Patent Publication Number: US-11384920-B2

Title: Illumination device

Description:
TECHNICAL FIELD 
     The present disclosure relates to illumination devices, and particularly relates to illumination devices using laser beams. 
     BACKGROUND ART 
     In the related art, illumination devices using laser beams are known, each of which includes a laser beam source which emits a laser beam, and a wavelength converting component such as a phosphor. In such illumination devices, illumination light having a desired light color is obtained by mixing wavelength-converted light, which is generated by irradiating the wavelength converting component with the laser beam and absorbing part of the laser beam in the wavelength converting component, with part of the laser beam not subjected to such wavelength conversion in the wavelength converting component. 
     For example, in an illumination device including a laser beam source which emits a laser beam of blue light and a phosphor which emits yellow green light, the yellow green light (wavelength-converted light) emitted from the phosphor as a result of absorption of part of blue light emitted from the laser beam source by the phosphor is mixed with the blue light (laser beam) not absorbed by the phosphor, providing white illumination light. 
     As a traditional illumination device using a laser beam, a reflective illumination device is disclosed, which radiates illumination light obtained by causing a laser beam to enter the surface of a wavelength converting component from an oblique direction, and mixing the color of wavelength-converted light generated by the wavelength converting component with the color of the laser beam reflected by the wavelength converting component (for example, PTL 1). 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Unexamined Patent Application Publication No. 2014-135159 
     SUMMARY OF THE INVENTION 
     Technical Problems 
     The laser beam has higher directivity than those of other types of light from LEDs and the like. Such high directivity causes color unevenness of illumination light in the traditional illumination device using the laser beam. In other words, the laser beam reflected by the wavelength converting component has high directivity while the wavelength-converted light generated through wavelength conversion of the laser beam by the wavelength converting component is diffused light and has no directivity. For this reason, the color of the laser beam and the color of the wavelength-converted light are not desirably mixed, causing color unevenness of the irradiation pattern of the mixed light (illumination light), which is the mixed-color light of the laser beam and the wavelength-converted light. 
     To solve this problem, by forming projections and depressions on the surface of the wavelength converting component or mixing a filler having light scattering properties in the wavelength converting component, the laser beam may be diffused (scattered) when the laser beam is reflected by the wavelength converting component, thereby relaxing the directivity of the laser beam. 
     In this method, however, the laser beam which enters the wavelength converting component is back-scattered before absorbed by the wavelength converting component, and is released to the outside of the wavelength converting component. When such a phenomenon becomes remarkable, the absorptivity of the laser beam by the wavelength converting component is inevitably reduced. As a result, for example, when the laser beam is blue light, the blue color component in the mixed light of the laser beam and the wavelength-converted light is hardly reduced, and white light having a low color temperature is hardly obtained as mixed light, reducing the freedom of color design of the mixed light. As above, the method of diffusing the laser beam with the wavelength converting component suffers from a narrow color range of the mixed light of the laser beam and the wavelength-converted light because the diffusibility of the laser beam and the absorptivity of the wavelength converting component are in a trade-off relation. 
     An alternative may be a method of diffusing mixed light after the color of the laser beam is mixed with the color of the wavelength-converted light, rather than the laser beam is diffused by the wavelength converting component. Examples thereof include a method of diffusing the mixed light of the laser beam and the wavelength-converted light by disposing a diffusion transmission component such as a diffusion transmission panel or a diffusion transmission film in an opening portion of the illumination device. 
     In this method, however, the laser beam contained in the mixed light is diffused, and at the same time, part of the wavelength-converted light having no directivity whose further diffusion is unnecessary, is back-scattered. This results in a reduction in light extraction efficiency of the illumination device. 
     The present disclosure has been made to solve such problems, and an object of the present disclosure is to provide an illumination device which produces illumination light having reduced color unevenness without reducing light extraction efficiency and enables color design of the mixed light in a wide color range. 
     Solutions to Problems 
     To solve the above object, one aspect of the illumination device according to the present disclosure includes a housing including an opening portion; a wavelength converting component which is disposed inside the housing and radiates wavelength-converted light after a laser beam enters the wavelength converting component, the wavelength-converted light having a different wavelength from a wavelength of the laser beam; an optical film which covers the opening portion, the optical film having optical properties such that a transmittance for the wavelength-converted light is 80% or more and a transmittance for the laser beam at a peak wavelength is 80% or less of a transmittance for the wavelength-converted light at a peak wavelength; and a light diffusing structure which is disposed on at least part of an inner wall of the housing and diffusely reflects the laser beam reflected by at least the optical film. 
     Advantageous Effects of Invention 
     According to the present disclosure, color unevenness of the illumination light can be reduced without reducing the light extraction efficiency, and color design of the mixed light in a wide color range is enabled. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration of the illumination device according to an embodiment. 
         FIG. 2  is a diagram illustrating the transmission spectrum of the optical film in the illumination device according to the embodiment. 
         FIG. 3  is a partially enlarged cross-sectional view of region III surrounded by the dashed line in  FIG. 1 . 
         FIG. 4  is a partially enlarged cross-sectional view of the configuration of the illumination device according to Modification  1 . 
         FIG. 5  is a partially enlarged cross-sectional view of the configuration of the illumination device according to Modification  2 . 
         FIG. 6  is a diagram illustrating trajectories of light beams of the illumination device according to the embodiment. 
         FIG. 7  is a perspective view of the illumination device according to an example of application. 
         FIG. 8  is a partial cross-sectional view of the illumination device according to the example of application. 
         FIG. 9  is a diagram illustrating the configuration of the illumination device according to Modification  3 . 
         FIG. 10  is a diagram illustrating the configuration of the illumination device according to Modification  4 . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The embodiments according to the present disclosure will now be described. The embodiments described below all illustrate specific examples of the present disclosure. Accordingly, numeric values, shapes, materials, components, arrangements and positions of components, and connection forms thereof illustrated in the following embodiments are exemplary, and should not be construed as limitations to the present disclosure. Accordingly, among the components of the following embodiments, the components not described in an independent claim representing the most superordinate concept of the present disclosure are described as arbitrary components. 
     The drawings are schematic views, and are not always strictly drawn. Accordingly, the scale is not always consistent in the drawings, for example. In the drawings, identical referential numerals are given to substantially identical configurations, and the duplication of the description will be omitted or simplified. 
     Embodiments 
     The configuration of illumination device  1  according to an embodiment will be described with reference to  FIG. 1 .  FIG. 1  is a diagram illustrating a configuration of illumination device  1  according to the embodiment. In  FIG. 1 , the cross-section of illumination device  1  excluding light source  50  is illustrated. 
     As illustrated in  FIG. 1 , illumination device  1  includes housing  10  including opening portion  10   a , wavelength converting component  20  disposed inside housing  10 , optical film  30  disposed in opening portion  10   a  of housing  10 , and light diffusing structure  40  disposed on at least part of an inner wall of housing  10 . Illumination device  1  according to the present embodiment further includes light source  50 . 
     Housing  10  is an accommodator including opening portion  10   a . In the present embodiment, housing  10  accommodates wavelength converting component  20 . Housing  10  has bottom portion  11  and side wall portion  12  erected from bottom portion  11 . Bottom  11  faces opening portion  10   a . As one example, bottom portion  11  has a rectangular shape seen in planar view. In this case, bottom portion  11  is surrounded by four side wall portions  12 . 
     Housing  10  supports wavelength converting component  20  and optical film  30 . Specifically, the wavelength converting component is supported by bottom portion  11  of housing  10 . Optical film  30  is supported by the opening end portion of opening portion  10   a  of housing  10 . Wavelength converting component  20  and optical film  30  are fixed to housing  10  by bonding or using a latch structure or a screw. 
     Housing  10  is made of a metallic material, a resin material, or a ceramic, for example. To dissipate heat generated in wavelength converting component  20 , housing  10  may be made of a material having high thermal conductivity. Accordingly, housing  10  may be made of a metallic material, a resin material high thermal conductivity, or a ceramic. 
     Wavelength converting component  20  is disposed inside housing  10 . Specifically, wavelength converting component  20  is placed on bottom portion  11  of housing  10 . 
     Wavelength converting component  20  radiates wavelength-converted light having a wavelength different from that of a laser beam after the laser beam enters wavelength converting component  20 . In other words, wavelength converting component  20  converts the laser beam entering wavelength converting component  20  into light having a wavelength different from that of the laser beam. Specifically, wavelength converting component  20  outputs light having a wavelength different from that of the laser beam through absorption of the laser beam having a specific wavelength. 
     Wavelength converting component  20  does not completely absorb the laser beam and then convert it to light having a different wavelength. Rather, wavelength converting component  20  absorbs part of the laser beam and outputs light having a different wavelength while reflecting another part of the laser beam without absorption thereof. In other words, part of the laser beam entering wavelength converting component  20  is converted into wavelength-converted light having a wavelength converted by wavelength converting component  20  and is radiated from wavelength converting component  20 , while another part of the laser beam entering wavelength converting component  20  is reflected by wavelength converting component  20  and is radiated from wavelength converting component  20  without wavelength conversion by wavelength converting component  20 . Specifically, wavelength converting component  20  has incident surface  20   a  which the laser beam enters. After incident surface  20   a  is irradiated with the laser beam, incident surface  20   a  absorbs part of the laser beam and outputs light having a different wavelength while reflecting another part of the laser beam. 
     As wavelength converting component  20 , a fluorescent element containing at least one phosphor can be used, for example. In this case, wavelength converting component  20  (fluorescent element) emits fluorescence where the incident light serves as excitation light. As one example, wavelength converting component  20  can be a fluorescent element including fluorescent particles dispersed in a binder made of a resin material such as a silicone resin or an inorganic material such as glass or a ceramic. 
     Wavelength converting component  20  (fluorescent element) is excited through irradiation with the laser beam emitted from light source  50  as excitation light, and radiates fluorescence having a desired color (wavelength). In other words, after the laser beam emitted from light source  50  enters wavelength converting component  20 , wavelength converting component  20  absorbs part of the laser beam, and is excited. Thereby, fluorescence having a predetermined color (wavelength) is radiated from wavelength converting component  20  as wavelength-converted light. For example, wavelength converting component  20  contains a phosphor which absorbs blue light having a wavelength in the range of 420 nm to 480 nm and radiates yellow green light having a wavelength from 510 nm to 590 nm. In other words, wavelength converting component  20  radiates yellow green light as the wavelength-converted light. Such a phosphor to be used can be cerium (Ce)-doped yttrium-aluminum-garnet (YAG) fluorescent particles. Wavelength converting component  20  may contain several fluorescent bodies having different fluorescence peak wavelengths. 
     The wavelength-converted light radiated from wavelength converting component  20  is scattered light and has no directivity. For example, the fluorescence emitted from the phosphor is radiated in all the directions. On the other hand, although the directivity of the laser beam reflected by wavelength converting component  20  can be somewhat weakened by the light diffusibility of wavelength converting component  20 , the light diffusibility of wavelength converting component  20  and the light absorptivity thereof are in a trade-off relation. In the present embodiment, the light absorptivity of wavelength converting component  20  takes precedence over the light diffusibility and a lower light diffusibility is preferred. Accordingly, wavelength converting component  20  had better not to contain a light scattering material which scatters light, such as a filler or nanoparticles, or to diffuse the laser beam somewhat, wavelength converting component  20  may contain a light scattering material. 
     Examples of wavelength converting component  20  containing fluorescent particles include those containing fluorescent particles encapsulated in any encapsulating material. In this case, the light diffusibility and light absorptivity of wavelength converting component  20  can be controlled by the shape, the size, and the refractive index of the fluorescent particles. 
     Although the fluorescent element containing a phosphor has been exemplified as wavelength converting component  20  in the present embodiment, wavelength converting component  20  can be made of any material as long as it converts the wavelength of the incident laser beam to a different wavelength and outputs the resulting light. 
     Optical film  30  covers opening portion  10   a  of housing  10  including wavelength converting component  20  which the laser beam enters. Thereby, the wavelength-converted light obtained by wavelength conversion of the laser beam which enters wavelength converting component  20  and radiated by wavelength converting component  20  and part of the laser beam which enters wavelength converting component  20  reflected by wavelength converting component  20  without wavelength conversion by wavelength converting component  20  enter optical film  30 . Not only these direct light beams but also scattered light beams generated through diffuse reflection of the laser beam and the wavelength-converted light by light diffusing structure  40  enter optical film  30 . 
     Optical film  30  has optical properties to selectively transmit and reflect specific wavelengths of the light beams entering optical film  30 . 
     Specifically, optical film  30  has optical properties such that the transmittance for the wavelength-converted light radiated from wavelength converting component  20  is 80% or more. In other words, optical film  30  has a high transmittance for the wavelength-converted light radiated from wavelength converting component  20 , and transmits most of the wavelength-converted light which is radiated from wavelength converting component  20  and enters optical film  30 . More preferably, the transmittance of optical film  30  for the wavelength-converted light is 90% or more. 
     In the present embodiment, optical film  30  has a high transmittance not only for the wavelength-converted light radiated from wavelength converting component  20 , but also for light other than the wavelength-converted light outside the wavelength bandwidth of the laser beam emitted from light source  50 . For example, the transmittance of optical film  30  outside the wavelength bandwidth of the laser beam entering wavelength converting component  20  is preferably 80% or more. This improves the light extraction efficiency of the illumination light emitted from illumination device  1 . More preferably, the transmittance of optical film  30  outside the wavelength bandwidth of the laser beam entering wavelength converting component  20  is 90% or more. In other words, optical film  30  is preferably transparent for the light having a wavelength outside the wavelength bandwidth of the laser beam entering wavelength converting component  20 . 
     Optical film  30  has optical properties so as to reflect part of the laser beam entering optical film  30  and transmit another part of the laser beam. In other words, optical film  30  has both of an optical property to reflect the laser beam emitted from light source  50  and an optical property to transmit the laser beam emitted from light source  50 . As one example, the transmittance of optical film  30  for the light in the wavelength bandwidth of the laser beam emitted from light source  50  is 40% to 80%. 
     Furthermore, optical film  30  has optical properties such that the transmittance for the laser beam entering wavelength converting component  20  at the peak wavelength is 80% or less of the transmittance for the wavelength-converted light at the peak wavelength, which is radiated from wavelength converting component  20 . 
     In the present embodiment, the laser beam emitted from light source  50  is blue light having a wavelength of 420 nm to 480 nm (peak wavelength: 450 nm), and the wavelength-converted light radiated from wavelength converting component  20  is yellow green light having a wavelength of 510 nm to 590 nm (peak wavelength: 550 nm). Thus, as its optical properties, optical film  30  has the transmission spectrum (transmittance distribution) shown in  FIG. 2  as one example. 
     Specifically, as illustrated in  FIG. 2 , the transmittance of optical film  30  for the wavelength-converted light (yellow green light) in the wavelength bandwidth of 510 nm to 590 nm is 80% or more, and optical film  30  has a high transmittance for the wavelength-converted light. 
     As shown in  FIG. 2 , the transmittance of optical film  30  for the laser beam (blue light) in the wavelength bandwidth of 420 nm to 480 nm is 48% to 75% and the transmittance of optical film  30  for the laser beam at the peak wavelength (450 nm) is 63.1%. In other words, the half or more of the laser beam entering optical film  30  is transmitted and the half or less of the laser beam entering optical film  30  is reflected. Part of the laser beam entering optical film  30  is absorbed by optical film  30 , generating heat. 
     Furthermore, in  FIG. 2 , the transmittance of optical film  30  at the peak wavelength (550 nm) of the wavelength-converted light is 83.1% and that at the peak wavelength (450 nm) of the laser beam is 63.1%. Thus, the proportion of the transmittance (63.1%) at the peak wavelength of the laser beam to the transmittance (83.1%) at the peak wavelength of the wavelength-converted light is 631/83.1=76.0%. 
     Optical film  30  having such optical properties can be made of a dielectric multi-layer film composed of several dielectric films having different refractive indices. The dielectric multi-layer film may be made of organic materials, or may be made of inorganic materials. 
     Optical film  30  has a shape of a film, a sheet, or a plate as one example, and can have any other shape. 
     As illustrated in  FIG. 1 , light diffusing structure  40  is disposed on the inner wall of housing  10 . Specifically, light diffusing structure  40  is disposed on the inner surface of bottom portion  11  and the inner surface of side wall portion  12  of housing  10 . In the present embodiment, light diffusing structure  40  is disposed across the entire inner surface of housing  10 . 
     Light diffusing structure  40  diffusely reflects the laser beam reflected by at least optical film  30 . Specifically, the laser beam reflected by optical film  30  is diffused through scattering reflection by light diffusing structure  40 . Although light diffusing structure  40  is disposed to diffuse the laser beam having high directivity reflected by mainly optical film  30 , it may diffusely reflect not only the light in the wavelength bandwidth of the laser beam but also the light in the entire wavelength band in the visible light region. In this case, while the reflectance of light diffusing structure  40  in the entire wavelength band in the visible light region may be 100%, the reflectance does not always need to be 100%, and may be at least 90% or more. Of the light beam which enters light diffusing structure  40 , part of the light beam not reflected by light diffusing structure  40  is absorbed in light diffusing structure  40  or housing  10  to generate heat, and the heat is conducted. Light diffusing structure  40  may diffusely reflect only the laser beam reflected by optical film  30 . 
     Light diffusing structure  40  to be used can be a light diffusion film including aggregates of a fine light scattering material. Here, with reference to  FIG. 3 , a detailed configuration of light diffusing structure  40  will be described.  FIG. 3  is an enlarged cross-sectional view of region III surrounded by the dashed line in  FIG. 1 . 
     As illustrated in  FIG. 3 , light diffusing structure  40  is a light diffusion film including light scattering material  41  dispersed in resin  42 , and is disposed on the inner wall of housing  10 . Such a light diffusion film to be used can be a resin film including light diffusing nanoparticles as light scattering material  41  dispersed in a binder resin such as a polycarbonate or acrylic resin as resin  42 . Specifically, a white resin film including white nanoparticles as light scattering material  41  (light diffusing nanoparticles) can be used. Such a light diffusing structure  40  can be disposed as a light diffusion coating. For example, the light diffusion coating can be disposed on the inner wall surface of housing  10  by applying a dispersion of an infinite number of light scattering material  41  dispersed in a binder resin solution onto the inner wall surface of housing  10 , and curing the coating. 
     As light diffusing structure  40 A illustrated in  FIG. 4 , a transparent inorganic filler may be used as light scattering material  41 A, and a light diffusion film including a set of aggregates of the transparent inorganic filler may be used. In this case, as illustrated in  FIG. 4 , part of light scattering material  41 A may be exposed from resin  42 , and light scattering material  41 A may not be exposed. In  FIG. 3 , light scattering material  41  may be exposed from resin  42 . 
     Although light diffusing structures  40  and  40 A each are separately disposed from housing  10  in the present embodiment, light diffusing structures  40  and  40 A each may be integrally formed with housing  10 . In this case, housing  10  is formed using the same material as those for light diffusing structures  40  and  40 A. 
     As illustrated in  FIG. 5 , light diffusing structure  40 B may be a convexo-concave structure disposed on the inner wall of housing  10 , rather than aggregates of light scattering material  40  or  40 A. In other words, the laser beam reflected by optical film  30  may be diffusely reflected according to the shape of the convexo-concave structure. The convex-concave structure is a repetition structure of a plurality of fine projections and/or a plurality of fine depressions. In this case, the convexo-concave structure preferably contains a convexoconcave surface having a surface roughness Ra (arithmetic average roughness) of 10 μm or more. Thus, the laser beam reflected by optical film  30  can be diffusely reflected with high efficiency. The convexo-concave structure which can diffusely reflect light may be a convexo-concave film having a convexo-concave surface structure which is formed separately from housing  10  as illustrated in  FIG. 5 , or may be part of housing  10 . In other words, a convexo-concave structure may be formed on the surface of housing  10 . 
     Light diffusing structures  40  and  40 A may be formed across the entire surface of housing  10 , or may be formed on part thereof. Light diffusing structures  40  and  40 A may partially include a different structure. Desired properties of illumination device  1  can be controlled according to the proportion of the area where light diffusing structure  40  or  40 A is formed or the proportion of a different structure included in light diffusing structure  40  or  40 A. For example, the light extraction efficiency and color temperature of the illumination light emitted from illumination device  1  can be controlled according to the proportion of the formation area. 
     Light diffusing structure  40  can control the reflectance of light according to its thickness and scattering intensity. The light extraction efficiency and color temperature of the illumination light emitted from illumination device  1  can be controlled by controlling the reflectance of light diffusing structure  40 . 
     Light source  50  is a laser beam source which emits a laser beam. For example, light source  50  includes a semiconductor laser which emits a laser beam. In the present embodiment, the laser beam emitted from light source  50  is blue light. Specifically, the laser beam emitted from light source  50  is light having a peak wavelength of 450 nm and having a wavelength bandwidth of 420 nm to 480 nm, for example. 
     Light source  50  is disposed outside housing  10 . Light source  50  is disposed such that the laser beam enters wavelength converting component  20 . In the present embodiment, light source  50  is disposed such that the laser beam emitted from light source  50  enters wavelength converting component  20  with an inclination to the surface thereof. 
     Specifically, through hole  10   b  is disposed on side wall portion  12  of housing  10 , and the laser beam is emitted from light source  50 , and enters wavelength converting component  20  through hole  10   b.    
     To control the orientation of the laser beam emitted from light source  50  or perform beam shaping of the laser beam, optical components such as a collimator lens and a reflective component may be disposed between light source  50  and wavelength converting component  20 . Light source  50  may be disposed inside housing  10  rather than outside housing  10 . In this case, through hole  10   b  of housing  10  is unnecessary. 
     Next, the optical action of illumination device  1  according to the present embodiment will be described with reference to  FIG. 6 .  FIG. 6  is a diagram illustrating trajectories of light beams in illumination device  1  according to the embodiment. 
     As illustrated in  FIG. 6 , after laser beam LB 1  is emitted from light source  50 , laser beam LB 1  (the solid bold line in  FIG. 6 ) enters the surface of wavelength converting component  20  from an oblique direction. When laser beam LB 1  enters wavelength converting component  20 , part of laser beam LB 1  is absorbed in wavelength converting component  20  to be subjected to wavelength conversion. Wavelength-converted light LC 2  (the dashed line in  FIG. 6 ) having a wavelength different from that of laser beam LB 1  is radiated from wavelength converting component  20 , and another part of laser beam LB 1  is reflected by wavelength converting component  20  without being absorbed in wavelength converting component  20  to be converted into laser beam LB 2  (the solid semi-bold line in  FIG. 6 ). 
     As a result, wavelength-converted light LC 2  and the reflected laser beam LB 2  are radiated from wavelength converting component  20 . At this time, wavelength-converted light LC 2  is radiated in all the directions. Laser beam LB 2  reflected by wavelength converting component  20  is radiated while maintaining directivity. 
     Wavelength-converted light LC 2  and laser beam LB 2  radiated from wavelength converting component  20  travel to optical film  30 , and enter optical film  30 . 
     At this time, optical film  30  has a transmittance of 80% or more for the wavelength-converted light generated in wavelength converting component  20 . For this reason, most of wavelength-converted light LC 2  which enters optical film  30  transmits through optical film  30 , and is radiated to the outside of housing  10 . 
     Optical film  30  has both an optical property to reflect the laser beam emitted from light source  50  and an optical property to transmit the laser beam emitted from light source  50 . For this reason, part of laser beam LB 2  which enters optical film  30  travels straight and transmits through optical film  30 , and is radiated to the outside of housing  10  as laser beam LB 3  (the solid thin line in an upper portion of  FIG. 6 ), and another part of laser beam LB 2  is reflected by optical film  30 , and travels toward the lower portion of housing  10  as laser beam LB 4  (the solid thin line in a lower portion of  FIG. 6 ). In other words, laser beam LB 2  which enters optical film  30  is separated into laser beam LB 3  (light traveling straight) and laser beam LB 4  (reflected light) by optical film  30 . 
     Laser beam LB 4 , which is reflected by optical film  30  and travels to the lower portion of housing  10 , enters light diffusing structure  40  disposed on the inner wall of housing  10 . Light diffusing structure  40  has a function to diffusely reflect at least the laser beam emitted from light source  50 . Thus, laser beam LB 4  which enters light diffusing structure  40  is diffusely reflected by light diffusing structure  40 , and is radiated from light diffusing structure  40  as diffused light LD 5  (the dashed-and-dotted line in  FIG. 6 ) in an isotropic-scattering manner. 
     Diffused light LD 5  diffusely reflected by light diffusing structure  40  travels toward the upper portion of housing  10  inside housing  10 . In other words, diffused light LD 5  travels toward optical film  30 , and enters optical film  30 . 
     Here, diffused light LD 5  has the same wavelength as that of the laser beam emitted from light source  50 . As described above, optical film  30  has both an optical property to reflect the laser beam emitted from light source  50  and an optical property to transmit the laser beam emitted from light source  50 . Accordingly, part of diffused light LD 5  which enters optical film  30  travels straight and transmits through optical film  30 , and is radiated to the outside of housing  10 , while another part of diffused light LD 5  which enters optical film  30  is reflected by optical film  30  to return to the inside of housing  10 , and travels toward the lower portion of housing  10 . 
     The diffused light of diffused light LD 5 , which is reflected by optical film  30  and travels inside housing  10  toward the lower portion thereof, is again diffusely reflected by light diffusing structure  40  and reenters optical film  30 . In other words, diffused light LD 5  is repeatedly subjected to reflection by and transmission through optical film  30  and diffuse reflection by light diffusing structure  40 . 
     As a result, laser beam LB 4 , which is reflected by wavelength converting component  20  and then by optical film  30 , is finally converted to diffused light by light diffusing structure  40 . In other words, laser beam LB 4  is completely converted to diffused light, transmits through optical film  30 , and is radiated to the outside of housing  10 . For this reason, irrespective of the absorptivity of wavelength converting component  20 , light diffusibility for laser beam LB 1  emitted from light source  50  can be ensured. 
     At this time, as a result of laser beam LB 4  being repeatedly subjected to reflection by and transmission through optical film  30  and diffuse reflection by light diffusing structure  40 , laser beam LB 3  can have a sufficiently small light quantity to the light quantity extracted as the diffused light to the outside of housing  10 . Thus, color unevenness of the irradiation pattern of the mixed light can be reduced. 
     Thus, in illumination device  1  according to the present embodiment, the laser beam having high directivity can have diffusibility because of optical film  30  and light diffusing structure  40  even if the light diffusibility is not imparted to wavelength converting component  20 . The wavelength-converted light generated by wavelength converting component  20  using the laser beam as excitation light has diffusibility. In other words, the laser beam radiated from opening portion  10   a  of housing  10  and the wavelength-converted light both are diffused light, and are turned into mixed light having a desired mixed color (mixed-color light). Accordingly, color unevenness generated in the irradiation pattern of the illumination light emitted from illumination device  1  can be reduced. 
     Furthermore, in illumination device  1  according to the present embodiment, formation of projections and depressions on the surface of wavelength converting component  20  or mixing of a filler having light scattering properties in wavelength converting component  20  is unnecessary for the purpose of enhancing the light diffusibility of wavelength converting component  20 , and therefore the absorptivity of the laser beam in wavelength converting component  20  can be maintained at high level. Thus, a narrow color range of the mixed-color light as the mixed light of the laser beam and the wavelength-converted light can be avoided, increasing the freedom of color design of the mixed light. 
     In addition, because illumination device  1  according to the present embodiment has a configuration in which the section having a function to diffuse the laser beam is separated from the section having a function to absorb the laser beam and perform wavelength conversion on the laser beam, only mainly the laser beam can be selectively diffused between the laser beam and the wavelength-converted light. Accordingly, a reduction in light extraction efficiency due to back scattering of the wavelength-converted light is avoided in illumination device  1 , unlike the traditional illumination device including the diffusion transmission component where such back scattering is caused by diffusion of not only the laser beam but also the wavelength-converted light whose further diffusion is unnecessary. 
     As described above, in illumination device  1  according to the present embodiment, color unevenness of the illumination light can be reduced without reducing the light extraction efficiency, and color design of the mixed light in a wide color range is enabled. 
     Here, an example of application of illumination device  1  according to the embodiment will be described with reference to  FIGS. 7 and 8 .  FIG. 7  is a perspective view of illumination device  1 A according to an example of application.  FIG. 8  is a partial cross-sectional view of illumination device  1 A.  FIG. 7  illustrates a state where optical film  30  is removed. 
     As illustrated in  FIGS. 7 and 8 , illumination device  1 A according to the present modification further includes base  60 , lens  70 , and reflective component  80 . 
     Base  60  is the main body including housing  10  and light source  50 . Housing  10  is placed on the top surface of base  60 . Light source  50  is accommodated inside base  60 . 
     Base  60  also functions as a heat sink to dissipate heat generated in wavelength converting component  20  through light source  50  and housing  10 . Accordingly, base  60  is preferably made of a material having high thermal conductivity such as a metallic material (such as aluminum) or a highly heat conductive resin. 
     Lens  70  is a collimator lens. The laser beam radially emitted from light source  50  is converted to parallel light having a predetermined beam diameter by lens  70 . 
     Reflective component  80  reflects the laser beam emitted from light source  50 , and emits the reflected laser beam to wavelength converting component  20  disposed inside housing  10 . Specifically, reflective component  80  reflects the laser beam collimated by lens  70 . Reflective component  80  is attached to part of base  60 . 
     Although light source  50  is held by base  60  in the present modification, light source  50  may be disposed outside base  60  and the laser beam may be transmitted from light source  50  through an optical fiber to cause the laser beam to enter reflective component  80 . In this case, an end portion of the optical fiber is disposed at the position of light source  50  in  FIG. 8 . 
     Modifications 
     The illumination device according to the present disclosure has been described by way of the embodiments, but the embodiments above should not be construed as limitations to the present disclosure. 
     For example, in the embodiments above, illumination device  1  may be a lighting apparatus as a product, or may be used as a part (light source module) incorporated in the lighting apparatus. 
     Although the laser beam emitted from light source  50  is caused to enter wavelength converting component  20  in the embodiments above, irradiation of wavelength converting component  20  with the laser beam can be performed by any other method. For example, as illustrated in  FIG. 9 , the laser beam emitted from light source  50  may be transmitted through optical fiber  90 , and the laser beam emitted from one end portion of optical fiber  90  may be emitted to wavelength converting component  20 . In this case, in  FIG. 9 , the light emitting portion (one end portion of optical fiber  90 ) is disposed inside housing  10 . The light emitting portion may be disposed outside housing  10 . 
     Although light diffusing structure  40  including aggregates of a light scattering material ( FIG. 3 ) or light diffusing structure  40 A having a convexo-concave structure on its surface ( FIG. 4 ) is disposed on the inner wall of housing  10  as the structure to diffuse light in the embodiments above, any other structure to diffuse light can be used. For example, as illustrated in  FIG. 10 , light diffusing structure  40 C may have a concave surface defined by a curved surface of the inner wall (inner wall surface) of housing  10 . In this case, light diffusing structure  40 C may have a smooth concave surface defined by a curved inner wall surface of housing  10 , or may include the aggregates of a light scattering material illustrated in  FIGS. 3 and 4  or the convexo-concave structure illustrated in  FIG. 5  on the surface of the concave surface. 
     Although the illumination device according to the embodiments above is of a reflective type which reflects the laser beam on wavelength converting component  20 , the present disclosure can be used in a transmissive illumination device which transmits the laser beam through wavelength converting component  20 . 
     Besides, the present disclosure also covers embodiments obtained from a variety of modifications of the embodiments and modifications above conceived by persons skilled in the art and those implemented with any combinations of the components and the functions in the embodiments and modifications without departing the gist of the present disclosure.