Abstract:
A beam-control member has a substantially cylindrical holder that is light-permeable, and a first beam-control member disposed on an end surface of the holder, the first beam-control member reflecting part of the light emitted from a light-emitting element and admitting part of the light. A guide protrusion and a tab are provided on the end surface of the holder. A concave portion corresponding to the tab is provided on an outer circumferential part of one surface of the first beam-control member. The first beam-control member is radially mated in a rotatable manner along the guide protrusion. Rotating the first beam-control member on the end surface of the holder so that the tab and the concave portion engage causes the first beam-control member to be secured on the end surface of the holder.

Description:
TECHNICAL FIELD 
     The present invention relates to a light flux controlling member that controls the light distribution of light emitted from a light emitting element, and an illumination apparatus that includes the light flux controlling member. 
     BACKGROUND ART 
     Recently, from the viewpoint of energy saving and environment protection, illumination apparatuses (for example, LED light bulbs) that use a light-emitting diode (hereinafter, also referred to as “LED”) as a light source are used as an alternative to incandescent light bulbs. 
     However, a conventional illumination apparatus that uses an LED as a light source emits light only in the forward direction, and cannot emit light in a wide direction like an incandescent light bulb. Therefore, unlike an incandescent light bulb, the conventional illumination apparatus cannot illuminate the inside of a room extensively using reflected light from a ceiling or wall surfaces. 
     In order to make the light distribution characteristics of such a conventional illumination apparatus that uses an LED as a light source close to the light distribution characteristics of an incandescent light bulb, technology has been proposed that controls the traveling direction of light emitted from the LED by the use of a light flux controlling member (for example, see PTL 1). 
       FIG. 1  is a cross-sectional view illustrating the configuration of illumination apparatus  10  described in PTL 1. As shown in  FIG. 1 , illumination apparatus  10  includes a plurality of LEDs  12  arranged on a substrate, and case  14  made of an optically transparent material and disposed so as to cover the LEDs  12 . Case  14  is constituted by case body  14   a  in a cylindrical shape and cover section  14   b  formed in an inverted circular truncated cone shape. Case body  14   a  and cover section  14   b  are integrally formed in a single unit. A transflective film (half-mirror coating)  16  is formed on the inner face of cover section  14   b . As indicated by arrows in  FIG. 1 , part of the light emitted from LEDs  12  passes through transflective film  16  and serves as light emitted in the forward direction (upward direction). Further, part of the light emitted from LEDs  12  is reflected by transflective film  16  and serves as light emitted in the lateral direction (horizontal direction) and in the backward direction (downward direction). 
     By controlling the traveling direction of light emitted from the LEDs using a light flux controlling member (case  14  in which semi-transflective film  16  is formed) having both optical transparency and optical reflectivity, in the manner described above, emitted light can be obtained not only in the forward direction, but also in the lateral direction and in the backward direction. Therefore, by using the light flux controlling member described in PTL 1, the light distribution characteristics of the illumination apparatus (LED light bulb) can be made close to the light distribution characteristics of an incandescent light bulb to a certain extent. 
     CITATION LIST 
     Patent Literature 
     PTL 1 
     Japanese Patent Application Laid-Open No. 2003-258319 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the light flux controlling member described in PTL 1, cover section  14   b  that has both optical transparency and optical reflectivity and case body  14   a  that has optical transparency require different optical properties from each other. Consequently, it is necessary to separately adjust the respective optical properties of cover section  14   b  and case body  14   a . However, since cover section  14   b  and case body  14   a  are integrated in the light flux controlling member described in PTL 1, separately adjusting the respective optical properties is a complicated process, and the manufacturing cost increases. 
     As one means for solving the above described problem, it is conceivable to separately manufacture cover section  14   b  (transflective member) that has both optical transparency and optical reflectivity and case body  14   a  (holder) that has optical transparency. In such a case, it is necessary to fix cover section  14   b  to one end of case body  14   a.    
     A method that fixes cover section  14   b  using an adhesive is conceivable as a method for fixing cover section  14   b  to one end of case body  14   a . However, according to this method, since a step of applying adhesive must be added to the manufacturing process, there is a problem of an increased cost of manufacturing the light flux controlling member. 
     Another conceivable method for fixing cover section  14   b  to one end of case body  14   a  is a method in which, as shown in  FIG. 2 , a plurality of hooks  18  for holding cover section  14   b  from the side are provided on case body  14   a . In this case, it is necessary to form notch portions  20  around each hook  18  to provide each hook  18  with elasticity. However, according to this method, since light leaks from notch portions  20 , a desired light distribution cannot be realized. 
     An object of the present invention is to provide a light flux controlling member that is constituted by a plurality of members and that is superior in terms of both optical properties and manufacturability. Another object of the present invention is to provide an illumination apparatus that includes the light flux controlling member. 
     Solution to Problem 
     To achieve at least one of the above mentioned objects, a light flux controlling member according to one aspect of the present invention controls a light distribution of light emitted from a light emitting element, the light flux controlling member including: a substantially cylindrically shaped holder having optical transparency, and a first light flux controlling member disposed on one end face of the holder, the first light flux controlling member reflecting part of the light emitted from the light emitting element and transmitting part of the light emitted from the light emitting element; wherein: the first light flux controlling member includes two principal surfaces that are in a front-and-rear relationship; a guide protrusion is provided at one part of an outer peripheral portion of the one end face of the holder; one or more hooks are provided on the one end face of the holder; a fitting portion that is located between the hook and the one end face of the holder when the first light flux controlling member is mounted on the one end face is provided at an outer peripheral portion of the first light flux controlling member; movement of the first light flux controlling member in a radial direction is restricted by allowing the first light flux controlling member to be radially fitted so as to be rotatable along the guide protrusion; and the first light flux controlling member is fixed on the one end face of the holder by rotating the first light flux controlling member on the one end face of the holder to engage the fitting portion between the hook and the one end face. 
     An illumination apparatus according to another aspect of the present invention includes: one or more light emitting elements; the light flux controlling member of the present invention; and a cover that transmits reflected light and transmitted light from the light flux controlling member while diffusing the reflected light and the transmitted light. 
     Advantageous Effects of Invention 
     According to the present invention a light flux controlling member can be provided that is constituted by a plurality of members and that is superior in terms of both optical properties and manufacturability. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view of an illumination apparatus described in PTL 1; 
         FIG. 2  is a perspective view illustrating an example of a method for fixing a transflective member; 
         FIG. 3  is a cross-sectional view of an illumination apparatus according to Embodiment 1; 
         FIG. 4  is a perspective view of the light flux controlling member according to Embodiment 1; 
         FIG. 5A  is a plan view of the light flux controlling member according to Embodiment 1,  FIG. 5B  is a front view of the light flux controlling member according to Embodiment 1,  FIG. 5C  is a bottom view of the light flux controlling member according to Embodiment 1, and  FIG. 5D  is a cross-sectional view taken along line A-A shown in  FIG. 5A ; 
         FIG. 6  is an exploded perspective view of the light flux controlling member according to Embodiment 1; 
         FIG. 7A  is a plan view of a second light flux controlling member and a holder,  FIG. 7B  is a front view of the second light flux controlling member and the holder,  FIG. 7C  is a bottom view of the second light flux controlling member and the holder, and  FIG. 7D  is a cross-sectional view taken along line B-B shown in  FIG. 7A ; 
         FIG. 8A  is a plan view of a first light flux controlling member,  FIG. 8B  is a front view of the first light flux controlling member,  FIG. 8C  is a bottom view of the first light flux controlling member,  FIG. 8D  is a cross-sectional view taken along line C-C shown in  FIG. 8A , and  FIG. 8E  is a right side view of the first light flux controlling member; 
         FIG. 9  is a perspective view of a second light flux controlling member and a holder included in a light flux controlling member according to Embodiment 2; 
         FIG. 10A  is a plan view of the second light flux controlling member and the holder,  FIG. 10B  is a front view of the second light flux controlling member and the holder,  FIG. 10C  is a bottom view of the second light flux controlling member and the holder, and  FIG. 10D  is a cross-sectional view taken along line D-D shown in  FIG. 10A ; 
         FIG. 11  is a perspective view of a second light flux controlling member and a holder included in a light flux controlling member according to Embodiment 3; 
         FIG. 12A  is a plan view of the second light flux controlling member and the holder,  FIG. 12B  is a front view of the second light flux controlling member and the holder,  FIG. 12C  is a bottom view of the second light flux controlling member and the holder, and  FIG. 12D  is a cross-sectional view taken along line E-E shown in  FIG. 12A ; 
         FIG. 13A  is a plan view of a second light flux controlling member and a holder included in a light flux controlling member according to Embodiment 4, and  FIG. 13B  is a perspective view of the second light flux controlling member and the holder included in the light flux controlling member according to Embodiment 4; 
         FIG. 14  is a perspective view of a holder included in a light flux controlling member according to Embodiment 5; 
         FIG. 15A  is a plan view of the holder,  FIG. 15B  is a front view of the holder,  FIG. 15C  is a bottom view of the holder, and  FIG. 15D  is a cross-sectional view taken along line F-F shown in  FIG. 15A ; 
         FIG. 16  is a perspective view of a holder included in a light flux controlling member according to Embodiment 6; 
         FIG. 17A  is a plan view of the holder,  FIG. 17B  is a front view of the holder,  FIG. 17C  is a bottom view of the holder, and  FIG. 17D  is a cross-sectional view taken along line G-G shown in  FIG. 17A ; and 
         FIGS. 18A and 18B  are perspective views illustrating a state in which the holder is fixed on a substrate. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings. 
     Embodiment 1 
     [Configuration of Illumination Apparatus] 
       FIG. 3  is a cross-sectional view of illumination apparatus  100  according to Embodiment 1 of the present invention. The illumination apparatus according to the present embodiment can be used as an alternative to an incandescent light bulb. 
     As shown in  FIG. 3 , illumination apparatus  100  includes base  110 , substrate  120 , one or more light emitting elements  130 , light flux controlling member  170  and cover  180 . Each of these components is described hereunder. 
     (1) Base, Substrate and Light Emitting Element 
     Light emitting element  130  is a light source of illumination apparatus  100 , and is mounted on substrate  120  fixed on base  110 . Light emitting element  130  is, for example, a light-emitting diode (LED) such as a white light-emitting diode. In a case where a plurality of light emitting elements  130  are mounted on substrate  120 , the respective light emitting elements  130  may be disposed in a circle. The shape of substrate  120  is not particularly limited as long as light emitting element  130  can be mounted thereon, and the shape need not be a tabular shape. The shape of base  110  is not particularly limited as long as at least substrate  120  can be fixed thereon, and the shape need not be a tabular shape. 
     (2) Light Flux Controlling Member 
     Light flux controlling member  170  controls the light distribution of light emitted from light emitting element  130 .  FIG. 4  and  FIGS. 5A to 5D  illustrate the configuration of light flux controlling member  170 .  FIG. 4  is a perspective view,  FIG. 5A  is a plan view,  FIG. 5B  is a front view,  FIG. 5C  is a bottom view, and  FIG. 5D  is a cross-sectional view taken along line A-A shown in  FIG. 5A . Further,  FIG. 6  is an exploded perspective view of light flux controlling member  170 . As shown in these drawings, light flux controlling member  170  includes first light flux controlling member  140  (transflective member), second light flux controlling member  150  (light condensing member), and holder  160  (supporting member and diffused transmission member). Second light flux controlling member  150  and holder  160  are integrated. 
     The respective components of light flux controlling member  170  are described hereunder in the order of holder  160 , second light flux controlling member  150  and first light flux controlling member  140 . 
     (2-1) Holder 
       FIGS. 7A to 7D  illustrate the configuration of second light flux controlling member  150  and holder  160 .  FIG. 7A  is a plan view,  FIG. 7B  is a front view,  FIG. 7C  is a bottom view, and  FIG. 7D  is a cross-sectional view taken along line B-B shown in  FIG. 7A . As described above, second light flux controlling member  150  and holder  160  are integrated. 
     Holder  160  is positioned by base  110 , and positions first light flux controlling member  140  and second light flux controlling member  150  with respect to light emitting element  130 . As shown in  FIG. 3 , optical axis LA of light emitting element  130 , central axis CA 1  of first light flux controlling member  140 , and central axis CA 2  of second light flux controlling member  150  coincide with each other. 
     Holder  160  is an optically transparent member formed in a substantially cylindrical shape. First light flux controlling member  140  is fixed at one end of holder  160 . The other end of holder  160  is fixed to base  110 . In the following description, of the two ends of holder  160 , the end at which first light flux controlling member  140  is fixed is referred to as “upper end” and the end that is fixed to base  110  is referred to as “lower end”. 
     Holder  160  is formed together with second light flux controlling member  150  by integral molding. The material of holder  160  is not particularly limited as long as the material can transmit light of a desired wavelength. Examples of the material of holder  160  include optically transparent resins such as polymethylmethacrylate (PMMA), polycarbonate (PC), and epoxy resin (EP), or glass. In the case of providing holder  160  with a light diffusing capability, scatterers may be included in these optically transparent materials, or a light diffusion process may be performed on the surface of holder  160 . 
     As shown in  FIG. 6 , guide protrusion  162  and hook  163  are provided at the upper end of holder  160  to fix first light flux controlling member  140  on end face  161  of the upper end. 
     Guide protrusion  162  is formed at a part of an outer peripheral portion of end face  161  of the upper end, and prevents first light flux controlling member  140  moving in the radial direction of holder  160 . The number of guide protrusions  162  is not particularly limited, and is normally two or more. In the example illustrated in  FIG. 6 , holder  160  has two guide protrusions  162  that face each other. The shape of guide protrusion  162  is not particularly limited as long as guide protrusion  162  can radially fit together with first light flux controlling member  140 . In the example illustrated in  FIG. 6 , guide protrusion  162  has a circular arc shape in a plan view. 
     Hook  163  is formed on end face  161  of the upper end. As described later, together with fitting portion  143  (recess  144 ) of first light flux controlling member  140 , hook  163  prevents detachment and rotation of first light flux controlling member  140 . The number of hooks  163  is not particularly limited, and is normally two or more. In the example illustrated in  FIG. 6 , holder  160  has two hooks  163  that face each other. The shape of hook  163  is not particularly limited as long as hook  163  can be engaged with recess  144  of first light flux controlling member  140  when first light flux controlling member  140  is rotated. 
     End face  161  for mounting first light flux controlling member  140  is formed over the entire circumference of the upper end of holder  160 . That is, end face  161  is also present at the inner side of guide protrusion  162  and the inner side of hook  163  (see  FIG. 7A ). Accordingly, when light flux controlling member  170  is seen in a plan view, an outer peripheral portion (flange  142 ) of first light flux controlling member  140  overlaps with end face  161  of the upper end over the entire circumference thereof. Consequently, leakage of light from a gap between first light flux controlling member  140  and holder  160  is prevented. 
     Stepped portion  165  for positioning holder  160  on base  110  is provided at the lower end of holder  160 . Further, ventilation opening  166  for ventilating the air around second light flux controlling member  150  is also provided at the lower end of holder  160 . 
     (2-2) Second Light Flux Controlling Member 
     Second light flux controlling member  150  controls the traveling direction of part of light emitted from light emitting element  130 , and functions so that the light distribution of light emitted from second light flux controlling member  150  is narrower than the light distribution of light emitted from light emitting element  130 . As shown in  FIG. 7A , second light flux controlling member  150  is a member formed in a substantially circular shape in a plan view. Second light flux controlling member  150  is supported by holder  160 , and is disposed with respect to light emitting element  130  with an air layer interposed therebetween so that central axis CA 2  thereof coincides with optical axis LA (see  FIG. 3 ). In a case where a plurality of light emitting elements  130  are disposed on substrate  120 , the term “optical axis LA of light emitting element  130 ” refers to the traveling direction of light at the center of three-dimensional light fluxes from the plurality of light emitting elements  130 . 
     As shown in  FIGS. 7A to 7D , second light flux controlling member  150  includes incidence surface  151  on which light emitted from light emitting element  130  is incident, total reflection surface  152  that totally reflects part of the light that is incident from incidence surface  151 , and emission surface  153  that emits part of the light that is incident from incidence surface  151  and light that is reflected by total reflection surface  152 . 
     As described above, second light flux controlling member  150  is formed together with holder  160  by integral molding. The material of second light flux controlling member  150  is not particularly limited as long as the material is a highly transparent material that can transmit light of a desired wavelength. Examples of the material of second light flux controlling member  150  include optically transparent resins such as polymethylmethacrylate (PMMA), polycarbonate (PC), and epoxy resin (EP), or glass. 
     Incidence surface  151  causes the light emitted from light emitting element  130  to be incident on the inside of second light flux controlling member  150 . Incidence surface  151  is the inner face of a recess formed in the bottom of second light flux controlling member  150 . Incidence surface  151  is formed at a position opposing light emitting element  130  so as to intersect with central axis CA 2  of second light flux controlling member  150 . Incidence surface  151  is a rotationally symmetric plane about central axis CA 2  of second light flux controlling member  150 . Incidence surface  151  includes an inner top face that constitutes the top face of the recess, and a tapered inner side face that constitutes the side face of the recess. The inner diameter of the inner side face gradually increases from the inner top face side toward the opening edge side so that the dimensions of the inner diameter on the opening edge side are larger than the dimensions of the inner diameter of the edge on the inner top face side (see  FIG. 7D ). 
     Total reflection surface  152  totally reflects part of the light that was incident on incidence surface  151  toward first light flux controlling member  140 . Total reflection surface  152  is a surface extending from the outer edge of the bottom of second light flux controlling member  150  to the outer edge of emission surface  153 . A flange may be provided between the outer edge of total reflection surface  152  and the outer edge of emission surface  153  (see  FIG. 7D ). Total reflection surface  152  is a rotationally symmetric plane that is formed so as to surround central axis CA 2  of second light flux controlling member  150 . The diameter of total reflection surface  152  gradually increases from the bottom side toward the side of emission surface  153 . A generating line constituting total reflection surface  152  is an arc-shaped curve that is convex to the outside (the side away from central axis CA 2 ). The generating line constituting total reflection surface  152  may be set to a straight line depending on the light distribution characteristics required for illumination apparatus  100 , and total reflection surface  152  may have a tapered shape. Note that the term “generating line” generally means a straight line that is used to draw a ruled surface, and in the present invention the term “generating line” is used as a term that includes a curve for drawing total reflection surface  152  that is a rotationally symmetric plane. 
     Emission surface  153  emits part of the light that was incident on incidence surface  151  and light that was totally reflected by total reflection surface  152  toward first light flux controlling member  140 . Emission surface  153  is a surface located on the opposite side of incidence surface  151  (bottom) in second light flux controlling member  150 , and is formed so as to intersect with optical axis LA of light emitting element  130 . That is, emission surface  153  is formed so as to oppose first light flux controlling member  140  (see  FIG. 5D ). 
     (2-3) First Light Flux Controlling Member 
       FIGS. 8A to 8E  illustrate the configuration of first light flux controlling member  140 .  FIG. 8A  is a plan view,  FIG. 8B  is a front view,  FIG. 8C  is a bottom view,  FIG. 8D  is a cross-sectional view taken along line C-C shown in  FIG. 8A , and  FIG. 8E  is a right side view. 
     First light flux controlling member  140  reflects part of the light emitted from second light flux controlling member  150  (light emitted from light emitting element  130 ) while controlling the traveling direction thereof, and transmits the remaining part. First light flux controlling member  140  is a member formed in a substantially circular shape in a plan view, and has two principal surfaces that are in a front-and-rear relationship. First light flux controlling member  140  is supported by holder  160 , and is disposed with respect to second light flux controlling member  150  with an air layer interposed therebetween so that central axis CA 1  thereof coincide with optical axis LA of light emitting element  130 . That is, first light flux controlling member  140  is disposed on an opposite side to light emitting element  130  with respect to second light flux controlling member  150 , so as to oppose emission surface  153  of second light flux controlling member  150 . 
     First light flux controlling member  140  reflects part of the light emitted from second light flux controlling member  150  and transmits another part thereof. Means for providing first light flux controlling member  140  with such a function is not particularly limited. For example, a transflective film may be formed on the surface (surface opposing light emitting element  130 ) of first light flux controlling member  140  that is formed of an optically transparent material. Examples of the optically transparent material include transparent resin materials such as polymethylmethacrylate (PMMA), polycarbonate (PC) and epoxy resin (EP), and transparent glass. Examples of the transflective film include dielectric multilayer films such as a multilayer film composed of TiO 2  and SiO 2 , a multilayer film composed of ZrO 2  and SiO 2 , and a multilayer film composed of Ta 2 O 5  and SiO 2 , or a metallic thin film formed of aluminum (Al) or the like. Light scatterers such as beads may be dispersed in first light flux controlling member  140  that is formed of an optically transparent material. That is, first light flux controlling member  140  may be formed of a material that reflects some light and transmits some light. Further, a light-transmitting portion may be formed in first light flux controlling member  140  that is formed of an optically reflective material. Examples of the optically reflective material include white resins and metals. Examples of the light-transmitting portion include a through-hole and a bottomed recess. In the latter case, light emitted from second light flux controlling member  150  passes through the bottom (portion having a thin thickness) of the recess. For example, first light flux controlling member  140  having both functions of optical reflectivity and optical transparency can be formed using white polymethyl methacrylate with visible ray transmittance of about 20% and reflectance of about 78%. 
     First light flux controlling member  140  includes reflection surface  141  that opposes second light flux controlling member  150  and that reflects part of the light emitted from second light flux controlling member  150 . Reflection surface  141  reflects part of the light emitted from second light flux controlling member  150  toward holder  160 . The reflected light passes through holder  160  and reaches the middle portion (side portion) and the lower portion of cover  180 . 
     Reflection surface  141  of first light flux controlling member  140  is a rotationally symmetric (circularly symmetric) plane about central axis CA 1  of first light flux controlling member  140 . As shown in  FIG. 5D , the generating line extending from the center of the rotationally symmetric plane to the outer peripheral portion is a curve that is concave with respect to light emitting element  130  (second light flux controlling member  150 ), and reflection surface  141  is a curved surface formed by rotating the generating line 360°. That is, reflection surface  141  has an aspheric curved surface in which the height from light emitting element  130  increases from the center toward the outer peripheral portion. The outer peripheral portion of reflection surface  141  is formed at a position at which the distance (height) from light emitting element  130  in the direction of optical axis LA of light emitting element  130  is greater than at the center of reflection surface  141 . For example, reflection surface  141  is an aspheric curved surface in which the height from light emitting element  130  increases from the center toward the outer peripheral portion, or an aspheric curved surface in which, from a central portion until a predetermined location, the height from light emitting element  130  (substrate  120 ) increases from the central portion toward the outer peripheral portion, and from the predetermined location until the outer peripheral portion, the height from light emitting element  130  decreases from the central portion toward the outer peripheral portion. In the former case, an inclining angle of reflection surface  141  with respect to the plane direction of substrate  120  decreases from the center toward the outer peripheral portion. On the other hand, in the latter case, in reflection surface  141 , a point at which the inclining angle with respect to the plane direction of substrate  120  is zero (parallel to substrate  120 ) exists at a position which is between the center and the outer peripheral portion and is close to the outer peripheral portion. As described above, the term “generating line” generally means a straight line that is used to draw a ruled surface, and in the present invention the term “generating line” is used as a term that includes a curve for drawing reflection surface  141  that is a rotationally symmetric plane. 
     As shown in  FIGS. 8A to 8D , flange  142  that can be mounted on the end face  161  of holder  160  is provided at the outer peripheral portion of first light flux controlling member  140 . The width of flange  142  differs depending on the location so that first light flux controlling member  140  can rotate at a predetermined angle in a state in which first light flux controlling member  140  and guide protrusion  162  of holder  160  are fitted together radially (see  FIG. 8A ). 
     Fitting portion  143  that is positioned between hook  163  and end face  161  of holder  160  when first light flux controlling member  140  is mounted on end face  161  of holder  160  is also provided in outer peripheral portion of first light flux controlling member  140 . Recess  144  that corresponds to hook  163  of holder  160  is provided in one face (face on the side of cover  180 ) of fitting portion  143 . Together with hook  163  of holder  160 , fitting portion  143  (recess  144 ) prevents first light flux controlling member  140  from rotating. The number of fitting portions  143  (recesses  144 ) is normally the same as the number of hooks  163 . In the example illustrated in  FIG. 6 , first light flux controlling member  140  has two fitting portions  143  (recess  144 ). The shape of fitting portion  143  is not particularly limited as long as recess  144  can be engaged with hook  163  of holder  160  when first light flux controlling member  140  is rotated. 
     As will be described later, first light flux controlling member  140  is fixed on end face  161  of holder  160  by being rotated on end face  161  of holder  160  to cause hooks  163  to engage with recesses  144  (see  FIG. 6 ). 
     (3) Cover 
     Cover  180  is positioned by base  110 , and diffuses and transmits light (reflected light and transmitted light) whose traveling direction is controlled by light flux controlling member  170 . Cover  180  is a member in which a hollow region having an opening is funned. Substrate  120 , light emitting element  130 , and light flux controlling member  170  are disposed in the hollow region of cover  180 . 
     Means for providing cover  180  with a light diffusing capability is not particularly limited. For example, a light diffusion process (for example, a roughening process) may be performed on the inner face or the outer face of cover  180 , or cover  180  may be manufactured using a light-diffusing material (for example, an optically transparent material including scatterers such as beads). The shape of cover  180  is not particularly limited as long as desired light distribution characteristics can be realized. For example, cover  180  may have a spherical crown shape (a shape obtained by horizontally cutting part of a spherical surface). 
     Next, the optical path of light emitted from light emitting element  130  in illumination apparatus  100  of the present embodiment will be described. 
     Light that is emitted from light emitting element  130  at large angles with respect to optical axis LA of light emitting element  130  is incident on second light flux controlling member  150  from incidence surface  151  (inner side face). Part of the light incident on second light flux controlling member  150  is reflected toward first light flux controlling member  140  by total reflection surface  152 , and is emitted from emission surface  153 . Part of the light emitted from emission surface  153  of second light flux controlling member  150  passes through first light flux controlling member  140  and reaches the upper portion of cover  180 . Further, part of the light emitted from emission surface  153  of second light flux controlling member  150  is reflected by first light flux controlling member  140 , and passes through holder  160  and reaches the middle portion and lower portion of cover  180 . 
     On the other hand, light that is emitted from light emitting element  130  at small angles with respect to optical axis LA of light emitting element  130  is incident on second light flux controlling member  150  from incidence surface  151  (inner top face), and is emitted toward first light flux controlling member  140  from emission surface  153  directly. Part of the light emitted from emission surface  153  of second light flux controlling member  150  passes through first light flux controlling member  140  and reaches the upper portion of cover  180 . Further, part of the light emitted from emission surface  153  of second light flux controlling member  150  is reflected by first light flux controlling member  140 , and passes through holder  160  and reaches the middle portion and lower portion of cover  180 . 
     Thus, in illumination apparatus  100  of the present embodiment, a large part of the light that reaches first light flux controlling member  140  is light that is incident inside second light flux controlling member  150  and is emitted from second light flux controlling member  150 . 
     According to illumination apparatus  100  of the present embodiment, of the light that is emitted from light emitting element  130 , at least light that is emitted within an angular range from a direction in which light of a maximum intensity is emitted (for example, direction of optical axis LA) to a direction in which light having an intensity that is half of the maximum intensity is emitted (hereunder, referred to as “light within a half-intensity-angular-range”) passes through at least one of holder  160  and first light flux controlling member  140 , and is emitted from an inner region surrounded by holder  160  and first light flux controlling member  140  to an outer region. In other words, light flux controlling member  170  according to the present embodiment is formed so that light within a half-intensity-angular-range passes through at least any one of holder  160  and first light flux controlling member  140 . 
     As shown in  FIG. 2 , in a case where notch portions  20  are formed at the upper end of the holder (case body  14   a ), comparatively strong light leaks out from notch portions  20 . Therefore, a bright part is liable to arise on a surface to be irradiated or a cover (cover that covers the light flux controlling member). In particular, when light within a half-intensity-angular-range leaks out from notch portions  20 , there is a risk that a bright part will become pronounced depending on the position on the surface to be irradiated or the cover. In contrast, if the light is light emitted at a large angle with respect to the optical axis of the light emitting element (light at an angle equal to or greater than a half-intensity angle, and that is emitted towards the direction of ventilation opening  166 ), even if the light is emitted directly to outside without passing through holder  160  or first light flux controlling member  140  and irradiates a surface to be irradiated or a cover, a specific bright part cannot easily occur. 
     [Method of Manufacturing Light Flux Controlling Member] 
     Light flux controlling member  170  according to the present embodiment can be manufactured by the following procedure, for example. 
     First, first light flux controlling member  140  including reflection surface  141  is formed by injection molding. The method of manufacturing first light flux controlling member  140  is not particularly limited. For example, first light flux controlling member  140  can be manufactured by injection molding using a colorless and transparent resin material, and thereafter depositing a transflective film on a face (face opposing second light flux controlling member  150 ) that is to serve as reflection surface  141  of the resultant resin molded product. First light flux controlling member  140  can also be manufactured by injection molding using a white resin material. 
     Further, second light flux controlling member  150  and holder  160  are integrally formed in a single unit by injection molding using a colorless and transparent resin material. 
     Subsequently, as shown in  FIG. 6 , flange  142  of first light flux controlling member  140  is mounted on end face  161  of the upper end of holder  160 , and first light flux controlling member  140  and guide protrusions  162  of holder  160  are fitted together radially. In this state, when first light flux controlling member  140  is rotated in a predetermined direction, fitting portions  143  of first light flux controlling member  140  engage between hooks  163  and end face  161  of holder  160 . That is, hooks  163  of holder  160  engage with recesses  144  of first light flux controlling member  140 . 
     By performing the above described procedure, light flux controlling member  170  according to the present embodiment that includes first light flux controlling member  140 , second light flux controlling member  150  and holder  160  can be manufactured without using adhesive and without providing notch portions in holder  160 . 
     [Advantageous Effects] 
     Light flux controlling member  170  according to Embodiment 1 can control the traveling direction of light emitted from light emitting element  130  by using first light flux controlling member  140  and second light flux controlling member  150 , and thereby distribute the emitted light to the forward direction, the lateral direction and the backward direction. Therefore, illumination apparatus  100  that includes light flux controlling member  170  according to Embodiment 1 can control the amounts of light emitted in the forward direction, the lateral direction and the backward direction, and realize light distribution characteristics that are close to those of an incandescent light bulb. 
     Further, light flux controlling member  170  according to Embodiment 1 reflects part of the light in the lateral direction (direction toward the middle portion of cover  180 ) and the backward direction (direction toward the lower portion of cover  180 ) by means of reflection surface  141 , and transmits part of the light in the forward direction (direction toward the upper portion of cover  180 ). At this time, light flux controlling member  170  generates reflected light mainly in the lateral direction in a region on the central portion side of reflection surface  141 , and generates reflected light mainly in the backward direction in a region on the outer peripheral portion side of reflection surface  141 . Therefore, illumination apparatus  100  according to Embodiment 1 can efficiently illuminate a surface to be irradiated in the backward direction without being obstructed by base  110 . 
     When manufacturing light flux controlling member  170  according to Embodiment 1, first light flux controlling member  140  that has both optical transparency and optical reflectivity and holder  160  that has optical transparency are manufactured separately. It is therefore possible to easily adjust the optical properties of first light flux controlling member  140  irrespective of holder  160 . Likewise, the optical properties of holder  160  can also be easily adjusted irrespective of first light flux controlling member  140 . 
     Further, when manufacturing light flux controlling member  170  according to Embodiment 1, first light flux controlling member  140  can be fixed on holder  160  without gaps and without using an adhesive by merely mounting first light flux controlling member  140  on end face  161  of holder  160  and rotating first light flux controlling member  140 . It is therefore possible to manufacture light flux controlling member  170  according to Embodiment 1 without reducing the optical properties thereof and without increasing the manufacturing cost. 
     Embodiment 2 
     An illumination apparatus and a light flux controlling member according to Embodiment 2 differ from illumination apparatus  100  and light flux controlling member  170  according to Embodiment 1 only in the shape of the holder. Therefore, components that are the same as in illumination apparatus  100  and light flux controlling member  170  according to Embodiment 1 are denoted by the same reference numerals, and a description thereof is omitted hereunder. 
       FIG. 9  and  FIGS. 10A to 10D  illustrate the configuration of second light flux controlling member  150  and holder  260  that are included in the light flux controlling member according to Embodiment 2.  FIG. 9  is a perspective view,  FIG. 10A  is a plan view,  FIG. 10B  is a front view,  FIG. 10C  is a bottom view, and  FIG. 10D  is a cross-sectional view taken along line D-D shown in  FIG. 10A . As shown in these drawings, second light flux controlling member  150  and holder  260  are integrated. 
     Holder  260  included in the light flux controlling member according to Embodiment 2 has fundamentally the same structure as holder  160  included in light flux controlling member  170  according to Embodiment 1. However, holder  260  differs from holder  160  in the respect that the wall thickness thereof is thinned within a range that can secure the light intensity and prevent the occurrence of light leakage. As shown in  FIG. 10A  and  FIG. 10D , the wall thickness of holder  260  differs depending on the location. 
     [Advantageous Effects] 
     The light flux controlling member according to Embodiment 2 has the same advantageous effects as light flux controlling member  170  according to Embodiment 1, while also being lighter than light flux controlling member  170  according to Embodiment 1. 
     Embodiment 3 
     An illumination apparatus and a light flux controlling member according to Embodiment 3 differ from illumination apparatus  100  and light flux controlling member  170  according to Embodiment 1 only in the shape of the holder. Therefore, components that are the same as in illumination apparatus  100  and light flux controlling member  170  according to Embodiment 1 are denoted by the same reference numerals, and a description thereof is omitted hereunder. 
       FIG. 11  and  FIGS. 12A to 12D  illustrate the configuration of second light flux controlling member  150  and holder  360  that are included in the light flux controlling member according to Embodiment 3.  FIG. 11  is a perspective view,  FIG. 12A  is a plan view,  FIG. 12B  is a front view,  FIG. 12C  is a bottom view, and  FIG. 12D  is a cross-sectional view taken along line E-E shown in  FIG. 12A . As shown in these drawings, second light flux controlling member  150  and holder  360  are integrated. 
     Holder  360  included in the light flux controlling member according to Embodiment 3 has fundamentally the same structure as holder  160  included in light flux controlling member  170  according to Embodiment 1. However, holder  360  differs from holder  160  in the respect that the wall thickness thereof is thinned within a range that can secure the light intensity and prevent the occurrence of light leakage. As shown in  FIG. 12A  and  FIG. 12D , the wall thickness of holder  360  differs depending on the location. 
     [Advantageous Effects] 
     The light flux controlling member according to Embodiment 3 has the same advantageous effects as light flux controlling member  170  according to Embodiment 1, while also being lighter than light flux controlling member  170  according to Embodiment 1. 
     Embodiment 4 
     An illumination apparatus and a light flux controlling member according to Embodiment 4 differ from illumination apparatus  100  and light flux controlling member  170  according to Embodiment 1 only in the shape of the holder. Therefore, components that are the same as in illumination apparatus  100  and light flux controlling member  170  according to Embodiment 1 are denoted by the same reference numerals, and a description thereof is omitted hereunder. 
       FIGS. 13A and 13B  illustrate the configuration of second light flux controlling member  150  and holder  460  included in the light flux controlling member according to Embodiment 4.  FIG. 13A  is a plan view and  FIG. 13B  is a perspective view. As shown in these drawings, second light flux controlling member  150  and holder  460  are integrated. 
     Holder  460  included in the light flux controlling member according to Embodiment 4 has fundamentally the same structure as holder  160  included in light flux controlling member  170  according to Embodiment 1. However, holder  460  differs from holder  160  in the respect that ventilation groove  461  is formed in end face  161  of the upper end thereof and in the inner face of guide protrusion  162 . Ventilation groove  461  serves as a ventilation channel for ventilating the air in the space between first light flux controlling member  140  and second light flux controlling member  150  when the opening of holder  460  is blocked by first light flux controlling member  140 . As shown in  FIG. 13A  and  FIG. 13B , to prevent the occurrence of light leakage, ventilation groove  461  bends in a crank shape. 
     [Advantageous Effects] 
     In addition to having the same advantageous effects as light flux controlling member  170  according to Embodiment 1, the light flux controlling member according to Embodiment 4 also has the advantageous effect that an increase in the temperature in the space between first light flux controlling member  140  and second light flux controlling member  150  can be suppressed. 
     Embodiment 5 
     An illumination apparatus and a light flux controlling member according to Embodiment 5 differ from illumination apparatus  100  and light flux controlling member  170  according to Embodiment 1 in that a second light flux controlling member is not included. Therefore, components that are the same as in illumination apparatus  100  and light flux controlling member  170  according to Embodiment 1 are denoted by the same reference numerals, and a description thereof is omitted hereunder. 
       FIG. 14  and  FIGS. 15A to 15D  illustrate the configuration of holder  560  included in the light flux controlling member according to Embodiment 5.  FIG. 14  is a perspective view,  FIG. 15A  is a plan view,  FIG. 15B  is a front view,  FIG. 15C  is a bottom view, and  FIG. 15D  is a cross-sectional view taken along line F-F shown in  FIG. 15A . 
     Holder  560  included in the light flux controlling member according to Embodiment 5 has fundamentally the same structure as holder  160  included in light flux controlling member  170  according to Embodiment 1. However, as shown in  FIG. 14  and  FIGS. 15A to 15D , holder  560  is not integrated with the second light flux controlling member. Further, a stepped portion or the like for fixing the second light flux controlling member is not provided in holder  560 . 
     [Advantageous Effects] 
     The light flux controlling member according to Embodiment 5 has the same advantageous effects as light flux controlling member  170  according to Embodiment 1. In a case where it is necessary to adjust the distribution of light in the forward direction, the lateral direction, and the backward direction, it is possible to obtain the intended light distribution by adjusting the balance between the transmission performance and reflection performance or the shape of the reflection surface of first light flux controlling member  140 . 
     Embodiment 6 
     An illumination apparatus and a light flux controlling member according to Embodiment 6 differ from illumination apparatus  100  and light flux controlling member  170  according to Embodiment 1 in the shape of the second light flux controlling member and the holder. Therefore, components that are the same as in illumination apparatus  100  and light flux controlling member  170  according to Embodiment 1 are denoted by the same reference numerals, and a description thereof is omitted hereunder. 
       FIG. 16  and  FIGS. 17A to 17D  illustrate the configuration of second light flux controlling member  650  and holder  660  that are included in the light flux controlling member according to Embodiment 6.  FIG. 16  is a perspective view,  FIG. 17A  is a plan view,  FIG. 17B  is a front view,  FIG. 17C  is a bottom view, and  FIG. 17D  is a cross-sectional view taken along line G-G shown in  FIG. 17A . As shown in these drawings, second light flux controlling member  650  and holder  660  are integrated. 
     As shown in  FIG. 17D , second light flux controlling member  650  included in the light flux controlling member according to Embodiment 6 has incidence region  651  on which light emitted from light emitting element  130  is incident, and emission region  654  that is located on the opposite side to incidence region  651  and that emits light that is incident from incidence region  651 . Incidence region  651  includes refraction portion  652  that is located at a central portion of incidence region  651 , and Fresnel lens portion  653  that is located on the outer side of refraction portion  652 . 
     Refraction portion  652  is formed so as to intersect with central axis CA 2  of second light flux controlling member  650  at a position facing light emitting element  130 . Refraction portion  652  is, for example, a flat, spherical, aspheric, or refractive Fresnel lens. Refraction portion  652  has a function that causes part of the light emitted from light emitting element  130  (mainly light emitted in the forward direction) to be incident inside second light flux controlling member  650 , and also refracts the incident light toward emission region  654 . The shape of refraction portion  652  in the present embodiment is rotationally symmetrical about central axis CA 2  of second light flux controlling member  650 . 
     Fresnel lens portion  653  causes part of the light emitted from light emitting element  130  (mainly light emitted in the lateral direction) to be incident inside second light flux controlling member  650 , and also totally reflects the incident light toward emission region  654 . The shape of Fresnel lens portion  653  is rotationally symmetrical about central axis CA 2  of second light flux controlling member  650 , and Fresnel lens portion  653  has a plurality of toric protrusions that are arranged in a concentric shape (see  FIG. 17C ). As shown in  FIG. 17D , among the plurality of toric protrusions, a protrusion located on the outermost side is formed to be larger than the other protrusions. 
     Each of the plurality of protrusions has a first inclining surface that is an incidence surface on which light emitted from light emitting element  130  is incident, and a second inclining surface that is a reflection surface that reflects light that is incident from the first inclining surface toward emission region  654 . In each protrusion, the first inclining surface is located on the inner side (central axis CA 2  side) and the second inclining surface is located on the outer side. 
     A generating line of the first inclining surface may be a straight line or may be a curve. An angle of the first inclining surface with respect to optical axis LA of light emitting element  130  is not particularly limited as long as light that is incident from the first inclining surface can be refracted to the side of the second inclining surface, and the angle can be appropriately set in accordance with the size and location of light emitting element  130 . The angles of the first inclining surfaces of the respective protrusions may be identical or may be different. Likewise, a generating line of the second inclining surface may be a straight line or may be a curve. An angle of the second inclining surface with respect to optical axis LA of light emitting element  130  is not particularly limited as long as light that is incident from the first inclining surface can be reflected to the side of emission region  654 , and the angle can be appropriately set in accordance with the intended light distribution characteristics and the like. The angles of the second inclining surfaces of the respective protrusions may be identical or may be different. 
     Emission region  654  is a flat surface that is formed on the first light flux controlling member  140  side that is on the opposite side to light emitting element  130 . Emission region  654  is formed so as to intersect with central axis CA 2  of second light flux controlling member  650 . As shown in  FIG. 17A , emission region  654  is a rotationally symmetric plane about central axis CA 2  of second light flux controlling member  650 . Emission region  654  causes light that is incident from refraction portion  652 , and light that is incident from first inclining surface of Fresnel lens portion  653  and reflected by second inclining surface to be emitted toward first light flux controlling member  140 . 
     Holder  660  included in the light flux controlling member according to Embodiment 6 has fundamentally the same structure as holder  160  included in light flux controlling member  170  according to Embodiment 1. However, holder  660  differs from holder  160  in the respect that the wall thickness thereof is thinned within a range that can secure the light intensity and prevent the occurrence of light leakage. As shown in  FIG. 17D , the wall thickness of holder  660  differs depending on the location (the same as holder  360  according to Embodiment 3). Further, positioning bosses  661  and positioning hooks  662  for positioning holder  660  on substrate  120  are provided at the lower end of holder  660 . 
       FIGS. 18A and 18B  illustrate a state in which holder  660  is fixed on substrate  120 .  FIG. 18A  is a perspective view as seen from the side of holder  660 .  FIG. 18B  is a perspective view as seen from the side of substrate  120 . As shown in these drawings, four through-holes are provided in substrate  120 . Holder  660  is fixed on substrate  120  by inserting positioning bosses  661  and positioning hooks  662  of holder  660  in the four through-holes, respectively. At such time, adhesive may be used or need not be used. 
     Positioning bosses  661  are fitted into the corresponding through-holes in a state in which almost no gap exists between each positioning boss  661  and the corresponding through-hole. On the other hand, positioning hooks  662  are fitted into the corresponding through-holes so that the tips thereof engage with the rear surface of substrate  120 . Positioning bosses  661  can prevent movement in a direction parallel to the substrate surface. Positioning hooks  662  can prevent movement in a direction perpendicular to the substrate surface. 
     [Advantageous Effects] 
     The light flux controlling member according to Embodiment 6 has the same advantageous effects as light flux controlling member  170  according to Embodiment 1, while also being lighter than light flux controlling member  170  according to Embodiment 1. Further, the light flux controlling member according to Embodiment 6 can be easily fixed on substrate  120 . 
     Modified Example 
     Although an example in which the second light flux controlling member and the holder are integrated was described in Embodiments 1 to 4 and Embodiment 6, a configuration may also be adopted in which the second light flux controlling member and the holder are separate members. In such case, it is necessary to fix the second light flux controlling member to the holder before fixing the first light flux controlling member to the holder. A method for fixing the second light flux controlling member to the holder is not particularly limited. For example, a stepped portion may be formed in the circumferential direction at the inner peripheral surface of the holder, and the second light flux controlling member may be fixed using the stepped portion. 
     Further, although a light flux controlling member having a first light flux controlling member formed in a predetermined shape was described in Embodiments 1 to 6, the shape of the first light flux controlling member is not particularly limited. For example, the shape of the first light flux controlling member may be an inverted circular truncated cone shape, similarly to case  14  that is described in PTL 1 (see  FIG. 1 ). 
     The present application claims priority based on Japanese Patent Application No. 2012-026971 filed on Feb. 10, 2012 and Japanese Patent Application No. 2012-190014 filed on Aug. 30, 2012. The entire contents of the specification and drawings of the aforementioned documents are hereby incorporated by reference into the specification of the present application. 
     INDUSTRIAL APPLICABILITY 
     The illumination apparatus according to the present invention can be used as an alternative to an incandescent light bulb, and thus can be widely applied to various illumination devices such as a chandelier or an indirect illumination apparatus. 
     REFERENCE SIGNS LIST 
     
         
           10  Illumination apparatus 
           12  LED 
           14  Case 
           14   a  Case body 
           14   b  Cover section 
           16  Transflective film 
           18  Hook 
           20  Notch portion 
           100  Illumination apparatus 
           110  Base 
           120  Substrate 
           130  Light emitting element 
           140  First light flux controlling member 
           141  Reflection surface 
           142  Flange 
           143  Fitting portion 
           144  Recess 
           150 ,  650  Second light flux controlling member 
           151  Incidence surface 
           152  Total reflection surface 
           153  Emission surface 
           160 ,  260 ,  360 ,  460 ,  560 ,  660  Holder 
           161  End face 
           162  Guide protrusion 
           163  Hook 
           165  Stepped portion 
           166  Ventilation opening 
           170  Light flux controlling member 
           180  Cover 
           461  Ventilation groove 
           651  Incidence region 
           652  Refraction portion 
           653  Fresnel lens portion 
           654  Emission region 
           661  Positioning boss 
           662  Positioning hook 
         CA 1  Central axis of first light flux controlling member 
         CA 2  Central axis of second light flux controlling member 
         LA Optical axis of light emitting element