Patent Publication Number: US-2012033430-A1

Title: Optical lens and lighting apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2010-0076301 filed on Aug. 9, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical lens and a lighting apparatus using the same, and more particularly, to a lighting apparatus having a light distribution curve suitable for use in lighting having a wide range of uses by employing an optical lens having an improved orientation angle. 
     2. Description of the Related Art 
     In general, a light emitting diode (LED), a kind of semiconductor light source, is a semiconductor device capable of generating light of various colors due to the recombination of electrons and electron holes at the junction between a p-type semiconductor and an n-type semiconductor, when current is applied thereto. 
     Demand for this light emitting diode has been continuously increasing, since the light emitting diode has various advantages, such as long lifespan, low power consumption, superior initial driving characteristics, high vibration resistance, and the like, as compared to a filament-based light source. In particular, a group III-nitride semiconductor capable of emitting blue light having a short wavelength has recently come to prominence. 
     Recently, there has been an attempt at replacing a lighting apparatus in the related art, such as an incandescent lamp or a fluorescent lamp by using the light emitting diode. However, in the case of the light emitting diode, light is emitted in a particular direction rather than being uniformly emitted in all directions, and, in general, an orientation angle is in the range of approximately 120°. These light contribution characteristics of the light emitting diode show sufficient differences as compared to an incandescent lamp or a fluorescent lamp emitting light in all directions, whereby the light emitting diode is limited to be used as a lighting apparatus having a wide range of uses. Accordingly, in the case of a lighting apparatus using the light emitting diode, a design solution capable of extending the application range of a lighting apparatus using the light emitting diode by using a lens controlling direction of emitted light has been required. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides an optical lens having a shape capable of improving an orientation angle of a light source, and further provides a lighting apparatus having a light distribution curve suitable for use in lighting having a wide range of uses by employing this optical lens. 
     According to an aspect of the present invention, there is provided an optical lens, including: an incidence part provided as a light incident area and including a micro lens array formed on at least a partial region of a surface thereof; a reflection part spaced apart from the incidence part by a predetermined distance and reflecting at least a certain amount of light having passed through the incidence part; and a side surface part connecting the incidence part and the reflection part and transmitting the certain amount of light reflected by the reflection part. 
     The micro lens array may refract at least a certain amount of light incident on the incidence part at an angle at which the light is totally reflected by the reflection part. 
     The incidence part and the reflection part maybe planes parallel with each other. 
     The reflection part may have a width greater than that of the incidence part. 
     The incidence part and the reflection part may have round shapes. 
     The side surface part may have a curved surface shape projecting outwardly. 
     The micro lens array may be formed of micro lenses, each having a hemispherical shape projecting from a lower surface of the incidence part. 
     The micro lens array may include at least one micro lens having a hemispherical, conic, triangular pyramidal, quadrangular pyramidal or randomly scattered shape. 
     The optical lens is made of at least one of polycarbonate and acryl. 
     According to another aspect of the present invention, there is provided a lighting appratus, including: a light source; and an optical lens including an incidence part provided as a light incident area and including a micro lens array formed on at least a partial region of a surface thereof; a reflection part spaced apart from the incidence part by a predetermined distance and reflecting at least a certain amount of light having passed through the incidence part; and a side surface part connecting the incidence part and the reflection part and transmitting the certain amount of light reflected by the reflection part. 
     The micro lens array may refract at least a certain amount of light incident on the incidence part at an angle at which the light is totally reflected by the reflection part. 
     The incidence part and the reflection part may be planes parallel with each other. 
     The reflection part may have a width greater than that of the incidence part. 
     The incidence part and the reflection part may have round shapes. 
     A ratio of a width of the incidence part to a width of a light source may be within a range between 1.8 and 3.2. 
     A ratio of a width of the reflection part to the width of the light source may be within a range between 3 and 4.2. 
     The side surface part may have a curved surface shape projecting outwardly. 
     A ratio of a distance between the reflection part and the incidence part to the width of the light source may be within a range between 0.46 and 0.9. 
     The micro les array may have a plurality of micro lenses, each having a hemispherical shape projecting from a lower surface of the incidence part. 
     In the micro les array, an interval between the micro lenses may be uniform. 
     A ratio of the interval between the micro lenses to the width of the light source maybe within a range of 0.08 or more. 
     A ratio of a radius of the micro lenses to the interval between the micro lenses may be within a range between 0.48 and 0.62. 
     The optical lens may be made of at least one of polycarbonate and acryl. 
     A formation area of the micro lens array may be greater than an area corresponding to the light source. 
     The lighting appratus may further include a heat dissipating structure disposed on a lower surface of the light source. 
     The lighting appratus may further include a fixing part between the optical lens and the heat dissipating structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic perspective view of an optical lens according to an exemplary embodiment of the present invention; 
         FIG. 2  shows a cross sectional view of a lighting apparatus having a light source disposed below the optical lens of  FIG. 1 , taken along line A-B, together with light paths therefrom; 
         FIG. 3  shows a simulated light distribution curve of the lighting apparatus of  FIG. 2 ; 
         FIG. 4  shows a cross sectional view of a lighting apparatus having a light source disposed below the optical lens of  FIG. 1  from which a micro lens array is removed, taken along line A-B, together with light paths therefrom; 
         FIG. 5  shows a simulated light distribution curve of the lighting apparatus of  FIG. 4 ; 
         FIG. 6  is a schematic cross sectional view of an optical lens according to an exemplary embodiment of the present invention, which illustrates reference numerals for explaining length relationships between individual parts configuring the optical lens; 
         FIG. 7  is a graph illustrating a simulated ratio of a radius of an incidence part to a width of a light source in an optical lens according to an exemplary embodiment of the present invention; 
         FIG. 8  is a graph illustrating a simulated ratio of a radius of a reflection part to the width of the light source in the optical lens according to the exemplary embodiment of the present invention; 
         FIG. 9  is a graph illustrating a simulated ratio of a distance between the reflection part and the incidence part to the width of the light source in the optical lens according to the exemplary embodiment of the present invention; 
         FIG. 10  is a graph illustrating a simulated ratio of a distance between a plurality of micro lenses to the width of the light source in the optical lens according to the exemplary embodiment of the present invention; 
         FIG. 11  is a graph illustrating a simulated ratio of a radius of the plurality of micro lenses to the distance between the plurality of micro lenses in the optical lens according to the exemplary embodiment of the present invention; 
         FIG. 12  is a schematic cross sectional view of a lighting apparatus using the optical lens according to the exemplary embodiment of the present invention; 
         FIG. 13  is a simulated light distribution curve of the lighting apparatus according to the exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the shapes and sizes of components are exaggerated for clarity. While those skilled in the art could readily devise many other varied embodiments that incorporate the teachings of the present invention through the addition, modification or deletion of elements, such embodiments may fall within the scope of the present invention. 
     The same or equivalent elements are referred to by the same reference numerals throughout the specification. 
       FIG. 1  is a schematic perspective view of an optical lens according to an exemplary embodiment of the present invention. 
       FIG. 2  is a cross sectional view of a lighting apparatus having a light source disposed below the optical lens of  FIG. 1 , taken along line A-B, and also shows light paths of light having passed through the optical lens to go on. 
     Referring to  FIGS. 1 and 2 , an optical lens  10  according to the exemplary embodiment of the present invention may be provided to have a basic structure formed by an incidence part  13 , a reflection part  11  spaced apart from the incidence part  13  by a predetermined distance, and a side surface part  12  connecting the incidence part  13  and the reflection part  11 . In this case, the optical lens  10  maybe provided to have a shape similar to that of a transparent curved plate. Namely, the incidence part  13  and the reflection part  11  may be provided to have flat circular shapes, the centers of which are aligned. At the same time, the incidence part  13  and the reflection part  11  maybe parallel, such that they are continuously spaced apart from each other by the same distance. The incidence part  13  and the reflection part  11  spaced apart from each other may be connected through the side surface part  12 . As shown in this exemplary embodiment of the present invention, when a width (or a diameter) of the incidence part  13  is formed to be smaller than that of the reflection part  11 , the side surface part  12  may have a width narrowing towards the incidence part  13  from the reflection part  11 , while having a curved surface shape formed along the incidence part  13  and the reflection part  11  and projecting outwardly of the optical lens  10 . 
     With reference to  FIG. 2 , a case in which, when a light source  2  is disposed below the optical lens  10  formed as above, that is, centrally disposed below the incidence part  13 , light emitted from the light source passes through the optical lens to finally be emitted to the outside, will be explained in detail. 
     Referring to  FIG. 2 , a light emitting diode may be used as the light source  2  in the exemplary embodiment of the present invention. As described above, since the light emitting diode may generally have light distribution characteristics having an orientation angle remaining within approximately 120°, light emitted from the light source  2  may not be widely dispersed, whereby the majority of light therefrom may be emitted upwardly. In this case, the emitted light may reach the inclination part  13  of the optical lens  10  disposed to be parallel with the light source  2  in such a manner as to be centrally adjacent to the upper portion of the light source  2 . A certain amount of the emitted light maybe incident to a micro lens array  14 , a certain amount of the emitted light may reach the planar incidence part  13  on which the micro lens array is not formed, and a certain amount of the emitted light may be dispersed in air, without being guided in a direction of the optical lens  10 , may be reflected, or totally reflected from the reflection part  13  of the optical lens  10 , thereby being dispersed. In this case, the greatest quantity of emitted light may be incident to the optical lens  10 . This is an important factor in order to disperse light having a narrow range of orientation angle, which is the characteristic of the light emitting diode, through the optical lens  10 . Thus, in the exemplary embodiment of the present invention, the micro lens array  14  may be formed on the inclination part  13  in such a manner as to be disposed more widely than a width of the optical lens  10 . By doing so, the quantity of light reflected or totally reflected from the incidence part  13  without being incident on the optical lens  10 , to be dispersed may be minimized, thereby eventually contributing to the improvement of the light distribution characteristics. 
     As described above, the direction of light incident to the micro lens array  14  may be changed through refraction. In this case, an angle at which light is emitted from the micro lens array  14  may be greater than an angle at which the light is incident thereto, which will be explained in detail later with reference to the operation of the reflection part  11 . In this manner, since the micro lens array  14  serves to enlarge the angle at which light is incident thereto with respect to the inclination part  13  of the optical lens  10 , the micro lens array  14  may be formed to have a shape capable of maximizing this function. 
     The refraction of light refers to a change in the direction of light at an interface at which mediums having different refractive indexes meet each other, and the emitted light may be guided in a desirable direction by adjusting the refractive index of each medium and an angle formed by the direction of light with respect to the interface. 
     In the exemplary embodiment of the present invention, a plurality of micro lenses forming the micro lens array  14 , may each have a hemispherical shape protruding to the outside from the incidence part  13 . By doing so, a considerable amount of the light incident to the micro lens array  14  may be emitted at a large angle. However, the present invention is not limited to the exemplary embodiment, and the shape of the micro lens array may be variable, for example, hemisphere hemispherical, a conic, a triangular pyramidic, a quadrangular pyramidic, a randomly scattered shape, or a mixture thereof, according to embodiments of the present invention. 
     As set forth above, the micron lens array  14  may serve to refract the incident light at a large angle; however, not all light incident to the incidence part  13  of the optical lens  10  maybe refracted as above. In other words, the light incident to the incidence part  13  from the light source  2  may be incident through an area of the incidence part  13  on which the micro lens array  14  is not formed, reflected from the surfaces of the micro lenses, or may be advanced straight as it is, while being refracted only slightly, according to an incident position or an incident angle, even in the case in which light from the light source  2  may be incident to the incidence part  13  through the micro lens array  14 . 
     As described above, a fractional part of the light incident and refracted by the incidence part  13  maybe advanced directly to the side surface part  12  and ultimately be emitted, and the majority of the light incident and refracted by the incidence part  13  may be advanced to the reflection part  11 . As shown in  FIG. 2 , since the reflection part  11  may forma planar interface with air, it may generate a total reflection with respect to light having an incident angle exceeding a predetermined critical angle. As described above, a fractional part of the light incident and refracted by the incidence part  13  may be advanced directly to the side surface part  12  and ultimately be emitted, and the majority of the light incident and refracted by the incidence part  13  may be advanced to the reflection part  11 . As shown in  FIG. 2 , since the reflection part  11  may form a planar interface with air, it may generate a total reflection with respect to light having an incident angle exceeding a predetermined critical angle. As described above, as the light which is not sufficiently refracted by the incidence part  13  and substantially advanced to reach the reflection part  11  does not have an incident angle greater than the critical angle, the light reaching the reflection part  11  may be refracted and pass through the interface with air to finally be emitted. In this process, the light maybe dispersed and emitted at different angles; however, only with this, it is difficult to obtain noticeable effects for improving the orientation angle of the light emitting diode. However, light having an incident angle greater than the critical angle may be totally reflected so as not to be emitted to the outside of the optical lens  10 , thereby advancing in a direction of the side surface part  12 , or again advancing to the incidence part  13 . 
     In this manner, light may be guided in the direction of the side surface part  12  by enlarging an angle at which the light is incident on the reflection part  11 , and the micro lens array  114  may serve to enlarge the incident angle at the reflection part  11 . 
     The light guided to the side surface part  12  may no longer be totally reflected, and may need to be emitted to the outside of the optical lens  10 . In the case in which the light guided to the side surface part  12  is reflected or totally reflected, there may be an unintentional loss of light which may not be emitted to the outside. Thus, in order to prevent the occurrence of such a case, it is necessary to reduce the incident angle of the light incident to the side surface part  12 . Accordingly, the side surface part  12  may be outwardly protruded such that the light totally reflected from the reflection part  11  may be incident thereon in such a manner as to be approximately perpendicular thereto. 
     On the other hand, the light readvanced to the incidence part  13  may be directly emitted to the outside through the incidence part  13 , or may be totally rereflected in the case of a wide incident angle. Even in the case of repeating the total reflection, since the light may be inevitably advanced to the side surface part  12 , the light may consequently be emitted by the side surface part, whereby the loss of light may not be caused. 
     In the optical lens  10  as aforementioned, from the light incident by the incidence part  13  including the optical lens array  14 , a certain amount of light L 1  may pass directly through the reflection part  11  to be emitted upwardly of the optical lens  10 , a certain amount of light L 2  may be totally reflected from the reflection part  11  and pass through the side surface part  12  to finally be emitted sidewardly, a certain amount of light L 3  may repeat the total reflection and pass through the side surface part  12  or the incidence part  13  to be emitted. In this manner, even in the case of the light emitting diode having an orientation angle remaining within the range of approximately 120°, when the lens does not exist, light may be irradiated sidewardly and backwardly by disposing the optical lens  10  above the light source according to the exemplary embodiment of the present invention. 
       FIG. 3  shows a simulated light distribution curve of the lighting apparatus of  FIG. 2 . Referring to  FIG. 3 , it can be confirmed that light emitted the light source has improved light distribution characteristics through the optical lens  10  according to the exemplary embodiment of the present invention. 
       FIG. 4  shows a cross sectional view of a lighting apparatus having a light source  4  disposed below the optical lens of  FIG. 1  from which the micro lens array  14  is removed, taken along line A-B, together with light paths therefrom. 
     Referring to  FIG. 4 , an optical lens  40  having a shape the same as that of the optical lens  10  shown in  FIGS. 1 and 2 , except for the formation of the micro lens array  14  on an incidence part  43  maybe illustrated. That is,  FIG. 4  is a cross sectional view of the optical lens  40  including the incidence part  43 , a side surface part  42 , and a reflection part  41  above the light source  4 , which also shows light paths L 4  and L 5  of light incident from the light source  4 . Here, in a case in which the micro lens array does not exist, the majority of light of light paths L 4  and L 5 , incident to the incidence part  43 , may be not be refracted to have large emitting angles, such that it may ultimately be emitted having not been totally reflected. 
       FIG. 5  shows a simulated light distribution curve of the lighting apparatus of  FIG. 4 . Referring to  FIG. 5 , even in the case of disposing the optical lens  40  according to the exemplary embodiment of the present invention, when the micro lens array  14  is removed therefrom, the light distribution characteristics thereof may be rarely improved, as compared to the case shown in  FIG. 3   
     As described above, the optical lens  10  may lead to natural light scattering by allowing a certain amount of light to advance, and a certain amount of light to be refracted. In this process, the amount of light and the refractive degree to which the amount of light is refracted may be determined by a combination of diverse variables such as the shape and the formation range of the micro lens array  14 , the type of optical lens structure, the interval between micro lens array  14 , the diameters and heights of the micro lens array  14 , the width of the light source, and the like. Exemplary embodiments with reference to the diverse variables will be now explained in detail. 
       FIG. 6  is a schematic cross sectional view of an optical lens according to an exemplary embodiment of the present invention, which illustrates reference numerals for explaining length relationships between individual parts configuring the optical lens. 
       FIGS. 7 through 11  show graphs respectively illustrating a simulated back direction efficiency of light when the lengths of the individual parts of  FIG. 6  are varied. 
     Referring to  FIG. 6 , a width S of a light source  6 , a width D 1  of an incidence part  63  of an optical lens  60 , a distance H between the incidence part  63  and a reflection part  61  (that is, a height of the optical lens  60 ), an interval P between micro lenses, and a radius R of each micro lens having a hemispherical shape are defined. 
     In addition, referring to  FIGS. 7 through 11 , when D 1 /S is equal to approximately 2.5, the maximum back direction efficiency of light may be obtained, and preferably, when D 1 /S is within the range of 1.8 to 3.2, advantageous light efficiency may be obtained. When D 2 /S is equal to approximately 3.5, the maximum back direction efficiency of light may be obtained, and preferably, when D 2 /S is within the range of 3 to 4.2, advantageous light efficiency may be obtained. When H/S is equal to approximately 0.5, the maximum back direction efficiency of light may be obtained and preferably, when H/S is within the range of 0.46 to 0.9, advantageous light efficiency may be obtained. When P/S is equal to approximately 0.03, the maximum back direction efficiency of light may be obtained and preferably, when P/S is within the range of 0.08 or less, advantageous light efficiency may be obtained. When R/P is equal to approximately 0.05, the maximum ack direction efficiency of light may be obtained and preferably, when R/P is within the range of 0.48 to 0.62, advantageous light efficiency may be obtained. 
     Meanwhile, the optical lenses  10 ,  40 , and  60  may be made of various light-transmitting materials, and preferably, may be made of at least one of polycarbonate and acryl. 
       FIG. 12  is schematic cross sectional view of a lighting apparatus  100  using the optical lens according to the exemplary embodiment of the present invention. In the lighting apparatus  100  according to the exemplary embodiment of the present invention, a circuit board  140  may be disposed on a heat dissipating structure  150  and a light source  120  is mounted on the circuit board  140 . In this case, the light source  120  may include a plurality of light emitting diodes. An optical lens  110  according the aforementioned embodiments of the present invention is disposed above the light source  120 , and the center of the light source  120  may be positioned in such a manner as to correspond to the center of the optical lens  110 . In this case, when the width of the optical lens  110  is greater than that of the light source  120 , a fixing part  160  may be disposed between the heat dissipating structure  150  and the optical lens  110  so as to firmly fix the optical lens  110 . In addition, a cover part  130  may be disposed above the heat dissipating structure  150  in such a manner as to surround the light source  110  and the optical lens  110 . 
     A driving circuit part  170  for operating the light source  110  maybe disposed within the heat dissipating structure  150 , and an electrical connection part  180  may be formed to be connected with the driving circuit part  170 . The lighting apparatus according to the exemplary embodiment of the present invention has a shape similar to that of an incandescent lamp according to the related art, and is merely exemplarily illustrated. Thus, the lighting apparatus according to the exemplary embodiment of the present invention may be variously modified according to the requirements of design. 
       FIG. 13  is a simulated light distribution curve of the lighting apparatus according to the exemplary embodiment of the present invention. Referring to  FIG. 13 , it can be seen that the light distribution characteristics of the lighting apparatus  110  are improved by using the optical lens  110  according to the exemplary embodiment of the present invention. 
     As set forth above, according to exemplary embodiments of the invention, by disposing an optical lens performing a light diffusion function, the light of a light emitting diode can be widely spread to be evenly diffused, and at the same time, superior luminous efficiency can be obtained. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.