improvement in smoothing a transition between the center beam light area and the peripheral area of the light pattern of the resultant light beam, while maintaining sufficient light output efficiency (e.g., greater than 70%, preferably between 80% and 85%) and a bright center beam. The figures, such as  FIGS. 5A, 5B, 5C, 6A, 6B and 6C , will be described below in greater detail. 
       FIG. 5A  illustrates an example of a simulated light pattern distribution  500  and an intensity plot  510  for a light beam produced by an optical assembly with only a primary optic, such as a reflector. The light pattern distribution  500  shows a center beam light area  502  and a peripheral light area  504  bordering and surrounding the center beam light area  502  in relations to horizontal (X) and vertical (Y) positions. The intensity plot  510  is a graph of light intensity versus degrees from center corresponding to the light pattern shown in the light pattern distribution  500 . In the intensity plot  510 , there is shown a peak light intensity  512  of a center beam forming the center beam light area  502 , and a light intensity  514  of the peripheral light area  504 . As shown by  FIG. 5A , the use of an optical assembly with only a reflector produces a light beam with harsh edges or transition between the center beam light area  502  and the peripheral light area  504 . This is similarly shown in the example light pattern distribution  600  of  FIG. 6A  with a center beam light area  602  and a peripheral light area  604 , which were also produced by an LED light system with an optical assembly having only a reflector. As shown in both  FIGS. 5A and 6A , the peripheral light areas  504  and  604 , respectively, do not blend well or fade into the surrounding darkness. 
       FIG. 5B  illustrates an example of a simulated light pattern distribution  530  and an intensity plot  540  for a light beam produced by an optical assembly with only a primary optic, such as a reflector, and an optical medium. The light pattern distribution  530  shows a center beam light area  532  and a peripheral light area  534  bordering and surrounding the center beam light area  532  in relations to horizontal (X) and vertical (Y) positions. The intensity plot  540  is a graph of light intensity versus degrees from center corresponding to the light pattern shown in the light pattern distribution  530 . In the intensity plot  540 , there is shown a peak light intensity  542  of a center beam forming the center beam light area  532 , and a light intensity  544  of the peripheral light area  534 . As shown by  FIG. 5B , the use of an optical assembly with only a reflector and an optical medium also produces a light beam with harsh edges or transition between the center beam light area  532  and the peripheral light area  534 . This is similarly shown in the example light pattern distribution  640  of  FIG. 6B  with a center beam light area  642  and a peripheral light area  644 , which were produced by an LED light system with an optical assembly having only a reflector and an optical medium. As shown in both  FIGS. 5B and 6B , the peripheral light areas  534  and  644 , respectively, do not blend well or fade into the surrounding darkness. 
       FIG. 5C  illustrates an example of a simulated light pattern distribution  560  and an intensity plot  570  for a light beam produced by an optical assembly including a primary optic (e.g., a reflector), a secondary optic (e.g., an annular disk-shaped light diffuser) suspended inside of the primary optic, and an optical medium. The light pattern distribution  560  shows a center beam light area  562  and a peripheral light area  564  bordering and surrounding the center beam light area  562  in relations to horizontal (X) and vertical (Y) positions. The intensity plot  570  is a graph of light intensity versus degrees from center corresponding to the light pattern shown in the light pattern distribution  560 . In the intensity plot  570 , there is shown a peak light intensity  572  of a center beam forming the center beam light area  562 , and a light intensity  574  of the peripheral light area  564 . As shown by  FIG. 5C , the use of an optical assembly with the light diffuser (along with the reflector and the optical medium) produces an improved light beam with a smoother transition between the center beam light area  562  and the peripheral light area  564  in comparison to those shown in  FIGS. 5A, 5B, 6A and 6B . In this example, the light intensity of the light continuously decreases from the center out towards the periphery of the light pattern of the light beam. For example, the light intensity of the light pattern from the light beam continuously decreases from the peak intensity  572  in the center beam light area  562  outwards across the peripheral light area  564 . This is similarly shown in the example light pattern distribution  680  of  FIG. 6C  with a center beam light area  682  and a peripheral light area  684 , which were also produced by an LED light system with an optical assembly having a reflector, an annular disk-shaped light diffuser, and an optical medium. As shown in both  FIGS. 5C and 6C , the peripheral light areas  564  and  684 , respectively, have been softened by the redistribution of light using the light diffuser, and blend well or fade into the surrounding darkness. The resulting light pattern is aesthetically pleasing particularly for spot or narrow flood light applications. 
       FIG. 7  illustrates another sectional view of an example of the optical assembly  100 , which shows the directionality of various example light rays  710 ,  720  and  730  passing through or reflected by the reflector  110  of the LED light system  10  of  FIG. 1 . As shown in  FIG. 7 , some of the light produced by the LED light source  30  is diffused by the light diffuser  130 , as shown by the light rays  710 . The redistribution of light, as shown by the diffused light rays  710 , soften the peripheral light area, and thus, provide a smooth or smoother transition, without harsh edges, between the center beam light area and the peripheral light area, such as previously shown in the examples of  FIGS. 5C and 6C . 
     As further shown in  FIG. 7 , a significant amount the light produced by the LED light source  30  passes directly through the central opening  134  as light rays  720  along the optical axis, without being diffused, to produce the center beam light area of the light beam. Some of the light produced by the LED light source  30  also passes through the windows  154  and the light-transmissive material of the optic holder  140  as light rays  730 . The light rays  730  are reflected by the reflector  110  to contribute to the center beam light area of the light beam. 
     It should be understood that the optical assembly  100 , as described with reference to  FIGS. 1-7 , is provided as an example. The size, shape and materials of the various components of the optical assembly can be modified according to the lighting application. Furthermore, the LED light system can employ other types of mechanical connectors (e.g., fasteners, screws, snap-fits, etc.) to connect the optic holder to the reflector of the LED light system, as well as to connector the other components together of the LED light system. 
     Words of degree, such as “about”, “substantially”, and the like are used herein in the sense of “at, or nearly at, when given the manufacturing, design, and material tolerances inherent in the stated circumstances” and are used to prevent the unscrupulous infringer from unfairly taking advantage of the invention disclosure where exact or absolute figures and operational or structural relationships are stated as an aid to understanding the invention. 
     While particular embodiments and applications of the present disclosure have been illustrated and described, it is to be understood that the present disclosure is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations can be apparent from the foregoing descriptions without departing from the invention.