Abstract:
A member for controlling luminous flux ( 100 ) has an incidence surface ( 110 ) and an emitting surface ( 120 ). The incidence surface ( 110 ) is a pyramidal surface having a recessed shape relative to the bottom of the member for controlling luminous flux ( 100 ), and having rounded borders between the individual facets. The horizontal cross-section of the incidence surface ( 110 ) is substantially similar in shape to that of an n-hedral irradiated surface ( 410 ). In the horizontal cross-section of the emitting surface ( 120 ), each of the straight lines connecting together adjacent angles of the n angles that correspond to the n angles of the irradiated surface ( 410 ) is substantially parallel to the side that corresponds to the horizontal cross-section of the incidence surface ( 110 ). The horizontal cross-section of the emitting surface ( 120 ) is the same as the n-hedron formed by the straight lines in the cross section, or fits inside the n-hedron.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a light flux controlling member that controls distribution of light emitted from a light emitting element. In addition, the present invention relates to a light emitting apparatus having the light flux controlling member and an illumination apparatus having the light emitting apparatus. 
       BACKGROUND ART 
       [0002]    In recent years, from the viewpoint of energy saving, light-emitting diodes (LEDs) have been used as light sources for lighting, in place of fluorescent lights, halogen lamps, and the like. 
         [0003]    When a surface to be irradiated is irradiated using a light-emitting diode, illuminance varies greatly between a location immediately below a light source (light-emitting diode) and a location separated from the light source. Therefore, when a wide surface to be irradiated is irradiated using one light-emitting diode, illuminance varies greatly between a location immediately below a light source and a rim part of the surface to be irradiated. As a method of uniformly illuminating a wide surface to be irradiated using a light-emitting diode, there has been consideration of the dense arrangement of a plurality of light-emitting diodes. However, such a method is not preferable from the viewpoint of energy saving. 
         [0004]    In addition, as another method of uniformly illuminating a wide surface to be irradiated using a light-emitting diode, there has been consideration of the expansion of the distribution of light emitted from the light-emitting diode using a lens (for example, see Patent Literature 1). Patent Literature 1 discloses a light emitting element unit including a light emitting element, and a lens unit that expands the distribution of light from the light emitting element. The lens unit includes an incidence surface on which the light from the light emitting element is incident, and an emission surface from which the light incident thereon from the incidence surface spreads out. The lens unit has a rotationally-symmetrical shape (circularly-symmetrical shape) using an optical axis of the light emitting element as a central axis. Therefore, the lens unit has a circular shape when seen in a plan view. It is possible to uniformly irradiate a wide surface to be irradiated with light from a light emitting element to a certain extent, by using the light emitting element unit disclosed in Patent Literature 1. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PTL 1 
         Japanese Patent Application Laid-Open No. 2009-152142 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0007]    When a planar surface to be irradiated is irradiated with light using the light emitting element unit disclosed in Patent Literature 1, an irradiation area of the light has a substantially circular shape. Therefore, when a rectangular surface to be irradiated is irradiated with light using the light emitting element unit disclosed in Patent Literature 1, there is a concern that four corners of the surface to be irradiated may be darkened. In addition, when there is an attempt to sufficiently irradiate the four corners of the surface with light, the light spreads more than necessary, and thus the light may be wasted. 
         [0008]    In this manner, when a light flux controlling member (lens) of the related art is used, it is not possible to effectively irradiate a polygonal-shaped surface to be irradiated with light emitted from a light emitting element. 
         [0009]    An object of the present invention is to provide a light flux controlling member that can uniformly and effectively irradiate a polygonal (n-sided polygon: n is an integer equal to or greater than 3) surface to be irradiated with light emitted from a light emitting element. In addition, another object of the present invention is to provide a light emitting apparatus having the light flux controlling member, and an illumination apparatus having the light emitting apparatus. 
       Solution to Problem 
       [0010]    There is provided a light flux controlling member that controls distribution of light emitted from a light emitting element, the member including: an incidence surface on which the light emitted from the light emitting element is incident; and an emission surface from which the light incident thereon from the incidence surface is emitted toward a surface to be irradiated which has an n-sided polygonal shape, in which the incidence surface is a pyramidal surface formed in a concave shape with respect to a bottom located on an opposite side to the emission surface, at a position of the bottom which corresponds to the light emitting element, the pyramidal surface being configured such that a boundary between surfaces thereof is an R surface, in which a shape of a cross-section of the incidence surface, the cross-section of the incidence surface being perpendicular to an optical axis of the light emitting element, is substantially similar to a shape of the surface to be irradiated, in which in a cross-section of the emission surface, the cross-section of the emission surface being perpendicular to an optical axis of the light emitting element, straight lines connecting corners adjacent to each other in n corners respectively corresponding to n corners of the surface to be irradiated are substantially parallel to corresponding sides of the cross-section of the incidence surface, and in which in the cross-section of the emission surface, the cross-section of the emission surface is the same as an n-sided polygon defined by the straight lines connecting the corners which are adjacent to each other in the n corners corresponding to the n corners of the surface to be irradiated, or is included in the n-sided polygon. 
         [0011]    There is also provided a light emitting apparatus including: the light flux controlling member; and a light emitting element, in which the light flux controlling member is disposed in such a manner that an optical axis of the light emitting element passes through an apex of the pyramidal surface. 
         [0012]    There is also provided an illumination apparatus including: the light emitting apparatus; and a polygonal-shaped surface to be irradiated which is irradiated with light from the light emitting apparatus, in which the light emitting apparatus is disposed in such a manner that the optical axis of the light emitting element and the surface to be irradiated are perpendicular to each other. 
       Advantageous Effects of Invention 
       [0013]    A light emitting apparatus including a light flux controlling member of the present invention can uniformly and effectively irradiate a polygonal-shaped surface to be irradiated with light emitted from a light emitting element. In addition, an illumination apparatus of the present invention can uniformly and effectively illuminate a polygonal-shaped surface to be irradiated with light. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1A  is a top perspective view of an illumination lens according to Embodiment 1, and  FIG. 1B  is a bottom perspective view of the illumination lens according to Embodiment 1; 
           [0015]      FIG. 2A  is a plan view of the illumination lens according to Embodiment 1, and  FIG. 2B  is a bottom view of the illumination lens according to Embodiment 1; 
           [0016]      FIG. 3A  is a cross-sectional view taken along line A-A illustrated in  FIG. 2A ,  FIG. 3B  is a cross-sectional view taken along line B-B illustrated in  FIG. 2A , and  FIG. 3C  is a cross-sectional view taken along line C-C illustrated in  FIG. 2A ; 
           [0017]      FIG. 4  is a bottom view of the illumination lens according to Embodiment 1 for illustrating a roughened region; 
           [0018]      FIG. 5  is a cross-sectional view taken along line D-D illustrated in  FIG. 3B ; 
           [0019]      FIG. 6  is a cross-sectional view of an illumination lens having an incidence surface that does not include an R surface; 
           [0020]      FIG. 7A  is a diagram illustrating illuminance distribution when the illumination lens according to Embodiment 1 is used, and  FIG. 7B  is a diagram illustrating illuminance distribution when an illumination lens of the related art is used: 
           [0021]      FIG. 8A  is a plan view of the illumination lens of the related art,  FIG. 8B  is a bottom view of the illumination lens of the related art, and  FIG. 8C  is a cross-sectional view taken along line F-F illustrated in  FIG. 8A ; 
           [0022]      FIG. 9A  is a top perspective view of an illumination lens for comparison, and  FIG. 9B  is a bottom perspective view of the illumination lens for comparison; 
           [0023]      FIG. 10A  is a top perspective view of an illumination lens for comparison, and  FIG. 10B  is a bottom perspective view of the illumination lens for comparison; 
           [0024]      FIG. 11A  is a top perspective view of an illumination lens for comparison, and  FIG. 11B  is a bottom perspective view of the illumination lens for comparison; 
           [0025]      FIG. 12A  is a top perspective view of an illumination lens for comparison, and  FIG. 12B  is a bottom perspective view of the illumination lens for comparison; 
           [0026]      FIG. 13A  is a top perspective view of an illumination lens for comparison, and  FIG. 13B  is a bottom perspective view of the illumination lens for comparison: 
           [0027]      FIG. 14  is a perspective view of an illumination apparatus according to Embodiment 1; 
           [0028]      FIG. 15A  is a graph illustrating light distribution of a light emitting apparatus according to Embodiment 1, and  FIG. 15B  is a side view of the illumination apparatus according to Embodiment 1; 
           [0029]      FIG. 16A  is a plan view of an illumination lens according to Embodiment 2, and  FIG. 16B  is a bottom view of the illumination lens according to Embodiment 2; 
           [0030]      FIG. 17  is a side view of the illumination lens according to Embodiment 2; 
           [0031]      FIG. 18A  is a cross-sectional view taken along line A-A illustrated in  FIG. 16A ,  FIG. 18B  is a cross-sectional view taken along line B-B illustrated in  FIG. 16A , and  FIG. 18C  is a cross-sectional view taken along line C-C illustrated in  FIG. 16A ; 
           [0032]      FIG. 19A  is a cross-sectional view taken along line D-D illustrated in  FIG. 18B , and  FIG. 19B  is a cross-sectional view taken along line E-E illustrated in  FIG. 18B ; and 
           [0033]      FIG. 20A  is a diagram illustrating illuminance distribution when the illumination lens according to Embodiment 2 is used, and  FIG. 20B  is a diagram illustrating illuminance distribution when the illumination lens according to Embodiment 1 is used. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0034]    Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, as representative examples of a light flux controlling member of the present invention, an illumination lens will be described which can effectively irradiate a square (n-sided polygon: n=4)-shaped surface to be irradiated with light emitted from a light emitting element. 
         [0035]    Meanwhile, “square-shaped surface to be irradiated” in this specification is a surface that is to be irradiated with light, and refers to a surface having a square-shaped irradiation area of light. Therefore, the “square-shaped surface to be irradiated” is not limited to a square-shaped flat plate. For example, when a circular flat plate is irradiated with light in a square shape, a surface to be irradiated with light corresponds to a “square-shaped surface to be irradiated”. 
       Embodiment 1 
     Configuration of Illumination Lens and Light Emitting Apparatus 
       [0036]      FIG. 1  to  FIG. 5  are diagrams illustrating a configuration of illumination lens  100  according to Embodiment 1.  FIG. 1A  is a top perspective view of illumination lens  100 , and  FIG. 1B  is a bottom perspective view of illumination lens  100 .  FIG. 2A  is a plan view of illumination lens  100 ,  FIG. 2B  and  FIG. 4  are bottom views of illumination lens  100 .  FIG. 3A  is a cross-sectional view taken along line A-A illustrated in  FIG. 2A ,  FIG. 3B  is a cross-sectional view taken along line B-B illustrated in  FIG. 2A , and  FIG. 3C  is a cross-sectional view taken along line C-C illustrated in  FIG. 2A .  FIG. 5  is a cross-sectional view taken along line D-D illustrated in  FIG. 38 . 
         [0037]    Meanwhile,  FIG. 3A  illustrates light emitting element  200  together with illumination lens  100 . That is,  FIG. 3A  is a cross-sectional view of light emitting apparatus  300  according to Embodiment 1. 
         [0038]    As illustrated in  FIG. 1  to  FIG. 3 , illumination lens  100  includes incidence surface  110  on which light emitted from light emitting element  200  is incident, emission surface  120  from which the light incident thereon from incidence surface  110  is emitted toward a square (n-sided polygon: n=4)-shaped surface to be irradiated, flange  130  that is provided in an outer peripheral part, and cylindrical foot  140  that is provided on the bottom surface side of flange  130 . 
         [0039]    Illumination lens  100  is formed by integral molding. A material of illumination lens  100  is not particularly limited as long as it is a material capable of transmitting light having a desired wavelength. For example, the material of illumination lens  100  is a light-transmissive resin such as polymethylmethacrylate (PMMA), polycarbonate (PC), or epoxy resin (EP), or is glass. 
         [0040]    Illumination lens  100  is attached onto a substrate (not shown) to which light emitting element  200  is fixed, so that central axis CA is consistent with an optical axis of light emitting element  200  (see  FIG. 3A ). Flange  130  and foot  140  are provided in order to fix illumination lens  100  to the substrate. Illumination lens  100  and light emitting element  200  constitute light emitting apparatus  300 . For example, light emitting element  200  is a light-emitting diode (LED) such as a white light-emitting diode. 
         [0041]    Incidence surface  110  of illumination lens  100  is an inner surface of concave part  111  that is formed on the bottom (located on the opposite side to emission surface  120 ) of illumination lens  100 . Concave part  111  has a substantially quadrangular pyramid shape. That is, incidence surface  110  is formed at a position corresponding to light emitting element  200  at the bottom of illumination lens  100 , and is a concave quadrangular pyramid surface (side surface of quadrangular pyramid) with respect to the bottom of illumination lens  100 . The shape of an opening part of concave part  111  (the shape of bottom surface of quadrangular pyramid) is substantially similar to the shape (square) of a surface to be irradiated. In addition, the shape of a cross-section of incidence surface  110  at an arbitrary position in a direction (hereinafter, referred to as “horizontal direction”) which is perpendicular to central axis CA (optical axis of light emitting element) of illumination lens  100  is also substantially similar to the shape (square) of the surface to be irradiated. Here, the “arbitrary position” is a position that crosses each flat surface  112  (flat surface that is not R surface  113  to be described later) of concave part  111 . In addition, as described later, the quadrangular pyramid is R-chamfered, and an R part is formed in a corner part of the cross-section of incidence surface  110  in the horizontal direction. Therefore, the shape of the cross-section of incidence surface  110  in the horizontal direction is “substantially” similar to the shape (square) of the surface to be irradiated. 
         [0042]    A boundary (ridge line and apex) between flat surface  112  of concave part  11   l  is constituted by R surface  113  (see  FIG. 2B ). Therefore, the shape of a cross-section of concave part  111  in the horizontal direction in the vicinity of an apex part has a small straight-line part, and thus is close to a circular shape. When the boundary between flat surfaces  112  of incidence surface  110  is not R surface  113 , it is not possible to direct light onto a central part and a diagonal line of the surface to be irradiated, and thus illuminance unevenness may occur. A radius of R surface  113  is not particularly limited as long as it can prevent the illuminance unevenness of the surface to be irradiated from occurring. For example, the radius of R surface  113  is set as follows. 
         [0043]    As illustrated in  FIG. 6 , it is assumed that light is incident on an incidence surface that does not include an R surface. When light (solid line) which is emitted in an optical axis direction from light-emitting point O (point on the optical axis) of a light emitting element  200  is incident on incidence surface S 1  shown on the left side of  FIG. 6 , the light reaches point A 1  on a surface to be irradiated via point B 1  on an emission surface  120 . On the other hand, when the light (solid line) which is emitted in the optical axis direction from light-emitting point O of the light emitting element  200  is incident on incidence surface S 2  shown on the right side of  FIG. 6 , the light reaches point A 2  on the surface to be irradiated via point B 2  on the emission surface  120 . At this time, a region between point A 1  and point A 2  on the surface to be irradiated becomes a dark part due to the lack of the amount of light. An R surface is formed so that the region does not become a dark part. 
         [0044]    When an intersection point between line segment OB 1  and incidence surface S 1  is set as b 1  and an intersection point between line segment OB 2  and incidence surface S 2  is set as b 2 , a radius of an inscribed circle using point b 1  and point b 2  as contact points serves as a minimum radius of the R surface. The R surface is formed in this manner, and thus light also reaches a region between point B 1  and point B 2  of the emission surface, which allows the region between point A 1  and point A 2  of the surface to be irradiated to be irradiated with light. 
         [0045]    The radius of the R surface is set to be equal to or greater than the above-mentioned minimum radius, and thus it is possible to suppress the generation of a dark part in the surface to be irradiated. In order to more reliably suppress the generation of a dark part, it is preferable to set a radius of an inscribed circle, which uses point a 1  and point a 2  illustrated in  FIG. 6  as contact points, to the radius of the R surface. Here, point a 1  is an intersection point between line segment OA 1  and incidence surface S 1 , and point a 2  is an intersection point between line segment OA 2  and incidence surface S 2 . Meanwhile, when the shape of incidence surface  110  becomes closer to a spherical surface by increasing the size of the region of the R surface more than necessary, it is not possible to distribute emitted light in the vicinity of the optical axis in a peripheral direction of the surface to be irradiated, and thus a dark part may be generated in the central part of the surface to be irradiated. 
         [0046]    Herein, the radius of the R surface in the apex part of the pyramidal surface has been described, but the same is true of a radius of a ridge line part of the pyramidal surface. 
         [0047]    Incidence surface  110  will be described again. In R surface  113  of the ridge line part of the pyramidal surface, a region (region shown as “E” in  FIG. 4 ) in the vicinity of the apex is roughened. The region is roughened in this manner, and thus it is possible to prevent cruciform (X-shaped) illuminance unevenness from occurring in the surface to be irradiated. Meanwhile, when the entirety of R surface  113  is roughened, there is a concern that illuminance in four corners of the surface to be irradiated may be reduced. 
         [0048]    As described above, illumination lens  100  is disposed such that central axis CA is consistent with the optical axis of light emitting element  200 . At this time, the optical axis of light emitting element  200  passes through the apex of the pyramidal surface (incidence surface  110 ) (see  FIG. 3A ). 
         [0049]    In illumination lens  100 , emission surface  120  is located on the opposite side to incidence surface  110 . The shape of the cross-section (cross-section in a direction perpendicular to the optical axis) of emission surface  120  in the horizontal direction is substantially similar to the shape (square) of the surface to be irradiated (see  FIG. 5 ). 
         [0050]    Both the shape of the cross-section of incidence surface  110  in the horizontal direction and the shape of the cross-section of emission surface  120  in the horizontal direction are similar to the shape (square) of the surface to be irradiated. At this time, directions of the two substantially squares are consistent with each other. That is, in the cross-section of emission surface  120  illustrated in  FIG. 5  in a horizontal direction, straight lines (C 1 -C 2 , C 2 -C 3 , C 3 -C 4 , and C 4 -C 1 ) connecting corners adjacent to each other in four (n=4) corners C 1  to C 4  respectively corresponding to four (n=4) corners of the surface to be irradiated are substantially parallel to the corresponding sides of the cross-section (square) of incidence surface  110  in the horizontal direction. In addition, a positional relationship between illumination lens  100  and the surface to be irradiated shows that the sides in the cross-section of incidence surface  110  in the horizontal direction and the straight lines (C 1 -C 2 , C 2 -C 3 , C 3 -C 4 , and C 4 -C 1 ) in the cross-section of emission surface  120  in the horizontal direction are disposed so as to be substantially parallel to sides of the surface to be irradiated which correspond to the sides in the cross-section of the incidence surface. 
         [0051]    Meanwhile, in the cross-section of emission surface  120  illustrated in  FIG. 5  in a horizontal direction, the cross-section of emission surface  120  has the same shape as (overlaps with) a quadrangle defined by the straight lines (C 1 -C 2 , C 2 -C 3 , C 3 -C 4 , and C 4 -C 1 ) connecting the corners adjacent to each other in four (n=4) corners C 1  to C 4  corresponding to the four corners (n=4) of the surface to be irradiated. 
         [0052]    As illustrated in  FIG. 3A  and  FIG. 3B , four (n=4) curved surfaces constituting emission surface  120  are curved surfaces that are convex with respect to flat surface  112  (corresponding flat surface  112 ) that is the closest thereto, in four (n=4) flat surfaces  112  constituting incidence surface  110 . In addition, the four (n=4) curved surfaces constituting emission surface  120  do not have a curvature in the horizontal direction (see  FIG. 5 ). That is, each of the four curved surfaces constituting emission surface  120  is a straight line in the cross-section of emission surface  120  in a horizontal direction. In this case, a configuration is provided in which four cylindrical lenses are disposed in the vicinity of light emitting element  200 . In this manner, it is possible to condense light toward a rim part of the surface to be irradiated. In addition, unlike incidence surface  110 , a boundary between the four (n=4) curved surfaces constituting emission surface  120  does not have an R surface (see  FIG. 1A ). However, a minimum R surface that is required when processing a mold may be formed. 
         [0053]    Flange  130  and foot  140  support illumination lens  100 . As described above, flange  130  and foot  140  are provided in order to fix illumination lens  100  to the substrate. Therefore, flange  130  and foot  140  having a shape capable of accomplishing the object are not particularly limited to the shape shown in this embodiment, as long as they have a shape that does not exert adverse influences on optical properties. 
         [0054]    It is possible to reduce an amount of light that is directed in the optical axis direction of light emitting element  200  and to increase an amount of light that is directed to the four corners of the surface to be irradiated, by using illumination lens  100  according to Embodiment 1. As a result, it is possible to uniformly and effectively irradiate the square-shaped surface to be irradiated with light from the light emitting element, by using illumination lens  100  according to Embodiment 1. 
         [0055]      FIG. 7A  is a diagram illustrating illuminance distribution when a square-shaped surface to be irradiated is irradiated by using light emitting apparatus  300  including illumination lens  100  and light emitting element  200  according to Embodiment 1. In this experiment, an interval between light emitting element  200  and the surface to be irradiated is set to 250 mm. In addition, a size of the surface to be irradiated is set to 500 mm×500 mm. 
         [0056]    The size of each part of illumination lens  100  (made of PMMA) that is used in this experiment is as follows. 
         [0057]    The length of one side of incidence surface  110  (substantially square) when seen in a plan view: 8.2 mm 
         [0058]    The length of one side of emission surface  120  (square) when seen in a plan view: 7.67 mm 
         [0059]    The height from the opening part of concave part  111  to the apex of emission surface  120 : 4 mm 
         [0060]    The radius of R surface  113 : 2 mm 
         [0061]    In  FIG. 7A , the square-shaped surface to be irradiated (500 mm×500 mm) is colored. Each numerical value is illuminance (unit: lx) in the relevant part. As illustrated in  FIG. 7A , when illumination lens  100  according to Embodiment 1 is used, it is possible to uniformly irradiate the inside of the square-shaped surface to be irradiated with light (192 lx to 266 lx). On the other hand, parts other than the surface to be irradiated are barely irradiated with light (12× to 35×). Thus, it is seen that the square-shaped surface to be irradiated is uniformly and effectively irradiated. 
         [0062]      FIG. 7B  is a diagram illustrating illuminance distribution when a square-shaped surface to be irradiated is irradiated, by using a light emitting apparatus including an illumination lens of the related art and a light emitting element. In this experiment, illumination lens  10  (made of PMMA) illustrated in  FIG. 8  is used as the illumination lens of the related art. 
         [0063]      FIG. 8A  is a plan view of the illumination lens of the related art, FIG. SB is a bottom view of the illumination lens of the related art, and  FIG. 8C  is a cross-sectional view taken along line F-F illustrated in  FIG. 8A . A diameter of incidence surface  11  (circle) when seen in a plan view is substantially the same as a diameter of an inscribed circle of incidence surface  110  (substantially square) when seen in a plan view of illumination lens  100  according to the embodiment. In addition, a diameter of emission surface  12  (circle) when seen in a plan view is approximately the same as a diameter of a circumscribed circle of emission surface  120  (square), when seen in a plan view, of illumination lens  100  according to the embodiment. 
         [0064]    As illustrated in  FIG. 7B , when illumination lens  10  of the related art is used, the illuminance of each of four corners of the square-shaped surface to be irradiated is lower than that of the central part thereof, and thus illuminance unevenness occurs. In addition, since parts other than the surface to be irradiated are irradiated with light (35× to 73×), the illuminance of the inside of the surface to be irradiated was lower than that of illumination lens  100  according to Embodiment 1 (66 lx to 136 lx). 
         [0065]    In this manner, it is possible to uniformly and effectively irradiate the square-shaped surface to be irradiated with light from light emitting element  200 , as compared with illumination lens  10  of the related art, by using illumination lens  100  according to Embodiment 1. 
         [0066]    Meanwhile, the inventors have also performed the same experiment on illumination lenses having shapes illustrated in  FIG. 9  to  FIG. 13 . 
         [0067]    The illumination lens illustrated in  FIG. 9  is different from illumination lens  100  according to Embodiment 1 in that a horizontal section of emission surface  120  has a circular shape.  FIG. 9A  is a top perspective view, and  FIG. 9B  is a bottom perspective view. When the illumination lens illustrated in  FIG. 9  was used, four corners of a square-shaped surface to be irradiated were darkened. 
         [0068]    The illumination lens illustrated in  FIG. 10  is different from illumination lens  100  according to Embodiment 1 in that incidence surface  110  is a circular conical surface (the vicinity of the apex is constituted by an R surface).  FIG. 10A  is a top perspective view, and  FIG. 10B  is a bottom perspective view. When the illumination lens illustrated in  FIG. 10  was used, a central region of a square-shaped surface to be irradiated was darkened. 
         [0069]    The illumination lens illustrated in  FIG. 11  is different from illumination lens  100  according to Embodiment 1 in that an R surface is not present (ridge line is present) in a boundary between surfaces of incidence surface  110 .  FIG. 11A  is a top perspective view, and  FIG. 11B  is a bottom perspective view. When the illumination lens illustrated in  FIG. 11  was used, a central region of a square-shaped surface to be irradiated and a region in the vicinity of a diagonal line were darkened. 
         [0070]    The illumination lens illustrated in  FIG. 12  is different from illumination lens  100  according to Embodiment 1 in that an R surface is present (ridge line is not present) in a boundary between surfaces of emission surface  120  and that an R surface is not present (ridge line is present) in a boundary between surfaces of incidence surface  110 .  FIG. 12A  is a top perspective view, and  FIG. 12B  is a bottom perspective view. Even when the illumination lens illustrated in  FIG. 12  was used, a central region of a square-shaped surface to be irradiated and a region in the vicinity of a diagonal line were darkened. 
         [0071]    The illumination lens illustrated in  FIG. 13  is different from illumination lens  100  according to Embodiment 1 in that a square formed by an outer rim of incidence surface  110  and a square formed by an outer rim of the emission surface deviate by 45 degrees when illumination lens  100  is seen in a plan view, and that an R surface is not present (ridge line is present) in a boundary between surfaces of incidence surface  110 .  FIG. 13A  is a top perspective view, and  FIG. 13B  is a bottom perspective view. When the illumination lens illustrated in  FIG. 13  was used, light was condensed on a central region of a square-shaped surface to be irradiated and a region in the vicinity of a diagonal line. 
         [0072]    The above experimental results show that it is important to satisfy conditions 1) to 3) below in order to uniformly and effectively irradiate the square-shaped surface to be irradiated. 
         [0073]    1) Incidence surface  110  is a pyramidal surface in which a boundary between surfaces thereof is an R surface. 
         [0074]    2) The shape of a horizontal section of incidence surface  110  is substantially similar to the shape of the surface to be irradiated. 
         [0075]    3) Four corners of a horizontal section of emission surface  120  correspond to four corners of the horizontal section of incidence surface  110 . That is, in the horizontal section of emission surface  120 , straight lines connecting corners adjacent to each other in the four corners corresponding to four corners of the surface to be irradiated are substantially parallel to corresponding sides of the horizontal section of incidence surface  110 . 
         [0076]    [Configuration of Illumination Apparatus] 
         [0077]    Next, an illumination apparatus including light emitting apparatus  300  according to Embodiment 1 will be described. 
         [0078]      FIG. 14  is a perspective view of illumination apparatus  400  according to Embodiment 1. As illustrated in  FIG. 14 , illumination apparatus  400  includes light emitting apparatus  300  and square surface  410  to be irradiated. As described above, light emitting apparatus  300  includes illumination lens  100  and light emitting element  200 . 
         [0079]    Surface  410  to be irradiated is a square (n-sided polygon: n=4)-shaped flat surface. Light emitting apparatus  300  is disposed in such a manner that surface  410  to be irradiated is perpendicular to central axis CA of illumination lens  100  and the optical axis of light emitting element  200  (see  FIG. 3A ). At this time, central axis CA of illumination lens  100  and the optical axis of light emitting element  200  pass through a central part of surface  410  to be irradiated. 
         [0080]    As described above, both the horizontal section of incidence surface  110  and the horizontal section of emission surface  120  of illumination lens  100  have a substantially square shape. Here, light emitting apparatus  300  is disposed in such a manner that sides of these two squares and sides of surface  410  to be irradiated are parallel to each other. 
         [0081]    Illumination apparatus  400  is used by irradiating surface  410  to be irradiated with light that is emitted from light emitting apparatus  300 . Light emitting apparatus  300  according to Embodiment 1 uniformly irradiates square surface  410  to be irradiated and does not nearly irradiate parts other than surface  410  to be irradiated. Therefore, illumination apparatus  400  can uniformly and effectively illuminate square surface  410  to be irradiated. 
         [0082]      FIG. 15A  is a graph illustrating the light distribution of light emitting apparatus  300  according to Embodiment 1 (measured angle 0 degrees). In addition,  FIG. 15B  is a side view of illumination apparatus  400  according to Embodiment 1. 
         [0083]    As illustrated in FIG. ISA, light emitting apparatus  300  according to Embodiment 1 has the highest illuminance at a predetermined angle ±θ a  (in the graph of  FIG. 15A , approximately ±50 degrees). The value of θ a  varies according to an angle of incidence surface  110  with respect to a substrate surface of light emitting element  200  and a curvature of each surface of emission surface  120 . As illustrated in  FIG. 15B , when an angle of a line, which connects light emitting apparatus  300  and an end part of surface  410  to be irradiated, with respect to the central axis (consistent with central axis CA of illumination lens  100 ) of light emitting apparatus  300  is set to θ L , it is preferable to dispose light emitting apparatus  300  so that the relation of θ L &gt;θ a  is established, in order to effectively irradiate surface  410  to be irradiated. 
       Effects 
       [0084]    Illumination lens  100 , light emitting apparatus  300 , and illumination apparatus  400  according to Embodiment 1 can uniformly and effectively irradiate square surface  410  to be irradiated with light that is emitted from light emitting element  200 . 
       Embodiment 2 
     Configuration of Illumination Lens and Light Emitting Apparatus 
       [0085]      FIG. 16  to  FIG. 19  are diagrams illustrating a configuration of illumination lens  500  according to Embodiment 2.  FIG. 16A  is a plan view of illumination lens  500 , and  FIG. 16B  is a bottom view of illumination lens  500 .  FIG. 17  is a side view of illumination lens  500 .  FIG. 18A  is a cross-sectional view taken along line A-A illustrated in  FIG. 16A ,  FIG. 18B  is a cross-sectional view taken along line B-B illustrated in  FIG. 16A , and  FIG. 18C  is a cross-sectional view taken along line C-C illustrated in  FIG. 16A .  FIG. 19A  is a cross-sectional view taken along line D-D illustrated in  FIG. 181 , and  FIG. 19B  is a cross-sectional view taken along line E-E illustrated in  FIG. 18B . 
         [0086]    Meanwhile,  FIG. 18A  illustrates light emitting element  200  together with illumination lens  500 . That is,  FIG. 18A  is a cross-sectional view of light emitting apparatus  600  according to Embodiment 2. 
         [0087]    As illustrated in  FIG. 16  to  FIG. 19 , similarly to illumination lens  100  according to Embodiment 1, illumination lens  500  according to Embodiment 2 includes incidence surface  110 , emission surface  510 , flange  130 , and foot  140 . Illumination lens  500  and light emitting apparatus  600  according to Embodiment 2 are substantially the same as illumination lens  100  and light emitting apparatus  300  according to Embodiment 1 (radius of R surface of incidence surface, etc. are slightly different), with regard to components other than the emission surface of the illumination lens. Consequently, the same components as illumination lens  100  and light emitting apparatus  300  according to Embodiment 1 are denoted by the same reference numerals, and a description thereof will not be repeated. 
         [0088]    In illumination lens  500 , emission surface  510  is located on the opposite side to incidence surface  110 . As illustrated in  FIG. 17 , emission surface  510  is constituted by four surfaces  510   a  that are located on the upper side (in a travelling direction of light on the optical axis), and four surfaces  510   b  that are located on the lateral side (on flange  130  side). Four surfaces  510   a  that are located on the upper side have the same shape as a part of emission surface  120  of illumination lens  100  according to Embodiment 1 (refer to comparison between  FIG. 3A  and  FIG. 18A ). On the other hand, four surfaces  510   b  that are located on the lateral side are surfaces which are substantially parallel to the optical axis (surfaces that are substantially perpendicular to flange  130 ). The shape of a cross-section of an upper part of emission surface  510  in the horizontal direction is substantially similar to the shape (square) of a surface to be irradiated (see  FIG. 19B ). On the other hand, the shape of a cross-section of a lower part of emission surface  510  in the horizontal direction is not substantially similar to the shape (square) of the surface to be irradiated (see  FIG. 19A ). 
         [0089]    The positions of four (n=4) corners C 1  to C 4  in the cross-section of emission surface  510  in a horizontal direction, which correspond to four (n=4) corners of the surface to be irradiated, correspond to four (n=4) corners in the cross-section of incidence surface  110  in the horizontal direction. That is, in the cross-sections of emission surfaces  510  ( 510   a  and  510   b ) illustrated in  FIG. 19A  and  FIG. 19B , straight lines (C 1 -C 2 . C 2 -C 3 , C 3 -C 4 , and C 4 -C 1 ) connecting corners adjacent to each other in four (n=4) corners C 1  to C 4  respectively corresponding to the four (n=4) corners of the surface to be irradiated are substantially parallel to the corresponding sides of the cross-section (square) of incidence surface  110  in the horizontal direction. A positional relationship between illumination lens  500  and the surface to be irradiated shows that sides in the cross-section of incidence surface  110  in the horizontal direction and the straight lines (C 1 -C 2 , C 2 -C 3 , C 3 -C 4 , and C 4 -C 1 ) in the cross-section of emission surface  510  in the horizontal direction are disposed so as to be substantially parallel to the sides of the surface to be irradiated which correspond to the sides in the cross-section of the incidence surface. 
         [0090]    In the cross-section of the lower part of emission surface  510  illustrated in  FIG. 19A  in a horizontal direction, the cross-section of emission surface  510  ( 510   b ) is included within a quadrangle defined by the straight lines (C 1 -C 2 , C 2 -C 3 , C 3 -C 4 , and C 4 -C 1 ) connecting corners adjacent to each other in the four (n=4) corners C 1  to C 4  which correspond to the four (n=4) corners of the surface to be irradiated. On the other hand, in the cross-section of the upper part of emission surface  510  illustrated in  FIG. 198  in a horizontal direction, the cross-section of emission surface  510  ( 510   a ) is the same as (overlaps with) the quadrangle defined by the straight lines (C 1 -C 2 , C 2 -C 3 , C 3 -C 4 , and C 4 -C 1 ) connecting the corners adjacent to each other in the four (n=4) corners C 1  to C 4  which correspond to the four (n=4) corners of the surface to be irradiated. 
         [0091]    As illustrated in  FIG. 18A  and  FIG. 18B , in eight surfaces constituting emission surface  510 , four curved surfaces  510   a  coming into contact with the optical axis (central axis CA of illumination lens  500 ) of the light emitting element and respectively corresponding to four (n=4) flat surfaces  112  constituting incidence surface  110  are curved surfaces having a convex shape with respect to flat surface  112  (corresponding flat surface  112 ) which is the closest thereto. In addition, these four (n=4) curved surfaces  510   a  does not have a curvature in the horizontal direction (see  FIG. 19B ). That is, in the cross-section (cross-section in the horizontal direction) which is perpendicular to central axis CA of illumination lens  500 , each of four (n=4) curved surfaces  510   a  is a straight line. 
         [0092]    In this case, a configuration is provided in which four cylindrical lenses are disposed in the vicinity of light emitting element  200 . In this manner, it is possible to condense light toward a rim part of the surface to be irradiated. In addition, a boundary between these four (n=4) curved surfaces  510   a  does not have an R surface (see  FIG. 16A ). 
         [0093]    Similarly to illumination lens  100  according to Embodiment 1, it is possible to uniformly and effectively irradiate the square-shaped surface to be irradiated with light from the light emitting element by using illumination lens  500  according to Embodiment 2. 
         [0094]      FIG. 20A  is a diagram illustrating illuminance distribution when a square-shaped surface to be irradiated is illuminated, by using light emitting apparatus  600  including illumination lens  500  and light emitting element  200  according to Embodiment 2. In addition,  FIG. 20B  is a diagram illustrating illuminance distribution when a square-shaped surface to be irradiated is illuminated, by using light emitting apparatus  300  including illumination lens  100  and light emitting element  200  according to Embodiment 1. 
         [0095]    As illustrated in  FIG. 20A  and  FIG. 20B , even when illumination lens  100  according to Embodiment 1 is used and even when illumination lens  500  according to Embodiment 2 is used, the inside of a square-shaped surface to be irradiated can be irradiated with light in a substantially uniform manner. On the other hand, parts other than the surface to be irradiated are not nearly irradiated with light. In addition, comparing  FIG. 20A  and  FIG. 20B , when illumination lens  500  according to Embodiment 2 is used, parts other than the surface to be irradiated are further prevented from being irradiated with light than a case where illumination lens  100  according to Embodiment 1 is used, and thus the square-shaped surface to be irradiated is more effectively irradiated. In the measurement results illustrated in  FIG. 20A  and  FIG. 20B , when illuminance values (in the drawing, measurement values surrounded by a double line) of measurement points between an outermost rim of a measurement area and a colored surface to be irradiated are compared with each other, the illuminance values in a case (59 to 131) where illumination lens  500  according to Embodiment 2 is used are lower than those in a case (151 to 204) where illumination lens  100  according to Embodiment 1 is used. This shows that illumination lens  500  according to Embodiment 2 has a greater effect of controlling an irradiation region to a square shape than illumination lens  100  according to Embodiment 1. 
       Effects 
       [0096]    Similarly to illumination lens  100 , light emitting apparatus  300 , and illumination apparatus  400  according to Embodiment 1, illumination lens  500  and light emitting apparatus  600  according to Embodiment 2 and the illumination apparatus (not shown; see  FIG. 14 ) which includes light emitting apparatus  600  according to Embodiment 2 can uniformly and effectively irradiate a square-shaped surface to be irradiated with light that is emitted from light emitting element  200 . 
         [0097]    Meanwhile, in the above-mentioned embodiments, illumination lenses  100  and  500 , light emitting apparatuses  300  and  600 , and illumination apparatus  400  which are used to irradiate a square (n-sided polygon: n=4)-shaped surface to be irradiated have been described, but the illumination lens, the light emitting apparatus, and the illumination apparatus of the present invention are not limited thereto. The shape of the surface to be irradiated is not particularly limited as long as it is a polygonal shape (n-sided polygon: n is an integer equal to or greater than 3), and may be a triangular shape (n=3), a pentagonal shape (n=5), a hexagonal shape (n=6), or the like. In this case, the shape of a horizontal section of an incidence surface is substantially similar to the shape (polygonal shape) of the surface to be irradiated. 
         [0098]    This application is entitled and claims the benefit of Japanese Patent Application No. 2011-138370 filed on Jun. 22, 2011 and Japanese Patent Application No. 2011-210277 filed on Sep. 27, 2011, the disclosure of which including the specification and drawings is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0099]    A light flux controlling member, a light emitting apparatus, and an illumination apparatus of the present invention can uniformly and effectively irradiate a polygonal-shaped surface to be irradiated with light that is emitted from a light emitting element. The light emitting apparatus and the illumination apparatus of the present invention are useful as, for example, lighting for cultivating plants, task lights (table and desk lighting), or reading lights. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10 ,  100 ,  500  Illumination lens 
           11 , 110  Incidence surface 
           111  Concave part 
           112  Flat surface 
           113  R surface 
           12 ,  120 ,  510  ( 510   a ,  510   b ) Emission surface 
           130  Flange 
           140  Foot 
           200  Light emitting element 
           300 ,  600  Light emitting apparatus 
           400  Illumination apparatus 
           410  Surface to be irradiated 
         CA Central axis