Patent Publication Number: US-10317018-B2

Title: Lighting device

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a U.S. National Stage Application under 35 U.S.C. § 371 of PCT Application No. PCT/KR2016/009165, filed Aug. 19, 2016, which claims priority to Korean Patent Application No. 10-2015-0123441, and Korean Patent Application No. 10-2015-0123442, both filed Sep. 1, 2015, whose entire disclosures are hereby incorporated by reference. 
     TECHNICAL FIELD 
     Embodiments relate to a lighting device including light emitting elements. 
     BACKGROUND ART 
     In general, a light emitting diode (LED) is a device that emits light when electrons and holes meet at a P-N junction by applying a current. The LED has many advantages over conventional light sources, such as continuous light emission at a low voltage and low current and low power consumption. 
     Particularly, LEDs are widely used for various display devices, backlight sources, and the like. In recent years, technologies for emitting white light by using three light emitting diode chips emitting red, green and blue light respectively or by using a fluorescent substance to convert the wavelength of light have been developed and are expanding in application range even to lighting devices. 
     An LED that emits ultraviolet light may be used in water purifiers, sterilizers, and the like for the purpose of sterilization, cleaning, and the like, and may also be used in an exposure apparatus that forms a photoresist pattern. Particularly, for a light emitting module including the LED for emitting ultraviolet light used in the exposure apparatus, it is important to concentrate light on a certain target area. 
     When the LED, which has a relatively small light amount compared to a lamp having a large light amount, is used as a light source to concentrate the power of the light source on an optical fiber or a detector having a size comparable to that of the light source, it is difficult to concentrate the power of the light source over the entire area of the detector using the simple form of a reflector. 
     DISCLOSURE 
     Technical Problem 
     Embodiments provide a lighting device capable of uniformly condensing light on a target having a certain area. 
     Technical Solution 
     In one embodiment, a lighting device may include a light emitting unit including a board and a plurality of light emitting elements disposed on a top surface of the board, a reflector including a first reflective surface positioned on one side of the light emitting unit and a second reflective surface positioned on an opposite side of the light emitting unit, the first reflective surface and the second reflective surface having a parabolic shape, and a lens disposed on the light emitting unit between the first reflective surface and the second reflective surface, wherein each of the light emitting elements is arranged to be aligned with a focus of the parabolic shape, and a height of the reflector is defined by Equation 1 defined as follows: 
     
       
         
           
             
               
                 
                   
                     Z 
                     = 
                     
                       
                         
                           ( 
                           
                             PD 
                             / 
                             2 
                           
                           ) 
                         
                         2 
                       
                       
                         4 
                         ⁢ 
                         a 
                       
                     
                   
                   , 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
               
             
           
         
       
     
     where Z may be the height of the reflector, a may be a focal length of the parabolic shape, and PD may be a distance from an uppermost end of the first reflective surface to an uppermost end of the second reflective surface. 
     Z≥0.89 A, and A may be a diameter of the light emitting elements. 
     A distance between a lowermost end of the first reflective surface and a lowermost end of the second reflective surface may be greater than or equal to 4a. 
     The lens may include a refractor including an incidence surface on which light emitted from the light emitting elements is incident, and an exit surface through which light passing through the incidence surface passes, wherein the light passing through the refractor wearing output in parallel with a direction perpendicular to the top surface of the board. 
     A diameter of the incidence surface of the lens may be defined by Equation 2 as follows:
 
 LD =(2α×tan θ+√{square root over ((2α×tan θ) 2 +4α 2 )})×2,  Equation 2
 
     where LD may be the diameter of the incidence surface of the lens, and θ may be an angle of light emitted from the light emitting elements having a luminous intensity of 10% of a maximum value of an intensity distribution. 
     A height of the lens may be defined by Equation 3 as follows: 
     
       
         
           
             
               
                 
                   
                     LZ 
                     = 
                     
                       tan 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       α 
                       × 
                       
                         LD 
                         2 
                       
                     
                   
                   , 
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   3 
                 
               
             
           
         
       
     
     where LZ may be the height of the lens, and a may be an angle between the top surface of the board and a reference line, wherein the reference line may be an imaginary line connecting a center of each of the light emitting elements and an uppermost end of the first reflective surface or the second reflective surface. 
     α may be 33° to 67°. Alternatively, α may be 33° to 51°. Alternatively, α may be 33° to 37°. 
     A first edge of the lens may contact the first reference line, and a second edge of the lens may contact the second reference line, wherein and the first reference line may be an imaginary line connecting a center of each of the light emitting elements and an uppermost end of the first reflective surface, and the second reference line may be an imaginary line connecting the center of each of the light emitting elements and an uppermost end of the second reflective surface. 
     The lens may further include a support connected to the refractor and fixed to the top surface of the board, wherein the support may be coupled to a second region of the top surface other than a first region of the board, the light emitting elements being positioned in the first region. 
     The lighting device may further include a housing having a cavity for accommodating the light emitting unit, the reflector, and the lens, wherein an inner wall of the housing may be provided with a protruding support for supporting opposite ends of the lens. 
     Each of the light emitting elements may generate ultraviolet light in a wavelength range of 200 nm to 400 nm. 
     In another embodiment, a lighting device may include a light emitting unit including a board and at least one light emitting element disposed on a top surface of the board, a reflector including a first opening positioned around the light emitting unit, a second opening positioned over the first opening and allowing light emitted from the light emitting unit to be output therethrough, and a reflector including a reflective surface positioned between the first opening and the second opening, and a lens disposed on the light emitting unit on an inner side of the reflective surface and having an incidence surface and an exit surface, wherein the reflective surface may be an elliptic shape and a corner where the incidence surface and the exit surface of the lens meet is aligned to contact a reference line, wherein the reference line may be an imaginary line connecting a center of the at least one light emitting element and an uppermost end of the reflective surface, wherein an angle between a vertical reference line and the reference line may be 30° to 51°, wherein the vertical reference line may be an imaginary line passing through a center of the reflector and a center of the lens and perpendicular to the top surface of the board. 
     A diameter of the first opening of the reflector may be greater than or equal to 1.2 times a diameter of a light emitting surface of the light emitting element and be less than or equal to 5.0 times the diameter of the light emitting surface of the light emitting element. 
     A height of the lens may be half a height of the reflector. 
     40% or more of a total collected power may be concentrated on a target spaced apart from a lower surface of the reflector and positioned in front of the second opening. 
     A diameter of the target may be greater than or equal to 1.2 times a diameter of a light emitting surface of the light emitting element and be less than or equal to 1.5 times the diameter of the light emitting surface of the light emitting element. 
     A distance from the lower surface of the reflector to the target may be greater than or equal to 1.0 time a diameter of a light emitting surface of the light emitting element and be less than or equal to 4.5 times the diameter of the light emitting surface of the light emitting element. 
     A diameter of the lens may be defined by Equations 4 and 5 as follows:
 
 LD 2= k×B , and  Equation 4
 
 B= 2 ×LH 2×tan(θ),  Equation 5
 
     where LD 2  may be the diameter of the lens, B may be half a diameter of the second opening, 0.8≤k≤1, LH 2  may be a height of the lens, and θ may be the angle between the vertical reference line and the reference line. 
     Advantageous Effects 
     According to embodiments, light may be uniformly condensed on a target having a certain area. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  shows an exploded perspective view of a lighting device according to an embodiment. 
         FIG. 2A  shows a cross-sectional view of the lighting device shown in  FIG. 1 , taken along line AB. 
         FIG. 2B  shows a cross-sectional of the lighting device shown in  FIG. 1 , taken along line CD. 
         FIG. 3  shows light refracted by the lens shown in  FIG. 1 . 
         FIG. 4  shows the height of the first and second reflective surfaces shown in  FIG. 3 . 
         FIG. 5  shows light reflected by the reflector shown in  FIG. 1 . 
         FIG. 6  shows a cross-sectional view of a lighting device according to another embodiment, taken along line CD. 
         FIG. 7  shows conditions for each case for the simulation result of  FIG. 8 . 
         FIG. 8  shows a rate of increase in luminous intensity according to a simulation result based on the conditions of  FIG. 7 . 
         FIG. 9  shows a curve of maximum intensity increase rate in each case of  FIG. 8 . 
         FIG. 10  shows an exploded perspective view of a lighting device according to an embodiment. 
         FIG. 11  shows a cross-sectional view of the lighting device shown in  FIG. 10 , taken along line AB. 
         FIG. 12  shows a cross-sectional of the lighting device shown in  FIG. 10 , taken along line CD. 
         FIG. 13  shows light reflected by the reflective surface of the reflector shown in  FIG. 10 . 
         FIG. 14  shows the size of a reflective surface, the size and position of a lens, and the size and position of a target. 
         FIG. 15  shows conditions for each case for the simulation result of  FIG. 16 . 
         FIG. 16  shows a simulation result of light condensation of the lighting device according to  FIG. 15 . 
         FIG. 17  shows conditions for each case for the simulation result of  FIG. 18 . 
         FIG. 18  shows a simulation result of light condensation of a lighting device according to the conditions of  FIG. 17 . 
         FIG. 19  is a graph of the simulation results of  FIGS. 16 and 18 . 
     
    
    
     BEST MODE 
     Hereinafter, embodiments will be more clearly understood from the following description taken in conjunction with the accompanying drawings. In the description of the embodiments, it is to be understood that when a layer (film), region, pattern or structure is described as being “on” or “under” a substrate, each layer (film), region, pad, or pattern, the terms “on” and “under” conceptually include “directly” or “indirectly”. In the description, “on” or “under” is defined based on the drawings. 
     It will be appreciated that for simplicity and clarity of illustration, the dimensions of some of the elements are exaggerated, omitted, or schematically shown relative to other elements. In addition, elements shown in the drawings have not necessarily been drawn to scale. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1  shows an exploded perspective view of a lighting device  100  according to an embodiment,  FIG. 2A  shows a cross-sectional view of the lighting device  100  shown in  FIG. 1 , taken along line AB, and  FIG. 2B  shows a cross-sectional of the lighting device  100  shown in  FIG. 1 , taken along line CD. 
     Referring to  FIGS. 1, 2A, and 2B , the lighting device  100  includes a housing  110 , a light emitting unit  120 , a reflector  130 , and a lens  140 . 
     The housing  110  has a cavity  111  for accommodating the light emitting unit  120 , the reflector  130 , and the lens  140 . 
     The housing  110  may be formed of a plastic material having a light weight and high thermal resistance, or a metal material having a high thermal conductivity such as, for example, aluminum. The inner wall of the housing  110  may be coated with a reflective material capable of reflecting light emitted from the light emitting unit  120 . In another embodiment, the housing  110  may be formed of a reflective material that reflects light. 
     The light emitting unit  120  is disposed in the housing  110  and emits light. 
     The light emitting unit  120  may include a board  122 , and a light emitting element  124 . The light emitting unit  120  may further include a resin layer  126  capable of protecting the light emitting element  124  and refracting light emitted from the light emitting element  124 . Here, the resin layer  126  may serve as a lens for refracting light. 
     The board  122  of the light emitting unit  120  may be a plate-shaped structure on which the light emitting element  124  and an element capable of supplying power to the light emitting element  124 , controlling the light emitting element, or protecting the light emitting element may be mounted. 
     For example, the board  122  may be a printed circuit board or a metal PCB. In  FIG. 2B , the board  122  may have a rectangular parallelepiped shape. However, embodiments are not limited thereto. The board may have a circular, elliptical, or polyhedral plate shape. 
     The light emitting element  124  is disposed on one surface (e.g., the top surface) of the board  122 . The light emitting element  124  may be a light emitting diode (LED)-based light source, but is not limited thereto. For example, the light emitting element  124  may take the form of an LED chip, or an LED package. 
     The number of the light emitting elements  124  may be greater than or equal to 1. While it is illustrated in  FIG. 1  that a plurality of light emitting elements  124 - 1  to  124 - n  (where n is a natural number greater than 1) is disposed in a line on the board  122 , embodiments are not limited thereto. The plurality of light emitting elements  124 - 1  to  124 - n  (where n is a natural number greater than 1) may be disposed in various shapes such as a circular shape or a matrix shape on the board  122 . 
     The light emitting elements  124 - 1  to  124 - n  (where n is a natural number greater than 1) may emit rays in the same wavelength range or similar wavelength ranges. Alternatively, at least one of the light emitting elements  124 - 1  to  124 - n  (where n is a natural number greater than 1) may emit light in a different wavelength range. 
     For example, each of the light emitting elements  124 - 1  to  124 - n  (where n is a natural number greater than 1) may generate ultraviolet light having a wavelength range of 200 nm to 400 nm. Alternatively, for example, each of the light emitting elements  124 - 1  to  124 - n  (where n is a natural number greater than 1) may generate ultraviolet-C (UVC) in a wavelength range of 200 nm to 280 nm. 
     The reflector  130  may include a first reflective surface  132   a  positioned on one side of the light emitting unit  120  and a second reflective surface  132   b  positioned on the opposite side of the light emitting unit  120  and facing the first reflective surface  132   a.    
     The first reflective surface  132   a  and the second reflective surface  134   a  may have a parabolic shape or have a curvature of a parabola. 
     For example, the curved surface where the extended line of the first reflective surface  132   a  meets the extended line of the second reflective surface  134   a  may be parabolic, and the light emitting elements  124 - 1  to  124 - n  (where n is a natural number greater than 1) may be arranged so as to be aligned at the focus of the parabolic shape. 
     The reflector  130  may include a first reflector  132  positioned at one side of the light emitting unit  120  and a second reflector  134  positioned at the opposite side of the light emitting unit  120 . As shown in  FIGS. 1, 2A, and 2B , the first and second reflectors  132  and  134  are spaced apart from each other, but embodiments are not limited thereto. In another embodiment, one end of the first reflector  132  and one end of the second reflector  134  may be connected to each other and the opposite end of the first reflector  132  and the opposite end of the second reflector  134  may be connected to each other. 
     For example, the first reflector  132  may include a first reflective surface  132   a  facing the light emitting unit  120 , a first side surface  132   b  positioned opposite the first reflective surface  132   a , and a first lower surface  132   c  positioned between the first reflective surface  132   a  and the first side surface  132   b.    
     The second reflector  134  may include a second reflective surface  134   a  facing the light emitting unit  120 , a second side surface  134   b  positioned opposite the second reflective surface  134   a , and a second lower surface  134   c  positioned between the second reflective surface  134   a  and the second side surface  134   b.    
     For example, the length L 1  of the upper side (or lower side) of the first reflective surface  132   a  may be greater than the length L 2  from the upper end to the lower end of the first reflective surface  132   a . The length of the upper side (or lower side) of the second reflective surface  134   a  may be greater than the length from the upper end to the lower end of the second reflective surface  134   a.    
     For example, the lengths of the upper side and the lower side of the first reflective surface  132   a  may be equal to each other, and the lengths of the upper side and the lower side of the second reflective surface  134   a  may be equal to each other. 
     In addition, for example, the length L 1  of the upper side (or lower side) of the first reflective surface  132   a  may be equal to the length L 1  of the upper side (or lower side) of the second reflective surface  134   a , but embodiments are not limited thereto. The length L 1  of the upper side or lower side of each of the first reflective surface  132   a  and the second reflective surface  134   a  may be increased or decreased depending on the number and arrangement of the light emitting elements of the light emitting unit  120 . 
     The first reflector  132  and the second reflector  134  are spaced apart from each other, and the light emitting unit  120  may be positioned in a space between the first reflector  132  and the second reflector  134 . 
     The first reflective surface  132   a  and the second reflective surface  134   a  may be symmetrical with respect to a vertical reference plane  101 . The vertical reference plane  101  may be an imaginary plane passing through the center of the lens  140  and perpendicular to the top surface of the board  122 . For example, the lens  140  may be bisected to be symmetrical with respect to the vertical reference plane  101 . 
     The reflector  130  may be formed of a reflective metal, for example, stainless steel or silver (Ag). Alternatively, the reflector  130  may be formed of a metal material causing specular reflection. 
     Alternatively, the reflector  130  may be formed of a resin material having high reflectivity, but embodiments are not limited thereto. 
     The lens  140  is disposed on the light emitting unit  120  between the first reflective surface  132  and the second reflective surface  134 . For example, the center of the light emitting unit  120  and the center of the lens  140  may be aligned with each other in the vertical direction, but embodiments are not limited thereto. 
     For example, the lens  140  refracts and transmits the light emitted from the light emitting unit  120 . 
     The lens  140  may include a refractor  142  which is convex in a direction pointing from the lower end to the upper end of the reflector  130  or pointing from the light emitting unit  120  to the lens  140  and a support  144  provided on the lower surface of the refractor  142 . 
     The support  144  of the lens  140  may be coupled to a coupling groove  122   a  provided on the top surface of the board  122  and support the lens  140 . 
     The support  144  may take the form of a leg. At least one support may be provided at one end of the lower surface of the lens  140 , and at least one support may be provided at the opposite end of the lower surface of the lens  140 . For example, the number of the supports  144  may be two or more. 
     For example, in order to suppress refraction of light emitted from the light emitting unit  120  caused by the support  144 , supports may be provided on one side and the opposite side of the lower surface of the refractor  142 . However, embodiments are not limited thereto. 
     While it is illustrated in  FIG. 1  that the supports  144  of the lens  140  are coupled to a groove  122   a  provided in the board  122 , embodiments are not limited thereto. In another embodiment, the supports  144  of the lens  140  may be coupled to a groove (not shown) provided in the lower surface of the cavity  111  of the housing  110 . In another embodiment, the groove  122   a  may not be provided in the board  122 , but the supports  144  may be fixed to the board  122  or the lower surface of the cavity  111  of the housing  110  by an adhesive member. 
     As shown in  FIG. 2B , the support  144  may not be positioned in a first region S 1  which is between the first reflective surface  132   a  and the second reflective surface  134   a  and correspond to the light emitting elements  124 - 1  to  124 - n  (where n is a natural number greater than 1). For example, the support  144  of the lens  140  may be disposed in a second region S 2 , which is between the first reflective surface  132   a  and the second reflective surface  134   a , other than the first region S 1 . For example, the support  144  may be coupled to the second region S 2  other than the first region S 1  of the top surface of the board  122  in which the light emitting elements  124 - 1  to  124 - n  (where n is a natural number greater than 1) are positioned. Here, the groove  122   a  of the board  122  to be coupled with the support  114  may also be formed in the second region S 2  of the board  122 . 
       FIG. 3  shows light refracted by the lens  140  shown in  FIG. 1 , and  FIG. 4  shows the height Z of the first and second reflective surfaces  132   a  and  134   a  shown in  FIG. 3 . 
     Referring to  FIGS. 3 and 4 , the refractor  142  of the lens  140  may include an incidence surface  142   a  and an exit surface  142   b.    
     The incidence surface  142   a  of the refractor  142  of the lens  140  may be a surface on which light emitted from the light emitting elements  124 - 1  to  124 - n  (where n is a natural number greater than 1) is incident and refracted, and may be spaced apart from the first and second reflective surfaces  132   a  and  134   a.    
     The exit surface  142   b  of the refractor  142  of the lens  140  refracts and passes the light that has passed through the incidence surface  142   a . The light that has passed through the incidence surface  142   a  and the exit surface  142   b  of the refractor  142  of the lens  140  may be converted into rays  148  parallel to the direction pointing from the light emitting unit  120  to the lens  140 . 
     For example, the incidence surface  142   a  of the lens  140  may be a flat surface parallel to the top surface of the board  122 , and the exit surface  142   b  may have a hemispherical shape or a dome shape, for example, a parabolic shape, or an elliptical shape that is convex in a direction pointing from the light emitting unit  120  to the lens  140 . However, embodiments are not limited thereto. In another embodiment, the incidence surface  142   a  and the exit surface  142   b  may be embodied in various shapes to convert the light passing through the incidence surface  142   a  and the exit surface  142   b  into parallel rays  148 . 
     The space between the first and second reflective surfaces  132   a  and  134   a  and the space between the lens  140  and the light emitting unit  120  may be filled with a gas such as, for example, air, but embodiments are not limited thereto. In another embodiment, the spaces may be filled with a translucent material. 
     The lens  140  may be disposed such that a first edge  142 - 1  of the lens  140  adjoins a first imaginary reference line  102   a  connecting the center of the light emitting element  124  and the uppermost end  132 - 1  of the first reflective surface  132   a . For example, the first edge  142 - 1  of the lens  140  may be a first corner of the lens  140  where the incidence surface  142   a  and the exit surface  142   b  of the lens  140  adjoin each other. 
     The lens  140  may be disposed such that the second edge  142 - 2  of the lens  140  adjoins a second imaginary reference line  102   b  connecting the center of the light emitting element  124  and the uppermost end  134 - 1  of the second reflective surface  134   a . For example, the second edge  142 - 2  of the lens  140  may be a second corner of the lens  140  where the incidence surface  142   a  and the exit surface  142   b  of the lens  140  adjoin each other. 
     For example, the center of the light emitting element  124  may be the center of the light emitting surface of the light emitting element  124 , and the first and second edges  142 - 1  and  142 - 2  of the lens  140  may be corners where the lateral surface and the lower surface of the light emitting element  124  meet. 
     The light of the light emitting element  124  emitted into a space between the first imaginary reference line  102   a  and the second imaginary reference line  102   b  may be refracted by the lens  140 , and the refracted light may be converted into light  148  parallel to a direction pointing from the light emitting unit  120  to the lens  140 . 
     In another embodiment, the first edge  142 - 1  and the second edge  142 - 2  of the lens  140  may be disposed to be spaced apart from the first reference line  102   a  and the second reference line  102   b.    
       FIG. 5  shows light reflected by the reflector  130  shown in  FIG. 1 . 
     Referring to  FIG. 5 , the light of the light emitting element  124  emitted downward of the first reference line  102   a  and the second reference line  102   b  is reflected by the first and second reflective surfaces  132   a  and  134   a  without being refracted by the lens  140 . 
     Since the first and second reflective surfaces  132   a  and  134   a  have a parabolic shape, the light  149  reflected by the first and second reflective surfaces  132   a  and  134   a  may be parallel to the direction pointing from the light emitting unit  120  to the lens  140 . For example, the light of the light emitting element  124  emitted downward of the first reference line  102   a  and the second reference line  102   b  may be reflected by the first and second reflective surfaces  132   a  and  134   a  and thus converted into parallel rays  149  to be output. 
     The height Z of the first and second reflectors  132  and  134  may be greater than or equal to 0.89 A (Z≥0.89 A). A may be the diameter of the light emitting element  124 . 
     When the height Z of the first and second reflectors  132  and  134  is less than 0.89 A, the first and second reflective surfaces  132   a  and  134   a  are too small for the lens  140  to be disposed on the inner side of the first and second reflective surfaces  132   a  and  134   a . The upper limit of the first and second reflectors  132  and  134  may be defined by β, which will be described later. 
     In an embodiment, the relationship between the height Z of the first and second reflectors  132  and  134 , the position a of the light emitting elements  160 - 1  to  160 - m , and the diameter PD of the light exit port of the first and second reflectors  132   a  and  132   b  may be defined as Equation 1. 
     
       
         
           
             
               
                 
                   Z 
                   = 
                   
                     
                       
                         ( 
                         
                           PD 
                           / 
                           2 
                         
                         ) 
                       
                       2 
                     
                     
                       4 
                       ⁢ 
                       a 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
               
             
           
         
       
     
     Here, Z denotes the height of the reflectors  132  and  134 , for example, the distance from the bottoms  132   c  and  134   c  to the uppermost ends  132 - 1  and  134 - 1  of the first and second reflective surfaces  132   a  and  134   a.    
     PD denotes the diameter of the light exit port between the first and second reflective surfaces  132   a  and  134   a , for example, the distance from the uppermost end  132 - 1  of the first reflective surface  132   a  to the uppermost end  134 - 1  of the second reflective surface  134   a.    
     a may be the distance from the lowermost end of the parabolic shape PA to the light emitting element  124 . For example, a may be the focal length of the parabolic shape PA. 
     The distance D between the lowermost end  132 - 2  of the first reflective surface  132   a  and the lowermost end  134 - 2  of the second reflective surface  134   a  may be 4a. For example, when the light emitting element  124  is positioned at the focus of the parabolic shape PA, D may be set to 4a. 
     The distance D between the lowermost end  132 - 2  of the first reflective surface  132   a  and the lowermost end  134 - 2  of the second reflective surface  134   a  may be 1.2 A or more. 
     When the distance D between the lowermost end  132 - 2  of the first reflective surface  132   a  and the lowermost end  134 - 2  of the second reflective surface  134   a  is greater than or equal to 1.2 A, light generated from the light emitting element  124  may be transmitted to the first and second reflective surfaces  132   a  and  134   a  without loss. On the other hand, when the distance D between the lowermost end  132 - 2  of the first reflective surface  132   a  and the lowermost end  134 - 2  of the second reflective surface  134   a  is less than 1.2 A, loss of the amount of light emitted from the light emitting element  124  may occur. 
     The diameter LD of the incidence surface  142   a  of the lens  140  may be defined as Equation 2.
 
 LD =(2α×tan θ+√{square root over ((2α×tan θ) 2 +4 2 )})×2,  Equation 2
 
     Here, θ denotes the angle of light emitted from the light emitting elements  124 - 1  to  124 - 4  corresponding to a 10% region of the maximum value of the luminous intensity in the intensity distribution of the lighting device  100 , and a denotes the focal length of the parabolic shape PA. 
     The height LZ of the lens  140  may be defined as Equation 3. 
     
       
         
           
             
               
                 
                   LZ 
                   = 
                   
                     tan 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     α 
                     × 
                     
                       LD 
                       2 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   3 
                 
               
             
           
         
       
     
     Here, LZ may be the height of the lens  140 , for example, the distance from the lower surfaces  132   c  and  134   c  of the first and second reflectors  132  and  134  to the incidence surface  142   a  of the lens  140 , and α may be an angle between the horizontal reference plane and the first imaginary reference line  102   a  or an angle between the horizontal reference plane and the second imaginary reference line  102   b . The horizontal reference plane may be a plane perpendicular to the vertical reference plane  101 . For example, the horizontal reference plane may be the lower surfaces  132   c  and  134   c  of the first and second reflectors  132  and  134 , or the top surface of the board  122 . 
       FIG. 7  shows conditions for each case for the simulation result of  FIG. 8 ,  FIG. 8  shows a rate of increase in luminous intensity according to a simulation result based on the conditions of  FIG. 7 , and  FIG. 9  shows a curve of maximum intensity increase rate in each case of  FIG. 8 . 
     Referring to  FIG. 7 , the size of each of the light emitting elements  160 - 1  to  160 - m  may be 2.5 mm×2.5 mm, and the length of the diagonal of each of the light emitting elements  160 - 1  to  160 - m  may be 3.5 mm. The light emitting elements  160 - 1  to  160 - m  may be aligned at the focus of a parabolic shape. 
     If the height Z of the first and second reflectors  132  and  134  is excessively small compared to the diameter of each of the light emitting elements  160 - 1  to  160 - m , the maximum intensity increase rate of the lighting device  100  is lowered. If the height Z of the first and second reflectors  132  and  134  is excessively large compared to the diameter of each of the light emitting elements  160 - 1  to  160 - m , the region for adjusting the light source becomes large and the role of the lens  140  of collecting light is weakened. 
     Compared to a lighting device which is not provided with the lens  140 , the lighting device  100  according to the embodiment may exhibit a maximum intensity increase rate of 10% or more. 
     The maximum intensity of the lighting device may be used as an index for evaluating the intensity distribution of the lighting device that performs light condensation into parallel rays well. That is, as the maximum intensity of the lighting device increases, the lighting device may have an intensity distribution which exhibits better light condensation into parallel rays. Here, the rate of increase may be a percentage of the maximum intensity of the lighting device  100  having the lens  140  with respect to the maximum intensity of the lighting device without the lens  140 . 
     Referring to  FIG. 8 , Cases 1 to 5 may have a maximum intensity increase rate of 10% or more. Here, α may be 33° to 67°, and β may be 23° to 57°. In this case, the angle 2β between the first reference line  102   a  and the second reference line  102   b  may be 46° to 114°. 
     Alternatively, the lighting device  100  according to an embodiment may have a maximum intensity increase rate of 30% or more. Referring to  FIG. 8 , Cases 1 to 3 may have a maximum intensity increase rate of 30% or more. Here, α may be 33° to 51°, and β may be 39° to 57°. In this case, the angle 2β between the first reference line  102   a  and the second reference line  102   b  may be 78° to 114°. 
     Alternatively, the lighting device  100  according to an embodiment may have a maximum intensity increase rate of 60% or more. Referring to  FIG. 8 , Cases 1 and 2 may have a maximum intensity increase rate of 60% or more. Here, α may be 33° to 37°, and β may be 53° to 57°. In this case, the angle 2β between the first reference line  102   a  and the second reference line  102   b  may be 106° to 114°. 
       FIG. 6  shows a cross-sectional view of a lighting device according to another embodiment, taken along line CD. 
     The perspective view of  FIG. 6  may be the same as  FIG. 1  except for a protruding support  115  of  FIG. 6 , and the cross-sectional view taken along line AB may be the same as  FIG. 2A . The same reference numerals as used in  FIGS. 1, 2A and 2B  represent the same constituents, and the description of the same constituents will be simplified or omitted. 
     Referring to  FIG. 6 , a lens  140 ′ of a lighting device  200  does not have the support  144  of  FIG. 1 . The housing  110  of the lighting device  200  has a protruding support  115  on the inner wall thereof. The protruding support  115  supports one end and the opposite end of the lower surface of the refractor  142  of the lens  140 ′. 
     Accordingly, the lens  140 ′ may be supported by the protruding support  115  provided on the inner wall of the housing  110 . 
     In the embodiment shown in  FIG. 6 , the support  114  is not provided, and therefore the light emitted from the light emitting elements  124 - 1  to  124 - n  may be prevented from being refracted by the support  114  of the lens  140 , the condensing efficiency may be improved as designed by Equations 1 to 3. 
     Compared to a red LED, blue LED, green LED, or white LED, a UV LED is a point light source that provides a relatively small amount of light. Therefore, if a light emitting module is configured with only the UV LED, light condensing capability is degraded. 
     When the target distance increases, the number of UV LEDs included in the light emitting module needs to be increased to meet the target irradiance. In addition, as the target distance increases, not only irradiance but also light uniformity is lowered. 
     In this embodiment, light may be uniformly condensed on a target having a certain area by converting light emitted from a UV LED light source into parallel rays using the parabolic reflective surfaces  132   a  and  134   a  and the condenser lens  140 . The target may be, but is not limited to, a light receiving device, an optical fiber, an optical cable, an exposure device, a detector, an endoscope, or a sensor. 
     In addition, as the lighting device  100  according to the embodiment is provided with the first and second reflectors  132  and  134  and the lens  140  according to Equations 1 to 3, it may have a maximum intensity increase rate of 10% or more. 
       FIG. 10  shows an exploded perspective view of a lighting device  1100  according to an embodiment,  FIG. 11  shows a cross-sectional view of the lighting device  1100  shown in  FIG. 10 , taken along line AB, and  FIG. 12  shows a cross-sectional of the lighting device  1100  shown in  FIG. 10 , taken along line CD. 
     Referring to  FIGS. 10 to 12 , the lighting device  1100  includes a housing  1110 , a light emitting unit  1120 , a reflector  1130 , and a lens  1140 . 
     The housing  1110  has a cavity  1111  for accommodating the light emitting unit  1120 , the reflector  1130 , and the lens  1140 . 
     The housing  1110  may be formed of a plastic material having a light weight and high heat resistance, or a metal material having high thermal conductivity, such as, for example, aluminum. The inner wall of the housing  1110  may be coated with a reflective material capable of reflecting light emitted from the light emitting unit  1120 . In other embodiments, the housing  1110  may be formed of a reflective material that reflects light. 
     The light emitting unit  1120  is disposed in the housing  1110  and emits light. 
     The light emitting unit  1120  may include a board  1122  and a light emitting element  1124 . The light emitting unit  1120  may further include a resin layer  1126  for surrounding the light emitting element  1124 . The resin layer  1126  may protect the light emitting element  1124  and refract light emitted from the light emitting element  1124 . For example, the resin layer  1126  may serve as a lens for refracting light. 
     The board  1122  of the light emitting unit  1120  may be a plate-shaped structure on which the light emitting element  1124  and an element capable of supplying power to the light emitting element  1124 , controlling the light emitting element, or protecting the light emitting element may be mounted. 
     For example, the board  1122  may be a printed circuit board or a metal PCB. In  FIG. 10 , the board  1122  may have a cubic plate shape. However, embodiments are not limited thereto. The board may have a circular, elliptical, or polyhedral plate shape. 
     The light emitting element  1124  is disposed on one surface (e.g., the top surface) of the board  1122 . The light emitting element  1124  may be a light emitting diode (LED)-based light source, but is not limited thereto. For example, the light emitting element  1124  may take the form of an LED chip, or an LED package. 
     The number of the light emitting elements  124  may be one or more. While it is illustrated in  FIG. 10  that one light emitting element is disposed on the board  1122 , embodiments are not limited thereto. For example, in another embodiment, a plurality of light emitting elements may be disposed in a line on the board, or may be disposed in various shapes such as a circular shape or a matrix shape on the board  1122 . 
     The light emitting element  1124  may emit visible light or light in an infrared wavelength range. 
     For example, the light emitting element  1124  may emit light in a wavelength range of blue, red, or green. Alternatively, the light emitting element  1124  may emit light in a white wavelength range. 
     Alternatively, for example, the light emitting element  1124  may emit ultraviolet light having a wavelength range of 200 nm to 400 nm. Alternatively, for example, the light emitting element  1124  may generate ultraviolet-C (UVC) in a wavelength range of 200 nm to 280 nm. 
     When a plurality of light emitting elements is provided, the plurality of light emitting elements may emit rays in the same wavelength range or similar wavelength ranges. At least one of the plurality of light emitting elements may emit light in a different wavelength range. 
     The reflector  1130  may include a reflective surface  1132  disposed to surround the light emitting element  1124  and configured to reflect light emitted from the light emitting unit  1120 . 
     For example, the reflector  1130  may include a first opening  1130   a  adjacent to the light emitting unit  1120  and positioned at a lower end, a second opening  1130   b  positioned over the first opening  1130   a  and allowing light emitted from the light emitting unit  1120  to be output therethrough, and a reflective surface  1132  positioned between the first opening  1130   a  and the second opening  1130   b . The diameter of the second opening  1130   b  is greater than the diameter of the first opening  1130   a.    
     The first opening  1130   a  and the second opening  1130   b  shown in  FIG. 10  have a circular shape, but embodiments are not limited thereto. In another embodiment, they may have an elliptical shape or a polygonal shape. 
     The vertical cross-section of the reflective surface  1132  may have an elliptical shape or have a curvature of an ellipse. For example, the vertical cross-section of the reflective surface  1132  may be a plane passing through the center of the first opening  1130   a  and the center of the second opening  1130   b.    
     For example, in  FIG. 11 , the reflective surface  1132  and an extension line of the lower end of the reflective surface  1132  may form an ellipse EL. The extension line of the lower end of the reflective surface  1132  may form a vertex of the ellipse EL. 
     The light emitting element  1124  may be aligned to be positioned at the focus of the ellipse EL. 
     The light emitting unit  1120  may be disposed spaced apart from the reflective surface  1132 , and the center of the light emitting unit  1120  may be aligned with a vertical reference line  1101 . Here, the center of the light emitting unit  1120  may be the center of the light emitting element  1124 . The center of the light emitting element  1124  may be the center of the light emitting surface of the light emitting element  1124 . 
     The vertical reference line  1101  may be an imaginary line passing through the center of the reflector  1130  and the center of the lens  1140  and perpendicular to the top surface of the board  1122 . For example, the vertical reference line  1101  may be an imaginary line passing through the center of the first opening  1130   a  of the reflector  1130 , the center of the second opening  1130   b  and the center of the lens  1140  and perpendicular to the top surface of the board  1122 . 
     The reflector  1130  may include a reflective surface  1132  having a vertical cross-section in an elliptical shape, a side surface  1134  positioned opposite the reflective surface  1132 , and a lower surface  1134  positioned between the reflective surface  1132  and the side surface  1134 . 
     The reflector  1130  may be formed of a reflective metal, for example, stainless steel or silver (Ag). Alternatively, the reflector  1130  may be a metal material causing specular reflection. 
     Alternatively, the reflector  1130  may be formed of a resin material having high reflectivity, but embodiments are not limited thereto. 
     The lens  1140  is disposed in a space inside the reflective surface  1132  on the light emitting unit  1120 , and refracts and transmits light emitted from the light emitting unit  1120 . For example, the center of the lens  1140  may be aligned with the center of the light emitting unit  1120 , the center of the first opening  1130   a , and the center of the second opening  1130   b.    
     The lens  1140  may include a refractor  1142  which is convex in a direction pointing from the lower end to the upper end of the reflector  1130  or pointing from the light emitting unit  1120  to the lens  1140  and a support  1144  provided on the lower surface of the refractor  1142 . 
     The support  1144  of the lens  1140  may be coupled to a coupling groove  1122   a  provided on the top surface of the board  1122  and support the lens  1140 . For example, the support  1144  take the form of a leg connected to the lower surface of the refractor  1142  of the lens  1140 , and the number of the supports  1144  may be greater than or equal to two. One end of the support  1144  may be provided with an engagement portion to be coupled with the coupling groove  1122   a  of the board  1122 . 
     In  FIG. 10 , the number of the supports  1144  is four, but embodiments are not limited thereto. 
     For example, in order to suppress refraction of light emitted from the light emitting unit  120  caused by the supports  1144 , the supports  1144  may be spaced apart from each other and connected to the lower surface of the refractor  1142 . 
     While it is illustrated in  FIG. 10  that the supports  1144  of the lens  1140  are coupled to a groove  1122   a  provided in the board  122 , embodiments are not limited thereto. In another embodiment, the supports  1144  of the lens  1140  may be coupled to a groove (not shown) provided in the lower surface of the cavity  1111  of the housing  1110 . 
     In another embodiment, the groove  1122   a  may not be provided in the board  1122 , but the supports  1144  may be fixed to the board  1122  or the lower surface of the cavity  1111  of the housing  1110  by an adhesive member. 
       FIG. 12  shows light refracted by the lens  1140 . 
     The refractor  1142  of the lens  1140  may include an incidence surface  1142   a  and an exit surface  1142   b.    
     The incidence surface  1142   a  of the refractor  1142  of the lens  1140  may be a surface on which light emitted from the light emitting element  1124  is incident and refracted, and may be spaced apart from the reflective surface  1132 . 
     The exit surface  1142   b  of the refractor  1142  of the lens  1140  refracts and passes the light that has passed through the incidence surface  1142   a . The light that has passed through the incidence surface  1142   a  and the exit surface  1142   b  of the refractor  1142  of the lens  1140  may be converted into rays  1148  parallel to the direction pointing from the light emitting unit  1120  to the lens  1140 . 
     For example, the incidence surface  1142   a  of the lens  1140  may be a flat surface parallel to the top surface of the board  1122 , and the exit surface  1142   b  may have a hemispherical shape, a parabolic shape, or an elliptical shape that is convex in a direction pointing from the light emitting unit  1120  to the lens  1140 . However, embodiments are not limited thereto. In another embodiment, the incidence surface  1142   a  and the exit surface  1142   b  may be embodied in various shapes to convert the light passing through the incidence surface  1142   a  and the exit surface  1142   b  into parallel rays  1148 . 
     The inner space of the reflective surface  1132  and the space between the lens  1140  and the light emitting unit  1120  may be filled with a gas such as, for example, air, but embodiments are not limited thereto. In another embodiment, the spaces may be filled with a translucent material. 
     An edge  1142 - 1  of the lens  1140  may be spaced apart from an imaginary reference line  1102   a  connecting the center of the light emitting element  1124  and the uppermost end  1132 - 1  of the reflective surface  1132   a . Alternatively, the edge  1142 - 1  of the lens  1140  may be aligned with or adjacent to the imaginary reference line  1102   a.    
     If the edge  1142 - 1  of the lens  1140  overlaps the imaginary reference line  1102   a , the light reflected by the reflective surface  1132  and the light refracted by the lens  1140  may interfere with each other, and light may not be focused on a target as desired due to such light interference. 
     The edge  1142 - 1  of the lens  1140  may be the corner of the lens  1140  where the incidence surface  1142   a  of the lens  1140  and the exit surface  1142   b  adjoin each other. 
     When a plurality of light emitting elements  1124  is provided, the center of the light emitting elements  1124  may be the center of a region where the light emitting elements are distributed. 
     The light of the light emitting element  1124  emitted onto a first region S 11  of the reflector  1130  may be refracted by the lens  1140 , and the refracted light may be converted into rays  1148  parallel to a direction pointing from the light emitting unit  1120  to the lens  1140  and be output. 
     Here, the first region S 11  of the reflector  130  may be a region positioned on one side of the imaginary reference line  1102   a  connecting the center of the light emitting element  1124  and the uppermost end  1132 - 1  of the reflective surface  1132   a.    
     For example, the first region S 11  of the reflector  1130  may be an inner region of a closed curved surface (e.g., a cone) formed by the imaginary reference lines  1102   a  connecting the center of the light emitting element  1124  and the uppermost end  1132 - 1  of the reflective surface  1132   a.    
     For example, the light emitted from the light emitting element  1124  upward of the reference line  1102   a  may be refracted by the lens  1140 , and the refracted light may be converted into the rays  1148  parallel to the direction pointing from the light emitting unit  1120  to the lens  1140  and be output. 
       FIG. 13  shows light  1149  reflected by the reflective surface  1132  of the reflector  1130  shown in  FIG. 10 , and  FIG. 14  shows the size of the reflective surface  1132 , the size and position of the lens  1140 , and the size and position of a target Ta. 
     Referring to  FIGS. 13 and 14 , the light of the light emitting element  1124  emitted downward of the reference line  1102   a  is reflected by the reflective surface  1132  without being refracted by the lens  1140 . Since the reflective surface  1132  has an elliptical shape, the light  1149  reflected by the reflective surface  1132  may be condensed on the target Ta positioned at a certain distance. 
     The light of the light emitting element  1124  emitted downward of the reference line  1102   a  may pass through the vertical reference line  1101  by reflection on the reflective surface  1132  and be condensed on the target Ta or may be condensed on the target Ta so as to be aligned with the vertical reference line  1101 . 
     Referring to  FIGS. 12 and 13 , the diameter ED 1  of the first opening  1130   a  of the reflector  1130  may be 1.2×LD to 5.0×LD. For example, LD may be the diameter of the light emitting surface of the light emitting element  1124 , and ED 1  may be the diameter of the lowermost end of the reflective surface  1132 . 
     If the diameter ED 1  of the first opening  1130   a  is greater than or equal to 1.2×LD, light generated from the light emitting element  1124  may be transmitted to the reflective surface  1132  without loss. If the diameter ED 1  of the first opening  1130   a  is less than 1.2×LD, loss of the amount of light emitted from the light emitting element  1124  may occur. 
     If the diameter ED 1  of the first opening  1130   a  exceeds 5.0×LD, the diameter of the first opening  1130   a  is excessively large compared to the area of the light source to increase the loss of the light amount, thereby resulting in increase in loss of the light amount and thus decrease in optical power. 
     In an embodiment, the diameter TD of the target Ta may be 1.2×LD to 1.5×LD such that light may be condensed on the target Ta having a diameter similar to the diameter LD of the light emitting surface of the light emitting element  1124 . 
     The distance TH from the lower surface  1136  of the reflector  1130  to the target Ta may be 1.0×LD to 4.5×LD. 
     If TH is greater than 4.5×LD, the condensation distance is increased, and therefore the power of condensed light is reduced to below 40%. 
     If TH is less than 1.0×LD, the distance TH from the lower surface  1136  of the reflector  1130  to the target Ta may become too short to obtain the light condensation effect through the reflector  1130  and the lens  1140 . 
     The angle θ between the vertical reference line  1101  and the reference line  1102   a  is defined by Equation 4. 
     
       
         
           
             
               
                 
                   θ 
                   = 
                   
                     
                       tan 
                       
                         - 
                         1 
                       
                     
                     ( 
                     
                       
                         
                           ED 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                         2 
                       
                       EH 
                     
                     ) 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   4 
                 
               
             
           
         
       
     
     ED 2  may be the diameter of the second opening  1130   b . For example, ED 2  may be the diameter of the uppermost end of the reflective surface  1132 . 
     EH denotes the height of the reflector  1130 . For example, EH may be the distance from the lower surface  1136  of the reflector  1130  to the uppermost end  1132 - 1  of the reflective surface  1132 . 
     The angle θ between the vertical reference line  1101  and the reference line  1102   a  may be 30° to 51°. 
     If the angle θ is less than 30°, the focal length a 1  of the elliptical shape EL is increased and thus the amount of light falls. If the angle θ is greater than 51°, the focal length a 1  of the elliptical shape EL is reduced, and it is difficult to condense light. 
     The diameter LD 2  of the lens  1140  is defined by Equations 5 and 6.
 
 LD 2= k×B , and  Equation 5
 
 B= 2 ×LH 2×tan(θ),  Equation 6
 
     k denotes a constant related to interference of light rays, and may be 0.8≤k≤1. 
     When k=1, the edge  1142 - 1  of the lens  1140  may be aligned with the imaginary reference line  1102   a.    
     When k&gt;1, the edge  1142 - 1  of the lens  1140  overlaps the imaginary reference line  1102   a , and thus light interference may occur. 
     When k&lt;0.8, the diameter of the lens  1140  may become small, and the light condensing effect may not be obtained through by the lens  1140 . 
     LH 2  denotes the height of the lens  1140 . 
     For example, LH 2  may be the distance from the lower surface  1136  of the reflector  1130  to the incidence surface  1142   a  of the lens  1140 . 
     The height LH 2  of the lens  1140  is set to half the height EH of the reflector  1130 , in consideration of the fact that the lens  1140  has a curvature of an ellipse and the distance to the target Ta. The curvature of the lens  1140  may depend on the distance TH to the target. 
     That is, as the area in which the lens  1140  condenses light decreases, the height of the curvature of the lens  1140  may increase and the distance TH to the target Ta may increase. Considering the distance to the target at which the lens  1140  having an elliptical curvature can condense light, the embodiment may set LH 2  to half the height EH, thereby concentrating 25% to 60% of the light emitted from the light emitting element  1124  at the desired target Ta. 
     In Equation 6, when LH 2  is half the height EH of the reflector  1130 , B may be half the diameter of the uppermost end of the reflective surface  1132  or half the diameter ED 2  of the second opening  1130   b.    
     The light of the light emitting element  1124  emitted onto the second region S 12  of the reflector  1130  may be condensed in a target region by the reflector  1130 . 
     The embodiment may concentrate at least 40% of the total optical power of the light emitted from the lighting device in the target area even when the loss of light caused by the lens  1140  is considered. 
       FIG. 15  shows conditions for each case for the simulation result of  FIG. 16 , and  FIG. 16  shows a simulation result of light condensation of the lighting device according to  FIG. 15 . 
     LES denotes the diameter of the light emitting surface of the light emitting element  1124 . LES may be 3.5 mm, and the size of the target, e.g., the detector, may be 5 mm×5 mm. Here, the detector may measure the power or light amount of the received light. 
     F 1  and F 2  denote the focuses of an ellipse, R is the vertex radius of the ellipse, k is a conic constant, and F is the distance from the origin of the ellipse to the focus (or the light emitting element  1124 ). 
     The total collected power represents the collected power of the entire light output from the lighting device, and the detector collected power represents the power of light detected by the target Ta, for example, the detector, and the rate represents the ratio of the total collected power to the detector collected power. 
     The size of the target Ta, for example, the detector may be 1.2 times to 1.5 times the diameter of the light emitting surface. 
     Referring to  FIGS. 15 and 16 , the rate may be 40% or more in Cases 1 to 4, and θ may be 30° to 51°. 
       FIG. 17  shows conditions for each case for the simulation result of  FIG. 18 , and  FIG. 18  shows a simulation result of light condensation of a lighting device according to the conditions of  FIG. 17 . 
     LES may be 14.5 mm, and the size of the target, e.g., the detector, may be 18 mm×18 mm. 
     Referring to  FIGS. 17 and 18 , the rate may be 40% or more in Cases 1 to 4, and θ may be 30° to 51°. 
       FIG. 19  is a graph of the simulation results of  FIGS. 16 and 18 . 
     f 1  is a curve according to the simulation result in  FIGS. 16 , and f 2  is a curve according to the simulation result in  FIG. 18 . 
     Referring to  FIG. 19 , the value P 1  of θ at which the rate is 40% is 28°. 
     θ of the lighting device  100  according to the embodiment may be greater than or equal to 30° and less than or equal to 51° such that the rate is 40% or more in consideration of a margin of error of 2°. 
     When θ is greater than 51°, the height EH of the reflective surface  1132  becomes too small, and thus it is difficult for the reflective surface  1132  to have an elliptical shape, and thus light may not be condensed on a desired target. Therefore, the upper limit of θ is set to 51°. 
     When θ is 30° to 51°, the rate may be higher than or equal to 40% and lower than or equal to 68%. 
     θ may be set between 34° and 51° such that the rate is higher than 50%. 
     In order to make the rate higher than or equal to 60%, θ may be between 42° and 50°. 
     When an LED having a relatively small light amount compared to a lamp having a large light amount is used as a light source to concentrate the power of the light source on an optical fiber or a detector having a size similar to that of the light source, it is difficult to concentrate the power of the light source over the entire area of the detector using a simple reflector. 
     Embodiments have the following effects. 
     First, the amount of light lost to an optical system group may be reduced by using a condensing lens as a central lens of the reflector having an elliptical reflective surface for condensing light. 
     Second, an optical system that uses multiple lenses for condensing light typically exhibits system efficiency of about 70%, whereas embodiments may exhibit system efficiency of at least about 84% by using two optical elements, e.g., two lenses, and facilitate alignment of the optical axis. 
     Third, the size and position of the lens may be easily adjusted according to a rule based on the area and distribution of the light emitting element  1124 . 
     For a target Ta having TH of 1.0×LD to 4.5×LD and the diameter of 1.2×LD to 1.5×LD, embodiments may concentrate 40% or more of the total collected power of the amount of light output from the reflector  1130  on the target Ta. 
     The features, structures, effects and the like described in the embodiments are included in at least one embodiment of the present disclosure and are not necessarily limited to only one embodiment. Further, the features, structures, effects, and the like illustrated in the embodiments may be combined and modified for other embodiments by those having ordinary skill in the art to which the embodiments belong. Therefore, it is to be understood that these combinations and modifications should be understood as being within the scope of the present disclosure. 
     INDUSTRIAL APPLICABILITY 
     The embodiments may be used for a lighting device capable of uniformly condensing light on a target having a certain area.